We derive the exact specification that a two-stage betatronic collimation insertion must satisfy to cut the halo of a proton beam down to its ultimate limit which is the aperture of the secondary collimators. Our result is a set of correlated phase advances between primary and secondary collimators. We then determine the number of jaws needed to reach a given level of performance. We also specify the optic of a momentum collimation insertion. [S1098-4402(98) 00024-X]
We report results on inclusive direct photon (); 0 , and production in both pp and pp interactions at p s = 2 4 : 3 GeV in the transverse momentum range 4:1 p T 7:7 GeV/c and rapidity range 0:1 y 0:9. The data were collected between 1988 and 1990 by the UA6 experiment at CERN, which employed an internal H 2 gas jet target in the S ppS collider. The inclusive direct photon cross sections and the cross section dierence (pp) (pp) expressed as functions of p T () are compared with next-to-leading order QCD predictions.
Beam loss and collimation issues at LHC can only be briefly outlined in three pages, but some emphasis is given to the bibliographic material. TABLE 1. Some LHC nominal parameters related to beam losses Luminosity 10 34 cm −2 s −1 Normalised emittence 3.75 µm β * at crossing 0.5 m σ * at crossing 16 µm Bunch population 1.05 10 11 protons Stored bunches 2800 Injection energy 450 Gev Collision energy 7000 Gev Injected intensity 12 × 2.5 10 13 protons Stored intensity 3 10 14 protons Stored energy (per beam) Injection 12 × 2 MJ ≡ 12 × 4 kg melted Cu Collision 304 MJ ≡ 800 kg melted Cu
The collimation system of the Compact Linear Collider (CLIC) must fulfil a number of conflicting requirements, namely it should (1) remove beam halo to reduce the detector background, (2) provide a minimum distance between collimators and collision point for muon suppression, (3) ensure collimator survival and machine protection against errand beam pulses, (4) not be excessively long, and (5) not amplify incoming trajectory fluctuations via the collimator wake fields. Two optical systems have been designed -the first linear, the second non-linear -, which promise to meet all these requirements for the design beam energy of 1.5 TeV. We decribe the various design criteria, a preliminary performance assessment, and outstanding questions.
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