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Dynamic Dispersion for Main Injector Collimation

Dynamic Dispersion for Main Injector Collimation. Dave Johnson Review of MI Collimation Concepts June 30, 2006. Dynamic Dispersion for MI Collimation. Motivation Concepts Current lattice Proposed lattice changes Impact on ECOOL Impact on RR transfers in SNuMI Era Summary.

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Dynamic Dispersion for Main Injector Collimation

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  1. Dynamic Dispersion for Main Injector Collimation Dave Johnson Review of MI Collimation Concepts June 30, 2006 DEJ Beams-doc 2315

  2. Dynamic Dispersion for MI Collimation • Motivation • Concepts • Current lattice • Proposed lattice changes • Impact on ECOOL • Impact on RR transfers in SNuMI Era • Summary DEJ Beams-doc 2315

  3. Motivation for Lattice change • Although much progress has been made on increasing the efficiency of the slip stacking process and in the reduction of the Booster longitudinal emittance, we frequently have significant beam loss activating the tunnel. The situation only gets worse with slip-stacking for NuMI. • Beam intensity increase from 8E12/cycle to 5.5E13/cycle with NuMI slip-stacking (5E12 x 11 batches every 2.2 sec). • We need to provide a well shielded absorber to put all the beam that is not re-captured to main RF bucket. Est of 5 to 15% of injected beam (up to 5E12/cycle i.e. 10% of 5E13) • Momentum collimation system-> implies the need for dispersion • No room in arc’s for absorbers • Room in straight sections, but dispersion is zero • Need symmetric straight for dispersion un-suppression • MI10,MI40, and MI60 are not available but MI30 (or at least part of) is available. What does it take ? •  Digress a minuet on losses (2 slides) DEJ Beams-doc 2315

  4. Injection/Acceleration Efficiency M:TOR109/I:14SUM3 Nov 05 – Mar 06 90% 8E12 • > Measure of Beam on Target/Beam at • end of 8 Gev line (i.e TOR852) • Assume relative calibration of toroid good to about 5% • > Before shutdown slip-stack ~6-8E12 at • efficiency of 85 to 90% on average. • > After shutdown slip-stack ~5-6E12 at • efficiency of ~ 87% on average • > After shutdown NuMI ran 1.2E13ish at • efficiency of ~ 97 to 98% E:TOR101/I:19SUM3 June 06 DEJ Beams-doc 2315

  5. Beam loss looking at BEL • Plot showing TOR852 (cyan), 14SUM3 (red), BEAM (blue), and the response of BEL (green). • Try to keep loss to 1 kJ • BEL does not include DC beam kicked into 104 and hence would report a lower loss • Need to quantify differences between efficiency looking at toroids and BEL. 1.8kJ/1.6E-19/8GeV/7.5E12 ~ 18% Transition loss Loss of un-captured beam at start of ramp Loss due to the fuzzing of beam captured in wrong buckets AND chromatic lifetime DEJ Beams-doc 2315

  6. Concept part 1 ramp • Horizontal position of a particle in a region of dispersion • Locate an absorber (fixed large shielded mass) in dispersive region at a large offset • Utilize corrector time/energy bump to move beam close to absorber to produce absolute aperture restriction for large amplitude particles-then move away from absorber for remainder of cycle (reduce risk of hitting absorber with 120 GeV beam) • Take advantage of large step size from D*dp/dt • MI30 straight section has room in lattice for absorber (and secondary masks) so create a symmetric dispersion insert to produce the desired dispersion. (could be DC or ramped) Un-captured beam Motion of captured beam Closed orbit un DEJ Beams-doc 2315

  7. Slow loss Fast loss Slow loss 5E11 MI Ramp Start of ramp Integrated LM634 Concept part 2 • Slow beam loss from start of ramp till dp/p ~ .018 • Fast beam loss for dp/p > .018 till ~.04 (E < 9.3 GeV) • Another slow loss above 9.3 Gev (chromatic effects?) • Fast loss last about 30 ms (~2,700 turns). • Time and duration of loss depends on closed orbit, proximity to aperture and momentum spread of un-captured beam. • Rapid momentum change lends itself to large step size on a turn by turn basis (as compared to halo formation in Colliders) DEJ Beams-doc 2315

  8. Concept 3 Measured MI momentum aperture Position change per turn • Momentum aperture & vertical tune for un-captured beam can generate beam loss for larger chromaticities -> want to collimate before reaching dp/p where Qy approaches ½ integer • With current MI ramp dx/dt at D=2m when dp/p < .005 is ~10um/turn at dp/p ~.01 dx/dt ~16-18 um/turn • Compare with Halo collimation in Colliders where difusion rate is ~ 1-2 um/sec ! At dp/p .002 dx ~ 20 mm DEJ Beams-doc 2315

  9. Current Main Injector lattice • Generate toy lattice with ideal quad lengths and no multipoles • Compare geometry, lattice function and dispersion to full blown lattice - good agreement • Tunes H 26.425/ V 25.415 c d d d c c d d d c MI-30 DEJ Beams-doc 2315

  10. Proposed Lattice changes • The basic idea is to create a region of dispersion in a otherwise dispersion free region where there is room for collimator absorbers. To be done in MI30 ! • How ? Symmetrically power the trim coils in the IQC and IQD quads of the dispersion suppressors on either side of the MI30 straight section • Add trim quads in the MI30 straight section and power them symmetrically around Q305 • This solution introduces a tune shift which must be compensated by main QF and QD quad bus • The trim coils in IQC and IQD in remainder of ring are adjusted to minimize lattice function distortion. • Use MAD to generate insert, match to existing ring lattice and adjust ring tune. • Next 8 slides show solutions from current to finalsolution DEJ Beams-doc 2315

  11. Current Lattice -- Ring Dispersion • Proton direction • MAD uses RHR • +X to ring inside • B fix,D<0,p<p0,dx>0 (inside) • Dispersion suppressors • not matched between • arc and SS (in dispersion • or beta) • The next seven slides will • show the dispersion ramp • from its current level to • where it is -2.2 m at Q302 • and Q308 MI-30 DEJ Beams-doc 2315

  12. DEJ Beams doc 2315, June 30,2006 Ramping Dispersion -0.2 m DEJ Beams-doc 2315

  13. Ramping Dispersion -0.4 m DEJ Beams-doc 2315

  14. Ramping Dispersion -0.6 m DEJ Beams-doc 2315

  15. Ramping Dispersion -1.0 m DEJ Beams-doc 2315

  16. Ramping Dispersion -1.2 m DEJ Beams-doc 2315

  17. Ramping Dispersion -1.6 m DEJ Beams-doc 2315

  18. Ramping Dispersion -2.2 m DEJ Beams-doc 2315

  19. Dispersion in MI30 for -2.2m Solution • Close up view of MI30 dispersion • Note the zero dispersion at 22 and 32 • Note symmetric solution • Dp/p <0 move radial in • Particles with dp/p >0 move radial out (collimate high momentum at 308?) Q308 Q302 DEJ Beams-doc 2315

  20. Lattice functions of Current MI • Proton direction • Lattice with ideal quad length • Vertical beta wave measured • in machine • The next seven slides will • show the beta fctn while • ramping the dispersion to • where it is -2.2 m at Q302 • and Q308 DEJ Beams-doc 2315

  21. Lattice with Dispersion -0.2 m DEJ Beams-doc 2315

  22. Lattice with Dispersion -0.4 m DEJ Beams-doc 2315

  23. Lattice with Dispersion -0.6 m DEJ Beams-doc 2315

  24. Lattice with Dispersion -1.0 m DEJ Beams-doc 2315

  25. Lattice with Dispersion -1.2 m DEJ Beams-doc 2315

  26. Lattice with Dispersion -1.6 m DEJ Beams-doc 2315

  27. Lattice with Dispersion -2.2 m DEJ Beams-doc 2315

  28. Procedure for creating insert • Create Dispersion Insert • Beam line between 228 and 314 • Constrain Dx,D’x at 302 and 308 • Match b and D (and their derivatives in both planes) at 314 cell bndry to existing ring lattice functions. • Constrain max b between 228 &314 • Vary 5 trim coils & 4 trim quads • Generates insert & phase shift • Compensate phase shift & maintain match to ring • Use Main quad bus & trim coils in each dispersion suppressor in 4 circuits IQC(F&D) and IQD(F&D) • Re-tune machine to desired tune • Use main quad circuits QF & QD DEJ Beams-doc 2315

  29. Power Supply settings DEJ Beams-doc 2315

  30. Trim Coil and Trim Quad Currents DEJ Beams-doc 2315

  31. WAG for circuit implementation Trim Coil Count DEJ Beams-doc 2315

  32. V301 V303 ECOOL K H304 H302 H308 Q305 Potential MI30 layout • Utilize combination of fixed absorbers and masks • Install Vertical absorber ds Q303 • Install Horizontal absorber ds Q302 • Replace Q302 and Q303 with IQE or WQB • Move QXR quad at Q302 to Q306 • Future potential RR->MI transfer line devices (in red) • Could utilize kicker at Q301 to remove beam in kicker gap Kicker 309 Vertical collimator/absorber Lam 308 Horizontal collimator/absorber Secondary mask (outside beam pipe) DEJ Beams-doc 2315

  33. Concept on fixed absorber • Both cross sections are shown on single plot • Vertical (red) has W jaw on top • Horizontal (magenta) has W jaw radial inside • Absorber jaw tapered to improve impact parameter • Absorber on MI like stands and surveyed into position (reduce cost and complexity of absorber) beam Top view (tapered end) Corrector moves beam to be collimated Cross section DEJ Beams-doc 2315

  34. Compatibility with MI-RR Pbar Transfers • Beam centroid on pbar transfers to RR is about 10 mm at 302 and 16mm at 230. • Absorber edge at offset > 25mm • Use correctors to move beam close as necessary to absorber to maximize impact parameter DEJ Beams-doc 2315

  35. Impact on ECOOL • Want to minimize prompt radiation in the ECOOL region. • Design of a mask (steel outside the beam pipe in a region of loss) for Q301 has been done (by Nikolai using MARS) for a loss rate of 3E9 p/s at a grazing angle. Single mask reduce prompt dose at ECOOL by factor 15 over no mask. (e-mail 9/2/05). Addition of second mask at 305 reduced rate by another factor of 5. • With the absorber at 302 and 303 and masks at 304 and 305. We should be able to keep all activation within this region. This needs verification ! DEJ Beams-doc 2315

  36. e 25p sH ~5mm sV ~3mm sp/p ~4E-4 & D 2m -> .8mm HKICK at MRK232 RR VLAM 309 308 306 RR-30 straight section 302 304 K K VUP1 VDN2 MI-30 straight section 309 308 306 304 302 K K MI VLAM Rolled Impact on RR transfers in SNuMi Era • Use WQB at Q308 • Offset Lambertson septa by ~15-20 mm • Inject with zero dispersion, capture then ramp the dispersion insert (dynamic) in ~ 20-40 ms • Minimal impact on transfer line design • DC insert -> larger impact DEJ Beams-doc 2315

  37. Summary • It has been shown that a dynamic dispersion insert to generate 2.2m of dispersion in the MI30 straight is feasible with minimal impact on lattice or dispersion in the remainder of the ring. • A single fixed absorber concept is utilized due to large particle step size (does not require 2 stage collimation) • A Potential layout and MI30 modifications is outlined • Impact on ECOOL and SNuMI Era transfer line looks to be minimal • WAG cost est. for power supplies was presented • Other concepts for matching should be investigated such as phase trombone in MI60. DEJ Beams-doc 2315

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