Doug made mention of examining a possible hybrid approach for the WFD
over/undershoot problem until a final solution is reached.
In this spirit, what about decreasing the DELAY TIME in the WFD STOP MASTER
as a temporary "fix"? Currenly it is set at ~1 millisecond, a number that was
defined based on the TOF of the slowest particle (in all geometries) we'd like
to record together with some catalysis arguments. Given that the WFD hardware
*as is* now records *everything* up to ~100 microseconds we may trivially
change the camac lists that control the wait time of the stop master so that
to match it.
This will recover *full* efficiency for *any* particle with beta>~10^-3.
For particles slower than that, the entry face waveform is *guaranteed*
to be recorded. Recording the particle's exit face waveform (plus any
possible additional one) will depend on the particle's pathlength inside
the detector. Over most of the <10^-3 beta region there will still be
significant solid angle over which all hit detector faces will be recorded.
For example, for beta~3x10^-4 all pathlengths up to 9m will have all of
the waveforms recorded. For longer pathlengths, two (entry + ~CENTER) or one
(entry) faces will be there... Throughout this temporary scheme it will be very
simple to calculate efficiencies/acceptances and easy to explain why for
a monopole you recorded over this period you have only its entry waveform
only (if). The 100usec window still allows some searches with catalysis in
mind.
The acceptance in this configuration may be further improved by increasing
the WFD data byte limit (if I recall well though, Ed mentioned that this is
already at its limit). Another thing that will help in this direction is
to clock down the WFDs by some factor that will not harm our ability to
distinguish s.p.e.'s. We can perform a type of Sophia's sensitivity
measurement done back in Feb96 with some clocked down WFD channels and see
how this is affected. We'll gain as much as we can afford in this way since
the available digitizing window will be increased inversely prop. to the
frequency. However, any precision TOF measurement for fast particles will
be harmed...
--Erik