FIDA Diagnostic

•Diagnostic for FAST IONS : it measures the vertical component of perpendicular energy

•Processes generating fast ions –Beam–ICRH heating–Nuclear reaction

Beam-Plasma Interaction

2

Collisional ionization

beam + plasma e

plasma neutrals

(halo neutrals)

CXRS

beam + plasma ions

beam ion

Re- neutrals

CXRS

+ beam

D emission from neutrals

Neutral

population

Energy Atomic

Processes H

Beam 80 KeV Electron collision

Doppler shift

(60A)+ Stark splitting (10A)

Edge plasma

10 eV Electron

collision

unshifted

Halo neutrals

Plasma energy

CXRS(plasma ions-beam)

shift Doppler (15 A? for 5keV)

Re-neutrals

Energetic ionsNo Mawelliana

CXRS (ions beam- beam)

Broad + shift Doppler (max 60 A)

Radiation signal

Undesired Signal Signal substruction

D spectral line

•Beam(Doppler shift canceled by View at 90)

•Edge plasma

•Halo neutrals

putting a mask in front of CCD

Background

visible Bremsstrahlung

impurity spectral lines

Working with a modulated beam

D from Re-neutrals ONLY signal to analyze

LENS COLLECTION

f/number: f/4.4

OPTICAL FIBERS

1.5 mm core diameter

SPECTROMETER SP-2356 CZERNY-TURNER

f/number: f/4

300 mm focal lenght

1800 grooves/mm grating

CCD VELOCICAM VC105A

rate readout: 2.2 MHz14 bits

chip:8*6 mm2

area image chip:652 vertical columns with 488 pixel

Wavelenght range is = 6470 - 6630 Å Spectral Resolution: 5 Å

PROTOTYPE INSTRUMENT

5

CONTAMINANTS IN THE SPECTRUM

Lines

ImpurityOrigin Elimination

B V

C VI

Excited by charge exchange

By beam modulation and time slice subtraction

O V

C II

O IV

Noncharge exchange lines

By fitting a theoretical response function

Fitting of a theoretical response function

The theoretical response function radiated by the impurity is the convolution of:

• the Gaussian line shape radiated by the impurity

• the instrumental response (taken by illuminating the fibers with a neon lamp and represented by the sum of three Gaussians)

Spectrum from re-neutrals

• Born by CXRS fast ions-beam

• Not Maxwellain distribution function

• D spectrum much broader with a

non- Gaussian shape

Rotational velocity

• Measurement vector

with parallel and orthogonal direction to magnetic field

• Doppler shift

• Ion energy con

• For view line orthogonal to B 0||

1||||ˆˆˆ bb

1||ˆ,ˆbb

c

vv

cv 1||||ˆˆ

22|| )1( pp

EE

v

vp ||

1

21 pE

E

For view line orthogonal to B

• For vz = 2.4 106 m/s --> Ez = 60 KeV

a)

b)

Any value of

Any ion with energy

KeVE 60 smv /104.2 6

KeVE 80smv /108.2 6

31

v

B

vz

Fast ion

Fast ionB

vza) b)

v

0

||v

)1/( 2pEE

The success of FIDA is based on

• Vertical views ( Doppler shift only due to gyromotion of fast ions)

• Blocking bar ( avoiding CCD saturation)

• Beam modulation ( for substructing background)

• High quantum efficiency CCD ( for good S/N)

Spectrometers + CCD: characteristics

OMA HRS FIDA

Focal (mm) 500 300

F# 8 3 4.4

grating 2400-1200-150 300 g/mm

(echelle)

1800

1/D(A/mm) 7-13-133 2.8 14

Spectral resolution(A)

0.015 - 0.06 - 0.5 0.05 5

Slit aperture 20 40 100

CCD pixels 1340 x 400 760 - 290 652 x 488

Pixel size 20 17 x 34 12