PS 2 Beams for SPS Michael Benedikt ABOP
PS 2 Beams for SPS Michael Benedikt AB/OP 21/08/2007 SPSU WG 1
PS 2 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 PS 2 – 4 Ge. V injection energy (previously 3. 5 Ge. V) • Machine length of 15/7 times the existing PS – ~ twice longer than PS because of higher ejection energy (50 Ge. V) – Needed to assure RF cogging with SPS for 40 MHz systems • h=180 (PS 2 ejection) to h=924 (40 MHz) and 4620 (200 MHz) SPS – PS 2 = 15/77 times the SPS • Slightly too short to fill the SPS completely with 5 turns. 21/08/2007 SPSU WG 2
PS 2 main parameters (protons) • PS 2 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 = h=180) • Apertures – Determined by high intensity fixed target beam • Scaling from high intensity PS beam at 1. 4 Ge. V • Norm. sigma emittances 15/8 mm mrad (h/v) MAXIMUM FOR PS 2 • Adiabatic emittance damping by (bg)1. 4/ (bg)4. 0 21/08/2007 SPSU WG 3
LHC beam from PS 2 (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 Ge. V!) • 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. 21/08/2007 SPSU WG 4
LHC beam from PS 2 (ii) • Beam parameters – – – Extraction energy: 50 Ge. V Maximum bunch intensity: 4 E 11 / 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 = e 0 √(I/I 0) • (for stability in SPS, Elena) • I max = 4 E 11 e max = 0. 35 e. Vs*√(4/1. 3) = 0. 6 e. Vs – Momentum spread scales like emittance (bunch length = const. ) • Scaling from nominal beam dp/p=2 E-3 but @50 Ge. V dp/p=1 E-3! • dp/p max = 1 E-3*√ 3 = 1. 8 no aperture issues – Voltage at PS 2 extraction scales like intensity (emittance^2). • 3 times more voltage for shortening of the 4 E 11 bunch. 21/08/2007 SPSU WG 5
CNGS beam from PS 2 (i) • Filling the SPS with 5 turns from PS 2 – “Bunch to bucket” transfer from PS 2 40 MHz to SPS 200 MHz PS 2 = 15/7 PS = 15/77 SPS 23 micros 2/77 SPS non-filled because of geometry (0. 6 micros) SPS 23 micros 5 gaps for LSS 4 extraction kicker rise/fall (1 micros) – Filling is achieved in a single PS 2 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 PS 2 21/08/2007 SPSU WG 6
CNGS beam from PS 2 (ii) • CNGS beam parameters at PS 2 extraction – Extraction energy: 50 Ge. V • Extraction channel design foreseen to cover ~20 Ge. V to 50 Ge. V – Maximum intensity: ~8 E 11 protons per 40 MHz bucket • Line intensity reduced by factor 5 in SPS to <2 E 11 protons per 200 MHz bucket • Total intensity of ~1. 2 E 14 per PS 2 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 21/08/2007 SPSU WG 7
CNGS beam from PS 2 (iii) • Longitudinal aspects – Scale longit. emittance compare to LHC case • Would require only 0. 4 e. Vs from SPS (2 E 11/bucket) • This is most probably not sufficient in PS 2 for stability – Maximum acceptable longit. emittance for FT in SPS? – If large emittance voltage requirements for shortening in PS 2? • Resonant island extraction – 5 -turn island extraction like planned for PS – Compatibility with bunch shortening (Massimo, Steve) 21/08/2007 SPSU WG 8
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