WEBVTT 00:00:00.000 --> 00:00:02.000 On the longevity and ecological studies of the CMS trim bermule detector. 00:00:02.000 --> 00:00:11.000 And I will just start the recording in one second. And I think we can go ahead. 00:00:11.000 --> 00:00:23.000 Okay. Hello. Hi, everyone. My name is colin um So today I was… I'm sorry, I just stopped sharing. 00:00:23.000 --> 00:00:34.000 Okay, sorry. Okay, so say I was hoping to give a talk on my contributions towards longevity and eco gas studies in the cathode strip chambers. 00:00:34.000 --> 00:00:46.000 You want to sector subsystem of the CMS experiment. So the cathode strip, there's more on this too, by the way, in my lab mate. Xiaowei will be giving a talk later in the day around 11. 00:00:46.000 --> 00:00:51.000 And she can explain more about the CMS experiment where these fit in. 00:00:51.000 --> 00:00:58.000 Mine is more of a methodological study on the actual CSC materials and such. 00:00:58.000 --> 00:01:08.000 So here I just want to briefly tell you about a Catholic strip chamber. They're a type of multi-wide proportional chamber Which means their gaseous chamber. 00:01:08.000 --> 00:01:16.000 There are 540 of them in the NCAP muon system. So it's quite integral to the muon system with the CMS experiment. 00:01:16.000 --> 00:01:25.000 Each chamber has six gas gap layers. In each layer, there's anode wires running perpendicular to cathode strips. 00:01:25.000 --> 00:01:30.000 And the ionization of the gas in the in these one of these gas gaps. 00:01:30.000 --> 00:01:38.000 Leads to loose electrons which are pulled towards the wires and the strips that are held at high voltage difference. 00:01:38.000 --> 00:01:49.000 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% CO2, and 10% CO4. 00:01:49.000 --> 00:02:00.000 And the main purpose of this study is to focus on this carbon tetrafluoride, which is very strong global warming potential and something we greatly like to reduce our dependency on. 00:02:00.000 --> 00:02:11.000 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. 00:02:11.000 --> 00:02:25.000 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 00:02:25.000 --> 00:02:44.000 The studies, these studies. So currently how CSCs are handling this is that they've implemented with the gas group here at CERN a recuperation system where they can take the exhausted gas and filter it and sort and recollect the carbon tetrafluoride and then feed it back through. 00:02:44.000 --> 00:02:52.000 So currently we're doing that with 40% fresh mixture and 60% of what we give back to the trajectory is we've created. 00:02:52.000 --> 00:02:56.000 So we'd like to see if we can further reduce this. 00:02:56.000 --> 00:03:07.000 And so I'll present that now. So one of the ways Xiaowei is also doing study with this, but one of the ways we can do this um to use smaller prototype css. 00:03:07.000 --> 00:03:16.000 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. 00:03:16.000 --> 00:03:29.000 But this smaller one is only 30 centimeters by 30 centimeters. It has just two gas cap layers And so it's kind of ideal for small fest laboratory tests of chamber performance and longevity. 00:03:29.000 --> 00:03:34.000 Integral since we're studying the integral gas, we have our own gas mixture. 00:03:34.000 --> 00:03:43.000 Which we can mix up to four different gas components. Currently, we're doing it with 40% argon, 55% CO2, and 5% CO4. 00:03:43.000 --> 00:03:48.000 But entirely recuperated. And so I'll talk about this a little bit more later. 00:03:48.000 --> 00:04:04.000 But uh 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 evaluate the performance. So here I show a small schematic of 00:04:04.000 --> 00:04:22.000 Six holes we've drilled into the top honeycomb layer of the chamber, which gives easy access for the for our radioactive sources. In particular, we irradiate at hole two and then we treat holes four and six as our control layers. 00:04:22.000 --> 00:04:34.000 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 three different gas mixtures. 00:04:34.000 --> 00:04:49.000 5%, 2%, and 0% CF4. They irradiated them up to 300 milliculums per centimeter, which was one and a half times the prediction of the high luminosity LHC radiation environment at the time. 00:04:49.000 --> 00:04:58.000 And evaluated the chamber performance. They saw no significant aging up to this particular accumulated charge in any of these three cases. 00:04:58.000 --> 00:05:05.000 But they later disassembled the chamber and sent off the wires for material analysis. 00:05:05.000 --> 00:05:24.000 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. So this presents kind of a risky situation Especially since they had done their study, the prediction has increased for the radiation environment of the CSCs. 00:05:24.000 --> 00:05:31.000 So 5% seems to be a good candidate for operations since we saw no significant carbon increase. 00:05:31.000 --> 00:05:40.000 And so we'd like to further investigate that. We'd like to focus on using entirely recuperated CO4 instead of fresh gas. 00:05:40.000 --> 00:05:46.000 And then also since the prediction has changed, we need to irradiate to a higher level. 00:05:46.000 --> 00:05:53.000 Of charge accumulated. So this is kind of the motivation for the study we've been doing currently with the mini CSC. 00:05:53.000 --> 00:06:05.000 And why we have the gas mixture I mentioned earlier. So to actually do the study, we used the gas mixture I told you. We leave the chamber on and irradiate it with a strong strontium-90 source. 00:06:05.000 --> 00:06:16.000 Specifically, it's 30 megabrel. And every week we take the source off the chamber and then perform a series of measurements to evaluate the health of the chamber. 00:06:16.000 --> 00:06:25.000 Since it's just one layer and small, we're not tracking individual muon tracks. We can just make kind of general measurements so we look at things like the dark grates and currents. 00:06:25.000 --> 00:06:36.000 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. 00:06:36.000 --> 00:06:42.000 In a chamber. So we want to monitor that that's not changing As we go on. 00:06:42.000 --> 00:06:56.000 As we go on. So two 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. 00:06:56.000 --> 00:07:03.000 So here on the right, I show an example charge spectrum we collect from a local 109 cadmium source. 00:07:03.000 --> 00:07:07.000 Which is just a gamma emitter and gives a very crisp and clean peak here. 00:07:07.000 --> 00:07:13.000 And we can monitor this peak position relative to the control holes I mentioned earlier. 00:07:13.000 --> 00:07:24.000 And monitor for any changes in this peak position. So this is one of the ones we do every week. But then, as I was mentioning, we also do the absolute gasping measurement. 00:07:24.000 --> 00:07:42.000 And the way we can do this is we can measure, we can place the source on a chamber and measure the current uh measure the current from a singular strip with a very sensitive ammeter, pico ammeter And then we can measure their current across a whole range of high voltages from zero up to 3,900 volts. 00:07:42.000 --> 00:07:48.000 We can also do this without source. And when we subtract the two, we isolate the current due to the source. 00:07:48.000 --> 00:08:00.000 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. 00:08:00.000 --> 00:08:13.000 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 was amplified. This is our gas gain. 00:08:13.000 --> 00:08:25.000 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 values. So besides this being a good value to look at. 00:08:25.000 --> 00:08:34.000 It's also important when we're doing the radiation that our chamber is operating in conditions that we are intended. 00:08:34.000 --> 00:08:41.000 So in particular. It should follow a clean exponential as the high voltage is raised. 00:08:41.000 --> 00:08:55.000 Then the gas gain should follow that well. And so we look in this high voltage region between the dashed lines here, and we fit an exponential to the gas gain here. 00:08:55.000 --> 00:08:58.000 Where we expect it to be well behaved and minimal space charge. 00:08:58.000 --> 00:09:04.000 And then we extrapolate this fit into higher voltage regions here. 00:09:04.000 --> 00:09:13.000 And then we look to see, to make sure that the chamber is, the gas gain is climbing similar or as expected with the fit. 00:09:13.000 --> 00:09:25.000 At too high of voltage, you can get space charge effects where the you get a buildup of positive slower moving positive ions that cause a effective dip in your gas gain. 00:09:25.000 --> 00:09:28.000 And that's not ideal. And so we looked for the onset of that. 00:09:28.000 --> 00:09:36.000 And we see that where we'd like to operate in the chamber at 3,600 volts, there's negligible space charge. So the chamber is behaving how we'd like. 00:09:36.000 --> 00:09:54.000 So this is. 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 explain too much how exactly we're describing the age. So the preferred metric is to describe the accumulated charge where we talk about the 00:09:54.000 --> 00:10:03.000 Current collected by the wires. And divided by the length of those wires experiencing that current. And this gives us a value in millicoulons per centimeter. 00:10:03.000 --> 00:10:09.000 Describing our chamber age. So, um. 00:10:09.000 --> 00:10:16.000 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. 00:10:16.000 --> 00:10:23.000 So that we would be able to accurately describe the aging of the chamber. 00:10:23.000 --> 00:10:38.000 So in order to do this, we needed to characterize the beam spot so we took the strontium 90 source and we placed it on top of the chamber Particularly the 30 megabecrol source Then I measured the current. 00:10:38.000 --> 00:10:44.000 At all 12 active strips. And then I divided that current by the strip width. 00:10:44.000 --> 00:10:48.000 To give a measure of the linear turn density at that strip. 00:10:48.000 --> 00:10:58.000 So that's what these plotted points are here. I then fit to it the sum of two Gaussians, one describing the peak and one describing the shoulder. 00:10:58.000 --> 00:11:02.000 So this full fit is here in the solid black line. 00:11:02.000 --> 00:11:14.000 And this describes the linear current density in one direction. But because I'm measuring the current in 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. 00:11:14.000 --> 00:11:28.000 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've got here. And then we can see exactly where the current is being delivered relative to the center of the radioactive source. 00:11:28.000 --> 00:11:35.000 In these contours, I then show potential bean spot definitions that we were considering. So the full width at half max and the two and three sigma regions. 00:11:35.000 --> 00:11:42.000 Where sigma comes from the standard deviation of this peak component Gaussian in dash blue here. 00:11:42.000 --> 00:11:48.000 In this dash line, I show a cross section to better show the what the bean sprout looks like. 00:11:48.000 --> 00:11:55.000 And what we decided on was that the two sigma region described the bulk of the current as much as reasonable of the shoulders. 00:11:55.000 --> 00:12:05.000 So given this information, we can then say that for L, a full 24 hours of irradiating, we can get 2.31 millicool per centimeter. 00:12:05.000 --> 00:12:08.000 And then since we've begun the study, we've actually upgraded to another source. 00:12:08.000 --> 00:12:14.000 That's 50 megabit curl and we can now irradiate up to 3.77 milliliters per centimeter each day. 00:12:14.000 --> 00:12:24.000 So, so far we've accumulated up to 177 millicolons per centimeter And we've been monitoring, as I said, the dark rates in those of gas gain as we go on. 00:12:24.000 --> 00:12:43.000 So ideally. So, so far we've established a good accelerating aging methodology, including the bean spread characterization, and we've been monitoring our gas gain and performance metrics as we go ahead. We're steadily increasing towards high lunarity LHC conditions and we're hoping that 00:12:43.000 --> 00:12:50.000 We can give recommendations soon about how low we can go in terms of this potent greenhouse gas carbon nitric fluoride. 00:12:50.000 --> 00:12:58.000 So thank you for your attention. And if you have any questions, I'd be happy to answer them. 00:12:58.000 --> 00:13:02.000 Thank you, Glenn, for the great talk. I already see a hand up, Dwayne. 00:13:02.000 --> 00:13:07.000 You can go ahead. 00:13:07.000 --> 00:13:17.000 Hi, Colin, this is a very interesting talk. You've mentioned that you have 00:13:17.000 --> 00:13:29.000 Yeah, so you mentioned the CF4 is the gas that you're aiming for to try to reduce But you also have 50% carbon dioxide as well. 00:13:29.000 --> 00:13:43.000 Are you looking at anything in terms You never actually explained why the carbon dioxide is required there. Is that a gas that's able to be replaced as well? Or are you just looking at CFO for now? 00:13:43.000 --> 00:13:57.000 Yes, so good question. So the CO2 is incorporated because it acts as a quenching molecule. So it helps reduce dead time and prevent excessive signals. 00:13:57.000 --> 00:14:06.000 We have not looked into it as right now, but we're more concerned right now because CF4 is uh it's like almost 2000 times or maybe more, I think. 00:14:06.000 --> 00:14:19.000 As potent as CO2. So we were hoping to tackle the worst uh guests first. 00:14:19.000 --> 00:14:30.000 Thank you, Colin. Yes, I think actually with the CFO, the global learning potential should be around seven times more CO2. So it's definitely the first one to tackle. 00:14:30.000 --> 00:14:37.000 I was just checking if there are any more questions. Otherwise, I would also have one. 00:14:37.000 --> 00:14:49.000 I was wondering if you knew like what would be the reductions in emissions Over the 5% mixture and the one you're currently using. 00:14:49.000 --> 00:14:58.000 Okay, so I don't have phone numbers, sorry, but we can recuperate with an efficiency of 70%. 00:14:58.000 --> 00:15:10.000 So we would Well, first of all, we'd be using half as much total. And then if we went to fully recuperated, we would 00:15:10.000 --> 00:15:18.000 Whatever's a seven percent so maybe Sorry, I'm thinking of my simple math right now. 00:15:18.000 --> 00:15:39.000 And with the efficiency sorry it's a second question that i had as well uh 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? 00:15:39.000 --> 00:15:48.000 Right. So it used to be entirely fresh. So we're trying to work our way towards recucrated. They are concerned about impurities and particularly if any silicon gets in. 00:15:48.000 --> 00:16:02.000 Also, since it's not the most They are worried about impurities that might alter the gas cane, like if more nitrogen gets in there, then that's another noble gas that may act as an active medium and So it might not be behaving how we expect. 00:16:02.000 --> 00:16:16.000 So they're kind of waiting for us to do these studies to make sure that everything is behaving well. And the recuperative gas we are using is collected from the CMS experiment. So we were hoping to give them a good answer about 00:16:16.000 --> 00:16:25.000 If it's as if it's pure enough to uh operated chamber as we expect. 00:16:25.000 --> 00:16:34.000 Okay, thank you. I will just have a quick look in the chat. I'm not seeing any further question. 00:16:34.000 --> 00:16:48.000 You're in the So then I would say thank you so much, Colin, for the talk. It was really nice to see the efforts on the CSEs in the cses And I think we can… 00:16:48.000 --> 00:16:51.000 And I think we can… Dig. 00:16:51.000 --> 00:16:53.000 Jacob. I'm mispronouncing. 00:16:53.000 --> 00:16:58.000 Okay.