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

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

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

FFAG 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 (  T 1 +  T 2 ) as compared with the triplet (lower  T implies less phase slip, more turns for fixed, high frequency rf)

FFAG 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

FFAG Momentum compaction in scaling FFAGs Scaling FFAGs: Pathlength or TOF always increases with p

FFAG Momentum compaction in linear nonscaling FFAGs Linear non-scaling FFAGs:

FFAG Cont…. 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. l FF

FFAG 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

FFAG Electron Model - Non-scaling Demonstration of New Accelerator Physics Gutter Acceleration asynchronous acceleration within a rotation manifold outside the rf bucket. Momentum Compaction Unprecedented compaction of momentum into a small aperture. “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

FFAG Electron Model - Construction 6m – 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

FFAG Radiofrequency system Adopt TESLA-style linear RF distribution scheme to reduce number of waveguides R=1M , Q=1.4  10 4 Where possible adopt designs already existing at the host laboratory. 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. Adopt 1.3 GHz ELBE buncher cavity to be used at Daresbury 4GLS Frequency variation of few to investigate 1 or 2 fixed points operation. 20 cm straight for installation

FFAG Quadrupole Magnet 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. General requirements: Gradient: 7 T/m Slot length: 10 cm Aperture: 40 mm wide, 25 mm high Rep rate <1Hz

FFAG 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

FFAG Dipole plus quad field lines Dipole only field lines 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% Magnet Concept (Vladimir Kashikhin, FNAL)

FFAG 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

FFAG 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 A Magnet body length 50 mm CF magnet with independently variable dipole and quad fields

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

FFAG Diagnostics Diagnostic designs described here –BPMs bunch train/single bunch operation Turn by turn data –OTRs (Optical Transition Radiation) Foils + detection 10 8 /bunch or lower for a bunch train 10 9 /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

FFAG 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 10 9 electrons/bunch ~66 nsec rotation period BPM Specification - General  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 BPM (Jim Crisp, FNAL) FNAL MI BPM Hardware and Single Bunch Operation

FFAG

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

FFAG

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 A, 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.. 3-D image of the electron beam obtained with OTR monitor Variation of the beam X-profile versus SPA05 lens current

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

FFAG Electron Model - Hardware and Measurements: Full Complement of Diagnostics designed or available including - Large aperture BPMs, OTR foils and detectors - Single Wire Scanners, Pepperpots Magnetic components designed or under design; short: 5-6 cm and strengths appear technically reasonable 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