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
beam + plasma ions
beam + plasma e
CXRS
plasma neutrals
(halo neutrals)
Collisional ionization
beam ion + beam
CXRS
Re- neutrals
2
Da emission from neutrals
Neutral
population
Energy
Atomic
Processes
Ha
Beam
80 KeV
Electron
collision
Edge
plasma
10 eV
Electron
collision
Halo
neutrals
Plasma
energy
CXRS
shift Doppler
(plasma ions-beam)
(15 A? for 5keV)
Reneutrals
Energetic
ions
CXRS
(ions beam- beam)
Broad + shift
Doppler (max 60 A)
No Mawelliana
Doppler shift
(60A)+ Stark
splitting (10A)
unshifted
Radiation signal
Da from Re-neutrals ONLY signal to analyze
Undesired Signal
Signal substruction
Da 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
PROTOTYPE INSTRUMENT
LENS
COLLECTION
f/number:
f/4.4
OPTICAL
FIBERS
1.5 mm core
diameter
SPECTROMETER
SP-2356 CZERNYTURNER
CCD VELOCICAM
VC105A
f/number:
f/4
300 mm
focal
lenght
rate readout: chip:
2.2 MHz
8*6 mm2
14 bits
Wavelenght range is  = 6470 - 6630 Å
Spectral Resolution: 5 Å
1800
grooves/mm
grating
area image
chip:
652 vertical
columns with
488 pixel
5
CONTAMINANTS IN THE SPECTRUM
Lines
Impurity
BV
C VI
OV
C II
O IV
Origin
Elimination
Excited by charge By beam
exchange
modulation and
time slice
subtraction
Noncharge
By fitting a
exchange lines
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
• Da spectrum much broader with a
non- Gaussian shape
Rotational velocity
• Measurement vector ˆ  ||bˆ||  bˆ1
with bˆ|| , bˆ1
parallel and orthogonal
direction to magnetic field
• Doppler shift
• Ion energy E 



ˆ  vˆ || v||   v1

c
E
(|| p  
c
v||
p
con
v
1  p 2 )2
• For view line orthogonal to B   1 ||  0
E
E
1  p2
For view line orthogonal to B
• For vz = 2.4 106 m/s --> Ez = 60 KeV
a)
E  60 KeV
b)
E  80 KeV
vz
a)
v
B
Fast ion
v  2.4 106 m / s   0
v  2.8 106 m / s   31
b)
vz
v
B
Fast ion

Any value of v||
Any ion with energy
E  E /(1  p 2 )
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
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
0.05
5
40 m
100 m
Spectral
0.015 - 0.06 - 0.5
resolution(A)
Slit aperture
20 m
FIDA
CCD pixels
1340 x 400
760 - 290
652 x 488
Pixel size
20 m
17 x 34 m
12 m