MCA: Multichannel Analyzer


The MCA team aims to design and build a low-cost Multichannel Analyzer. Our MCA will take in a voltage signal with pulses and record these pulses on the computer. The device will be complemented with software that connects to our hardware and communicates with it via USB. This program will display a real-time spectrum and flux plot of the incoming voltage pulses. Current MCAs sell for hundreds or thousands of dollars; our target cost is $25.

What is an MCA?

Scientists at NASA-Goddard Space Flight Center need to monitor x-ray emission at points along a beamline. A multichannel analyzer is a device used for analyzing the output of a detector - in our case, an x-ray detector. By analyzing the timing and amplitude of pulses produced by a detector, it enables its users to characterize the flux and spectrum of a radiation source.

Where the MCA Fits In

The role of the MCA and the detection process are illustrated above. The detection process is:

  1. Incoming x-rays are exposed to a detector
  2. These x-rays impact an avalanche photodiode sensitive to x-rays, which is shown above with an amplifier.
  3. The detector produces voltage pulses with height related to the energy of the source x-rays
  4. The MCA hardware captures information about the pulse. It records the time between successive pulses, and uses a peak and hold circuit to capture the height of each pulse. Optionally, if only flux information is desired, the MCA can switch to a low height resolution mode.
  5. Using full-speed USB, the MCA hardware sends pulse time and height information to a host computer, along with a periodic pulse count.
  6. A computer interface produces a flux plot and histogram of the output, and allows the user to configure the MCA.

The MCA project is making progress, and it will eventually be recorded here. Please contact jeff (at) if you have any questions about this project in the meantime.