WEBVTT 1 00:00:00.000 --> 00:00:05.839 Stefania Juks: Chamber music detector, and I will just start the recording in one second. 2 00:00:06.340 --> 00:00:09.130 Stefania Juks: and I think we can go ahead. 3 00:00:11.390 --> 00:00:17.630 collinarbour: Hello, Hi, everyone! My name is Colin. So today I was, oh. 4 00:00:17.890 --> 00:00:19.360 collinarbour: I'm sorry. I just stopped sharing. 5 00:00:23.620 --> 00:00:33.560 collinarbour: Okay, sorry. Okay. So say, I was hoping to give a talk on my contributions towards the longevity and ecocast studies in the Catholic chambers. 6 00:00:34.042 --> 00:00:37.569 collinarbour: You want to check your subsystem of the Cms experiment. 7 00:00:38.282 --> 00:00:50.449 collinarbour: So the cathode strip. There's more on this, too. By the way, in my lab maid, Xiaowei will be giving a talk later in the day at around 11, and she can explain more about the seamless experiment where these fit in. But 8 00:00:50.780 --> 00:01:04.799 collinarbour: mine is more of a methodological study on the actual Csc materials and such. So here, I just want to briefly tell you that about a catalyst strip chamber. They're a type of multiwire proportional chamber. 9 00:01:05.424 --> 00:01:15.800 collinarbour: Which means they're a gaseous chamber. There are 540 of them in the Ncat Muon system, so it's quite integral to the Muon system of the Cms. Experiment. 10 00:01:15.990 --> 00:01:24.179 collinarbour: Each chamber has 6 gas gap layers in each layer. There's anode wires running perpendicular to cathode strips. 11 00:01:25.230 --> 00:01:30.209 collinarbour: and the ionization of the gas in the in these one of these gas gaps 12 00:01:30.360 --> 00:01:38.029 collinarbour: leads to loose electrons which are pulled towards the wires and the strips that are held at high voltage difference. 13 00:01:38.560 --> 00:01:59.339 collinarbour: So since we're operating with gas, we are releasing a bunch of gas into the atmosphere right now, it's composed of 40% argon, 50% Co, 2 and 10% Co 4. And the main purpose of this study is to focus on this carbon tetrafluoride, which has a very strong global warming potential and something we'd greatly like to reduce our dependency on. 14 00:02:00.130 --> 00:02:27.209 collinarbour: It's included in the chambers because it helps prevent aging. So it helps etch away any silicon deposits. And we found also prevent carbon polymerization or buildup of carbon deposits as well. So it's really important in terms of making sure the chamber survives and behaves well throughout the duration of our experiments, so we need to find either an alternative or figure out how we can reduce it. And this is kind of the purpose of the studies these studies. 15 00:02:28.061 --> 00:02:33.299 collinarbour: So currently, how Cfcs are handling this is that they've implemented with the gas group here at Cern 16 00:02:33.530 --> 00:02:37.150 collinarbour: a recuperation system where they can take the exhausted gas and 17 00:02:37.410 --> 00:02:44.069 collinarbour: filter it and sort and recollect the carbon tetrafluoride and then feed it back through. 18 00:02:44.340 --> 00:02:51.309 collinarbour: So currently, we're doing that with 40% fresh mixture and 60% of what we give back to the detectors we created. 19 00:02:52.435 --> 00:02:55.790 collinarbour: So we'd like to see if we can further reduce this. 20 00:02:55.990 --> 00:02:58.020 collinarbour: And so I'll present that now. 21 00:02:58.568 --> 00:03:04.771 collinarbour: So in one of the ways shall, we is also doing study with this. But one of the ways we can do. This is 22 00:03:05.250 --> 00:03:24.939 collinarbour: to use smaller prototype Cscs, which we call Mini Cscs. And so I show an example. Chamber up here in the top right. They're made of the exact same materials and use the exact same electronics as the real chambers. But this smaller one is only 30 cm by 30 cm. It has just 2 gas cap layers. And so it's kind of ideal for small fest 23 00:03:25.290 --> 00:03:28.300 collinarbour: laboratory tests of chamber performance and longevity 24 00:03:28.720 --> 00:03:36.840 collinarbour: integral. Since we're studying the gas. We have our own gas mixture which we can mix up to 4 different gas components. 25 00:03:36.950 --> 00:03:42.829 collinarbour: Currently, we're doing it with 40%. Argon 55%, co, 2 and 5% Co 4, 26 00:03:43.290 --> 00:03:47.519 collinarbour: but entirely recuperated. And so I'll talk about this a little bit more later. 27 00:03:48.383 --> 00:03:49.649 collinarbour: But yeah. 28 00:03:49.830 --> 00:04:00.269 collinarbour: to actually evaluate the Chamber. We need to simulate the radiation environment of the experiment. So we use local radiation sources to simulate that aging. And then we can also use it to 29 00:04:01.160 --> 00:04:10.334 collinarbour: evaluate the performance. So here I show a solid small schematic of 6 holes. We've drilled into the top honeycomb layer of the chamber, which gives easy access for the 30 00:04:11.700 --> 00:04:13.229 collinarbour: for our radioactive sources. 31 00:04:13.710 --> 00:04:18.449 collinarbour: In particular, we we irradiate at Hole 2, and then we treat holes 4 and 6 32 00:04:18.560 --> 00:04:20.179 collinarbour: as our control layers. 33 00:04:22.029 --> 00:04:34.420 collinarbour: So why are we using this particular gas mixture? Well, previously people have used these prototypes to also study this kind of problem. And most recently a study was done where they evaluated 3 different gas mixtures. 34 00:04:34.670 --> 00:04:37.509 collinarbour: 5%, 2% and 0%. Cf, 4, 35 00:04:37.780 --> 00:04:47.920 collinarbour: they irradiated them up to 300 milligolms per centimeter, which was one and a half times the prediction of the high luminosity Lhc. Radiation environment at the time 36 00:04:48.740 --> 00:05:02.600 collinarbour: and evaluated chamber performance. They saw no significant aging up to that this particular accumulated charge in any of these 3 cases, but they later disassembled the chamber and sent off the wires. 37 00:05:03.297 --> 00:05:04.790 collinarbour: For material analysis. 38 00:05:05.080 --> 00:05:12.099 collinarbour: And it was found that in the 0% and 2% cases there was a significant increase in the amount of carbon deposited on the wires. 39 00:05:12.795 --> 00:05:15.640 collinarbour: So this presents kind of a risky situation. 40 00:05:15.850 --> 00:05:23.399 collinarbour: especially since they have done their study. The prediction has increased for the radiation environment of the Cses. 41 00:05:24.455 --> 00:05:30.640 collinarbour: So 5% seems to be a good candidate for operation, since we saw no significant carbon increase. 42 00:05:31.240 --> 00:05:39.779 collinarbour: And so we'd like to further investigate that we'd like to focus on using entirely recuperated Co. 4 instead of fresh gas. 43 00:05:40.400 --> 00:05:45.809 collinarbour: And then, also, since the prediction has changed, we need to irradiate to a higher level 44 00:05:46.130 --> 00:05:52.169 collinarbour: of charge accumulated. So this is kind of the motivation for the study we've been doing currently with the Mini Cse. 45 00:05:53.060 --> 00:05:55.639 collinarbour: and why we have the gas mixture I mentioned earlier. 46 00:05:56.190 --> 00:06:05.450 collinarbour: So to actually do the study, we use the gas mixture. I told you we leave the chamber on and irradiate it with a strong strontium 90 source. 47 00:06:05.550 --> 00:06:08.580 collinarbour: Specifically, it's a 30 mega macro. 48 00:06:09.680 --> 00:06:15.569 collinarbour: and every week we take the source off the Chamber and then perform a series of measurements to evaluate the health of the chamber. 49 00:06:15.770 --> 00:06:39.539 collinarbour: since it's just one layer and small we don't get. We're not tracking individual muon tracks. We can just make kind of general measurements. So we look at things like the dark rates and dark currents, to make sure it's not becoming more or less noisy. And then, in particular. What we can study well is the gas gain of a chamber which is very important for interpreting and collecting the data in a chamber. So we want to monitor that that's not changing 50 00:06:39.780 --> 00:06:41.560 collinarbour: as we go on as good 51 00:06:41.740 --> 00:07:07.299 collinarbour: as we go on. So 2 ways we can do this is we can measure the absolute gas gain. But that's kind of sensitive to pressure and temperature. So another, while it's still important to know another good way is to also look at the Absolute. I'm sorry the relative gas gain. So here on the right I show an example. Charge spectrum. We collect from a local 109 cadmium source, which is just a gamma emitter, and it gives a very crisp and clean peak here. 52 00:07:07.540 --> 00:07:12.459 collinarbour: and we can monitor this peak position relative to the control holes I mentioned earlier 53 00:07:13.540 --> 00:07:16.940 collinarbour: and monitor for any change in this peak position. 54 00:07:17.220 --> 00:07:23.810 collinarbour: So this is one of the ones we do every week. But then, as I mentioned, we also do, the absolute gas gaining measurement. 55 00:07:23.940 --> 00:07:27.629 collinarbour: And the way we can do this is, we can measure. We can place the source 56 00:07:28.430 --> 00:07:31.730 collinarbour: on a chamber, and measure the current 57 00:07:32.170 --> 00:07:35.929 collinarbour: from a singular strip with a very sensitive ammeter picoameter. 58 00:07:36.440 --> 00:07:41.740 collinarbour: and then we can measure that current across a whole range of high voltages from 0 up to 3,900 volts. 59 00:07:42.020 --> 00:07:47.680 collinarbour: We can also do this without source, and when we subtract the 2, we isolate the current due to the source. 60 00:07:48.813 --> 00:07:59.809 collinarbour: Then we look in the low voltage range here, around between 0 and 500 volts, and this current is due to the electric field being strong enough to collect the ionized electrons. 61 00:07:59.930 --> 00:08:18.589 collinarbour: but not enough to cause an amplification in that signal. So this is called our primary ionization plateau, and if we divide all our points by the average current here, we get a factor for how much that signal is amplified. This is our gas gain. So in this bottom plot here you can see a plot of what the gas gain looks like across a range of these higher voltage. 62 00:08:19.539 --> 00:08:20.089 collinarbour: Values 63 00:08:21.383 --> 00:08:30.106 collinarbour: so besides being a good value to look at it's also important when we're doing the radiation that our chambers operating and 64 00:08:30.880 --> 00:08:34.240 collinarbour: conditions that we are intended. 65 00:08:34.953 --> 00:08:44.160 collinarbour: So in particular it should follow a clean exponential. As the voltage high voltage is raised, then the gas gain should follow that well. 66 00:08:44.400 --> 00:08:58.259 collinarbour: and so we look in this mid to high this high voltage region between the dashed lines here, and we fit an exponential to the gas gain here, where we expect it to be well behaved and minimal space charge. 67 00:08:58.440 --> 00:09:03.580 collinarbour: and then we extrapolate this fit into higher voltage regions here 68 00:09:04.032 --> 00:09:11.230 collinarbour: and then we we look to see, to make sure that the chamber is the gas gain is climbing similar 69 00:09:11.430 --> 00:09:13.179 collinarbour: or as expected, with this thing 70 00:09:13.914 --> 00:09:19.120 collinarbour: at too high of a voltage. You can get space charge effects where? The you get a buildup 71 00:09:19.430 --> 00:09:27.949 collinarbour: of positive, slower, moving, positive ions that cause a effective dip in your cascade, and that's not ideal. And so we looked for the onset of that. 72 00:09:28.100 --> 00:09:34.959 collinarbour: And we see that where we'd like to operate the chamber at 3,600 volts. There's negligible space charge. So it's the chamber is behaving how we'd like 73 00:09:36.272 --> 00:09:37.299 collinarbour: so this is 74 00:09:38.080 --> 00:10:05.630 collinarbour: so. This is some cool, good examples of how we're performing the monitoring, and then our intent for aging it. But I guess I haven't really explained too much how exactly we're describing the age. So the preferred metric is to describe the accumulated charge where we talk about the current collected by the wires and divided by the length of those wires experiencing that current, and this gives us a value in milligolms per centimeter describing our chamber age. 75 00:10:06.580 --> 00:10:07.190 collinarbour: So 76 00:10:08.830 --> 00:10:18.238 collinarbour: we'd like to keep track of this, but it's not trivial to do that when we have a local radioactive source. So I spent a lot of effort trying to characterize this so that we would be able to 77 00:10:18.840 --> 00:10:23.109 collinarbour: accurately describe the aging of the chamber. 78 00:10:23.652 --> 00:10:28.020 collinarbour: So in order to do this, we needed to characterize the beam spot. So 79 00:10:28.670 --> 00:10:32.600 collinarbour: we took the strong team, 90 source, and we placed it on top of the chamber. 80 00:10:33.406 --> 00:10:35.290 collinarbour: Particularly the 30 megabital source. 81 00:10:35.980 --> 00:10:40.320 collinarbour: Then we took. I measured the current at all 12 active strips. 82 00:10:40.850 --> 00:10:44.039 collinarbour: and then I divided that current by the strip width 83 00:10:44.280 --> 00:10:48.100 collinarbour: to give a measure of the linear turn density at that strip. 84 00:10:48.390 --> 00:10:49.830 collinarbour: So that's what these 85 00:10:51.200 --> 00:11:04.630 collinarbour: plotted points are here. I then fit to it the sum of 2 Gaussians, one describing the peak and one describing the shoulder. So this full fit is here in the solid black line, and this describes the linear current density in one direction. 86 00:11:05.050 --> 00:11:22.039 collinarbour: But because I'm measuring the current of a strip, it's taking the current from the whole length of the strip. So in reality, this is an integral over the length of the strip here, and using this information and the values I get from the fit. I can then reconstruct the full 2D current density distribution which I plot here. 87 00:11:22.340 --> 00:11:27.720 collinarbour: and then we can see exactly where the current is being delivered relative to the center of the radioactive source. 88 00:11:27.860 --> 00:11:38.210 collinarbour: In these contours I then show potential beanspot definitions that we were considering. So the full width half Max and the 2 and 3 sigma regions where Sigma comes from the standard deviation of this peak. 89 00:11:38.939 --> 00:11:41.279 collinarbour: Component Gaussian in dash blue. Here 90 00:11:41.690 --> 00:11:45.459 collinarbour: in this dashed line I show a cross section to better show the 91 00:11:45.770 --> 00:11:47.479 collinarbour: what the bean spot looks like. 92 00:11:47.840 --> 00:11:55.230 collinarbour: and what we decided on was that the 2 Sigma region described the bulk of the current as much as as reasonable of the shoulders. 93 00:11:55.550 --> 00:12:04.340 collinarbour: So, given this information, we can then say that for LA. Full 24 h of irradiating. We can get 2.3 1 millicols per centimeter. 94 00:12:04.650 --> 00:12:13.179 collinarbour: And then, since we've begun this study, we've actually upgraded to another source. That's 50 megabit, and we can now irradiate up to 3.7 7 molecules per centimeter each day. 95 00:12:14.170 --> 00:12:19.170 collinarbour: So so far, we've accumulated up to 107 milligrams per centimeter. 96 00:12:19.400 --> 00:12:23.499 collinarbour: and we've been monitoring, as I said, the dark rates and osive gas gain as we go on 97 00:12:24.530 --> 00:12:24.920 collinarbour: so 98 00:12:25.750 --> 00:12:35.679 collinarbour: ideally. So so far we've established a good accelerating, aging methodology, including the bean spread characterization. And we've been monitoring 99 00:12:36.160 --> 00:12:42.950 collinarbour: our gas gain and performance metrics as we go ahead. We're steadily increasing towards high conditions, and we're hoping that 100 00:12:43.100 --> 00:12:49.619 collinarbour: we can give recommendations soon about how low we can go in terms of this potent greenhouse, gas, carbon dirt fluoride. 101 00:12:49.970 --> 00:12:55.189 collinarbour: So thank you for your attention, and if you have any questions I'd be happy to answer them. 102 00:12:57.900 --> 00:12:59.560 Stefania Juks: Thank you, Colin, for the great talk 103 00:12:59.730 --> 00:13:03.390 Stefania Juks: I already see a hand up. Duane can go ahead. 104 00:13:07.130 --> 00:13:14.792 Dwayne Spiteri: Hi Colin, this is very interesting talk. You've mentioned that you have 105 00:13:18.740 --> 00:13:29.527 Dwayne Spiteri: yeah. So you mentioned the cf, 4 is the gas that you're aiming for to try to reduce. But you also have 50% carbon dioxide as well. 106 00:13:30.100 --> 00:13:41.169 Dwayne Spiteri: Are you looking at anything in terms is you never actually explained why the carbon dioxide is required there? And is that the gas is able to be replaced as well? Or are you just looking at. Cf. 4 for now. 107 00:13:42.800 --> 00:13:52.140 collinarbour: Yes, so good. Question. So the Co. 2 is incorporated because it acts as a quenching molecule, so it prevents. It helps reduce dead time and prevent 108 00:13:52.300 --> 00:13:54.410 collinarbour: excessive signals. 109 00:13:56.140 --> 00:13:57.030 collinarbour: So 110 00:13:57.310 --> 00:14:10.509 collinarbour: we have not looked into it as right now. We're more concerned right now, because cf, 4 is it's like almost 2,000 times, or maybe more, I think, as potent as Co. 2. So we were hoping to tackle the worst 111 00:14:10.810 --> 00:14:12.250 collinarbour: gas first.st 112 00:14:19.150 --> 00:14:29.470 Stefania Juks: Thank you, Colin. Yes, I think actually, with the Cfo, the global warning potential should be around 7 times more Co. 2. So it's definitely the 1st one to tackle. 113 00:14:30.926 --> 00:14:46.720 Stefania Juks: I was just checking. If there are any more questions, otherwise I would also have one. I was wondering if you knew, like, what would be the the reductions in emissions over the 5% mixture. And the one you're currently using. 114 00:14:49.903 --> 00:14:58.110 collinarbour: Okay, so I don't have full numbers. Sorry but we can. We can recuperate with an efficiency of 70%. 115 00:14:58.892 --> 00:15:00.490 collinarbour: So we would. 116 00:15:02.230 --> 00:15:08.119 collinarbour: Well, 1st of all, we'd be using half as much total and then if we went to fully recuperated we would. 117 00:15:10.280 --> 00:15:14.860 collinarbour: Whatever's a 7%. So maybe 118 00:15:16.230 --> 00:15:18.250 collinarbour: sorry. I'm thinking my simple math right now. 119 00:15:18.250 --> 00:15:18.650 Stefania Juks: That is. 120 00:15:19.200 --> 00:15:38.479 Stefania Juks: And with this, with the efficiency, sorry, it's a second question that I had as well. Why are you using 40% of fresh one at the moment, like, what are the are you concerned about impurities, or are there any other causes? Why, you're keeping this fresh amount of gas? You're still injecting. 121 00:15:39.880 --> 00:15:57.030 collinarbour: Right. So it used to be entirely fresh. So we're trying to work our way towards recuperated. They are concerned about impurities in particular. If any silicon gets in also, since it's not the most they are worried about impurities that might alter the gas gain like if more nitrogen gets in there, then that's another noble gas that may 122 00:15:57.460 --> 00:15:59.670 collinarbour: act as an active medium. And and 123 00:16:00.350 --> 00:16:06.860 collinarbour: so it might, not behaving how we expect. So they're kind of waiting for us to do these studies to make sure that everything 124 00:16:07.703 --> 00:16:12.989 collinarbour: is behaving well, and and the recruiting guests we are using is collected from the C. The 125 00:16:13.120 --> 00:16:17.789 collinarbour: the Cms experiment. So we're hoping to give them a good answer about. If it's 126 00:16:18.800 --> 00:16:23.490 collinarbour: as if it's pure enough to operated chamber, as we expect. 127 00:16:25.180 --> 00:16:26.560 Stefania Juks: Okay, thank you. 128 00:16:28.080 --> 00:16:35.770 Stefania Juks: I will just have a quick look in the chat. I'm not seeing any further question, either in the 129 00:16:37.010 --> 00:16:37.980 Stefania Juks: in the group. 130 00:16:38.710 --> 00:16:46.010 Jie Gao: So then I would say, Thank you so much, calling for the talk. It was really nice to see the efforts on the Css. Any Css. 131 00:16:47.170 --> 00:16:47.890 Stefania Juks: And I think. 132 00:16:48.815 --> 00:16:51.589 Jie Gao: Think we can. 133 00:16:53.410 --> 00:16:53.980 Stefania Juks: Mister, now. 134 00:16:54.595 --> 00:16:55.210 Jie Gao: It.