Multichannel Analyzer (MCA) Raphael Cherney Dan Elg Sam Sun Chen Wang
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- 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
- Slide 31