Atomic collisions in fusion plasma physics

An introduction to the course Atomic Physics in Fusion, ED2235

Henric Bergsåker 26 Oct 2011

Atomic collisions in fusion

• Atomic collisions and plasma performancePlasma resistivity and ohmic heatingRadiative coolingTransport

Collisions in edge plasma physicsIon implantation and backscattering at surfacesSputtering at surfaces

• Diagnostics involving atomic collisions• Types of collisions• Classical mechanics vs Quantum mechanics• Key quantities• Course outline and schedule

Plasma resistivity

E J1/ 2 2

2 3/ 20

ln0.51

3 (2 )e

se

m e

T

2j j

js s eff

j jj

n Z

Zn Z

2P j

The plasma resistivity is due to elastic collisions

Radiation losses

loss Z e zZ

P L n nIn a low density plasma the chargestate distribution and radiating powerdensity depends on electron impactionisation and excitation.

Plots: Y. Ding, Master thesis KTH 2008

Transport and collisions2

c

D

Classical diffusion

Neoclassical diffusion2 2

3/ 2c

qD

Parallel transport on open field linesis important for impurity control witha divertor. Impurities created in thedivertor are confined there by thecollisional friction drag by the majorityion flow towards the divertor plates.

Backscattering at surfaces

Upper: H -> CW.Eckstein et al.

Lower: C -> CH. Bergsåker et al.

Ion implantation

W. Eckstein et al. 2005

Physical sputtering

Upper: few collisions view, J. Bohdansky.

Lower: Monte-Carlo (TRIM), W Eckstein et al.

Modelling of deposition in castellation gaps.Experiments in TEXTOR

A. Litnovsky et al. , PSI San Diego

X-ray tomography

m/n=1 mode behaviour during sawtooth activity in the HT-7 tokamak.

T.P. Ma et al. Phys. Lett. A361(2007)136.

Neutral particle analysis

The central ion temperaturecan be measured by neutral particleanalysis.

M. Bagatin et al. Fus. Eng. Design25(1995)425.

Charge exchange spectroscopyStudies of fully stripped OfollowingH0+O8+ -> H++(O7+)* R.C. Isler et al. Nucl Inst. Meth. B9(1985)673.

Charge exchange spectroscopy

Fast CXRS in JT-60U.Measurements of Ti and grad Ti

using a line in the C5+ spectrumAfter H0+C6+ -> H++(C5+)* M. Yoshida et al. Fus. Eng. Des.2009 in press.

Impurity and H flux from emission spectroscopy

The images show hydrocarbonemission from the divertor regionof DIII-D.In principle the flux density ofneutrals entering the plasma canbe measured spatially resolved inthis way.

M. Groth et al. J.Nucl.Mater 363-365(2007)157.

Atomic beam edge diagnostics

Observation of three lines in neutral He.The intensity ratios give both Te and ne

B. Schweer et al. J.Nucl.Mater. 266- 269(1999)673.

Important types of collisions

• Elastic collision• Bremsstrahlung• Electron impact ionisation• Electron impact excitation• Radiative recombination• Dielectronic recombination• Charge transfer

e H e H H A H A

e H e H h

(1 )e H s e e H ( 1)q qH A H A h

( ) ( )e H i e H f

e H H h ( 1) ** ( 1) *q q qe A A A h

H H H H ( 1)q qH A H A h

Classical vs Quantum mechanics

Intended learning outcomes

• Recall definitions of basic concepts in atomic physics and the size of key atomic quantities

• Apply methods of wave mechanics and classical mechanics&electrodynamics to problems in atomic physics

• Explain the significance of different approximations when estimating atomic quantities

• Predict the general behaviour of fusion relevant atomic physics quantities based on dominating physical mechanisms

• Construct simple numerical or analytic models of fusion plasma phenomena with input from atomic physics databases

• Present and discuss fusion related atomic physics material, both in writing and orally

Having completed the course you should be able to:

Schedule

sem = seminar room 1419, Teknikringen 31kosm= kosmos, top floorHenric Bergsåker, henricb@kth.se, 08-7906094, 073 9850300

Tentative schedule

Examination

• Five assignments, solving problems and discussing fusion plasma physics issues involving atomic physics (50%)

• Presentations (10%)

• Final written examination: basic facts, solving problems, discuss the physics (40%)