SR-007 September 2007 Calibration of Particle Instruments in Space Physics Editors Martin Wüest INFICON Ltd, Balzers, Principality of Liechtenstein David S. Evans Space Environment Center, NOAA, Boulder CO, USA Rudolf von Steiger International Space Science Institute, Bern, Switzerland
Contents List of Figures List of Tables Preface xi xvii xix 1 Introduction 1 1.1 Particle Environments............................ 1 1.2 Measurement Requirements........................ 1 1.3 Conversion to Physical Quantities..................... 5 1.3.1 Particle Fluxes........................... 5 1.3.2 Velocity Distribution Function................... 5 1.3.3 Moments.............................. 6 1.3.4 Gas Densities............................ 7 1.4 Required Accuracy............................. 7 1.5 Error Sources................................ 8 Bibliography................................... 10 2 Review of Instruments 11 2.1 Introduction................................. 11 2.1.1 Important Characteristics of Analyzers.............. 13 2.2 Detectors.................................. 13 2.2.1 Faraday Cups............................ 13 2.2.2 Discrete Electron Multiplier.................... 14 2.2.3 Continuous Electron Multiplier.................. 15 2.2.4 Microchannel Plates........................ 18 2.2.5 Solid-State Detectors........................ 27 2.2.5.1 Energy Loss of Particles in Matter........... 27 2.2.5.2 Silicon Solid-State Detectors.............. 29 2.2.5.3 Scintillators and Cherenkov Radiators......... 32 2.2.6 Avalanche Photo Diodes...................... 34 2.3 Langmuir Probes.............................. 34 2.3.1 Overview of the Langmuir Probe Technique............ 35 2.3.2 Types of Probes Used in Ionosphere Measurements........ 36 2.3.3 Measurement Accuracy...................... 37 2.3.4 Internal Consistency Checks.................... 37 2.3.5 Implementation Issues....................... 38 2.3.5.1 Boom Mounting..................... 38 2.3.5.2 Collector Surfaces.................... 38 2.3.5.3 Probe Contamination.................. 39 2.3.5.4 Magnetically Induced Potentials............ 39 2.3.5.5 Adaptive Circuitry.................... 39 2.3.5.6 Spacecraft Design Factors................ 40 iii
iv CONTENTS 2.3.6 Summary of Langmuir Probe Operations in Dense Plasmas.... 41 2.3.7 Langmuir Probe Measurements in Low Density Plasmas..... 41 2.4 Faraday Cups................................ 43 2.4.1 Introduction............................. 43 2.4.2 Instrument Description....................... 44 2.4.2.1 System Components................... 44 2.4.2.2 Measurement Chain................... 46 2.5 Plasma Analyzers.............................. 49 2.5.1 Introduction............................. 49 2.5.2 The Retarding Potential Analyzer................. 50 2.5.3 The Cylindrical Curved Plate Electrostatic Analyzer....... 50 2.5.4 Spherical Sector Analyzers..................... 52 2.5.5 Top-Hat Analyzers......................... 54 2.5.5.1 Spherical Top-Hat Analyzers.............. 54 2.5.5.2 Toroidal Top-Hat Analyzers............... 56 2.5.5.3 Electrostatic Deflection to Increase Field of View... 59 2.5.6 Magnetic Sector Analyzers..................... 59 2.5.7 Plasma Analyzer Summary..................... 61 2.6 Mass Spectrometers............................. 62 2.6.1 Performance Specifications..................... 62 2.6.2 Introduction to Magnetic and Electric Analyzers......... 63 2.6.2.1 Magnetic Mass Spectrometers.............. 64 2.6.2.2 Double Focusing Magnetic Mass Spectrometers.... 64 2.6.2.3 E B Instruments................... 66 2.6.3 RF Mass Spectrometers...................... 66 2.6.3.1 Quadrupole Analyzers.................. 66 2.6.3.2 Omegatrons....................... 69 2.6.3.3 Bennett Ion Mass Spectrometer............. 69 2.6.4 Time-of-Flight Analyzers..................... 70 2.6.4.1 Continuous Operation TOF............... 71 2.6.5 Linear Time-of-Flight Instruments with SSD........... 74 2.6.5.1 Gated Time-of-Flight Analyzers............ 76 2.6.5.2 Foils........................... 78 2.6.5.3 TOF Electronics..................... 78 2.7 Upper Atmosphere Neutral Gas Mass Spectrometers........... 78 2.7.1 Examples of Neutral Gas Mass Spectrometers........... 79 2.7.2 Gas Inlet.............................. 80 2.7.3 Ionization Source.......................... 82 2.7.4 Cruise Conditions......................... 83 2.7.5 Spectra............................... 83 2.8 Neutral Atom Imagers........................... 83 2.8.1 Introduction............................. 83 2.8.2 Measurement Principles...................... 84 2.8.3 Rejection of Other Signal Sources................. 84 2.8.4 ENA Measurement Techniques.................. 86 2.9 Solid-State Detector Instruments...................... 90 2.9.1 Overview.............................. 90
v 2.9.2 Solid-State Detector Telescopes.................. 90 2.10 Plasma Wave Instruments.......................... 91 2.11 Electronics................................. 94 2.11.1 Amplifier and Discriminator Operation.............. 94 2.11.2 TOF Electronics.......................... 95 2.11.3 Other................................ 97 2.12 Common Instrument Problems....................... 97 2.13 Data Handling............................... 98 2.13.1 Data Compression......................... 99 2.13.2 Transmission and Ground Processing............... 100 2.14 Conclusion................................. 101 Bibliography................................... 101 3 Calibration Techniques 117 3.1 Introduction to Calibration......................... 117 3.1.1 The Geometric Factor of Particle Instruments........... 121 3.1.2 The Generic Mass Spectrometer Response............. 125 3.1.3 Dead Time Corrections in Pulse Counting Systems........ 131 3.2 Low and Medium Energy Electron Calibration............... 134 3.2.1 Electron Sources for Instrument Calibrations........... 135 3.2.1.1 Ultraviolet Photocathode Electron Sources....... 135 3.2.1.2 Hot Filament Electron Sources............. 137 3.2.1.3 Radioactive Electron Sources.............. 137 3.2.2 Test Equipment Considerations.................. 138 3.2.3 Instrument Simulations....................... 141 3.2.4 Sources of Non-Ideal Response.................. 143 3.2.5 Test and Calibration Procedures.................. 148 3.2.5.1 Component Testing................... 148 3.2.5.2 Calibration Runs..................... 150 3.2.6 How to use the Calibrations for Post-Launch Data Processing.. 154 3.3 Low Energy Ion Calibration........................ 157 3.3.1 Numerical Raytracing....................... 159 3.3.2 Laboratory Equipment....................... 160 3.3.3 Testing and Calibration....................... 165 3.3.4 Low-Energy Ion Calibration Facilities............... 165 3.3.4.1 Bennett Ion Mass Spectrometer Calibration....... 167 3.3.4.2 Calibration in a Real Plasma Environment....... 169 3.3.5 Calibration of Faraday Cup Instruments.............. 169 3.3.5.1 Bench Testing...................... 170 3.3.5.2 Beam Testing...................... 172 3.3.5.3 Absolute Calibration with an Ion Beam......... 175 3.4 Medium Energy Ion Calibration...................... 176 3.4.1 The Toroidal Imaging Mass-Angle Spectrograph......... 177 3.4.1.1 Extraction of Calibration Constants From Calibration Measurements...................... 178 3.4.1.2 From Count Rates to Physical Quantities........ 181 3.4.2 The Plasma and SupraThermal Ion Composition Instrument... 185
vi CONTENTS 3.4.2.1 Calibration of the Entrance System........... 187 3.4.2.2 Calibration of the Solid-State Detectors......... 191 3.4.2.3 Calibration of the Microchannel Plate Detectors.... 193 3.4.2.4 TOF Section Calibration................. 194 3.5 High Energy Particle Calibration...................... 196 3.5.1 Calibration of Dosimeters..................... 198 3.5.1.1 Active Volume Determination.............. 200 3.5.1.2 Energy Calibration.................... 203 3.5.2 Calibration of Telescopes...................... 207 3.5.2.1 Geometric Factor Calculation.............. 208 3.5.2.2 Geometric Factor Measurement............. 210 3.5.2.3 Electron Detection.................... 214 3.5.2.4 Conversion to Physical Units.............. 215 3.5.3 Calibration of Mass-Resolving Telescopes............. 215 3.6 Thermal Gas Calibration.......................... 224 3.6.1 The Quasi-Open Source and Thermal Gas Calibration...... 225 3.6.2 Absolute Pressure Thermal Gas Systems............. 226 3.6.3 Transfer Standard Thermal Gas Systems.............. 229 3.6.4 Gases Used for Thermal Gas Calibration............. 237 3.7 Low Energy Neutral Beam Calibration................... 237 3.7.1 Thermal Gas Beam Systems.................... 239 3.7.2 Miscellaneous Low Energy Beam Techniques........... 241 3.7.3 Molecular Beam Techniques.................... 243 3.8 ENA Calibrations.............................. 252 3.8.1 Charge Exchange Gas Cells.................... 253 3.8.2 Photo-Detachment Sources..................... 254 3.8.3 Surface Neutralization....................... 255 3.9 Cross-Calibration between the Flight Model and Laboratory Model.... 258 3.9.1 Solar Wind Instrumentation.................... 259 3.9.2 Cometary Instrumentation..................... 259 3.9.3 Pioneer Venus ONMS Backup Sensor Calibration......... 260 3.9.4 Cassini IMNS Backup Sensor Calibration............. 261 Bibliography................................... 262 4 In-Flight Instrument Calibration and Performance Verification 277 4.1 Introduction................................. 277 4.2 Sources of Instrument Degradation, Noise, and Spurious Responses... 279 4.2.1 Electrostatic Analyzers (ESAs)................... 279 4.2.2 Gain Degradation in Electron Multiplier Detectors........ 284 4.2.3 Time-of-Flight Detector Systems.................. 289 4.2.4 Energetic Particle Detectors.................... 290 4.2.5 Neutral Gas Instruments...................... 292 4.2.6 ENA instruments.......................... 294 4.2.7 Faraday Cup Instruments...................... 295 4.2.8 Langmuir Probes.......................... 296 4.2.8.1 Current-Measuring Probes................ 296 4.2.8.2 Voltage-Measuring Probes................ 298
4.2.9 Unexpected Sources of Noise................... 300 4.3 Identification of Instrument Degradation, Noise, and Spurious Responses 303 4.3.1 Identifying Gain Degradation in Electron Multiplier Detectors.. 304 4.3.2 Identifying Degradation in Time-of-Flight Detector Systems... 311 4.3.3 Identifying Noise and Radiation Damage in Solid-State Detectors 312 4.3.4 Identifying Degradation in Neutral Gas Instruments........ 317 4.3.5 Identifying Degradation and Noise in ENA Instruments...... 319 4.3.6 Identifying Degradation in Faraday Cup Instruments....... 320 4.3.7 Identifying Degradation in Langmuir Probes........... 322 4.3.7.1 Current-Measuring Probes................ 322 4.3.7.2 Voltage-Measuring Probes................ 322 4.3.8 The Use of Artificial Signal Injection for Instrument Performance Verification............................. 323 4.4 Relative and Absolute Calibration of Plasma Instruments......... 324 4.4.1 Introduction............................. 324 4.4.2 Physical Principles......................... 326 4.4.2.1 Use of Wave-Determined Plasma Densities....... 326 4.4.2.2 Calculating Particle Moments and Correcting for Spacecraft Charging...................... 327 4.4.2.3 Charge Neutrality.................... 330 4.4.2.4 Gyrotropy........................ 331 4.4.2.5 Pressure Balance..................... 332 4.4.2.6 Alfvén Waves...................... 332 4.4.2.7 Intra-Satellite versus Inter-Satellite Calibrations.... 332 4.4.3 Geotail............................... 332 4.4.4 Polar-Hydra............................. 337 4.4.5 Wind 3D Plasma.......................... 340 4.4.6 Cluster CIS............................. 347 4.4.6.1 Absolute Efficiencies.................. 347 4.4.6.2 Relative Efficiencies................... 348 4.4.6.3 Pressure Balance..................... 350 4.4.6.4 Three-Spacecraft Check of Calibrations........ 350 4.4.7 NOAA-POES............................ 350 4.4.8 FAST................................ 356 4.4.9 Wind Faraday Cups......................... 359 4.4.9.1 SWE/FC and Waves................... 360 4.4.9.2 SWE/FC and MFI.................... 361 4.4.9.3 CELIAS/MTOF Proton Monitor with SWE/FC..... 362 4.4.9.4 Moment versus Non-Linear Analysis Methods..... 364 4.4.10 In-Flight Testing in Special Circumstances............ 365 4.4.11 Langmuir Probes.......................... 366 4.5 In-Flight Relative and Absolute Calibration for Energetic Particles.... 367 4.5.1 Absolute Energy Response Calibration.............. 368 4.5.2 Relative Flux Response (Multi-Spacecraft)............ 370 4.6 In-flight Relative and Absolute Calibration for Neutral Gas Sensors... 371 4.7 In-Flight Relative and Absolute Calibration for ENA Instruments..... 376 4.8 Conclusion................................. 377 vii
viii CONTENTS Bibliography................................... 378 5 Summary and Outlook 387 5.1 Summary of Previous Chapters....................... 387 5.2 Future Calibration Needs.......................... 388 5.3 Absolute Calibration and Traceability................... 388 5.3.1 The Importance of Traceability to the Space Community..... 389 5.3.2 Lack of Adequate Standards.................... 389 5.3.3 Summary and Recommendation.................. 390 5.4 Calibration Transfer Standard........................ 390 5.4.1 Cross-Calibration Between Facilities............... 391 5.4.2 Non Beam Blocking Current Meter................ 391 5.4.3 Internal Reference Standard.................... 392 5.5 New Techniques to Improve Calibration.................. 392 5.5.1 Challenges for Small Series Production.............. 393 5.5.2 Instrument Response Modeling.................. 394 5.5.3 Statistical methods......................... 394 5.5.4 Artificial Intelligence Methods................... 394 5.6 Machine Learning Methods for Automated Calibration.......... 394 5.6.1 Current State-of-the-Art and Related Work............ 395 5.6.2 Machine Learning Methods.................... 396 5.6.2.1 Model Learning..................... 396 5.6.2.2 Transfer Learning.................... 396 5.6.2.3 Active Learning..................... 398 5.6.3 Other Methods........................... 398 5.7 Summary.................................. 399 Bibliography................................... 399 Appendix 401 A Raytracing in Instrument Design 401 A.1 Electric Field Solving Program....................... 402 A.2 Particle Ray Tracing Program........................ 407 A.3 Display Programs for Characterizing Analyzers.............. 411 A.4 Raytracing Software............................ 414 Bibliography................................... 418 B High Energy Instrument Modeling 421 B.1 Instrument Development Process...................... 421 B.2 Monte Carlo Codes............................. 425 B.3 Numerical Issues.............................. 426 B.4 Random Number Generation........................ 427 B.5 Reduction of Variance............................ 429 B.6 Problems in Using Monte Carlo Simulations................ 430 B.7 Conclusions................................. 431 B.8 Some Available Monte Carlo Codes.................... 432 Bibliography................................... 433
ix C Calibration Facilities 435 C.1 Summary of Calibration Facilities..................... 435 C.2 Description of Calibration Facilities.................... 449 Bibliography................................... 510 D Space Physics Basics 511 D.1 Distribution Functions........................... 511 D.2 Space Physics Terms............................ 512 D.3 Moments Calculation............................ 515 D.4 Typical Parameters of Space Plasma.................... 516 D.5 Comparative Characteristics of Different Mass Spectrometers....... 516 E Glossaries and Acronyms 519 E.1 Glossary of Metrology........................... 519 E.2 Acronyms.................................. 524 E.2.1 Institutions............................. 524 E.2.2 Spacecraft.............................. 525 E.2.3 Instruments............................. 527 E.2.4 Other Acronyms.......................... 531 E.2.5 Radiation Effects on Electronics.................. 533 F Units and Constants 535 F.1 SI Base Units................................ 535 F.2 SI Derived Units.............................. 535 F.3 SI Prefixes.................................. 539 F.4 Units Outside the SI............................. 539 F.5 Constants.................................. 541 F.6 Units and Unit Conversion......................... 542 G Relative Isotopic Standard 545 H Fragmentation Patterns and Total Ionization Cross Sections 555 H.1 Neutral Gas Electron Impact Mass Fragmentation Patterns........ 556 H.2 Neutral Gas Electron Impact Total Ionization Cross Sections....... 561 Bibliography................................... 569 I Authors Addresses 571 Index 575
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