ION SOURCES Akira Takagi KEK (High Energy Accelerator Organization), Japan CAT-KEK SOKENDAI School on Spallation Neutron Source: Accelerator Physics ＆

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)