New MCA

[Carl Willis]

I have just massively upgraded my pulse-height analysis equipment, thanks to some throwaway NIMs and some wonderful open-source software.

The new system comprises a Canberra 556 AIM module and a Canberra 9635 ADC (both single-width NIMs). These modules and their relatives from Canberra's proprietary-standard "ICB" NIM family are often on eBay or in other surplus quite inexpensively, and I'm guessing it is because people do not know how to use them or assume that the Canberra Genie(R) software is needed to operate them. Indeed this was my initial assessment of the package, but I'm not one to turn down good loot. It turns out that (A) the cabling needed to attach the ADC to the AIM is straightforward; (B) all you need to get the AIM connected to a PC via ethernet is a cheap IEEE 802.3 to 10-BASE-T transceiver; and the real kicker is that (C) there is FREE, OPEN-SOURCE SOFTWARE available to collect real-time data from Canberra AIM modules.

Let me just describe in briefest terms how the 9635 ADC stacks up against some other ADCs I have experienced in hobby settings. The conversion time is calculated for the photopeak of the spectrum shown, in hypothetical channel 1076 (provided the unit has enough memory). Conversion time is inversely proportional to the maximum count-rate the ADC can process.

ADC / MCA...........................Memory.........................Circuit...............Conversion time

Tracor-Northern 1705.............1023.....................50 MHz Wilkinson...........(20 us)
Canberra 35 Plus....................4096....................100 MHz Wilkinson..........10 us
SpecTech UCS30...................4096....................(Fixed-time ADC).............10 us
Canberra 9635........................8192....................(Fixed-time ADC).............0.9 us

Another way of looking at this is that the 35 Plus and Spectrum Techniques UCS30 would be able to beat the 9635 in count-rate capability only if the peak in question were placed below Channel 96 in those units.

The software I needed to put on my Windows computer was the following, all of it free:

-Cygwin/X (Linux emulator)
-IDL Virtual Machine
-Dr. Mark Rivers' "mca" binaries, here:
http://cars.uchicago.edu/software/pub/mcaPrebuilt.tgz
-EPICS binaries for Windows, here:
http://cars.uchicago.edu/software/pub/E ... naries.zip
-Dr. Mark Rivers' MCA GUI for IDL, here:
http://cars.uchicago.edu/software/pub/idl_mca.tar


I'll give a fuller set of instructions on my blog sometime soon. But for now I will say that I'm incredibly indebted to the hard work of Dr. Rivers and all the other contributors to this fine open-source software, especially the EPICS system. Setup could be a little hairy for some, but the end result is a real-time graphical interface to a top-quality MCA, for ultracheap. The pic just shows this software running, with a Cs-137 spectrum on a 2" NaI(Tl) detector with about 5% resolution.

-Carl

[Jon Rosenstiel]

Very nice Carl, thanks for the report.

Jon R

[Starfire]

A nice catch Carl - and in your hands this instrument will be tasked to peak performance. Good luck with the find.

[Richard Hull]

Very sweet! As my old pal and tesla coil buddy, Bill Richards would say... "nice stuff".
I know the pleasure of bringing stuff up from scratch and having it do well. You can be proud in addition to being gratified by your efforts.

Richard Hull

[Carl Willis]

Hi Richard,

I think I saw a Canberra 8xxx series ADC in your NIM bin upstairs, and someone had written software to read its data via parallel port?

I'm almost certain that the AIM module I have is compatible with that model of ADC, among numerous others. Maybe keep your eyes peeled for an AIM unit, which will almost surely act as a much better buffer memory than the PC-via-parallel port.

-Carl

[Richard Hull]

Carl, I will keep my eyes peeled for the AIM unit.

I can't remember the number of the Canberra ADC in my bin right now. I thought it was an 875.

My pal Craig Brown wrote the software for the thing and it worked OK but not quite as well and my 35 system, which I still use. I am always ready to bo better, of course.

Richard Hull

[David D Speck MD]

Richard,

Could you provide links to Craig Brown's DOS software and hardware interface to the older style NIM ADC cards? I've had no luck finding the info, though I know I saw it in the past.

Thanks,

Dave Speck

[Steven Sesselmann]

Carl,

What is the anomalous bump in the 32 kev x-ray?

Steven

[Larry Upjohn]

Carl;
I wanted ask how vital is the IDL virtual machine for using the rest of the MCA package. I seem to be blocked from downloading the IDL virtual machine from the home website.
I have an older Nuclear Data MCA that is already microprocessor controlled. The electronics contained there in is essentially the ND NIM cards with an old bit slice AMD chipset to collect, bin and transmit the data via an RS-232 port. I have the original DOS software however the media (3.5 floppy disks) have developed dropouts and the software no longer will install or run. I did archive to hard drive some time ago but that old DOS system died taking the hard drive with it. The MCA does respond to serial commands from TeleTerm emulator but some of the higher level analysis and plotting software is needed to make it pretty. This software you present in this thread appears as though I may be able to adapt it for my existing NIM stuff.
I have tried the PRA software with my existing sound cards and it does not have the refinement of the old ND system I am seeking to up grade. I know that this thread is somewhat older so hopefully this will not be inconvenient for follow up. More later, Larry Upjohn.

[David Housley]

In my next life, I want to come back as Carl. He always sets the bar high for everyone to aspire to. Good job, Carl--I always relish your posts as prime meat in these forums. Thanks!

[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]

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

-Carl

[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]

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