to the highest luminosity and BEYOND Salim Ogur

to the highest luminosity and BEYOND Salim Ogur Tracking in 20 Ge. V Linac Acknowledgements: K. Oide, F. Zimmermann CERN February 2018

Outline 1. Introduction 2. Linac Designs 2. 1. Up to 1. 54 Ge. V (injection to the Damping Ring) 2. 2. From 1. 54 to 6 Ge. V (injection to Pre-booster) 2. 3. From 1. 54 to 20 Ge. V (injection to Booster Ring) 3. Conclusion 2 2

1. Introduction Cavities S-Band C-Band Frequency (MHz) 2855. 98 5711. 96 Length (m) 2. 97 1. 80 Cavity Mode 2π/3 Aperture Diameter (mm) 20 14 Unloaded Cavity Gradient (MV/m) 25 50 ❖ Linac will have a repetition of 200 Hz repetition with 2&4 Bunches per RF pulse. ❖ The S-Band wakefields of K. Yokoya are scaled for the C-Band cavities. The wakefields are increased by 10^3/7^3 in transverse, and 10^2/7^2 in longitudinal plane due to aperture size. 3

1. Introduction- Misalignments Element Simulated Error Injection Offset (h/v) 0. 1 mm Injection Momentum Offset (h/v) 0. 1 mrad Quadrupole Misalignment (h/v) 0. 1 mm Cavity BPM’s Misalignment (h/v) 30 μm ❖Field errors are ignored, because we can always perform Quad. BPM method in the linacs throughout operation. ❖ Space charge will be matter of low energy part for the electron acceleration, however since the damping ring is at 1. 54 Ge. V, even 100 times of emittance blow can be cured, thus this effect is negligible. 4

Misalignments & BPM σbpm=30 μm misalignment w. r. t. cavity Reference Line of the cavity cavities might be misaligned by σcavity=100 μm : = BPM Reference Line of the accelerator ➡ Cavities and the quadrupoles may be aligned within the precision of σ=100 μm; however, the cavity BPMs will have a relative error of σ=30 μm, as suggested by K. Oide. Actually, compare to the accelerator reference line, they are misaligned by σ<130 μm. 5

2. 1 Linac up to 1. 54 Ge. V ❖ An S- Band Linac has been simulated starting from an RF- Gun which provides a 2 E 10 particles* in a bunch at 12 Me. V with 0. 35/0. 5 μm of geometric emittance (i. e. 8/12 μm normalised). The initial beam is created with 1% energy spread and sigma_z=1 mm Gaussian randomly **. * normally we may need 1. 7 E 10 particles in a bunch, 2 E 10 is chosen for precompensation, and safety. ** Currently, waiting for the macroparticle beam from RF gun simulations. 6

2. 1 Linac up to 1. 54 Ge. V ❖ The fluctuations and dispersion with the automatic orbit steering. 7

2. 1 Linac up to 1. 54 Ge. V ❖ 1 M macroparticles are used. 8

2. 1 Linac up to 1. 54 Ge. V Some results for different seeds using 1 M macro-particles for Gaussian random beam are presented below (all misalignments + BPM errors are included): Trial ID Horizontal Emittance (nm) Vertical Emittance (nm) Transmission 1 6. 2 8. 4 100% 2 7. 7 4. 5 100% 3 3. 0 4. 0 100% 4 5. 6 3. 8 100% 5 15 5. 3 100% 6 6. 5 5. 7 100% 7 2. 9 6. 0 100% 8 5. 8 4. 0 100% 9 12 4. 2 100% 10 5. 3 5. 0 100% 11 4. 0 4. 2 100% 12 2. 8 5. 1 100% average 6. 4 5. 0 100% 11

Beam after Damping Ring + Bunch Compressor ❖We may cool the e- emittance at the DR, yet definitely cool e+, therefore we can’t avoid the bends… The emittance from the DR can be as low as 1. 2/0. 4 nm (h/v) ideally. However, the bends needed for re-entrance to the linac and the CSR are likely to dilute the emittance. T. Charles

Beam after Bunch Compressor T. Charles ❖This beam presented is the positron simulations of KEK up to 1. 1 Ge. V, then the emittance cooling at the Damping Ring for 45 ms, which is transferred via a transverse matching section, then the beam is injected back to the linac.

Beam after BC followed by BTL BCS Linac ❖ A Beam Transfer Line has been designed to match BC to Linac solely to proceed Linac simulations. Nonetheless, this matching had better done at the turnaround loops/BC as suggested by K. Oide.

Beam after BC followed by BTL ❖Tracking through BTL.

2. 2. Linac from 1. 54 to 6 Ge. V ❖ S-Band structures. 16

2. 2. Linac from 1. 54 to 6 Ge. V ❖ Beam profiles tracked through linac using the beam exiting BC&BTL 17

2. 2. Linac from 1. 54 to 6 Ge. V ❖ Beam profiles tracked through linac using the beam exiting BC&BTL 18

2. 2. Linac from 1. 54 to 6 Ge. V ❖ Beam profiles tracked through linac using the beam exiting BC&BTL 19

2. 2. Linac from 1. 54 to 6 Ge. V ❖ Results with misalignments plus BPM errors. Trial ID Horizontal Emittance (nm) Vertical Emittance (nm) Transmission 1 0. 55 0. 42 100% 2 1. 50 0. 16 100% 3 0. 95 0. 21 100% 4 1. 26 0. 33 100% 5 2. 16 0. 13 100% 6 0. 51 0. 17 100% 7 0. 61 0. 14 100% 8 2. 23 0. 57 100% 9 0. 53 0. 29 100% 10 0. 50 0. 14 100% 11 1. 28 0. 70 100% 12 0. 62 1. 81 100% Average emit. 
 at 6 Ge. V 1. 06 0. 42 100% Injected emit. at 1. 54 Ge. V 1. 86 0. 4 100% 20

2. 1 Linac from 1. 54 to 20 Ge. V ❖ S-Band structures finish at 6 Ge. V (QR 9 in the optics), then C-band structures start. ❖ Ideal design (typical drift space between cavities and magnets ~25 cm). 21

2. 1 Linac from 1. 54 to 20 Ge. V ❖ The fluctuations and dispersion with the automatic orbit steering. 22

2. 1 Linac from 1. 54 to 20 Ge. V ❖ The distance between correctors and preceding/proceeding elements have been increased (40 cm for steerers, 25 cm for cavities & quadrupoles), in order to diminish the effectiveness of the BPM misalignments. Entrance angle to the cavity due to BPM misalignment is proportional to. 29

2. 1 Linac from 1. 54 to 20 Ge. V ❖Tracking which results in an emittance of 3. 6/0. 2 nm and 90% transmission. 30

2. 1 Linac from 1. 54 to 20 Ge. V ❖ emittance=0. 87/0. 1 nm Transmission: 98. 6% 32

2. 1 Linac from 1. 54 to 20 Ge. V • Some results with all misalignments (including BPM’s) for different seeds using the e+ beam simulated through BC and BTL: Trial ID Horizontal Emittance (nm) Vertical Emittance (nm) Transmission 1 3. 6 0. 2 90% 2 5. 4 0. 4 95% 3 3. 7 0. 2 90% 4 4. 1 0. 1 91% 5 2. 8 0. 2 91% 6 4. 7 0. 5 94% 7 7. 0 0. 2 97% 8 3. 7 0. 1 91% 9 2. 8 0. 1 85% 10 0. 9 0. 1 99% 11 3. 2 0. 4 88% 12 5. 7 1. 0 95% AVERAGE at 20 Ge. V 4. 0 0. 3 92% Injected at 1. 9 0. 4 100% 33

3. Conclusions Linac Results S-Band up to 1. 54 Ge. V S-Band 1. 54 -> 6 Ge. V C-Band 6 -> 20 Ge. V Length (m) 79. 1 221. 9 557. 2† Transmission for 2 E 10 part. 100% 92% Number of Cavities 21 60 181 Number of Quadrupoles* 14 9 9 Injected Emittance (h/v) ** 0. 35/0. 5 μm 1. 9/0. 4 nm - Emit. with no blow 2. 7/3. 8 nm 0. 5/0. 1 nm 0. 15/0. 03 nm Avg. Extracted Emit. 6. 4/5. 0 nm 1. 1/0. 4 nm 4. 0/0. 3 nm † lengthy optimisation of individual spacing is to come. * excludes the quadrupoles for matching from/to other accelerators ** excludes the emittance dilution due the mis-injection! 34

3. Conclusions ❖The S-Band Linac 6 Ge. V linac has become 79. 1+221. 9= 301 m, resulting in 1. 1/0. 4 nm emittance on average with perfect transmission. ❖The C-Band part adds 557 m to the total length, therefore the 20 Ge. V linac is about 858 m for now, however, the current study is to shrink it to 750 meters. ❖The misalignment study has been performed for many different seeds, the interpretation is to conclude that this design can absorb misalignment and readout errors together with offsets in the injection. 35

3. Conclusions: Emittance Evolution Accelerator h/v emittance Status RF Gun: 0. 35/ 0. 50 μm Even smaller emittance is achieved ideally for 6. 5 n. C. We are safe, because we reduce the charge requirement to 3. 2 n. C. Linac at 1. 54 Ge. V tracking results for e- 6. 4/5. 0 nm Emittance blow. However, the DR can reduce it to 1. 8/0. 4 nm, easily. Linac at 1. 54 Ge. V provides e+ 1. 3/1. 2 μm 4 n. C simulations at 1. 1 Ge. V from KEK. We need less charge with similar emittance at 1. 54 Ge. V Damping Ring has an acceptance of 24/24 μm Safe. Enough acceptance for e+ and e- Damping Ring tracking for e+ results 1. 8/0. 4 nm Safe. That emit. at 1. 54 Ge. V is allowing 1 nm extraction at 6 Ge. V. Linac re-entrance at 1. 54 Ge. V 1. 9/0. 4 nm Beam Transfer Line needs to be done at BC. Linac at 20 Ge. V tracking results for e- 4. 0/0. 3 nm Average of 12 different seeds using 1 M macro particles. Pre-Booster Asks for Booster Ring Asks for 36