NNP Non Neutral Plasma

Physics Group

Focusing of Intense Heavy Ion Beams

with Plasma Lenses

Oliver Meusel

12th Heavy Ion Accelerator Technology Conference

NNP Non Neutral Plasma

Physics Group

Historical Remarks

Proposal of a SCL by Gabor, July 1947

Electrical & Electronic

Engineering Department,

Imperial College London

NNP Non Neutral Plasma

Physics Group

Space Charge Lenses

high field Gabor lens for beam energies up to 500keV

lens properties:

FA,max = 6.5kV

Bz,max = 48mT

lens properties :

FA,max = 65kV

Bz,max = 220mT

Gabor lens for beam energies up to 50 keV

NNP Non Neutral Plasma

Physics Group

Radial Confinement

m v

reE ev B

e e,

2

r e, z

e

e,v

r

pe

22

e

0 e

e n

m

ez

e

eB

m

plasma frequency

cyclotron frequency

angle velocity

Er given by Poisson equation:

1

r rrE

en (r)r

e

0

integration for 0 < r < Rp :

E1

2en rr

0

e

e

pe

e e

2

2

2

radial force balance equation

NNP Non Neutral Plasma

Physics Group

Radial Confinement

maximum density by a trapping efficiency of

2

1

2

2

)2

1(12 e

peee

solution:

e

ze

e

pe

rm

Bn

21

2 2

0

2

2

r 1

e ee

2

r 1

e

pe

2

r

z

e e2

E

rB ;

NNP Non Neutral Plasma

Physics Group

Longitudinal Confinement

Freen r

2

04

1 2

2

0r r r

en rr r e

F F ( )

integrated for 0 < r <Rp

maximum density at F Fanode r

Fr is determined from Poisson‘s equation:

2

04

ern A

e

F

longitudinal potential well

NNP Non Neutral Plasma

Physics Group

Numerical Simulation

e

zA

m

Ber

8

22

F

y

x z

pz

GabLensM2

• kinetic description

• dynamic processes

• 3D-Particle-In-Cell Simulation

GaborM

• fluid description

• steady state

two different simulation methods

NNP Non Neutral Plasma

Physics Group

Focusing Strength

mv

qgk

mv

qBk

2

2mv

qgk

time

comparison of focusing strengthes

MSQ / ESQ

strong

focusing/defocusing

SCL

strong focusing

Solenoid

weak focusing

be

z

Wm

qeBk

8

2

NNP Non Neutral Plasma

Physics Group

Comparison of Focussing Strengthes

e

i

ii

be

z

m

m

vm

qBk

Wm

Bqk

2

8

22

Filling degree depends on:

• electron temperature

• loss and production rates

NNP Non Neutral Plasma

Physics Group

Beam Transport Experiments

Preasure measurement

& control

Gabor lens

Faraday Cup

Beam dump

500 L/s Turbo Pump

Emittance Scanner

focussing of micro bunches passing a

Gabor lens @ 108MHz, Df = 60°

NNP Non Neutral Plasma

Physics Group

Experiments Using Ion Beams

measurement of the electron density

using an ion beam

1

40

2

0f

x

xk l

en l

W

e

b

D ' ,exp

r

e

e theo

n

n

.exp

,

beam properties:

Wb = 110 keV/u

I = 1.2 mA

He+

p = 10-7 hPa

NNP Non Neutral Plasma

Physics Group

Beam Emittance Growth

rms x x xx 2 2 2' '

D

rms

rms out

rms in

,

,

characterisation of lens aberration by

estimation of emittance growth

beam properties:

Wb = 110 keV/u

I = 1.2 mA

He+

p = 10-7 hPa

NNP Non Neutral Plasma

Physics Group

Planned Experiments

NNP Non Neutral Plasma

Physics Group

High Field Gabor Lens

HF-GL prototype for HSI upgrade

lens properties

ranode : 85mm

Bmax : 50mT

Fmax : 50kV

• ceramic insulator

• HV-contacting

• UH vacuum sealing

DN CF 160

NNP Non Neutral Plasma

Physics Group

Performance Test of the HF-GL

emitted bremsstrahlung spectra

NNP Non Neutral Plasma

Physics Group

Electron Clouds under XHV Conditions

loss and production rates at preasures below 10-12 mbar

Is it possible to use a Gabor - lens in a cryogenic interior?

SC-CH Cavity SC-Gabor lens SC-Gabor lens

Cryostat

NNP Non Neutral Plasma

Physics Group

Thank you for your attention.

NNP Group

http://nnp.physik.uni-frankfurt.de

http://hicforfair.de