Photometric calibration of soft x-ray and p-terphenyl coated visible photodiodes in the 180-1500 eV range for fusion plasma spectroscopy

The efficiencies of x-ray ultraviolet silicon, and p-terphenyl coated visible photodiodes have been measured in the 180-1500 eV range using a K radiation-Manson source. It is found that the quantum efficiency (electrons/photon) of the silicon diode varies between 25 and 400 in the above-mentioned range; the p-terphenyl coated diode is by two orders of magnitude less performing at the high-energy end of the range considered, but approaches the efficiency of the silicon diode at 100 Å. Such diodes with built-in amplifiers, coated with scintillator and thin layers of metal films, can be efficiently used in spectroscopic diagnostics of magnetically confined plasmas.