Hi,
Genya said most of it in his shift summary. Run plan is at the end of
this message.
***
The behavior of the cell temperature remains not understood. While the
sensor of the heater behaves reliably (it goes up when heated and cools
down at an expected rate, and it increases only a few degrees with beam
on) the cell frame sensors indicate a much higher heat flow than expected
(from the temperature drop-off rate when the beam is turned off).
It appears possible that the sensors themselves gets hot (and not the
frame). It is therefore planned to run a test at 200mA to see if any
outgassing is invoked.
Genya pointed out the suspicion that the cell temperature has never
increased significantly above 100K. That is what the sensor sitting
directly on the cell indicates also with beam on. The other two sensors
are sitting on the frame. The suspicion is that the wires that lead to
those sensors catch up RF power from the vicinity of the beam axis near
the collimator. We might therefore not need to open the target.
***
On Wednesday after the snake filling we changed the direction of the
holding field from 32 to 45 degrees (by lowering the amplitude of the
longitudinal field to 50%. The polarization has been considerably lower
since, both hPz and Pzz decreased to about 60% of the level obtained for
32 degrees. It is desirable to check wether the polarization decrease is
related to the change of the spin angle (or field amplitude).
We have thus changed the angle back to 32 degrees, see below.
***
Today at Bates, we held a meeting about a possible ion polarimeter
measurement. Before major efforts are started to prepare this measurement,
two essential features are to be tested.
1) Check if the polarization remains the same at lower amplitude of the
holding field.
2) Check if ed elastic events can be properly identified for zero BLAST
field.
***
Run plan for the weekend:
Understanding the polarization issue has the highest priority besides the
planned tests for the ion polarimeter measurement.
-Measure polarized Deuterium at a spin agle of 32 degrees, 250k events per
run and keep RUNLIST-D2.4 and pol.log uptodate. Keep up with the
autocruncher.
-As soon as available, evaluate Pzz and hPz with the standard scripts.
For Pzz:
> cd ~/pro2004/macros/Deuterium/edel;
> root ed_xs.C ####-#### spinthd=32 closed
For hPz:
> cd ~/pro2004/macros/Deuterium/DEEPLIB;
> root -l show_deep_asym_all.C ####-#### closed
-If by Sunday morning the polarization turns out to be still low, the
upcoming procedures need to be discussed on Monday. We then should have
CCR (Larry Longcoy on Sunday 8-16) tune the beam with BLAST field off,
until reasonably low BQM and Wch rates should be obtained. Take 8 hours
of ABS D2 data with BLAST field off. Goal is to see wether ed elastic
events are identifiable.
-If the polarization is high, just continue ABS D2 data taking at 32
degrees until Monday. The zero-field test could be done during nozzle
warm-up on Monday night using unpolarized Deuterium.
Regards,
Michael
--+-------------------------------------+--------------------------+ | Office: | Home: | |-------------------------------------|--------------------------| | Dr. Michael Kohl | Michael Kohl | | Laboratory for Nuclear Science | 5 Ibbetson Street | | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 | | Middleton, MA 01949 | U.S.A. | | U.S.A. | | | - - - - - - - - - - - - | - - - - - - - - -| | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de | | Work: +1-617-253-9207 | Home: +1-617-629-3147 | | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 | | http://blast.lns.mit.edu | | +-------------------------------------+--------------------------+
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