TREX Matters arising 23 rd April 2015 VELO

TREX Matters arising 23 rd April 2015

VELO validation Criteria Status Aperture To be revisited (Massimo et al). Change in reference scenario, levelling, beam parameters etc. Mechanical and positioning tolerances OK Impedance • OK for increase in longitudinal impedance – should crosscheck with HL-LHC parameters (Elena Chapochnikova) • Benoit Salvant to re-check model, possible corrugation depth optimization – seeing Massi on 29 th April Vacuum stability OK – see VELO workshop Background LHCb to perform Monte Carlos – not expecting any issues (G. Corti) – see VELO workshop Machine protection/collimation Revisit for confirmation (Stefano et al)

Miscellaneous • Additional IPQ cables in IRs 1 & 5 – ECR for Q 4 installation in IR 1 to be released soon – Space reservation for Q 7/Q 8 on hold • CMS TAN cranes – “create the documentation, to launch the procedure, tests will be done during technical stop 1” – TS 1 now delayed until 15 th June

ALICE ZDC/protection devices post LS 2 • JJ gives required crossing angle given by long range beam-beam separation • ALICE want to avoid ZDC being shadowed by any (injection) protection devices • Need to ensure that existing and planned upgrades respect the constraints as much as possible

John Jowett’s conclusions • If – half-gap of 29. 5 mm is feasible for TCLIA and – it can be moved to 72. 748 m from IP (end of jaw) • then we can have ± 100 μrad half-crossing angle at IP 2 giving ~6σ separation with 50 ns bunch spacing (and nominal emittance) • New TDI proposal comfortable • TCDD seems OK if ± 35 mm vertical clearance is available in flange, open position