Log entry time 14:28:02 on March 29, 2010

Entry number 314497

Following up on last night's optics study, and per discussions
with Paul Souder and John LeRose, here is a suggested run plan
for more optics studies.  When this is performed is up to the RC.

Notation

Tune A == what we started expt with (sometimes called "old" tune)

Tune B == what we tried yesterday (was "new" tune).  [I don't like
"old" and "new".  Future tunes will be C,D,...]

But first, let me elucidate the issues:

(i). For good systematic errors, we need the acceptance defined 
by the collimator, not Q1.  We also need symmetry L/R and up/down.
For the elastic peak, nothing downstream of Q1 should affect 
the acceptance, for either tune.  For tune A it's speculated
that Q1 chops the acceptance, while for B it does not.

(ii). With tune B new holes appeared at top and bottom (good), but 
there are still 2 holes missing at smaller scatt. angle --> 
potentially the septum is not optimal.

Here is the suggested plan:

P0 = 1.063 and all runs repeated for tune A and B.

1. For 2% steps over a range of +/- 20 %  in Q1, measure 
the rates with sieve out.

10 nA (atten = 75, slit = 15) and turn on upper scint HV
to measure the trigger T5 rate.  Should be <= 100 kHz, or
else it may have electronic deadtime.  Speculation is that
tune A will vary but tune B will be rather flat.

2. For septum from 600 A to 800 A in 10A steps, look at the
sieve slit pattern and observe what happens to the holes.
The analysis should focus on getting sharp pictures on the
small-angle holes.

a) Do more holes appear at smaller angle ?

b) Do holes appear and disappear on L,R at the same septum current ?
If so, the apparatus is L,R symmetric.  If not, we may consider 
(later) making a shunt to make the two septum magnets different;
hopefully not necessary.