Connects directly to PMT probe shown in the book’s Figure 30 with no need for PMT amplifier!
The nice guys at the Yahoo GammaSpectrometry Group developed multichannel analyzer software for the $79 SainSmart DSO201 Pocket-Sized Digital Oscilloscope. The upload of the MCA software to the oscilloscope is really easy (via USB), and it allows the PMT probe shown in the book’s Figure 30 to be connected directly to the oscilloscope’s input with no need for a PMT amplifier!
This is a very easy and inexpensive way to conduct the single-photon detection experiments of the book’s Chapter 2, as well as the Compton Scattering experiment in Chapter 5. The setup makes for a great general-purpose radiation spectrometer for the identification of gamma-emmiting isotopes.
The Sain Smart DSO201
The Sain Smart DS0201 is a pocket-size digital storage oscilloscope based on an ARMCortex™-M3 compatible 32-bit platform, equipped with a 320×240 color display, SD card capability, USB connection, and USB-rechargeable batteries that provide over 2 hours of operation. In the US, Sain Smart sells through Amazon (mine came in just one day although I chose free shipping!)
The manual for the DSO201 is available at: DS0201_nano_Manual
The GammaGrapher V2 Software
The GammaGrapher V2 project is an open-source effort to convert a Sain Smart DSO201 Nano oscilloscope into a multichannel analyzer for gamma spectrometry. The source and binaries for GammaGrapher v2.0 are available for free download in a zip file at https://sourceforge.net/projects/gammagrapherv2/
Connecting the DSO201 MCA to the PMT Probe
This is easy! Simply connect the oscilloscope probe that came with the DSO201 to the PMT probe’s output. Set the probe to X1. You may want to build a dedicated MCX-to-BNC cable to make this connection more suitable for field use.
PMT Probe Setup
Connect your PMT/NaI(Tl) scintillation probe to the oscilloscope. Place a Cs-137 check source close to the crystal. Power the probe (+1,250V) and tune the probe’s gain so that it produces negative-going pulses with a maximum amplitude of around 3V. If you built the probe exactly as shown in the book’s Figure 30, then the pulse width should be around 12 microseconds. Otherwise, you may need to add a simple RC low-pass filter to stretch the PMT pulses to be at least 6 microseconds wide.
Loading GammaGrapher V2 on the DSO201
1. Download the zipped file for the latest GammaGrapher V2 release from https://sourceforge.net/projects/gammagrapherv2/. Unzip the file into its own folder.
2. Connect the DSO201 oscilloscope to your Windows PC via the USB cable that comes included with the DSO201.
3. Turn off the DSO201. Press the “-” button on the DSO201, and while pressing the “-” button, turn on the DSO201. This will send the oscilloscope into a special bootloading mode:
4. An Explorer window for the DSO201’s directory should open on your Windows PC, as if you would have connected a USB drive. Its name will be something like “”DFU V3_11_A”.
5. Copy the file mca-app.hex from the \GGV2_APP\project\gcc\ directory in the folder that you created by unzipping the GammaGrapher .zip file into the DSO201’s directory. The DSO201’s Explorer window will close, and after a few seconds reopen to show the mca-app file with its extension renamed to .rdy.
6. Now copy the file mca-lib.hex from the \GGV2\GGV2_LIB\project\gcc\ directory in the folder that you created by unzipping the GammaGrapher .zip file into the DSO201’s directory. The DSO201’s Explorer window will close, and after a few seconds reopen to show the mca-lib file with its extension renamed to .rdy.
7. Turn off the DSO201, and then turn it back on. GammaGrapher’s welcome screen will be displayed. Congratulations! You now have a $79 Multichannel analyzer!
Freeware Gamma Grapher MCA with diy PMT Scintillation Probe by David and Shanni Prutchi diyPhysics.com
By the way, if you want to return the oscilloscope to its original firmware, upload the files from:
“Hex-files for reflashing scope-firmware 2.6 and BenF 3.64” available to Yahoo GammaSpectrometry Group members at: http://tech.groups.yahoo.com/group/GammaSpectrometry/files/Gamma%20Grapher%20Version%202/
MCA Setup
Press the “M” button on the DSO201 and set the following parameters:
INPUT SIGNAL SETUP:
-
Pulse: Pos | Neg = 1
-
Gaussian Approx: FALSE
-
dv/dt Thres: -200.000
-
Low Limit: -4.000 kev
-
High Limit: 2046.000 kev
-
Range +/-: 4.000 v
Then go up the menu to “Clear All” and press one of the horizontal cursor keys (|<< or >>|). Press M to exit the menu. You should now see the spectrum building up on the screen. The following shows a screen shot of the unit displaying the spectrum of a Cs-137 check source using these settings:
Advanced Setup
To access the design files (and hopefully to participate in the development) you will need to join the GammaSpectrometry Yahoo Group (free membership). Join through: http://groups.yahoo.com/ Read the posts and experiment with calibrating your probe to yield high-resolution spectra that reads correctly in keV.