Email from Roger:

From carlini@jlab.org Thu Sep 23 10:50:44 2004
Date: Sun, 19 Sep 2004 14:55:50 -0400
From: Roger Carlini 
To: Jim Birchall 
Cc: Juliette Mammei , Klaus Grimm ,
     Mark Pitt , Neven Simicevic ,
     Greg Smith , Allena Opper ,
     Tony Forest , Norman Morgan ,
     Mike Finn , David Armstrong ,
     Yongguang Liang , Shelley Page ,
     Dave Mack , Richard Jones 
Subject: Re: Inelastic rates on the Cerenkov bar

Hi Jim:

If the increased inelastics in the 8-9-22 design are due at least in part to the need for a wider bar to cover the tips 
of the moustache then I suggest clipping the upper corners of the 9-8-22 collimator at the largest phi edges. This might 
decrease the width requirement (and inelastic %) without hurting the FOM much. Just a thought.

Best Regards

Roger

Jim Birchall wrote:
> Here are the rates I find on the Cerenkov bar from inelastics (REAC = 3 
> only, ep --> en pi+) as a function of cut across the width of the bar 
> with mini-torus field off for the 10-8-22, 9-8-22 and the standard 
> 8-8-22 Boston type collimators. There is no cut on the energy of the 
> electron, just on the bar width.
> 
> 10-8-22 collimator (maximum angle 14.5 degrees)
> Cut on x (cm)   Elastic rate (MHz)  Inelastic rate (MHz) Percent inelastic
> 300-320  785   4.5  0.57%
> 300-318  771   2.4  0.31%
> 300-316  750   1.2  0.16%
> 
> The maximum angle let through by the 10-8-22 collimator is about 14.5 
> degrees, which extends the upper edge of the moustache compared with the 
> standard 8-8-22 Boston collimator (maximum angle 11.5 degrees).
> 
> 9-8-22 collimator (maximum angle 13 degrees):
> Cut on x (cm)   Elastic rate (MHz)  Inelastic rate (MHz) Percent inelastic
> 300-320  730  1.50  0.21%
> 300-318  717  0.64  0.09%
> 300-316  702  0.22  0.03%
> 
> The standard 8-8-22 Boston collimator, maximum angle 11.5 degrees:
> Cut on x (cm)   Elastic rate (MHz)  Inelastic rate (MHz) Percent inelastic
> 300-320  624  0.19  0.030%
> 300-318  618  0.07  0.011%
> 300-316  609  0.03  0.005%
> 
> So, for the standard Boston collimator, the inelastic rate on the bar is 
> up to 200 kHz, 0.03% of the elastics, depending on bar width. For 
> 9-8-22, the inelastic rate is up to 0.2%, for 10-8-22, up to about 1/2%.
> 
> Jim
>