Radiation spectra of the scintillators,

Imaging Diagnostics Test at ATF

For high brightness beams the focal spot size in the interaction region can be smaller than 100 microns. Operating beams of such small spot-sizes naturally raises the question if the diagnostics resolution can be pushed to under 10 microns level. The test has been performed at the ATF (Accelerator Test Facility), to compare the response of the commonly used imaging scintillators (such as YAG:Ce single crystals) to the OTR and wire-scan diagnostics. All diagnostics were positioned on a single motorized feedthrough, and electron beam images (sizes) were obtained with all the test pieces. The results show significant image "blooming" observed with the scintillators:

The observed resolution degradation was explained as a consequence of parasitic secondary ionization, occurring in the scintillators under the direct impact of the electric field of an intense beam.