Email from Mike:

From jmichaelfinn@cox.net Thu Sep 23 11:24:13 2004
Date: Sun, 19 Sep 2004 23:42:09 -0400
From: John M. Finn 
Reply-To: finn@physics.wm.edu
To: carlini@jlab.org, '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

        Roger,
        
        This is part of the point that I have been making. You can't allow
the sectors to overlap, and I thought that we had argeed not to. Is it
possible to find out the the largest phi angle cut that doesn't overlap the
sectors at the z location of the Cerenkovs?
        Regards,
        Mike,
        
        
        -----Original Message-----
    From: Roger Carlini [mailto:carlini@jlab.org] 
    Sent: Sunday, September 19, 2004 2:56 PM
    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
        >