Olin Student Projects 2008 Keith Gendreau Code 662 NASA/GSFC

A PIC Microcontroller Based Pulse Detection and Measurement System Take an input analog signal, look for pulses above a threshold, detect the peak voltage of each pulse, digitize the peak voltage, write to a file the pulse time and peak pulse height, continue…. Build on last year’s “Flux Meter”, if possible.

X-ray Detection and Pulses X-ray DetectorAmplifier V signal X-ray photons X-rays pack a lot of energy. X-ray detectors see individual X-ray photons. If the detectors and electronics are good enough, they can determine the energy of the photon. Science is to be gained by the energy of the photons.

Pulses on an analog signal (from an X-ray detector) V t t pulse v pulse Pulse widths: ~25 ns- 2µsec V t v thresh Pulse#1Pulse#2 Pulse#3 V pulse is proportional to Energy of photon Noise pulses?

Desired Layout: Top view Olin Pulse Height Box Analog signal From X-ray Detector On a BNC Connector Knob for Additional gain Knob for Lower Voltage Threshold USB Output Computer With Olin Software To display/save Events Any type of computer, PC or Mac (I prefer Mac, but whatever is doable)

Requirements Must handle pulses ranging from ~< 100 nsec to ~ 100 microsec wide Goal of achieving ~10 6 counts per second (typically, it is much less than this, I’d be happy with ~10 4 cps) Should be able to handle pulseheights ranging from ~0 to 10 volts (positive).

Output Desires ASCII file with time and pulseheight for each event above threshold Plot with histogram of pulseheights Flux vs time (like on the flux meter) Be creative. TCP/IP port? eg, The computer reading the instrument can make the data available as a server to others as client computers via a TCP/IP Sockets protocol Would be an extremely useful feature for beamline work.

From This is a circuit design I found that can detect a pulse peak And hold the pulse long enough for a slow ADC to measure the peak voltage. It can then be reset to detect the next pulse after the measurement has been made. ** just a suggestion, maybe other things exist… This one should be fast, though…

Other parts A threshold comparator A gain circuit to provide additional signal amplification if necessary A PIC microcontroller to digitize the voltage, control the peak detector circuit, and communicate the results to computer via USB. (Maybe build on last year’s “Flux meter” Project?)

How to proceed? Use a signal generator to produce simulated X-ray pulses that would come out of a detector… –Easy to control pulse width, rate, and pulse height Easier than using a detector.. Toward last weeks of project, I will send you a detector to try instead of the signal generator