december 2007esf-workshop, athens, greece university of jyväskylä, department of physics ecr ion...
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December 2007 ESF-Workshop, Athens, Greece
University of Jyväskylä, Department of Physics
ECR ion source for the highly charged, intensive ion beams
H. Koivisto
December 2007 ESF-Workshop, Athens, Greece
Content
1. Production of highly charged ion beams (by ECRIS)
2. Present projects and challenges
3. (Metal) Ion beam production
4. Beam transport
December 2007 ESF-Workshop, Athens, Greece
What kind of ion source?
Accelerator (linear/cyclotron) gives some boundary condition!
- Continues or pulsed beam?
- A+ or Aq+(low versus high charge states)?
- Intensity requirement?
- Variety of elements? Charge breeding? Etc...
ECRIS
December 2007 ESF-Workshop, Athens, Greece
Operation principle (ECRIS)
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1) Sufficient magnetic field (including correct structure)
2) Electrons rotating in magnetic field
3) Microwaves
ECR:ElectronCyclotronResonance
December 2007 ESF-Workshop, Athens, Greece
Scaling laws (magnetic, frequency)
1) Magnetic field: Axial magnetic field Baxial by solenoids
Radial magnetic field Bradial by multipole
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VENUS
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14 GHz : 0.5 T
28 GHz: 1 T
0
1
2
3
4
-100 -50 0 50 100
Solenoid Field on axis
Sextupole only
Ion Source Axis [cm]
December 2007 ESF-Workshop, Athens, Greece
Scaling laws
2) Frequency
€
Iq ∝ f 2
R. Geller proposed:
as high microwave frequency as possible is wanted!
PROBLEM: Higher magnetic field is required!!
December 2007 ESF-Workshop, Athens, Greece
ECRIS generations
1st generation: 6.4 GHz MSU RT-ECRIS, TAMU 6.4 GHz, etc
2nd generation: 14 GHz ECRIS AECR, Artemis, Caprice, etc.
3rd generation: 28 GHz VENUS, SECRAL, several under
construction: Requires SC-technique!
December 2007 ESF-Workshop, Athens, Greece
The requirements of next generation heavy ion facilities made the development of 3rd Generation sources (and maybe 4th Generation) ECR ion sources necessary
SC-ECRIS, RIKEN, Japan
Post Accelerator
Isotope Separator
Fragmentation Production Target
Fragmentation Separator
Driver Linac (400 MeV/nuc U, 900 MeV p)
RFQ’s
Experimental Areas
“Gas Catcher”
Nuclear Structure
In Flight Separation
IsotopeRecovery
E< 15 MeV/u E>50 MeV/u
Applied Physics
Astro Physics
E< 1 MeV/u
No Acceleration
VENUS, 270 eµA U33+ and 270 eµA U34+
SPIRAL 2, GANIL, France
SECRAL, Lanzhou, China
H. Zhao
MS ECRISGSI, Germany
SuSINSCL,USA
525 eµA U35+
50-100 eµA U41+
1mA Ar12+
December 2007 ESF-Workshop, Athens, Greece
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December 2007 ESF-Workshop, Athens, Greece
Optimization of the VENUS source for Ar12+ to demonstrate the ‘tuning’ of the plasma parameters
Ar VENUS(28GHz)
eμA
12+ 860
14+ 514
16+ 270
17+ 36
18+ 1
0
200
400
600
800
2 3 4 5 6 7 8 9
Analyzed Current [eµA]
Mass to Charge
O3+
O4+
10
O5+
O6+
15
9
8
7
1112
13
14
16
O2+
6
Motivation: 1mA Ar12+ for the SPIRAL II Project
December 2007 ESF-Workshop, Athens, Greece
Comparison of different generations
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1st generation:Itot<1 mA
2nd generation:Itot= 2-4 mA
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Beyond present technological know-how!
Becr= 2 T Binj ~ 8 TBext= 4 TBrad= 4 T
ECRIS-56
December 2007 ESF-Workshop, Athens, Greece
MS-ECRIS won’t be a 4th generation ECRIS even if 56 GHz can be tested
It won’t fulfill the scaling law for the magnetic fields!
It will be a step between the 3rd and 4th generationECRIS (3.5 generation)
4th generation ECRIS requires a lot of development workfor example in the field of superconductive technique
December 2007 ESF-Workshop, Athens, Greece
Some engineering current densities
0
100
200
300
400
500
600
0 5 10 15 20 25B Tesla
Je A/mm
2
Nb3Sn at 4.2K
NbTi at 1.9K
NbTi at 4.2K
B2212 at 4.2K
B2212 at 35K
December 2007 ESF-Workshop, Athens, Greece
Peak field
Solenoid 22 T
Dipole 13 T
Quadrupole 10 T tested (4.5 T pole)
Sextupole
+ Solenoid
Need ~14T for 56 GHz
Different Nb3Sn-structures
December 2007 ESF-Workshop, Athens, Greece
From Claude LyneisCryocoolerFlangeLN Reservoir
(70 K)
LHe Reservoir (4.2 K)
50 K Shield
Cold Mass
with Coils Enclosed
Links Iron Yoke
Vacuum Vessel
Cryostat and Cold Mass
• Bremsstrahlung created in collisions of energetic electrons with the plasma chamber walls produce a high flux of x-rays.
• A fair amount of this energy is deposited in the cryostat
• With the original Al plasma chamber:
• 1 W/kW 28 GHz (only 2 W cooling power available)
• 150mW/kW for 18 GHz
• High voltage insulation deteriorates in the high x-ray flux
Warm BorePlasma Chamber
Bremsstrahlung will be a seriousproblem!
December 2007 ESF-Workshop, Athens, Greece
Challenges for 4th generation ECRIS
- superconducting wire to reach required B-field
- bremsstrahlung (heating of cryostat)
- cooling of plasma chamber (power up to tens of kW)
- efficient extraction to handle multi tens of mA beam
- coupling of microwaves to plasma
December 2007 ESF-Workshop, Athens, Greece
Production of metal ion beams
ECOS working group: “In order to meet the requirements of the future experiments with high-intensity beams, further development is needed,
especially in the production of metal-ion beams. Consequently, the development of ECR ion source will be one of the most
active areas in accelerator physics.”
Consequently a lot of human resources will beinvested in this work (very visible role during FP7)
December 2007 ESF-Workshop, Athens, Greece
High temperature ovens:
- inductively heated oven (above 2000˙C)
Different methods:
December 2007 ESF-Workshop, Athens, Greece
- resistively heated oven (above 2000˙C))
- sputtering (some refractory elements)
- laser ablation?
December 2007 ESF-Workshop, Athens, Greece
Beam transport
More beam intensity from the cyclotron is neededfor the experiments!!
Improvement of ECRIS performance does not always increase the intensity for the experiments
beam formation or/and transmission problem!!
Problem in several laboratory!
December 2007 ESF-Workshop, Athens, Greece
Statistics (2004)Total transmission efficiency
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
0,16
0,18
0 25 50 75 100 125 150 175
Intensity [µA] 14 GHz ECRIS
Efficiency2nd harmonic
JYFL 14 GHz ECRIS
Transmission efficiency decreases when beam intensityincreases!
Some reasons: 1) space charge effect (strong focusing)
2) Emittance increases with beam intensity
Icycl/IECR
December 2007 ESF-Workshop, Athens, Greece
DIMAD simulations (by X. Wu)
Beam spot in viewer according to DIMAD-simulations
Beam spot in viewer (just after dipole)
December 2007 ESF-Workshop, Athens, Greece
Hollow beam
JYFL
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NSCL
December 2007 ESF-Workshop, Athens, Greece
“ECOS” needs the development of:
- ion sources for higher intensity and higher charge states
- beam formation to produce high quality beams
- high quality beam transport facility to transport beam efficiently to accelerator
-development of metal ion beam production to make newand exotic beams available
December 2007 ESF-Workshop, Athens, Greece
Thanks to the following for providing slides for this presentation:
- Santo Gammino
- Daniela Leitner
- Claude Lyneis
- Marc Doleans