 Rhaid i fi, wrth gwrs, rwy'n chweithio ar ystod yn 10b. Yn ymwneud, Chris Tale. Rwy'n gweithio ymlaen chi'n mynd i fynd i'n cyrraedd, ac rwy'n meddwl am y cyflaen dweud yma. Fel fan yw ymlaen i chi. Rhaid i fi, rwy'n gweithio ar ystod. Mae hwn yn fawr i chi'n gweld i chi'n gweithio. I'm going to be talking about Geico-counters, as you're probably guessed by now, specifically some reasons why you might want to earn a Geico-counters review of your own, how easy it can be to build one for yourself for not very much money, and my specific reasons for building mine. I'm also going to delve a little bit into music physics, which is one of many subjects about which I'm totally unqualified. So, if you're a real physicist in the audience, and I go too far off the mark, then feel free to wave at me and tell me what's on the mess I'm making with it. Equally, if you're, ah, I see we have a physicist. If you're confused about what I'm saying, then let me know and I'll try and make it clear. So, some of you may recognise this. This is the sort of cliché version of radioactivity. It's green and it glows. And this mostly dates to the early days of the discovery of radioactivity, specifically radium, which was one of the first radioactive elements to be isolated. And there was what amounted to a fad for radium. It was used for all kinds of dodgy things. And one of the things that it was used for was it was mixed with zinc sulfide, and incorporated into paint and used to label up dials and things for watches. And it became lodged in the public imagination that it was green and glowy. The reason why it was glowy was because the radiation stimulated phosphorescence in the zinc sulfide. And that made it glow. Having said that, there are actually some elements, radioactive elements, which do glow. Actinium is one of them. If you have a sample of actinium, it will glow blue. But again, it's not actually the radioactivity that's doing that. It's ionising the air around it. So, if you had your actinium in a vacuum, then you wouldn't be able to see anything. Which is why you need a guic counter. And this is one that I built, which I've actually bought with me. So I'll give you a demo a little later, if I can persuade it to work. So I promise some reasons why you might want to own one. This is the sort of radioactivity that you might call background that you're exposed to every day. And as you can see, about 85% of that is natural. Only about 15% is down to things like x-rays. And a practically negligible amount is down to fallout. Most of these natural radioactivity is down to three elements. Which is uranium, 238, thorium, which is 232. And potassium 40, which is the radioactive isotope of potassium. And as you can see, about half of the natural exposure is down to radon gas. Which wells up out of the ground. So at this point, I'll stop talking for a minute. And you can have a little listen to my counterpicking. Hopefully picking up the background radiation here at Easter. I think the circuitry is going to interfere with the microfeters. So you're not going to hear it ticking. But I don't know if you can see that. It's counting the number of counts per minute at the moment. And currently we're sitting at about 24. Which is towards the upper end of what you normally expect. It's between about 5 and 25 normally. So I'll leave that going. And this is where the radon comes from. It's decay products of uranium 238. Those three radioactive elements that I mentioned are particularly important. Because they happen to have half lives. Which are comparable with the age of the earth. Which means that a large proportion of it that was incorporated in the earth when it was formed is still around. And this is what they call the decay chain for uranium 238. It looks more like it decays their case actually. One of the products of this is radon 222. Which can be quite dangerous in some parts of the world. I said that I come up with reasons why you might want to own a Geiger counter. I have to admit that my Geiger counter is not the best thing for detecting radon. Because it won't pick up alpha particles. And radon is now for emitter. But you can see from this chain that some of the products of radon. When the radon decays it produces elements which emit beta particles. And it will pick up beta so you should be able to detect it. That's not very interesting. This is actually a radon map that was produced by the government. And it shows parts of the country where you're more likely to be at risk of exposure to radon. It tends to pool in low-lying areas. So if you've got a basement in your house and you live in one of these areas. Then you probably need a radon detector to be installed. You'd see that Cornwall is very dodgy when it comes to radon. There's a lot of areas where it's a risk. And in fact Cornwall is the one county in England and Wales. Where they're not allowed to build new tear actors. Because the background radiation is all ready enough that you'd exceed your recommended annual dosage. So they have to keep away. And as it happens you probably spot it. This is a zoom-in on Isner. And we're in a radiation black spot. Or a radiation brown spot I should say. Because the modern hills are very close. And they've got a lot of granites in them. The uranium decays and formed radons. So this is one of the areas where you might have to watch out. It's probably the thing I tend to well learn today, didn't it? This is another reason why you might want to have a guide to counter. If you have fancy new kitchen and it's got granite work tops. Then some of the granite that's used for work tops can actually contain a lot of uranium. People have tested a lot of them. And about 5% of them contain enough uranium to actually pose a hazard to health if you leave it around for long enough. So watch out. And these are small railway sleepers. And one of my friends at Melkyn has made a space. Gives a wave of purple. He's asked if he can borrow my guide to counter because he's got some of these. And he's heard that you can, if you get them from Eastern Europe, then some of them might actually be radioactive. So he'd like to test them before he hasn't hanging around for too long. And bananas, famously radioactive. You may or may not have heard that. It is true and it's because they've got quite high levels of potassium in them. But effectively, you're not going to be able to detect it. I have actually tested a banana with my guide to counter. And I can tell you I haven't been able to find a statistically significant difference between background and banana. So it definitely didn't go bananas. Having said that bananas are high in potassium, so are you the average human being for about 140 grams of potassium. And of that, about 0.01%, I think, is actually potassium 40, which is the radioactive form of it. But that's enough to produce quite a lot of radiation. And at this point I was going to demo it again, but as I say, my guide to counter might prefer and don't like each other very much. So I'll just wait this at you. I might recognise this. This is low sodium salt. And it's about 50% potassium chloride. And of the potassium chloride, about half of that is by weight is potassium. So there's about 90 grams of potassium in this canister. And my guide to counter can absolutely detect the radiation from this. It's something like quadruples of the ray over background if you've got this close to the GM tube. So you can buy stuff in the supermarket, which is pretty radioactive, really. But you probably won't use very much of the time, so it's not going to be a risk. And I've also got some rather more radioactive samples. It completely has it in the morning. This is the guts from a smoke detector. And you can see that there's a little sample of Amaryssian 241, buried at the base of this thing. And that's emitting a constant stream of lava particles, which ionise the air in the smoke detector. And this can definitely pick that up. If I apply it to the back there, I would say the counts are bound double. It's gone up to about a bit more double, 50, 60. No, it's still climbing. 120. 120 counts, something like that. So I'll pop it back in this little case. It's not detecting the alpha particles in this case, but there is some secondary radiation which it picks up. If I had an alpha detector, then it would be going berserk. This is something else which you might find in your loft. If your parents were into counting, these are gaspanthals, and they contain a lot of thorium. So I'll apply it to the back. And it's gone nuts. It's climbing up 200, 300, 400 counts per minute. These things are pretty radioactive, which is why you can't buy them anymore. They actually pose a risk to people in factories that manufacture themselves. I think that's why they've stopped making them. It's primarily a litre. A litre in itre, that's what it's picking up here. So we're up to 1200 counts per minute. So I'll close it up again. Now I happen to have those things lying around, but you can definitely take it too far. This is a book about a guy that you may have heard of. His name was David Hartman. In 1994, he was a boy scout in America, and he decided for one of his merry badges, he was going to build a fast-breeding nuclear reactor, and he tried to do it in his mum's potting shed. He came alarmingly close, because somehow the various radioactive sources, he bought up hundreds of old smoke detectors and thousands of thorium gaspanthals, and he rented them all down. He was trying to build some kind of breather, but whatever he did, he managed to affect the neighbourhoods to the point where he could detect the radiation from about four houses away, and he lived in a wealthy neighbourhood. He was declared a sort of nuclear hazard zone by the government, and they came and dug up most of his months' garlic and carted it off to a nuclear waste dump. So, have I... Yes, I've gone past a couple of them. So, this is the reason why I built my Geiger counter. This is a PET scanner, specifically it's a PET CT scanner, and PET stands for Positron Emission Tomography. Positrons are basically anti-electrons, so these are the anti-particles I promised in the title of the talk, and as you may know, anti-matter and anti-particles do not like non-matter at all, and when a Positron is created, as soon as it comes into contact with an electron, it's annihilated rather violently and it generates radiation. She's got what the scanner picks up. Nowadays they tend to be combined with a CT scanner, which provides a detailed image of your body, and then the PET part of it will pick up the food's interest, which in my case was prostate cancer. I was diagnosed last year, early 2017, and they operated on it, but unfortunately the cancer returned, so they decided they were going to give me one of these scans. And about a week before the scan, I decided it would be interesting to have a look-see and find out just how radioactive they were going to make me. Fortunately, this is a decay curve for the element that they use, which is fluorine-NT, and as you can see from the scale at the bottom, it's a bit jumpy on my laptop on there, go back, and as you can see from the scale at the bottom, in hours, from the time that you actually get injected with the stuff, within 18 hours, it's pretty much undetectable again. But the syrins that they use is slightly alarming. They don't inject it directly like that, they put it into a cannula, but they do inject it and then run away very fast. What they specifically injected into me was an organic compound called colyn, colyn happens to be taken up quite strongly by the prostate cancer, which means that you can highlight it quite precisely. One of the problems about that is that the process that creates fluorine-NT will destroy organic molecules it's made in a cyclotron. So you have to manufacture the fluorine-NT, then label your colyn molecule and then rush it to the patient within about an hour, otherwise it's useless. So it tends to get queried around the country from your local site cyclotron to the hospital. And I'm skipping pages again. There we go. So this is the actual process that goes on inside the pet scanner. It's rather clever. They detect the positron emission and annihilation event. It creates gamma rays which actually travel in opposite directions. So they've got this circle of detectors around it and it will then only register gamma rays that emerge simultaneously in opposite directions and that generates your emission. So this is the council that I came up with, which again my friends will recognise, because, fortuitously, when I was irradiated, it happened to be one of the meeting days for the makerspace. So immediately after my scan, I rushed over to the makerspace and irradiated everybody there. So this was sitting at the edge. Jim, you interviewed this, didn't you? It was sitting at the edge of the makerspace and I got somebody to say, I'm forming this, starting walking towards it. Another time I got within about three metres. It was going nuts. So that was quite exciting. This is the circuit board inside it and obviously the most interesting thing about it is that nice big, properly GM tube. I'm going to be on the tube at the top. The reason why it looks kind of old is because it's ex-Soviet Russia. The various components of the former USSR are selling these things off in the thousands. They're very cheap on eBay. So you can pick one up for under a tenor. The circuit at the bottom is pretty straightforward, really. A little chip at the bottom of the bottom left-hand side is Texas Instruments, a positive modulation controller, and that actually controls a simple boost converter, which takes in nine volts and boosts it up to about 400 volts, which is what the GM tube needs. When you've got 400 volts across it and then you get a radioactive particle entering the tube, it ionises the gases inside the tube, which then has a sort of cascade which generates a very short pulse. It's on the right-hand side, are pulse stretchers, basically. It's a triple-five timer, which takes in a short pulse of about a few microseconds and stretches it up to milliseconds, which is then fed to that little black ego speaker at the bottom there. So this was very simple, and it worked quite nicely for demonstrating it. But a few months after that, I had chemotherapy, and after that I wanted to know how it had done, so they showed it to me for another scan. This time I wanted to know just how much radiation I was getting, so I decided to add an actual count facility to it. So this is Mark II, which is one I've got with me today, and I reused the circuit. You can see at the back, that's the circuit from the first model. It's simply incorporated a new circuit board with various boost converters, an 18650 to provide the power, and a nifty little OLED screen at the front. That's mostly pre-packaged to them. They're sort of cheap Chinese boost converters and things that I picked up for Ennis, really. This is an overhead view of it. You can see there's a couple of boost converters there. There's an Arduino nano microcontroller, and there's a charging circuit for the 18650, so I can recharge the thing and open it up. There's a close-up of the OLED display, which looks pretty smart. It also looks vaguely like it's a full-color one, but it's actually monochrome. The clever Chinese have just stuck a couple of color filters over it, so you stuck with the yellow strip at the bottom and a blue bit at the top. You can get these up to about £1.50 off AliExpress, and they're very useful, very handy for small circuits for your room for a bigger display. These are the other notes. I've got a count per second, and I also added a battery voltage monitor, just because. Having done all that and irradiated my friends another time, it actually got up to quite impressive count. It was about 110,000 counts per minute when I was first injected with the thing. I did take countering with me both times, and they didn't seem to eject too much. The most recent thing is I've just had a course of radiotherapy. That finished about three weeks ago, and this was the machine that they used to do it, and it was extremely swish, and it's a rather impressive bit of kit. The big thing at the top is the actual, it's actually a linear accelerator. Technically it doesn't produce gamma radiation, it produces X-rays. X-rays are nowadays, they're a bit of a conundrum really, because depending on which field you're in, they're classified in different ways. If you happen to be an astronomer, then the traditional way of doing this thing is the electromagnetic spectrum runs up through visible light, through ultraviolet, up to X-rays, and then finally to gamma radiation. However, that has kind of changed in recent times because of things like this linear accelerator. It can actually produce X-rays that have shorter wavelengths and are more energetic than gamma radiation that's produced by radioactive materials. So technically it's an X-ray device. It does in fact have two X-ray emitters because the thing on the right-hand side is a CT scanner. This is very sophisticated bit of kit because when you lie on the platform, that platform is actually pure carbon fibre, and it's made out of carbon fibre. First of all, so they don't drop you when you're sort of hung out over the edge of the thing. Secondly, because carbon is radio-transparent, or pretty much so, and therefore they can actually send the beam in from underneath you as well as on top, so it gives them a lot of control. This is the machine behind the public face. It looks a lot more like a physics experiment, and the way that the radiation is produced, the yellow thing at the top on the left-hand side is actually a magnetron. I've had a look at the guys of the radiographers at the centre where I was being treated, found out that I was a geek, and they very kindly unlocked the doors and let me have a poke around behind the thing, which was kind of them, and the magnetron actually looks a lot like a scaled-up version of what you find in the microwave oven, and the way it works, basically, is the magnetron pulses microwaves into the long tube, which is the linear accelerator, and there's a source of electrons at the back of the thing, and the radiation actually accelerates the electrons that are injected at the base of the thing up to multiple megavolts. They then hit a tungsten target at the head, and the electrons decelerate very rapidly, and gamma rays are emitted, well, x-rays are emitted, sorry, I'm mixing my terminology here, and that's actually then focused and creates the treatment beam. So, this is a rather clever little thing called a multi-leaf collonator, and this also sits in the head. These little slabs are slices of tungsten, and each slice has its own little motor, and as the thing is scanning, the motors push these little leaves in and out, and it focuses the radiation exactly where it needs to be, so nothing gets radiated that shouldn't be, which I was very much in favour of. So, after I've taken in my gygaric accounts after the obligatory check of the scanning process, I thought part of the problem was you have to stay absolutely still when you're being treated, and I couldn't actually see the display on the gygaric account when it was sitting on the chair about three metres away, so I decided to upgrade the firmware so that I could get a record of the counts, and so I rewrote the firmware and took it in again, and the odd beam actually has about a K of E-bron, a non-volatile memory, so I managed to put in a recording facility which tracks the amount of radiation receiving every second, and it was just about enough to cover the whole treatment. These are the results. The bit on the left-hand side is the CT scan, and the bit on the right-hand side is the actual treatment, and I was surprised to see that the treatment had much less apparent radiation than the CT scan, but having given it a little thought, the beam is much more focused for a start, so not all of it is going to work, or very little of it really, because it's going to be hitting the GM2. Also, it's high in very high energy radiation, and it's a thin walled tube, so most of the radiation goes straight through it, and it won't get detected. So what's actually being detected there is probably secondary radiation where the gamma rays are hitting items in the rub, and then stimulating the detector. You may notice that it seems to be a kind of ceiling. It looks as though it's sort of maxing out at some points on there, and I have no idea where that is, so if anybody's got any theories about that, there was a physicist, actually, resident among the treatment centre, and she was kind of intrigued by this, so apparently this graph has been passed around the physics community, so they kindly gave me some explanations to why it was, but I don't think they've got a definitive answer as to why they won't get those flat spots. So I mentioned that these things are cheap, and this is one which I picked up a few days ago, but I saw the ad on eBay. As you can see, it's £9.40, something like that. Looks like a new tube. They call it SPM 20s. The label's in Cyrillic. And this is the code for the counsellor that I wrote. I'll put it on GitHub, so if you're interested in building your own, I'm going to try and provide a circuit for it as well at some point, so I haven't got around to that just yet, but the source code has been open-sourced and is available. There's also a Python programme there, which I use because I've implemented a rudimentary form of compression to fit more readings in, and that suggests a little decoder to uncompress it. So I briefly mentioned some possible upgrades to the thing. This is one of the upgrades which actually is on-order, but unfortunately it didn't arrive in time for the ADMF camp. This is an SBT9. I'm not very good on Cyrillic, but this is what they call an end-window detector. It's got a very thin micro-window at the end of it, and this will pick up alpha particles as well as the beta and gamma, and they're a fair bit more expensive. I think this cost me about £30, but the nice thing about them is that they will work with exactly the same circuitry that I've already got, so I can basically tweak the hardware and plug it in, hopefully. So that's pretty much it. Thank you very much for coming and listening to me. I think I've probably just about exceeded my... I have exceeded my allotted time, so if you've got any questions about it, our Milking's Maker Space tent is just across the way there, so you can come and have a chat to me, and I'll be happy to answer any questions that you've got there. Thanks very much.