Physics and Applications of Hydrogen Negative Ion Sources

Preface
References
Contents
Contributors
1 Fundamental Processes of Hydrogen Negative Ion Production in Ion Source Plasma Volume
1.1 Need of Negative Ion Beams for Magnetic Confinement Fusion Research and for High Energy Accelerators
1.2 The Volume Production Mechanism
1.2.1 Early Direct Extraction Negative Ion Sources (Before 1980)
1.2.2 Observation of a New H− Ion Formation Mechanism in the Plasma Volume
1.2.3 H− Formation by DA to Excited H2 Molecules
1.2.4 Excited H2 Populations in Low-Temperature Plasmas
1.2.5 Experimental Validation of the Volume Production Mechanism
1.3 Volume Production of H− Ion Sources
1.3.1 Penning Source
1.3.2 The Magnetically Filtered Multicusp Volume Negative Ion Source
1.3.2.1 Role of the Magnetic Filter
1.3.2.2 Role of the Plasma Electrode
1.4 Conclusion
References
2 Fundamental Aspects of Surface Production of Hydrogen Negative Ions
2.1 Introduction
2.1.1 Early Observations
2.1.2 High-Current Surface Plasma Source
2.1.3 Cs Operation of Volume Production Source
2.2 Mechanism of Negative Ion Surface Production
2.2.1 Theoretical Background
2.2.2 Experiments on Fundamental Processes
2.2.3 Experimental Results Using Ion Sources
2.3 Surface H− Ion Production at Low Energy
2.3.1 Negative Ion Production at Cs Covered PG Surface
2.3.2 Contamination of PG Surface by Impurities
2.4 Conclusion
References
3 Modeling of Reaction Dynamics in Volume-Production Negative Hydrogen Ion Sources
3.1 Introduction
3.2 Brief Description of GMNHIS
3.2.1 Particle Balance Equation
3.2.2 Power Balance Equation
3.2.3 Chemistry Mechanism in the Volume-Production NHIS
3.3 Benchmarking of GMNHIS for RF Discharge
3.3.1 Negative Hydrogen Ion Density and Electronegativity Versus Pressure
3.3.2 Electron Temperature and Electron Density Versus Pressure
3.3.3 VDFs at Two Different Pressures
3.3.4 Densities of Positive Ions and H (N == 1–3) Atoms Versus Pressure
3.4 Validation of GMNHIS for ECR Discharge
3.4.1 Electron Density Versus Pressure
3.4.2 Pressure Dependence of VDF
3.4.3 Determination of Negative Hydrogen Ion Density
3.4.4 Production and Loss Mechanisms of Negative Hydrogen Ions
3.5 Analytical Model for VDF
3.5.1 Reduced Set of Processes for Vibrational Kinetics
3.5.2 Particle Balance for Vibrational States
3.5.3 Repopulation Probabilities of Vibrational States on the Wall
3.5.4 Reduced Linear Model for VDF
3.6 Conclusion
References
4 Particle-In-Cell Modeling of Negative Ion Sources for Fusion Applications
4.1 Introduction
4.2 The Particle-In-Cell Technique
4.3 Plasma Transport Across the Magnetic Barrier
4.4 Gas Dynamics and Vibrational Kinetics
4.5 Negative Ion Production on Surfaces
4.5.1 2.5D of the Whole Ion Source Volume Including the Apertures
4.5.2 Charged Particle Extraction Dynamics Across Apertures
4.6 Conclusions
Bibliography
5 Electrostatic and Electromagnetic Particle-In-Cell Modelling with Monte-Carlo Collision for Negative Ion Source Plasmas
5.1 Fundamentals of Negative Ion Source Plasma Modelling by Particle-In-Cell
5.1.1 Numerical Modelling for Negative Ion Source Development
5.1.1.1 Main Physical Processes in Negative Ion Sources
5.1.2 Basic Equations of the PIC Modelling
5.1.2.1 Electrostatic PIC
5.1.2.2 Electromagnetic PIC
5.1.3 Collision Processes
5.2 Negative Ion Extraction Mechanism from the Surface Production Ion Source
5.2.1 Surface Produced H− Extraction Under the Low Source Filling Gas Pressure
5.2.2 Surface-Produced H− Extraction Under the High Source Filling Gas Pressure
5.3 Plasma Meniscus and Negative Ion Beam Optics
5.3.1 Asymmetry of the Plasma Meniscus
5.3.2 Effects of Extraction Voltage on the Plasma Meniscus and Beam Optics
5.3.3 Negative Ion Beam Acceleration and Beam Optics
5.4 EM-PIC-MCC Modelling in the RF Driven Negative Ion Source for Accelerators
5.4.1 Introduction
5.4.2 PIC Simulation of the E-Mode RF Plasma
5.4.3 PIC Simulation of H-Mode RF Plasma
5.5 Conclusion
References
6 Plasma and Gas Neutralisation of High-Energy H− and D−
6.1 Background
6.2 Reactions
6.3 Basic Equations
6.4 Cross-Sections
6.5 Calculation Method
6.6 Results
6.7 Discussion and Conclusions
References
7 Advanced Models for Negative Ion Production in Hydrogen Ion Sources
7.1 Introduction
7.2 H2 Cross-Sections
7.3 Numerical Model
7.4 Global Kinetic Model of Multicusp Negative Ion Source
7.4.1 Kinetic Scheme
7.4.2 Multicusp Source
7.5 Results
7.6 Conclusions
Bibliography
8 The Plasma Sheath in Negative Ion Sources
8.1 Introduction
8.2 The Plasma Sheath
8.3 Production and Transport of Negative Ions Across the Sheath
8.3.1 Surface Production of Negative Ions
8.3.2 The Formation of a Virtual Cathode
8.3.3 The Virtual Cathode in a Plasma-Based Ion Source
8.3.3.1 The Sheath before the Formation of a Virtual Cathode
8.3.3.2 The Plasma Sheath with a Virtual Cathode
8.4 The Plasma Sheath with Negative Ions Emitted at the Wall
8.4.1 The Sheath Structure and Its Implications
8.4.2 The Effect of Surface Work Function
8.4.3 The Emission of Electrons into the Sheath
8.5 Beam Extraction
8.6 Conclusions
References
9 Helicon Volume Production of H- and D- Using a Resonant Birdcage Antenna on RAID
9.1 Introduction
9.2 The Resonant Antenna Ion Device (RAID)
9.2.1 RAID Vacuum Vessel, Pumping System, and Magnetic Field
9.2.2 RAID Plasma Source: The Birdcage Antenna
9.2.3 Plasma Parameters in RAID and Standard Conditions
9.3 Overview of RAID Diagnostics
9.3.1 Diagnostics of Electron Parameters
9.3.2 Diagnostics for Negative Ions: Optical Emission Spectroscopy, Cavity Ring-Down, and Photodetachment
9.3.2.1 Optical Emission Spectroscopy (OES)
9.3.2.2 Cavity Ring-Down Spectroscopy (CRDS)
9.3.2.3 CRDS Experimental Setup in RAID
9.3.2.4 Langmuir Probe Laser Photodetachment (LPLP)
9.4 Measurements of Negative Ions
9.4.1 First Evidence of Negative Ions in RAID Using OES
9.4.2 Measurements of Negative Ions Using CRDS
9.4.3 Measurements of Negative Ions with LPLP
9.4.4 Combining CRDS and LPLP to Extract Absolute Negative Ion Density Profiles
9.5 A 1.5D Fluid: Monte Carlo Model of a Hydrogen Helicon Plasma
9.5.1 Description of the Fluid Model
9.5.2 Reaction Rates
9.5.3 A Monte Carlo (MC) Model to Determine Neutral Density Profiles
9.5.4 Transport of the Ion Species
9.6 Conclusions
References
10 Plasma Electrode for Cesium-Free Negative Hydrogen Ion Sources
10.1 Introduction
10.2 Materials for Production of Highly Excited Ro-vibrational Hydrogen Molecules
10.3 Materials for Negative-Ion Surface Production
10.3.1 Basic Mechanisms of Negative-Ion Formation on Plasma Electrode Surfaces
10.3.2 Carbon Materials
10.3.3 Nanoporous C12A7 Electride
10.4 Discussions and Summary
References
11 Low-Temperature High-Density Negative Ion Source Plasma
Nomenclature
11.1 Introduction
11.2 Magnetic Multipole Plasma Source and Its Filaments
11.3 The Discharge Mechanism and the Ion Species Ratio
11.4 Mode Flap in Arc Discharge
11.5 Cusp Leak Width
11.6 Need of Negative Ion Beams
11.7 Negative Ion Production
11.8 Volume Production
References
12 ECR–Driven Negative Ion Sources Operating with Hydrogen and Deuterium
12.1 Fundamental Principles of Electron Cyclotron Resonance (ECR) Heating
12.2 H− and D− Negative Ion Production and Destruction Processes in ECR-Driven Plasmas
12.3 Representative H− and D− Negative Ion Sources
12.3.1 Camembert III
12.3.2 Prometheus I
12.3.3 ECR with Driven Plasma Rings
12.3.4 HOMER
12.3.5 ROSAE (I, II, and III)
12.3.6 Scheme (I, II, and II+)
12.4 Other Sources and Extracted Currents in ECR Sources
References
13 Vibrational Spectroscopy of Hydrogen Molecules by Detecting H− (D−) and Its Use in Studies Relevant to Negative Ion Sources
13.1 Introduction
13.2 Dissociative Electron Attachment to Hydrogen
13.3 Hydrogen Vibrational Spectroscopy (HVS) by Negative Ion Detection
13.3.1 Basics of the Use of DEA Properties for Hydrogen Vibrational Spectroscopy (HVS)
13.3.2 Experimental Setups
13.3.2.1 Electrostatic Setup at LDMA Paris
13.3.2.2 Magnetic Setup in JSI Ljubljana
13.3.2.3 Beam-Like Experimental Setup in JSI Ljubljana
13.4 Applications and Results
13.4.1 Metal Cell with the Hot Tungsten Filament
13.4.2 Atom Recombination on Metal Exposed to Atom Beam
13.4.3 Results of Some Other Applications of HVS Based on DEA
13.5 Perspectives
References
14 Physics of Surface-Plasma H− Ion Sources
14.1 Introduction
14.2 Mechanism of Surface-Plasma Negative Ion Production
14.2.1 Main Physical Processes in SPS
14.2.2 First Surface-Plasma Sources
14.2.3 Studies of Intense Negative Ion Production in the First SPS
14.3 Surface Processes of Negative Ion Formation in SPS
14.3.1 Negative Ion Secondary Emission
14.3.2 H− Production by Hydrogen Particles Backscattering (Reflection)
14.3.2.1 H− Production by Backscattering of Energetic Hydrogen Ions and Atoms
14.3.2.2 H− Production by Backscattering of Thermal Hydrogen Atoms
14.3.2.3 H− Production by Backscattering of Suprathermal Hydrogen Atoms
14.3.3 Negative Ion Production by Desorption (Sputtering)
14.3.3.1 Negative Ion Production Due to Impact Desorption by Light Ions and Atoms
14.3.3.2 Negative Ion Production Due to Impact Desorption by Heavy Ions
14.3.3.3 Total H− Ion Production by Backscattering and Desorption by Hydrogen Ions
14.3.4 Negative Ion Yield Due to Mixed Ion Bombardment
14.3.5 Surface Negative Ion Production in Plasma Environment
14.3.5.1 Hydrogen-Cesium Plasma
14.3.6 Hydrogen Plasma with Addition of Inert Gases
14.4 Channels and Efficiency of Negative Ion Production in SPS
14.4.1 SPSs with High-Current E = B Discharges
14.4.1.1 Planotron (Magnetron) SPSs
14.4.1.2 Penning SPSs
14.4.2 Direct Current SPSs
14.4.3 Multicusp SPS with Internal Converter
14.4.4 SPSs with Pulsed High-Power RF Discharges
14.4.5 Giant Long-Pulsed Multiaperture SPS for Fusion Neutral Beam Injectors
14.5 Essential Features of Negative Ion Production in SPS
14.5.1 Cesium Catalyst of Negative Ion Production
14.5.1.1 Primary Cesium Seed to SPS Electrodes
14.5.1.2 Conditioning (Activation) of the Cesiated SPS Electrodes
14.5.1.3 Confinement and Recirculation of Cesium in the High-Current E = B Discharges
14.5.2 Suppression of Co-extracted Electron Flux
14.6 Summary
References
15 Hydrogen Negative Ion Density Diagnostic in Plasma
15.1 Introduction
15.2 Measurement of the Negative Ion Density in Plasma by Langmuir Probe-Assisted Photodetachment
15.3 Measurement of the Negative Ion Density in Plasma by Cavity Ring-Down Spectroscopy (CRDS)
15.4 Negative Ion Source Study with Photodetachment Method
15.5 Conclusion
References
16 RF-Driven Ion Sources for Neutral Beam Injectors for Fusion Devices
16.1 Introduction
16.2 Modular Concept of the RF-Driven Ion Source
16.2.1 The Prototype Source
16.2.2 Size Scaling
16.2.3 RF Coupling Efficiency
16.2.4 Magnetic Filter Field
16.2.5 Low Pressure Operation
16.2.6 Plasma Parameter
16.3 Achievements for ITER
16.3.1 Short Pulses: Up to 10 s
16.3.2 Long Pulses: Up to 1 h
16.3.3 Toward Full Performance of the ITER Source: A Stepwise Approach
16.4 Lessons Learned and Challenges
16.4.1 Source Operation: RF Issues/Technology
16.4.2 Plasma Uniformity, Symmetry of Co-extracted Electrons, and Beam Uniformity
16.4.3 Cesiation and Co-extracted Electrons
16.5 Activities Beyond ITER
16.5.1 RF Sources for a DEMO: Worldwide Activities
16.5.2 Racetrack-Shape RF Drivers
16.5.3 Cesium Consumption
16.5.4 Reliability and Availability
16.6 Conclusion and Outlook
References
17 Ion Source Engineering and Technology
17.1 Introduction
17.2 Powering the Plasma
17.2.1 Accelerating Electrons
17.2.2 CCP Power Supply
17.2.3 ICP Power Supply
17.3 Magnetic Fields
17.3.1 Magnetised Electrons
17.3.2 Making Magnetic Fields
17.4 Extracting Negative Ions
17.5 High Voltage
17.5.1 High Fields
17.5.2 High-Voltage Platform
17.5.3 Platform Bias Voltage Stability
17.5.4 High-Voltage Enclosure Versus High-Voltage Room
17.5.5 High-Voltage Design
17.5.6 Electrode Design
17.5.7 Insulator Design and Triple Junctions
17.5.8 Triple Junction Shielding
17.5.9 Insulator Material
17.5.10 Insulator Surface Profile
17.5.11 Insulator Protection
17.5.12 Insulation Coordination
17.5.13 Gaseous Insulation
17.5.14 Liquid Insulation
17.5.15 Cooling Equipment on High-Voltage Platforms
17.5.16 Breakdown Protection
17.6 Earthing
17.6.1 The Earth Connection
17.6.2 Local Earth
17.6.3 Earth Loops
17.6.4 Equipotential Bonding
17.6.5 Automatic Earthing
17.6.6 Earth Sticks
17.7 Safety
17.7.1 Compliance with Regulations
17.7.2 Personnel Protection Interlock System
17.7.3 Reliability of the PPS
17.7.4 IEC 61508
17.7.5 Electrical Authorization
17.7.6 Radiation Protection
17.7.7 Hydrogen Safety
17.8 Controls and Diagnostics
17.8.1 Control System
17.8.2 Diagnostics
17.9 Vacuum and Gas Systems
17.9.1 A Wide Range of Pressures
17.9.2 Differential Pumping
17.9.3 Vacuum System Design
17.9.4 Trapped Volumes
17.9.5 Types of Vacuum Flanges and Seals
17.9.6 Primary Vacuum Vessel and Main Insulator
17.9.7 Plasma Chamber
17.9.8 Surfaces in Vacuum
17.9.9 Vacuum System Exhaust
17.9.10 Gas Delivery Systems
17.9.11 Caesium Systems
17.10 Plasma Ignition Systems
17.11 Documentation Systems
17.11.1 Mechanical Drawings
17.11.2 Electrical Drawings
17.11.3 Ancillary Equipment
17.11.4 Ion Source `Build Sheets'
17.11.5 Post Failure Analysis
17.12 Reliability
References
18 Radio Frequency-Driven, Pulsed High-Current H− Ion Sources on Advanced Accelerators
18.1 Introduction
18.2 Radio Frequency-Driven, Hydrogen Discharges
18.3 The Spallation Neutron Source RF H− Ion Source
18.4 The Surface-Produced H− Ions
18.5 The Management of Cesium
18.6 Refurbishing and Starting Up RF Ion Sources, Their Performance, and Their Plasma Outages
18.7 Internal or External Antenna?
18.8 Other Failures of the Past
18.9 Service Cycles and Lifetimes of the SNS RF H− Source
18.10 The H− Beam Decay and the Loss of Cesium
18.11 Surface Films in the SNS RF H− Ion Source
18.12 The SNS H− Extraction and the Low-Energy Beam Transport
18.13 A Summary and Outlook for the SNS RF H− Ion Source
18.14 The RF-Driven H− Source at J-PARC
18.15 The RF-Driven H− Source at CERN's LINAC4
18.16 The RF-Driven H− Source at CSNS
18.17 The Future of Pulsed, High-Current H− Sources
References
19 Development of High-Current Negative-Ion-Based Beam Source at the National Institutes for Quantum Science and Technology (QST) in Japan for JT-60 U and ITER Neutral Beam Injectors
19.1 Negative Ions in Fusion Applications
19.2 Magnetic Filter for Low-Temperature Plasma
19.3 KAMABOKO Source for Surface Production of Negative Ions
19.4 Negative Ion Extraction and Electron Suppression
19.5 Beam Deflection and Compensation
19.6 Negative Ion Acceleration up to MeV Beam Energy
19.7 Conclusion and Discussion
References
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