The 2mrad crossing angle layout for the ILC

1. The 2mrad crossing angle layout for the ILC R. Appleby, Cockcroft Institute and the University of Manchester, UKD. Angal-Kalinin, CCLRC, ASTeC, Cockcroft Institute, Daresbury Laboratory, UKP. Bambade O. Dadoun, LAL, Orsay, FranceB. Parker, BNL, Upton, Long Island, New YorkL. Keller, K. Moffeit, Y. Nosochkov, A. Seryi, C. Spencer, SLAC, Menlo Park, CaliforniaJ. Carter, John Adams Institute and Royal Holloway, University of London, UKO. Napoly, CEA/DSM/DAPNIA, Saclay The baseline layout of the International Linear Collider contains two interaction regions, with two detectors, and a different beam crossing angles. One angle is large (20mrad), and the interaction region and extraction line is well understood. The other angle is small (2mrad) and presents considerable design and technological challenge. The first complete optics, optimised for the 1 TeV ILC was first presented at Snowmass in 2005. The extraction line optics contained energy spectrometry and polarimetry diagnostic structures, and low energy beam tail collimation. The 500 GeV extraction line is not optimised, and obtained by scaling the fields. The disrupted beam in the final doublet magnets, for the 1 TeV Nominal beam parameters, are shown below. Power losses in the downstream region are high, and will cause problems with the normal and superconducting magnets used in the design. The outgoing horizontal and vertical beam envelopes Reoptimised final doublets The extraction line The optimised final doublets have been integrated into the downstream extraction line, and the extraction line optics optimised for the 500 GeV machine. The optics are constrained to provide a beam phase space distribution suitable for polarimetry and energy spectrometry. The polarimetry diagnostics require a dispersion dominated beam size at the Compton interaction point and the beam has to be parallel to the beam at the main interaction point to avoid spin precession. These conditions are sufficient to match the extraction line quadrupoles and dipoles into the final doublet. The extraction line linear optics and the dispersion for the extraction line based on the NbTi final doublet are: We have used current and proposed advances to redesign the final doublet layout. NbTi coils are an established technology, and Nb3Sn coils are under R+D at the present time. The reason can be seen by looking at the final double charged beam and radiative Bhabha losses for the Low Power parameter set: • These losses are high, and will quench the magnet. Therefore we propose three new final doublet layouts: • NbTi layout for the 500 GeV machine • NbTi layout for the 1 TeV machine • Nb3Sn based layout for the 1 TeV machine The layout parameters were optimised by scanning the parameter phase space, using the total charged beam and radiative Bhabhas losses as a figure of merit. The result is three new layouts, each with shorter magnets and improved losses from beam transport. As an example, the new losses for NbTi doublet for the 500 GeV machine are: The beam transport properties, disrupted beam power losses, interaction region backgrounds and diagnostic performance is currently under study. The improvement over the table above can be seen. The localised peak power deposition into the coils of the superconducting magnets can be reduced using Tungsten liner on the particle deposition hotspot. The use of such a linear, in combination with the doublet parameters calculated here, give power losses in the final doublet which are less than the magnet quench limit for most beam parameter sets under current consideration. • We present optimised final doublet and extraction line layouts for the 2mrad crossing angle scheme of the ILC. We consider current and proposed superconducting magnet technologies to redesign the final doublet region, and present corresponding extraction line optics.Ongoing work included studying beam transport, interaction region backgrounds and diagnostic performance.