Huashun Zhang. Ion Sources. With 187 Figures and 26 Tables Э SCIENCE PRESS. Springer

Transcription

1 Huashun Zhang Ion Sources With 187 Figures and 26 Tables Э SCIENCE PRESS Springer

2 XI Contents 1 INTRODUCTION Major Applications and Requirements Performances and Research Subjects Historical Development 8 2 GAS DISCHARGE FUNDAMENTALS Thermionic Emission Secondary Electron Emission Surface Ionization Elastic and Inelastic Collisions Collision and Probability of Collision Elastic Collision and Its Cross Section Inelastic Collision Ionization Cross Section Recombination of Charged Particles Mobility Diffusion Coefficient Particle Distribution in a Retardation Region Ambipolar Diffusion Magnetic Field Influence on Particle Motion Fundamentals of a Hot-Cathode Arc Source Stable Theory of the Cathode Double Sheath Bipolar Flow Cathode Double Sheath Cathode Double Sheath Oscillations and Noise Scattering of Primary Electrons Beam-Plasma Interaction Positive Column Plasma Anode Region Minimum Pressure 45 References 46 3 EXTRACTION SYSTEMS FOR ION SOURCES Extraction Systems Requirements Extraction System with a Solid Emitter Space-Charge-Limited Flow for an Ideal Diode Plane Diode Cylindrical Diode 51

3 XU 3. Spherical Diode Some Universal Relationships Space-Charge-Limited Flow with Multiple Ion Species Pierce-Shape Extraction System High-Perveance Electron Gun Emittance and Brightness Emittance Brightness Relation Between Brightness and Emittance Effective Emittance Emittance and Brightness of an Ion Source Ion Extraction from a Plasma Plasma-Sheath Equation and the Emitting Current from a Plasma The "Extractable Flow" from an Extraction System Adjustment of Ion Emissive Surface Comparison between a Plasma Ion Source and an Electron Gun Extraction System Geometry of Extraction Systems Typical Types and Geometries Probe Extraction Systems for Low Plasma Density Principle and Analytical Model Experimental Results Aperture Extraction Systems for Medium Plasma Density Analytical Model for a Two-Electrode System Circular Three Electrode Extraction System Slit Extraction System Four Electrode Extraction System Expansion Cup Extraction System for High Plasma Density Some Properties of a Diffusing Plasma Extraction System of a Duoplasmatron Source Large-Area Multi-Aperture Extraction Systems Multi-aperture Beam Focusing by Aperture Displacement Power Loading of the Electrodes Grid-controlled Extraction System Research Methods of Extraction Systems Experimental Research Analytical Approaches to Beam Optics Numerical Simulations Physical Models Physical Equations Some Results 108

4 хш 3.7 Some Other Problems Transverse Magnetic Field Effects on Ion Extraction Technological Problems of Extraction Systems... Ill 1. Suppression of Breakdown in the Lateral Extraction Ion Source Ill 2. Some Technological Problems 112 References POSITIVE ION SOURCES Classification of Ion Sources Hot Cathodes Requirements and Types of Hot Cathodes Cathode Material and Lifetime Effects of Discharge Current Magnetic Field Effects of the Filament Current Plasma Cathodes Arc Source in a Uniform Magnetic Field Hot-Cathode Penning Source Simple Principle Typical Structures Duoplasmatron Ion Source General Principle Formation of the Constriction Double Sheath Primary Parameters Heavy Ion Duoplasmatron Source Hot-Cathode "Freeman" Source Broad Beam Ion Sources Cold-Cathode PIG Source Principles of a Cold-Cathode Penning Discharge Cold-Cathode PIG Sources Radio-Frequency Ion Source Principle of an RF Discharge Magnetic Field Effects and Structures Heavy Ion RF Sources Metallic Ion RF Sources RF Ion Source for Ion Thrusters RF Tritium Ion Source Beam Current Modulation from RF Sources Technology of Heavy Ion Sources Special Requirements for Heavy Ion Sources Types of Heavy Ion Sources Surface Ionization and Thermionic Emission Source High Field Ion Source Gas Field Ionization Source Liquid Metal Ion Source 170

5 XIV Feed Material Methods of Vapor Transport Design and Operation of Heavy Ion Sources 179 References GIANT ION SOURCES DuoPIGatron Ion Source Essential Principle Improvement of the Plasma Uniformity Typical Results Periplasmatron Ion Source Multifilament Ion Source Essential Principle Multifilaments and Multislot Extraction Electrode Ionization Efficiency Typical Results Magnetic Multipole Ion Source General Description Magnetic Multipole (Multicusp) Field Confinement Principle of a Cusped Field Magnetic Field Configuration Influence of Other Parameters Typical Results and Applications Hall Accelerator Cluster Ion Source Intense Pulsed Ion Source Reflex Triode Magnetically Insulated Ion Diode Anode Plasma and Structure 222 References MULTIPLY CHARGED ION SOURCES Introduction Formation of Multiply Charged Ions Physical Definitions for Multiple Ionization Ionization Potential Total and Partial Ionization Cross Section Distribution of Charge States and Average Charge State Formation of Multiply Charged Ions Multiple Ionization by Single Collisions Stepwise Single Ionization of Ions Stepwise Multiple Ionization of Ions Ionization of Metastable Atoms or Ions Loss Processes of Multiply Charged Ions 239

6 XV 1. Loss by Charge Transfer Loss by Recombination Loss by Diffusion Balance Equations for Ion Charge States Multiply Charged Ion Generation by Stripping of Fast Ions Major Research of MCIS Multiply Charged Electron Beam Ion Source Electron Beam Ion Source Typical Structure Essential Principle and Results Electron Beam Ion Trap Time-of-Flight EBIS (TOFEBIS) Conventional Multiply Charged Ion Sources Penning Multicharged Ion Source Introduction, Types, and Typical Structures The Essential Principle of Generating Multiply Charged Ions in a PIG Source Experimental Results Duoplasmatron MCIS Other Plasma Discharge MCIS Radio-Frequency Ion Source Electrostatic Oscillating Electron Ion Source Trapped Ion Source Microwave Ion Sources Electron Cyclotron Resonance Multiply Charged Ion Source Development and Typical Structure Essential Principles and Results High Intensity Microwave Ion Source Cavity Type Microwave Ion Source Antenna Type Microwave Ion Source High-intensity Microwave Proton Source Hot Electron Layer Ion Source (HELIOS) Beam-Plasma Ion Source High Density Plasma Sources Laser Multiply Charged Ion Source Metal Vapor Vacuum Arc Ion Sources Vacuum Spark Ion Source 297 References MASS AND ENERGY SPECTRA OF ION SOURCES Mass Spectra of a Hydrogen Ion Source Physical Processes Effecting the Mass Spectra 305

7 XVI Particle Balance Equations for Determining the Mass Spectra Proton Content of an RF Ion Source Mass Spectra of a Magnetic Multipole Ion Source Mass Spectra of a Duoplasmatron Ion Source Mass Spectra of a Hot-Cathode PIG Ion Source Mass Spectra of a Cold-Cathode PIG Ion Source Energy Spectra of Ion Sources Physical Cause of the Energy Spread Energy Spectra of an RF Ion Source Energy Spectra of Other Ion Sources 322 References NEGATIVE ION SOURCES Introduction Electron Affinity Historical Development Negative Ion Formation Processes Volume Formation of Negative Ions H~ Formation by Electron Impact Negative Ion Formation by Multiple Charge-Transfer Surface Formation of Negative Ions Work-function of Surfaces Surface Sputtering Essential Principle Distributions of Sputtered Particles Particle Reflection from a Solid Surface Essential Principles Parameter Dependence of Reflection Distribution of Reflected Particles Secondary Ion Emission General Principles H~ Ion Formation by Particle and Surface Interaction Other Negative Ions Formed by Sputtering Negative Surface Ionization Destruction of Negative Ions Destruction Processes of Negative Ions Cross-Sections of H _ Destruction Volume H _ Ion Source Duoplasmatron Negative Ion Sources Penning Negative Ion Sources Magnetically Filtered Multicusp Volume Sources Essential Principle Magnetic Filter 364

8 XVII 3. Dependence on Various Parameters Cesium Seeded Multicusp H _ Source Giant H _ Ion Sources Other Volume Production Negative Ion Sources H _ Ion Extraction and Electron Suppression Surface-Plasma H _ Ion Sources Magnetron H~ Ion Sources Penning Surface-Plasma H - Ion Sources Magnetic Cusped Surface-Plasma H _ Sources Hollow Discharge Duoplasmatron H _ Sources Charge-Transfer Negative Ion Sources Exchange Target Charge-Transfer H _ Ion Sources Radio Frequency Negative Ion Source Powerful Charge-Transfer H~ Ion Sources He" Ion Source Other Charge-Transfer Heavy Negative Ion Sources Cesium Sputter Negative Ion Sources Middleton Cesium Sputter Source (UNIS) Cesiated Plasma Sputter Negative Ion Sources Radial Extraction Sputtering Penning Negative Ion Source Self-Extraction Plasma-Sputtering Negative Ion Source Universal High Intensity Cesium Sputter Negative Ion Sources Dissociative Source by Positive Ion Impact Surface Negative Ionization Ion Sources 397 References SELF-NEUTRALIZATION OF BEAM SPACE CHARGE Self-Neutralization of Positive Beams Dynamic Decompensation of the Beam Space Charge 410 References BEAM DIAGNOSTICS FOR ION SOURCES Introduction Beam Current Measurements Electric Methods Intercepting the Beam DC Current Measurement by a Faraday Cup Pulsed Current Measurement by a Faraday Cup Calorimetric Methods Essential Principles of Calorimetric Methods Flow Calorimeter Stem Calorimeter 423

9 XVlll 4. Calorimeter in an Isothermal Mode Magnetic-Conduction Probe for Pulsed Beams Residual Gas Ionization Chamber Beam Density Profile Measurements Mechanical Beam Profile Scanner Segmented Wire (or Target) Electric or Magnetic Scanner Other Methods Beam Emittance Measurements Physical Concept of Beam Emittance Measurement Principle and Errors of Emittance Measurement Various Emittance Devices "Pepper-Pot" Emittance Probe Mechanical Scanner Electric (Magnetic) Scanner Slit-Multiple Collector Device "Three Beam Widths" Method Ion Energy Spectra Measurements Cylindrical Electrostatic Energy Analyzer Retarding Field Energy Analyzer Mass or Charge Spectra Measurements Uniform Magnetic Field Analyzer E x В Mass Separator Time-of-Flight Spectrometer 457 References 459 APPENDIX 462 Al. Physical Constants 462 A2. Common Usits and Conversion Factors 463 A3. Densities, Melting Points, Boiling Points, Vapor Pressure, Some Source Feed Compounds 464 A4. Work-function, First and Stepwise Ionization Potential, Electron Affinity of the Elements 468 A5. The Calculated Values of the Stepwise Ionization Potential of Noble Gases 472 A6. The Minimum Workfunctions of Amorphous Surfaces with Adsorbate Materials at Optimum Layer 472 A7. Solution of the Plasma-Sheath Equation 473 INDEX 474