characterization of nonneutral plasmas confined in a gabor...

Characterization of Nonneutral Plasmas

Confined in a Gabor Lens

Kathrin Schulte

IAP Workshop 2012

NNP Non Neutral Plasma

Physics Group

NNP Non Neutral Plasma

Physics Group

Accelerator Physics

Gabor Lens Electric Space Charge Field Focussing Force

z

r

beam

• proposal by D. Gabor in 1947

• linear electric space charge field in case of

homogeneous electron density distribution

• focussing independent of ion mass

• space charge compensation

NNP Non Neutral Plasma

Physics Group

Plasma- and Astrophysics

• nonneutral plasma properties: ne=1014-1015 m-3, Te=100-1000 eV

• study of plasma properties under laboratory conditions

• investigation of new diagnostic techniques

NNP Non Neutral Plasma

Physics Group

Gabor Plasma Lens

solenoid

ground electrode

anode

solenoid

ground electrode

NNP Non Neutral Plasma

Physics Group

Confinement Principle

Radial force balance for an axicentred,

circular electron orbit:

electrostatic +

centrifugal force

electron

magnetic force

orbit

Radial Confinement Longitudinal Confinement

Potential depression by confined

electrons:

NNP Non Neutral Plasma

Physics Group

Space Charge Lenses at IAP

NNP Non Neutral Plasma

Physics Group

Electron Production

1. Several residual gas atoms are ionised by natural radioactivity or

cosmos radiation in the lens volume.

2. In the electric field the produced residual gas ions are accelerated

out of the Gabor Lens and on their way they are able to ionise

other residual gas atoms.

3. Additionally secondaries are produced by the interaction of

particles with the surface of the electrode.

4. In case of use as focussing optics electrons are produced by

beam ions.

Study of production and loss

mechanisms on the basis of

emitted xray radiation.

Bachelor Thesis, Stephan Klaproth

NNP Non Neutral Plasma

Physics Group

Electron Density Measurement Scheme

Trajectories of Emitted

Residual Gas Ions

Peak 1

Peak 2

Detected Ion Energy

Distribution

Potential Depression

by Confined Electrons

Localization of Production

Mean Electron Density

ne

integrated

over z

B=10,6 mT

p=4,8e-4 hPa Datei: 23082007

2

04

ern A

e

NNP Non Neutral Plasma

Physics Group

Temperature Measurement Scheme

Optical Emission

Cross Section:

Measurement Scheme Ratio of Emission Cross Sections

John B. Boffard et al., University of

Wisconsin, 2004

NNP Non Neutral Plasma

Physics Group

Time-resolved Diagnostics

Measured Ion Current

Measured Intensity

Time-resolved Measurement of an Instability

=3400V

B=12 mT

p=7,9-4 hPa (He) Datei: 18072011

Bachelor Thesis, Benjamin Glaeser

NNP Non Neutral Plasma

Physics Group

Experimental Set-up

Gabor Lens

Beam

Transformer

Beam Dump FDC

+

Beam Transformer

Slit-Grid Emittance Scanner

HV Gap

MUCIS

Ion Source

HV Terminal

beam parameters:

pulse length=1,25 ms, rep. rate=1 Hz

NNP Non Neutral Plasma

Physics Group

Excerpt from the Results

rms,100%=0,170 p mm mrad

IDT1=30 mA

rms,100%=0,247p mm mrad

IDT1=35 mA

A=0 kV, Bz= 0 mT A=9,8 kV, Bz= 10,8 mT

Beam parameters:

Ar1+, 3,1 keV/u

NNP Non Neutral Plasma

Physics Group

Thank you for your attention!