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Squeeze optics and power converter settings. Questions addressed: Can we ramp at constant optics and crossing scheme? Behaviour of optical parameters during squeeze of IR1 and/or IR5 Number of matched optics during squeeze Status of squeeze optics for IR2 and 8.

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Squeeze optics and power converter settings

Squeeze optics and power converter settings

  • Questions addressed:

  • Can we ramp at constant optics and crossing scheme?

  • Behaviour of optical parameters during squeeze of IR1 and/or IR5

  • Number of matched optics during squeeze

  • Status of squeeze optics for IR2 and 8

S. Fartoukh, M. Giovannozzi, J. Jowett, Y. Papaphilippou

LHCCWG - November 29th 2006


Introduction
Introduction

  • The material concerning the squeeze for IR1 and 5 can be found at:

    • S. Fartoukh -> 23 LTC meeting, 31/03/04.

  • The material concerning the crossing scheme for IR1 and 5 during the squeeze can be found at:

    • S. Fartoukh -> LOC meeting, 11/10/05.

  • All the optics files are stored in the official database under V6.5

LHCCWG - November 29th 2006


Can we ramp at constant optics and crossing scheme i
Can we ramp at constant optics and crossing scheme? - I

  • IR1 and 5:

    • Optics: injection optics can be ramped up to 7 TeV

    • Crossing scheme:

      • for beta* = 11 m, a = 200 mrad, par. sep. = 2 mm, MCBYs at Q4 (mainly for par. Sep.) are at 107% of nominal at 7 TeV -> the injection crossing scheme can be ramped (tight, but feasible).

      • For beta* = 17 m , a = 160 mrad, par. sep. = 2.5 mm, the same correctors are at 132% of nominal at 7 TeV -> the injection crossing scheme has to be changed at about 5 TeV.

LHCCWG - November 29th 2006


Can we ramp at constant optics and crossing scheme ii
Can we ramp at constant optics and crossing scheme? - II

  • IR2 and 8:

    • Optics: injection optics can be ramped up to 7TeV. Important point: strength of triplets is 220 T/m instead of 205 T/m (due to the injection contraints of phase advance between septum and kicker)!

    • Crossing scheme:

      • IR2: the MCBY correctors in Q4 are limited in strength. In principle the injection crossing scheme cannot be ramped up to 7TeV. This issue should be studied in more details to assess whether alternative solution is possible…

      • IR8: no strength limitation is present, even though the strengh requirements for MCBYs at Q4 are tight (due to par. sep.). Injection crossing scheme can be ramped up to 7TeV.

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 and or ir5 i
Behaviour of optical parameters during squeeze of IR1 and/or IR5- I

  • Status of squeeze optics:

    • 12 matched optics for various beta* are available.

    • Solutions provide smooth variation of the quadrupole gradients during squeeze.

    • A crossing scheme is implemented for each of the matched optics.

    • Criteria imposed on crossing scheme during squeeze:

      • Parallel separation kept constant

      • Scaling of the X-angles:

      • Scaling law for the IP shift:

S. Fartoukh LOC meeting, 11/10/2005

LHCCWG - November 29th 2006


Squeeze 3 4

S. Fartoukh, 23 LTC meeting IR5

Squeeze (3/4)

Quadrupole gradients [T/m] in the Dispersion Suppressor (Q7-Q10)

as a function of b*: beam1 (left) beam2 (right)

 Rather smooth except for 1 m <b* < 2 m

LHCCWG - November 29th 2006


Squeeze 4 4

S. Fartoukh, 23 LTC meeting IR5

Squeeze (4/4)

Quadrupole gradient [T/m] in the trim quadrupoles (QTL11,-QT12,QT13)

as a function of b*: beam1 (left) beam2 (right)

  • Smooth/monotonous for beam1 but more “erratic’’ for beam2, with unavoidable zero-crossing for both beams (matching procedure could be optimised if needed)

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 and or ir5 iii
Behaviour of optical parameters during squeeze of IR1 and/or IR5- III

S. Fartoukh LOC meeting, 11/10/2005

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 and or ir5 iv
Behaviour of optical parameters during squeeze of IR1 and/or IR5- IV

  • Simulation conditions:

    • Plain V6.5 layout with nominal optics.

    • No errors (alignment or magnetic) included.

    • The 12 matched optics are used (collision tunes – 0.31/0.32, and chromaticities set to 2 with SF/SD circuits).

    • In between two matched optics the gradients are obtained by linear interpolation.

    • For intermediate optics relevant beam parameters are evaluated.

LHCCWG - November 29th 2006




Behaviour of optical parameters during squeeze of ir1 iii
Behaviour of optical parameters during squeeze of IR1 - III IR5

Critical region for Beam 2: smoothing should improve it

Beam 2 seems to be more critical than Beam 1! However, no problem down to beta* = 2m.

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 iv
Behaviour of optical parameters during squeeze of IR1 - IV IR5

Critical region for Beam 2: smoothing should improve it

Beam 2 seems to be more critical than Beam 1! However, no problem down to beta* = 2m.

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 v
Behaviour of optical parameters during squeeze of IR1 - V IR5

Computed outside IR1/5

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 vi
Behaviour of optical parameters during squeeze of IR1 - VI IR5

Computed outside IR1/5

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 vii
Behaviour of optical parameters during squeeze of IR1 - VII IR5

Critical region for Beam 2: smoothing should improve it

Computed outside IR1/5

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 viii
Behaviour of optical parameters during squeeze of IR1 - VIII IR5

Critical region for Beam 2: smoothing should improve it

Computed outside IR1/5

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir1 ix
Behaviour of optical parameters during squeeze of IR1 - IX IR5

No impact of the squeeze on the beam parameters at IP.

7TeV crossing parameters. Matching with injection crossing to be discussed.

LHCCWG - November 29th 2006


Number of matched optics during squeeze i
Number of matched optics during squeeze IR5- I

  • Two test cases considered:

    • Removal of two matched optics (beta* = 4 m and 2.5 m).

      • Beta* = 4 m: whenever removed the optical parameters remain bounded, e.g., tune variation below 1E-3.

      • Beta* = 2.5 m: whenever removed the optical parameters grow, e.g., tune variation above 4E-3.

    • Academic case: remove successive points below 11 m to determine behaviour of optical parameters.

LHCCWG - November 29th 2006


Number of matched optics during squeeze ii
Number of matched optics during squeeze IR5- II

LHCCWG - November 29th 2006


Number of matched optics during squeeze iii
Number of matched optics during squeeze IR5- III

LHCCWG - November 29th 2006


Number of matched optics during squeeze iv
Number of matched optics during squeeze IR5- IV

LHCCWG - November 29th 2006


Behaviour of optical parameters during squeeze of ir5
Behaviour of optical parameters during squeeze of IR5 IR5

  • Whenever IR5 is squeezed the results are very much the same as for IR1 (taking into account the exchange of the crossing plane): no particular new issue observed.

LHCCWG - November 29th 2006


Behaviour of optical parameters during combined squeeze of ir1 and 5 i
Behaviour of optical parameters during combined squeeze of IR1 and 5 - I

  • Larger variations of the optical parameters are observed. In particular:

    • Horizontal and vertical planes have equal behaviour for closed orbit leakage < 0.1 s.

    • Beam 1:

      • Factor 2 larger tune variations -> DQ ~ 3E-3

      • Chromaticities almost unaffected -> DQ’ ~ 0.15

      • Factor 1.5 in beta-beating -> Db/b~ 1.5%

      • Orbit leakage almost unaffected < 0.1 s

    • Beam 2 (similar values as ofBeam 1, except for 1 m <beta* < 2 m):

      • Factor 2 larger tune variations -> DQ ~ 6E-3

      • Chromaticities strongly affected -> DQ’ ~ 2

      • Factor 1.5 in beta-beating -> Db/b~ 10-15%

      • Orbit leakage almost unaffected < 0.1 s

LHCCWG - November 29th 2006


Behaviour of optical parameters during combined squeeze of ir1 and 5 ii
Behaviour of optical parameters during combined squeeze of IR1 and 5 - II

Critical region for Beam 2: smoothing should improve it

LHCCWG - November 29th 2006


Behaviour of optical parameters during combined squeeze of ir1 and 5 iii
Behaviour of optical parameters during combined squeeze of IR1 and 5 - III

Critical region for Beam 2: smoothing should improve it

LHCCWG - November 29th 2006


Status of squeeze optics for ir2 and 8
Status of squeeze optics for IR2 and 8 IR1 and 5 - III

  • As far as the other insertions are concerned:

    • IR8:

      • it is foreseen to be squeezed down to beta* = 2 m (1 m is excluded due to aperture issues).

      • Optics files present, but not optimized, yet (quadrupoles variation not smooth enough). Once the optical solutions will be in final form, the approach presented should be repeated. The crossing scheme needs also to be implemented during the squeeze.

    • IR2:

      • it is foreseen to be un-squeezed for protons and squeezed down to beta* = 0.5 m for ions.

      • Optics files for the un-squeeze are still missing, while those for the ions are available. In both cases the crossing scheme needs to be computed.

    • IR2 and 8: transition from beta* = 10 m and MQX strength from 220 T/m to 205 T/m.

LHCCWG - November 29th 2006


Summary and outlook
Summary and outlook IR1 and 5 - III

  • MADX tool developed to qualify the squeeze.

  • Ramping with constant optics (injection) up to 7TeV is feasible (for IR2 and 8 it will depend on performance of triplet quadrupoles).

  • Ramping with constant crossing scheme (injection) up to 7TeV is problematic for IR2 (to be re-computed) and thigh, but feasible for IR1, 5, and 8.

  • Strength issues will not impose the choice of when to change optics/crossing scheme.

  • Squeeze with one insertion at a time (IR1 or 5) is not an issue in terms of optical parameters (and for a perfect machine).

    • Impact of errors to be assessed.

    • Behaviour of Beam 2 to be analyzed in details (possibly fixed by smoothing transition between beta* 1 m and 2 m).

  • Squeeze with both insertions at a time (IR1 and 5) is feasible, provided situation of Beam 2 is fixed.

  • Optics squeeze of other insertions (IR2 and 8) to be computed/finalized. Their contribution should be assessed.

  • Transition from injection to collision crossing scheme to be studied.

LHCCWG - November 29th 2006


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