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 axisSextupole 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+ 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

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

0,060,08

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

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