Some Physics Processes in the Nitrogen-Filled Photoluminescence Cell

The photoluminescence cell is a viable candidate for monitoring the total energy in the Linac Coherent Light Source [1]. 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. The general template for this discussion follows a draft report 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