Well,
running with the CC in the een trigger, as suggested friday, cut the
deadtime by a factor of 2, as can be seen in the first attachment
(red/green point vs black). Nothing changed on the ep trigger so the CC
efficiency can be determined from there. The new file trigger is called
tb.settings - for the time being. It also fixes a minor bug.
So presently, we can run < 20 % up to 80 mA (true singles - with CC - are
effectively prescaled by 15). On friday I was quite convinced that the
"breaking point" in the deadtime vs beam distribution somehow had to do
with beam tune and beam blow up, although I could never find evidence in
the lifetime for that.
Then 2nd attach: livetime vs accepted rate. As predicted by Karen and
discussed in the hall-B NIM paper at about 400 Hz we max out on bandwith.
The solution - for the higher currents - is to go to fast ethernet, which
requires additional fastbus modules. In the meantime we can reduce the
event sizeby running the ADC thresholds
However, it is also true that 2/3 of the events are trackless, and a vast
majority of those that track are low-energy "junk" and that this is
attributed to the collimator. In my opinion this is the most important
item. Also because at this rate sooner than later we are going to fill up
our disks with useless junk.
-- ________________________________________________________________________________ Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124 research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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