User name GB
Log entry time 11:30:58 on November 21,2002
Entry number 51959
This entry is a followup to: 8359
keyword=Beam hits target cell when moved in Y directionI was studying the stability of the tof cuts with beam steering, using the Benoit' script.
I observed huge counting rates of the inelastic protons when the beam is shifted 3mm in Y direction (figure 1 : run 14399, octant 2) compared to the ToF spectra when the beam is centered (figure 2 : run 14384, octant 2).
This phenomenon is observed only when the beam is shifted in Y direction (the same behaviours also exists when dY=-2.3). It seems that the beam hits the target cell somewhere when it is not centered. That also could explain the trip of HV when the beam was moved 2mm in Y direction (see elog 8359).
It is important to notice that the increase of the counting rates associated to the inelastic protons is greater in small detectors than in great detectors. The simulation underestimates the rates of inelastic protons even when the beam is centered. The ratio between rates of inelastic protons extracted from the measurement and from the simulation is also greater in small detectors (a factor of 6) than in great detectors (a factor of 2).
The simulation doesn't take into account the interaction of the beam with the entrance and exit windows of the target cell. Thus, the main part of the inelastic protons rates could be produced in these windows. Let's wait the results of the empty target measurement.
FIGURE 1
FIGURE 2
