Log entry time 23:59:48 on May 09, 2004

Entry number 84621

Run Coordinator Daily Report for 8 May Owl to 9 May Swing

Summary

Threshold studies have been completed.
During  Sunday Owl  we took LH2 production data at 40 uA (1 h,  IHWP=IN).
On Sunday morning , we decided that we should also take some data with Hall C off to measure the HallA + B leakage as a function of time. These are short runs as we use only the lumis.
During that time intense negociations were done with different parties in order to get approved a signnificant time with Hall A off.

GMS is still off.
 

Significant News

On Saturday Owl, we have had the opportunity to do a leakage measurement of Hall B, with Hall A off.  We divided the time in  two 4-hours period:

•  one period of 4 hours was  to measure Hall B leakage with a high precision by inducing large beam asymmetry using thre RWP (Rotatable Wave Plate).

The standard value to minimize Hall C beam asymmetriy (all sources added) is 7600. We used a value of 6200 who gave asymmetries in Hall B beam to
up to 14000.
• another period  for studying the sensivity of the leakage into Hall C  as a function of Hall B operating parameters (laser power, slit opening...)


The results are the following (the raw  data are shown in g0log 84519):

• by inducing artificially a large asymmetry, we increase the statistical significance but at the same time we become very sensitive to small changes in the operating conditions. The results were not reproducible with time at a 3-4 standard deviation level.. In these conditions it was impossible to validate the procedure using cut 0 as it implies a subtraction of 2  large numbers.
• then we reduced the Hall B asymmetry to about 2000 (RWP=7500), and there we got consistent results with the cut0 method at a 300ppm level .
• the results of the sensivity to Hall B parameter tests is very encouraging. We varied the HallB laser parameters over a wide range:  slits at 100-300-600,  laser control level (which controls the laser power) between 36 and 49, two different settings for the prebuncher. The Hall B

current varied from about 2 to 60 nA. If we discard  the 2 runs with very low (unphysicall) Hall B beam intensity , all the asymmetries measured
with both the FPDs and lumis are within +/- 10%, meaning that we are not very sensitive to Hall B parameters.

• these resullts confirmed our preliminary conclusions stating that we could validate the cut0 method at a level below 100 ppm  in 3-4 shifts.
• finally we got approved to run during 4 periods of 8h without Hall A (and without Hall B for very short periods of time)

Short term Plans

- Reference_FiB_Buddy
- NA thresholds to 7 and FR thesholds to 50mV

1) Leakage studies  with Hall A OFF
During these studies we will alternate  3 types of runs:

• Hall B off, Hall C into Hall A slits by rotating laser phase (detailed instructions for MCC are given in g0log 84607). This will allow to measure HallC_leak directly. Take 2 runs of 10', one at beginning of shift and one around the end (1/2h before Hall A is scheduled to come back). I have arranged with Hall B that before doing this test, we should ask them the permission to shut off the Hall B laser (that will be done at the end of a Hall B run). Increase lumi sensivity (HV file to highhigh and amplifier x 10): see below
• Hall B on, HallC laser off. This will measure directly Hall B leakage.  Increase lumi sensivity (HV file to highhigh and amplifier x 10).

Take 3 runs of  10', one at beginning,  one at end (preceding or following HallB off runs) and one in the middle of a 8h period.
• The bulk of the data is be to alternate HallB on, HallC on, with 40 muA  into HallC (standard production run, 1h) with HallB on, Hall C on, but sent into Hall A slits (10'  runs):

    - with HallB+C on, we measure the asymmetry in cut0
    - with HallB on and HallC beam into HallA slits we measure HallB+C leakage.
DON'T FORGET TO RESET LUMI TO LOW GAIN WHEN BEAM IS SENT TO HALLC
2) When HallA and Hall B are ON
Alternate 2 types of runs:
• Hall C on, 40 uA. Take 1h runs
• Hall C off (Laser off, slits wide open), take 10' runs


DON'T FORGET TO CHANGE THE LUMI SETTINGS WHEN SWITCHING FROM ONE TYPE OF RUN TO THE OTHER.
 

SETTINGS TO BE USED WHEN RUNNING WITH NO CURRENT IN HALL C

• Lumi gain has to be multiplied by 1000, this being obtained by gaining a factor 100 using an increase in HV and another factor of 10 by
changing the gain of the lumi amplifiers. For that:
            - Switch from standard  lumi  HV file HV.2004-02-19.lumi_halo_on.hvcto HV.lumi_highhigh_on.hvc
            - Change the 6 lumi amplifier settings in Electronics Shack  upstairs (if you don't know how to do,ask Mark Pitt or Jianglai or the RC).
• change BCM 1 and BCM gains from 3==>5 in rack CH03B11 in Hall C electronics room. These will most likely not work as sensivity

is 1 uA only for these settings but it does not hurt.

Longer term Plan

• Follow the above procedure until Thursday morning.
• Next week (tentatively on Tue or Wed): one full Day Shift will be devoted again to SOS tests (to be confirmed)

 

 

Concerns

Transverse spin  running could be done at the end of the week (Thu-Sun) if we get an extension and if we find volunteers. 
To be discussed at RC meeting tomorrow at 11:00