Continuous injection background

1
Continuous injection background
Shoji Uno (KEK) Nov.-16th , 2004 at Belle-Babar
joint Background meeting
2
Time structure of continuous injection
200xMIP
10msec

• 100nsec

200msec
3.5msec
3
Data size

• Veto time
• 3.5msec
• Originally, 2msec
• There are events with larger data size after veto
  window.
• Fraction of events with larger data size is quite
  small.

4
Background condition(short term)
Back Storage Blue HER injection Read LER
injection

• The beam background is fluctuate for various
  accelerator condition, especially during the
  injection.
• Injection parameters and movable masks are
  adjusted to reduce the beam background.

5
Unstable injection background

• Injection background is not stable.
• Background at HER injection was worse before
  starting continuous injection mode.
• Background at LER injection is not stable,
  recently.
• It was less problematic before the first CIM
  test.
• The background at just injection time is higher
  than before and HER injection.
• Duration is longer than the veto time, sometimes.
• There are no damping ring for both electron and
  positron in KEKB.
• We have an energy compression system for positron
  only to reduces the energy spread.

6
Near future

• We started study to understand the injection
  background in detail.
• Collimators in BT line is not so effective for
  the injection background.
• We want to understand the time structure.
• Usual tuning for the injection system is
  effective to get some background level. But, it
  is not sufficient for further improvement.
• So far, we do not know which parameter is a key
  to keep the injection background low and stable.
• Movable mask is also effective to reduce the
  background. But, it is not sufficient to keep
  the background stable.