SABER Optics. Y. Nosochkov, K. Bane, P. Emma, R. Erickson. SABER Workshop, SLAC, March 15-16, /25

Transcription

1 SABER Optics Y. Nosochkov, K. Bane, P. Emma, R. Erickson SABER Workshop, SLAC, March 15-16, /25

2 Outline White paper optics design Beam tracking for SABER and for the old South Arc Magnet overlap in the BSY and solution Field and alignment sensitivities Linac Layout new for SABER with low-β IP 2/25

3 Sector 20 Horizontal layout Linac X (m) Bypass Vertical layout Bypass to South arc Z (m) Y (m) Z (m) 3/25

4 rotated bends 1st dog-leg - horizontal layout Linac X (m) cm 18.4 mrad Bypass m Z (m) Vertical layout Y (m) 7.8 mrad 4.75 cm Bypass m Linac Z (m) 4/25

5 2nd dog-leg - horizontal layout Linac 50B1 X (m) 40.1 mrad South arc Bypass 51B2 (2) rotated bends Z (m) Vertical layout Y (m) Linac 21.9 mrad Bypass 50B1 White paper version Magnet x-y size may not be right Magnet overlap discussed later Z (m) 5/25

6 Beta and Dispersion from Bypass to IP β 1/ 2 (m 1/ 2 ) sec dogleg 1 45 o /cell straight (ε diagnostic?) South arc with bypass. Unix version 8.51/15 16/10/ βx 1/ 2 βy 1/ 2 Dx Dy dogleg 2 nπ arc final focus IP β x = 1 cm β y = 10 cm D(m) s (m) δ E/ p0c = 0. Table name = TWISS R 56 = 27.0 mm, T 566 = 77.2 mm (with sextupoles) 6/25

7 Low Beta Final Focus Required at IP: σ xy < 10 µm, η = 0, η = 0. IP design: 6 quads for β x / β y = 1 / 10 cm, η = 0, η = 0, L* = 2 m. At 30 GeV and γε x / γε y = 50 / 5 µm (β x ε x ) 1/2 =(β y ε y ) 1/2 = 2.9 / 2.9 µm. But errors and energy spread will increase the size. IP is at z = m from the old straight center, and 13.7 m from the next arc. 2 South arc achromats final focus IP South arc and Final Focus. β 1/ 2 (m 1/ 2 ) Unix version 8.51/15 16/10/ βx 1/ 2 β y 1/ 2 Dx Dy D(m) (w/o local D y correction) s (m) 7/25

8 Sextupoles for Chromaticity Correction 8 sextupoles are included to compensate beam size growth due to the large energy spread. Since there is no dispersion in the FF, the sextupoles are placed in the bypass dog-legs. The sextupoles minimize the 2nd order dispersion and W-functions (dβ/dδ). 2 sextupoles in the 1st dog-leg 5 sextupoles in the 2nd dog-leg and 1 in arc matching section β (m) st dogleg of bypass. Unix version 8.51/15 16/10/ β x βy Dx Dy D(m) β (m) nd dogleg of bypass. Unix version 8.51/15 16/10/ β x βy Dy Dx D(m) s (m) δ E/ p0c = 0. Table name = TWISS s (m) δ E/ p0c = 0. Table name = TWISS 8/25

9 2nd Order Dispersion and W-functions Without sextupoles With sextupoles dd/ dδ (m) nd order dispersion without sextupoles. Unix version 8.51/15 16/10/ Dx Dy dd/ dδ (m) nd order dispersion with sextupoles. Unix version 8.51/15 16/10/ Dx Dy T 566 = 225 mm s (m) δ E/ p0c = 0. Table name = TWISS 2nd order dispersion T 566 = 77 mm s (m) δ E/ p0c = 0. Table name = TWISS 2nd order dispersion W W-function without sextupoles. Unix version 8.51/15 16/10/ Wx Wy W W-function with sextupoles. Unix version 8.51/15 16/10/ Wx Wy nπ s (m) δ E/ p0c = 0. Table name = TWISS W-function s (m) δ E/ p0c = 0. Table name = TWISS W-function 9/25

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11 Initial Beam Z and E/E at Entrance to the Bypass Beam case 1: short bunch length, but large E/E E = 28.5 GeV, σ E =1.08%, σ z = 406 µm, N = 2.13x10 10 σ E / E =1.082% (fwhm=3.284) E = GeV, N e = z =0.153 mm 2 2 ~4.5% E/ E /% 1 0 E/ E /% n/ z /mm Source: gaussian random σ z =0.337 mm (fwhm=0.882, fit=0.406) I pk =1.127 ka V ind /MV I /ka z /mm z /mm GUI: saber: sarc with bypass; Yuri s correction of T566, Paul s overcompress; output particles 30 SEP :56:45; [ ] 11 / 25

12 X-Y Tracking from Bypass to IP, γε x(y) = 50(5) µm, no errors 100 Y (um) vs X (um) at IP in South Arc with bypass (v.3) - full beam beam u 1:3 50 Y (um) vs X (um) at IP in South Arc with bypass (v.3) - beam core beam u 1: Y (µm) Y (µm) Full beam at IP X (µm) Beam core size within specification < 10 µm Beam core at IP X (µm) σ x = 5.2 µm (gauss fit) σ y = 5.4 µm (gauss fit) blue - data red - gauss fit 12 / 25

13 X and Y vs. E/E at IP Good chromatic correction for E/E < 1.5%. Without sextupoles, there would be a significant beam size growth and beam loss E/E (%) de/e (%) vs X (um) at IP in South Arc with bypass (v.3) beam u 1: E/E (%) de/e (%) vs Y (um) at IP in South Arc with bypass (v.3) beam u 3: X (µm) Y (µm) / 25

14 Z and E/E at IP Gaussian fit σ z = 25.8 mm (86 fs) de/e (%) vs Z (um) at IP in South Arc with bypass (v.3) beam u 5:6 E/E (%) Z (µm) σ z = 25.8 µm (gauss fit) blue - data red - gauss fit 14 / 25

15 Beam case 2: reduced E/E, but longer bunch length No errors, 28.5 GeV, γε x(y) = 50(5) µm, N = 2.13x10 10 σ x = 4.4 µm (gauss fit) σ y = 4.3 µm (gauss fit) σ z = 32.6 µm (gauss fit) 15 / 25

16 South Arc Phase 1: with chicane, but w/o bypass and low beta Tracking from 50B1 to the Old IP with β* = 11.2 m σ x = 114 µm (gauss fit) σ y = 32.6 µm (gauss fit) σ z = 16.4 µm (gauss fit) 16 / 25

17 Magnet Overlap in the Bypass 2nd Dog-Leg White paper version Linac 50B1 Horizontal overlap of LER B3 and bypass QDB2 X (m) B3 Solution: move QDB2 0.8 m upstream Bypass LER line Z (m) Y (m) Bypass B3 50B1 LER line Vertical overlap of linac 50B1 and bypass QFB3 Solution: move QFB m upstream Z (m) 17 / 25

18 Modified Bypass 2nd Dog-Leg without Overlap Linac 50B1 More checking is needed in this region. X (m) Bypass B3 LER line Z (m) Optics is re-optimized. Some magnet strengths increased. R 56 = mm T 566 = mm Bypass 50B1 Y (m) B3 LER line Z (m) 18 / 25

19 Tracking in the Modified Lattice Beam case 1: 28.5 GeV, γε x(y) = 50(5) µm, N = 2.13x10 10 σ x = 5.1 µm (gauss fit) σ y = 5.3 µm (gauss fit) σ z = 25.5 µm (gauss fit) 19 / 25

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25 Further Optics Action Items Resolve any remaining magnet overlaps with other beamlines. Research the available SLAC magnets for use in SABER and include in optics. Tracking with realistic errors and correction systems. More tolerance studies. Correction systems for IP tune-up. Dump line. Experimental space requirements. 25 / 25