The CERN Hadron Ion Sources

For the production of hadronic particles for the CERN accelerator complex, two types of pulsed ion source are currently in use. Ions from these sources are preaccelerated before injection into the linacs. Protons are produced in a Duoplasmatron source, injected into Linac2 and accelerated to 50 MeV. Heavy Ions, currently lead208 27 times charged, are formed in an Electron Cyclotron Resonance (ECR) source for acceleration in Linac3 to 4.2 MeV/u.

The CERN Duoplasmatron Proton Ion Source

Proton Source Characteristics

The Heavy Ion (Lead) Source

Lead Ion Source Characteristics

Source Characteristics

Proton Source

Type Duoplasmatron with biased electrode in expansion cup
Source Body Iron or mild steel acting as magnetic flux path
Intermediate electrode Iron, water cooled. Forms cathode plasma chamber
I.E. Canal 5 mm. diameter, 12 mm. long
Cathode Mixed oxide thermionic, hairpin, 16 mm. by 92 mm.
Heating current 50 A (150 W) via arc isolating transformer
Hydrogen flow 3 - 6 (0.05 - 0.1 mbar l/s)
Plasma chamber pressure 0.7 - 2 mbar (estimated
Main (compression magnet) 2 layer, water cooled, 10A (8750 A.T), iron return
Anode 1 mm. molybdenum in iron insert
Anode hole Typically 0.6 mm
Arc supply Current controlled connected to cathode
Arc voltage 500 - 1000 V ignition, 80 V during discharge
Arc current 50 - 60 A pulsed
Pulse length 20 - 150 us (by crowbar of delay line, user defined)
Repetition rate 1 Hz
Expansion magnet Encapsulated, Kapton/BN3/epoxy insulated (600 A.T)
Expansion cup Titanium with pseudo-Pierce angle, 20 mm. aperture
Polarised electrode Stainless steel held at -40 V wrt. expansion cup
Extraction By acceleration field, accel - decel
Extraction potential 92 kV (- 3kV on decel electrode)
Extraction gap 16.5 mm
Beam current 250 - 320 mA

Lead Ion Source

Type Electron Cyclotron Resonance (ECR) ECR4
Frequency 14.5 GHz
Resonance field 0.52 Tesla
Plasma chamber Water cooled stainless steel
Dimensions 66 mm. diameter, 179 mm. long
Plasma electrode aperture 16 mm
Cutoff plasma density 2.4 1012 /cm3
Longitudinal Confinement Minimum B, mirror, 2 water cooled coils
Peak axial field 1.1 Tesla
Mirror ratio 2.2
Coil current typically 1100 A
Radial confinement NdFeB permanent magnet hexapole
Pole tip field 1.2 T but with longitudinal gradient
RF power 2 kW max.
RF power source Klystron amplifier
Power injection Tuned waveguide to co-axial transition
Operation mode Pulsed, optimised for "afterglow"
Sample feed Gaseous, by injection through co-ax
Metallic, by micro-over or plasma heating
Plasma Gas Oxygen
Heating pulse length 50 ms
Useful beam length approximately 1 ms.
Repetition rate 10 (5) Hz
Extraction By acceleration field, one gap
Extraction potential 2.5 keV/nucleon (nominal)
Extraction gap 42 mm.
Beam currents Total 2 -3 mA (typically)
Analysed, >100microA Pb27+

Linac home page.
mailto Charles.Hill at with Comments and Suggestions
CEH 17/3/99.