A. Ejiri

E. Ishiyama

Group CHS

H. Iguchi

K. Hanada

K. Matsuoka

S. Duorah

Y. Takase

Duorah,  S.

Ejiri,  A.

Ishiyama,  E.

Takase,  Y.

Hanada,  K.

Iguchi,  H.

Matsuoka,  K.

CHS, Group

NIFS-Repository (National Institute for Fusion Science)

§32. Development of Three Dimensional Electron Temperature Measurements Using Multi -Layer Mirror Based Soft x-Ray Spectrometer Duorah, S.I), Ejiri, A.2\ Ishiyama, E.I), Takase, Y.2), Hanada, K. 3), Iguchi, H., Matsuoka, K., CHS Group I) Dep. of Physics, Univ. of Tokyo 2) Dep. of Complexity Science, Univ. of Tokyo 3) Kyushu Univ. A 20 channel fully calibrated multilayer mirror (MLM) based soft X-ray spectrometer was installed on CHS for cen-tral electron temperature measurement.!) Using the high throughput of the MLM and the fast time response of the PIN diodes, it is possible to measure the soft X-ray spectrum with a time resolution of Ims. The slope of the spectrum gives us the electron temperature. Analysis of the observed spectrum showed that the experimentally measured soft X-ray intensity was about 50-1000 times the theoretically calculated spectrum assuming free-free pure hydrogen bremsstrahlung using the temperature and density profiles from the Thomson scattering measurements for a single discharge (Fig.l.). Moreover the spectrum simu-lated with a software XSPEC 2) showed that it is heavily con-taminated by impurity lines in the energy range of the present measurements (640 eV -' 1030eV). Figure 2 shows the simu-lated spectra 1) for a free-free pure hydrogen plasma and 2) the same spectra with contribution from impurities. The simu-lation was done with the following impurities (C (0.1 %), N(O.l %),0(3%), Fe(O.02%) , Ni(O.OOI %» fora 1 keY plasma. These values are based on a earlier study of the soft X-ray spectrum from CHS plasmas.3) Also, the slope of the spec-trum in the present range of measurement differs greatly from that of the free-free pure bremsstrahlung spectrum. Evidently, the slope of the observed spectrum wil not represent the elec-tron temperature. It can thus be reasonably concluded that the soft x-ray spectrometer with its present setup cannot be used to measure the electron temperature of the CHS plasmas. In order to explore the various ways that the soft X-ray spectrometer could be modified for temperature measurements leads to the following possibilities. The simplest is to change the range of measurement to a higher energy range (3 -' 5ke V) where there is little or no impurity radiation from the main impurities that are present in CHS plasmas. In this case, the spectrum is not sharply modified and the slope will represent the actual electron temperature. However, in this case the sig-nal to noise (SIN) ratio may not be enough for a high time resolution for CHS plasmas ( electron temperature < 2 keY) as the number of photons will be greatly reduced. This ratio can be increased by using the spectrometer to measure the spectrum of higher temperature plasmas like in LHD. Sec-ondly, as the spectrometer is very compact with a size of about 280mm(w) x 480mm(l) x 95mm(h) ( including pin hole, mir-ror, detectors) it is not difficult to install many systems for a large device. With the use of multi spectrometers viewing the plasma in both the toroidal and poloidal directions it would bepossible to measure the three dimensional electron tempera-ture. These various options are presently under study. 0.001 -- !\-'leasure . ----:rheoretical -"----, ------.. _-----._----------10·6~~~~~~~~~~~~~~~~ 600 700 800 900 1000 1100 Energy [eV] Fig.I. Comparison of the measured and theoretically calcu-lated spectrum using the temperature and density profiles from Thomson scattering measurements. > 10 ~ ~ --en --N E u --~ 0.1 o ...... o ~ 0 .01 ----- Free-free .. -........ . .............. 1.4 2 .2 3 3 .8 4 .6 Energy [ke V] Range of measurement Fig.2. Simulated soft X-ray spectrum for a 1 keY plasma for free-free and total emission. Reference 1) Ishiyama, E. Master Thesis. Univ. of Tokyo (19%) 2) Raymond, C.J. et al Astrophys. Journal Suppl. Vol. 35, (1977) 419 3) Masai, K et aI, IPP Ann. Rev. (April 1988 - May 1989) 20 253 

Development of Three Dimensional Electron Temperature Measurements Using Multi-Layer Mirror Based Soft x-Ray Spectrometer

Development of Three Dimensional Electron Temperature Measurements Using Multi-Layer Mirror Based Soft x-Ray Spectrometer

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