RARE-GAS OPTICS-FREE STABLE EXTREME-ULTRAVIOLET PHOTON SPECTROMETER FOR SOLAR-SYSTEM STUDIES

We have developed a prototype spectrometer for space applications that require long-term stable EUV photon flux measurements. In this recent ly developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking ad vantage of the photoelectric effect in one of several rare gases at lo w pressures. Using an electron energy spectrometer operating at a few electron volts, and followed by an electron multiplying detector, puls es due to individual electrons are counted. The overall efficiency of this process is essentially independent of gain drifts in the signal p ath, and the secular degradation of optical components that is often a problem in other techniques is avoided.