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vdM beam production in the injectors

vdM beam production in the injectors. H. Bartosik, G. Rumolo LBOC, 26. November 2013. Introduction. 2 options for producing such bunches (large transverse emittance wrt requested intensity …)

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vdM beam production in the injectors

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  1. vdM beam production in the injectors H. Bartosik, G. Rumolo LBOC, 26. November 2013

  2. Introduction • 2 options for producing such bunches (large transverse emittance wrt requested intensity …) • Low intensity INDIV bunch in the PSB with normalized emittance of about 1-2 μm and then blow-up downstream (mismatch at PS-SPS transfer, resonances in SPS, …) • Controlled generation of (relatively low intensity) bunch with already large transverse emittance at exit from PSB (avoid necessity of blow-up downstreams) • Option b) used in the end of 2012turned out to be easiest and most reproducible way, while transverse tails were obtained with option a) in the past (see vdM scans early 2012) LBOC, 26. November 2013

  3. Beam preparation in PSB and PS • PSB • Injection of 2.5 turns and loss of 92% of intensity through slow capture (“longitudinal shaving”)  longitudinal emittance around 0.25 eVs • Adjustment of intensity with vertical shavers (good reproducibility) less than Gaussian vertical tails !!! • PS • No specific manipulation apart from slight longitudinal emittance blow-up εy≈2.5μm (tails less populated than Gaussian) εx≈3μm LBOC, 26. November 2013

  4. Beam preparation in SPS • INDIV cycle in the SPS (flat bottom of 7.2 s to allow for 4 injections) • Small incoherent losses on flat bottom (large beam size) and capture losses • Final adjustments of intensity and transverse distribution with scrapers close to flat top  intensity around 0.9(±0.1)x1011p/b flat bottom capture losses scraping LBOC, 26. November 2013

  5. Resulting beam profiles at SPS extraction (1) • Looks pretty Gaussian on the SPS wire scanner • but hard to tell due to limited resolution and linear scale • tails were populated somewhere from PSB extraction to SPS flat top! LBOC, 26. November 2013

  6. Resulting beam profiles at SPS extraction (2) • Closer look on beam profiles in log-scale • Still slightly less than Gaussian tails (apart from the noise floor) in SPS • These bunches become almost perfectly Gaussian between SPS extraction and collision due to processes in the LHC (see presentation of W. Kozanecki, LBOC December 3rd2013) with emittances of 2.5-3μm LBOC, 26. November 2013

  7. Summary and Conclusions • Single bunches for van der Meer scans successfully produced in 2012 • Starting from bunches with large transverse emittance in the PSB (instead of intentional blow-up downstream as used in the past) • Optimized transverse beam distribution • Significantly less than Gaussian tails at exit from the PSB  diffusion and blow-up in PS and SPS • Slightly less than Gaussian tails at SPS extraction  almost perfect Gaussian distribution at LHC collision (during van der Meer scans) • Reached beam characteristics requested by LHC • Intensity around 0.9(±0.1)x1011p/b • emittances of 2.5-3μm • Gaussian profiles at collision in the LHC • Summary of beam production scheme in ATS note:CERN-ACC-NOTE-2013-0008 MD LBOC, 26. November 2013

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