RE: beamline specs on wiki

Dear Richard,

Thanks very much for your prompt answer. I agree with you that the energy resolution for the fixed array is good enough for us.

Best regards,

Liping

From: Richard Jones [mailto:richard.t.jones@uconn.edu]
Sent: Wednesday, October 08, 2008 12:44 PM
To: Gan, Liping
Cc: Hall D beam working group
Subject: Re: beamline specs on wiki

Dear Liping,

In our current tagger design, there are two possible ways for you to get what you need.

used the fixed array -- full coverage in the range 9.0-11.7 with 190 counters subtending 30 MeV each.
move the microscope down to the endpoint region of the focal plane and tag a range of only 150-200 MeV with 100 channels of 2 MeV width each.

The microscope is designed primarily for operation at lower photon energies, where the counter widths per MeV are a lot lower. Moving it to the endpoint allows running at the highest possible rates, but with very fine energy channels only 2 MeV wide, and a narrow tagging range of 150-200 MeV, depending on where in your range 11 - 11.7 GeV it is placed. I believe that is overkill for your needs.

You should look carefully at the fixed array. A full width of each energy bin of 30 MeV translates into a rms energy resolution of 13 MeV = 1.1e-3 of E0. That is very close to your stated requirement.

Richard Jones

Gan, Liping wrote:

Dear Richard,

According to the current beamline specification, the energy resolution

in the range of 9-11.7 Gev is 20 MeV, which is about 2x10^-3. Is it

possible to improve the resolution to 1x10^-3 in the high energy end,

see from 11-11.7 GeV? It would be great help for Primakoff experiment

because its cross section has strong energy dependence. I would

appreciate very much to hear from you as soon as possible.

Best regards,

Liping