ECR ion source for the highly charged, intensive ion beams

December 2007 ESF-Workshop, Athens, Greece

University of Jyväskylä, Department of Physics

ECR ion source for the highly charged, intensive ion beams

H. Koivisto


Content

1. Production of highly charged ion beams (by ECRIS)

2. Present projects and challenges

3. (Metal) Ion beam production

4. Beam transport


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


Operation principle (ECRIS)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

1) Sufficient magnetic field (including correct structure)

2) Electrons rotating in magnetic field

3) Microwaves

ECR:ElectronCyclotronResonance


Scaling laws (magnetic, frequency)

1) Magnetic field: Axial magnetic field Baxial by solenoids

Radial magnetic field Bradial by multipole



VENUS





14 GHz : 0.5 T

28 GHz: 1 T

0

1

2

3

4

-100 -50 0 50 100

Solenoid Field on axisSextupole only

Ion Source Axis [cm]


Scaling laws

2) Frequency

€

Iq ∝ f 2

R. Geller proposed:

as high microwave frequency as possible is wanted!

PROBLEM: Higher magnetic field is required!!


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!


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+


Optimization of the VENUS source for Ar12+ to demonstrate the ‘tuning’ of the plasma parameters

Ar VENUS(28GHz)

eμA

12+ 86014+ 51416+ 27017+ 3618+ 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


Comparison of different generations



1st generation:Itot<1 mA

2nd generation:Itot= 2-4 mA

3rd generation:Itot= 10 mAQuickTime™ and aTIFF (Uncompressed) decompressor


Beyond present technological know-how!

Becr= 2 T Binj ~ 8 TBext= 4 TBrad= 4 T

ECRIS-56


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


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


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


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!


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


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)


High temperature ovens:

- inductively heated oven (above 2000˙C)

Different methods:


- resistively heated oven (above 2000˙C))

- sputtering (some refractory elements)

- laser ablation?


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!


Statistics (2004)Total transmission efficiency

0,00

0,02

0,04

0,060,08

0,100,12

0,14

0,16

0,18

0 25 50 75 100 125 150 175Intensity [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


DIMAD simulations (by X. Wu)

Beam spot in viewer according to DIMAD-simulations

Beam spot in viewer (just after dipole)


Hollow beam

JYFL



NSCL


“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


Thanks to the following for providing slides for this presentation:

- Santo Gammino - Daniela Leitner - Claude Lyneis

- Marc Doleans

ECR ion source for the highly charged, intensive ion beams

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