Code for time-resolved x-ray pulse analysis at high count rates for short tokamak discharges

Abstract

The measurement of soft x-ray spectrum in fusion plasmas allows for information on the nature of electron distribution, identification of impurity contents, calculation of electron temperature, estimation of Zeff, etc. All these measurements can be performed with a semiconductor detector. By amplifying the signal and using it as input to a multichannel analyzer (MCA), the spectrum is obtained. This kind of measurement does not have the desirable property of temporal resolution unless several detection chains are used or a special hardware is developed. In this paper, a method is presented to reach that type of resolution. This method requires only one measurement chain and the substitution of the MCA for a digitizer and mass storage. The digitized signal is stored in a computer, which will be the input for the several codes developed with the purpose of performing all the tasks of an MCA. These codes allow any number of time windows, of any length, along the digitized signal. Furthermore, in this way, it is possible to process one signal several times with different input parameters. Results in the TJ-I Tokamak (R0=0.3 m; a=0.1 m; BT<1.9 T; IP<70 kA) are shown.