The Geiger discharge revisited Part IV.: The fast component

The mechanism of the self-quenching Geiger counter has been understood, in general terms, for over half a century. However, quantitatively, one aspect of the discharge has not been satisfactorily accounted for. This is the fraction of the signal that is “fast” in the sense of being contemporaneous with the avalanches that propagate the discharge, as opposed to the “slow” fraction that is due to the drift of the positive ions, produced in the avalanches, towards the cathode. The standard theory suggests that the fast fraction is of the percentage order whereas experimentally, as has also been known for half a century, it is of a few tens of percent. The resolution of the problem lies in consideration of the space-charge effects within individual avalanches following which the fast component is satisfactorily accounted for.