Transcript The Proposed Conversion of CESR to an ILC Damping Ring Test Facility M.

The Proposed Conversion of CESR to
an ILC Damping Ring Test Facility
M. Palmer, R. Helms, D. Rubin, D. Sagan, J. Urban, M. Ehrlichman
Abstract: In 2008 the Cornell Electron Storage Ring (CESR) will end nearly three decades of providing electron-positron collisions for the CLEO
experiment. At that time it will be possible to reconfigure CESR as a damping ring test facility, CesrTF, for the International Linear Collider project. With its
12 damping wigglers, CesrTF will offer horizontal emittance in the few nanometer range and, ideally, vertical emittances approaching those specified for the
ILC damping rings. An important feature of the CesrTF concept is the ability to operate with positrons or electrons. Positron operation will allow detailed
testing of electron cloud issues critical for the operation of the ILC positron damping rings. Other key features include operation with wigglers that meet or
exceed all ILC damping ring requirements, the ability to operate from 1.5 to 5.5 GeV beam energies, and the provision of a large insertion region for testing
damping ring hardware. We discuss the CesrTF machine parameters, critical conversion issues, and experimental reach for damping ring studies.
CesrTF Baseline Lattice
CesrTF Conversion
bx
North IR with Wigglers (Top View)
Lattice design carried
out with 6 wigglers in
North IR and 6 wigglers
in the CESR arcs. Zero
dispersion regions created
for all wigglers.
~18 m
South IR with RF Cavities for Short Bunch Operation (Top View)
• Move 6 wigglers to North IR
• Space for insertion devices in South IR
 Ample cryogenics support
 SCRF cavities for short bunch length
operation
 Instrumentation (eg, possible laserwire
installation)
 Could support an extraction line
• Upgrade feedback system for 4 ns
spaced bunches
• Upgrade beam instrumentation
 Ultra-low emittance measurement
19W
19E
15W
14W
15E
14E
CLEO
South IR
Parameter
Value
E
2.0 GeV
Nwiggler
12
Bmax
2.1 T
ex
2.25 nm
Qx
14.59
Qy
9.63
Qz
0.098
sE/E
8.6 x 10-4
tx,y
47 ms
sz
6.8 mm
ap
6.4 x 10-3
Quadrupole, Bend, Wiggler and
Sextupole Rotations
100 mrad

Points plotted at ½ damping time
Tunes calculated for 1st half and
2nd half of damping time
hx
Tune Scans to Determine Working Point
Equilibrium Emittance with IBS for Baseline Lattice
Nominal CESR Magnet Alignment Resolutions
Nominal Value

Color Scale: ln10 Qx2  Qy2
Intrabeam Scattering (Preliminary)
Low Emittance Operation
Misalignment
Quadrupole, Bend and Wiggler Offsets
Sextupole Offsets
Frequency Map Analysis
Target ey~ 5 – 10 pm
Wiggler Moves
 Add cryogenic support
 Add electron cloud diagnostics
by
Wiggler
Locations
North IR
Dynamic Aperture
Calculation assumes vertical emittance is dominantly due to emittance coupling.
ex grows by factor of ~3 from zero current to ILC bunch current
150 mm
300 mm
Nominal Values
Example Vertical Emittance Sensitivities
• IBS growth rates scale as 1/g4 a increase energy
 Increases zero current emittance
 Decreases sensitivity to IBS
Dominant Sensitivity
• Can also lengthen bunch
• Explore 2.5 GeV lattice with 9 mm bunch as potential configuration for low
emittance studies at the ILC bunch current (eg, electron cloud studies)
Correction Algorithm
• Randomly misalign elements using multiple seeds
• Orbit correction followed by dispersion correction
using steering and skew quadrupole correctors
• Include effects of BPM errors
Correction Type
Orbit Only
Orbit+Dispersion
Conversion and Operations Plan
• CESR-c/CLEO-c program ends on March 31, 2008
• 7-9 month conversion followed by commissioning
• Available for ILC DR R&D in early 2009
• Operating Schedule
 Approximately 110 running days/year in 2 periods
 Interleaved with CHESS X-ray running
 Significant downtime at each transition for installation of prototypes and
other hardware
Average Value
10.2 pm
3.9 pm
Equilibrium Emittance for 2.5 GeV Lattice and 9mm Bunch Length
ex grows by a factor of < 1.6 from zero current to ILC bunch current.
Zero current ex ~2.85 nm. .
95% Limit
21.4 pm
8.2 pm
Conclusion: Simulations indicate that CesrTF can be operated in a regime that is
useful for a range of damping ring studies. In particular, CesrTF will have the ability to
study physics issues associated with the damping ring wigglers and validate the final
design of the ILC wigglers and vacuum chamber. The machine will be able to directly
explore the impact of the electron cloud on the emittance. Due to the modest scope of the
conversion, CesrTF offers an efficient route towards exploring key areas of ILC damping
ring physics and technology on a timescale consistent with the start of ILC construction.
• Minimum of 3 years of operation as a test facility
Cornell University’s Laboratory for Elementary-Particle Physics is supported by the U.S. National Science Foundation and Department of Energy.