"A New and Generic Two-Dimensional Model for Studying Channeling Radiation with Relativistic Electron Beams"

Abstract

In 2016, Fermilab Accelerator and Technology Facility (FAST) conducted an experiment to generate a discrete and potentially tunable hard X-ray channeling radiation emissions in the 40-150 KeV energy range using a new 50 MeV rated linear accelerator. There are two current models (one-dimensional (1-D) Planar and the two-dimensional (2-D) Axial model) that numerically simulate the physics involved in generating channeling radiation. FAST decided to use the 1-D Planar model in designing the experiment using a diamond crystal lattice with a (110) plane orientation. However, this study shows that the 1-D Planar model is fraught with inconsistencies and applies excessive approximations. Using this approach will obfuscate the analysis in properly identifying the mechanism that generate these discrete energy emissions. The 2-D Axial model would be a much better model to properly predict spectrum emissions energies. However, the 2-D Axial model is complex and appears to also contain unnecessary approximations as well. This study's goal was to develop a better 2-D Generic model for the experiment based on a more fundamental and accurate approach than the existing 2-D Axial model. Unfortunately the FAST experiment was unable to generate channeling radiation data. Thus, this study had to compare its 2-D Generic model predictions with the published experimental results that were based on the 2-D Axial model. Our 2-D Generic model produced a rich amount of spectrum. But, ultimately, it had poor agreement with these published experimental data results. On the other hand, the 2-D axial model provided very good agreement with their published experimental data. The failure for this new 2-D Generic model indicates two possibilities. First, the accelerator's electron beam distribution of the transverse momentum to the beam direction directly impacts spectrum data. In all published results, this beam transverse momentum distribution is unknown. Therefore, if this transverse momentum distribution was published, then a more definitive conclusion can be made on whether this model agrees with the published experimental data or not. Second, since this model is based on a more fundamental concept, the 2-D Generic model should have very good agreement. However, since the model is unable to accurately predict discrete channeling emission energies, this discrepancy indicates that there are perhaps additional mechanisms unaccounted for in the generation of channeling radiation. Attached files DATA.zip