We report the results of the first laser high-power measurement comparison between the Physikalisch-Technische Bundesanstalt (PTB, Germany), and the National Institute of Standards and Technology (NIST, USA). Laser power transfer standards were calibrated at both national standards laboratories between 82 W and 127 W at 1.06 µm and between 85 W and 554 W at 10.6 µm. Relative agreement between the standards of the two laboratories was demonstrated to lie between 5 10 -3 and 7 10 -3 , which is well within the combined uncertainties.

A method is described to derive a radiometric scale for laser pulse energies from a scale for CW laser power. The transfer standard used is a commercial glass-disk calorimeter. The sources of measurement uncertainties have been studied and methods for the experimental determination of corrections are described. The achieved relative uncertainty of the scale is about 0,15%.

The operation of streamer chamber has been studied by application of image converter and image intensifier. The high voltage pulse was produced by a Marx generator (pulse duration about 15 ns), the primary ionisation was generated by gasionizing radiation emitted by a spark lamp. There exist two modes of operation: 1. When only about one primary electron per 2 cm was available, the discharges were identified as to be avalanches, which developed into anode-and cathode-directed streamers, as soon as critical amplification was attained. The first 5 ns after beginning of streamer mechanism, when E/p was large, streamer propagation depends strongly on E/p; the velocity of anode-directed streamer is somewhat larger than that of cathodedirected streamer. When pulse magnitude decreases strongly, the streamer velocities become nearly independent of E/p.2. Starting with about 100 electrons/cm, one gets tracks, which emit sufficient light for direct photography. The tracks are parallel to the direction of the ionizing radiation and are caused by overlapping of the local avalanches initiated by the primary electrons.

No abstract

No abstract