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PS2 Beams for SPS

PS2 Beams for SPS. Michael Benedikt AB/OP. PS2 main parameters (protons). Injection energy via beam brightness: Reach twice brightness of the ultimate 25 ns LHC beam (20% reserve for losses): 4.0 10 11 per LHC bunch (inst. 1.7 10 11 ) within nominal transverse emittances

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PS2 Beams for SPS

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  1. PS2 Beams for SPS Michael Benedikt AB/OP SPSU WG

  2. PS2 main parameters (protons) • Injection energy via beam brightness: • Reach twice brightness of the ultimate 25 ns LHC beam (20% reserve for losses): 4.01011 per LHC bunch (inst. 1.71011) within nominal transverse emittances • Determines line density at injection incoherent SC tune spread. • MAXIMUM BRIGHTNESS FROM PS2 • 4 GeV injection energy (previously 3.5 GeV) • Machine length of 15/7 times the existing PS • ~ twice longer than PS because of higher ejection energy (50 GeV) • Needed to assure RF cogging with SPS for 40 MHz systems • h=180 (PS2 ejection) to h=924 (40 MHz) and 4620 (200 MHz) SPS • PS2 = 15/77 times the SPS • Slightly too short to fill the SPS completely with 5 turns. SPSU WG

  3. PS2 main parameters (protons) • PS2 RF systems (2 principal routes) • 40 MHz only h=180 (with SPL as injector with 40 MHz chopping). • Lattice parameters (esp. gt) play an important role for bunch shortening at ejection to fit SPS 200 MHz buckets • First simulations confirm that with installed 40 MHz (for acceleration) the bunches can be shortened sufficiently. • 10 MHz (h=15) as main systems • Additional 20, 40 MHz systems for splitting (cf. PS) each bunch in 12 LHC bunches (h=15 x 3 = 45 x 2 x 2 = h=180) • Apertures • Determined by high intensity fixed target beam • Scaling from high intensity PS beam at 1.4 GeV • Norm. sigma emittances 15/8 mm mrad (h/v) MAXIMUM FOR PS2 • Adiabatic emittance damping by (bg)1.4/ (bg)4.0 SPSU WG

  4. LHC beam from PS2 (i) • Nominal bunch train at extraction (independent of rf route) • h=180 (40 MHz) with bunch shortening to fit SPS 200 MHz. • 168 buckets filled leaving a kicker gap of ~ 300 ns (50 GeV!) • Achieved by 14 filled buckets on h=15 (10 MHz) and 12 splittings • Alternatively with painting in 40 MHz directly from SPL (would allow up to 170 bunches) • No big changes on LHC filling scheme (P.Collier) • Any other bunch train pattern down to 25 ns spacing • Straightforward with SPL 40 MHz chopping and 40 MHz system • Limited to present schemes (75 ns, 1, 12, bunches etc…) with 10 MHz system and “classical” splitting. SPSU WG

  5. LHC beam from PS2 (ii) • Beam parameters • Extraction energy: 50 GeV • Maximum bunch intensity: 4E11 / protons per LHC bunch (25 ns) • Bunch length rms: 1 ns (identical to PS) • Transverse emittances norm. rms: 3 microm (identical to PS) • Longitudinal emittance varying with intensity • Longitudinal aspects • Scale longit. emittance with sqrt of intensity e = e0 √(I/I0) • (for stability in SPS, Elena) • I max = 4E11 e max = 0.35 eVs*√(4/1.3) = 0.6 eVs • Momentum spread scales like emittance (bunch length = const.) • Scaling from nominal beam dp/p=2E-3 but @50 GeV dp/p=1E-3! • dp/p max = 1E-3*√3 = 1.8  no aperture issues • Voltage at PS2 extraction scales like intensity (emittance^2). • 3 times more voltage for shortening of the 4E11 bunch. SPSU WG

  6. SPS 23 micros SPS 23 micros PS2 = 15/7PS = 15/77 SPS 2/77 SPS non-filled because of geometry (0.6 micros) 5 gaps for LSS4 extraction kicker rise/fall (1 micros) CNGS beam from PS2 (i) • Filling the SPS with 5 turns from PS2 • “Bunch to bucket” transfer from PS2 40 MHz to SPS 200 MHz • Filling is achieved in a single PS2 pulse 17.4 out of 23 micros • Extraction kicker gap corr. to ~40 unfilled 40 MHz buckets. • Straightforward with SPL • 3 (36) or 4 (48) missing bunches at injection on h=15 i.e. 10 MHz • ~140 filled 40 MHz buckets in PS2 SPSU WG

  7. CNGS beam from PS2 (ii) • CNGS beam parameters at PS2 extraction • Extraction energy: 50 GeV • Extraction channel design foreseen to cover ~20 GeV to 50 GeV • Maximum intensity: ~8E11 protons per 40 MHz bucket • Line intensity reduced by factor 5 in SPS to <2E11 protons per 200 MHz bucket • Total intensity of ~1.2E14 per PS2 cycle • Transverse emittances: like upper limits of present CNGS beam • Norm. sigma emittances 15/8 mm mrad (h/v) • Adiabatic emittance damping by (bg)13/ (bg)50 = 0.27 • Therefore ~1/2 present beamsize due to emittance. • Transfer either with/without emittance exchange in TL. • Bunch length rms: 1 ns (identical to PS) • Required to fit SPS 200 MHz system  cf. to LHC case SPSU WG

  8. CNGS beam from PS2 (iii) • Longitudinal aspects • Scale longit. emittance compare to LHC case • Would require only 0.4 eVs from SPS (2E11/bucket) • This is most probably not sufficient in PS2 for stability • Maximum acceptable longit. emittance for FT in SPS? • If large emittance voltage requirements for shortening in PS2? • Resonant island extraction • 5-turn island extraction like planned for PS • Compatibility with bunch shortening  (Massimo, Steve) SPSU WG

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