[Tpe] TPE field reversing

[Larry Weinstein]

Dear TPEers,

We will need to decide how often to reverse the magnetic fields.  There 
are a few constraints.

   1. we should reverse torus fields weekly during the Tuesday
      maintenance period
   2. we need to remeasure the two beam energy vs position after
      reversing the chicane.  This will take about 4 hours.

We should decide whether to switch the chicane when we switch the torus 
or not.

There are generally two schemes: 1) switch both the torus and the 
chicane weekly, but out of phase or 2) switch the torus weekly and the 
chicane every other week.

Scheme 1: switch torus polarities on Tuesdays (during maintenance 
periods) and switch chicane polarities on Fridays.
Advantages: a) complete set of four field possibilities every two weeks, 
b) reverse Torus fields during down times, c) never change both fields 
together
Disadvantage: must measure beam distributions every week with the 
calorimeter and dense fiber monitor
day
	torus
polarity
	chicane
polarity
1 Tuesday
	+
	+
4 Friday
	+
	-
8 Tuesday
	-
	-
11 Friday
	-
	+
15 Tuesday
	+
	+


Scheme 2: switch torus polarities on Tuesdays (during maintenance 
periods) and switch chicane polarities on alternate Tuesdays (or Fridays).
Advantages:  a) reverse Torus fields during down times, b) measure beam 
distributions every two weeks
Disadvantages: a) complete set of four field possibilities every four 
weeks, b) change both fields on the same day (if done Tuesday)
day
	torus
polarity
	chicane
polarity
1 Tuesday
	+
	+
8
	-
	+
15
	+
	-
22
	-
	-
29
	+
	+
36
	-
	+


The frequency of beam distribution measurements will have an impact on 
calorimeter mounting.

-- 
				Sincerely,
				Larry

-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
weinstein at odu.edu
http://www.lions.odu.edu/~lweinste/

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