Cherenkov Gas project calculations (fwd from Polyansky)

[Elton Smith <elton@jlab.org>]

HI All,

I will forward a few background e-mails which can be used for further
discussion.

Cheers, Elton.

---------- Forwarded message ----------
Date: Thu, 1 Feb 2007 13:22:34 +0300 (MSK)
From: Valery Polyansky <poly@x4u.lebedev.ru>
To: Elton Smith <elton@jlab.org>
Subject: Cherenkov Gas project calculations

      Dear Professor Smith,
thank you for the information in the last letter.

 Briefly about the current status of work on the Gas Cerenkov project.

 By present time the GEANT basis program
for simulating of the generating Cherenkov radiation and
the light collection from relativistic
particles in the gas-filled Cherenkov detector is created.

 This one program code  include simulating of the relativistic
particles and radiations propagation through substance
with taking Moliere scattering, energy loss and others
elementary process into account. Moreover, the transport
of particles include the correction  of the tracks in the magnetic
field for the given GlueX configuration.

 The Cherenkov radiation generating process  is simulated
according to the energy, impulse vector of particle and the medium
refractive index (which also depend on the wave length!).

 The transport of Cherenko's photons  through transparent media
the refractive index depend on wave length. The reflection/refraction
and absorption processes according to input angles, wave length on
the boundary including. Especially, at the simulating of the PMT input
window crossing -  taking the dependence of the quantum efficiency
(or the registration possibility)  from the input angle, wave length
and cross-point position into account.

 We carry out calculations taking   the described GlueX configuration
(distribution of substance  and a magnetic field) into account.

 Next, the radiator material for the gas-filled Cherenkov detector
must be with the high refractive index and simultaneously
small density  and Z. Ours operational choice - C4F10 (n=1.00153) at
atmospheric pressure.

 We consider some variants of the light collection
systems on a basis ellipsoidal and others mirrors shape with
single or two reflecting elements. The mirrors elements are assumed
on carbon-base composite with Al reflecting layer and the
MgF2 protective film.

 The light collection system will be segmented , from 10  to 16 sections
are assumed. This number will be optimized.

 As photodetectors some types PMT are considered. The main traits of
this device for given detector -  the multialkali photocathode,
the quartz or UV glass of the input windows,
the rise time value about several ns and an opportunity of work
in high magnetic fields with/without the outside passive protective
shield. And  the maximum diameter for the input window is assumed.

 Real time for completion of the calculations, design works, to produce
of the documentation on the"Conceptual design project repor"-level
and to make an appraisal of the project  in our opinion - the middle
of March - the beginning of April.

 At the same time, it is reasonable to specify status of works in
the beginning of March.

What do you think about it?

Best regards,
Valeri Polianski
Lebedev group, Russia, Moscow

PS
Word-file with some figures and comments is attached to this letter.

Some pictures and comments