WEBVTT 1 00:00:00.000 --> 00:00:01.720 STFC-RAL-CR03-RAL-R61-2.01: They can see. 2 00:00:02.320 --> 00:00:18.400 STFC-RAL-CR03-RAL-R61-2.01: Okay, sorry about the delay. Okay. So, to introduce Rob, you joined Ashley's group last October, right? Yeah. And before that, you did a PhD from all of her with Jocelyn? Yeah. And prior to that, you had 3 degrees. 3 00:00:18.460 --> 00:00:28.140 STFC-RAL-CR03-RAL-R61-2.01: So, yeah, bachelor's degree in physics and master's degree in physics from Sheffield, and also the PCC degree in secondary education from Sheffield, Halloween University. 4 00:00:28.140 --> 00:00:40.390 STFC-RAL-CR03-RAL-R61-2.01: So, I believe you are going to talk about your PhD stuff here, so, yeah, all of you, by the way. Okay, so, hi everyone, yeah, thanks for that introduction. So, I'm Rob. I'm going to be talking to you about Quest DMC experiment. 5 00:00:40.390 --> 00:00:48.459 STFC-RAL-CR03-RAL-R61-2.01: Which stands for Quantum Enhanced Superfluid Technologies for Dark Matter and Cosmology. And if there are any hip-hop heads in the audience, which I'm sure there are. 6 00:00:48.680 --> 00:00:58.540 STFC-RAL-CR03-RAL-R61-2.01: They'll probably realize that we stole the name and the logo from Run DMC, so maybe one day there will be a lawsuit in the mail, but hopefully not. 7 00:00:58.650 --> 00:01:17.189 STFC-RAL-CR03-RAL-R61-2.01: So the general outline of the talk is going to be starting from a very broad overview of theoretical and experimental landscape of direct dark matter detection, where Quest DMC fits into this landscape, why does the experiment exist, an overview of the experiment, just the composite parts that make it up, and then 8 00:01:17.300 --> 00:01:27.019 STFC-RAL-CR03-RAL-R61-2.01: The operation of the experiments and data, how we actually, how we actually run this thing, and then the physics potential in the direct biomatter detection space as well. 9 00:01:28.080 --> 00:01:37.580 STFC-RAL-CR03-RAL-R61-2.01: So, starting with the sort of landscape. So, I made this slide very quickly, I thought, in my head, okay, what are some of the big questions in terms of today? 10 00:01:37.750 --> 00:01:56.540 STFC-RAL-CR03-RAL-R61-2.01: Unification of the forces, why is there so much more matter than antimatter in the universe, what is the nature of dark energy, and then the bottom one there, which I care about the most, what is dark matter? So we know it exists, I'm sure a lot of you here have heard about it, some of you might even work on it, but some of you might not. 11 00:01:57.020 --> 00:02:02.190 STFC-RAL-CR03-RAL-R61-2.01: But one of the fundamental questions you have is, we know it's there, what is it? 12 00:02:03.150 --> 00:02:15.650 STFC-RAL-CR03-RAL-R61-2.01: So, I won't spend loads of time on this, but there's lots of evidence for dark matter, going from galactic scales, of the rotation of stars around galaxies, things going faster than they should do. 13 00:02:15.660 --> 00:02:27.229 STFC-RAL-CR03-RAL-R61-2.01: The, colliding galaxy clusters, where you find that most of the mass of these galaxy clusters actually goes through, completely unperturbed, where the actual stellar gases interact with each other. 14 00:02:27.230 --> 00:02:49.439 STFC-RAL-CR03-RAL-R61-2.01: The large-scale structure of the universe, so we kind of need dark matter to explain why the universe, formed the way it did, and the cosmic wave formed the way it did, and how large scales and small scales formed at certain times in the universe's history. And then also the anisotropies of the cosmic microwave background palette structure. You essentially need 15 00:02:49.440 --> 00:02:59.110 STFC-RAL-CR03-RAL-R61-2.01: A good amount of matter that isn't interacting with radiation to then actually explain why we get these rare fractions and compressions in the early universe. 16 00:03:00.470 --> 00:03:02.600 STFC-RAL-CR03-RAL-R61-2.01: So what makes a good candidate for dark matter? 17 00:03:02.890 --> 00:03:14.709 STFC-RAL-CR03-RAL-R61-2.01: Well, it needs to be stable, or at least on a scale similar to the lifetimes of the universe, so it's not decaying into any standard model particles at a very fast rate. 18 00:03:14.860 --> 00:03:21.379 STFC-RAL-CR03-RAL-R61-2.01: Initially electrically neutral, so… or incredibly weakly charged, so it's not really interacting with light much. 19 00:03:21.660 --> 00:03:22.969 STFC-RAL-CR03-RAL-R61-2.01: That's why I stopped. 20 00:03:23.150 --> 00:03:24.650 STFC-RAL-CR03-RAL-R61-2.01: has had mass. 21 00:03:24.900 --> 00:03:27.649 STFC-RAL-CR03-RAL-R61-2.01: To explain all the gravitational effects that we see. 22 00:03:28.290 --> 00:03:34.639 STFC-RAL-CR03-RAL-R61-2.01: non-baryonic. It has to be cold, so non-relativistic, so that's essentially, 23 00:03:35.620 --> 00:03:42.240 STFC-RAL-CR03-RAL-R61-2.01: To explain the large-scale structure, this has to be moving at certain speeds that means it can plump together. 24 00:03:44.910 --> 00:03:49.920 STFC-RAL-CR03-RAL-R61-2.01: So, I know this is a very wisdom tour of dark matter, but this is… 25 00:03:50.910 --> 00:03:57.940 STFC-RAL-CR03-RAL-R61-2.01: Showing about 40 orders of magnitude of theories of what a dark matter particle could be. 26 00:03:57.940 --> 00:04:14.680 STFC-RAL-CR03-RAL-R61-2.01: So it's quite a broad spectrum to be able to look at and say, okay, we're going to create an experiment and look for particles in this mass range, because realistically, you can't create an experiment that looks over 40 orders of magnitude in mass and energy scales. So. 27 00:04:14.680 --> 00:04:16.569 STFC-RAL-CR03-RAL-R61-2.01: There's a few… 28 00:04:16.680 --> 00:04:27.069 STFC-RAL-CR03-RAL-R61-2.01: popular theories and theoretical models of what dark matter could be, going from, you know, wave-like dark matter, so axions, axion-like particles, where… 29 00:04:27.270 --> 00:04:46.770 STFC-RAL-CR03-RAL-R61-2.01: Yeah, these are light enough to behave more like a wave, so you have experiments that then look for conversion into photons, and resonant cavities, magnetic cavities. And then on this side, when you're getting to similar mass scales to nuclei, or electrons, and then nuclei. 30 00:04:46.770 --> 00:05:03.440 STFC-RAL-CR03-RAL-R61-2.01: then you end up having models that you can look for from interaction with nuclei themselves. So, elastic recoils, where you have a dark matter particle come in, bounce off a nucleus, and then detect the energy that that dark matter particle has given that nucleus. 31 00:05:03.550 --> 00:05:19.850 STFC-RAL-CR03-RAL-R61-2.01: So that's essentially what I'm going to be focusing on today, so his interactions with nuclei, and this is the sort of region that Quest wants to sit in. So, this space where we're looking for models of dark matter that have sort of MVP to GEV scale mass. 32 00:05:23.170 --> 00:05:27.110 STFC-RAL-CR03-RAL-R61-2.01: So this is quite a nice cartoon, where 33 00:05:27.600 --> 00:05:36.749 STFC-RAL-CR03-RAL-R61-2.01: you can see the different ways in which you might produce or detect dark matter on Earth or, or in fact in space. So. 34 00:05:36.870 --> 00:05:41.579 STFC-RAL-CR03-RAL-R61-2.01: That starts at the top. So if you imagine this is a Feynman diagram. So you have… 35 00:05:41.720 --> 00:05:53.019 STFC-RAL-CR03-RAL-R61-2.01: the biomass particles over here, you have the standard model particles over here. If you start with an initial state, with two standard model particles, let's say, like in a collider. 36 00:05:53.190 --> 00:06:06.539 STFC-RAL-CR03-RAL-R61-2.01: You zoom these around, you bash them into each other, you might then create a final state, where you have the dark matter particles flying off, and what you do is you look for sort of the missing mass, or missing energy. 37 00:06:07.010 --> 00:06:08.430 STFC-RAL-CR03-RAL-R61-2.01: So that's production. 38 00:06:08.900 --> 00:06:15.020 STFC-RAL-CR03-RAL-R61-2.01: You can also have, maybe your initial state being dark matter particles interacting with each other. 39 00:06:15.370 --> 00:06:19.980 STFC-RAL-CR03-RAL-R61-2.01: Producing a final state, Which are your standard microparticles. 40 00:06:20.290 --> 00:06:40.180 STFC-RAL-CR03-RAL-R61-2.01: And you would call that indirect detection, so let's say, you see a burst of gamma rays coming from an astrophysical object, and you say it has a certain energy, and you say, okay, that looks like it could be a very energetic system where you have dark matter being able to interact with each other, and then produce. 41 00:06:40.460 --> 00:06:47.460 STFC-RAL-CR03-RAL-R61-2.01: some, some, energetic semi-modern particle, which then, eventually, we see on a… 42 00:06:48.580 --> 00:06:55.169 STFC-RAL-CR03-RAL-R61-2.01: But then, what I focus on is the direct protection aspect. So, you have a dominant particle come in. 43 00:06:55.370 --> 00:06:57.660 STFC-RAL-CR03-RAL-R61-2.01: interact with the Seminar Particle. 44 00:06:58.080 --> 00:07:00.219 STFC-RAL-CR03-RAL-R61-2.01: That domino parcel flies off. 45 00:07:00.490 --> 00:07:14.449 STFC-RAL-CR03-RAL-R61-2.01: And what we care about is the final state of that standard model particle, where it's been given some energy, it then has to DXI, and you have to detect that energy that the standard model particle has recoiled with. 46 00:07:14.820 --> 00:07:16.389 STFC-RAL-CR03-RAL-R61-2.01: To try and infer. 47 00:07:16.550 --> 00:07:18.879 STFC-RAL-CR03-RAL-R61-2.01: Like, you have a DMAC spot to come in. 48 00:07:19.020 --> 00:07:20.319 STFC-RAL-CR03-RAL-R61-2.01: That's it. 49 00:07:22.970 --> 00:07:23.820 STFC-RAL-CR03-RAL-R61-2.01: So… 50 00:07:24.430 --> 00:07:38.890 STFC-RAL-CR03-RAL-R61-2.01: In our field, we kind of parameterize the interactions with, between dim matter and new films using something called non-relativistic vector field theory. So, I'm not going to go too far into this, because I'm also not a theorist. 51 00:07:38.910 --> 00:07:51.169 STFC-RAL-CR03-RAL-R61-2.01: But you essentially have, your interaction split into a bunch of different operators, we call them, where within these operators, you have different couplings, so… 52 00:07:51.730 --> 00:08:00.650 STFC-RAL-CR03-RAL-R61-2.01: The benchmark operators that we tend to use in our fields are steady independent, where you have this coherent scattering. 53 00:08:00.780 --> 00:08:03.720 STFC-RAL-CR03-RAL-R61-2.01: With all of the nucleons within a nucleus. 54 00:08:04.020 --> 00:08:11.250 STFC-RAL-CR03-RAL-R61-2.01: And then, this actually scales with the atomic mass, Of whatever your nucleus is. 55 00:08:12.060 --> 00:08:18.430 STFC-RAL-CR03-RAL-R61-2.01: But then you can also have a skin-dependent coupling. So, you have the interaction coupling to the nucleosphere itself. 56 00:08:18.640 --> 00:08:20.680 STFC-RAL-CR03-RAL-R61-2.01: But to actually be sensitive to this. 57 00:08:20.790 --> 00:08:30.959 STFC-RAL-CR03-RAL-R61-2.01: you need to have an unpaired nucleon within your target nucleus. So, let's say you have two protons and one neutron in your nucleus, for example. 58 00:08:31.180 --> 00:08:33.079 STFC-RAL-CR03-RAL-R61-2.01: Which I'll come onto in a second. 59 00:08:33.710 --> 00:08:38.500 STFC-RAL-CR03-RAL-R61-2.01: But then this doesn't scale with your atomic mass number. It can scale with how many 60 00:08:38.940 --> 00:08:50.480 STFC-RAL-CR03-RAL-R61-2.01: Target atoms you have, obviously your sensitivity, but the actual cross-section, the actual interaction strength is not going to scale with how big a root business is, which is useful for us. 61 00:08:52.790 --> 00:09:00.620 STFC-RAL-CR03-RAL-R61-2.01: And this is the, again, very broad direct detection landscape. So, just to explain this box quickly. 62 00:09:01.020 --> 00:09:05.430 STFC-RAL-CR03-RAL-R61-2.01: These are what we call exclusion points, where we have our dark matter maps. 63 00:09:05.600 --> 00:09:19.990 STFC-RAL-CR03-RAL-R61-2.01: that we're looking for on the x-axis, and then you have the cross-section, or interaction strength on the y-axis. So the further down you go here, the rarer your interaction, the weaker the coupling between your dark matter and your nucleus. 64 00:09:20.260 --> 00:09:32.610 STFC-RAL-CR03-RAL-R61-2.01: And then, the lower down here, obviously, the smaller that mathematics you're actually testing for. So we have this spin-independent, like I mentioned, sensitivities here, and spin-dependent exclusions here. 65 00:09:32.860 --> 00:09:36.210 STFC-RAL-CR03-RAL-R61-2.01: Where any, any of the shaded region here. 66 00:09:36.340 --> 00:09:39.999 STFC-RAL-CR03-RAL-R61-2.01: We say, that's excluded. So we statistically said. 67 00:09:40.650 --> 00:09:45.679 STFC-RAL-CR03-RAL-R61-2.01: The matter can't live in this parameter space, and each of these lines is a different experiment. 68 00:09:45.790 --> 00:09:50.459 STFC-RAL-CR03-RAL-R61-2.01: There's actually published a limit from running and taking data. 69 00:09:51.040 --> 00:10:09.840 STFC-RAL-CR03-RAL-R61-2.01: then any line that has, a dashed line is, is an expected sensitivity from a planned experiment in the future. So, you can see down in this, like, larger mass region, sort of below the 10 GV, dominated by experiments that use, 70 00:10:09.980 --> 00:10:20.300 STFC-RAL-CR03-RAL-R61-2.01: nodal makers, so things like Xenon, so like Xenon Enton, Panda X, LZ, or things like, Argon, so Bonsai 20K, the 3600, 71 00:10:20.790 --> 00:10:25.700 STFC-RAL-CR03-RAL-R61-2.01: But then… You notice, as you start moving down to lowering lower masses. 72 00:10:26.260 --> 00:10:33.990 STFC-RAL-CR03-RAL-R61-2.01: the experiments that dominate down here aren't the experiments that dominate up here. That's because as you move down to lower masses. 73 00:10:34.590 --> 00:10:37.909 STFC-RAL-CR03-RAL-R61-2.01: You essentially need to be able to set lower end fees. 74 00:10:38.240 --> 00:10:42.800 STFC-RAL-CR03-RAL-R61-2.01: Because you're going to be giving your nuclei smaller amounts of energy. 75 00:10:43.100 --> 00:10:47.950 STFC-RAL-CR03-RAL-R61-2.01: For a given dark matter mass. So, the kinematic matching means 76 00:10:48.340 --> 00:11:03.970 STFC-RAL-CR03-RAL-R61-2.01: you're essentially going to probably want lighter particles, in general, as your target. Also, smaller and smaller energies need to be detectable. So here you have solid-state detectors like CDMS, things like germanium, silicon, where you have low bandgaps. 77 00:11:05.380 --> 00:11:07.220 STFC-RAL-CR03-RAL-R61-2.01: And you notice. 78 00:11:07.420 --> 00:11:18.799 STFC-RAL-CR03-RAL-R61-2.01: There's all this unexplored region over here, because it's actually quite hard to create a detector where you can detect incredibly small amounts of energy 79 00:11:18.940 --> 00:11:20.390 STFC-RAL-CR03-RAL-R61-2.01: Very, very well. 80 00:11:20.520 --> 00:11:26.709 STFC-RAL-CR03-RAL-R61-2.01: And actually be able to distinguish that from background noise in your experiment. 81 00:11:27.080 --> 00:11:30.719 STFC-RAL-CR03-RAL-R61-2.01: So this is the sort of region that we want to live in. 82 00:11:31.540 --> 00:11:37.529 STFC-RAL-CR03-RAL-R61-2.01: And this is where Quest DNC fits in. So… One, we're gonna use EM3. 83 00:11:37.660 --> 00:11:43.280 STFC-RAL-CR03-RAL-R61-2.01: Where it has an unpaired electron, which means we're going to be sensitive to spin-dependent interactions. 84 00:11:43.570 --> 00:11:49.090 STFC-RAL-CR03-RAL-R61-2.01: And then two, healing 3 becomes something called a superfluid. 85 00:11:49.650 --> 00:11:57.519 STFC-RAL-CR03-RAL-R61-2.01: Which means that you actually have this massive quantum system, and the amount… the quanta that you produce are tiny, tiny, tiny energy. 86 00:11:57.690 --> 00:12:08.880 STFC-RAL-CR03-RAL-R61-2.01: So if you look at this plot, we have the recoil energy, so the energy being given to your nucleus from your dark matter recoil against the mass of your dark matter particle. 87 00:12:09.020 --> 00:12:16.780 STFC-RAL-CR03-RAL-R61-2.01: And if we look at this elastic nuclear recall band, so we're saying we're looking for, you know, a nuclear recall, that's our signal. 88 00:12:16.920 --> 00:12:23.999 STFC-RAL-CR03-RAL-R61-2.01: Then, once you get down to maybe 100 MeV, you're talking about maybe breathable energies on the EV scale. 89 00:12:24.470 --> 00:12:33.319 STFC-RAL-CR03-RAL-R61-2.01: So… For the noble liquids like xenon, argon, you're kind of limited by The ionization energy. 90 00:12:33.450 --> 00:12:52.940 STFC-RAL-CR03-RAL-R61-2.01: Once you go down, you can start looking at these semiconductor gap materials, about maybe one electron volt. Then you can go even further down, you can look at, interesting systems like, superconductors, where you have maybe, like, MEV, scale excitations you can detect. 91 00:12:53.360 --> 00:12:56.269 STFC-RAL-CR03-RAL-R61-2.01: But then eventually, if you want to go down to, like, micro. 92 00:12:56.500 --> 00:13:02.559 STFC-RAL-CR03-RAL-R61-2.01: effects on both scale reborn energies. You've got to go into this weird world of superfoods. 93 00:13:10.950 --> 00:13:14.510 STFC-RAL-CR03-RAL-R61-2.01: So the Quest AMC collaboration is kind of an interesting one. 94 00:13:14.700 --> 00:13:33.779 STFC-RAL-CR03-RAL-R61-2.01: It brings together both, sort of, particle astrophysicists, dark matter protection physicists, and then ultra-low temperature, superfluid helium-3 condensed matter physicists, to try and solve a couple of really interesting questions in the field of physics, where… 95 00:13:33.960 --> 00:13:47.010 STFC-RAL-CR03-RAL-R61-2.01: The one, obviously, I'm focusing on is its direct detection of, sort of, GEV dark matter. But then, there's actually another work package, WorkPatcher 2, we call it, where they're looking at phase transitions in superfluid helium. 96 00:13:47.040 --> 00:13:58.880 STFC-RAL-CR03-RAL-R61-2.01: As a, an analog for phase transitions in the early universe, which could also help explain, gravitational wave, production in the early universe as well. 97 00:14:01.890 --> 00:14:06.729 STFC-RAL-CR03-RAL-R61-2.01: So there's a nice picture of the collaboration in Liverpool. You'll also notice, maybe. 98 00:14:06.830 --> 00:14:14.770 STFC-RAL-CR03-RAL-R61-2.01: I'm not in this. Well, you get a good picture of me here, that's fine. But I was curiously, curiously 99 00:14:15.050 --> 00:14:25.860 STFC-RAL-CR03-RAL-R61-2.01: finishing my thesis when this collaboration meeting was going on, so I didn't think it was a good idea to, do anything other than sit in the office for 15 hours or whatever. 100 00:14:25.980 --> 00:14:32.199 STFC-RAL-CR03-RAL-R61-2.01: But, so yeah, so let's come on to the Quest EMC Experiment. I'll go over, kind of, the… 101 00:14:34.190 --> 00:14:46.489 STFC-RAL-CR03-RAL-R61-2.01: the base parts that make up the experiment, the kind of overall, interesting ways in which we're trying to reach that sensitivity in that parameter space that I mentioned before. 102 00:14:46.750 --> 00:14:51.169 STFC-RAL-CR03-RAL-R61-2.01: And then I'll come on to, afterwards, the actual operation and what kind of data to take. 103 00:14:52.990 --> 00:14:54.470 STFC-RAL-CR03-RAL-R61-2.01: So the goal of the experiment… 104 00:14:54.950 --> 00:14:57.790 STFC-RAL-CR03-RAL-R61-2.01: We want to do a low threshold done matter search. 105 00:14:58.670 --> 00:15:07.089 STFC-RAL-CR03-RAL-R61-2.01: How do we achieve this? So, I've already gone over the superfood aspect, but we want to get down to ultra-low temperatures, so about 100 microcars. 106 00:15:07.320 --> 00:15:19.500 STFC-RAL-CR03-RAL-R61-2.01: So we do that because not only does that mean you're, reducing the thermal noise in your system, so you're going to have less noise, you might be able to reach lower energy… energy thresholds. 107 00:15:19.670 --> 00:15:28.799 STFC-RAL-CR03-RAL-R61-2.01: But you're also going to have, you also need to go down below the millikelvin scale to actually turn the helium-3 into a superfird. 108 00:15:29.210 --> 00:15:40.559 STFC-RAL-CR03-RAL-R61-2.01: You have extremely small quanta, so 10 to the minus 7 electron volt quanta. So, in other words, that means you put 1 electron volt into the system, you've got a 10 to the 7 quanta. 109 00:15:40.710 --> 00:15:42.180 STFC-RAL-CR03-RAL-R61-2.01: Pretty strong today. 110 00:15:43.510 --> 00:15:52.329 STFC-RAL-CR03-RAL-R61-2.01: You, we use, nano-electromechanical resonators to try and detect this wonder, and I'll come onto all of this, a bit later. 111 00:15:52.690 --> 00:16:08.139 STFC-RAL-CR03-RAL-R61-2.01: And then, to read out these nano-electromechanical resonators, we use low-noise quantum readouts, so something called SWIDs, try and reduce the amount of electrical noise they have in our system. But again, try and reach as low an energy threshold as possible. 112 00:16:08.580 --> 00:16:11.829 STFC-RAL-CR03-RAL-R61-2.01: So, the name of the game here is very different to 113 00:16:12.120 --> 00:16:31.459 STFC-RAL-CR03-RAL-R61-2.01: most direct detection experiments, where you're trying to reduce your backgrounds, you're trying to go deep, deep on the ground, for example, to look for very, very rare events, but higher energy. Here, we… the name of the game is just to reduce your energy threshold as much as you physically can. 114 00:16:31.560 --> 00:16:35.969 STFC-RAL-CR03-RAL-R61-2.01: Because that's gonna increase your sensitivity. 115 00:16:39.130 --> 00:16:56.769 STFC-RAL-CR03-RAL-R61-2.01: So, superfood Helium-3 is an interesting system, and I'm not going to go into the theoretical details of superfood, because I don't want to do. It's quite complicated, and I'm not a condensed math theorist, but, you know, I do my best. 116 00:16:57.870 --> 00:17:02.270 STFC-RAL-CR03-RAL-R61-2.01: You can imagine… if you can picture Helium 4, So… 117 00:17:02.450 --> 00:17:08.169 STFC-RAL-CR03-RAL-R61-2.01: It kind of makes sense. If you cool helium-4 down, you get rid of enough of that thermal energy. 118 00:17:09.020 --> 00:17:11.080 STFC-RAL-CR03-RAL-R61-2.01: Then, you have… 119 00:17:11.280 --> 00:17:17.430 STFC-RAL-CR03-RAL-R61-2.01: no one pens with germs. You can imagine, it forms a Bonsai compensate when you pull it down. 120 00:17:18.660 --> 00:17:27.299 STFC-RAL-CR03-RAL-R61-2.01: But you want to expect the same thing in PDM3. These are… these are sort of fermionic, right? Like, they have an unpaired nucleon, they have our integer spin. 121 00:17:27.300 --> 00:17:42.119 STFC-RAL-CR03-RAL-R61-2.01: But, weirdly enough, it does sort of form a Bose-Einstein-like state, a superfluid state, but it's the same as electrons in a superconductor. Once you get rid of enough of that thermal energy, they end up forming bound states. 122 00:17:42.660 --> 00:17:46.699 STFC-RAL-CR03-RAL-R61-2.01: That then form a sort of composite boronic-like object. 123 00:17:48.220 --> 00:17:52.460 STFC-RAL-CR03-RAL-R61-2.01: And the superfluid needle, the really interesting thing is, as I mentioned, the gap. 124 00:17:52.720 --> 00:18:05.460 STFC-RAL-CR03-RAL-R61-2.01: To turn that composite trooper there, we call them, into, to liberate that helium atom from that composite, and turn it into an excitation in your superfluid. It's 10 to the minus 7 electrons. 125 00:18:06.660 --> 00:18:15.809 STFC-RAL-CR03-RAL-R61-2.01: The… so this is the… the, phase diagram of… of Helium-3, so this 3D part is quite complicated, but there's a… 126 00:18:16.140 --> 00:18:21.400 STFC-RAL-CR03-RAL-R61-2.01: a sort of 2D representation of this side of it at zero magnetic field. 127 00:18:21.520 --> 00:18:27.159 STFC-RAL-CR03-RAL-R61-2.01: Where you see there's two phases, A phase and B phase, and then your normal liquid phase here. 128 00:18:27.390 --> 00:18:31.969 STFC-RAL-CR03-RAL-R61-2.01: the A phase is just to do with the, sort of, ordering of the, 129 00:18:32.550 --> 00:18:44.279 STFC-RAL-CR03-RAL-R61-2.01: magnetic spins in the helium, but the… in general, when we're talking about Quest, direct protection experiments, we are using B phase, because what… what you find is 130 00:18:44.550 --> 00:18:53.089 STFC-RAL-CR03-RAL-R61-2.01: when you create N phase, it quickly nucleates into B phase anyway, so your stable target is this B phase. And then… I'll use this. 131 00:18:53.860 --> 00:19:12.150 STFC-RAL-CR03-RAL-R61-2.01: And then, this is actually a plot of the heat capacity of Helium 3 at zero pressure against the temperature. So, you see, as you get down to about 1 to 2 millichelvin, you actually reach a peak in your heat capacity, and then you actually get an exponential falloff. 132 00:19:12.370 --> 00:19:19.899 STFC-RAL-CR03-RAL-R61-2.01: And in the insert area, you see between, sort of, 500 to zero, microkeleton. And this exponential fall-off 133 00:19:20.070 --> 00:19:25.260 STFC-RAL-CR03-RAL-R61-2.01: is what makes this so useful as a detector of energy, right? So… 134 00:19:25.370 --> 00:19:31.470 STFC-RAL-CR03-RAL-R61-2.01: As you go down, down, down in temperature, all of a sudden it means, for the same amount of energy. 135 00:19:31.770 --> 00:19:38.229 STFC-RAL-CR03-RAL-R61-2.01: you get a much larger… you get a much larger change in temperature. So if you can detect that change in temperature. 136 00:19:38.910 --> 00:19:41.510 STFC-RAL-CR03-RAL-R61-2.01: Which is the same as essentially expecting 137 00:19:41.830 --> 00:19:43.789 STFC-RAL-CR03-RAL-R61-2.01: The number of points around your system. 138 00:19:44.120 --> 00:19:51.119 STFC-RAL-CR03-RAL-R61-2.01: Then you can… you can start detecting tiny amounts of energy and get sensitivity to very low dark matter masses. 139 00:19:54.700 --> 00:20:03.420 STFC-RAL-CR03-RAL-R61-2.01: So what happens when, a bombard particle comes in, or any particle, I'd say, comes in, hits one of your medium atoms? 140 00:20:03.690 --> 00:20:08.690 STFC-RAL-CR03-RAL-R61-2.01: So, you're gonna end up with some elastic scattering, which will go into 141 00:20:08.690 --> 00:20:26.200 STFC-RAL-CR03-RAL-R61-2.01: your quasi-particle partition, so all of those onto that I mentioned before. But then you're also going to end up with some ionization, some excitation, you're going to get some recombination, you're going to form excited diner states, these are going to decay, eventually into, sort of, singlet and, 142 00:20:26.440 --> 00:20:39.900 STFC-RAL-CR03-RAL-R61-2.01: into this either being a singlet state or a triplet state, which then decay into UV photons. So these singlets on the state… on the, timescales of, like, nanoseconds into triplets on the timescales of maybe, like, 13 seconds or so. 143 00:20:40.050 --> 00:20:50.109 STFC-RAL-CR03-RAL-R61-2.01: And you actually find that, based on this sort of model, that I've referenced here, that for a nuclear recoil. 144 00:20:50.250 --> 00:20:58.040 STFC-RAL-CR03-RAL-R61-2.01: So, one of your Domite particles coming in, hitting the nucleus, compared to, you know, one of your dark particles coming in and hitting an electron. 145 00:20:58.200 --> 00:21:00.120 STFC-RAL-CR03-RAL-R61-2.01: Of your target atom. 146 00:21:00.270 --> 00:21:05.600 STFC-RAL-CR03-RAL-R61-2.01: that the… You have a noticeable difference. 147 00:21:05.710 --> 00:21:08.319 STFC-RAL-CR03-RAL-R61-2.01: In the ratio of these 148 00:21:08.320 --> 00:21:26.690 STFC-RAL-CR03-RAL-R61-2.01: channels. So, how much less energy ends up in new photons, how much of this energy ends up into infrared photons and quasi particles is going to be different depending on, whether it's new degree 12 or electronically 12. And this means that if you can actually detect not just the quasi-particle partition. 149 00:21:26.710 --> 00:21:28.029 STFC-RAL-CR03-RAL-R61-2.01: But also. 150 00:21:28.100 --> 00:21:34.690 STFC-RAL-CR03-RAL-R61-2.01: these UV photons, then you might end up getting really good feature power within your system between whether you're 151 00:21:34.880 --> 00:21:41.640 STFC-RAL-CR03-RAL-R61-2.01: You see an electroreo, whether you see a nuclear recall. And then, if you're searching for nuclear recalls, that's your signal. 152 00:21:41.900 --> 00:21:48.320 STFC-RAL-CR03-RAL-R61-2.01: You can get rid of a lot of background, because you can then say, okay, we know this is an electron recoil, we can throw it out. 153 00:21:51.630 --> 00:21:54.970 STFC-RAL-CR03-RAL-R61-2.01: So this is the, sort of, very general detection principle. 154 00:21:55.130 --> 00:22:00.199 STFC-RAL-CR03-RAL-R61-2.01: So, you have a dark matter particle come in, it comes in, you have a box. 155 00:22:00.340 --> 00:22:09.120 STFC-RAL-CR03-RAL-R61-2.01: Of helium, so this is about 1cm cute inside, and this is absolutely, absolutely tiny. And this is inside your cryostat. 156 00:22:10.560 --> 00:22:23.170 STFC-RAL-CR03-RAL-R61-2.01: You produce these quasi-particles, so 10 to the 7 of these excitations bouncing around in your box, for each electron volt that you've actually put in, by that recoil. 157 00:22:23.510 --> 00:22:36.790 STFC-RAL-CR03-RAL-R61-2.01: These then bounce around and hit a wire inside there, which is superconducting, and you're driving it with some AC current, and it's in a vertical bead field. So this is vibrating like this. 158 00:22:37.480 --> 00:22:41.700 STFC-RAL-CR03-RAL-R61-2.01: And it's actually a dumped oscillator, right? 159 00:22:41.990 --> 00:22:42.860 STFC-RAL-CR03-RAL-R61-2.01: I'm… 160 00:22:43.310 --> 00:22:51.990 STFC-RAL-CR03-RAL-R61-2.01: When you have these quasi parts with these excitations moving through your box, they actually will eventually exert force on your vibrating wire. 161 00:22:52.420 --> 00:22:59.500 STFC-RAL-CR03-RAL-R61-2.01: This force can then be read out as a change in the impedance of your circuit. 162 00:23:00.020 --> 00:23:11.530 STFC-RAL-CR03-RAL-R61-2.01: So that's how we recreate the amount of energy that's gone into our system. So we're essentially counting particles by measuring the force on our wire, the damping force on our vibrating wire, etc. 163 00:23:12.620 --> 00:23:13.290 STFC-RAL-CR03-RAL-R61-2.01: Boop. 164 00:23:14.700 --> 00:23:20.419 STFC-RAL-CR03-RAL-R61-2.01: So this is sort of an image… well, really a few images of a few of our barbarometers, 165 00:23:20.820 --> 00:23:27.980 STFC-RAL-CR03-RAL-R61-2.01: A barometer is just something that detects people. That's just why it's called a barometer. So you have, a box with an orifice. 166 00:23:27.980 --> 00:23:45.689 STFC-RAL-CR03-RAL-R61-2.01: The orifice is there because you want any blood particles that don't interact with your wire, you want them to be able to holistically propagate out of your box, so you have some time constant at which it relaxes back to its face temperature, so it's not just constantly eating up and eating up and heating up. 167 00:23:45.880 --> 00:23:48.979 STFC-RAL-CR03-RAL-R61-2.01: As you're… as you have more and more interactions in there. 168 00:23:49.140 --> 00:24:03.610 STFC-RAL-CR03-RAL-R61-2.01: Inside a llometer, you have your, two wires, so you have one which is a vibrating wire you use as your thermometer wire, measuring the temperature, and then you have one which is a heater wire, which you actually use for calibration, because you can then 169 00:24:03.610 --> 00:24:09.210 STFC-RAL-CR03-RAL-R61-2.01: Produce quasi-particles using that Peter, and then measure the response in your thermometer. 170 00:24:09.500 --> 00:24:18.540 STFC-RAL-CR03-RAL-R61-2.01: And here are a few pictures, so our initial prototypes were… were actually made of, literally graph paper, 171 00:24:18.660 --> 00:24:32.359 STFC-RAL-CR03-RAL-R61-2.01: encased in some, something called SkyPass, which is an epoxy, and, then these were wrapped in something called PEN, which is a wavelength shifter. The idea of this was to see whether we could actually cool down 172 00:24:32.520 --> 00:24:47.259 STFC-RAL-CR03-RAL-R61-2.01: these billometers and have them transparent to the UV scintillation. So then you could actually wrap them in the wavelength shifter to then detect the UV scintillation at a visible wavelength in something like a silicon photo multiplier. 173 00:24:47.480 --> 00:25:02.700 STFC-RAL-CR03-RAL-R61-2.01: But eventually, our, later models were using just copper, so we just started, looking at the key partition of the energy, and said, we're not going to bother at the moment about the UV partition. 174 00:25:02.700 --> 00:25:11.939 STFC-RAL-CR03-RAL-R61-2.01: Until future… until future models. We're just going to try and use comfort to try and get it as cold as possible. So, we're just looking at one of these, 175 00:25:11.940 --> 00:25:20.569 STFC-RAL-CR03-RAL-R61-2.01: energy partitions, just for heat, and just trying to get the actual thermometer itself as cold as possible. And you can see one of these guys here. 176 00:25:21.040 --> 00:25:24.770 STFC-RAL-CR03-RAL-R61-2.01: Next to a penny, so you can see how tiny these things actually are. 177 00:25:30.230 --> 00:25:31.210 STFC-RAL-CR03-RAL-R61-2.01: So… 178 00:25:31.460 --> 00:25:42.620 STFC-RAL-CR03-RAL-R61-2.01: I'm not going to spend tons of time on this, but the cryogenics is the interesting thing. I mean, the interesting thing about how you get these things cold is you have to use two different methods, so… 179 00:25:42.900 --> 00:25:46.900 STFC-RAL-CR03-RAL-R61-2.01: It's classic dilution refrigeration using heating, heating floor. 180 00:25:47.040 --> 00:25:54.290 STFC-RAL-CR03-RAL-R61-2.01: Where we can get… we get down to about maybe 10 millikelvin using this, using this method, so you kind of… 181 00:25:54.510 --> 00:26:00.300 STFC-RAL-CR03-RAL-R61-2.01: recool a mixture of even doing 3 and even 4 to about 4K. You then… let me just gonna get… 182 00:26:00.510 --> 00:26:04.119 STFC-RAL-CR03-RAL-R61-2.01: You then pump… pump it down through your fridge. 183 00:26:04.390 --> 00:26:06.780 STFC-RAL-CR03-RAL-R61-2.01: It then reaches a mixing chamber. 184 00:26:07.060 --> 00:26:24.170 STFC-RAL-CR03-RAL-R61-2.01: You then produce a concentrated phase and a dilute phase, where the dilute phase has 6.6% helium-3, the concentrated phase is all helium-3. And this is a temperature where the helium-4 is a constituted fluid, but the helium-3 is just potentially a gas. 185 00:26:24.460 --> 00:26:27.799 STFC-RAL-CR03-RAL-R61-2.01: And you pump it through. 186 00:26:28.240 --> 00:26:30.059 STFC-RAL-CR03-RAL-R61-2.01: You pump the healing 3 through. 187 00:26:30.260 --> 00:26:34.039 STFC-RAL-CR03-RAL-R61-2.01: And through… through… back through your system pay-ups and still. 188 00:26:34.100 --> 00:26:52.739 STFC-RAL-CR03-RAL-R61-2.01: But then, actually, EM3, moving from the concentrated phase to the dilute phase, it costs empathy, which means that you actually reduce the temperature of your system here at the mixing chamber. So then, you will, you know, if you're just using a dilution fridge without caring about getting any colder. 189 00:26:52.840 --> 00:27:05.199 STFC-RAL-CR03-RAL-R61-2.01: You would then put your platform for your experiments, sort of, around this mixing chamber, so they would be thermally connected to this. So then you would cool down your platform, cool down your experiment, and then you could run it. 190 00:27:05.320 --> 00:27:07.200 STFC-RAL-CR03-RAL-R61-2.01: But that's not common enough for us. 191 00:27:07.920 --> 00:27:26.089 STFC-RAL-CR03-RAL-R61-2.01: And we actually use something called Adyebactic nuclear demagnetization. So, we attach a nuclear stage, which is like a big box of copper for us, to, a dilution fridge. We cool it down to 10 millKelvin, and then we actually disconnect it thermally, using something called the Peak switch. 192 00:27:26.260 --> 00:27:30.109 STFC-RAL-CR03-RAL-R61-2.01: And then you reduce the magnetic field. 193 00:27:30.640 --> 00:27:41.359 STFC-RAL-CR03-RAL-R61-2.01: And you actually have… you actually find that the… the field… the ratio of the field to the temperature has to stay constant, so you end up reducing your temperature as you go from a high field to a low field. 194 00:27:41.460 --> 00:27:50.389 STFC-RAL-CR03-RAL-R61-2.01: And we can get down to about 100 microKelbins, and that's 100 microkelb actually in our llometer, for the actual, 195 00:27:50.990 --> 00:27:53.049 STFC-RAL-CR03-RAL-R61-2.01: nuclear stage, that's a lot colder than that. 196 00:27:56.350 --> 00:28:09.769 STFC-RAL-CR03-RAL-R61-2.01: So, the nano-electromechanical resonators, so this is how we actually, detect these excitations inside our superfluid. So, as I said, these are, like, little vibrating superproductive wires, and these are actually made by hand. 197 00:28:10.080 --> 00:28:20.310 STFC-RAL-CR03-RAL-R61-2.01: So this is a 400 nanometer diameter wire. Holy at the back, you might not even be able to see that, but it sort of runs from here to here. 198 00:28:20.600 --> 00:28:24.879 STFC-RAL-CR03-RAL-R61-2.01: Where it's been picked up by these two So, larger legs. 199 00:28:25.220 --> 00:28:30.110 STFC-RAL-CR03-RAL-R61-2.01: Just take a picture of it and, attach with some epoxy. 200 00:28:30.420 --> 00:28:31.440 STFC-RAL-CR03-RAL-R61-2.01: Resident. 201 00:28:32.520 --> 00:28:37.880 STFC-RAL-CR03-RAL-R61-2.01: And then this is a slightly larger wire, so this is a 4.5 micron. 202 00:28:38.380 --> 00:28:42.710 STFC-RAL-CR03-RAL-R61-2.01: Going from there to that, attached to some proper legs here by some epoxy. 203 00:28:43.320 --> 00:29:00.930 STFC-RAL-CR03-RAL-R61-2.01: And, these are made by our, collaborators in Lancaster by hand, like I said, and they do this by essentially having sort of a matrix of, I think copper and titanium wires, and then they stretch this thing out through some diamond dies to try and get it to the diodes that they want. 204 00:29:00.930 --> 00:29:06.850 STFC-RAL-CR03-RAL-R61-2.01: And then they go in individually by hand and pick out the Niobium, titanium. 205 00:29:07.090 --> 00:29:15.050 STFC-RAL-CR03-RAL-R61-2.01: Wires that they want to then go and attach it to some, some legs, to then go and plug in one of our velometers. 206 00:29:18.450 --> 00:29:20.979 STFC-RAL-CR03-RAL-R61-2.01: sort of switch, as I said, so we weed out 207 00:29:21.150 --> 00:29:40.790 STFC-RAL-CR03-RAL-R61-2.01: we attach this thing to an electrical circuit inside our volumeter, and then we read it out using something called a squid. So it's a superproductive quantum interference device. There's a SEM picture of one here, and then there's a nice cartoon of one here, but these are essentially just very sensitive magnetometers. 208 00:29:41.120 --> 00:29:48.899 STFC-RAL-CR03-RAL-R61-2.01: So, in our system, we have our… this is our, vibrating nanowire circuit here. We… 209 00:29:49.690 --> 00:30:01.220 STFC-RAL-CR03-RAL-R61-2.01: magnetically couple this, inductively couple this, to our SWID, which we then read out using, a lock-in amplifier to reduce noise at the frequencies we don't want. 210 00:30:01.660 --> 00:30:11.100 STFC-RAL-CR03-RAL-R61-2.01: And essentially, it's as simple as the current increases through your, Vibrating on a wire circuit. 211 00:30:12.290 --> 00:30:21.889 STFC-RAL-CR03-RAL-R61-2.01: then this is industrially cooled to this squid. This… this squid then amplifies that current by sensing the change in magnetic flux through 212 00:30:22.020 --> 00:30:27.770 STFC-RAL-CR03-RAL-R61-2.01: Through the actual, loop, where this is just two jurisdunctions on… 213 00:30:28.090 --> 00:30:30.399 STFC-RAL-CR03-RAL-R61-2.01: Either side of the Super Booking loop. 214 00:30:33.540 --> 00:30:34.840 STFC-RAL-CR03-RAL-R61-2.01: So, I'm… 215 00:30:35.080 --> 00:30:48.670 STFC-RAL-CR03-RAL-R61-2.01: Tell a bit about, tell you a bit now about how we actually use these methods to, detect the quantum in our system, actually, how we actually reconstruct, energies in our, thermometers. 216 00:30:49.690 --> 00:30:54.520 STFC-RAL-CR03-RAL-R61-2.01: So, I'm just going to mention this paper that got released this year from, 217 00:30:54.830 --> 00:31:12.970 STFC-RAL-CR03-RAL-R61-2.01: from the collaboration, where it was a very in-depth study of cooling down these nanowires with the squid readout circuit, and they had two wires in their bellometer, one 400 nanometer and one 4.5 micron. 218 00:31:13.060 --> 00:31:22.040 STFC-RAL-CR03-RAL-R61-2.01: And this is a picture of the longest seller used, which is attached to this larger, sort of, copper structure, and heat exchanger. 219 00:31:22.230 --> 00:31:29.189 STFC-RAL-CR03-RAL-R61-2.01: Which sat inside of their BrightStat, so this is a picture of one of these fridges, so it would have sat… 220 00:31:29.510 --> 00:31:32.980 STFC-RAL-CR03-RAL-R61-2.01: Around here, at this stage. 221 00:31:33.270 --> 00:31:40.009 STFC-RAL-CR03-RAL-R61-2.01: Yeah, it doesn't really look like an old bridge, but trust me, that's this… that's a bridge. 222 00:31:40.150 --> 00:31:42.020 STFC-RAL-CR03-RAL-R61-2.01: And they… 223 00:31:42.800 --> 00:31:51.309 STFC-RAL-CR03-RAL-R61-2.01: Yeah, well, I'll mention a little bit more. So, they essentially just cooled these things down, they showed that we could actually, do a long-term 224 00:31:51.480 --> 00:32:00.919 STFC-RAL-CR03-RAL-R61-2.01: run with these squids reading out these vibrating nanowires. We could reconstruct, energies as we thought, and we… 225 00:32:02.740 --> 00:32:07.479 STFC-RAL-CR03-RAL-R61-2.01: Essentially, to look at the wire. 226 00:32:07.770 --> 00:32:23.279 STFC-RAL-CR03-RAL-R61-2.01: we characterize the device by doing a large sweep across all frequencies. So remember, we're driving… we can drive these wires… yeah. Remember, we're driving these wires with some input circuit, so we're driving at some given frequency with some… some ordinary current. 227 00:32:23.670 --> 00:32:29.009 STFC-RAL-CR03-RAL-R61-2.01: So… You can do a… do a sweep of props. 228 00:32:29.440 --> 00:32:37.579 STFC-RAL-CR03-RAL-R61-2.01: A large range of frequencies, and find that actually your wire, which, remember, is a damp oscillator, has some resonant frequency. 229 00:32:38.270 --> 00:32:41.460 STFC-RAL-CR03-RAL-R61-2.01: So, this resident frequency report has S0. 230 00:32:41.680 --> 00:32:43.520 STFC-RAL-CR03-RAL-R61-2.01: And it has a month due date. 231 00:32:44.200 --> 00:32:51.449 STFC-RAL-CR03-RAL-R61-2.01: And this… Full width at heart maximum DF, is what we call the line width, or just the width. 232 00:32:51.830 --> 00:32:59.329 STFC-RAL-CR03-RAL-R61-2.01: And that's… that's essentially the variable we use to reconstruct The force on our wire. 233 00:33:00.060 --> 00:33:00.900 STFC-RAL-CR03-RAL-R61-2.01: So… 234 00:33:01.170 --> 00:33:08.799 STFC-RAL-CR03-RAL-R61-2.01: When you do a sweep across these frequencies around the resonance, you see that actually you get a nice fit to a complex Orencian. 235 00:33:09.210 --> 00:33:12.279 STFC-RAL-CR03-RAL-R61-2.01: With an amplitude that's actually, 236 00:33:12.970 --> 00:33:26.210 STFC-RAL-CR03-RAL-R61-2.01: Related to the length of the wire, the effective length of the wire, which is about a millimeter in this case, the magnetic field that's in, then also the mass of the wire. Remember, this is not just an electrical object, this is also a mechanical object as well. 237 00:33:27.870 --> 00:33:32.199 STFC-RAL-CR03-RAL-R61-2.01: So then… Once you've understood your wire resonance. 238 00:33:32.470 --> 00:33:43.200 STFC-RAL-CR03-RAL-R61-2.01: what you do is you just drive at the resonant frequency, so you say, okay, I understand what the resonance looks like, I understand if I… 239 00:33:43.500 --> 00:33:50.389 STFC-RAL-CR03-RAL-R61-2.01: driving the resonant frequency, and I look for a change in the amplitude, Which is just the voltage. 240 00:33:51.240 --> 00:33:55.860 STFC-RAL-CR03-RAL-R61-2.01: But for the change in the altitude, in my impedance. 241 00:33:56.210 --> 00:34:03.590 STFC-RAL-CR03-RAL-R61-2.01: then I can reconstruct this variable DF, which is actually proportional to the force possible work. 242 00:34:04.450 --> 00:34:12.889 STFC-RAL-CR03-RAL-R61-2.01: So this is what that kind of data looks like. So you drive the wire in resonance, you're measuring beads to the wire, then you restructure your width. 243 00:34:13.420 --> 00:34:17.659 STFC-RAL-CR03-RAL-R61-2.01: And… This is an example of… 244 00:34:18.080 --> 00:34:23.960 STFC-RAL-CR03-RAL-R61-2.01: The time series dates that you get, so this is about, what, so half an hour? Yeah, half an hour or so. 245 00:34:24.460 --> 00:34:31.599 STFC-RAL-CR03-RAL-R61-2.01: And we have one of these pulses here, in red, where you've got a zoomed-in block here. 246 00:34:32.000 --> 00:34:43.830 STFC-RAL-CR03-RAL-R61-2.01: Of a characteristic, nice shape, where it's all a double exponential, where you have one time constant, which is dependent on the wire, and how fast the wire actually reacts to, and it changes. 247 00:34:43.850 --> 00:34:53.649 STFC-RAL-CR03-RAL-R61-2.01: So that's… that's actually determined by the mass of the Y, for example. And then you have a time constant that's determined by the orifice and the volume. 248 00:34:53.690 --> 00:34:59.509 STFC-RAL-CR03-RAL-R61-2.01: Of your barometer, so just how fast that barometer's actually going to cool back down to its base temperature. 249 00:35:03.700 --> 00:35:14.320 STFC-RAL-CR03-RAL-R61-2.01: You can also do, things like drive amplitude sweeps. So, essentially, you look at the relationship between the force on your wire and the velocity of the wire. 250 00:35:14.620 --> 00:35:20.999 STFC-RAL-CR03-RAL-R61-2.01: And… You can increase your drive current, measure the velocity. 251 00:35:21.310 --> 00:35:31.279 STFC-RAL-CR03-RAL-R61-2.01: And you see, at some point, you end up getting this change in behavior, and you can also see it on this spot here, where this has been converted to force. 252 00:35:32.900 --> 00:35:52.200 STFC-RAL-CR03-RAL-R61-2.01: you get this change in behavior. So what's happening here is actually the wire itself becomes pair-breaking. So, the wire itself is going fast enough to just create positive particles by itself. It's not just a quasi-particle detector now, it's a quasi-particle creator. It's breaking apart those super pairs in your, 253 00:35:52.300 --> 00:36:00.399 STFC-RAL-CR03-RAL-R61-2.01: In your barometer. So now, at this point, past this point, it's useless as a detector of excitations. 254 00:36:00.970 --> 00:36:01.800 STFC-RAL-CR03-RAL-R61-2.01: But… 255 00:36:01.940 --> 00:36:20.129 STFC-RAL-CR03-RAL-R61-2.01: Below this point, this is the… this is the operating range. You see that in the inset here, where we're going between, sort of, 0 and 15, you've got, sort of, a nice linear regime here, and then at some point it becomes nonlinear, so your velocity and force relation is no longer nicely linear. 256 00:36:20.750 --> 00:36:27.449 STFC-RAL-CR03-RAL-R61-2.01: So… This… this makes it a little bit trickier to operate in this, regime. 257 00:36:27.710 --> 00:36:34.960 STFC-RAL-CR03-RAL-R61-2.01: But you actually win, because the higher your velocity, the larger your signals are. 258 00:36:36.370 --> 00:36:39.839 STFC-RAL-CR03-RAL-R61-2.01: So, if we can operate in this regime, then it's very useful. 259 00:36:42.370 --> 00:37:01.739 STFC-RAL-CR03-RAL-R61-2.01: And I won't go into this too much, but essentially you find that you can use… but you can actually use some correction, which is some, actually some nasty mix of, like, Betel and screwed functions, to then run in this nonlinear regime and correct 260 00:37:02.400 --> 00:37:12.320 STFC-RAL-CR03-RAL-R61-2.01: what you read out as your, width, your base width. So you have your intrinsic width, and then the width that you're getting from the, interactions in your 261 00:37:12.420 --> 00:37:24.189 STFC-RAL-CR03-RAL-R61-2.01: in your volumeter, and I'm not going to spend too much time, so I'm running a bit slow, but essentially, you can run in this nonlinear regime, we've shown you can do it, and… 262 00:37:24.470 --> 00:37:26.139 STFC-RAL-CR03-RAL-R61-2.01: You actually win quite a lot. 263 00:37:28.300 --> 00:37:36.279 STFC-RAL-CR03-RAL-R61-2.01: This is how we calibrate our wires, so I mentioned you have a thermometer wire and a heater wire, so what you do to calibrate 264 00:37:36.280 --> 00:37:51.130 STFC-RAL-CR03-RAL-R61-2.01: is you inject known power through your heater wire to produce quasi-particles in your barometer, then you read out what you get from your thermometer. So that's essentially what's happening here. This is the power that you're putting in to 265 00:37:51.130 --> 00:37:57.120 STFC-RAL-CR03-RAL-R61-2.01: Your repeater wire, and then eventually you can get some, measurement of width 266 00:37:58.130 --> 00:38:08.000 STFC-RAL-CR03-RAL-R61-2.01: From your thermometer, as opposed to the get some calibration of, energy and quasi-particle… 267 00:38:08.320 --> 00:38:25.160 STFC-RAL-CR03-RAL-R61-2.01: And I will mention also, we're currently commissioning a 955 calibration source to actually put, in or right next to one of these thermometers to get a nice measurement of the actual partition in both heat and, and singlet and driven. 268 00:38:26.300 --> 00:38:40.169 STFC-RAL-CR03-RAL-R61-2.01: Sources of noise… yeah, this is the… this is the real problem. I think we're now at a point where we're just essentially finding how we can reduce all of the noise in assets of… to, 269 00:38:40.280 --> 00:38:52.070 STFC-RAL-CR03-RAL-R61-2.01: to then get to as low an energy threshold as we possibly can. So, it's also annoyed with things like vibrations coupling to the wire, so here, for example, this is the frequency shift from your personal frequency. 270 00:38:52.360 --> 00:39:03.320 STFC-RAL-CR03-RAL-R61-2.01: most of your noise is not coming from the Squid 3i itself, but it's actually coming from installing to the wire, and sometimes you might be particularly unlucky and have 271 00:39:03.320 --> 00:39:18.119 STFC-RAL-CR03-RAL-R61-2.01: particular frequencies that are sitting right on top of your resonance. And you also have, obviously, operation of the squid that has some, dependence of the vibrations in the squid itself, the magnetic field, and also the temperature you can get down to. 272 00:39:20.030 --> 00:39:37.400 STFC-RAL-CR03-RAL-R61-2.01: Filtering, I will just mention that we're kind of, at the moment, using things like knock-thawk filters to reduce the, the energy threshold we can get to, but in the future, there's some work on using machine learning-based noise reduction, in our data, which could 273 00:39:37.400 --> 00:39:41.119 STFC-RAL-CR03-RAL-R61-2.01: You're with really, really, really, really good improvements, essentially. 274 00:39:43.460 --> 00:39:59.290 STFC-RAL-CR03-RAL-R61-2.01: So, current operation, there's work being done, in Lancaster at the moment. We've pulled down one of these cryostats, a different cryostat now, so, this is actually the coldest blocks we've had yet, so about 120 microkelvin. 275 00:39:59.480 --> 00:40:08.010 STFC-RAL-CR03-RAL-R61-2.01: With a full squid readout as well, so this is just one exit of one pulse from some early data, but we are… 276 00:40:08.310 --> 00:40:14.960 STFC-RAL-CR03-RAL-R61-2.01: We're looking forward to seeing how well we can do with this, because this… we've never… we've never got this cold before. 277 00:40:14.960 --> 00:40:29.960 STFC-RAL-CR03-RAL-R61-2.01: The coldest we had, we got before with maybe about 150 microKelvin, but then that was also not with a squid readout at all. That was using a cold transformative amplified signal, which is actually a lot noisier than using a squid. So, I'd say watch this space. 278 00:40:32.370 --> 00:40:35.920 STFC-RAL-CR03-RAL-R61-2.01: So, just going on to quickly sources of background in the experiment. 279 00:40:36.080 --> 00:40:54.980 STFC-RAL-CR03-RAL-R61-2.01: So you can do your GM4 simulation of what… where you expect the event rates in your detector to be. So this is the, energy deposited in your billetre cell as a function of energy, and, this is the rate in, per kilogram per day per kV. 280 00:40:55.500 --> 00:41:01.059 STFC-RAL-CR03-RAL-R61-2.01: And… From this line, you can see that 281 00:41:01.530 --> 00:41:12.530 STFC-RAL-CR03-RAL-R61-2.01: majority of the background events, the non-dark matter events, are going to come from cosmic neurons. So we're not deep underground, we're on the Earth's surface. 282 00:41:12.530 --> 00:41:23.580 STFC-RAL-CR03-RAL-R61-2.01: So you have a large background from these, so if you can increase your visa power to these cosmic muons, then you're going to increase your sensitivity to dark matter interactions. 283 00:41:24.390 --> 00:41:28.910 STFC-RAL-CR03-RAL-R61-2.01: Coming on to… What's… what's, being worked on here at Runel? 284 00:41:28.940 --> 00:41:46.469 STFC-RAL-CR03-RAL-R61-2.01: So it's actually a development of this ecosystem happening here at RAL. So you're getting a scintillator block, you mold this, you put this inside your fridge, around your billometer, then you can do some trigger logic. At the moment, we're using something called a red tire PGA, board. 285 00:41:46.640 --> 00:41:54.669 STFC-RAL-CR03-RAL-R61-2.01: then you can reject coincident events between your veto and your belonger to Hainesberg with that sensitivity. 286 00:41:55.440 --> 00:42:09.400 STFC-RAL-CR03-RAL-R61-2.01: There's also been work demonstrating photon channel readout, at 10 millikelvin using, silicon photomultipliers, so eventually we can use this both in the veto system, but also eventually probably to, to… 287 00:42:09.640 --> 00:42:19.709 STFC-RAL-CR03-RAL-R61-2.01: Detect the scintillation channel, as well as the quasi-particle channel, to be able to get that electron recoil, nuclear recoil, beta power forward. 288 00:42:22.170 --> 00:42:23.330 STFC-RAL-CR03-RAL-R61-2.01: And, yeah. 289 00:42:23.560 --> 00:42:26.070 STFC-RAL-CR03-RAL-R61-2.01: Quest DMC at around PPD, so… 290 00:42:26.350 --> 00:42:41.000 STFC-RAL-CR03-RAL-R61-2.01: There's a lot going on. The data processing and infrastructure for the current run in Lancaster. Joe's doing a lot of work on that. Development of machine learning-based filtering and pulse filing. Joe's also working on, I think, to reduce the experimental threshold. 291 00:42:41.060 --> 00:42:52.070 STFC-RAL-CR03-RAL-R61-2.01: the R&D for the cosmic muon veto system, and eventually this could have an extra quantum error correction, because cosmic muons are actually quite an issue for qubits as well. 292 00:42:52.390 --> 00:43:06.590 STFC-RAL-CR03-RAL-R61-2.01: There's a commissioning of the cryolab happening, so we've got 20 millikalvin bridge arriving in the very near future, and then heavy involvement in producing a low threshold biomark search. And I'll just finish on one more slide. 293 00:43:07.440 --> 00:43:08.320 STFC-RAL-CR03-RAL-R61-2.01: So… 294 00:43:08.660 --> 00:43:18.790 STFC-RAL-CR03-RAL-R61-2.01: This is just a potential sensitivity, going back to the pots I showed at the start, where we assume we have 5, you know, 0.3cm cells. 295 00:43:18.790 --> 00:43:31.819 STFC-RAL-CR03-RAL-R61-2.01: With a 6-month run of a 50% future cycle, so essentially on 50% of time, and then half the electron volt threshold, with SWID readout. So this was reported in, EPJC. 296 00:43:32.390 --> 00:43:33.890 STFC-RAL-CR03-RAL-R61-2.01: And you can see. 297 00:43:34.250 --> 00:43:42.560 STFC-RAL-CR03-RAL-R61-2.01: With these assumptions, there's a chance that we could end up getting down to world-leading sensitivity in the spin-dependent dark matter interaction space. 298 00:43:43.000 --> 00:43:50.339 STFC-RAL-CR03-RAL-R61-2.01: So I think I will… Yeah. You sure? Yeah. What? 299 00:43:50.340 --> 00:44:07.860 STFC-RAL-CR03-RAL-R61-2.01: Okay. Conclusions. West EMC collaboration is searching for sub-GV dark matter using superfluid helium-3 and a low-noise quantum readout. We've demonstrated switch readout of these vibrating nanowires and pulse detection using them. 300 00:44:07.860 --> 00:44:21.370 STFC-RAL-CR03-RAL-R61-2.01: Currently operating our coldest barometer so far, which includes the squid readout. There's heavy involvement from the PPD group here, especially in the development of the beta systems, and then the upcoming firearm as well. And… 301 00:44:21.400 --> 00:44:27.780 STFC-RAL-CR03-RAL-R61-2.01: The experiment is working towards world-leading sensitivity, spin-dependent dark matter interactions, and… 302 00:44:28.170 --> 00:44:30.520 STFC-RAL-CR03-RAL-R61-2.01: Or the future of the experimenters, right? 303 00:44:37.420 --> 00:44:39.180 STFC-RAL-CR03-RAL-R61-2.01: Questions. 304 00:44:40.750 --> 00:44:43.669 STFC-RAL-CR03-RAL-R61-2.01: Stone and silence. Yeah, bit. 305 00:44:44.030 --> 00:44:46.230 STFC-RAL-CR03-RAL-R61-2.01: Ask what is some… 306 00:44:46.610 --> 00:45:04.360 STFC-RAL-CR03-RAL-R61-2.01: the thermal coefficient. It has this peak up to 1 millikov. That looked like the transition temperature of the liquid to go super fluid. Yeah. Is that… I mean, is the width of it then… what's the width of that? But it seems, you know… 307 00:45:04.500 --> 00:45:07.480 STFC-RAL-CR03-RAL-R61-2.01: Yeah, that's a good question, right? 308 00:45:07.790 --> 00:45:15.429 STFC-RAL-CR03-RAL-R61-2.01: I suppose the… the width… All the way back to the start. Did you mention this before? Yeah. Yeah. 309 00:45:15.880 --> 00:45:17.200 STFC-RAL-CR03-RAL-R61-2.01: I mean, the wicks. 310 00:45:18.650 --> 00:45:30.629 STFC-RAL-CR03-RAL-R61-2.01: I suppose you're going just into two regimes, I'm not sure if the width itself is an important quantity, but I guess you're going two regimes of non-superfluid, and then superfluid at this point. 311 00:45:31.400 --> 00:45:32.250 STFC-RAL-CR03-RAL-R61-2.01: But yeah. 312 00:45:33.320 --> 00:45:41.209 STFC-RAL-CR03-RAL-R61-2.01: It just feels like you use the transition temperature that's happening over a very large range of relative temperatures. 313 00:45:42.450 --> 00:45:45.560 STFC-RAL-CR03-RAL-R61-2.01: Well, I think the tran… well, I think the transition temperature is… 314 00:45:46.070 --> 00:45:47.650 STFC-RAL-CR03-RAL-R61-2.01: This point here is a peak. 315 00:45:51.020 --> 00:45:54.669 STFC-RAL-CR03-RAL-R61-2.01: It's not quite good. 316 00:45:55.900 --> 00:46:03.779 STFC-RAL-CR03-RAL-R61-2.01: Exactly. The Phase 1, Phase 2, that we see in NHC is a lot sharper position. 317 00:46:03.900 --> 00:46:04.705 STFC-RAL-CR03-RAL-R61-2.01: So. 318 00:46:07.650 --> 00:46:19.619 STFC-RAL-CR03-RAL-R61-2.01: No, yeah, I think that's just the transition to this one point, actually. Yeah. This is just going into the B phase, this is not taking into account, like, two different phases, right? 319 00:46:20.020 --> 00:46:36.279 STFC-RAL-CR03-RAL-R61-2.01: Well, you said that that's at zero pressure, right? Yeah. And kind of, like, you can kind of see in the… in the bottom right plot, like, the phase transition kind of has a minimal gradient at that point, so, like, would it be, like, if you go to higher pressures, that would get sharper? 320 00:46:36.280 --> 00:46:47.720 STFC-RAL-CR03-RAL-R61-2.01: You said? Yes, yeah, yeah. Well, yeah, the temperature, in which you go to see food increases at higher fiber. Yeah. But, like, if, if… 321 00:46:48.010 --> 00:46:54.610 STFC-RAL-CR03-RAL-R61-2.01: I guess I'm thinking that, like, if at zero pressure, like, the sort of the slope of that, of the phase boundary. 322 00:46:54.750 --> 00:47:00.480 STFC-RAL-CR03-RAL-R61-2.01: At… at zero bar, is at its shallow… is at its, sort of, lowest 323 00:47:00.640 --> 00:47:10.229 STFC-RAL-CR03-RAL-R61-2.01: And maybe if you go to higher pressures, it'll happen at a higher temperature, but the phase, like, the width of that heat might be sharper because the gradient is steeper. 324 00:47:10.920 --> 00:47:13.220 STFC-RAL-CR03-RAL-R61-2.01: Yeah, my thoughts will be able to highlight that, yeah. 325 00:47:13.950 --> 00:47:17.219 STFC-RAL-CR03-RAL-R61-2.01: It is supposed to be second bullet. 326 00:47:17.640 --> 00:47:27.620 STFC-RAL-CR03-RAL-R61-2.01: It is. And, I think it's supposed to be Lambda point, where… 327 00:47:27.820 --> 00:47:30.289 STFC-RAL-CR03-RAL-R61-2.01: into the universe. It's made a shark. 328 00:47:30.590 --> 00:47:36.429 STFC-RAL-CR03-RAL-R61-2.01: But what may happen here is probably the similar thing which happens in superconductors. 329 00:47:36.800 --> 00:47:39.260 STFC-RAL-CR03-RAL-R61-2.01: Is that the preferred formation? 330 00:47:39.390 --> 00:47:41.020 STFC-RAL-CR03-RAL-R61-2.01: And it was being solved. 331 00:47:41.460 --> 00:47:42.900 STFC-RAL-CR03-RAL-R61-2.01: So he's pretty cool. 332 00:47:43.020 --> 00:47:43.880 STFC-RAL-CR03-RAL-R61-2.01: Weird. 333 00:47:44.930 --> 00:47:52.150 STFC-RAL-CR03-RAL-R61-2.01: a more excitation. Yeah, it's… because, yeah, it's… Happens through the summit. 334 00:47:53.740 --> 00:47:57.789 STFC-RAL-CR03-RAL-R61-2.01: And another thing, in ISIS, we have 335 00:47:57.950 --> 00:48:03.690 STFC-RAL-CR03-RAL-R61-2.01: Very nice source for atmospheric, cosmic particles. 336 00:48:04.120 --> 00:48:15.159 STFC-RAL-CR03-RAL-R61-2.01: rules, and… Neutrons, we even have instruments generating neutrons to study the effect on semiconductor devices. 337 00:48:15.410 --> 00:48:20.039 STFC-RAL-CR03-RAL-R61-2.01: stuff that's happening. I'm just wondering if you can try to… 338 00:48:20.510 --> 00:48:23.049 STFC-RAL-CR03-RAL-R61-2.01: If you had one of them on Castro. 339 00:48:24.830 --> 00:48:31.570 STFC-RAL-CR03-RAL-R61-2.01: Vibration wires and exposure to Cosmic particles, we can generate them. 340 00:48:31.910 --> 00:48:40.450 STFC-RAL-CR03-RAL-R61-2.01: in huge numbers. Let's try and see how much it, like, deteriorates. We can… essentially, we can calibrate. Yeah, yeah, interesting. 341 00:48:43.010 --> 00:48:47.330 STFC-RAL-CR03-RAL-R61-2.01: But, yeah, do you think… Yeah, maybe. 342 00:48:48.600 --> 00:48:52.780 STFC-RAL-CR03-RAL-R61-2.01: Yeah, because I've never really… I've never really actually thought about how much they might be deteriorating. 343 00:48:52.900 --> 00:48:55.670 STFC-RAL-CR03-RAL-R61-2.01: the time, or the… the, 344 00:48:56.410 --> 00:49:01.400 STFC-RAL-CR03-RAL-R61-2.01: The usefulness of it, yeah. Same problem happens with modern computers. Yeah. 345 00:49:02.810 --> 00:49:04.230 STFC-RAL-CR03-RAL-R61-2.01: Nobody messaged it. 346 00:49:06.500 --> 00:49:07.959 Sean Paling - STFC UKRI: I've got a question on my… One wish. 347 00:49:09.070 --> 00:49:11.400 STFC-RAL-CR03-RAL-R61-2.01: Yes, please. 348 00:49:11.400 --> 00:49:32.930 Sean Paling - STFC UKRI: So, I don't know if you can hear me, it's Sean from Bulby. Thanks for the talk. Exciting project. Can you say a little bit more about the background? You said that, cosmic rays are a background, and yet you operate on the surface, and you're going to tackle it with a veto. Is there a reason you don't think about using an underground lab, for instance, Bulby? 349 00:49:32.930 --> 00:49:52.869 STFC-RAL-CR03-RAL-R61-2.01: There is no reason other than, we haven't been able to put it down well. I think, yeah, I think realistically, the question, if this question ever gets asked, the answer is always, like, we would love to, I think, put one of these, down underground. I think getting a… 350 00:49:52.920 --> 00:49:57.549 STFC-RAL-CR03-RAL-R61-2.01: Nuclear demagnetization fridge underground is for… 351 00:49:58.010 --> 00:50:04.839 STFC-RAL-CR03-RAL-R61-2.01: Hard part… well, apart from all the other physics, but… probably the hard part in terms of introscription. 352 00:50:06.380 --> 00:50:25.800 Sean Paling - STFC UKRI: Well, just to be clear, I mean, we are getting a dilution fridge underground at Borby, and we have spoken about a nuclear demagnetization stage, so, you know, certainly don't rule it out, but… so, I mean, but if you try and tackle it by just muon veto, is that enough? Doesn't that… what are the downsides to that? Does it give you dead time problems, or… 353 00:50:25.800 --> 00:50:26.500 STFC-RAL-CR03-RAL-R61-2.01: Also. 354 00:50:26.500 --> 00:50:28.359 Sean Paling - STFC UKRI: residuals that you can't get rid of. 355 00:50:29.440 --> 00:50:38.489 STFC-RAL-CR03-RAL-R61-2.01: Yeah, yeah, I mean, 100%, the more we can reduce the background, the better it's going to be for us. I think we live in a regime in, 356 00:50:38.750 --> 00:50:56.130 STFC-RAL-CR03-RAL-R61-2.01: in the likes of the mass world, where our expected signal rates are high, it's just the energies are low, so we can kind of live with a certain level of backgrounds that, like, larger detectors for high-mass particles can't. But 357 00:50:56.390 --> 00:51:05.110 STFC-RAL-CR03-RAL-R61-2.01: the more you can do to reduce your background, the better. So, I think in reality, putting something down above me would be fantastic. 358 00:51:05.390 --> 00:51:19.430 STFC-RAL-CR03-RAL-R61-2.01: Yeah. Can I add something? So, Sean, yeah, so I think we haven't actually fully characterized, like, the dead time that would be associated with this, because obviously it's still under development. I would expect that there would be a dead time associated, which would affect the sensitivity. 359 00:51:19.430 --> 00:51:34.450 STFC-RAL-CR03-RAL-R61-2.01: But the thing is, then, in that case, you just run for longer. And actually, we've been able to show that we can run for quite a while. So, you know, I think you could win back that sensitivity just by operating, sort of, more stably for longer, to counteract that. You know, but again, it needs to be quantified, but… 360 00:51:35.370 --> 00:51:41.310 Sean Paling - STFC UKRI: Okay, well, I mean, so, yeah, okay, well, don't rule us out. If there's ways in which we can help 361 00:51:42.480 --> 00:51:43.290 Sean Paling - STFC UKRI: We are hungry. 362 00:51:43.290 --> 00:51:48.070 STFC-RAL-CR03-RAL-R61-2.01: 100% are not ruling you out. We would love to go underground. 363 00:51:48.070 --> 00:52:03.249 Sean Paling - STFC UKRI: I mean, because it's a very similar problem that a lot of the dark matter experiments have, of course, dead time, and also sort of residual backgrounds that come from the cosmic rays. So, you know, you're entering into a world that's 364 00:52:03.500 --> 00:52:08.979 Sean Paling - STFC UKRI: well considered by other, other projects, so… Anyway, great talk. Thank you. 365 00:52:09.790 --> 00:52:28.539 STFC-RAL-CR03-RAL-R61-2.01: why don't you have a neutrino background? So, we do have a neutrino background, but it is tiny in comparison. So, let's say… so we've got a rate of, like, 10 to the 4 here. I think the neutrino background's, maybe, like, 10 to the… 366 00:52:28.720 --> 00:52:31.580 STFC-RAL-CR03-RAL-R61-2.01: That's the minus 8, something like that? Yeah. 367 00:52:31.830 --> 00:52:34.200 STFC-RAL-CR03-RAL-R61-2.01: But then it would be competitive with a single. 368 00:52:34.910 --> 00:52:41.229 STFC-RAL-CR03-RAL-R61-2.01: Well, actually, no, so the signal we're looking for, the kind of cross-section we're testing, are… 369 00:52:41.810 --> 00:52:42.940 STFC-RAL-CR03-RAL-R61-2.01: gonna be… 370 00:52:43.460 --> 00:52:50.769 STFC-RAL-CR03-RAL-R61-2.01: Well, you'd like to get as low as possible, right? But realistically, the rates are going to be much higher in that industry. 371 00:52:51.640 --> 00:53:02.889 STFC-RAL-CR03-RAL-R61-2.01: They're going to be more comparative to these rates than they are to the background, yeah. That's just… detect is so small. Yes, detect is really small, but also the… 372 00:53:03.020 --> 00:53:17.769 STFC-RAL-CR03-RAL-R61-2.01: this is why it's a kind of a different school of thought compared to the large Starbucks in Texas, because they're looking for higher energy, very, very weak, very, very rare signals, where we're not too bothered about super rare signals. 373 00:53:17.880 --> 00:53:22.599 STFC-RAL-CR03-RAL-R61-2.01: But we just need to detect very small energies, very small recalls, yeah. 374 00:53:24.090 --> 00:53:28.430 STFC-RAL-CR03-RAL-R61-2.01: How does the screen readout work? Is the two… 375 00:53:28.640 --> 00:53:40.420 STFC-RAL-CR03-RAL-R61-2.01: a closed cooling system that, so could flow it, or put together? So, it's actually kind of put together. So, if you imagine you have your 376 00:53:40.720 --> 00:53:42.760 STFC-RAL-CR03-RAL-R61-2.01: bike, fridge. 377 00:53:43.560 --> 00:53:47.519 STFC-RAL-CR03-RAL-R61-2.01: then you can… You have your, 378 00:53:47.720 --> 00:53:55.410 STFC-RAL-CR03-RAL-R61-2.01: down here, I'm not sure exactly where it would be, but… but you have… let's say you call this part of your fridge, let's say it's this plate here, for example, or this plate here. 379 00:53:55.800 --> 00:54:07.029 STFC-RAL-CR03-RAL-R61-2.01: You know, your gold is part of the bridge, and you put your, volumeter, which is actually, realistically, it's, like, inside a much larger, sort of, oxy… 380 00:54:07.860 --> 00:54:12.530 STFC-RAL-CR03-RAL-R61-2.01: cancer, basically, that you put… On the infrared terminally, 381 00:54:12.830 --> 00:54:25.840 STFC-RAL-CR03-RAL-R61-2.01: only, couplet to the fridge. But then you'd also put your squid, which is sitting… your squid chip, which is sitting inside of a dynamic titanium shield, so it doesn't get any interference from 382 00:54:26.540 --> 00:54:37.370 STFC-RAL-CR03-RAL-R61-2.01: like, straight magnetic fields, and you put that also on this platform. So it's cooled down the same fridge that's cooling down the… 383 00:54:37.500 --> 00:54:41.579 STFC-RAL-CR03-RAL-R61-2.01: But the temperature will be, slightly different. It will be higher, yeah, exactly, yeah. 384 00:54:44.190 --> 00:54:49.920 STFC-RAL-CR03-RAL-R61-2.01: Are there any other questions, Jacob? Yes, there is another one now, actually. 385 00:54:51.040 --> 00:54:53.679 STFC-RAL-CR03-RAL-R61-2.01: Yeah, one, John. 386 00:54:53.680 --> 00:54:58.740 Wonjong Chang: May I… okay, can you hear me? 387 00:54:59.130 --> 00:54:59.610 STFC-RAL-CR03-RAL-R61-2.01: Yes. 388 00:55:00.030 --> 00:55:04.850 Wonjong Chang: Okay, thank you. Okay, thank you for the really interesting talk. 389 00:55:05.000 --> 00:55:19.620 Wonjong Chang: I actually had some curiosities about the, the cutting-edge, readout and sensors. So, first of all, I was quite curious, like, what's the actual, 390 00:55:20.310 --> 00:55:22.969 Wonjong Chang: Resolution of the, the magnetometer. 391 00:55:23.900 --> 00:55:27.139 Wonjong Chang: Yeah, so… Let me… 392 00:55:27.810 --> 00:55:32.869 STFC-RAL-CR03-RAL-R61-2.01: So, at the moment, on the top of my head, I'm not sure of the resolution. 393 00:55:32.990 --> 00:55:37.039 STFC-RAL-CR03-RAL-R61-2.01: Like, this… the voltages that we're looking at are, like, nano… 394 00:55:37.040 --> 00:55:38.310 Wonjong Chang: Volt Skele. 395 00:55:39.480 --> 00:55:43.249 STFC-RAL-CR03-RAL-R61-2.01: The resolution… I actually did have a plot of… 396 00:55:43.660 --> 00:55:46.549 Wonjong Chang: the model we have here. So, yeah, so… 397 00:55:47.270 --> 00:55:55.059 Wonjong Chang: In terms of line width, so this is the… the actual, change in… 398 00:55:55.230 --> 00:56:11.129 Wonjong Chang: resonance width that we're able to detect for the resolution of that change. So this is the model we have at the moment for cooling the squid down to 10 millikelvin, 1 millikelvin, and 0.1 millikelvin. So. 399 00:56:11.130 --> 00:56:13.709 STFC-RAL-CR03-RAL-R61-2.01: off the top of my head, I'm not sure exactly. 400 00:56:13.710 --> 00:56:15.640 Wonjong Chang: Actually, these temperatures closer to… 401 00:56:16.180 --> 00:56:23.080 Wonjong Chang: how cold we think we actually could get the squid. But you said you're talking about maybe, 402 00:56:23.300 --> 00:56:31.340 Wonjong Chang: at Optimum Field, about… The N to the minus 4 herts in… I'm with… 403 00:56:33.600 --> 00:56:37.609 Wonjong Chang: I'm not sure if… I'm not sure if that's a useful answer to your question. 404 00:56:37.780 --> 00:56:39.550 STFC-RAL-CR03-RAL-R61-2.01: If the new units are actually useful or not. 405 00:56:40.770 --> 00:56:45.790 Wonjong Chang: Okay. I'll… 406 00:56:46.170 --> 00:56:59.669 Wonjong Chang: I'll just try to, think about it. Secondly, I was a bit curious, like, is there any unique advantages of making a lot of the parts superconducting? 407 00:57:02.660 --> 00:57:03.660 Wonjong Chang: Yeah. 408 00:57:03.840 --> 00:57:09.200 Wonjong Chang: So, you need the wire to be superconducting, because you don't want it to… 409 00:57:16.660 --> 00:57:19.260 Wonjong Chang: And then, aside from that, the… 410 00:57:19.380 --> 00:57:24.589 Wonjong Chang: Well, yeah, you just want as little resistance as possible, to reduce the amount of 411 00:57:25.010 --> 00:57:26.130 Wonjong Chang: Heat in your system. 412 00:57:30.760 --> 00:57:32.829 Wonjong Chang: Okay, thank you very much. 413 00:57:35.930 --> 00:57:37.470 STFC-RAL-CR03-RAL-R61-2.01: Last call for questions. 414 00:57:38.530 --> 00:57:53.089 STFC-RAL-CR03-RAL-R61-2.01: Yes, sir. No, just because you didn't get a chance to show it in the main talk, but you had a slide on the earth shaggling. Just thought maybe you want to explain that a little bit, because I think it's quite interesting. Yes. So, this is some work done by a collaborator of ours, named Balashi, 415 00:57:53.890 --> 00:57:56.779 STFC-RAL-CR03-RAL-R61-2.01: And, Yuri Smirnoff, so… 416 00:57:57.520 --> 00:58:14.220 STFC-RAL-CR03-RAL-R61-2.01: The interesting thing is, in our field, for a long, long time, we've kind of been thinking about the star match sensitivities as exclusion plots of a minimum bound, and then everything above it is parameter space, so you're… you've ruled out. 417 00:58:14.840 --> 00:58:21.149 STFC-RAL-CR03-RAL-R61-2.01: But it turns out that, actually, because your experiments are on Earth. 418 00:58:21.490 --> 00:58:24.240 STFC-RAL-CR03-RAL-R61-2.01: When you get to a high enough… 419 00:58:24.370 --> 00:58:35.009 STFC-RAL-CR03-RAL-R61-2.01: interaction strength between dark matter and nucleons, then you actually get shadowing effects from the Earth itself and the atmosphere of the Earth, which means that 420 00:58:35.620 --> 00:58:40.939 STFC-RAL-CR03-RAL-R61-2.01: realistically, you know, it doesn't matter, it exists in the premise space, sort of up here. 421 00:58:41.090 --> 00:58:52.839 STFC-RAL-CR03-RAL-R61-2.01: that you still wouldn't see in the detector, because it would have interacted with the Earth before it ever actually reshooted. So they did some work on essentially taking our limits, and then putting these, 422 00:58:53.320 --> 00:58:56.950 STFC-RAL-CR03-RAL-R61-2.01: Put the limits on them as well. Which… 423 00:58:57.180 --> 00:58:59.970 STFC-RAL-CR03-RAL-R61-2.01: You know, it's… it'll be a lot of work to then, 424 00:59:00.200 --> 00:59:16.380 STFC-RAL-CR03-RAL-R61-2.01: go and sort of produce these limits for all of the experiments that have ever… that have ever produced a limit. But I think it's a… it's an interesting, really interesting result. That means there's a lot of parameter space in the world that we thought was excluded, but realistically, it probably isn't. 425 00:59:18.650 --> 00:59:25.849 STFC-RAL-CR03-RAL-R61-2.01: If you're not going down the night, you go into space. Exactly. That's definitely more thought. 426 00:59:26.230 --> 00:59:29.929 STFC-RAL-CR03-RAL-R61-2.01: Any additional questions? 427 00:59:31.980 --> 00:59:32.780 STFC-RAL-CR03-RAL-R61-2.01: Huh? 428 00:59:33.180 --> 00:59:34.350 STFC-RAL-CR03-RAL-R61-2.01: Are you on Zoom? 429 00:59:34.580 --> 00:59:36.930 STFC-RAL-CR03-RAL-R61-2.01: No? Okay, then let's… thanks, you guys. 430 00:59:42.370 --> 00:59:46.879 STFC-RAL-CR03-RAL-R61-2.01: So, we'll be heading for lunch, in the PPD corridor, let's say, entire time.