How can I display a charge spectrum from data acquired from an photon detection device?

[RonMusser]

Hello everyone,

I currently building an application that allows me to aquire data from a photon detector (SiPM) and display the information in the form of a charge spectrum. I am running LabVIEW and I also have a NI 2GS/s Digitizer. My problem is that I can only obtain the voltage from the digitizer and I do not know how to convert this voltage information into a charge spectrum. I am sure the answer to my question is obvious but I am stuck. Any hints, pointers, or directions would be greatly appreciated.

Thank you very much,

Ronald

[Henrik_Volkers]

Usually, you measure a voltage that is propotional to a (PM)current measured over a resistance (usually 50Ohm) or a fast TIA.

Charge is the integral of current.  I'm not a ionisation counting guy...  the spectra I have seen where realised by two methods:

Capture the peak voltages and classify them (make a histogram of 256 bins with a 8bit ADC)  or for higher resolution: measure the area (integral) of each spike and build a histogram  (and I'm shure more sophisticated methods will do some fitting of the pulse shape including the information of the system response of the SiPM+Amp+DAQ .....)

The WWW can give much more detailed answers to this question 😉

[RonMusser]

Thank you for the suggestion.

Ronald

[djs_at_eaton]

Does the detector manufacturer have documentation that would help?  I'd start there.  The manufacturer typically publishes instructions or functions relating the output to input.  I'm worried that the output is related to energy, not charge.  Maybe the voltage / current output tells you the energy and charge determines the signal polarity.  Talk to the guys who designed the equipment.  When I studied Physics photons didn't carry charge.