1. BG study (M.Tanaka)
KEKB started high emittance operation to increase the luminosity. Tanaka
studied the clueter energy spectrum taken in the single bunch study. The 30
keV peak is reduced. The rate for the MIP energy range is also reduced from
the data one month ago. It is not clear if this is due to the high emittance
operation or better dynamic pressure. SVD PIN dose rate is also reduced to
2.4mRad/s during storage. Occupancy(or radiation dose)/current VS vacuum
pressure should tell us wheter the high emittance operation improves the BG.
Dejan reported a few incidents with sudden dose increases after the high
emittance operaqtion. Interestingly, we do not see large PIN dose. Further
study to understand the origin and careful monitoring of the radiation dose
is crucial for a while.


2. Radiation monitor (Zontar)
Dejan described the current status of the radiation monitoring. He found
that PIN dose varies by a factor of more than 5 from diodes to diodes. Since
MOSFET shows similar dose regardless of the device position, this variation
is not due to the position. The dose difference is probably due to the gain
difference. He recalibrated the PIN dose to the average FET dose to correct
the gain difference.
While studying the hardware abort, he found that the PIN diode output (well
actually preamp output) saturates very often. The saturation level is 1-10
Rad/s depending on the PIN. During injection, it saturates for every
injection. So, we can not use raw pulse height from the preamp for the
hardware abort. He use the duration of the saturation as an abort signal. He
is investigating how long it should be.
Conclusion: The radiation dose from PIN is not so accurate. It is still
useful as an instantaneous beam abort. We should use MOSFET for the
integrated radiation dose.

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+ Comments by Tsuboyama-san et al on background events


Dear colleagues,   
As D.Zonter showed in yesterday's SVD meeting, there were three
moments with extremely high dose rate while the high-emittance run of
KEKB was prepared.  

SVD has suffered radiation 0.2 to 0.4 krad, depending on the radfet
position.  Only F-90 sensor, which is put on Beryllium pipe, suffered
1.3 krad in a few minutes. The F-VA1 sensor which is placed at F-90
position, behind 300 um gold plates, suffered about 0.6 Krad. It seems
that the 300 um gold, together with the slight larger distance from
the beam center could reduce the radiation level by 1/3.  

1) December 2 16:20
   Since the injection to LER was poor, LER movable masks were fully opened.
SVD issued beam abort at LER current of 4 mA.

2) December 5 17:20
   Since the injection to LER was poor, LER movable masks were fully opened.
SVD issued beam abort at LER current of 20 mA.
      
3) December 8 19:58
   When vacuum leakage happened. Beam is aborted by SVD.
   

Graphs were read out by eyes.  
                            Dec.2    Dec.5   Dec.8
           Sensor           16:20    17:20   19:59
F   0 degrees on Be tube     0.6      0.3     0.4
F  90 degrees on Be tube     0.05     0.1     0.1
F 180 degrees on Be tube     0.05     0.1     0.05
F  90 degrees close to VA1   0.1      0.15    0.15
B 180 degrees on Be tube     0.05     0.1     0.1
=============================================================