From eggs@fnal.gov Mon Jul  1 22:38:56 2002
Date: Mon, 01 Jul 2002 16:47:49 -0500
From: Elizabeth Gallas <eggs@fnal.gov>
Subject: forward dimuon rates

Commissioners,

The store arrived today with a high rate of antiproton halo,  which caused the 
forward dimuon rates to jump to a rate of 50-100Hz at 6E30.  Two triggers with L1 
di-muon condition:
	mu2ptxbtxx_fz 
	mu2ptxatxx_fz 
had to be prescaled under those conditions.  The pbar halo rate was less than the 
beams division alarm rate but we called the MCR to express displeasure (they will 
investigate).

Rob/Jeff/Ken have been monitoring these halo conditions, which have been known to 
produce these effects, i.e., there is nothing wrong with the trigger as it is written.
Of course they are always making improvements, but it is not clear what could be done 
right away.

In the short term, the only thing I can suggest is that when a run is started, the DAQ 
shifter could reset the prescale on those triggers to 1 if the rate is less than 10 Hz.
At current luminosities, if the and/or rate is greater than 10Hz, the prescale should be 
set equal to the rate.

I don't think the pattern is established enough to speculate on the long term.

thanks,
Elizabeth