Contribution of residual atmosphere gases to the flux of collectively accelerated protons in a Luce diode

The contribution of residual atmosphere gases to the flux of collectively accelerated protons in a Luce diode has been determined by comparing the number of protons generated by anodes made of polyethylene and pyrolytic boron nitride. Radioactivation diagnostics based on the nuclear reactions $^{10}$B$(p,\alpha)^{7}$Be and $^{12}$C$(p,\gamma)^{13}$N has been used to determine the mean number of protons per pulse and their energy. It has been found that the number of protons accelerated collectively due to adsorption and ionization of water vapor and hydrocarbons from the residual atmosphere of the vacuum chamber on the surface of the dielectric anode insert may be comparable to the number of protons produced directly from the polyethylene dielectric anode insert.