LHC Optics with Crab Cavities

Phase I (Global Crab Scheme)

A global crab scheme where the cavities are placed in the accelerating RF section (IR4) due to space constraints in the IR1/IR5 and RF infrastructure issues is considered as the best choice for the first experimental test of crab cavities in hadron colliders.

Phase II (Local Crab Scheme)

A new approach to the existing IR upgrade optics by using additional D11 & D22 dipoles to separate the two beam lines to ~25 cm for inserting crab cavities is a viable solution for 800 MHz cavities. The distance between the presented D1 and D2 magnets can be increased by about 20m to ease the insertion of these new dipoles.

D2 69 53 3.85 10
Magnet Aperture-H [mm] Aperture-V [mm] Tesla L [m]
D1 134 110 7 10
D11 106 70 7 10
D12 78 60 4 10

Details of this conceptual optics can be found in Ref. LHC Optics: X-Angle ~ 0.5 mrad - R. Tomas et al.

Separate Focusing Channel Scheme (Old Proposal)

A first proposal (CARE-HHH, Valencia) with separate quadrupole channels for the two beam with large crossing angle (~8 mrad) was envisioned but was found to be risky since the entire upgrade would rely on the functioning of the crab cavities. The luminosity of this laytout without crab cavities drops by a factor of 25, with crab cavities increases by a factor of 2, with respect to the nominal LHC luminosity.

BXC 42 8.2 T 9.45
Magnet Aperture [mm] Tesla L [m]
QX1 46 200 T/m 6.3
QX2 63 200 T/m 5.5
QX3 63 200 T/m 5.5
BXA 59 5.3 T 17.6
BXB 39 8.6 T 9.0

Optics and Dispersion for 8 mrad Separate Quad Channels 10 sigma beam envelope near the IR

-- R. Calaga - Jul 1, 2009

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Topic revision: r8 - 2010-06-02 - Rcalaga
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