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Most radiation detector sensors, except Geiger Muller tubes, require a *preamplifier* to boost their weak signals to a level a Multi-Channel-Analyzer can deal with and display the familiar histograms we use for energy (MCA) or time studies (MCS or Multi-Channel-Scaler mode). This stage also acts as a buffer to convert the high impedance pulses from the sensor to drive a low impedance stage, perhaps a coaxial cable or some conventional electronic stage (bipolar transistor or IC). After the preamplifier, which is most often located in the sensor package, is a *shaping amplifier*. That stage shapes the raw pulses of the sensor into something that the following stages can recognize. With solid state sensors, this is often a triangular wave shape, and the shaping amplifier may be located within the sensor package as well. The various terms in the topic title are all the same item, just different names. FET input stages have been around for a very long time. If you've used an Eberline bench instrument, chances are it has a FET input. So do base mounted preamps for NaI(Tl) detectors, such as all the Canberra 12 and 14 plug on bases for Bicron scintillators etc. Rather than use some sort of homebrew setup, these first two stages can be purchased cheaply as LSI (Large Scale Integration) modules from several different manufacturers. From the same source, there are prewired PCB's to hold the modules and provide rudimentary functions such as power line bypass capacitors, input/ output terminals or connecters and any filtering needed on the power lines. Cremat is one mfg. that has very reasonable prices, suitable for the amateur experimenter's Home Lab, or Physics Class demonstrations. Using this approach, a customized package for various different sensors can be assembled at low cost. Pics are of the C.C. Preamp and Shaping Amp boxes Dr. Pruitchi used in his article on introductory Alpha Spec. Geo
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4 screws and the "nose cone" top part of the sensor housing separates. It has the sensor in it, hardwired with 6 wire umbilical cord. Sensor faces down towards the filter, and the lever mechanism that allows filters to be changed rotates the screened filter back downward to accommodate that. When the lever is rotated back to park/locked location, the filter back module cams up, pressing the filter home, blocking external light and air paths, while a switch on the lever alerts the control box there was a filter change. The popup dialog box must be ticked "was the filter replaced Y/N" to continue. Aside from that action there are no other mechanisms present in the slot. Below the back screen in the larger part of the sensor housing everything there has to do with airflow, much of the plumbing has to do with the Hot-Wire Anemometer air mass sensor, similar to what we have in the Eberline 6A head. Three of the 6 wires from the sensor go to those mini coaxial plugs in the main connector, the other 3 to regular signal pins. Most probably those first 3 are sensor signals, while the other 3 are power to the sensor and presumably a preamp/line driver in the "nose cone". No magic here, just updated versions of 1980 tech. The magic is in the control box computer, and that's what the patent covers. Geo
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Alan, Here¡¯s how to set up the Impex SmartCAM to readout in pCi/ml and Flow in LPM Record your original settings before changing things. Then open the Monitor tab then Instrument options. Check only Bypass Filter Log on and calibrate in cpm In the displayed column I¡¯ve moved these to display Temp Press Flow Alpha chronic Alpha acute Radon chronic Radon Acute Po-214 chronic Po-214 acute Po-212 chronic Po-212 acute Po-218 acute P-218 chronic When running I usually have the Top display show Radon Acute and the bottom display Radon Chronic. You¡¯ll need to multiply the pCi/ml x 1000 to get pCi/l. The EPA action level is 4 pCi/l at which point they think you¡¯ll die or go broke fixing it On the Channel tab: Set display units pCi ( should already be there) I¡¯m using Long as 140 and short as 60 sec. it was 240 and 120 but I¡¯m looking for quick response. Isotope window should be Radon Chronic ¨C you can¡¯t change it. Change the half life from E-18 to 186 sec which is the Po-218 half life that the radon will be calc¡¯ed from. That will get rid of the E-19 extension Check Archive data, Show differential, and show activity. That will get rid of the Radon pCih/l displayed and put radon activity pCi in its place on the screen. Equilibrium factor is how much Po-218 has platted out on the walls. I have generally used 0.3 but they are using the industry standard of 0.5. leave it 0.5 The other tabs ( Po-212 chronic etc. ) I haven¡¯t played with yet but the half lives and time may have to be adjusted there as well and I¡¯ll fool with that later. If you go to the View tab and check Raw data Channel it will display raw cps. I leave that unchecked unless I¡¯m doing a manual radon calc and need those numbers When shutting down under the File tab use the Shut Down option. OK lets report those radon room numbers. A this point don¡¯t sniff any sources as you only have one filter to play with and you¡¯ll be surprised to see what¡¯s left showing on the Spectra the next morning and just from room air. To change flow from CFM to LPM readout Go to the channels tab then to last tab Flow Change the display units to l/m, Under the Alarms box check first box change set boxes to ABOVE, 49.5, High Alarm ¨C leave all latch boxes unchecked check second box, set box to BELOW, 19.8, and Low Limit. check third box, set box to BELOW, 15, Low Fail Dud -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Geo Dowell Sent: Saturday, June 11, 2022 5:29 AM To: geoelectronics at rallstech.net; AlphaBetaSpectrometry Cc: Alan Jose Subject: Re: Alpha and Beta particle nuclear decay studies. This Weekend From: Alan Jose <Alan.Jose@...> To: geoelectronics@... Sent: Fri, 10 Jun 2022 22:07:01 -0400 (EDT) Subject: This Weekend "This weekend I plan on getting in plenty of lab time. We¡¯ll see. Alan" Good Alan. If you set up the IMPEX, and want to remove the filter card, be sure to ask me or read the instructions how th release it by rotating that lever- pull out the locking pin, rotate that lever as far as it will go, that releases the clamping mechanism so the filter can go in and out without damage. I messed up my filter before understanding that, but already have new filters coming from China. George
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This Weekend
To: geoelectronics@... Sent: Fri, 10 Jun 2022 22:07:01 -0400 (EDT) Subject: This Weekend "This weekend I plan on getting in plenty of lab time. We¡¯ll see. Alan" Good Alan. If you set up the IMPEX, and want to remove the filter card, be sure to ask me or read the instructions how th release it by rotating that lever- pull out the locking pin, rotate that lever as far as it will go, that releases the clamping mechanism so the filter can go in and out without damage. I messed up my filter before understanding that, but already have new filters coming from China. George
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So anybody seen these or know about them? I got two of the sample units but no controller.
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CAM filters
5
Here¡¯s some background on filter cards https://mirion.s3.amazonaws.com/cms4_mirion/files/pdf/spec-sheets/doc010295en-a_icam_fixed_filters.pdf?1579456643 A PTFE type from Milipore was $398/100 they didn¡¯t have a price on the glass fiber type and they are not card mounted I don¡¯t have a price from Mirion or Jeff yet but get ready to choke. Dud
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Under VIEW, DISPLAY, chose LOG and LINE Drawing. Here's a scan I can recognize. Also, photo of Rn-222 Alpha energies chart. Geo
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In remote outdoor air samplers, moving filters are the norm. This allows filter changing without an operatord.to the sites. IMPEX has such a head, we don't have that, nor would I want that option. I do have some rolls of filter material from such a site, new, sealed in tin cans and further sealed in factory plastic bags That filter material is glass fiber on paper backing. What came in the Impex is similar but seems to have a mesh interlayer. Looking closely at the supplied filter there are pinholes present. A clone of the filter card was attempted. When used to replace the worn-out test filter as suppled, everything changed on the spectrum readout, for the better. We will of course consider using the OEM filters for serious work, but these will be no cost playthings to gain experience. Now the Polonium peaks from Radon 222 daughters seem to be falling much more in line with predicted values. No other changes made. There are still other issues that need attending to, but those have been there since day 1, it's probably a matter of more training needed. PS if you request some of there be aware they have a textured side which goes towards the sensor (i.e., UP). It covers a 25mm hole perfectly. The cards used here are double weight 3X5's because it's what I had. 4X6 would be better raw material, that size could simply be folded in half longways forming a 'book", trimmed to size using the original card as a template, the filter material secured inside, then the edges taped shut It a pleasure to see the correct energy peaks from the Po species! I suggest printing the U-238 and Th-232 decay chains from the INL "Natural Decay Series: Uranium, Radium, and Thorium" and where it shows the alpha decays, pencil in the correct energy levels. This really helps not having to remember or look up what's what, If you don't have that link, it's also on my webpage K0FF@... PS Readings will be different on all instruments now, the weather has warmed, the widows screened, open, and an attic fan pumping fresh air in. It should prove interesting to retest everything, as the natural air should have far less Rn-222 present. A topic I would like to see discussed here is the broadening of the peaks, due to interaction of the Alpha Particles with matter (air). Geo Pics attached
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Well, after 6+ hrs of running and taking 20 min data between the RAD7 and the Impex CAM, the GAST pump died (yes it was hot and was maxed out at 32L/m). I can attest to the fact the CAM LOW FAIL alarm is LOUD and hard to mute without getting into the command mode which requires getting even closer to the Sonalert. We¡¯re going to need a bigger pump What do they recommend I wonder, my guess is a HiVol. I think I¡¯ll go have a Dixie cup full of a fine Boxed Merlot and grieve on the last Gasp of my poor $20 Gast pump. Dud From: dfemer [mailto:dfemer@...] Sent: Friday, May 27, 2022 1:59 PM To: '[email protected]' Subject: RE: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic Everything is supposedly in the manual, however we live by our wits alone. Dud From: [email protected] [mailto:[email protected]] On Behalf Of Geo Dowell Sent: Friday, May 27, 2022 1:46 PM To: [email protected] Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic THANKS Dud, great to know. Once I get it lined out, I'll start comparing to the Femtotech. how on earth did you figure that, was it in the manual? Geo ----- Original Message ----- From: Dude <dfemer@...> To: [email protected] Sent: Fri, 27 May 2022 14:36:57 -0400 (EDT) Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic margin: 0.0in; font-size: 12.0pt; font-family: "Times New Roman" , serif; } a:link, span.MsoHyperlink { color: blue; text-decoration: underline; } a:visited, span.MsoHyperlinkFollowed { color: purple; text-decoration: underline; } p { margin-right: 0.0in; margin-left: 0.0in; font-size: 12.0pt; font-family: "Times New Roman" , serif; } p.MsoNoSpacing, li.MsoNoSpacing, div.MsoNoSpacing { margin: 0.0in; font-size: 16.0pt; font-family: Arial , sans-serif; color: black; } span.EmailStyle19 { font-family: Arial , sans-serif; color: black; top: 0.0pt; letter-spacing: 0.0pt; font-weight: normal; font-style: normal; } *.MsoChpDefault { font-size: 10.0pt; } div.Section1 { page: Section1; } /*]]>*/ Geo/Nick To convert the wacko E-17 radon reading go to command mode with the Key get to the Radon tab and change the 1e-16 to 186 which is the Po218 half life.. Bring up the Radon Acute default page to read Po 218 acute and Radon Acute. It will be in pCi/ml multiply by 1000 to get pCi/l. I need to use Radon raw and Po raw but I still need to figure out how to do that. I¡¯m running the RAD 7and the SmartCAM together and the CAM showing 3.5 pCi/l while The RAD 7 is averaging 4.0 pCi/l +- 2.1. Doing a manual calculation it always comes up low by a factor 3 or so. That ma be due to not having all their corrections in there and using acute cps Dud From: [email protected] [mailto:[email protected]] On Behalf Of Geo Dowell Sent: Friday, May 27, 2022 10:42 AM To: [email protected] Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic " Geo, What kind of solid samples are going to run? One needs to be very careful not to crap up the detector. Most alpha samples are via liquid chem electro-deposited on steel disk, swipe and air sample filters. Don¡¯t put a loose sample in there. Dud" A few different electroplated discs on the IMPEX, But other units, anything I can lay my hands on Been collecting and waiting for this phase for a long time. All new to me. Geo ----- Original Message ----- From: Dude <dfemer@...> To: [email protected] Sent: Fri, 27 May 2022 13:16:02 -0400 (EDT) Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic margin: 0.0in; font-size: 12.0pt; font-family: "Times New Roman" , serif; } a:link, span.MsoHyperlink { color: blue; text-decoration: underline; } a:visited, span.MsoHyperlinkFollowed { color: purple; text-decoration: underline; } p { margin-right: 0.0in; margin-left: 0.0in; font-size:
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Okay so I did bring my little Gast pump to Texas. That's the good news. The bad news is that the motor is 240vac. And I haven't added the additional 240 outlets I need to for range, tube furnace, welder, etc. next to the door where it's convenient. It's a Gast 0211-V87 pump. So before I can even test it I need to either do some wiring or temp splice a dryer cord onto it to plug into my compressor outlet tucked way back in the corner behind the South Bend vertical mill.
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Radon instrument comparison
Attached is a comparison between the Smart CAM and a Niton (Durridge) RAD 7. It will be interesting to see Geo¡¯s FemtoTech data. Note that the CAM integrates the readings over a period of time which can be set in the software. I used 60 sec for the short acute and 140 for the chronic long. The default was 240 long and 140 short. I was more interested is fast response. The Po-218 needs to get to equilibrium which takes about 30 min. I used a flow rate of 1.13 cfm (32 lpm) which is about what was recommended on the CAM. The RAD 7 is very slow in the 100ml range I believe. There are some setting in the CAM that are not well explained. In order to get a radon reading without an exponent of E-17 go into the Channels Options and change the lifetime to 186 which is the half life of Po-218. Why that was set at E-17 was wrong Under channels tab you can check the Show differential and Integral which displays a RADON acute or Chronic in pCi/ml and a pCih/ml which was always zero so far. If you turn off the 2 check marks the display for radon is just RADON pCi/ml. If you check activity (differential is auto checked) it displays RADON in pCi/ml and pCi (activity). It would be nice if they had a way to use l rather than ml but, hey, what¡¯s 3 orders of magnitude anyhow. I¡¯m working on getting a price and supplier of the filter cards. We can do a group deal if anyone is interested. Dud From: [email protected] [mailto:[email protected]] On Behalf Of Geo Dowell Sent: Friday, May 27, 2022 1:46 PM To: [email protected] Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic THANKS Dud, great to know. Once I get it lined out, I'll start comparing to the Femtotech. how on earth did you figure that, was it in the manual? Geo ----- Original Message ----- From: Dude <dfemer@...> To: [email protected] Sent: Fri, 27 May 2022 14:36:57 -0400 (EDT) Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic Geo/Nick To convert the wacko E-17 radon reading go to command mode with the Key get to the Radon tab and change the 1e-16 to 186 which is the Po218 half life.. Bring up the Radon Acute default page to read Po 218 acute and Radon Acute. It will be in pCi/ml multiply by 1000 to get pCi/l. I need to use Radon raw and Po raw but I still need to figure out how to do that. I¡¯m running the RAD 7and the SmartCAM together and the CAM showing 3.5 pCi/l while The RAD 7 is averaging 4.0 pCi/l +- 2.1. Doing a manual calculation it always comes up low by a factor 3 or so. That ma be due to not having all their corrections in there and using acute cps Dud From: [email protected] [mailto:[email protected]] On Behalf Of Geo Dowell Sent: Friday, May 27, 2022 10:42 AM To: [email protected] Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic " Geo, What kind of solid samples are going to run? One needs to be very careful not to crap up the detector. Most alpha samples are via liquid chem electro-deposited on steel disk, swipe and air sample filters. Don¡¯t put a loose sample in there. Dud" A few different electroplated discs on the IMPEX, But other units, anything I can lay my hands on Been collecting and waiting for this phase for a long time. All new to me. Geo ----- Original Message ----- From: Dude <dfemer@...> To: [email protected] Sent: Fri, 27 May 2022 13:16:02 -0400 (EDT) Subject: Re: Alpha and Beta particle nuclear decay studies. need some pointers to background info on this topic margin: 0.0in; font-size: 12.0pt; font-family: "Times New Roman" , serif; } a:link, span.MsoHyperlink { color: blue; text-decoration: underline; } a:visited, span.MsoHyperlinkFollowed { color: purple; text-decoration: underline; } p { margin-right: 0.0in; margin-left: 0.0in; font-size: 12.0pt; font-family: "Times New Roman" , serif; } p.MsoNoSpacing, li.MsoNoSpacing, div.MsoNoSpacing { margin: 0.0in; font-s
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need some pointers to background info on this topic
24
Thank you guys for setting up this group. Problem for me is the physics of Alpha and Beta spectrometry. Can someone point me to any references on the mechanics of Alpha and Beta emission? My simple understanding was that Beta's energy from a given isotope is a continuum, hence is it possible to measure a spectra? I think Alphas are emitted in a narrower range? but doesn't distance and angle of incidence affect what level of energy is detected since it is a particle? P
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Radon Calc
2
Alpha Geeks, I still don¡¯t know what the Radon ~5E-17 pCi/ml readout is on the SmartCAM or where it comes from. However, using the Rn calculation in the manual (pg 33) with a detector efficiency of 0.25, Equilibrium factor of 0.3, an air flow of 1.13cfm (0.533 L/s), a mean life time of Po218 of 186sec and using the Po218 acute rate of 1.84 cps and a Po-212 chronic count rate of 0.05 cps. I get a Rn 222 concentration of 6.5 pCi/l in the rock strewn mancave. I¡¯ll try the RAD 7 and see if that is close. I should have used the Po¡¯s raw counts but I believe they are close for steady state conditions. If this is true then I¡¯m over the EPA action level of 4 pCi/l and will immediately turn both myself and the dog in to the EPA for prosecution, decontamination and a whole lung lavage Dud BTW anyone know of a quieter air pump than a GAST?
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first breath
7
Running for 30m so far. The Gast pump is full out at 1.13 cfm ( 31.99 LPM) they like 37 lpm but the gast is full bore and is noisy and gets hot. Gunna need a different pump with higher capacity. At 45 min pump time (55 cf^3) Po-218 is 1.39 cps Po-214 is 1.20 cps . Spectrum shows they are getting close to equilibrium. At 45 min 218 is 1.42 cps 214 is 1.42 in equilibrium yet Radon still reads 4.2449E-17 pCi/ml or 4.244e-14 pCi/l . Something is not right in the calc. maybe an efficiency factor or something of the kind. At 1 hr in the 218 is 1.51 cps and 214 is 1.92 I¡¯ll have to look at the equations they are using and see if there is something I¡¯m missing. Dud
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They didn't ask me not to share this, so...
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Added Folder /AlphaBeta Spectrometry Equipment, Lab Manuals, Teachers notes etc. Educational material, By Brand/AlphaBeta Spectrometry NIM modules by Brand
#file-notice
Geo Dowell <GEOelectronics@...> added folder /AlphaBeta Spectrometry Equipment, Lab Manuals, Teachers notes etc. Educational material, By Brand/AlphaBeta Spectrometry NIM modules by Brand
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5 files uploaded
#file-notice
The following files and folders have been uploaded to the Files area of the [email protected] group. /Nucleus 5030/5030.pdf /Nucleus 5030/A198.pdf /Nucleus 5030/Alphapaper.pdf /Nucleus 5030/AlphaSpec_ENG_1.pdf /Nucleus 5030/ATGtp915-1.pdf By: Geo Dowell <GEOelectronics@...>
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Added Folder /AlphaBeta Spectrometry Equipment, Lab Manuals, Teachers notes etc. Educational material, By Brand
#file-notice
Geo Dowell <GEOelectronics@...> added folder /AlphaBeta Spectrometry Equipment, Lab Manuals, Teachers notes etc. Educational material, By Brand
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Alpha Spec air filters
Dudley said:"I used a 0.1 u Glass Fiber filter for Rn air sampling. Using a poorly select filter media will embed the Alpha in deeper layer and give you long low energy tails and poor resolution. Use the proper material." Dud, how about posting some pictures and results, so we know what to shoot for? Geo
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Smart Cam Alpha Spec
15
Geo, Did it come with a manual and Is there a calibration required. I assume the points are the alpha hits and the yellow line is the fit, but where does it report Rn and can it report Rn-222 in pCi/l? Looks interesting. I assume you were using an Eberline RAS-1 and at what flow rate did it require? Dud
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