Radiation Detectors and Signal Processing

Helmuth Spieler

Lecture Notes - VII. Heidelberger Graduate Lectures in Physics

University of Heidelberg -- Oct. 8 - 12, 2001

(files in PDF format)

    I. Introduction (3.6MB)

    1. Why? 2
    2. Examples
    Astronomical Imaging 7
    Medical Imaging - Positron Emission Tomography 15
    X-Ray Fluorescence 22
    Vertex Detection in High-Energy Physics 28
    Failure Analysis in Si Integrated Circuits 33
    Detection of Gravity Waves 35
    3. The Problem 37
    4. Example Measuring System 45

    II. Signal Formation and Detection Thresholds (1.4MB)

    1. Detector Models 2
    Direct and Indirect Detection 3
    Detector Functions 5
    Example Detector Models 6
    2. The Signal 13
    Elementary Excitations
    Band structure in crystals 14
    Detector Sensitivity 20
    Signal fluctuations - the Fano factor 25
    3. Signal Formation 30
    Example: semiconductor detectors 31
    Formation of a High-Field Region 34
    Charge Collection 51
    Time Dependence of the Signal Current 58
    Induced charge - Ramo’s theorem 60
    4. Signal Acquisition 77
    Amplifier Types 77
    Active Integrator - Charge-Sensitive Amplifiers 81
    ...Calibration 83
    Realistic Charge-Sensitive Amplifiers 84
    Input Impedance of a Charge-Sensitive Amplifier 88
    Time Response of a Charge-Sensitive Amplifier 89
    A1 Appendix: Equivalent Circuits 91

    III. Electronic Noise (184kB)

    1. Why? 2
    2. What Determines Resolution? 4
    3. Basic Noise Mechanisms 7
    Thermal Noise in Resistors 8
    Shot Noise 9
    Derivation of thermal noise spectral density 10
    Derivation of shot noise spectral density 12
    "Noiseless" Resistances 13
    Noise Characteristics 15
    4. Noise in Amplifiers 17
    Amplifier Noise Model 18
    Noise Bandwidth vs. Signal Bandwidth 22
    Amplifier Noise Matching 23
    Noise Measures (noise resistance, temperature and energy) 26
    S/N with Capacitive Signal Sources 30
    Charge-Sensitive Preamplifier Noise vs. Detector Capacitance 34
    Quantum noise limits in amplifiers 37

    IV. Signal Processing (1.8MB)

    1. Continuous Signals 3
    2. Pulsed Signals 7
    Simple Example: CR-RC Shaping 9
    Pulse Shaping and Signal-to-Noise Ratio 10
    Ballistic Deficit 16
    3. Evaluation of Equivalent Noise Charge 17
    Analytical Analysis of a Detector Front-End 19
    Equivalent Model for Noise Analysis 20
    Determination of Equivalent Noise Charge 26
    CR-RC Shapers with Multiple Integrators 30
    Examples 32
    4. Noise Analysis in the Time Domain 42
    Quantitative Analysis of Noise in the Time Domain 51
    Correlated Double Sampling 52
    5. Detector Noise Summary 62
    6. Rate of Noise Pulses in Threshold Discriminator Systems 67
    7. Some Other Aspects of Pulse Shaping
    Baseline Restoration 74
    Pole-Zero Cancellation 76
    Bipolar vs. Unipolar Shaping 77
    Pulse Pile-Up and Pile-Up Rejection 78
    Delay Line Clipping 82
    8. Timing Measurements 84
    9. Digitization of Pulse Height and Time - Analog-to-Digital Conversion 102
    A/D Parameters 103
    A/D Techniques 113
    Time Digitizers 118
    9. Digital Signal Processing 122

    V. Amplifying Devices and Microelectronics (1.8MB)

    1. Bipolar Transistors 2
    Bipolar transistors in amplifiers 7
    2. Field Effect Transistors 16
    Junction Field Effect Transistors (JFETs) 16
    Metal Oxide Semiconductor FETs (MOSFETs) 24
    MOSFETs in amplifiers 34
    3. Noise in Transistors 38
    Noise in Field Effect Transistors 38
    ...Optimization of Device Geometry 42
    Noise in Bipolar Transistors 48
    Noise Optimization - Capacitive Matching 56
    Optimization for Low Power 61
    4. SQUIDs 68
    SQUID Noise 71
    5. Microelectronics 74
    Fabrication of Semiconductor Devices 74
    Integrated Circuits 85
    LBNL Microsystems Laboratory 89

    VI. Detector Systems - Conflicts and Compromises (1.6MB)

    1. Conflicts 2
    2. CDF Vertex Detector Upgrade 3
    3. BaBar Silicon Vertex Tracker 9
    3. Development of a Tracker Concept at the LHC 17
    Environment and Requirements 17
    Layout 24
    Strip Readout Architecture 29
    ...Required signal-to-noise ratio 30
    ...Prototype results 34
    Two-Dimensional Detectors 38
    ATLAS Pixel System 40
    Advantages of pixels at LHC 46

    VII. Why Things Don’t Work or Why S/N Theory Often Seems to be Irrelevant (297kB)

    1. Common Types of Interference 3
    2. Shielding Techniques 7
    Contiguous Shielding 7
    Field Line Pinning 10
    Self-Shielding Structures 11
    3. Shared Current Paths 12
    4. Remedial Techniques 15
    Breaking Parasitic Signal Paths 16
    Direct Current from Sensitive Nodes 21
    "Ground" Connections in Multi-Stage Circuits 26
    The Folded Cascode 27
    5. System Considerations 31
    Choice of Shaper 31
    Connections in Multi-Channel Systems 32
    "Self-Shielding" Cables 37
    6. Closing Remarks 38

    VIII. Detectors and Cosmology (7.9MB)

    1. Introduction 2
    2. CMB Experiments 3
    3. Examples of Existing CMB Arrays
    MAXIMA 5
    SuZIE 8
    4. Cryogenic Detector Arrays 12
    Detector Sensitivity 13
    Thermal Detectors 16
    Noise Optimization 19
    Heat Capacity 21
    Signal Fluctuations 22
    Voltage-Biased Transition Edge Sensors 25
    Monolithic Fabrication of TES Arrays 31
    Readout 36
    ...Signal Summing Schemes 38
    ...Cross Talk 40
    ...Demodulation 42
    ...Some Challenges 44
    5. Summary 48
    6. Outlook 49