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Painting, injection matching, emittances and beam dynamics

Painting, injection matching, emittances and beam dynamics. C. Bracco, C. Carli, L. M. Coralejo Feliciano, L. Ducimetiere, T. Fowler, B. Goddard, G. Grawer, J-B. Lallement, B. Mikulec, M. Scholz, W. Weterings. Outlines.

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Painting, injection matching, emittances and beam dynamics

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  1. Painting, injection matching, emittances and beam dynamics C. Bracco, C. Carli, L. M. Coralejo Feliciano, L. Ducimetiere, T. Fowler, B. Goddard, G. Grawer, J-B. Lallement, B. Mikulec, M. Scholz, W. Weterings

  2. Outlines • H- charge exchange injection: principle and layout (chicane + stripping foil) • Injection painting in phase space • Longitudinal • Transversal (horizontal plane, KSW magnets) • Studies for HW specifications • Vertical Plane • Conclusions

  3. H- Injection • Beam injected in with 66mrad angle w.r.t. PSB axis • Strength of BS chicane magnets maximum during injection  45.9 mm orbit bump • Chicane decays after Injection • Edge focusing effects at the pole faces  Strong vertical β-beating • Solutions : • Passive compensation: pole face rotation • Active compensation: additional trim quadrupoles (5 ms chicane decay)  more flexible, better compensation & lower losses (<5%)

  4. Longitudinal painting • Attenuation of space charge effects can be obtained by controlling the distribution, in phase space of injected particles • Energy of the injected beam will be varied to fill the bucket with an equal density distribution. ±1.1 MeV energy distribution over a period of 40 turns

  5. Transverse Painting Scheme Injected Beam Xoff (t1) Xoff,max Horizontal painting bump implemented Fill first the centre and then the outer area of the ellipse in the transverse phase space Decay time modulation of four kicker magnets (KSW), installed in the PSB lattice, allow to accomplish transverse phase space painting to required emittance. Maximum height of the bump, at injection, depends on the beam and injection parameters

  6. Effect of Stripping Foil on Emittance End of injection! Beam injected over 40 turns (LHC beam) Particle distribution generated for a horizontal position of -35mm (0 offset applied), matched in dispersion (Dx = -1.4 m) Bump height is kept fixed at -35mm over 100 turns Circulating beam passes through the stripping foil at each turn Horizontal emittance increases linearly after injection is finished  a factor of 2 increase after 100 turns Need for horizontal painting to move beam off foil!

  7. Different Beams Required by Users Multi-turn injection KSW modulations and different number of turns to reach target emittances with uniform particle distribution.

  8. ORBIT Simulations • Simulations were performed with the particle tracking code ORBIT • H- charge exchange, space charge effects, apertures and accelerations are included • A routine, implemented in ORBIT, allows to simulate the painting bump (KSW thin lens approximation) • Initial 6D distribution generated with a “Mathematica” notebook – longitudinal painting is included (500 000 macroparticles) • Initial lattice generated with MAD8 • Lattice stays unchanged during injection • After injection, lattice has to be reloaded at each turn to simulate chicane fall

  9. Multi-Linear Decay Waveform for KSW KSW Strength t1 tfall t2 Time [us] Imax I1 I2 • Imax: current corresponding to 35 mm orbit • Faster decay to I1 until t1 followed by an almost constant slope until t2  more uniform charge distribution: lower density in the core • Fast decay to 0 current to move the beam away from the stripping foil (maximum achievable gradient Imax  I0 = 15 ms)

  10. Waveform Parameters for PSB Users • Up to nominal LINAC 4 pulse (1×1014ppp, 4×10-4 s) • > 40 turns injection (RF) • Matched dispersion Dx = -1.4 m Constant fall time: 15 ms (can be as fast as allowed by the hardware) Imax Vertical offset (steering magnets in TL, see C. Carli’s talk) See L.M. Coralejo Feliciano’s talk

  11. Waveform Parameters for PSB Users • Assuming 8.13×1010 p+/turn (LHC beam type for all users) • Matched dispersion Dx = -1.4 m • Assuming 8.13×1010 p+/turn (LHC beam type for all users) • Mis-matched dispersion Dx = 0 m Dx = 0  smaller foil size  smaller number of p+ hits Pulse length of BI.DIS > 100 ms !!

  12. Normalized Horizontal Emittance • 8.13×1010 p+/turn (LHC beam type for all users) Review on PSB 160 MeV H- Injection

  13. Normalized Vertical Emittance • 8.13×1010 p+/turn (LHC beam type for all users) Review on PSB 160 MeV H- Injection

  14. Charge Distribution in Space • 8.13×1010 p+/turn (LHC beam type for all users) NORM Review on PSB 160 MeV H- Injection

  15. Intensity: p+ injected per Turn TOF NORM • Injection of a reduced intensity over a bigger number of turns: • allows to have a more uniform particle distribution  smaller space charge effect • Increases the number of foil hits per p+ by a factor ~3  is foil heating a problem? Review on PSB 160 MeV H- Injection

  16. Betatron Mismatch in Vertical Plane Twiss parameters @ PSB injection point Twiss parameters @ end of TL Mismatch factor Final Emittance

  17. Pure Betatron Mismatch Theoretical curve Simulations results * • PSB injection point: by=3.7m, ay=0 • End of TL: eyt = 0.8 mm*mrad, ayt=0.04 Review on PSB 160 MeV H- Injection

  18. Pure Betatron Mismatch Theoretical curve Simulations results * Highly peaked distribution  to be combined with offset • PSB injection point: by=3.7m, ay=0 • End of TL: eyt = 0.8 mm*mrad, , ayt=0.04 Review on PSB 160 MeV H- Injection

  19. Vertical Painting ? 3 existing PSB kickers 1 new kicker (3 m downstream of KSW.2L1) Foil 10 mm bump at the stripping foil Other option: Fast Kicker in the injection line ?

  20. Conclusions • A new injection system implemented for injection into PSB from LINAC4 • Longitudinal painting: RF limitations minimum number of injection turns = 40 • Transverse horizontal painting needed for uniform distribution and to move the beam off the stripping foil  reduce emittance blowup and foil heating • KSW multi-linear waveforms defined for all users and different conditions: dispersion, number of protons injected per turn  HW specifications • A lower injection intensity allows a more uniform particle distribution but increases the number of foil hits per p+ and requires a longer BI.DIS pulse • Vertical plane: • offset via steering magnet in TL  target emittances and uniform distributions • Betatron mismatch  target emittances but peaked distribution (combined with offset?) • Painting in vertical plain would require new hardware (either in the PSB or in the TL), up to now it doesn’t seem necessary • Performance for very small emittance LHC beams, in the light of 2011 LHC operation, has still to be evaluated Review on PSB 160 MeV H- Injection

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