RHIC Spin Collaboration Discussion During Run

**04/25/2003**

by B. Fox

\(1\) RHIC Status Report \[Haixin\]

Over the last week, the following was seen/accomplished:

-   overnight Thurs-Friday, the beam was mistakenly filled according to
    the 6x6 fill pattern instead of the 55x55. So, the first 6 bunches
    in each were polarized and all the rest were unpolarized. This was
    caused by a miscommunication with the operator and has been
    resolved.

-   still working on getting the confirmation spin pattern from the
    source measurement into CDEV. The expectation is that this will be
    ready on Monday.

-   the polarization in blue after the energy ramp is consistently above
    30%. The injected polarization is something like 42%. The ramping of
    the spin rotators at PHENIX do not alter the polarization in blue.

-   the polarization in yellow was 33% on Sunday when the injected
    polarzation was 40% or so. This observation demonstrates that the
    use of the damaged snake as a partial snake is going to work.

-   the explanation for the typical significant loss of polarization in
    yellow now has an explanation. During the beta-squeeze potion of the
    ramp, the beta_y tune crosses 0.24. With the partial snake, this
    value is probably too close to the 1/4 resonance. Work will be done
    to limit the tune during the ramp into a more safe region.

What needs to be done to get us into the physics run as soon as
possible?

-   verify the rotation of the spin at PHENIX using the local
    polarimeter.

-   up the luminosity.

-   try to correct the tune on yellow to keep it below 0.24 and thus
    better preserve the polarization.

\(2\) Source Status Report \[Anatoli\]

Over the last week, the following was seen/accomplished:

-   during the Wednesday access, Anatoli found a Na blob in the ionizer
    cell of the source which was cause of the limited intensity. This
    blob was removed.

-   developed and implemented a new scheme for pulsing the rF so that
    the bunch intensity could be high but the average load on the
    replaced 29 GHz tube is not high.

-   after the two changes, the source is delivering 5\*10\^{11} to the
    booster with polarizations of \~75% as measured with the 200 MeV
    polarimeter.

What was discussed....

-   Are we regularly measuring the polarization at the source? \[Gerry\]

> Yes.

-   Is the source polarization (sign) measurement from the Faraday
    polarimeter being archived? Is it available to experiments?
    \[Gerry\]

> It is measured but still not percolated through the system into CDEV.
> Work is underway on this matter and the expectation is that this work
> will done by Monday.
>
> \- What has been done to protect the new (irreplaceable) 29 GHz tube?
> \[Gerry\]

(1) the cooling system now uses N2 instead of air,

(2) new super-duper fileters were installed in the N2 cooling system,

(3) the reverse power to the tube is now interlocked, and

(4) the tube is checked at every access.

\(3\) AGS Status Report \[Thomas\]

Over the last week, the following was seen/accomplished:

-   the injection/ramping in the AGS is now a regular, stable operation

-   typically, the bunch intensity 0.6\*10\^{11} particles and
    polarization is 45% in the AGS at the transfer energy.

What is the thinking for improving on this performance:

-   try to use a faster ramp rate to reduce the polarization loss

-   consider extracting at a lower energy to avoid the final spin
    resonance where the AGS CNI shows about a 10 to 15% polarization
    loss. The issue here is that the gain in polarization may be lost in
    the transfer to RHIC due to the energy difference. Some head
    scratching here will decide if the effort is merited.

-   reduce the emittance further to gain a little bit of polarization
    now that the source is producing more intensity in each bunch.

-   systematic soften the booster collimation to increase the intensity
    injected into the AGS without affecting the polarization.

\(4\) AGS CNI Polarimeter Status Report \[Sandro\]

> Very little to say here since it works fine. They are thinking about
> moving the Si out by 15 cm in two weeks to reduce the radiation
> exposure and maybe they will change the detector at that time.

\(5\) RHIC CNI Polarization Status Report \[Osamu\]

Over the last week, the following was seen/accomplished:

\... on the hardware front,

\* the silicon leakage curretns are now \~1 uA, still small compared to
last year.

\* the energy calibration is stable within a few %.

\* all targets are okay.

\* WFD are working okay.

\... on the software front,

\* the \"simple\" switchover from scaler and event (AT) mode is still
being put together.

\* the QA code for analyzing data in either mode is now available.

\* the polarization analysis software worked just fine over the last
week (except when the spin pattern was screwy).

\... first measurement of the polarization on the ramp in yellow.

> \* there were two measurements done for yellow. In the second one,
> however, the beam was lost early in the ramp due to a beam permit
> being pulled in blue, not the polarimeter target.

\* during the ramp, the beam position wanders a bit and they see a nice
correlation between the beam position monitors and the event rate in the
polarimeter.

\* the polarization looked stable over the ramp, with perhaps a drop at
the start of the ramp. But, it is too early to make any conclusions from
these data.

\* offline work needs to be finished to understand the cuts, especially
for the first and last measurements.

\... on going to production mode,

\* instructing to the operators on how to use the polarimeters.

\* finishing up bunch monitoring tool.

and finally questions which came up \...

\(a\) How often do we measure? \[Gerry\]

The sign is measured with the Faraday polarimeter for every bunch.

\(b\) What about the \"funny\" data seen occasionally by the experiment?
\[Jan\]

> The funny data comes from calibration runs. It was suggested that the
> results from calibration runs not be placed in CDEV. Osamu will
> consider this matter.

\(c\) What, in event mode, will be logged into CDEV? \[Gerry\]

> In event mode, the scaler data is still available. That will be logged
> to CDEV as it was in the past.

\(d\) What about the asymmetry of the background? \[Hal\]

> Hal raised the point that, if there is an asymmetry in the background
> and the background causes deadtime for the CNI measurement, then it is
> possible that the deadtime will be spin-dependent. In this case, there
> is a problem. Osamu was asked to look at the asymmetry in the
> background.
>
> \(e\) Will we be collecting enough data to be able to simulate the
> device if there is a need? \[Hal\]

Yes, in event or \"AT\" mode, we store all of the data. Osamu plans to
operate in this mode as often as possible.

> \(f\) Can the readout of the WFD be setup to store both the yellow and
> blue measurements in the WFD and then readout after both measurements?
> \[Sandro\]
>
> The WFD can store the data from both measurements since its banks are
> deep enough. Sandro raises the question of whether we should consider
> reading out the WFD after both measurements instead of after each
> measurement as is done presently. This change would reduce the
> measurement time from 10 minutes to 1 minutes.

\(6\) Spin Rotator Commissioning Status Report \[Waldo\]

Over the last week, the following was seen/accomplished:

-   ramped up the PHENIX rotators in both rings over a 30 minute period.
    Had to make corrections to accomplish this. Polarization survived.

-   then, ramped up the PHENIX rotators in both rings over a 15 minute
    period. Polarization survived.

-   and then ramped up the PHENIX rotators in both rings over a 7.5
    minute period. Blue polarization survived, but this setup needs more
    work.

What is to planned for the next week?

-   yellow is more problematic than blue due to the spin tune shift
    arising from the use of the damaged snake. Work needs to continue on
    this matter.

-   local polarimeter measurement of the spin orientation at PHENIX with
    the rotators on.

and, then the questions \...

\(a\) What are the plans for the STAR spin rotators?

> STAR wants to run 1 week transverse at the start of physics. The plan
> is to use the lessons from getting the PHENIX rotators up to proceed
> more rapidly getting the STAR ones up.

\(b\) What are the plans to minimize/sync B-field flips at the
experiments?

> Each time an experiment flips it B-field, there is a need to do some
> beam, so such flips cause down time from physics. We should sync the
> B-field flips at the experiments and we should not do it more often
> than absolutely necessary. The best thing would be to sync the B-field
> flip schedule with the tuning of the STAR spin rotators since, in both
> cases, tuning is required.

\(7\) STAR Status Report \[Les\]

What has been seen/accomplished over the last week \...

-   East FPD is ready, just need to tune relative and absolute gains.

-   West FPD readout working following fixes done during the Wednesday
    access.

-   Progress w/STAR scaler system - bunch counting bits now working \--
    and anticipate getting data tonight if beam conditions are good.

What is planned for next ready?

-   TPC/EMC/FTPC/SVT/FPD(east) ready for data.

-   Continue to commissioning West FPD commissioning when there\'s beam.

-   Look for spin effects using the STAR scaler system.

-   Continue to commission the jet trigger for longitudinal running.

\(8\) PHENIX Status Report \[Matthias\]

What has been seen/accomplished over the last week \...

-   DAQ and trigger development now frozen, will run with LVL1 triggers
    at a rate of 1kHz and likely will use LVL2 trigger system in
    evaluation (not cut) mode.

-   Continuing to develop the spin monitoring and bunch-sorted scaler
    analysis code.

-   the MVD is operational but with a smaller acceptance; all other
    detectors are operating fine, though \-- when we have high
    luminosity beam, we will likely again have to deal with background
    issues.

What is planned for next week to be ready for physics?

-   measure LVL1 trigger rejections; after much tuning, we expect that
    our rejections are better this year than last year because the
    turn-on curve will be tighter. We need to make a measurement with
    beam to verify this.

-   will be ready to run in a shift or two.

\(9\) pp2pp Status Report \[Stephan\]

What has been seen/accomplished over the last week \...

-   put in the roman pots on Tuesday and did not trip the beam permit.

-   during the access on Wednesday, fixed some slight problems.

What is planned for next week to be ready for physics?

-   readout system is not ready, but Igor is coming next week to make it
    work. Starting to implement last year\'s readout system as a backup.