User name sawatzky
Log entry time 22:43:25 on February 20, 2006
Entry number 162977
Followups:
keyword=Trigger coincidence timing using pulser 'faked physics'The fake coincidence was established by fanning out two copies of the trigger. One copy was then delayed relative to the other by an amount corresponding to the physics delay between an electron in BB and a neutron in BH.
There are three delay settings (different length delay cables) that set the relative timing to match the timing of the three GeN kinematic settings.
There is a corresponding set of three delay cables that adjust the timing of the AND gate that generates coincidence triggers (T3s) such that the coincident peak stays centered with the timing acceptance.
The coincidence timing is measured by two TDCs.
The first is the low-resolution (0.5 ns/ch) 1877 in common-stop mode that also flags the event type (inputs 0-7 correspond to the T1-T8 trigger inputs). That histogram is titled "D.bit3".
The coincidence time between the arms is also measured by a high-res 1875 common-start TDC (0.05 ns/ch). That histogram is titled "D.ctimebb".
The spike on the left edge of the D.bit3 histos is the self-timing that occures when the n-arm random trigger walks into the coinc. window in the common stop 1877. The same thing happens on the right edge of the D.ctimebb histo for the common-start 1875.
In order, the figures below show the coinc. timing for
Kinematics 3, Q2 = 3.4 (GeV/c)^2
Kinematics 2, Q2 = 2.4 (GeV/c)^2
Kinematics 1, Q2 = 1.3 (GeV/c)^2
The timing was left set up for the 1.3 (GeV/c)^2 kinematics.
A copy of this log entry has been emailed to: rom@jlab.org, saw@jlab.org
Kin3 - fake coinc. plus randoms (run 1889)
Kin2 - fake coinc. plus randoms (run 1891)
Kin1 - fake coinc. plus randoms (run 1892)
