buettneb@Informatik.TU-Muenchen.DE (Buettner) (04/24/91)
Hi There! I am a little concerned about my new home made power amplifier. It uses a 4-1000A at an anode voltage of about 5.5kV. I have heard that Gamma radiation is produced at around 5kV. What I want to know is: How can I measure X-radiation (CHEAP)? How much is tolerable? CRTs produce X-Rays too, so how do manufacturers get around this problem. For thermal reasons I cannot put everything in a big box. Any takers out there? Ben Buettner (DL6RAI)
CPS@cup.portal.com (CHRIS PATRIC SMOLINSKI) (04/25/91)
The company I work for makes gauging equipment that uses X rays to measure the thickness of materials (metals and non metals). Typically, we use X rays in the range of 20 to 160 kV (that is, the voltage on the tube is from 20 kV to 160 kV), with a beam current of 1 to 4 milliamps. The detectors we use include ion chambers and various crystals (which emit UV light that is detected by photomultiplier tubes). I don't know of a cheaper detector. But to calm you, at 20 kV, the radiation is typically completely stopped by 1/16 of an inch of steel. If your amp is mounted in a metal box, you will be completely safe. - CHRIS
larry@kitty.UUCP (Larry Lippman) (04/25/91)
In article <1991Apr23.172122.13076@Informatik.TU-Muenchen.DE> buettneb@Informatik.TU-Muenchen.DE (Buettner) writes: >I am a little concerned about my new home made power >amplifier. It uses a 4-1000A at an anode voltage of >about 5.5kV. I have heard that Gamma radiation is >produced at around 5kV. > >What I want to know is: How can I measure X-radiation (CHEAP)? There are several methods for measurement of x-ray radiation, such as an ionization chamber and a scintillation detector. However, neither of these techniques are particularly simple or "cheap" to implement as a do-it-yourself project. One also has the problem of calibration for such a device; after all, what's the point of building it if the indication has no quantitative benchmark? My best suggestion, if you are really concerned, is to obtain a photographic film badge dosimeter, fasten it to the outside of the device in question, run the device for several hours, and then have the film badge developed and evaluated with a densitometer. There are outside service organizations who will provide such a service, but you will probably not like the cost. The best approach would be to find a friend who works for a hospital radiology or nuclear medicine department and has some "pull" to do a little favor... :-) Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
kludge@grissom.larc.nasa.gov ( Scott Dorsey) (04/26/91)
In article <1991Apr23.172122.13076@Informatik.TU-Muenchen.DE> buettneb@Informatik.TU-Muenchen.DE (Buettner) writes: >What I want to know is: How can I measure X-radiation (CHEAP)? >How much is tolerable? CRTs produce X-Rays too, so how do >manufacturers get around this problem. For thermal reasons >I cannot put everything in a big box. 5.5 Kv tubes can produce some reasonable soft X-rays. Go to your friendly neighborhood dentist and explain your concern. Get two small squares of dental X-ray film (actually, mammography film is even more sensitive). Put one next to the transmitter, and keep another someplace else in the house (or in another house altogether). Give it a couple of days. Then have him process the two sheets and look at the difference in density. You should not see any difference, and I doubt you will. Do note that the reference sheet will fog a bit if you keep it near anything radioactive, like brick. Ordinary photographic film will work as well, but it's not anywhere near as sensitive to X-rays. You'd want to wait longer. --scott
esj@harvee.UUCP (Eric S Johansson) (04/27/91)
In article <4902@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: > My best suggestion, if you are really concerned, is to obtain a > photographic film badge dosimeter, fasten it to the outside of the device > in question, run the device for several hours, and then have the film > badge developed and evaluated with a densitometer. There are outside > service organizations who will provide such a service, but you will probably > not like the cost. The best approach would be to find a friend who works > for a hospital radiology or nuclear medicine department and has some "pull" > to do a little favor... :-) > I would not trust film badge dosimeters. My wife works for a vet and they use film badge dosimeters in their x-ray room. One of her co-workers decieded to "test" the dosimeter by giving it a full dose of x-rays i.e the badge was the x-ray target. The report on the badge gave no indication that the badge had been exposed. Now, I don't know what the detection threshold is or if the badge readers can tell the difference between types of exposure but I don't have much faith in dosimeters anymore. ( honey, the light is keeping me awake. please put your head under ther covers... :-) --- eric -- ... ^^^ eric johansson UUCP ...!uunet!wang!harvee!esj esj@harvee.uucp * * a juggling fool AT&T (617) 577-4068 (w) o HAM ka1eec \_/ CSNET johansson%hydra@polaroid.com or hydra!johansson@polaroid.com source of the public's fear of the unknown since 1956
larry@kitty.UUCP (Larry Lippman) (04/28/91)
>> My best suggestion, if you are really concerned, is to obtain a >> photographic film badge dosimeter, fasten it to the outside of the device >> in question, run the device for several hours, and then have the film >> badge developed and evaluated with a densitometer. > >I would not trust film badge dosimeters. My wife works for a vet and >they use film badge dosimeters in their x-ray room. One of her co-workers >decieded to "test" the dosimeter by giving it a full dose of x-rays >i.e the badge was the x-ray target. The report on the badge gave no >indication that the badge had been exposed. Film badge dosimeters *DO* work! After all, how are x-rays most commonly taken, if not by means of exposing photographic film? I suspect the incident you related is isolated, and (hopefully) very uncommon. It's obvious that the organization processing the dosimeter film made some error. >Now, I don't know what >the detection threshold is or if the badge readers can tell the >difference between types of exposure but I don't have much faith >in dosimeters anymore. Good quality film badges have multiple filters covering portions of the film. Such filters permit bracketing of exposure into energy levels between 0.030 and 1.5 or so MeV. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
ken@swbatl.sbc.com (Ken Gianino 5-9081) (05/01/91)
>I would not trust film badge dosimeters. My wife works for a vet and >they use film badge dosimeters in their x-ray room. One of her co-workers >decieded to "test" the dosimeter by giving it a full dose of x-rays Does anyone still use film badges? I thought the whole industry switched over to thermoluminescent dosimeters years ago. They look like film badges. Maybe I'm wrong and just the nuclear power industry switched to TLD's for Gamma dose. -Ken WB0QNA
larry@kitty.UUCP (Larry Lippman) (05/02/91)
In article <1991May1.161415.4235@swbatl.sbc.com> ken@swbatl.sbc.com (Ken Gianino 5-9081) writes: >>I would not trust film badge dosimeters. My wife works for a vet and >>they use film badge dosimeters in their x-ray room. One of her co-workers >>decieded to "test" the dosimeter by giving it a full dose of x-rays > > Does anyone still use film badges? Sure! > I thought the whole industry switched > over to thermoluminescent dosimeters years ago. They look like film badges. Film badges, which typically use the dual-emulsion Kodak Type 2 Personal Monitoring Film, are useful for estimating the energy distribution of absorbed radiation since they generally mask the film with four filter quadrants. Film badge operation and processing cost is also somewhat less than that of TLD. ICN Biomedical, Inc., which processes film badge dosimeters for my organization, does a brisk business in film badges, although they also offer TLD dosimeters. > Maybe I'm wrong and just the nuclear power industry switched to TLD's for > Gamma dose. I can't speak about the nuclear power industry, but in my travels in industry and government where radionuclides are used for analytical chemistry purposes, I see film badges almost exclusively rather than TLD. TLD might be particularly useful in the nuclear power industry since it also detects neutron energy, whereas film badges are not suited for neutron measurement. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
anachem@silver.ucs.indiana.edu (mark gilstrap) (05/03/91)
In article <4916@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <1991May1.161415.4235@swbatl.sbc.com> ken@swbatl.sbc.com (Ken Gianino 5-9081) writes: >>>I would not trust film badge dosimeters. My wife works for a vet and >>>they use film badge dosimeters in their x-ray room. One of her co-workers >>>decieded to "test" the dosimeter by giving it a full dose of x-rays >> >> Does anyone still use film badges? > > Sure! > Here at IU too. >> I thought the whole industry switched >> over to thermoluminescent dosimeters years ago. They look like film badges. > > Film badges, which typically use the dual-emulsion Kodak Type 2 >Personal Monitoring Film, are useful for estimating the energy distribution >of absorbed radiation since they generally mask the film with four filter >quadrants. Film badge operation and processing cost is also somewhat less >than that of TLD. > The masks help discern accidental film fogging from real exposures. Unfortunately it costs extra to have a human look for a pattern on the film vs the automatic densitometer readings. My experience with IU is that a reading is always considered to be an accident. "you might have left it clipped to a lamp or in a window or on a heat register" and never is the human eye and associated expense authorized. So we never know. We have to go by cumulative totals correlated to work location - e.g the old GE xrd/xrf is a hot place. Even though an electronic's technician can "see" the x-rays out in the hallway with a detector tube as he passes the doorway, the IU rad safety screenings never see anything.... I know of cases where students wanted to test the system and intentionally exposed film badges. Never a word.... The only action we get is when someone gets a burn from one of the stuck interlocks etc... Somehow IU finagled a self policing agreement. If you try to go to OSHA with it - well IU has an OSHA man right here in his own office on campus. He was a footbal star...took IU to the Rose Bowl a few decades back...doesn't know where to look when you ask him for the wording of a regulation... but I digress.
edhall@rand.org (Ed Hall) (05/04/91)
In article <4212786@harvee.UUCP> esj@harvee.UUCP (Eric S Johansson) writes: >I would not trust film badge dosimeters. My wife works for a vet and >they use film badge dosimeters in their x-ray room. One of her co-workers >decieded to "test" the dosimeter by giving it a full dose of x-rays >i.e the badge was the x-ray target. The report on the badge gave no >indication that the badge had been exposed. Could well be that the badge showed a high exposure, then a human was called into the loop who took one look at it and said "Looks like some joker put this one in the beam; no problem." I'm sure that your wife's co-worker wasn't the first one to "test" the system in this way. -Ed Hall edhall@rand.org
alison@wsrcc.com (Alison Chaiken) (05/04/91)
How do TLD dosimeters work? I know how film badges work! -- Alison Chaiken alison@wsrcc.com (202)767-3603 [daytime] uunet!wsrcc!alison
larry@kitty.UUCP (Larry Lippman) (05/06/91)
In article <1991May4.005946.730@wsrcc.com> alison@wsrcc.com (Alison Chaiken) writes: >How do TLD dosimeters work? I know how film badges work! TLD dosimeters work on the principle of thermoluminescence resulting from radiation exposure. When certain crystalline phosphors, such as lithium fluoride and calcium fluoride, are exposed to ionizing radiation, emitted electrons are trapped in crystalline lattice imperfections. As long as the crystalline phosphor is maintained at close to ambient temperature, such electrons remain trapped for long periods of time (like months). When the phosphor is subsequently heated, the trapped electrons are released, thereby resulting in emission of visible light energy. Integration of the measurement of visible light energy emitted during heating of the TLD material may be correlated to an integrated radiation dose. A readout of a TLD dosimeter is sometimes referred to as a "glow curve" - it is a plot of emitted energy against time during the heating of the TLD element. TLD dosimeters have two advantages over film dosimeters: (1) they may be reused by annealing of the element - a slower heating process following that used for readout; (2) the readout process may be totally automated, with less likelihood of human error. TLD dosimetry was developed during the 1950's, and became really popular starting in the early 1970.s Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
klg@george.mc.duke.edu (Kim Greer -- rjj) (05/07/91)
In article <1991May1.161415.4235@swbatl.sbc.com> ken@swbatl.sbc.com (Ken Gianino 5-9081) writes:
==I would not trust film badge dosimeters. My wife works for a vet and
==they use film badge dosimeters in their x-ray room. One of her co-workers
==decieded to "test" the dosimeter by giving it a full dose of x-rays
=
= Does anyone still use film badges? I thought the whole industry switched
= over to thermoluminescent dosimeters years ago. They look like film badges.
= Maybe I'm wrong and just the nuclear power industry switched to TLD's for
= Gamma dose.
= -Ken WB0QNA
Well, Siemens provides film badge reading for quite a few hospitals
(including here at Duke). There are other companies that provide film
badges. We, actually Radiation Safety, used to do our own in house TLD
service for dozens of labs besides for the hundreds of Radiology employees
(x-ray/nuc med/rad oncology/PET/etc.). While the TLD's are very precise, and
accurate for very low readings (like less than 10 mr/month), apparently the
extra time and expense to provide in house TLD's was just too great to
otherwise let someone with greater volume (and no "conflicts of interest")
take it over. Then again, if a large percentage of readings are less than
10 mr/month, it is probably not worth worrying with anyway. At larger
doses, like >25, the film badges are supposed to be relatively accurate. If
anyone is really that interested, I will try to find out the (major)
reason(s) we converted from TLD's to film badges. Personally, I would
rather use TLD's, but nobody asked me my opinion! :^)
(For one thing, they hold up a lot better going through a washing machine
when you forget to take them off your clothes. =:^) )
--
Kim L. Greer
Duke University Medical Center klg@orion.mc.duke.edu
Div. Nuclear Medicine POB 3949 voice: 919-681-5894
Durham, NC 27710 fax: 919-681-5636tom@syssoft.com (Rodentia) (05/07/91)
In article <1991May3.194713.15676@rand.org> edhall@rand.org writes: [description of testing a dosimeter by x-raying it, but not being informed of an exposure deleted] >Could well be that the badge showed a high exposure, then a human was >called into the loop who took one look at it and said "Looks like some >joker put this one in the beam; no problem." I'm sure that your wife's >co-worker wasn't the first one to "test" the system in this way. I hope that wasn't the case. Consider this: person positioning patient when the x-ray machine machine either goes off spontaneously, or some fool walks up and hits a button. I'd sure want to know if this happened. Is this really rare enough to be not a concern? Aside: My wife was informed that her badge was too hot one month. She was told it was probably a fluke, and it never happened again. They said she may have left it too close to a TV or something. She doesn't work near x-ray anymore, and probably won't again. (That incident wasn't the decider, but why even risk it if you don't have to?) -- Thomas Roden | tom@syssoft.com Systems and Software, Inc. | Voice: (714) 833-1700 x454 "If the Beagle had sailed here, Darwin would have | FAX: (714) 833-1900 come up with a different theory altogether." - me |
mac@cis.ksu.edu (Myron A. Calhoun) (05/07/91)
In <1991May6.200739.28370@syssoft.com> tom@syssoft.com (Rodentia) writes: >Aside: My wife was informed that her badge was too hot one month. She >was told it was probably a fluke, and it never happened again. They said >she may have left it too close to a TV or something.... I once left a dosimeter taped to the screen of a 21-inch color TV for 24 hours and saw absolutely ZERO change in its reading. --Myron. -- # Myron A. Calhoun, Ph.D. E.E.; Associate Professor (913) 539-4448 home # INTERNET: mac@cis.ksu.edu (129.130.10.2) 532-6350 work # UUCP: ...rutgers!ksuvax1!harry!mac 532-7353 fax # AT&T Mail: attmail!ksuvax1!mac W0PBV @ K0VAY.KS.USA.NA
jeff@hpuplca.nsr.hp.com ( Jeff Gruszynski ) (05/08/91)
> > In article <1991May3.194713.15676@rand.org> edhall@rand.org writes: > [description of testing a dosimeter by x-raying it, but not being informed > of an exposure deleted] > >>Could well be that the badge showed a high exposure, then a human was >>called into the loop who took one look at it and said "Looks like some >>joker put this one in the beam; no problem." I'm sure that your wife's >>co-worker wasn't the first one to "test" the system in this way. > In a past life I worked in lab that used KCs of Co-60. As a "prank" someone's film badge was put on the lead shielding (outside cell). (I heard about it after the badge was found.) It read a several times higher than normal (still just mRem) when it was read a the end of the month. Radiation Safety brought the 'victim' in and intensely quized him on whether he'd walked by the source more often than usual, whether he was leaning closer to it, etc. Their diligence seemed impressive. Even so, when the source can deliver a instantly lethal dose of gamma to 10 people every second, you can relax only so much... (i.e. 10KRad/sec. Yes, yes, it's not physically possible to shuffle 10 people into the source path, let alone bring the sources up with the door open, and 1KRad is not instantaneous either, but it's a way to get a feeling for 'how big' the dose rate is.) >I hope that wasn't the case. Consider this: person positioning patient >when the x-ray machine machine either goes off spontaneously, or some >fool walks up and hits a button. I'd sure want to know if this happened. > >Is this really rare enough to be not a concern? > >Aside: My wife was informed that her badge was too hot one month. She >was told it was probably a fluke, and it never happened again. They said >she may have left it too close to a TV or something. She doesn't work >near x-ray anymore, and probably won't again. (That incident wasn't the >decider, but why even risk it if you don't have to?) > > >-- Another more amusing story. One of the people in the lab went into the hospital for some medical diagnostics. He came back to work in the afternoon. As I was returning from lunch the radiation alarms went off as I was walking into the building lobby. I immediately got a sinking feeling as I thought of the aforemention gamma source *and* the people who had skipped lunch to finish up some work. The building was evacuated. Radiation Safety came in with detectors. It wasn't the source though. But there were some diffuse readings that kept moving around as they searched the room. "Hey, wait a second! It's you!" The guy had had a tracer diagnostic and was hot! If we'd had something that hot from the lab, we would have had to put it in lead, used DOT and state permits to move it, etc. (of course, our source couldn't have made it hot, gammas don't activate, but someone else's reactor could.) I was shocked by how much they must have used, but apparently it was "normal" therapeutic levels. Go figure. Jeff Gruszynski T&M STE SE Santa Clara Sales Hewlett Packard ---