PowerPoint Presentation

Injector beam requirements and optionsGiovanni Rumolo and Hannes Bartosik

Acknowledgments: G. Arduini, T. Bohl, H. Damerau, J. Esteban-Mller, A. Findlay, R. Garoby, S. Gilardoni, B.Goddard, S. Hancock, G. Iadarola, B. Mikulec, Y. Papaphilippou, E. Shaposhnikova, R. TomsPS & SPS Operation crewsLBOC, 8 April 2014

Proposed LHC start up in 2015450GeV6.5 7 TeVIntensity ramp up & physics with 25ns450GeV6.5 7 TeVFrom LMC, 27 November 2013LHCPROBELHCINDIVLHC50 (std)up to 1.5 x 1011 p/bLHC25 (std)1.2 x 1011 p/bLHC50 (std/BCMS)up to 1.7 x 1011 p/bLHC25 (std)1.2 x 1011 p/bLHC25doublet1.6 x 1011 p/doubletLHC25 (std/BCMS)up to 1.3 x 1011 p/bLHC25 (BCMS)up to 1.3 x 1011 p/bLBOC, 8 April 2014Use of low e-cloud filling patternsOr, if scrubbing not sufficientPossible alternativeLHC25 (8b+4e)up to 1.8 x 1011 p/b2LHCPROBE & LHCINDIV specs @LHC injection3LHCPROBELHCINDIVIntensity [p/b]5 x 109 2 x 10102 x 1010 3 x 1011Transverse emittance, 1s [mm]1 < 2.5Longitudinal emittance [eVs]0.350.35 0.5LHCPROBE usually below or about 1010 p/b, transverse emittance not criticalLHCINDIV parameter range also extended in MDs to produce single bunches with up to 4 x 1011 p/b and/or with lower longitudinal emittances (down to 0.15 eVs) at SPS injectionAccelerate and extract high intensity variants for possible impedance or beam-beam studies ?LBOC, 8 April 2014LHCPROBE & LHCINDIV 2013 statusSince 2013, new production mechanism in the PSB to cover parameter range for both these beams (S. Hancock, CERN-ATS-Note-2013-040 MD)Based on longitudinal blow up (C16 voltage) during the first part of the cycle for intensity settingIt provides unprecedented intensity shot-to-shot reproducibility and preserves the 6D phase space unchanged for different intensity values4

LBOC, 8 April 2014LHCINDIV VdM 2012 statusIn 2012, a new single Gaussian bunch was produced for Van der Meer scans (H. Bartosik and G. Rumolo, CERN-ACC-NOTE-2013-0008 MD)Based on longitudinal AND transverse shaving in the PSB to obtain large emittance single bunches with less than Gaussian tailsProvides Gaussian bunches with the desired intensities in the SPS after scraping5LBOC, 8 April 2014Single bunch beam parametersIntensity7 9 x 1010 p/bTransverse emittance (norm.) 2.5 mTransverse distribution Gaussian

LHC50 (std & BCMS) pre-LS1 status50 ns beam at the SPS extraction in 2012/13 (Q20) Combined wire-scans at end of SPS flat bottom (values cross-checked with LHC)Error bars include spread from measurements as well as systematic uncertainty (10%)Intensity measured at SPS flat top after scrapingTransport through PS and SPS within intensity loss and emittance blow up budgets6Four trains of 36 bunchesRoutinely used for physics in 2012Three trains of 24 bunchesSent to LHC only for test to prove luminosity gainLBOC, 8 April 2014

LHC25 (std & BCMS) pre-LS1 status7Four trains of 72 bunchesUsed for the LHC scrubbing run in 2012Three trains of 48 bunchesUsed for the LHC pilot physics run in 2012LBOC, 8 April 201425 ns beam at the SPS extraction in 2012 (Q20) Combined wire-scans at end of SPS flat bottom (values cross-checked with LHC)Error bars include spread from measurements as well as systematic uncertainty (10%)Intensity measured at SPS flat top after scrapingTransport through PS and SPS 15% above budgets for std beamPre-LS1 performance850 ns beam (both standard production and BCMS) already very close to the limits in injectorsIntensity per bunch: close to the limit of longitudinal instability in the PSBrightness: BCMS at the present space charge limit in the SPS

25 ns beam (both standard production and BCMS) already very close to the limits in injectorsIntensity per bunch: 10% from the limit due to RF power and longitudinal instability in the SPSBrightness: At the present space charge limit in the PS

LBOC, 8 April 2014Post-LS1: Expected performance9Higher intensityExtended reach thanks to the upgraded longitudinal feedback in the PS25 ns expected to be limited to 1.3 x 1011 p/b because of RF power and longitudinal instabilities in the SPS

Higher brightnessRF manipulations in the PS @2.5 GeV (instead of 1.4 GeV) PS extraction time moved to c2850 for all 3bp LHC cycles Larger longitudinal emittance from the PSBSpace charge alleviated by both longer bunches and larger momentum spreadPSB control of longitudinal parameters along the cycleControlled longitudinal emittance blow up to produce the required longitudinal emittancesUse of h1+2 in phase at the PSB extraction to keep these larger longitudinal emittance bunches within a certain length (recombination kicker rise time constraint)

LBOC, 8 April 2014Longitudinal emittance per bunch at PS injection should not exceed

[Total Split Factor x 0.35 eVs]/1.1 (includes 10% margin for blow-up)About 3 eVs (h=7) and 2 eVs (h=9) for RF manipulations at Ekin=2.5 GeV[FB Split Factor x 1 eVs] for transition crossing in h=21 Matched value in the PSB (h1+2) to obtain the above bunch lengths

Post-LS1: PSB PS transfer10

Recombination kicker rise time:EkinBucket lengthMax bunch lengthBunch length (pre-LS1)h=7 (std)1.4 GeV327 ns220 ns180 nsh=9 (BCMS)1.4 GeV255 ns150 ns150 nsLBOC, 8 April 2014Kinetic energy, EkinRise time1.4 GeV105 nsLongitudinal emittance per bunch at PS injection should not exceed

[Total Split Factor x 0.35 eVs]/1.1 (includes 10% margin for blow-up)About 3 eVs (h=7) and 2 eVs (h=9) for RF manipulations at Ekin=2.5 GeV[FB Split Factor x 1 eVs] for transition crossing in h=21 Matched value in the PSB (h1+2) to obtain the above bunch lengths

Post-LS1: PSB PS transfer11Recombination kicker rise time:EkinBucket lengthMax bunch lengthBunch length (pre-LS1)h=7 (std)1.4 GeV327 ns220 ns180 nsh=9 (BCMS)1.4 GeV255 ns150 ns150 nsLBOC, 8 April 2014RF Manipulation:@1.4 GeV@2.5 GeV50 ns (Std/BCMS)1.2/0.9 eVs1.9/0.9 eVs25 ns (Std/BCMS)1.2/0.9 eVs2.8/1.5 eVs

Kinetic energy, EkinRise time1.4 GeV105 nsPost-LS1: LHC25 (std & BCMS)12

Std with new longitudinal parameters

BCMS with new longitudinal parametersLBOC, 8 April 201420122012Post-LS1: LHC25 and LHC50 (std & BCMS)1325 nsIntensity (p/b)Emittance (mm)Standard1.3 x 10112.4BCMS1.3 x 10111.350 nsIntensity (p/b)Emittance (mm)Standard1.7 x 10111.6BCMS1.7 x 10111.1Achievable beam parameters at the LHC injection after LS1Assuming:Transport in the PS and SPS within budgetsBenefits from reviewed longitudinal parameters in the PSB PS transferSuccessful SPS scrubbing after exposure to air during LS1

Summary tablesLBOC, 8 April 2014LHC25doublet (scrubbing beam)Machine tests in the SPS at the end of 2012-13 runDoublet production scheme at SPS injection validatedE-cloud enhancement experimentally demonstratedThe production scheme is based on splitting of long bunches at SPS injection Injection of trains of 72 x 10ns long bunches with 1.7e11 p/doublet on unstable phase and capture in two neighboring bucketsShould be fine in LHC only interlocked BPMs to be checked with doublets

1442860123Time [ms]200 MHz RF Voltage [MV]4-201st inj.

LBOC, 8 April 2014LHC25doublet (scrubbing beam)15

We need to accelerate 1.6 x 1011 p/doublet in the SPSex,y ~3 m at best at injectionRF power and longitudinal instability limitation in the SPS intensity perhaps achievable with a 3x slower ramp rate, tentatively on Q20Longitudinal emittance about 0.4 eVs at injection from simulations (J. Esteban-Mller)Beam quality possibly degraded due to e-cloud and longitudinal limitationsNeed to gain experience in the SPS with dedicated MDs in 2014 for complete parameter list at flat topLBOC, 8 April 20148b+4e scheme16Creates trains with 4 missing bunches every 8 bunches (H. Damerau, RLIUP)Allows for larger intensity per bunchIs expected to reduce e-cloud effectsProductionStd scheme Unbalance h = 7 21 triple split into a double split, leaving empty bucket bunch pattern 6x(8b+4e) + 8bBCMS merging and triple splitting suppressed bunch pattern 3x(8b+4e) + 8b

SimulationEkin = 2.5 GeV

SimulationEkin = 2.5 GeVLBOC, 8 April 2014

Standard schemeBCMS

8b+4e scheme17Limited to 1.8 x 1011 p/b in the SPS because of longitudinal instabilitiesBrightness limited byPSB brightness for standard schemeNo outstanding bottleneck for BCMSLBOC, 8 April 2014Standard schemeBCMS

8b+4e scheme18Limited to 1.8 x 1011 p/b in the SPS because of longitudinal instabilitiesBrightness limited byPSB brightness for standard schemeNo outstanding bottleneck for BCMSLBOC, 8 April 2014Standard schemeBCMS25 ns (8b+4e)Intensity (p/b)Emittance (mm)Bunch patternStandard1.8 x 10112.36x(8b+4e) + 8bBCMS1.8 x 10111.43x(8b+4e) + 8bSummaryLHC start upLHCPROBE and LHCINDIV with new production mechanism in the PSB for the bunch intensity controlLHC50 standard (first phase Scrubbing I)Up to 1.7 x 1011 p/b with ex,y=1.6 mmPossibly LHC25 standard (last phase Scrubbing I)Up to 1.3 x 1011 p/b with ex,y=2.4 mmPhysics and 25ns operationLHC50 (standard and BCMS) for first phase physics operationBCMS up to 1.7 x 1011 p/b with ex,y=1.1 mmLHC25 standard (first phase Scrubbing II)LHC25 doublet (last phase Scrubbing II)Up to 1.6 x 1011 p/doublet with ex,y>3.0 mmLHC25 BCMS for physics operationUp to 1.3 x 1011 p/b with ex,y=1.3 mm8b+4e as alternative if scrubbing is not enough to run with LHC25 BCMSUp to 1.8 x 1011 p/b with ex,y=2.3/1.4 mm (std/BCMS)LBOC, 8 April 201419Thank you for your attentionLBOC, 8 April 201420