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

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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

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MCA Functionality

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Radiation detection Nuclear power Food industry *X-ray spectroscopy Non-destructive testing Environmental analysis and monitoring Applications

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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

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Attack of the Killer Circuit!

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Baby steps

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Signal In (10 V Analog)

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Signal In (10 V Analog) Variable Gain Amplifier

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Signal In (10 V Analog) Variable Gain Amplifier

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Signal In (10 V Analog) Variable Gain Amplifier Fast Signal Bypass

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Signal In (10 V Analog) Variable Gain Amplifier Fast Signal Bypass Threshold Fast Comparator Adjustable Threshold

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Signal In (10 V Analog) Variable Gain Amplifier Fast Signal Bypass Threshold Fast Comparator Adjustable Threshold

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Signal In (10 V Analog) Variable Gain Amplifier Fast Signal Bypass Fast Comparator Adjustable Threshold Peak and Hold

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Signal In (10 V Analog) Variable Gain Amplifier Fast Signal Bypass Fast Comparator Adjustable Threshold Peak and Hold Analog to Digital Converter

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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

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PIC Clock Cycles Missed pulse??

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PIC Clock Cycles Missed pulse?? Actually, no. Hardware counter Limit processing time by using analog circuitry

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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

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Coincidence / Anticoincidence Primary Signal Secondary Signal Coincidence Anticoincidence Always need to reset peak and hold

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Full System

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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

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Onboard Histogram Stores data on PIC Detection system ADC Histogram Allows us to count quickly without having to send data quickly

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Ready? USB Wait send data wait Sends ~1 kB every time Full-speed bulk transfer HistogramsEndpoint Buffers Packet FormationBuffer Descriptors USB SIE

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Incoming data Histogram File I/O Flux Plot Host Application

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GUI

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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

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Final Deliverables An MCA A UV Flux Monitor Software to control these two devices, and display data

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What Now? Test firmware Finish GUI Rev 2 of PCB System integration and final testing Write documentation

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Questions? Special thanks to: Steve Holt Keith Gendreau Brad Minch Gill Pratt Mihir Ravel 2008 MCA team

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