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    User name Olivier, Peter

    Log entry time 18:06:38 on January25,2005

    Entry number 140023

    Followups:

    keyword=Pulser timing test

    We did a pulser test to check the timing for the deuterium target setup (same as for carbon).

    Timing for real particle:
    L - electron - beta=1 : tof=90ns
    R - 1.45 GeV/c proton - beta=0.83 : tof=107ns
    ND- 300 MeV/c neutron - beta=0.3 : tof=66ns

    So I send a 1024Hz pulser into L, R and ND, using cables that more or less reflect the relative timing of the 3 particles. I remeasured the length of these cables using a battery pulser and a scope;

    L - 297ns
    R - 325ns
    ND- 220ns

    Note: for the L and R cables, there is a trick in this relative timing. For a real particle, the cabling and electronics between PMT and trigger formation is 61ns. For the pulser signal it is 18ns. So there is a relative 43ns to account for when comparing with the ND (also the relative L-R is unchanged, since this trick is for both arms). On the neutron arm, the pulser is sent to the patch pannel, not the PM. So there is a 12ns to account for when comparing L-R.

    Given all that, the raw data shows that when the pulser is sent into ND-P1-L (TDC start with this pulser, stop with the T5 formed by the same pulser, simulating the triple coincidence setup), the TDC peak is at channel 777 (which is consistent with our scope observation if these signals; we also checked that the ADC signal shows up 100ns into the 200ns gate).

    This test is not fully analyzed yet, all these relative delays are not taken into account. I will sit down quietly and figure out where the peak is expected for real particles, and post a followup entry. However, the test shows that for the actual triple coincidence to be missed in time, the test must be wrong by more than 350ns, which I think is impossible. So the peak is here, hiding in the data...