1. Summary of Working Group 3: Rings Ioanis Kourbanis and Valeri Lebedev PIP-II Collaboration Meeting 9-10 November 2015

2. Working Group 3 Talks Talks are separated into 3 groups –Booster – 6 talks –MI & Recycler - 5 Talks –Controls – 1 talk V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings2

3. Booster Talks V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings3

4. Linac-to-Booster Transfer Line (A. Vivoli) Two optics choices were considered –No vertical elevation Crosses Tevatron tunnel Simple optics, most of quads in a single family No vertical dispersion Effect on operations? –Vertical separation with Tevatron tunnel Independent enclosures (+) but still no access to the Tevatron line if linac operates Same dipoles are rolled for vertical transfer Vertical dispersion, most of quads in two quad families V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings4

5. Linac-to-Booster Transfer Line (A. Vivoli) - 2 Optics is build –For transport Linac-to-Booster –For transport to the beam dump –For transport to Mu2e It includes fast switches (kickers and septa) for beam redirection to different destinations V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings5

6. Booster Injection (D. Johnson) Injection will be on 6 m straight line is barely sufficient for 800 MeV injection (initially was built for 200 MeV) Injection in the vertical plane reduces required bending angles Radiation protection is a challenging problem –Energy - 2 times higher, 1.5*1.33 – intensity, radiation - more than an order of magnitude –Beam damp requires additional space V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings6 Assume 2% H- and 0.2%H 0 Absorber 5x5x30 cm tungsten surrounded by 15 cm steel Up/downstream magnets 10 cm marble on top and aisle Residual activation on GMAG flange -> 10 R/hr Absorbed dose ~ 4 MGy/yr

7. Booster Injection (D. Johnson) - 2 2 choices –Inside present 6 m line –With new 4 shorter gradient dipoles More detailed design work is required to make the final choice V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings7

8. High Intensity Booster Operations (W. Pellico) V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings8 Booster has three loss points during the cycle: Injection/start of acceleration Largest fraction of loss 400 to 800 MeV Several components Transition RF voltage issue (soon done) Orbit control Space charge (often stated?) Extraction Limited aperture Kicker rise time RF manipulations

9. High Intensity Booster Operations (W. Pellico) - 2 Many recent and future improvements Immense progress has been made in recent years Flux has gone up by 10X Uncontrolled losses have been greatly reduced Efficiency is up – activation has been reduced even at higher pph The goal is to now double the flux but not increase the activation (remain at 2012 levels) 1.Increase beam cycle repetition rate to 15 Hz – first step done 2.Maintain uptime >85% - time will tell but many items addressed 3.Reduce losses by another 50% - lots of ideas and plans V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings9

10. Booster RF Cavity Replacement (T. Kroc) Why? –While the existing cavities have been refurbished, they are still 40 years old. –PIP II operations will leave no extra operating margin. –Uncertain operational impact of needing to run all cavities at maximum performance 24/7. How much? –Present operating range depending upon beam requirements and cavity repair status: 830 kV – 950 kV. < 850 kV, losses increase for 4.2E12/pulse. –1.2 MV ( 1.1 MV total + 0.1 MV overhead ) requires a minimum of 22cavities at the nominal voltage 55 kV (present 50 kV) This task of the PIP project is replacement of cavities only –Other RF hardware was already recently upgraded for PIP V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings10

11. Booster RF Cavity Replacement (T. Kroc) - 2 Beam parameters for PIP-II are set Cavity specs are complete and can be applied to either: –Parallel bias cavity or –Perpendicular bias cavity Major cavity specs are compatible with PIP-III/RCS Detailed specs will determine whether cavities can be used Work ramping up in FY16 with plans to test prototype in FY17 V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings11

12. Booster modification for 20 Hz operation (K. Seiya) Resonance circuit modifications –Reduced value of resonance circuit capacitor –increase voltage power dissipation at 20 Hz V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings12

13. Booster modification for 20 Hz operation (K. Seiya) - 2 Developing new GMPS regulator for present 15 Hz operation –Expect ±0.02% at injection –It should work for 20Hz New (magnetic) cogging system is operational –Further improvements are planned –Current system should work for 20Hz V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings13

14. Booster collimation system: status and future (V. Kapin) Transition from single stage to the two-stage collimation is planed –It is supported by new cogging which does not result in orbit changes required by present cogging –Old tests demonstrated its efficiency Numerical simulations show that the effective thickness of primary collimators need to be reduced (Cu -> Al, same thickness) New scheme where primary collimator is replaced by electrostatic septum is considered –It is expected to result further reduction of ring irradiation –Major fraction of loss will be hidden inside the collimation system V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings14

15. Booster collimation system: status and future (V. Kapin) - 2 V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings15

16. MI and Recycler Talks V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings16

17. MI/RR Accelerator Issues Can we slip stack and accelerate 50% more intensity. –Power loss from slip stacking (8 GeV) –RF Power (Acceleration) Running Recycler 53 MHz Cavities CW (Running at 60 GeV) Transition crossing Beam Stability Beam loss control/mitigation during slip stacking. V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings17

18. MI RF Power Upgrade (J. Reid) V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings18 Use two PA’s per cavity in a push pull configuration. We will need to double the modulators and the SS drivers. We have all the parts needed to test this option on the spare MI cavity.

19. MI RF Power Upgrade (Option 2) V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings19 Use new power amplifier (Eimac 4CW250000B) Size constraints need to be evaluated (much longer tube). Will need a new modulator. Can be used for the 2+ MW MI operations. Should purchase one tube for evaluation.

20. New RR RF cavities (J. Dey) V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings20 Use the cavity design developed for MI in collaboration with SLAC. Optimize the design for single frequency and lower voltage. Investigate different cooling options for tuner.

21. MI transition crossing simulations (I. Kourbanis) V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings21 Phase space distributions after transition No JumpHalf Jump Full Jump A gamma-t jump system is needed for loss free transition crossing.

22. MI Gamma-t system A first order jump system with small dispersion increase (taking advantage of the dispersion free region) Design goal:   T =  1 within 0.5 ms  d  /dt = 4000 1/s  16 times faster than the normal ramp (240 GeV/s) Components:  8 sets of quad triplets  8 sets of power supplies  Inconel beam pipe Need to finalize the design, build and test a gamma-t quad. V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings 14

23. Recycler slip stacking simulations (R. Ainsworth) Compare slip stacking simulations in the Recycler for the current running and PIP-II using synergia. Simulations include magnet multipoles, space charge, and realistic apertures. Focus on the tune spreads and shifts caused by space charge and chromaticity. V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings23

24. PIP-II high chromaticity 24 tune shift = -0.00365*-18 = 0.0657 Increase chromaticity to -18 in both places Off-momentum bunch shifted even closer to half - more losses V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings

25. Beam Stability in MI and Recycler (P. Adamson) No transverse stability issues for Main Injector in PIP-II era –Unless electron cloud shows up. Ongoing work to determine effects of beam pipe coating and beam scrubbing. Some work to do in Recycler –Dampers are fine when beam isn’t overlapped –Work ongoing to determine how dampers can operate in the overlapping region –Ongoing work to study fast horizontal instability Active working group If it’s e-cloud, pipe coating will help Low frequency (<1MHz) high-power (damp 10 turns growth rate) damper is buildable, if necessary V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings25

26. Recycler Horizontal Fast Instability: a surprise Doesn’t occur in Main Injector at same intensity –(even with shorter bunches) Differences between RR and MI –RR beam tube a little smaller –Combined function magnets? –Studies and simulations in progress E-cloud is a popular explanation given the fast growth rate, but we can’t yet explain all the details Trapping in gradient magnets? –Similar instability seen at extraction in CERN PS? R. Steerenberg et al., PAC07 –Does not occur for 700kW operations Potential issue at PIPII intensity V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings26 ½ synchrotron period One batch, at injection Growth rate 10-15 turns Color scale shows horizontal motion Machine turns

27. Controls V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings27

28. Controls Modifications for Booster 20 Hz Operations (J. Patrick) 15 Hz is the fundamental frequency of the control system There is significant but mostly straightforward work involved to convert to 20 Hz The time consuming part will likely be identifying all the places in the software where 15 Hz is assumed Work can begin well before 20 Hz operation is needed V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings28

29. Controls Modifications for Booster 20 Hz Operations (J. Patrick) - 2 Modifications Needed –New Master Oscillator to generate 20 Hz Good idea anyway, current one is very old Could make a new one with dual 15/20 Hz capability –Update TLG code Straightforward but significant work to verify Various timer delays in the complex may need adjustment –IRMs (Internet Rack Monitor) Nearly 30 year old technology at start of PIP-II operations Difficult maintenance Replacement is highly desirable –Front-end data acquisition V. Lebedev & I. Kourbanis, Summary of Working Group 3: Rings29