[b1_ana] Fwd: TAC Report for PR12-13-011

[Oscar Rondon-Aramayo]

Hi,

Basically, on the dilution item, they are saying that the target length
could change from the pol. half-period to the unpol. half-period, so they 
wouldn't cancel in our  eq. (26).

Of course, if we use targets of known geometry, that change would be totally
negligible. But for fragments we can estimate the change due to one fragment
that *might* fall out of the slow raster area during one period.

Since the average fragment is about 0.008 cm^3 (2 mm on the side) and the
raster volume, for p.f. = 0.6, is pi*1.1^2 cm^2*3 cm*0.6 = 6.8 cm^3 the 
change would be 1 part in ~ 850.

During SANE, there was one instance in about 500 h of beam time, of sudden 
polarization increase (about 8% absolute in under 1-2 min), which could be 
attributed to fragment loss/rearrangement about the NMR coil. Nothing was 
seen during RSS (about 250 beam hours). The jumps seen at SLAC happened with 
the SLAC beam of 20 muA per 4 mu s pulses at 120 Hz, not CW beam.

So I would estimate a less than 20h/500h*1/850 ~ 5E-4 change per period.

The data taking sequence:
- unpol. top target
- pol. top target
- unpol. bottom target
- pol. bottom target
- anneal

for the first cycle would optimize the low temperature irradiation to build 
up the ND3 polarization. The unpol. data could be taken at 150 nA to speed 
up the dose build up.

For the later cycles, it would be best to take pol. data first, so the 
initial dose is lowest. Dumping the LHe in the nose does not change the 
dilution factor (all data are taken with LHe), and it's extremely unlikely 
it would cause any material loss. But this could be studied during the run, 
by comparing yields for the same cup from one period to the next.

Research on making known geometry material would be most valuable.

Third arm luminosity monitors would need to do a better job than watching
the yields, with acceptance and raster cuts, of the data itself.

The other change, due to the acceptance dependence of beam position could be
tricky, although at forward angles and with longitudinal target field, it
should be easier to control. The problem is that the beam offsets affect the
reconstruction of kinematic quantities with software spectrometers such as 
the
HMS.

Cheers,

Oscar


On Tue, 28 May 2013 23:10:24 -0400
  Karl Slifer <karl.slifer at unh.edu> wrote:
> ---------- Forwarded message ----------
>From: Stephen Wood <saw at jlab.org>
> Date: Tue, May 28, 2013 at 11:06 PM
> Subject: TAC Report for PR12-13-011
> To: Karl Slifer <slifer at jlab.org>
> 
> 
> Karl:
> 
> Attached please find the TAC report for PR12-13-011.
> 
> This proposal was also reviewed by the the independent Technical review
> committee.  This report should come to you through official channels, but I
> will send you a copy if I can get it.
> 
> Steve