LHC Integration

Phase I: Prototype Tests (IR4, Global)
Phase II: Full Crab Implementation (IR1/5, Local)

The crab crossing scheme in the LHC is anticipated in two phases:

  • Phase I: Two 800 MHz elliptical cavities placed in the IR4 region equipped with a dog-leg to accommodate the cavity transversely. This phase will test crab crossing in a hadron collider for the first time and serve as a feasibility test for luminosity gain, leveling and machine protection through the LHC cycle.
  • Phase II: Four cavities per interaction region at IP1 & IP5 may be installed in conjunction with the phase II of the LHC IR upgrade. This upgrade scenario will require a special dog-leg to separate the beams between the D1 & D2 magnets by approximately 25 cm or larger (see optics section). If compact cavities were to be available at this time, a lower frequency (400 MHz) crab cavity will be used.

Phase I, Integration

The IR4 region is the only place with a special dog-leg to separate the beam-lines by approximately 42 cm which is sufficient to accommodate 800 MHz crab cavities for the phase I crab cavities. A compromise between highest frequency due to long proton bunches and transverse space limitations lead to the 800 MHz choice. At present two locations in the IR4 which are reserved for an additional transverse damper (3-4m) and capture cavities (~9m) are potential locations for the test cavities.

Left of IR4

Right of IR4


The operating temperature of 2K is preferred for 800 MHz superconducting cavity. However, the physical constraints and the availability of the 2K Helium (@30 mbar) at the IR4 location may limit the operating temperature to 4K (atm pressure). The cryogenic circuit should accommodate the RF losses at 4-5K. Some relevant parameters are listed in the table below with preliminary conceptual design of the cryogenic circuits for both 2K and 4-5K temperatures.

Helium Volume 35-50 L (approx)
Voltage 2.5 MV
Q_0 1x10^9
R/Q 120 Ohm
Cavity Losses 52 W @2K
Coupler Losses NE @4K

5 Kelvin Circuit

-- R. Calaga, July 18, 2009

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Topic revision: r5 - 2009-07-28 - RamaCalaga
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