In the present design of the CTB and TOF, the scintillators will be read by photo-multipliers. However the following considerations would be also valid if other devices, like photo-diodes, were to be used.
A fast relative calibration can be obtained by comparing the amplitude distributions in each counter. In the present design the counters have equal coverage in the polar angle, . However their coverage in rapidity changes along the axis parallel to the beam. Since the particle density is constant in rapidity, the distributions have to be corrected for their different acceptance before comparing counters. An additional correction due to the different trajectory length of particles inside the scintillator is also needed. The simplicity of the procedure, once the correction factors are known, allows its implementation in the on-line environment.
An absolute calibration, establishing the number of particles traversing a counter from the signal provided by the pm, needs the TPC information. This can be achieved by extrapolating the tracks reconstructed in the TPC to the CTB/TOF and comparing their number with the produced signal. Since this procedure requires track information, it is only possible off-line.