[b1_ana] Follow up on Re: Fwd: Re: A_PV with Deuteron Target

[O. A. Rondon]

One more thought: since the plan is to use the Hall B coils, the option
of suppressing A_V^d by aligning the field along q is very restricted.

I don't know very well the geometry of those coils, but I found a hand
sketch on the JLab Target Group pages (there must be something more
professional somewhere). From the numbers there I get that the coils
could be rotated to a maximum theta_q < ~ arctan(8/(19+4) = 19 deg,
keeping a 1 cm upstream clearance for the slow raster's 1.1 cm radius
envelope.

Given the uncertainties in surveys, and beam wandering, especially with
a chicane (needed to correct the beam deflection for rotated coils,) 1
cm is the minimum clearance I would advocate.

The dimension along the beam to the target center 19cm + 4 cm comes from
taking 1/2 the coils' 8 cm split, per NIM paper on the CLAS target. If
one sticks to the numbers on the sketch, the target center is at 19cm +
9cm (per note on the right), so theta_q < 15.9 deg.

The above consideration indicates that it's most likely that my 19 deg.
estimate is way over optimistic, and since our two high x points have
theta_q > 19 deg., trying to align the field along q to suppress the
target-only A_V^d does not compensate for the trouble of setting up the
beam line.

The rough sketch of the Hall B coil dimensions is here
https://userweb.jlab.org/~ckeith/EG1/Autopsy/banjo_dim.jpg

Again, I encourage everyone to review the above points carefully.

Cheers,

Oscar





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Subject: [b1_ana] Follow up on  Re: Fwd: Re: A_PV with Deuteron Target
Date: Sun, 19 May 2013 19:03:20 -0400
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