Hi,
I get same results this time. unpol feeds 2.2e16 atoms/sec, I get
rates of 0.66/C. ABS on a GOOD day gives same yield, on not so good
condition, yields a bit lower, but I looked at yields day by day,
ussually before it drops by more than 10%, we regenerate the nozzel
and/or pumps. It is nice to resolve this thing for good.
I get lower efficiency of 60% though, but I believe this is just due to
tighter cuts in my analysis. resolutions come into play as Genya pointed
out. I hope we can start to use some new claibration that improve
resolution very soon(in BLAST time ofcourse :) .
I also would like to report a strange thing that valve status are not
registered correctly in DST. It looks like that only when valve status is
changed, will the data be read into coda stream. When a valve is flipped
from open to close, correct valve status will be recorded into DST but
only TILL THE END OF RUN. the next run will have all valve status reading
0 again. I say this is strange because I was under the impression that all
epics channels are forced to be read once at GO time.
This caused some confusion about V14 status in some older unpol runs.
Anyhow, I think the easiest cure if for the shift person to write down V14
status in RUNLIST, in elog, and in RUN sheets.
Cheers.
Chi
On Thu, 9 Sep 2004, Genya wrote:
> Due to a unpol D2 run we took this week, I was able to recalibrate
> our luminosity
> again using fixed crunching (bugs discovered couple of weeks ago).
> Finally, for the
> first time with a long cell the data shows consistency.
> Th ABS data were taken from a "good day", when target was well
> conditioned after
> the nozzle refreezing. The elastic eD event rate is about the same for
> ABS and unpol with
> V14 open and buffer pressure 2.0 torr. Assuming we trust unpol, it gives
> ABS flux of
> F=2.2* 10**16 at/sec.
> Comparing the ABS rate with theoretical curve, I got F=1.5*10**16
> at/sec. The remainig
> 30% difference is apparently the real inefficiency of
> detection/reconstruction. So we may assume
> that F=2.2*10**16, target thickness is 6*10**13 at/cm**2 with detection
> efficiency of 70%.
> I'd like to add that this efficiency is related to relatively low q
> (Theta (e) is around 30 degrees).
> At higher q the identification might be a good deal worse, and the issue
> of momentum and
> angular resolution remains crutial.
> Genya
>
>
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