PPP Booster

Outline of Booster PPP tasks Beam Quality Goals K Seiya W Pellico Injection Dave Johnson CY Tan W Pellico Capture CY Tan K Seiya W Pellico Acceleration Transition B Zwaska J Eldred W Pellico Operations W Pellico K Seiya CY Tan Parameters: 800 MeV Injection Energy Emittances Injection 1 pi-mm-mr 6 σ Longitudinal delta 100 keV Injection Beam Current 10 to 40 ma Extraction: Extraction Current (Max) 6.7E12 Output Emittance pi-mm-mr 6 σ Output Longitudinal delta < 6 MeV Other Issues/Requirements: Bunch Rotation Cogging Notched Booster Beam System Loss (Watts) 525 ring wide Extraction Losses RF System – voltages Dampers

Booster Historic Perspective Stacking back in 2004: High batch intensity – Mid 5E12 range Booster efficiency - ~85% Larger V/H emittances: IPM data – 10 to 20%

PPP – Present Booster Operating -Three IPM data sets on $19

PPP – Beam Quality Maintain current level of losses Provide Recycler Longitudinal E spread of < 6 MeV Provide Recycler Transverse < 16 pi Provide up to 6.6E12/pulse to Recycler Operate at 15 Hz

PPP - Injection Hardware – Injection Girder 6 m between grad. mag.  x =4.9m  y=18.5m (impacts painting scenario) Existing 3 bump chicane – Center dipole 44 mr – Exceeds peak 800MeV -> implies new design New injection chicane design – 3 Bump – 4 Bump – Hor or Ver injection Expand SS by shortening adjacent grad.mag. (to allow for chicang and inj. absorber) Beam – Linac beam current Lower current means longer injection and higher foil hits leading to higher heating/losses For 10 mA-> 112 us -> 60 turns – Assume: Booster 6  emittance is 20  -mm-mr – Linac rms emittance ~ 0.23  - mm-mr – Difference in emittance implies trans. phase space painting want large emittance ratio (linac/Booster)

PPP – Injection (2) Beam – Assume 7.0E12 injection per cycle – Injection Losses (assume same stripping efficiency) Increase inj intensity 5E12->7E12 Increase duty factor x2 Increase energy x2 Losses increase x 5.6 Need injection absorber-> modify straight section – Foil heating due to circulating beam depending on linac intensity Emittances Painting scenario Hardware – Chicane dipoles New magnets – Painting magnets Where to install – Foil Thicker ~500 ug/cm 2 for 99.8% strip efficiency Size/geometry to be determined New foil holder – New, shorter us/ds gradient magnets to increase SS length – Injection absorber Internal absorber in grad mag External absorber

800 MeV Transport line Vertical angle down chute is ~ 13 degrees (227 mr) formed by MV1 and MV2 At 400 MeV (brho = T-m) – requires an integrated dipole field of ~7.22 kG-m. – Effective length 1.16m implies field of ~ 6.25 kG – Loss rate from Lorentz stripping ~ 1.8x10 -5 /m At 800 MeV (brho = 4.88 T-m) – requires a integrated dipole field of ~11.1 kG-m. – Based on same loss rate requires field of less than 4.15 kG – Magnet length increases to ~2.7 m – Is there enough room for increased length ?

Transverse Phase Space Painting Transverse phase space painting – Horizontal or vertical or both –  x <  y implies reduced losses by painting in vertical direction – Where to put painting magnets- up/down short straights. – Vertical aperture thru us/ds grad magnets – Implications on matching from transport line Example: paint both (left) paint Hor/steer Ver (right) *Example for 1 GeV

Booster Capture Beam -> 2ma to 40ma Capture – Bucket to Bucket Bunch by Bunch Notcher in Linac Long load time – RF sweeping Phase Lock (What frequencies?) – Paraphase Gap Clearing (Gap made in Linac) Barrier Bucket Long DC Dwell Time Issues – Space Charge Longitudinal Transverse – Emittance Painting Aperture Hardware Harmonic Cavity – Part of PIP Barrier Bucket Cavity – Only for long fill – Lots of volts (like Harmonic) Booster Notcher System – Same volts as current sys – 800 MeV but less beam GMPS Ramping – Front Porch (Depends on I) – Linac Slew – Correctors – hold B-field

PPP –> Load Time vs Current Paraphased capture – typically faster than bucket to bucket unless bucket to bucket does not have unused RF cycles for even fill. Harmonic bucket to bucket is faster than non-harmonic.

Different filling patterns No chopping. Assume PX injection frequency MHz into MHz. Ratio 162.5/45.17 = Random injection into bucket because of non integer multiple of Booster frequency. +/- 90 deg chopping +/- 60 deg chopping

PPP –> 735MeV = 9*44.4 Mhz = 400Mhz There is no harmonic overlap between PX cavity frequencies and Booster frequencies for considered energies. However, if one uses SNS or our current frequencies – we can have a direct lock at 735MeV.

800 MeV injection, Paraphased Just before transition At 0.4 msθrms = 0.37 degErms = 1.5 MeV 7e12 protons per batch injection energy spread is 300 keV

2 nd harmonic, max voltage MeV injection 250 injection, 100% capture θrms = 0.32 degErms = 1.4 MeV Note shoulders, probably need to change RF ramp rate.

2 nd harmonic, max voltage MeV injection 125 injection, 100% capture Erms=1.4 MeVθrms=0.39 deg Note shoulders again, probably need to change RF ramp rate.

2 nd Harmonic ramps

16.5 pi mm mm 95 % beam loss Vertical acceptance collimator

:Voltage from space charge, :space charge impedance Vsc= 20.6 l =100% of bucket length Vsc= 49.2 l =50% of bucket length Vsc= 141 l =10% of bucket length Voltage from longitudinal space charge N: 8.17e10 particles per bunch g 0 =4.0

PPP-Transition (1) Characterization of losses – Point loss at transition – Slow losses before and after transition “High-field loss” Point loss can be well- suppressed with enough RF and tuning – Rapidly gets worse with intensity Need to better characterize high-field loss – Difficult with inadequate RF voltage

PPP-Transition (2) Strategy 1: Avoid Transition Best option is new magnet lattice – Move  T above 10 or so “Stronger” lattice with greater momentum compaction Small slip factor at extraction complicates bunch rotation and phase lock – Make  T imaginary Difficult to make a round version Low slip factor at injection complicates capture or longitudinal painting – Additional benefits of new magnets and a separated function lattice Re-implement  T jump – Magnets were removed but striplines and power supplies remain – No-zero dispersion places for magnets – Quad steering can now be solved with magnetic cogging and new correctors – Can the scheme be improved

PPP-Transition (3) Strategy 2: Deal with transition Focus-Free Transition Crossing – Use harmonic RF to match bucket shapes Requires substantial RF system – Somewhat contradictory simulation results Outside experience with this method has not been very successful Voltage Jump at Transition – Overfocus beam to force a match – Requires about 25 % overhead in RF voltage Quad damper – Feedback on the main RF to reduce quad oscillations – Similar effectiveness as voltage jump – Similar voltage overhead requirements

PPP – Operations/Misc – 7E12/pulse Hardware Dampers – PIP building longitudinal Digital FE – New Transverse System (not done) – May need additional Power Beam Dump – Good Kickers – Good Diagnostics – Good Shielding (Flux higher – still 8 GeV) – Relies upon active system Low Level – being upgraded – Will need to fit new injection Beam Increase Flux – 3.6 E17 pph Assuming e12 – PIP goal is 2.2E17 pph HOM – Assume higher Transverse – Rely on chroms but…. – Injection damping? – Lifetime/Emittances? Head-Tail ?

Booster 20 Hz Option We investigated 20 Hz operations for the Booster and found the following: – Cost would depend upon injection time to some degree – PIP is adding three additional cavities but two more would be likely for 20 Hz high intensity operation Cavity plus PS would coast about 4 M$ for 2 cavities – Injection bump and supply would need to be redone Cost is about 250k$ (PS) and 1M$ for magnets Extraction Septa and PS would be similar Booster girder changes is 1.2M$ for short load times – 18.M$ for longer injection dwell time

Conclusions Faster – Cheaper – Better Based upon first glance – Booster to first order can operate in the scenarios so far considered. There is very little cost differences for most options but the low current will cost the most since modification to Booster GMPS will likely be required. The low current option is also the least compatible with current system. 1.A decision should be made as soon as possible to leverage PIP effort. 2.Any decision should have a plan for Booster and it’s expected operational lifetime. 3.Several critical items such as notching in Linac and injection girder need to be addressed. The history of delay will necessitate PIP continue as planned even though it may not be optimal for PPP. Rating Options: Need to understand priorities – beam flux, timetable, cost and uptime….