The MOSS Camera on H-1NF

Clive MichaelJohn Howard

PRL,RSPhysSE,ANU

Outline:•MOSS (Modulated Optical Solid-State Spectrometer)

•Camera imaging

•Results and interpretation

acknowledgements:B. Blackwell, A. Cheetham, R. Davies, J.

Wach

Instrument measures: Spectroscopic measurement of ION/ATOM:

TEMPERATURE

FLOW SPEED

SPECTRAL LINE INTENSITY SPATIAL & TIME RESOLVED VIEWING CHORD EMISSION WEIGHTED spectroscopically, from DOPPLER

BROADENING of transition radiation

dl)x~(I

dl)x~(T)x~(I

T

L

LL

dl)x~(I

ld )x~(v )x~(I

v

L

LL

,...)T,n(fI eeL

MOSS Spectrometer is a Pockel’s cell

Fixed delay, modulated Fourier transform spectrometer

wavelength

nceBirefringeLengthN

)t2sin(NNN 10

N0 ~ 1000-5000,

N1 =1/4 CEBB 0

cos12

II 0

Fringe contrast

Fringe phase

t2sin10

Measurement principle

Contrast => Temperature Phase => Flow

Achieves 2-D Imaging Light collection simple

MOSS has capability for a wide field of view Camera takes advantage of this

Compact and simple MOSS uses large aperture optics,

Grating spectrometer images through very thin slit

Motivation for camera: to have multi-channel experiment

Camera Imaging principle

Field of View and etendue

Contrast rolls of slowly.

Contrast falls off fast!

Usable field of view

Phase pattern in detector plane

Field of View and etendue

Specifications

Field of View plasma: 6 deg

Number of Channels: 16Aperture: 50mmSpectral Resolution : 1/5000(configurable from 1/20000 to 1/1000)Detector array: Multi-anode PMT

1

pplasma

2

Dcamera f

X;

f

X f1 is fixed. f2 is

chosen so that camera = plasma

Instrumentation

polarisingbeamsplitter

InstrumentCalibration light[expanded,diffused laser]

ligh

t fro

mpl

asm

a

40-50Khz Sine wave F

CAMACDIGITISERSYSTEM

COMPUTER FORSIGNALDEMODULATION

FUNCTIONGENERATOR

AUDIOAMPLIFIER

HIGH VOLTAGETRANSFORMER

LITHIUMNIOBATECRYSTAL

OP

TIC

AL

FIB

RE

AR

RA

Y

BANK OFPHOTOMULTIPIERTUBES

8 X F

Shutter synchronisedwith machine controlsystem

MULTI-CHANNELPMTDETECTORARRAY

OR

2kV 0-peak sinewave

A Typical Temperature Profile

Ti Profile “Hollow” implies ion heating in edge

Centre Ti rises slower than edge Ion-Ion equilibration time: 2ms: comparable to rise

time in centre Ions are heated at edge and heat diffuses towards

centre

Aside: potential profile evolves on same timescale as Ion temperature

Abel inversion: Projection->Profile

CameraFIR

Interferometer

l

ll

ll

dl)(I

dl)()(I

dl)(II Light intensityFringe contrast (Temperature)

Double inversion necessary

n

1iiie )(Fa)(n,,I

Transport studies: Assume flux surfaces have same T, I, ne

Combine MOSS Camera and FIR interferometer for studies of

Force balance Ion transport studies (RF modulation, ...)

Conclusions

MOSS Camera has etendue orders of magnitude higher than traditional grating spectrometers

Field widening improves FOV by ~15 Interesting and (Challenging) results

=> Hollow temperature profile Low rotation

Radial profiles -> Transport studies RF modulation Why are ions hot?