Some Physics Processes in the Nitrogen-Filled Photoluminescence Cell - Rev. 1

As shown in Ref. [1], the photoluminescence cell is a viable candidate for monitoring the total energy in the Linac Coherent Light Source. In Ref. [1], most of the discussion was concentrated on the cell with argon as a working gas. In the present note I provide a discussion of some physics processes that may affect the performance of the photoluminescence cell with the nitrogen fill. In particular, I will consider the role of the space charge effects, ambipolar diffusion, and recombination processes. This group of phenomena determines the duration of the afterglow process that follows an initial short (<100 ns) burst of optical radiation. The presence of this afterglow can be of some significance for the detection system. Compared to my previous note with the same title UCRL-TR-222274, a more detailed discussion of space charge effects is provided, with an emphasis on the electrostatic confinement of the primary electrons. Also, some additional atomic data are included into sections describing recombination processes. The general template for this discussion follows a draft report [1] where the argon-filled cell was considered. But some processes in nitrogen are different and require separate consideration. In what follows, I am not attempting to produce ''exact'' results, but rather to provide a quick order-of-magnitude scoping study