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NSLS II: Accelerator System Overview NSLS II Advisory Committees October 18/19, 2006 Satoshi Ozaki. Introduction. NSLS II: A highly optimized, third generation, medium energy storage ring for the x-ray synchrotron radiation: The CD-0 approval articulated required capabilities as: - PowerPoint PPT Presentation
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NSLS II: Accelerator System Overview
NSLS II Advisory CommitteesOctober 18/19, 2006
Satoshi Ozaki
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Introduction
• NSLS II: A highly optimized, third generation, medium energy storage ring for the x-ray synchrotron radiation:
• The CD-0 approval articulated required capabilities as: • ~ 1 nm spatial resolution,• ~ 0.1 meV energy resolution, and• single atom sensitivity (or sufficiently high brightness)
• These and other requirements translate into the target parameters of the storage ring as;• ~3 GeV, 500 mA, top-up injection• Brightness ~ 7x1021 photons/sec/0.1%bw/mm2/mrad2
• Flux ~ 1016 photons/sec/0.1%bw – Ultra low-emittance (x, y): 1 nm horizontal, ~0.01 nm vertical
20 straight sections for insertion devices ( 5 m), • A high level of reliability and stability of operation
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Linac
Booster
Storage Ring
Accelerator System Configuration
NSLS II Accelerator System:
• 200 MeV S-band Linac
• 3 GeV 1 Hz Booster
•Top-up injection once per minute
• 3 GeV storage ring: 30 DBA configuration
•15 long (8 m) straight with high -function•15 short (5 m) straight with low -function
Booster
Storage Ring
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Rendering of the NSLS II Ring (Rear View)
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Injector Linac
• S-band linac system providing 200 MeV electron beams of 7 nC to the Booster in one pulse
• Electron source: thermionic DC gun modulated to match 500 MHz RF of booster and storage ring
• Five accelerating structures with three klystrons operating at 1.3 GHz• The system commercially available in turn-key procurement:
• ACCEL• THALES
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Booster Synchrotron
• 200 MeV to 3 GeV booster• Hung below the ceiling of the storage ring tunnel and has the same
circumference of 780 m• The lattice arranged to have no booster components above storage ring
straight sections, except for one 8-m straight for RF cavity• Relatively light weight small magnets; low power and air cooled:
• 60 combined function dipoles: 1.5 m long, 25 mm gap, 0.7 T, ~580 kg• 96 quadrupoles: 0.3 m long, <10T/m, ~45 kg• 15 sextupoles: 0.4 m long, <200T/m2, ~55 kg• 15 sextupoles: 0.2 m long, <200T/m2, ~30 kg• 60 orbit correctors
• Up to 100 bunches per cycle for initial fill• Up to 20 bunches per cycle with the hunt-and-fill bunch pattern• One PETRA-type (commercially available) RF cavity• Very low emittance at the storage injection energy helps smooth low loss
top-up injection.
• Purchase components from industry based on our reference design, and build and commission in-house
• Turn-key procurement of a compact booster in separate tunnel: an option
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Booster Lattice and its Relationship with Storage Ring
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Storage Ring Lattice Layout
Linac
RF Station
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Storage Ring
Storage ring configuration• DBA30 lattice (780m circumference) with 15 super-periods, each ~52m long• Super-period: two identical cells separated by alternating 5m and 8m straights• Short straight: x = 2.7m, y = 0.95m, and dispersion = zero • Long straight: x = 18.2m, y = 3.1m, and dispersion = zero
• This Hi-Lo is suited for variety of ID as well as top-off injection• Weak bends (0.4T) with damping wigglers to achieve ultra-small emittance• Lattice magnet: (designed with 20% head room)
• Dipoles: 60 (50 with 35 mm gap and 10 with 60 mm gap for IR beams)• Quadrupoles: 360• Sextupoles : 390• Correctors and skew quadrupoles: 240 + (4 X ID)
• 500 MHz superconducting RF cavities each operating with 270 kW power level• Harmonic number (No. of buckets): 1300, of which ~ 80% will be filled
• A 2-cell harmonic cavities for bunch lengtheningBasic performances:• 3 GeV, 500 mA, Top-up with current stability of <1%• Bare Lattice: x ~2.1 nm, y ~0.008 nm (Diffraction limited at 12 keV)• Pulse Length (rms): 2.9 mm/~10 psec
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Lattice functions of half of an NSLS-II SR super-period (one cell).
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Dispersion Section of a Cell
In order to reduce the transmission of ground vibrations beam height is set at 1 m from the SR tunnel floor, instead of standard 1.4 m.
Girder Resonant Frequency > 50 Hz
Alignment tolerance of multipoles on a girder is 30 m, whereas girder-to-girder tolerance is ~100 m
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Dynamic Aperture of the Lattice
For on momentum and off momentum cases by 3%
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Horizontal Emittance vs. Energy Radiated by DW
Dots represent the cases with 0, 1, 2, 3, 5, 8 damping wigglers, each 7-m long with 1.8 T field
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RF Power Up-grade Path
RF Power Requirements for Dipole and Various Insertion Device Configurations.
Covered in baseline proposal
Installed RF Power
(270kW/unit
Power the 3rd cavity with 300kW Transmitter
Add 4th RF station
RF power # P(kW) # P(kW) # P(kW) # P(kW)
Dipoles - 144 - 144 - 144 - 144
Damping Wigglers (9.23 kW/m, 7m each)
3 194 4 259 8 517 8 517
CPMU’s (4.17kW/m, 3m each)
3 38 6 76 6 76 10 127
EPU’s (4.1kW/m, 4m each)
2 33 4 66 4 66 5 83
Additional Devices ? 200
Total
Available Power
409
540
545
540
803
810
1071
1080
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Ultimate Configuration and Performances
Ultimate Configuration:• 8 damping wigglers (7 m long, 1.8T peak field)• 4 RF cavities with 1,080 kW of RF power
Expected performances at 3 GeV:• Beam current: 500 mA• Emittance: x ~ 0.5 nm, y ~ 0.008 nm• Flux ~ 1016 photons/sec/0.1%bw • Brightness ~ 7x1021 photons/sec/0.1%bw/mm2/mrad2
• Beam Size (x/ y) at the center of short straights: ~38.5/~3.1 m
• Beam Divergence (x’/y’) ~18.2/~1.8 rad• Pulse Length (rms) with damping wigglers: 4.5 mm/~15 psec• 19 user device (e.g., undulators) straights (15 x 5 m & 4 x 8 m)
• 4 long straights for large gap user insertion devices• 15 short straight for user undulators, some with canting
• 8 user compatible (fixed gap) damping wigglers• Many bending magnets for soft X-ray beam lines (critical energy ~2.4 keV)• Up to 5 bending magnets for IR, far-IR, and THz beamlines
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Baseline Configuration & Performances
Proposed baseline (CDR): • 3 damping wigglers (7 m long, 1.8T peak field)• 2 RF cavities with 540 kW of RF power• 5 user beamlines (supported by trust funds)
Expected performances at 3 GeV:• Beam current: step-by-step increase to 500 mA• Emittance: x ~ 1 nm, y ~ 0.008 nm• Flux ~ 1016 photons/sec/0.1%bw ?• Brightness ~ 4x1021 photons/sec/0.1%bw/mm2/mrad2 ?
• Beam Size (x/ y) at the center of short straights: ~54.5/~3.1 m ?• Beam Divergence (x’/y’) ~25.7/~1.8 rad ?• Pulse Length (rms) with damping wigglers: 4.5 mm/~15 psec ?• No. of DW that can be used for light source: 3 • Max number of ID beam lines: ~10 (e.g., 6 CPMU [3 m] and 4 EPU [4 m]) • A number of bending magnets for soft X-ray beam lines (EC ~2.4 keV)• No. of IR beams from wide gap dipoles: 5
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Issues for Further Studies
• Development of precision alignment (~30 µm) technology• Development of the optimum orbit correction and feedback scheme
for high level orbit stability: – A factor of ~3 improvement over the submicron stability recently
reported with some recent light sources• Impact and remediation of 5 mm gap undulator with short pitch to the
dynamic aperture and the beam life-time– Because of the vertical focusing effect of undulators with short
pitch, they cannot occupy the part of the ID straight where the vertical -function is large, i.e., areas away from the center of the straight
– This limits the 5 mm gap undulator length to ~3 m• Impact of EPU on dynamics of the beam• Use of canted insertion device • Overall value engineering efforts
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Summary
• Made good progress in last nine months in developing CDR for NSLS II• Optimized and define the configuration of the accelerator systems• Undertook conceptual design of accelerator systems, in some case
more detailed• Assembled accelerator parameter tables
• We have a innovative design of a highly optimized synchrotron light source capable of meeting requirements articulated in the CD-0 document with ultra-high performances
• There are a number of issues requiring further study:• Insertion devices and their impact on the dynamic aperture and
beam life-time• Diagnostics and feed-back for the required highly stable beam
operation• General value engineering exercise to control costs
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Injector Linac Parameters
Linac
Nominal/maximum linac energy (MeV) 200/270
Frequency (GHz) 2.998
Number of accelerating structures 5
Number of klystrons (no hot spare) 3
Pulse repetition rate (pps) <10
Beam pulse length (ns) 1 - 80 (up to 1µs)
Pulse charge (nC) (overall charge in a macropulse) >7
Energy spread ( %) <0.5
Total number of traveling wave accelerating sections 5
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Booster Ring Parameters
Booster RingInjection energy (MeV) 200Nominal top energy (GeV) 3Circumference (m) 780Ramping repetition rate (Hz) 1Acceleration time (s) ~0.4Harmonic number 1300Radio frequency (MHz) 499.46Total number of cells 15Number of combined function bending magnets 60Number of quadrupole 96Dipole nominal aperture (mm) 25Dipole field at injection (T) 0.0533Dipole field at extraction at 3 GeV (T) 0.7Energy loss per turn at 3 GeV (keV) 500Beam current (mA) 2.7Natural emittance at 3 GeV (nm-rad) 11.5Number of bunches from 1 to >100
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Storage Ring Parameters
Storage Ring Assembly
Number of DBA cells 30Circumference (m) 780Nominal energy (GeV) 3Circulating current @ 3 GeV, multi-bunch (mA) 500Circulating current @ 3 GeV, single bunch (mA) 0.5Harmonic number 1300No. of filled bunches/harmonic number 80%Nominal bending field @ 3 GeV (T) 0.4Dipole critical energy @ 3 GeV (KeV) 2.4Number of 8 m straights: [βx/βy (m)] 15: [18.15/3.09]Number of 5 m straights: [βx/βy (m)] 15: [2.72/0.945]Number of dipoles 60Number of quadrupoles 360Number of sextupoles 390Number of correctors and scew 240 + (4 X ID)
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Storage Ring Parameters (Continue)
Damping Wigglers
Initial number of 7 m damping wigglers 2 Fixed +1 Vari
Final number of 7 m damping wigglers 5 Fixed +3 Vari
Max. peak field (T) 1.8
Radiation energy loss per wiggler (keV) 129.3Initial radiation energy loss with 3 wigglers (keV) 387.9Ultimate radiation energy loss with 8 wigglers (keV) 1,034.4Bending magnet radiation energy loss (keV) 286.4Emittance of bare lattice (nm) 2.1Emittance with 3 wigglers (nm) 1.0Emittance with 8 wigglers (nm) 0.6
Storage Ring RF SystemRadio frequency (MHz) 499.46Number of superconducting cavities 2 +1 spareInstalled RF power for initial configuration (kW) 540Harmonic cavity (2 cells/cavity) 2
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