Beck Lab (Whitman College) and Branning Lab (Trinity College).
We currently support 2 different versions of CCUs:
first version is based on a field programmable gate array (FPGA), basically a
programmable logic IC. The nicest thing
about this CCU is that there’s no circuit board to solder together—you buy a
preassembled development board (the DE2 from Altera) and simply download a
program onto it. The only thing you need
to build is a small adapter box to get the signals onto the board. This version also incorporates the
counting—you don’t need to buy a separate plug-in card to do that. Data streams from the CCU to the computer
over an RS232 serial interface (COM port).
Total cost for this CCU is ~$300. More info on this CCU below.
2. The second also uses an FPGA for counting, but uses discrete logic to perform the coincidence determination. It's much faster than the DE2 version, and it uses USB as the data transfer, rather than RS232. However, you need to get a board printed and solder it together. For more details on its performance, click here. (Note: this article is open access, so you don't need a subscription.) For more details on building this CCU, click here.
Our original, currently obsolete, CCU:
We have implemented a coincidence counting unit (CCU) on the Altera DE2 development and education board. The CCU takes inputs from up to four detectors, and has eight 32-bit counters that are used to count four singles counts and four arbitrary 2-, 3-, or 4-fold coincidences (coincidences are determined by switch settings on the DE2 board). The CCU has a coincidence-time resolution of less than 8 ns. Data is streamed from the CCU to a host computer over an RS232 serial interface.
The FPGA CCU is shown below.
To implement this CCU for yourself, you buy the Altera DE2, and get the design files and instructions for downloading them onto the DE2 from us. We’ll also give you the information you need to build the adapter box and use the CCU. All the info for implementing this circuit is located here. LabView code to run the CCU is here.
This CCU was largely programmed by Jesse Lord of Whitman College (now at the Univ. of Colorado).
The FPGA CCU.
webpage updated 7/26/2011
at whitman.edu (replace "at" with @)