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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. Design Information. Background Scaling vs. nonscaling Ring components Rf magnets Diagnostics BPMs - PowerPoint PPT Presentation
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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 (T1 + T2) 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
p
p
C
Cring
FFAG
Momentum compaction in scaling FFAGs
• Scaling FFAGs:
• Pathlength or TOF always increases with p
constant) a is(p
prC
FFAG
Momentum compaction in linear nonscaling FFAGs
• Linear non-scaling FFAGs:
)(
choices technicalare ''3.0
energyhigh at bend added0;
energy lowat bend reverse0;
quad. Fin point field-0 dipole, pure a ismagnet CF
-point gradient -0 theas definedorbit reference a is where
0
0
0
pppr
lBrlBp
pp
pp
p
p
p
cellF
F
Fo
Fo
cellcellF
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.
22
222
)1( FFt
Ft
lllr
lllr
l
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
FFAGElectron 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=1.4104
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 10-4 to investigate 1 or 2 fixed points operation.
20 cm straight for installation
FFAG Quadrupole Magnet
Fermilab Linac quadFermilab 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
FFAGCombined function magnet
SpecificationsDipole component of 0.15 – 0.2 T
Slot length: 10 cmMagnetic length: 7cm
Quad component of ~4T/mMagnet spacing: 5 cmAperture (good field): 50 mm wide, 25 mm highField uniformity 1% at pole tipSpace for internal BPM1Hz operation or less
No coolingNo eddy current problems
FFAG
Dipole plus quad field lines
Dipole only field lines
Power the dipole component with permanent magnets
CompactNo power issuesThermally stable PM material
Power the quadrupole component with a (modified) Panofsky coil
Compatible with rectangular apertureRelatively short endsPermanent 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 PotentialFixed points
FFAG
FFAG Combined Function MagnetV.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 parametersMagnet configuration C- type
Dipole field 0.15 TAdjustable quadrupole gradient 0 – 6.8 T/m
Dipole winding ampere-turns 7600 AQuadrupole pole winding ampere-turns 11638 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• 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
FFAG
1.3GHz button-type BPMs (FNAL Main Injector)1 set per magnet3 to 5 cm aperture20 micron resolution Internal mountingTurn by turn for ~10 turns109 electrons/bunch~66 nsec rotation period
BPM Specification - General
Digital receiver210 MHz adc sample rate12 bit resolution Single-bunch excitation of a filter as shown
105 MHz center frequency10 MHz bandwidthFilters must be stable and matched
adc must be synched to beam
BPM (Jim Crisp, FNAL)
-1
-0.5
0
0.5
1
0 20 40 60 80 100
FNAL MI BPM
Hardware and Single Bunch Operation
FFAG
FFAG
FFAG
FFAGEXAMPLE: Profiles from an OTR foil in the 120 GeV AP-1 proton line at Fermilab
FFAG
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 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.
15 20 25 30 35 40 450
20
40
60
80Horizont. profiles
10.12 mm
Marks on the OTR
SPA05=14 A
SPA05=9 A
SPA05=11 A
SPA05=0 A
I=0.975 A, F=-4 kV.
I(x),
rel. u
nits
X, mm
. 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