Multichannel Analyzer (MCA)
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Multichannel Analyzer (MCA). Raphael Cherney Dan Elg Sam Sun Chen Wang. Background: X-ray Detection. X-ray photons. V signal. X-ray Detector. Amplifier. NASA’s detectors can “see” individual X-ray photons Photon  V pulse Height proportional to energy

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Multichannel Analyzer (MCA)

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Multichannel analyzer mca

Multichannel Analyzer (MCA)

  • Raphael Cherney

  • Dan Elg

  • Sam Sun

  • Chen Wang


Multichannel analyzer mca

Background: X-ray Detection

X-ray photons

Vsignal

X-ray Detector

Amplifier

  • NASA’s detectors can “see” individual X-ray photons

  • Photon  Vpulse

    • Height proportional to energy

  • Our MCA measures the pulse heights and their times of arrival

MCA


Multichannel analyzer mca

MCA Functionality


Multichannel analyzer mca

Applications

  • Radiation detection

  • Nuclear power

  • Food industry

  • *X-ray spectroscopy

  • Non-destructive testing

  • Environmental analysis and monitoring


Multichannel analyzer mca

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

vpulse

tpulse

t


Multichannel analyzer mca

Attack of the Killer Circuit!


Multichannel analyzer mca

Building an MCA

Baby steps…

Circuits can be fun!


Multichannel analyzer mca

Signal In

(10 V Analog)


Multichannel analyzer mca

Signal In

(10 V Analog)

Variable Gain Amplifier


Multichannel analyzer mca

Signal In

(10 V Analog)

Variable Gain Amplifier


Multichannel analyzer mca

Fast Signal Bypass

Signal In

(10 V Analog)

Variable Gain Amplifier


Multichannel analyzer mca

Fast Signal Bypass

Threshold

Signal In

(10 V Analog)

Variable Gain Amplifier

Adjustable

Threshold

Fast Comparator


Multichannel analyzer mca

Fast Signal Bypass

Threshold

Signal In

(10 V Analog)

Variable Gain Amplifier

Adjustable

Threshold

Fast Comparator


Multichannel analyzer mca

Fast Signal Bypass

Signal In

(10 V Analog)

Adjustable

Threshold

Variable Gain Amplifier

Fast Comparator

Peak and Hold


Multichannel analyzer mca

Fast Signal Bypass

Signal In

(10 V Analog)

Adjustable

Threshold

Variable Gain Amplifier

Fast Comparator

Analog to Digital Converter

Peak and Hold


Multichannel analyzer mca

Fast Signal Bypass

PIC

Signal In

(10 V Analog)

Pulse Counter

Adjustable

Threshold

Peak Value

Variable Gain Amplifier

Fast Comparator

Analog to Digital Converter

Peak and Hold


Multichannel analyzer mca

PIC Clock Cycles

  • Missed pulse??


Multichannel analyzer mca

PIC Clock Cycles

  • Missed pulse??

  • Actually, no.

    • Hardware counter

    • Limit processing time by using analog circuitry


Multichannel analyzer mca

Signal In

(10 V Analog)

PIC Processor

D-type Flip-Flop

Adjustable

Threshold

Signal Latch

Pulse Counter

Peak Value

Fast Comparator

Analog to Digital Converter

Peak and Hold


Multichannel analyzer mca

Coincidence / Anticoincidence

Primary Signal

Secondary Signal

  • Always need to reset peak and hold

Coincidence

Anticoincidence


Multichannel analyzer mca

Full System


Multichannel analyzer mca

Threshold

Baseline

Reset

Reset

Zoom-in

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

Timing Diagram

1 horizontal unit = 5 clock cycles = 250 ns


Multichannel analyzer mca

Onboard Histogram

  • Stores data on PIC

  • Detection system  ADC  Histogram

  • Allows us to count quickly without having to send data quickly


Multichannel analyzer mca

USB

  • Wait  send data  wait

  • Sends ~1 kB every time

  • Full-speed bulk transfer

Packet Formation

Buffer Descriptors

USB SIE

Histograms

Endpoint Buffers

Ready?


Multichannel analyzer mca

Host

Application

Histogram

Incoming data

Flux Plot

File I/O


Multichannel analyzer mca

GUI


Multichannel analyzer mca

UV Flux Monitor

  • Photodiode outputs current according to flux

  • Converted into voltage, read by PIC

  • Uses onboard PIC ADC

UV Light

Isignal

Vsignal

Current-to-

Voltage

Converter

UV Photodiode

PIC


Multichannel analyzer mca

Final Deliverables

  • An MCA

  • A UV Flux Monitor

  • Software to control these two devices, and display data


Multichannel analyzer mca

What Now?

  • Test firmware

  • Finish GUI

  • Rev 2 of PCB

  • System integration and final testing

  • Write documentation


Multichannel analyzer mca

  • Special thanks to:

  • Steve Holt

  • Keith Gendreau

  • Brad Minch

  • Gill Pratt

  • Mihir Ravel

  • 2008 MCA team

Questions?


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