SHORT-PULSE PHOTOEMISSION FROM A TRIOXIDE CATHODE UNDER THE FUNDAMENTAL, THE 2ND, 3RD AND 4TH HARMONICS OF A PICOSECOND ND-YAG LASER

We present experimental results concerning the properties of a standar d thermionic trioxide cathode covered with BaO, CaO and SrO and workin g at ultra short pulses at room temperature. A picosecond Nd: YAG lase r is used at fundamental frequency and with harmonics up to the fourth , delivering 35 ps pulses, and with a d.c. electric field applied betw een the cathode and the anode. The work function of this cathode is lo w, W(phi) = 1.1 eV, leading to photoemission when submitted to HBARome ga1 = 1.17 eV. For HBARomega3 = 3.51 eV and HBARomega4 = 4.68 eV the q uantum yield value is eta greater-than-or-equal-to 1 x 10(-3). From th ese experiments, it appears that particular physical phenomena, depend ing on the creation of excitons and on the porous structure of the emi tting layer, increase the temporal pulse width of the emitted current up to nanoseconds.A thermal assistance T congruent-to 90-degrees-C, pe rmits us to limit these effects.