New MCA

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Carl Willis
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Re: New MCA

Post by Carl Willis »

Steven: I don't know specifically what the ~32-keV peak is, although I presume it is a fluorescence x-ray from either the Cs-137/Ba-137 itself, or the surroundings (check the decay data, Cs-137 has some k-alpha lines down there that show up in moderate yield). One of the problems with scintillation detectors is the poor energy resolution at low energies, which makes analysis of these kinds of features an exercise in conjecture most of the time.

Larry: I no longer use IDL, MEDM, and Mark Rivers' visualization app. Instead, I use the CALab module for EPICS in conjunction with my own LabVIEW VI that also operates the features of the amplifier and ADC. I can email a stand-alone executable (some features of my program are unlikely to work for other users with different equipment) or the LabVIEW VI itself. It's not something I support or troubleshoot since other peoples' setups vary, but it would make a good starting point for making your own MCA emulator based on the Canberra 556.

-Carl
Carl Willis
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TEL: +1-505-412-3277
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Carl Willis
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Real name: Carl Willis
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Re: New MCA

Post by Carl Willis »

That's kind of you. I try to post what I value: accessible, practical, technique-oriented material.

-Carl
Carl Willis
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TEL: +1-505-412-3277
George Dowell
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Re: New MCA

Post by George Dowell »

The 32 keV is from internal conversion (IC) of the Ba-137m. It is a combination.

repost:
Measurements always taken on the side opposite the label. Here the plastic
thickness is regulated and consistent. The label side is filled with epoxy,
therefore its shielding factor varies quite bit.

1 microCurie Cs-137 says:

2.22 X 10^6 DPM (disintegrations per minute).


For each disintegration of the Cs-137 I can expect two betas.

94.6% of the disintegration will give me a beta whose maximum energy is 511.550
keV, yielding an average energy of 156 keV.

5.4% of the disintegrations will give me a beta whose maximum energy is 1.1732
MeV, yielding an average energy of 415.2 keV.

Each disintegrations of a Cs-137 atom will yield a daughter which is Ba-137m.
Each Ba-137m will further have extra energy in the nucleus, which it promptly
releases as:

89.98% of the time it will release a 661.650 keV gammas,
3.82% of the time there will be a 32.194 keV photon due to Internal Conversion
2.07% of the time there will be a 31.8 keV photon " "
1.39% of the time there will be a 36.4 keV photon " "
1.038% of the time there will be a 4.47 keV photon " "

Photon Emission Products: Ba-137m
Fraction Energy(MeV)
0.010381 0.004470
0.013900 0.036400
0.020703 0.031817
0.038197 0.032194
0.899800 0.661650

Once this extra energy is shed, the Ba-137m becomes Ba-137 which is the stable
isotope. In my way of thinking,since there is no change of A or Z, there is no
transmutation, therefore there has been no "decay" per se. Gamma emission is not
considered a decay mode in the USA.

If for some reason i would want to calculate the doserate at a certain distance,
the microCuries would be multiplied by a Gamma Factor, sometimes called the
"Specific Gamma Exposure Rate Constant"

George Dowell
Daniel Kula
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Real name: Daniel Kula

Re: New MCA

Post by Daniel Kula »

Larry: I no longer use IDL, MEDM, and Mark Rivers' visualization app. Instead, I use the CALab module for EPICS in conjunction with my own LabVIEW VI that also operates the features of the amplifier and ADC. I can email a stand-alone executable (some features of my program are unlikely to work for other users with different equipment) or the LabVIEW VI itself. It's not something I support or troubleshoot since other peoples' setups vary, but it would make a good starting point for making your own MCA emulator based on the Canberra 556.

-Carl
[/quote]

Hello Carl,

I wonder if I may ask you a favor. Recently I obtained two pieces of Canberra 556 AIM modules and Model 9633 ADCs. I would like to use them for my amateur experiments in Gamma spectrum analysis.
Re your posts on Fusor forum (from years 2009 and 2012), you seem to have gathered quite a lot of experience with these modules. Since I have access to Labview 14 SW package, I wonder whether you would be willing to share some of your Labview .vi files for controlling these Canberra units. On Fusor forum you state you use Labview + CA Labs + EPICS.
My problem dwells in the fact I don't even have any "Programmer's Manual" for 556 AIM, that would list the commands used for the control, neither I have the list of ICB commands for 9633 ADC.
Thank you in advance for any response. And I'm sorry to bother with issue you posted on the Fusor forum such a long time ago.
Best Regards
Dan Kula
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