  At the Advanced Superconducting Test Accelerator (ASTA) now under
construction at Fermilab, we anticipate the appearance of the microbunching
instability related to the longitudinal space charge (LSC) impedances. With a
photoinjector source and up to two chicane compressors planned, the conditions
should result in the shift of some microbunched features into the visible light
regime. The presence of longitudinal microstructures (microbunching) in the
electron beam or the leading edge spikes can result in strong, spatially
localized coherent enhancements of optical transition radiation (COTR) that
mask the actual beam profile. Several efforts on mitigation of the effects in
the diagnostics task have been identified. At ASTA we have designed the beam
profiling stations to have mitigation features based on spectral filtering,
scintillator choice, and the timing of the trigger to the digital camera's CCD
chip. Since the COTR is more intense in the NIR than UV we have selectable
bandpass filters centered at 420 nm which also overlap the spectral emissions
of the LYSO:Ce scintillators. By delaying the CCD trigger timing of the
integration window by 40-50 ns, we can reject the prompt OTR signal and
integrate on the delayed scintillator light predominately. This combination of
options should allow mitigation of COTR enhancements of order 100-1000 in the
distribution.
