Multichannel Analyzer (MCA) • Raphael Cherney • Dan Elg • Sam Sun • Chen Wang
Transcript
Slide 1
Multichannel Analyzer (MCA) Raphael Cherney Dan Elg Sam Sun
Chen Wang
Slide 2
Background: X-ray Detection X-ray DetectorAmplifier V signal
X-ray photons MCA NASAs detectors can see individual X-ray photons
Photon V pulse Height proportional to energy Our MCA measures the
pulse heights and their times of arrival
Slide 3
MCA Functionality
Slide 4
Radiation detection Nuclear power Food industry *X-ray
spectroscopy Non-destructive testing Environmental analysis and
monitoring Applications
Slide 5
Our Task Build a $25 multichannel analyzer Handle pulses
ranging from 100 ns to 100 us (Require 1-50 us) 100,000 counts per
second (Require 1000 pulses) Handle pulse height from 0V to 10V
Output ASCII file with time and pulse height Create histogram of
pulse heights V tt pulse v pulse
Slide 6
Attack of the Killer Circuit!
Slide 7
Baby steps
Slide 8
Signal In (10 V Analog)
Slide 9
Signal In (10 V Analog) Variable Gain Amplifier
Slide 10
Signal In (10 V Analog) Variable Gain Amplifier
Slide 11
Signal In (10 V Analog) Variable Gain Amplifier Fast Signal
Bypass
Slide 12
Signal In (10 V Analog) Variable Gain Amplifier Fast Signal
Bypass Threshold Fast Comparator Adjustable Threshold
Slide 13
Signal In (10 V Analog) Variable Gain Amplifier Fast Signal
Bypass Threshold Fast Comparator Adjustable Threshold
Slide 14
Signal In (10 V Analog) Variable Gain Amplifier Fast Signal
Bypass Fast Comparator Adjustable Threshold Peak and Hold
Slide 15
Signal In (10 V Analog) Variable Gain Amplifier Fast Signal
Bypass Fast Comparator Adjustable Threshold Peak and Hold Analog to
Digital Converter
Slide 16
Signal In (10 V Analog) Variable Gain Amplifier Fast Signal
Bypass Fast Comparator Adjustable Threshold Peak and Hold Analog to
Digital Converter PIC Pulse Counter Peak Value
Slide 17
PIC Clock Cycles Missed pulse??
Slide 18
PIC Clock Cycles Missed pulse?? Actually, no. Hardware counter
Limit processing time by using analog circuitry
Slide 19
Peak and Hold Fast Comparator Signal In (10 V Analog)
Adjustable Threshold Analog to Digital Converter D-type Flip- Flop
Pulse Counter PIC Processor Peak Value Signal Latch
Slide 20
Coincidence / Anticoincidence Primary Signal Secondary Signal
Coincidence Anticoincidence Always need to reset peak and hold
Slide 21
Full System
Slide 22
Signal Peak-and- Hold Comparator D Flip-flop ADC 1 horizontal
unit = 5 clock cycles = 250 ns After detecting rising- edge of
comparator, count x (in this case 5) clock pulses, then enable ADC
Assuming 800 kcps, the ADC takes 1.25 s to sample Threshold
Baseline Timing Diagram Reset
Slide 23
Onboard Histogram Stores data on PIC Detection system ADC
Histogram Allows us to count quickly without having to send data
quickly
Slide 24
Ready? USB Wait send data wait Sends ~1 kB every time
Full-speed bulk transfer HistogramsEndpoint Buffers Packet
FormationBuffer Descriptors USB SIE
Slide 25
Incoming data Histogram File I/O Flux Plot Host
Application
Slide 26
GUI
Slide 27
UV Flux Monitor UV Photodiode Current-to- Voltage Converter V
signal UV Light PIC Photodiode outputs current according to flux
Converted into voltage, read by PIC Uses onboard PIC ADC I
signal
Slide 28
Final Deliverables An MCA A UV Flux Monitor Software to control
these two devices, and display data
Slide 29
What Now? Test firmware Finish GUI Rev 2 of PCB System
integration and final testing Write documentation
Slide 30
Questions? Special thanks to: Steve Holt Keith Gendreau Brad
Minch Gill Pratt Mihir Ravel 2008 MCA team