Introduction to scintillators — Transcript

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1. 0:00hey I'm Carl Willis I'm on the faculty
2. 0:02here in the nuclear engineering
3. 0:04department at the University of New
4. 0:05Mexico and also I'm the public
5. 0:07information and Outreach officer for the
6. 0:09Trinity section of the American nuclear
7. 0:12society today we're going to look at
8. 0:14radioactive stuff making things glow
9. 0:17which is one of my favorite sites in the
10. 0:19whole world um but it's also a very
11. 0:22useful thing for industrial radiation
12. 0:24detection and measurement and medical
13. 0:27Technologies such as pet scanners that
14. 0:30use the light produced when radiation
15. 0:32interacts with stuff so we're going to
16. 0:34be looking at cators today we've got a
17. 0:37bunch of cation materials set up in the
18. 0:41source closet and we're going to go to
19. 0:43the very back of the room pull out a
20. 0:45really hot Source we're talking about a
21. 0:48tenth of a cury of uh cium 137 and let
22. 0:53that radiation bathe those cators in
23. 0:56high energy gamma radiation and then
24. 0:58we're going to take a long exposure your
25. 1:00photo and show you just what colors come
26. 1:02out of those materials so it should be
27. 1:04fun but there's a couple technical
28. 1:06elements first of all we want to make
29. 1:07sure we don't get
30. 1:08Overexposed so I've got some toys from
31. 1:13Costco to help me manipulate the source
32. 1:16so that I can stay away from it so we've
33. 1:18got our uh distance component you'll see
34. 1:21when we get in there we've also got
35. 1:22shielding set up and I'll talk a little
36. 1:24bit more about that and uh we're also
37. 1:26going to be very quick with what we're
38. 1:28doing so time distance shielding we're
39. 1:30going to stay safe I don't expect to get
40. 1:32any measurable dose from this activity
41. 1:34despite the fact that we have a high
42. 1:37activity Source in use so let's go take
43. 1:40a look I think we'll get some really
44. 1:42cool beautiful photos thanks for
45. 1:48watching all righty so the first thing
46. 1:51I'm going to point out we've already got
47. 1:53our experiment staged all of our
48. 1:55cellation materials are set up on this
49. 1:57piece of glass and there's a bunch of
50. 1:59lead here which is designed to keep the
51. 2:02radiation going up into the materials of
52. 2:04interest and not out towards me um we've
53. 2:08also got a camera if you want to uh show
54. 2:12us uh which is shielded with lead and
55. 2:14hopefully it'll be enough to keep the
56. 2:16noise down in the camera but we're going
57. 2:18to uh take a long exposure so this
58. 2:20camera is already staged and set up and
59. 2:23ready to go we've got a um survey meter
60. 2:27here it's on a high range so I can see
61. 2:29what my dose rates are when I go to uh
62. 2:32start the experiment and what I want to
63. 2:35do I want to take the source out of its
64. 2:38storage location here I'm going to turn
65. 2:40it upright and then I'm going to move it
66. 2:44uh directly under the scintilating
67. 2:46materials and some of these things are
68. 2:48easier said than done the source could
69. 2:50flip over um you know but I'm prepared
70. 2:53for that i' uh I'm I know what it looks
71. 2:56like feels like and and I'm prepared for
72. 2:58that so let me get this camera set
73. 3:02up
74. 3:04timer self timer there it is it always
75. 3:08turns off on this particular camera so
76. 3:10I'm going to set it to 10 seconds I've
77. 3:12got a good view in there I've got my
78. 3:15I've got on the bulb setting and I've
79. 3:16got my shutter ready to go so everything
80. 3:19is good except for the source so now
81. 3:22we're going to take our source
82. 3:23out and the first thing we'll do is just
83. 3:26get it out and then we're going to make
84. 3:28sure we get it oriented correctly
85. 3:30so here's our
86. 3:32source that's a nice hot cesium
87. 3:35source and we're just going to work it
88. 3:38over this way stand it
89. 3:41up I'm going to grab it at the bottom
90. 3:44we're going to move it where it needs to
91. 3:47go which is all the way back in
92. 3:53here all righty sources is in place I'm
93. 3:57going to check the radiation level where
94. 3:59my camera is because I don't want the
95. 4:01camera to go postal and uh looks to me
96. 4:05like right near the camera we've got
97. 4:09maybe 20 or so milleran per hour all
98. 4:14righty so we're ready for this
99. 4:17picture guys you ready to get the
100. 4:21lights
101. 4:23okay so I'm going to back out quick okay
102. 4:308 7 6 let's get the lights off
103. 4:36guys awesome okay let's see what
104. 4:41happens well folks here it is the
105. 4:43picture we've been waiting for as you
106. 4:45can see the cellation materials exhibit
107. 4:49a wide diversity of colors and
108. 4:52brightnesses and although the picture
109. 4:54doesn't show it also in their response
110. 4:56times to radiation
111. 4:58events each each of these materials
112. 5:00produces a little flash of light when
113. 5:03it's hit by a discrete gamma ray and
114. 5:05what you're seeing is the integrated
115. 5:07totality of millions of these little
116. 5:09cation events let's talk about some of
117. 5:12these materials and where they're used
118. 5:14so over here in the can to protect it
119. 5:17from Air is sodium iodide one of the
120. 5:20most widely used cation materials you'll
121. 5:24find sodium iodide being used for
122. 5:25portable gamma spectroscopy in uh law
123. 5:29enforc
124. 5:30applications environmental assessments
125. 5:33and radiological surveys in workplaces
126. 5:35where radioactive material is used it's
127. 5:37truly the Workhorse of the industry and
128. 5:40it's manufactured in large quantities as
129. 5:43you can see the light it produces is a
130. 5:44beautiful blue
131. 5:46color plastic cators are another common
132. 5:50choice that you find in portable
133. 5:52equipment it's Mass producible it's
134. 5:54inexpensive and it
135. 5:57has uh a similar compos opposition to
136. 6:00human tissue and so it has what's called
137. 6:02a tissue equivalent response and that's
138. 6:04useful in in survey instruments as well
139. 6:06and here's an example that we have in
140. 6:09the uh UNM Laboratories being used as a
141. 6:11survey meter with tissue proportional
142. 6:16response the very brightest
143. 6:18cator in this lineup is thalium doped
144. 6:23cium iodide and as you can see it
145. 6:26produces a brilliant yellowish green
146. 6:30light this material is not as useful as
147. 6:33sodium iodide because that color is not
148. 6:37as good for the photo multiplier tubes
149. 6:40that are typically used in equipment so
150. 6:44this the sodium iodide despite being not
151. 6:46quite as bright uh actually puts more
152. 6:49signal into photo multiplier tubes but
153. 6:51there are other technologies that are
154. 6:54emerging um Solid State uh photo
155. 6:57multipliers and things like that for
156. 6:59which C iodide is a better match and so
157. 7:02we're seeing more instruments being made
158. 7:04with cesium iodide particularly very
159. 7:06Compact dosimeters and things like that
160. 7:10I have three examples in here of
161. 7:13materials that are used in detectors for
162. 7:16positron emission tomography or pet
163. 7:19scans this medical technique allows us
164. 7:22to image the functional and metabolic
165. 7:25behavior of individual organs in the
166. 7:27body so we have yum silicate lutetium
167. 7:31doped yum silicate and bismuth germinate
168. 7:35all three of these are dense bright
169. 7:37materials that emit in the blue green
170. 7:39and are very effective for pet scanners
171. 7:42so if you ever have to get a pet scan
172. 7:45you can thank these materials for making
173. 7:47the technique work
174. 7:49reliably here we have an example of a
175. 7:52material that emits very little light in
176. 7:55fact it looks just like a piece of inert
177. 7:57glass in the photo but this is extremely
178. 8:00valuable in certain physics research
179. 8:04because it is the fastest responding
180. 8:07material of all of these cators this is
181. 8:09barium fluoride and although you can't
182. 8:12see much light coming from it it is a uh
183. 8:16producer of ultraviolet and dark purple
184. 8:18light and not very much light but it is
185. 8:21extremely fast it has time resolution
186. 8:24below 1 nond and this is very useful if
187. 8:27you want to look at the coincidence
188. 8:30of radiation events or the time of
189. 8:32flight of radiation in an experiment
190. 8:35similarly we have a piece of lead tongue
191. 8:38State over here on the very far left and
192. 8:41this material also is not bright it
193. 8:43looks just like a big chunk of glass you
194. 8:45can't see any light coming out of it in
195. 8:46the photo but this has enabled some of
196. 8:49the most pivotal high energy physics
197. 8:52discoveries of the last century this
198. 8:55material is used in ton quantities in
199. 8:58detectors at C turn and has been used to
200. 9:00help discover the higs Bon and it
201. 9:03doesn't need to be a very bright cator
202. 9:05because it's looking for extremely high
203. 9:07energy events where particles deposit a
204. 9:10large amount of energy over the entire
205. 9:13bulk of a massive multi-ton quantity of
206. 9:16the
207. 9:17material at the bottom here I have a
208. 9:20bundle of cation fibers and you can't
209. 9:23see much light being given off by them
210. 9:25but they have an extremely valuable
211. 9:27property which is that they can localize
212. 9:30the source of radiation spatially very
213. 9:32well you can have a bundle of these
214. 9:34fibers and know exactly where the
215. 9:36radiation interaction took place that's
216. 9:39extremely important in certain Imaging
217. 9:42applications most of these materials
218. 9:44emit in the blue green end of the
219. 9:47spectrum the short wavelength end of the
220. 9:49electromagnetic spectrum but um that
221. 9:52doesn't mean we can't have materials
222. 9:53that emit in the red and so I have two
223. 9:55examples here of those we've got
224. 9:58mercurous Brom
225. 10:00which is an experimental material that
226. 10:01emits heavily in the infrared and red
227. 10:04and we have um Atrium oxy sulfide with a
228. 10:08europium dopent and a in a powder form
229. 10:11that emits red light and unlike large
230. 10:14solid crystals the powder is not very
231. 10:16good at transmitting the light that it's
232. 10:18that is being produced in it so it has
233. 10:21more limited
234. 10:23applications finally I have included a
235. 10:26piece of yum
236. 10:28orthovanadate in in this lineup it has
237. 10:31no known applications yet as a cation
238. 10:34detector but I've observed that it
239. 10:36produces cation light that is not
240. 10:38dissimilar in color to that from the
241. 10:40cesium iodide so I decided to show off a
242. 10:43piece of it here and my larger point in
243. 10:46doing that is to say that cation
244. 10:49detector research is an ongoing Frontier
245. 10:52in nuclear engineering new materials are
246. 10:55constantly being developed to serve
247. 10:57application spaces in medicine and
248. 11:00Industry and law enforcement and basic
249. 11:03science and this is a great field of
250. 11:06study so if you like seeing stuff glow
251. 11:09and you're interested in the properties
252. 11:11of stuff that glows when radiation hits
253. 11:13it this is a very fruitful area to get
254. 11:16into and I encourage you to come study
255. 11:18nuclear engineering and be part of that
256. 11:21ongoing Revolution with all that said
257. 11:24thank you very much for joining me today
258. 11:26I hope you enjoyed this picture as much
259. 11:27as I enjoyed taking it
260. 11:29and if you're interested in further
261. 11:31activities having to do with nuclear
262. 11:33science week please see the link up in
263. 11:35the uh screen and if you're interested
264. 11:38in joining the Trinity section of the
265. 11:40American nuclear Society I would love to
266. 11:42have your input again please follow the
267. 11:45link up above thank you very much look
268. 11:48forward to seeing you in another
269. 11:52video so
270. 11:54now comes the fun part we get to get the
271. 11:57source out of where it is put it back in
272. 12:00its storage container so hopefully we
273. 12:03can execute this Mission with uh with
274. 12:09success but this will be a real test of
275. 12:12my skills using
276. 12:18the the
277. 12:20thing there we
278. 12:24go
279. 12:26okay source is back home
280. 12:30and uh we have successfully performed
281. 12:33this experiment now we have to do the
282. 12:35now we get to do the fun part and go
283. 12:36look at the pictures we took which
284. 12:38hopefully will be nice but um one thing
285. 12:41I'll point out right away a fair bit of
286. 12:44radiation in the course of a 10-minute
287. 12:47shot is going to get on the sensor of
288. 12:48that camera so we're probably going to
289. 12:51see some some sparkles in there but uh
290. 12:54we'll see what we
291. 12:58get for