ion sources akira takagi kek (high energy accelerator organization), japan cat-kek sokendai school...
TRANSCRIPT
ION SOURCES
Akira TakagiAkira TakagiKEK KEK (High Energy Accelerator Organization), (High Energy Accelerator Organization), JapanJapan
CAT-KEK SOKENDAI School on Spallation Neutron Source: Accelerator Physics & Technological AspectsFebruary 2 – 8, 2004, Centre for Advanced Technology, Indore, India
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
Early History• The First artificially induced nuclear transmuta
tion. (Rutherford,1919)
16N + 4He 17O + 1H-particles (7 MeV, 2x107 m/s) from radium
• The results as a whole suggest that if -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)
Cockcroft-Walton’s 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)
Charge Transfer Processes (H+ -> H-)
Charge Exchange (D-)
Electron Affinities for atoms and molecules
H- Ions from Duoplasmatron
H- from Duoplasmatron
Potential distribution at the metal surface
PIG (Penning Ion Gauge) Type
Magnetron H- Production(Surface Production)
Magnetron Type
Multicusp Surface H- Ion Source
Multicusp Volume Production H- Ion Source
Multi-Cusp Negative Hydrogen Ion Source(Surface Production Type)
BLAKE-I
KEK-PS Ion Source just before Installation
Electron Suppression
LaB6 & TungstenLaB6 : W=2.67 eV
9 A/cm2 :1900 K
W : W=4.55 eV
1.6 A/cm2 : 2700 K
LaB6 Filament (15 mm dia.)
Surfase Analysis of LaB6 Filament
After 1000 hrs operation
LaB6 Filament&
Cathode Flange
After 3000 hrs Operation
LaB6 Filament (20 mm dia.)
LaB6 Filament& Cathode Flange(Volume Source)
Empty Cs Ampoules & Cs-Glass Reactants
750 keV Pre-Injector for 12 GeV PS
CM-1#1-Ion Source
#2-Ion Source
CM-2
CM-3CM-4CM-5
CM-6
H
H
H
CM-7
40 MeV Linac
QT
BD
BDTTTTTTTTT
D
T T
T
TD
T
B
B
B B
B
V-3
BEAM SHUTTER (ION-1)
V-2
GV-4
E.S. CHOPPER (ION-2)
E.S. CHOPPER (ION-1)
V-1
BEAM SHUTTER (ION-2) GV-3 GV-2 GV-1
Ratio of Negative Hydrogen Ions
0.00.10.20.30.40.50.60.70.80.91.0
0 20 40 60
Time (hr)
Rat
io
CM2/CM1
CM3/CM2
Operating ParametersMulticusp Surface production Negative Hydrogen Ion Source
BLAKE-I
• ARC Current 83 A• ARC Voltage 109 V• ARC Pulse Width 180 sec• 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
Beam Pulse : Ion Source Extraction & Linac Entrance
U : Voltage drop of the terminal voltage
M : Ion source output (H-)
L : Linac Input (H-)
Production of Direct-Chopped H- Ion Beam
Fast chopped H- beam (2 MHz)
by the direct modulation of converter voltage
Radio Frequency Discharge
Radio Frequency Skin Depth (Xe)
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 .
E + Ei > 2
Secondary Electron Emission by Ion Impact
Faraday Cup Signals by H-/+/o Beam(Without Secondary Suppression)
Secondary electron Coefficients by H-/+/o Beam
No Conclusion
• Tomorrow’s my lecture:
• Volume Production Negative Hydrogen Source • Early results in KEK• Recent results for J-PARC• H- diagnostics (with laser)