Transcript Cornell CHESS Template

CESR as Light Source
David L. Rubin
for the CESR Operations Group
Cornell University
Laboratory for Elementary-Particle Physics
- Introduction to CESR
- CESR Operating Status
- Multi-bunch optics
- Low emittance tuning
- Single beam optics
- Low emittance layout
April 28, 2009
CHESS Site Visit
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CESR
- CESR operates with counterrotating
beams of electrons and positrons
- Beam energy ranges from 1.5-5.5 GeV
-Injector
- Linac ~ 300MeV electrons & 150MeV
positrons
- Synchrotron booster accelerates to full
storage ring energy
- Linac/synchrotron cycle at 60Hz
- Electron gun pulses at up to 72MHz
to fill CESR with bunches spaced 14ns
Bunch configuration
- Traditionally 9 equally spaced trains
- As many as 6 bunches/train with
14ns spacing
- Itotal ~ 250 mA/beam
April 28, 2009
CHESS Site Visit
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CESR operating status
CHESS optics
Electrons
200 mA - 30 bunches
Positrons
180 mA - 22 bunches
Lifetime ~ 12 hours
Fill length ~ 3hours
h ~ 140 nm
v ~ 1-2 nm
X-ray beam position stability < 30 m.
April 28, 2009
CHESS Site Visit
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CESR operations
Sunday operation
Ion trapping
23.25 hours beam
23.5 hours beam
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CESR multi-bunch operation
Colliding beam configuration
4 electrostatic deflectors generate differential
closed orbit distortion that separates electron
and positron bunch trains.
9X5
Beginning fall 2008 interaction region
low  optics replaced with simple FODO
lattice structure. (L0)
Vertical separators removed (L3)
and the 9X5 configuration is no longer
viable.
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CESR multi-bunch operation
CHESS operation today
4 positron trains and 6 electron trains
with 6 bunches/train
April 28, 2009
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Beginning September 2009
10 trains 4 bunches/train
electrons and positrons
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Low Emittance Tuning
Having removed the low- insertion
and CLEO 1.5T solenoid
and rotated IR quadrupoles
and vertical separators
We have eliminated sources of transverse coupling, vertical
dispersion and vertical beam size
New optics configuration permits significant reduction in
vertical emittance
Operation with counterrotating beams limits the number of bunches.
High bunch current /good lifetime/ low vertical emittance
are mutually exclusive
April 28, 2009
CHESS Site Visit
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Low Emittance Tuning
-Principle component of the CesrTA project is to reduce vertical emittance
and develop procedures to monitor and maintain low emittance
-Survey and alignment - survey network
-Digital beam position monitor electrons will permit single bunch/single pass
real time nondestructive measurement of
- Orbit
- Optical functions
- Transverse coupling
- Dispersion
-On line analysis and modeling software will deploy corrector magnets
(vertical steering, quadrupoles, skew quads) to
preserve minimum emittance as well as beam position
April 28, 2009
CHESS Site Visit
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Accelerator R&D
Single beam operation?
“Pretzel” configuration (electrons and positrons)
- Constrains optics (precludes low horizontal emittance)
- Complicates injection
(injected bunch collides with opposite species stored beam)
- Limits number of bunches
- Impedes low emittance tuning
(beam is off axis in all magnets)
Single beam (positrons)
- Lower horizontal emittance optics
- More bunches (lower bunch current, smaller vertical beam size, longer lifetime)
- More efficient injection (top off ?)
- Reduced vertical emittance
- No ion trapping
April 28, 2009
CHESS Site Visit
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Single beam optics
Based on existing Ring layout
(Machine studies experiments are underway)
5GeV
Positrons
>180 bunches
I = 250mA
h = 50nm
v ~ 200pm
April 28, 2009
CHESS Site Visit
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Low Emittance layout
Rearrange hard bends for single beam operation
- Lower horizontal emittance
- Space for undulator/wiggler
Existing layout
Low emittance
(single beam)
layout
April 28, 2009
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Lattice development
Today
September Machine
2009
studies
New ring layout
Emittance[nm] (h/v)
140/1
110/1
52/0.2
15/0.1 7/0.05
Bunches
30/22
40/40
>180
>180
>180
Current/beam [mA]
175
225
250
250
250
Particle species
e+ & e- e+ & e-
e+
e+
e+
Horizontal Tune
10.57
10.21
14.57
14.57
14.57
Energy[GeV]
5.3
5.3
5.0
5.0
3.5
April 28, 2009
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Summary
• Today - 2 beam operation ~ 175mA/beam, 52 bunches
• Beginning Fall 2009
- 2 beams, 225mA/beam (80 bunches)
• Single beam existing layout (?)
Positrons, 250mA, >180 bunches, 50nm
• Single beam - low emittance layout
Positrons, 250mA, >180 bunches, 15nm
April 28, 2009
CHESS Site Visit
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