Hardware development for EMMA

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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
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Design Information

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

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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
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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)

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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

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Momentum compaction in scaling FFAGs

• Scaling FFAGs
• Pathlength or TOF always increases with p

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Momentum compaction in linear nonscaling FFAGs

• Linear non-scaling FFAGs

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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.

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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 32
• for nonscaling vs. scaling FFAGs

Fixed points
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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 Characteriz
e and optimize the complex parameter space for
rapid muon accelerators
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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
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Radiofrequency system
Where possible adopt designs already existing at
the host laboratory.
R1M?, Q1.4?104
Adopt 1.3 GHz ELBE buncher cavity to be used at
Daresbury 4GLS
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
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Quadrupole Magnet

• General requirements
• Gradient 7 T/m
• Slot length 10 cm
• Aperture 40 mm wide, 25 mm high
• Rep rate lt1Hz

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.
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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

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

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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
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EXAMPLE Profiles from an OTR foil in the 120
GeV AP-1 proton line at Fermilab
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Beam Profile Diagnostics for the Fermilab Medium
Energy Electron Cooler

• AbstractThe 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
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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
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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