Effect of the sextupole field component of the MR bending magnets and the variation of the strength of the MR sextupole magnets

1
Effect of the sextupole field component of the MR
bending magnets and the variation of the strength
of the MR sextupole magnets

• Alexander Molodozhentsev (KEK)
• RCS-MR group meeting
• June 9, 2006

2
Footprint for 1.8 kW/bunch, Bf0.2
WP1 Qx22.43, Qy20.82
WP2 Qx22.30, Qy20.92
Qy21
Qy21
Rectangular beam pipe ? 70 mm
Laslett incoherent tune shift (estimation)
?Parab.100 54 ? mm.mrad ??incoh - 0.14
(for ?1)
- 0.07 (if ? ltlt 1)
Footprint after 5000 turns
3
Space charge Sextupole Nonlinearity (NO errors)
WP1 Qx22.43, Qy20.82

• Injection dogleg
• break the MR super-periodicity
• Excitation of non-structure resonances, in
  particular 1,2,64, 3,0,67
• and 0,4,83

4
Measured field components, involved into
consideration

• Sextupole component of MR Bending magnets
  (961)

• Sextupole component of MR Sextupole magnets
  (72)

Location of each bending magnets and each
sextupole magnets in the ring is fixed according
to the magnet index.
Measurement has been performed by using the
rotating coil (March, 2006)
5
Measured field for MR-BM
Assumption ltb3/B1gt1000A(20GeV) ltb3/B1gt3GeV
Winj 3GeV B?12.7578 T.m B0Leff 0.835
T.m R0 0.01909 m (coil radius)
Gaussian distribution of the sextupole field
components for 96 magnets at the injection energy
with
ltk2LgtMAD 5.2?10-3 m-2
1? 4.2?10-3 m-2, cut3?.
6
Measured field for SX ?b3 lt 0.002
SFA
SDA
SDB
Relative deviation from the non-integrated
ideal strength of the sextupole magnets (3
families, 72 magnets) at the injection energy
3GeV.
April, 2006 (Niki san data)
7
Effect of the sextupole errors in combination
with Injection Dogleg (1)
Qx22.42, Qy20.80 1,2 3,0 0,4
additional contribution to the 1,2 3,0
resonances.
INJDLALL all elements of the injection dogleg
have the same timing.
MR Beam Power 1.8kW/bunch
8
Particle Losses at Scraper
MR Scraper Acceptance 70 ? mm.mrad
MR Beam Power 1.8kW/bunch
WP1 Qx22.43, Qy20.82
WP2 Qx22.30, Qy20.92
Particle losses are caused by the broken
super-periodicity.
Injection Process with the realistic timing of
BPs and OPMSs.
9
Conclusion

• Contribution of the sextupole component of the MR
  bending magnets and variation of the strength of
  the sextupole magnets from magnet to magnet to
  excitation non-structure normal sextupole
  resonances is small
• and does not lead to significant increasing the
  particle losses at the MR scraper.

10
Next to be done

• influence of the skew resonances.