Using beryllium and polypropylene-aluminium absorbers to measure the TBR-1tokamak electron temperature

Beryllium foils of different thickness have been employed for measuring the electron temperature in tokamaks using the absorbing method based on ratio of the bremsstrahlung intensities, emited by the plasma.. However, in the case of small tokamaks with low electron temperatures, such as TBR-1, the f oils must be very thin, becoming very fragile, hard to handle and with insu fficient absorbing power of line radiation from impurities. Also they are v ery expensive. In this work, we have investigated whether other absorber ma terials, obtained by depositing Aluminium on polypropylene films, for examp le, could give similar results. These new kind of filters have good mechani cal properties and are light. tight, as opposed to the thin beryllium foils which have shown, very often, the presence of pinholes. Also, the attenuat ion of the line emission from impurities, with the use of such filters, is more effective. Silver foils have also been manufactured and used, but with unsatisfactory results due to the TBR-1 low plasma temperature. However, s ilver foils should be considered a good candidate for measuring T-e through the absorbing method in large tokamaks with higher plasma temperatures.