PRESSURE MEASUREMENT METHOD USING LASER IONIZATION FOR XHV

A pressure measurement method for xhv using laser ionization has been developed. By means of nonresonant multiphoton ionization, the proport ional relation between the amount of laser-generated ions and the gas pressure is experimentally verified in the range 1 x 10(-3)-2 x 10(-8) Pa. Also, a nonresonant 4-photon ionization of the He atom, which has the highest ionization potential of all atoms and molecules, and satu rations of ionization for Xe, Kr, O2 and especially for H-2, which is a main residual molecule in uhv and xhv, are successfully observed. In addition, a high-sensitivity ion- detection system for the exact meas urement of several atoms and molecules in xhv is prepared. Noise due t o scattered laser light is discussed.