Detectors and Analog Electronics - PowerPoint PPT Presentation

Loading...

PPT – Detectors and Analog Electronics PowerPoint presentation | free to view - id: 9d327-YmEzY



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Detectors and Analog Electronics

Description:

derived from Level 2 reqs. and detector sims. Output amplifier. Resolution. Linear. Linear ... Pileup is rare due to low event rate and relatively short shaping time ... – PowerPoint PPT presentation

Number of Views:120
Avg rating:3.0/5.0
Slides: 25
Provided by: willia213
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Detectors and Analog Electronics


1
Detectors and Analog Electronics
  • Bill Crain
  • The Aerospace Corporation
  • 310-336-8530
  • Bill.crain_at_aero.org

2
Introduction
  • Design Overview
  • Requirements Flowdown
  • Detector Specification
  • Signals, Noise, and Processing
  • Board Descriptions
  • Interface Block Diagram
  • Power Consumption
  • Trade Studies
  • Summary

3
Detector Electronics Design Overview
  • Detector electronics comprised of two board
    designs
  • Detector Boards in Telescope assembly
  • Analog Processing Board (APB) in E-box
  • Heritage approach from Polar CEPPAD/IPS unchanged
    from proposal
  • Linear pulse processing system utilizing Amptek
    hybrids
  • Circuits re-designed for CRaTER requirements
  • Functional requirements summary
  • Measure LET of high LET particles in thin
    detectors
  • Measure LET of low LET particles in thick
    detectors
  • Provide good resolution for TEP effects
  • No fast timing requirements
  • Robust to temperature drift and environments

4
Analog Signal Flow Diagram
  • Single fixed gain, linear transfer function
  • All detector channels use same topology
  • Differences in preamp input transistor, detector
    biasing, and gain settings are made to optimize
    thin and thick channels

5
Requirements Flowdown
  • Electronics reqs. derived from Level 2 reqs. and
    detector sims.

6
Detector Specification (1)
  • Micron Semiconductor Limited
  • Lancing Sussex, UK
  • 20 years experience in supplying detectors for
    space physics
  • CEPPAD, CRRES, WIND, CLUSTER, ACE, IMAGE, STEREO,
    and more
  • Detector Type
  • Ion-implanted doping to form P junction on
    N-type silicon
  • Very stable technology
  • Advantages to science include good carrier
    lifetime, stable to environmental conditions, and
    thin entrance windows

7
Detector Specification (2)
  • Circular detectors having active area of 9.6 cm2
  • Two different detector thicknesses thin and
    thick
  • note state-of-the-art is 20um for thin and
    2,000um for thick detectors
  • Guard ring on P-side to improve surface
    uniformity
  • Very thin dead layers (windows) reduce energy
    loss, lower series resistance, and reduce noise

8
Detector Specification (3)
  • Detector drawings (Micron)

9
Detector Specification (4)
  • ISO9001
  • Full traceability and serialization
  • Travelers maintained
  • Verification and test prior to detector shipment
  • Random vibration test
  • Thermal cycling and thermal vacuum
  • Stability
  • Test criteria
  • Leakage current
  • I-V characteristic
  • Alpha resolution / pulser noise measurement
    (final test)

10
Proton Energy Deposition Simulations
Reference M. Looper
GEANT4
Thin 150MeV incident E
Thick 150MeV incident E
Thin 1000MeV incident E
Thick 1000MeV incident E
11
Iron Energy Deposition Simulation
Reference J.B. Blake
12
Signal Characteristics
13
Signal Processing (1)
  • Combined dynamic range of thin/thick pair is
    5,000
  • Thin threshold to provide overlap with thick
    range
  • Thin Detector Signal
  • Preamp input stage designed for 97 charge
    collection
  • High gain input jFET to raise dynamic input
    capacitance
  • 4 drift in operating point will result in 0.1
    in output peak (lt 1 bit)
  • Large feedback capacitance needed to handle Fe
    deposit
  • Preamp compensation to maintain closed-loop
    stability
  • Thick Detector Signal
  • Not as sensitive to detector capacitance
  • Design for low noise to maintain reliable 200 KeV
    low threshold and achieve lt 1-bit resolution

14
Noise Model (1)
Reference Helmuth Spieler IFCA Instrumentation
Course Notes 2001
15
Noise Model (2)
16
Signal Processing (2)
  • Noise dominated by detector leakage and input
    jFET
  • Shaping time for both thin and thick detectors
    set at thick optimum point
  • 1 usec
  • Compatible with A/D signal acquisition timing
  • 3-pole gaussian shaping improves symmetry and
    2-complex poles shortens tail
  • Shaping reduces noise but also impacts signal
    level
  • S/N at thick detector threshold for this design
    4
  • Translates to a noise occupancy in the
    coincidence window of lt 0.1 for time period not
    greater than shaping time

17
Signal Processing (3)
  • Other factors affecting noise performance
  • Bias resistor sized to minimize voltage drop
    (i.e., maintain stable operating point)
  • Detector shot noise doubles every 8 C
  • Beneficial to operate cold preferably below 20 C

18
Signal Processing (4)
  • Pileup is rare due to low event rate and
    relatively short shaping time
  • Exception occasional periods of high ESP flux
  • Leading edge trigger technique causes timing
    uncertainty but coincidence window is large by
    comparison
  • Amplified low-level discriminator available to
    reduce walk
  • Ballistic deficit is not an issue due to short
    collection times relative to peaking time of
    shaper
  • Output voltage scaled for A/D input
    specifications

19
Detector Board
  • Thin/thick detector pair use same design topology
  • Signal collected on P-contact
  • Negative bias
  • Guard signal shunted to ground
  • No guard leakage noise
  • AC coupling to isolate DC detector leakage
    current
  • Low noise / high gain JFET input stage

20
Analog Processing Board
  • Single board in E-box contains 3 thin and 3 thick
    detector processing channels
  • Flight proven pulse processing components
  • Amptek A250 preamp hybrid utilizing external jFET
    on detector board
  • Shaping amps use Amptek A275 for active filtering
  • Baseline restorer, Amptek BLR1, compensates for
    baseline shifts on interface to A/D
  • Pole-zero cancellation circuit for correcting
    preamp pulse decay to eliminate undershoot
  • Test pulser injects ?Q at preamp input jFET

21
Analog Interface Block Diagram
22
Power Estimate
Total estimated power dissipation is lt 1 Watt
23
Trade Studies
  • Determine if one detector board can be
    implemented instead of three
  • Determine if A250 device should be located on
    detector board
  • Determine sensitivity of APB to detector
    performance
  • Want to avoid rework of APB when
    selecting/changing detectors during development
  • Determine how best to isolate chassis noise from
    detectors and preamp

24
Summary
  • Detectors are well-established technology from
    experienced supplier
  • Detector electronics design meets requirements of
    Level 2 mission and satisfies energy deposition
    levels determined by detector/TEP simulations
  • Trade studies in progress
About PowerShow.com