ION SOURCES

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CAT-KEK SOKENDAI School on Spallation Neutron
Source Accelerator Physics Technological
Aspects February 2 8, 2004, Centre for Advanced
Technology, Indore, India
ION SOURCES
Akira Takagi
KEK (High Energy Accelerator Organization), Japan
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ION SOURCES(1)

• Early History of the Particle Accelerator
• Production Methods of Negative Ion
• Types of Negative Hydrogen Ion Source
• KEK-PS H- Ion Source
• LaB6 Filament
• Beam Chopping
• Secondary Electron by Ion Impact
• Heavy/Metal Negative Ion

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Early History

• The First artificially induced nuclear
  transmutation. (Rutherford,1919)
• 16N 4He ? 17O 1H
• a-particles (7 MeV, 2x107 m/s) from radium
• The results as a whole suggest that if
  a-particles or similuar projectiles- of still
  greater energy were available for experiment, we
  might expect to break down the nuclear structure
  of many of the lighter atoms.
• Rutherford, Phil. Mag. 37, 578 (1919)

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Cockcroft-Waltons Voltage Multiplier

• The first nuclear disintegration by nuclear
  projectiles artificially produced in a man-made
  accelerator.(1932)
• 7Li 1H ? 4He 4He (17.3MeV)
• Cockcroft, Walton, Proc. Roy. Soc. A137,
  229(1932)

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Charge Transfer Processes (H -gt H-)
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Charge Exchange (D-)
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Electron Affinities for atoms and molecules
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H- Ions from Duoplasmatron
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H- from Duoplasmatron
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Potential distribution at the metal surface
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PIG (Penning Ion Gauge) Type
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Magnetron H- Production(Surface Production)
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Magnetron Type
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Multicusp Surface H- Ion Source
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Multicusp Volume Production H- Ion Source
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Multi-Cusp Negative Hydrogen Ion Source(Surface
Production Type)BLAKE-I
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KEK-PS Ion Source just before Installation
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Electron Suppression
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LaB6 Tungsten

• LaB6 W2.67 eV
• 9 A/cm2 1900 K
• W W4.55 eV
• 1.6 A/cm2 2700 K

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LaB6 Filament (15 mm dia.)
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Surfase Analysis of LaB6 Filament
After 1000 hrs operation
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LaB6 FilamentCathode Flange
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After 3000 hrs Operation
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LaB6 Filament (20 mm dia.)
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LaB6 FilamentCathode Flange(Volume Source)
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Empty Cs Ampoules Cs-Glass Reactants
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750 keV Pre-Injector for 12 GeV PS
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Ratio of Negative Hydrogen Ions
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Operating ParametersMulticusp Surface production
Negative Hydrogen Ion SourceBLAKE-I

• ARC Current 83 A
• ARC Voltage 109 V
• ARC Pulse Width 180 msec
• Converter Voltage 650 V
• Gas Flow Rate 7.7 cc/min
• Filament Current Voltage
• FIL-1 72A x 8.0 V(1400 C)
• FIL-2 73A x 8.1V (1390 C)
• Cockroft-Walton Generator Voltage 749.5 kV
• Beam Current 39.1 mA

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Beam Pulse Ion Source Extraction Linac
Entrance
U Voltage drop of the terminal voltageM
Ion source output (H-)L Linac Input (H-)
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Production of Direct-Chopped H- Ion Beam
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Fast chopped H- beam (2 MHz)by the direct
modulation of converter voltage
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Radio Frequency Discharge
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Radio Frequency Skin Depth (Xe)
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Secondary Electron Emission

• In the case of electron impact
• The energy of the primary electron must be
  higher than the energy determined by the work
  function of the metal surface.
• In the case of positive ion impact,
• The secondary electron can be induced only if
  the sum of the potential energy E and the kinetic
  energy Ei is higher than twice the value of the
  work function f.
• E Ei gt 2f

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Secondary Electron Emission by Ion Impact
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Faraday Cup Signals by H-//o Beam(Without
Secondary Suppression)
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Secondary electron Coefficients by H-//o Beam
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No Conclusion

• Tomorrows my lecture
• Volume Production Negative Hydrogen Source
• Early results in KEK
• Recent results for J-PARC
• H- diagnostics (with laser)