[PEPPo] Nearly Final Version of the Proposal

[hyde at jlab.org]

A few quick comments on version 7.
Most of my previous comments on section 4.2.2 of version 5
have not been addressed.

I include them below.

Most glaringly,
Fig. 14 caption says
"Positron Collection efficiency for $10^6$ electrons,
but the vertical axis says
dN/dE 10^8 e-.
That is a factor of 100 discrepency.
Also, the vertical axis label is inconsistent with the scale.
The vertical scale has a factor x10^-6.
This implies that the vertical axis is positrons per electron.
If it were positrons per 10^8   electrons, the vertical scale
should be 0 to 100 as in Fig. 13.

Sincerely,
Charles Hyde



Previous comments:

Section 4.2.2
p. 24, after fig. 12
correct "on In fig. 13" and rephrase, as follows:
"The corresponding positron collection efficiency at the
end of the S1 solenoid, for collimator apertures
(just after the production target) of 2, 4, and 6 mm are
shown in Fig. 13."

p.25, the discussion of Fig. 13 and 14 is confusing.
Fig. 14 compares collection efficiency for the S1 entrance
at 10 or 50 mm from the target.  But on the previous page,
it was stated that S1 would be 120 mm from the target.
Is it mechanically feasible to have the solenoid as close as
10 mm? (or even 50 mm?)  What distance was used for Fig. 13.
Fig. 14 says 10^6 electrons.  Fig. 13 says 10^8 positrons.
If this is correct,then 50 mm increases the positron efficiency
by a factor of 200 over 120 mm (910/10^6 vs 409/10^8)
Please clarify.

Fig. 15
[ is x' =dx/dz = tan(theta_x) or is the vertical
axis $\atan(x')$?  The axis says degrees in illegible font,
but the values of 10 deg seem inconsistent with Fig. 16)
Suggested clarification of the caption:
"Positron phase space distributions $x'$ {\em vs.} $x$ (left)
and $y'$ {\em vs.} $y$ (left) at the exit of S1 (top) and
S2 (bottom).  The angles are expressed in degrees
($\atan(x')$ and ($\atan(y')$.
I don't understand  the sentence
"While the angular distribution spans up to 90 deg,
only a very small fraction of it will be detected by the
polarimeter..."
Firstly, is this referring to fig 16 only or Figs 15 and 16?
The positron production efficiency is irrelevant here.
What is relevant, is what fraction of this positron phase space
can be converted into useful photons for the polarimeter.
I think this sentence should be deleted, and replace with a phrase, "The
useful phase space for the positron polarimeter will
be discussed in section 5.

Fig 16 caption
We don't need the possesive 's'
"Positron Phase Space at Reconversion target T2".

Section 4.2.3
I think the background study and the discussion of the Compton asymmetry
belong in separate sections.
In particular, move the asymmetry to section 5.
Without the discussion of section 5, I totally do not understand
what it means to have a crystal dependent analysing power.
Fig. 18 needs to be moved to section 5, and needs much
more discussion, since this is the statistical precision of the
entire experiment.



 > Folks:  attached please find a version of the proposal that includes all
> changes I have received as of noon today, and the response of the
> writers to comments you sent.  As we are nearing the very end, I will
> not post the Latex sub-files this time - only the full proposal file
> (and all the figures).  The relevant files are posted at
> http://www.jlab.org/~cardman/ in the Prop-e+28JUN11/ directory. The
> proposal and final edits to it will be discussed during tomorrow's
> teleconference, slated to start at 10:30 AM.  If you have specific
> changes to suggest, please refer to the page and line numbers of the pdf
> file attached, and, ideally, provide suggested changes.  We MUST
> converge by Thursday evening as the proposal must be submitted by Friday.
>
>
>                            Larry
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