LCLS Spontaneous Radiation with Reflection along the Beam Line in the Undulator Pipes

Some commissioning and alignment procedures for XTOD may rely on the use of the spontaneous radiation. Therefore we have modeled the spontaneous radiation between the Undulator and the Near Experimental Hall to derive numerical values of the expected beam width and of the energy deposition. The values are then used to determine aperture sizes and detector sensitivities. We performed the calculations in three stages. The first was to generate an appropriate distribution of photons within the Undulator. The second was to simulate the emergence of the photons from the Undulator. The third was to propagate the photons (without any obstructing objects) to various points along the Z-axis up to the Near Experimental Hall entrance. We performed the simulations for low and high energies based on the spectral flux data supplied by Sven Reiche. These data sets were at 71 meters from the end of the Undulator for 4.5 and 14.08 GeV electrons