MULTIPOINT ND THOMSON SCATTERING ON HT-7 27 th EPS Conference on Controlled Fusion and Plasma Physics BUDAPEST, HUNGARY, 12-16 JUNE 2000 ASIPP HT-7 MULTIPOINT ND THOMSON SCATTERING ON HT-7 J. Mao, J.Zhao, Y.D.Li, A. Xie, Z. Fang, V.Sannikov* A. Gorshkov* Institute of plasma Physics, Academia Sinica, Hefei, Anhui, 230031, P.R.China. * PRC Kurchatov Institute, Moscow 123182. RUSSIA

ABSTRACT ASIPP HT-7 A compact, low cost, multipoint Thomson scattering diagnostic for HT-7 Superconducting Tokamak has been in operation. Its capability of measuring electron temperatures is 200ev to 2kev at densities of a few times 1012 cm-3, a spatial resolution of 2.4cm for 5 spatial points and a temporal resolution of 1ms-1s for 8 time points. The major components consist of 20-25J Nd:glass laser with 35ns width (8 pulses per burst), KDPdoubling unit; Spherical mirrors of multipass input optical system; wide-angle collection objective, bandpass glass filter for reducing the stray light to zero; f/2.5 polychromator, the fiberglass collimator, the photomultiplier’s box with electronic preamplifier, high gain and high signal/ noise ratio, CAMAC data acquisition and so on. The multipass optical system has been successful for increasing the quantity of scattered photons by laser beam passes 10 times through plasma. The HT-7 Thomson scattering diagnostic has provided successfully the information on two dimensional electron temperature in the plasma of HT-7 tokamak with LHCD and IBW heating.

Layouts of HT-7 T.S. HT-7 KDP PMT CALIB filter CAMAC 2250 FIBER PLCRO. ASIPP HT-7 KDP filter CALIB PLCRO. PMT CAMAC 2250 HT-7 FIBER BAND FILTER PRISM OSILLATOR AMPLIFIER POWER SUPPLY

PARAMETERS of HT-7 T.S. Te~0.2-2keV; Nelim > 2  1012 cm-3 ASIPP HT-7 Te~0.2-2keV; Nelim > 2  1012 cm-3 Spatial resolution : 2.4cm for 5 spatial points (0, 4cm,8cm,12cm,16cm) Temporal resolution : 1ms-1s for 8 points Nd Laser: Nd:glass laser, 20-25J1.06,4J0.53 (KDP doubling), width 35ns 1 or8 pulses.

PMT lens spherical mirrors Laser Prism Filter FIBER COLLECTOR

COMPONENT Nd Laser Optical system Polychromator and PMT ASIPP HT-7 Nd Laser Optical system Polychromator and PMT Fibelglass collimator Data Acquisition,CAMAC Filter and Multipass Calibration System

Nd:glass Laser System Oscillator ; an Amplifier; KDP crystal; ASIPP HT-7 Oscillator ; an Amplifier; KDP crystal; Energy meter;Glass filter to cut off light of 1.06 Laser room

OSCILLATOR * Ring resonator very stable ASIPP HT-7 * Ring resonator very stable * LiF crystal with colored,Qswitch * 50mJ, 40 nsec., line width<0.01Å Operate in a TEMoo *Two opration model. 1Hz repetition1 or 8 pulses * Dove prism with Brester’s angles.Light beam is rotated inside the resonator along the optical axis reduce the thermal stress which are accumulated during the operation

AMPLIFIER * Telescopic resonator 7 passes ASIPP HT-7 * Telescopic resonator 7 passes * LiF-2 plate with corored for Q switch,width 35ns for protecting the master oscillator from back-emission * Increasing laser power density by KDP’s nonlinear process.

POLYCHROMATOR * Transmission about 0.7-0.8 * Wide-angle collection ASIPP HT-7 PMT GRATING OBJECTIVE FIBER COLLECTOR * Wide-angle collection objective (F=200mm) * f=1/2.5 * Transmission about 0.7-0.8 * Diffraction grating 600 L/mm, 1515cm2

PHOTODETECTORS * 25 Pieces ( 5 x 5 ) * S-20 PHOTOCATHODE ASIPP HT-7 * 25 Pieces ( 5 x 5 ) * S-20 PHOTOCATHODE * Quantum Efficiency (5300Å ) , 10%-12% (6943Å~3%) * 12 Dynodes Dnode dark Current ~ 10-8 * High Gain * Preamplifiers: 50times, Bandpass: 0.15-35MHz S20

BANDPASS GLASS FILTER * Two pieces installed frond of ASIPP HT-7 * Two pieces installed frond of the input fiberglass guides * Reduce the stray light to zero * Special glass filter used cut off of laser radiation(1.06μ) * High damage resistant for high power laser

MULTIPASS OPTICAL   E=E0(1+R+R2+R3+....R9)==9.8EO ASIPP HT-7 lens spherical mirrors Laser Prism Filter   E=E0(1+R+R2+R3+....R9)==9.8EO  Two spherical mirrors R>>D 2R=3.2m, D=0.052m * Two pieces installed frond of the input fiberglass guides Reduce the stray light to zero  Success for Lager Device firstly

CALIBRATION SYSTEM  Optical Path Alignment (HeNe and Laser) ASIPP HT-7  Optical Path Alignment (HeNe and Laser)  Energy Calib. (Energy Meter)  Spectral Calib. (Hg lamp)  Spatial position Calib. (movable target)  Sensitivity of 25 Channel (Tungsten Lamp) Tungsten Lamp lens chopper fiber Photodiode To CAMAC

FLOW CHART OF THOMSON SCATTERING SYSTEM ASIPP HT-7

Profile of Te(r) ASIPP HT-7

High Te0 ~ 1KeV during LHCD Te by T.S compare with Te by ECE ASIPP HT-7

Profile of Te(r) ASIPP HT-7 IBW250kw LHCD420kw

Ip=130KA, Ne~1.51013/cm3 with IBW 150kw ASIPP HT-7 600ms Te by SXS 450ms 33051 600ms 33055 Te by T.S.

SUMMARY ASIPP HT-7 The multipass optical system has been successful for increasing the quantity of scattered photons. The HT-7 Thomson scattering diagnostic has provided successfully the information on two dimensional electron temperature and density profiles in the plasma of HT-7 tokamak with LHCD and IBW heating.

SUMMARY ASIPP HT-7 The multipoint Thomson scattering diagnostic for HT-7 Tokamak has been in operation. Nd Laser: Nd:glass laser, 20-25J1.06,4J0.53; 1 or 8 pulses. Optical system is very stable. System stray light was reduced to near zero by Two pieces of glass filter. The ratio of noise to signal is < 5%.