[Halld-tagger] Field mapping diagram and fringe field

[Timothy Whitlatch]

Hi Dan, 

We generally cover 30CM BR and downstream of the poles. It looks like we cover what you ask for. We can do hand measurements at the focal plane. 


Tim Whitlatch 
Hall D Engineer 
Jefferson Lab 
12050 Jefferson Ave ste 402 
Newport News, Va 23606 
757-269-5087 

----- Original Message -----

From: "Daniel Sober" <sober@ cua . edu > 
To: "Hall D beam working group" <halld-tagger@ jlab .org>, "Timothy Whitlatch " <whitey@ jlab .org> 
Sent: Monday, October 7, 2013 5:03:10 PM 
Subject: Field mapping diagram and fringe field 

Dear Tim et al ., 
Here's an updated version of the map request in the form of a diagram in mapper coordinates. I think it reflects most of what you reported earlier. 
The main thing I would like to add is to assure that we make some provision for measuring the fringe field at the exit flange , which is about 6 cm from the nominal focal plane. This field will be of order 10 gauss , and only a crude hand measurement is needed, but it may be important in adding another significant figure to the energy calibration. We also need to know whether the magnetic shielding planned for the fixed-array PMTs in this region is adequate. 
If you have not made other arrangements for measuring this fringe field, I would propose marking off distances along the exit flange and making a measurement with a hand-held gaussmeter at intervals of about 50 cm. The origin of coordinates could be referred to the magnet yoke. 
Dan 

-- 
Daniel Sober 
Professor 
Physics Department 
The Catholic University of America 
Washington, DC 20064 
Phone: (202) 319-5856, -5315 
E-mail: sober@ cua . edu 

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