PSB-PS TRANSFER AT 2 GEV - CONCEPTS AND OPTICS W. Bartmann, J. Abelleira et al. ABT LIU Review, 20-Nov-15

Aim of the PSB-PS transfer upgrade (as of 2013 review) All beams to be transferred at 1.4 and 2 GeV (until LS2 also 1.0 GeV in BT and BTM/BTY for ISOLDE, no 1.0 GeV after LS2) Magnet strength increased by 30% (Bρ 2GeV /Bρ 1.4GeV ) Can relax PS injection kicker fall time for LHC beam but not for HI beam LHC beam can be injected with existing kicker in short-circuit mode with longer fall time HI beam injection at 2 GeV requires additional kicker in SS53 Match optics at PS injection to reduce emittance blow-up due to dispersion mismatch Horizontal dispersion is presently not matched; install one additional quadrupole in BTP line to match the line to the PS injection optics Vertical dispersion remains mismatched due to the vertical displacement of the four PSB rings (Dy < 0.5 m) Optimise optics for different beams Requires ppm capability of HW (i.e. upgrade of BTP) 20/11/2015ABT LIU review, optics for 2 GeV transfer 2 New kicker specification Changed focus after 2015 review results

Layout BT 20/11/2015ABT LIU review, optics for 2 GeV transfer 3

Layout BTP and BTM 20/11/2015ABT LIU review, optics for 2 GeV transfer 4

Kicker specifications Initially assumed that same performance as of today is required Required additional kicker KFA53 to complement for 2 GeV beams injected in terminated mode Specifications for all kickers from PSB extraction, recombination and PS injection derived from requirements for LIU beams KFA45 can be modified to permanent SC mode and KFA53 be suppressed (see Thomas’ talk) Emittance growth due to different ripple on the waveform was studied for present and future system Last week new KFA45 solution approved by LIU-PS 20/11/2015ABT LIU review, optics for 2 GeV transfer 5

Emittance growth studies All details on kicker system studies will follow from Thomas Tool to estimate relative impact on beam coming from waveform ripple and rise/fall time wrt realistic bunch distributions Should not only focus on rise/fall times and flattop ripple since postpulse ripple is for the present system disturbing the beam most Emittance growth in % Flattop rippleRise/fall edgesPostpulse ripple LIU upgrade field Measured current present system Simulated current LIU upgrade /11/2015ABT LIU review, optics for 2 GeV transfer 6

Layout/optics changes Switching dipole deflection centre can stay  rematch BTP BTM.BHZ10 “fits” with a few mm distance from the wall, to be closely followed up Provided beam envelope for vacuum chamber specs First quad in PS zone eats into the wall  checks with RP ongoing 20/11/2015ABT LIU review, optics for 2 GeV transfer 7

Optics spread in the lines Edge focussing of recombination affects optics functions of each line differently 20/11/2015ABT LIU review, optics for 2 GeV transfer 8

PS injection Detailed integration studies ongoing Definition of Madx survey wrt data from surveyors ongoing 20/11/2015ABT LIU review, optics for 2 GeV transfer 9

Stability calculation Assign correctable errors and verify correction feasibility Only limited by BPM readings and correction strategy  checked in Oct-13, OK Assume machine free of correctable errors and assign separately dynamic errors to identify the main contributors to delivery imprecision Calculate delivery precision of position and angle at PS injection Check aperture in the lines (losses, radiation) Check foreseen margins for CO and betabeat in GFR Calculate emittance growth from steering error Calculate unavoidable emittance growth from optics and dispersion mismatch Sum all error sources into overall emittance growth and potential particle loss for LHC and HI beams 20/11/2015ABT LIU review, optics for 2 GeV transfer 10 R

Emittance growth From steering error at PS injection due to power converter ripple and kicker waveforms R x 2 /ε 0 (random errors ) gives and R x 2 /ε 0 (systematic offset) gives 0 and (extraction kicker waveform not included) From optics mismatch between different lines Energy error, geometrical mismatch and coupling negligible All error sources considered independent 20/11/2015ABT LIU review, optics for 2 GeV transfer 11 ErrorEmittance growth [%] Present situation (LHC) Emittance growth [%] LHC beam Emittance growth [%] HI beam HorVertHorVertHorVert Steering error Betatron mismatch Dispersion mismatch Total

Summary of layout and optics (shown at the review Sept-15) Since last review in Oct-13 Iterations on magnet design, integration and update of the optics model Resulting changes BT.BHZ10 can be kept at its centre of deflection  TL geometry can be kept Previously moved quadrupoles to make space can be kept at the present location Two locations of integration interferences (QNO20 with wall, QN040 with steerer) to be addressed Locations for extra BLMs identified Position for wideband pick-up in upgraded BTP to be checked Envelope for (new) BPMs required to be included in the integration Optics rematched accordingly One quadrupole (BTP.QNO20) due to difference in 4 lines increased GFR, but 25% lower gradient than max  within our margin Specifications for quadrupole gradients, field homogeneity and good field regions as from Oct-13 confirmed Specifications for power converter ripple as of beginning 2015 systematically checked and confirmed Random errors for both planes balanced Comparison of different sources of emittance growth show: Difference in optics between the four lines is the main cause of emittance growth, in particular the dispersion mismatch Emittance growth from steering errors due to power converter ripple is a minor contributor and can in principle be damped Assuming similar systematic contributions from PSB extraction and PS injection kicker in the horizontal plane as for the recombination kickers gives as maximum expected oscillations to be damped: +/- 1.5 mm in both planes The present mismatch situation is improved, but further optimisation required to balance the contributions from betatron and dispersion mismatch and thus reduce the overall emittance growth No additional particle loss due to emittance growth of HI beams 20/11/2015ABT LIU review, optics for 2 GeV transfer 12

Update since review end of September 2015 Further iterations with integrations  spotted issues with aperture model in Madx, being updated BTP optics: matching to reduce spread between lines  close to be finished BTM optics: go for dedicated measurement optics per line, lower prio PS injection: update of MADX survey ongoing Beam stopper: specification for energy deposition studies ongoing Study 160 MeV PSB extraction as preparation of H- inj commissioning Detailed study of trajectories at PS injection with 2 GeV strayfields from main units 20/11/2015ABT LIU review, optics for 2 GeV transfer 13