AN ALTERNATIVE APPROACH TO THE THEORY OF PHOTOCOUNTS

We discuss the formation of electron bunches in the interelectrode gap of vacuum detectors of optical radiation. This effect leads to the ex citation of electric-current spikes in an external circuit of the dete ctor, which are usually interpreted as photocounts. It is shown that t he traditional theory of photocounts is inconsistent and, in particula r, violates causality. Calculations based on the variational method sh ow that the distributed low-density electron cloud is unstable relativ e to Coulomb forces and decays into bunches. Moving in the interelectr ode gap, electron bunches are sharpened, which can be most simply expl ained on the basis of the catastrophe theory. Spatial (caustics) and t emporal (overtaking) catastrophes may occur in the electron flux. Sphe rical and linear spreadings of electron bunches under the action of Co ulomb forces are numerically simulated, and the formation of sharp pea ks of the electron density resembling pointlike particles is establish ed. Passing through the interelectrode gap, these particles can induce electric-current spikes in an external circuit of the detector, which are referred to as photocounts. The factors that increase the probabi lity of the formation of one electron clumps are pointed out. In gener al, this paper suggests an alternative to the traditional approach to the theory of photocounts.