If we are to get the 3% statistics originally proposed, these times need
to multiplied by (5/3)**2 = 2.78, yielding 6.4 and 4.2 days, respectively.
If we are to get 60 energy bins instead of 30, we need another factor of
two. Clearly this is beyond our hope. [The original request was for 48
bins.]
These times correspond to a tagged-photon rate of 5*10**6 sec-1. If this
can be pushed higher, no one will be happier than I (except Catalina).
Exploring this possibility is a crucial feature of the Tagger
commissioning run.
If we factor in a beam-on-target factor of 50%, we need another factor of
two. Recent experience has been much worse. We hope for the best here.
There will be a certain amount of overhead time for changing beam energy
(once) and for tagger-efficiency runs (1 hr every 12 hours, say). This
probably amounts to another day or so in total.
Clearly we have no time to waste. Equally clearly, the Tagger must be
commissioned and calibrated at BOTH 1.6 and 4.0 GeV before we begin.
Thanks for your understanding and help with all of the above.
See you Tuesday at the g5 meeting (2pm in room L207).
Best regards, Barry
Barry L. Berman
Professor and Chair
Department of Physics
The George Washington University
Corcoran Hall, Suite 208
725 21st Street NW
Washington, DC 20052
Telephone: (202) 994-7192
Secretary: (202) 994-6276
Fax: (202) 994-3001
>>> Please note: My new E-mail address is berman@gwis2.circ.gwu.edu <<<
On Wed, 13 Aug 1997, Arne P. Freyberger wrote:
>
> barry,
>
> > Since I am the Run Coordinator for expt g5, I would appreciate being
> >put on your email distribution list.
>
> You have to put yourself on the "clas_photon" mailing list.
> To subscribe point your browser to:
>
> http://www.cebaf.gov/ccc/hypermail_archives/How_to_Subscribe.html
>
> for instructions. The name of this group is "clas_photon"
>
> >We requested (via Dan Sober) that we begin with 1.6 GeV, then go to 4 GeV
> >on August 24, and back to 1.6 GeV on September 2. Is there any reason
> >this is not advisable?
>
> The fewer changes in beam energy the better off we will be..
> that is: the least amount of time that will be spent re-establishing
> a quality tune. Also remember that in June the accelerator was NOT
> able to establish a 1.6 Gev beam to hall B.
>
> I would strongly recommend that we:
>
> A) start out next week at 4 Gev
> B) finish commissioning at 4 Gev
> C) hand over operations to g5
> D) g5 completes the 4 Gev part of their run
> E) establish 1.6 Gev beam
> F) determine tagging efficiency for 1.6 Gev primary beam
> G) complete g5
>
> Any request for energy change could easily result in 8 hours of
> down time for the retune of the line.
>
> It would help if I/we had an idea of how much beam time you
> need at 4 Gev and 1.6 Gev.
>
> I hope this helps...
>
> Arne
>