1. 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

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

3. Scaling vs. Linear Non-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 T implies less phase slip, more turns for fixed, high frequency rf)

5. Momentum Compaction of Orbits
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
Pathlength or TOF always increases with p

7. Momentum compaction in linear nonscaling FFAGs

8. Cont…. But, the transverse excursion cannot be ignored at low energy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 Fermilab Linac quad 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. Magnet Concept (Vladimir Kashikhin, FNAL)
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 T
Adjustable quadrupole gradient – 6.8 T/m
Dipole winding ampere-turns A
Quadrupole pole winding ampere-turns A
Magnet body length 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 Other diagnostics 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 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.
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