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RF System for Bunch Rotation

RF System for Bunch Rotation. C. Ohmori 　（ KEK). Bunch Rotation in Longitudinal Phase Space. Momentum. Apply RF Voltage @ 5MHz. Direction of Beam. Saw Tooth RF is considered for smaller D p/p. After several turns in FFAG Small D p/p. Injection to FFAG Large D p/p.

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RF System for Bunch Rotation

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  1. RFSystem for Bunch Rotation C. Ohmori　（KEK)

  2. Bunch Rotation in Longitudinal Phase Space Momentum Apply RF Voltage @ 5MHz Direction of Beam Saw Tooth RF is considered for smaller Dp/p After several turns in FFAG Small Dp/p Injection to FFAG Large Dp/p Low Frequency for Large Bucket vs. Difficulty to get High Voltage at Low Frequency

  3. Saw-tooth • PRISM-low energy muon (68 MeV/c) => 200 kV/m＠5 MHz • Scaling FFAG for Neutrino Factory – high energy muon (200 MeV/c) • Bunch Merging Scenario for muon collider

  4. PRISM • 200kV/m @ 5 MHz • MA cavity X Tube AMP:1 kW X 60A/.33 m, 66kV/gap • Core impedance : about 160 W/core X 6 cores • Tube AMP : OK, obtained >60 A as RF current • Optimum design for only pulse operation (duty <0.1%) • Tubes is operated with Class B for 10 ms, other;Class C. • 1 APS for 4 RF AMP. • Tested with a test cavity and 43 kV/gap was obtained • Saw-tooth RF is tested.

  5. MA core for PRISM 1.7 m

  6. PRISM Cavity Design AMP Cavity APS Beam Pipe 33cm Side View

  7. PRISM But cost is expensive. cores >> AMP+PS And, prefer more voltage for more muons. 200kV/m => 300 kV/m Solution Improvement of Cavity (core) impedance Other approach: ceramic cavity

  8. Improvements of cavity impedance • Hybrid cavity with ceramic cavity • Improvements of cavity cores • X 2 by annealing under magnetic field for thinner ribbon • Small cores : OK • Large core ?

  9. How to improve • MA consists of Fe, Si, B, Cu and Nb. • Amorphous ribbon (<20 mm) is annealed and crystallized. • Combination of magnetic field during annealing and thinner ribbon (13 mm) • The small crystal has an axis magnetized easily. By the special annealing, the axis is equal. • But relation between core impedance and this effect is not clear. • Small cores : proved by Hitachi Metal • Large core : need big magnet and special oven. => Appling FY2007 JSPS money to produce these special core in KEK. B-H curve of MA core produced by annealing with/without magnetic field. (by Hitachi Metal)

  10. Ceramic Cavity • Proposed by J. Griffin. • Low frequency air core cavity with a ceramic capacitor to resonate. • Titanium Oxide capacitor was tested. 50kVDC (tested with 60kVDC). 1200pF. Electrodes are O.D. 121mmX I.D. 52mm, Thickness of ceramic is 14mm. • Supported by JSPS money. Purpose : bunch rotation with low rep. rate. • Small test cavity :30 cm X 30cm • 4 kW, Q=700, fres=7 MHz • High power test is planned. • High rep. rate : Hybrid cavity system with MA cavity. • Effective Q => below 100.

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