[Halld-pid] TOF resolution

[Elton Smith]

Hi Paul and Alexander,

I was thinking about the discussion at the collaboration meeting of 
increasing the width of the scintillators to accommodate the magnetic 
shielding. Given that the resolutions that have been achieved are on the 
order of 120 ps and our goal is 80 ps, I think we should actually be 
considering reducing the width to increase the number of photoelectrons 
collected. From the the light guide design that is proposed, any 
increase of the scintillator width beyond about 5 cm will start loosing 
light (and in fact also become less uniform in collection). So you might 
want to think carefully about the alternative of having a staggered 
configuration with sufficient overlap to avoid inefficiencies. This will 
increase the number of channels somewhat, but also reduce the rate per 
paddle, especially near the beam hole, where Sasha indicates the rates 
are perhaps too high already. He was suggesting reducing the width by a 
factor of 2 here, but I don't recall the numbers.

Cheers, Elton.


Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite #16
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax