Beam%20parameters%20for%205%20TeV%20operation%20in%202008

1
Beam parameters for 5 TeV operation in 2008

• M. Giovannozzi

• General assumptions
• Aperture
• Luminosity
• Overall target parameters
• Next steps
• Acknowledgements E. Chapochnikova, W. Herr, J.
  Tuckmantel

2
General assumptions - I

• The analysis is based on the general parameters
  for Phase A.
• In particular, no crossing angle is assumed and
  the same values for beta.
• Longitudinal parameters
• Nominal at 7 TeV
• Emittance 2.5 eVs (due to blow-up)
• Bunch length 7.55 cm
• Rms energy spread 1.13 10-4
• At 5 TeV one can assume the same values. However

3
General assumptions - II

• The hardware for generating the longitudinal
  blow-up will not be ready for the commissioning.
• Hence, emittance will be of the order of 1 eVs
  even at top energy.
• The corresponding set of beam parameters (5 TeV
  or 7 TeV) will have to be defined (discussions
  with Elena on-going).

4
Aperture - I
7 TeV
Aperture in IR1 at top energy with beta2 m and
no crossing angle
5 TeV
5
Aperture - II
IR8. Spectrometer at 7 TeV value
Aperture in IR2 and 8 at 5 TeV with beta10 m
and 2 m, respectively. No external crossing angle
IR2. Spectrometer at 7 TeV value
6
Aperture - III
Summary of aperture bottleneck at 5 TeV
Aperture in IR5 at 5 TeV with beta2 m. No
crossing angle
N1 min Location
IR1 14 Q2
IR2 24 Q6
IR5 14 Q2
IR8 14 Q2
7
Aperture - IV

• Some additional remarks
• Werner analysed in details the situation with the
  external crossing angle for IR8. Down to beta2
  m aperture and separations are enough until bunch
  spacing of 50 ns.
• Simulations concerning aperture vs. beam energy
  with
• beta as from Phase A
• No crossing angle
• Constant separation bump

8
Luminosity

• Target values depend on bg
• Re-scale values from Phase A by 0.71.
• Luminous region
• Assuming same longitudinal parameters, then it
  re-scales with respect to the nominal case by
  0.71.
• Nominal case
• The final result depends on the value of the
  longitudinal parameters

9
Overall target parameters

• First iteration on target parameters made (43 and
  156 bunches).
• Finalisation once the longitudinal parameters
  will be fixed.
• Also the table for the synchrotron radiation
  effects will need to be updated.

10
Next steps

• Define longitudinal parameters
• Re-evaluate the global set of beam parameters
• Evaluate the situation concerning the radiation
  damping
• However, the optics configuration is already
  available from the official LHC web site
• http//lhc.web.cern.ch/lhc/