Hardware development for EMMA

1. Hardware development for EMMA Electron Model with Muon Applications Electron Model with Many Applications C. Johnstone, Fermilab NuFact05 INFN, Frascotti, Italy June 21-26, 2005

2. Design Information • Background • Scaling vs. nonscaling • Ring components • Rf • magnets • Diagnostics • BPMs • OTRs • Single Wire Scanners

3. Scaling As a function of momentum • Parallel orbits • Constant optical properties • Orbit change, r, linear vs. Linear Non-Scaling As a function of momentum • Nonparallel orbits • Varying optics • resonance crossing • Orbit change ~quadratic • Smaller aperture requirements • Simple magnets   min

4. Optical layouts of FFAGs • Scaling and nonscaling lattices can have identical optical structures • FODO • Doublet • Triplet Rf drifts • The important difference is in the TOF vs. p, which is of particular importance for the linear non-scaling lattice: the FODO is 1.5 x (T1 + T2) as compared with the triplet (lower Timplies less phase slip, more turns for fixed, high frequency rf)

5. Momentum Compaction of Orbits • Momentum Compaction,  • Measure of orbit similarity as a function of momentum (also isochronicity for relativistic beams) • Measure of the compactness of orbits -   0, aperture  0

6. Momentum compaction in scaling FFAGs • Scaling FFAGs: • Pathlength or TOF always increases with p

7. Momentum compaction in linear nonscaling FFAGs • Linear non-scaling FFAGs:

8. Cont…. F l • But, the transverse excursion cannot be ignored at low energy • Eventually this transverse correction overtakes the net decrease with low momentum and C turns around giving an approximate quadratic dependence of C and TOF.

9. What does this mean? • Scaling FFAG can have only 1 fixed point, or orbit with is synchronous with the rf (fixed points are “turning” points in the phase slip relative to the rf waveform) • 1 turning point implies the beam slips back and forth across the rf crest twice • Linear nonscaling FFAG can have 2 fixed points (or 1) • Beam can optimally cross the rf crest 3 times • By using two fixed points for maximal acceleration, the ratio of extraction energy can be ~3:2 for nonscaling vs. scaling FFAGs Fixed points

10. Electron Model - Non-scaling Demonstration of New Accelerator Physics Momentum Compaction Unprecedented compaction of momentum into a small aperture. Gutter Acceleration asynchronous acceleration within a rotation manifold outside the rf bucket. “Uncorrectable” Resonance Crossing Rapid crossing of many resonances including integer and ½ integer; multi-resonance crossings in a single turn Evolution of phase space Under resonance conditions and gutter acceleration Validate concept for muon acceleration Characterize and optimize the complex parameter space for rapid muon accelerators

11. Electron Model - Construction – similar to the KEK ATF without straight sections (scaled down from 1.5 GeV to 20 MeV). Host: Daresbury Laboratory U.K. downstream of their 8-35 MeV Energy Recovery Linac Prototype (ERLP) of the 4th Generation Light Source (4GLS). 6m 6m

12. Radiofrequency system Where possible adopt designs already existing at the host laboratory. Adopt 1.3 GHz ELBE buncher cavity to be used at Daresbury 4GLS R=1M, Q=1.4104 1.3 GHz preferred over 3 GHz: reducing RF while magnet length is fixed, implies magnets become a smaller number of RF wavelengths. This implies smaller phase slip and more turns. 20 cm straight for installation Frequency variation of few 10-4 to investigate 1 or 2 fixed points operation. Adopt TESLA-style linear RF distribution scheme to reduce number of waveguides

13. Quadrupole Magnet • General requirements: • Gradient: 7 T/m • Slot length: 10 cm • Aperture: 40 mm wide, 25 mm high • Rep rate <1Hz Fermilab Linac quad The 5cm-long upgrade Fermilab linac quadrupole has peak pole-tip field near 3.5 kG, and the bore is 5cm. This is ideal for the 3 cm orbit swing envisioned for the ring. The gradient is stronger than required and will likely require a different coil.

14. Combined function magnet Specifications • Dipole component of 0.15 – 0.2 T • Slot length: 10 cm • Magnetic length: 7cm • Quad component of ~4T/m • Magnet spacing: 5 cm • Aperture (good field): 50 mm wide, 25 mm high • Field uniformity  1% at pole tip • Space for internal BPM • 1Hz operation or less • No cooling • No eddy current problems

15. Dipole only field lines Magnet Concept (Vladimir Kashikhin, FNAL) • Power the dipole component with permanent magnets • Compact • No power issues • Thermally stable PM material • Power the quadrupole component with a (modified) Panofsky coil • Compatible with rectangular aperture • Relatively short ends • Permanent quad + trim coil ±20% Dipole plus quad field lines

16. Advantage of variable quad and dipole fields? • Variable quad was felt to be most important for phase advance and resonance crossing controol • Variable dipole allows exploration of acceleration with 1 fixed point (1/2 synchrotron oscillation around “bucket”) or 2 (gutter acceleration • Measure phase space and emittance dilution • Both: different C /TOF parabolas • Asymmetric vs. symmetric • Correct for errors/end field Potential Fixed points

17. CF magnet with independently variable dipole and quad fields FFAG Combined Function Magnet V.S.Kashikhin, June 21, 2005 The proposed combined function magnet has C-type iron yoke and separate dipole and quadrupole windings. Each winding powered from individual power supply. They can be connected in series in accelerator ring. Dipole component of magnetic field formed by parallel surfaces of iron poles. Quadrupole field component formed by sectional quadrupole winding placed into the pole slots. Such configuration provides independent regulation both field components. Magnet parameters Magnet configuration C- type Dipole field 0.15 T Adjustable quadrupole gradient 0 – 6.8 T/m Dipole winding ampere-turns 7600 A Quadrupole pole winding ampere-turns 11638 A Magnet body length 50 mm

18. 2D modeling of new CF magnet Flux lines at maximum dipole and quadrupole currents. Dipole coil (blue), Quadrupole (red).

19. Diagnostics • Diagnostic designs described here • BPMs • bunch train/single bunch operation • Turn by turn data • OTRs (Optical Transition Radiation) • Foils + detection • 108/bunch or lower for a bunch train • 109/bunch for single bunch operation – will require closer examination for 108/bunch, single bunch operation • Other diagnostics • Single Wire Scanners • orbits are non-overlapping, • step increment microns • Pepperpot • phase space measurements in extraction line

20. BPM (Jim Crisp, FNAL) Hardware and Single Bunch Operation BPM Specification - General • 1.3GHz button-type BPMs (FNAL Main Injector) • 1 set per magnet • 3 to 5 cm aperture • 20 micron resolution • Internal mounting • Turn by turn for ~10 turns • 109 electrons/bunch • ~66 nsec rotation period • Digital receiver • 210 MHz adc sample rate • 12 bit resolution • Single-bunch excitation of a filter as shown • 105 MHz center frequency • 10 MHz bandwidth • Filters must be stable and matched • adc must be synched to beam FNAL MI BPM

24. EXAMPLE: Profiles from an OTR foil in the 120 GeV AP-1 proton line at Fermilab

26. Beam Profile Diagnostics for the Fermilab Medium Energy Electron Cooler Abstract—The Fermilab Recycler ring will employ an electron cooler to store and cool 8.9-GeV antiprotons. The cooler will be based on a Pelletron electrostatic accelerator working in an energy-recovery regime. Several techniques for determining the characteristics of the beam dynamics are being investigated. Beam profiles have been measured as a function of the beam line optics at the energy of 3.5-MeV in the current range of 10-4-1A, with a pulse duration of 2µs. The profiles were measured using optical transition radiation produced at the interface of a 250µm aluminum foil and also from YAG crystal luminescence. Variation of the beam X-profile versus SPA05 lens current . 3-D image of the electron beam obtained with OTR monitor

27. Electron Model - Demonstrates: Unprecedented compaction of momentum Asynchronous 2-fixed pt. gutter Acceleration Resonance Crossing Evolution of phase space and comparison with simulation Validate concept for muon acceleration

28. Electron Model - Hardware and Measurements: Magnetic components designed or under design; short: 5-6 cm and strengths appear technically reasonable • Full Complement of Diagnostics designed or available including • Large aperture BPMs, OTR foils and detectors • Single Wire Scanners, Pepperpots • Measure: • orbits, orbit stability, injection stability • probe injection phase space with a pencil beam • tolerances : field, injection, contributions of end fields • Evolution of phase space and comparison with simulation under different conditions of acceleration and resonance crossing • optimization and operational stability of accelerator conditions