DETECTOR CALIBRATION IN THE WAVELENGTH REGION 10-NM TO 100-NM BASED ON A WINDOWLESS RARE-GAS IONIZATION-CHAMBER

A detector calibration facility based on a rare gas ionization chamber has been built at the Electrotechnical Laboratory, Japan. We have rea lized a windowless system by applying strong differential pumping, whi ch features no spectral limitation and easy gas handling. In the auto- ionization region near the xenon absorption edge, photon flux was foun d to be underestimated and this limited the maximum available waveleng th to 92 nm. The uncertainty (1 sigma) for a Si photodiode calibration was estimated to be within +/-9% in the wavelength range 10 nm to 92 nm.