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

2. Background: X-ray Detection X-ray DetectorAmplifier V signal X-ray photons MCA NASA’s 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

3. MCA Functionality

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

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

6. Attack of the Killer Circuit!

7. Baby steps…

8. Signal In (10 V Analog)

9. Signal In (10 V Analog) Variable Gain Amplifier

10. Signal In (10 V Analog) Variable Gain Amplifier

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

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

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

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

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

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

17. PIC Clock Cycles Missed pulse??

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

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

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

21. Full System

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 μs to sample Threshold Baseline Timing Diagram Reset

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

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

25. Incoming data Histogram File I/O Flux Plot Host Application

26. GUI

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

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

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

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