50 likes | 136 Views
RF backgrounds on TOF1/2. M. Bonesini INFN Milano Bicocca. MICE setup: cooling + diagnostics. Cools and measures about 100 muons/s. RF background: yet another problem. RF cavities produce electron due to field emission converted to x-rays in absorbers
E N D
RF backgrounds on TOF1/2 M. Bonesini INFN Milano Bicocca M. Bonesini - CM19 RAL 7/10/2007
MICE setup: cooling + diagnostics Cools and measures about 100 muons/s M. Bonesini - CM19 RAL 7/10/2007
RF background: yet another problem • RF cavities produce electron due to field emission • converted to x-rays in absorbers • causing backgrounds in trackers and TOF stations • in phase with muons we want (peak at RF crest) • Emission rate rises very steeply with electric field and magnetic field (1.5-2.5 t at MICE cavity location) • test problem with MTA setup at FNAL • rates: ~26KHz/cm2 for 8 MV/m at B=0 at 4.5 m f rom RF cavity, with energy deposit ~ 400-600 KeV (for a MIP ~5 MeV) Fiber tracker M. Bonesini - CM19 RAL 7/10/2007
From BTF testbeam ADC spectrum in logarithmic scale Selection of single electron events Part of the same spectrum in linear scale Here we will have backgrounds signal: problem is to estimate rate M. Bonesini - CM19 RAL 7/10/2007
Back of the envelope calculation (CRAY MP inside) • Use Rykard MC estimation for tracker (MICE note): e- 4.4 KHz, g 1.8 MHz • But TOF1 or TOF2 is further downstream and thus rate/counter will be probably reduced • I guess with a suitable pedestal cut we will have no problems, but well a G4MICE simulation ( see Rykard note # 90) may be useful • MIP signal ~300-400 mV, this background is 15 times less in energy, so a -40 mV cut on LE discriminator may be enough M. Bonesini - CM19 RAL 7/10/2007