Electronics for Nuclear Physics Why Electronics Detector Electronics

Electronics for Nuclear Physics 김상열 노티스

Why Electronics? Detector + Electronics + Analysis = Physics Detector + Electronics + = Development + Electronics + Analysis = Simulation Detector + * 매우 개인적인 의견임!! + Analysis = ? ?

Some examples

Electronics for Nuclear physics experiment Detector Bias Voltage Preamp + other Analog circuits Digitizer Data Acquisition Trigger + DSP Power Supply

Frequently used example 50 ohm input impedance Oscilloscope level trigger

Signal from detector PMT, Si. PM… : gain ~ 10^6 -> ~ 10^10 electrons/Me. V = ~n. C/Me. V Wire chamber, GEM… : gain ~ 10^2~3 -> ~ 10^6~7 electrons/Me. V = ~p. C/Me. V Photodiode, Ion chamber… : gain ~ 1 -> ~ 10^3~5 electrons/Me. V = ~f. C/Me. V

How to measure signal Typical detector’s capacitance = 10 ~ 1000 p. F and V = Q/C ~ n. C/100 p. F/Me. V = 10 V/Me. V ~ p. C/100 p. F/Me. V = 10 m. V/Me. V ~ f. C/10 p. F/Me. V = 100 u. V/Me. V

What we measure actually? When Idet(detector current) is very fast, Isig = Qdet x exp(-t/T) where T = Cd x Rm = 100 p. F x 10 Mohm = ~ ms -> very long!

Where it comes from?

Bias voltage supplier should supply If detector response time = ~ 10 ns and count rate = ~ 100 kcps PMT, Si. PM… : n. C/10 ns x 100 kcps/s = 10 u. A @ a few k. V -> 1 m. A @ k. V Wire chamber, GEM… : p. C/10 ns x 100 kcps/s = 1 u. A @ k. V(? ) Photodiode, Ion chamber… : f. C/10 ns x 100 kcps/s = ~1 n. A @ a few ~ 100 V

Preamplifier converts Idet to Voltage signal.

Take a look at PMT oscilloscope shot again

Opamp basics

Current Sensitive Preamp

Charge Sensitive Preamp

Shaping Amplifier

Discriminator Leading edge discriminator Constant fraction discriminator

Analog to Digital Converter Peak sensing ADC Charge sensing ADC Flash ADC

ADC sampling

Time to Digital Converter Direct counting Resolution ~ 1 ns Time stretching Resolution ~ 10 ps

Time to Digital Converter Time interpolation Resolution ~ 10 ps Multi-hit TDC Pulse shaping TDC : resolution ~ 10 ps, multi-hit

Trigger

Trigger by combination

Data Acquisition Standard DAQ

Data Acquisition Ethernet : 125 MB/s max, ~30 MB/s typically USB : 500 MB/s max, ~100 MB/s typically PCI : 63 GB/s max, ~? ? ? typically

Power Supply

Example of electronics board