NSLS II: Accelerator System Overview

1

• NSLS II Accelerator System Overview
• NSLS II Accelerator Systems
• Advisory Committee
• October 10, 2006
• Satoshi Ozaki

2
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 requirements translate into the target
  parameters of the storage ring as
• 3 GeV, 500 mA, top-up injection
• Brightness 7x1021 photons/sec/0.1bw/mm2/mrad2
• Flux 1016 photons/sec/0.1bw
• 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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Milestone Schedule
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Steps in the Baseline Configuration Development

• The original lattice for CD0 proposal was TBA24
  with tight bend and 630 meter circumference.
• Although the desired small emittance (?x1.5 nm)
  was thought to be within reach with the perfect
  lattice, it was found that any reasonable errors
  would have closed up the dynamic aperture.
• Search of an alternative
• Enlarged TBA24 lattice
• DBA lattice with more straights for damping
  wigglers for emittance control.
• Weak bends to enhance damping by wigglers.
• CD0 proposal also included a full energy linac
  injector.
• A booster in the storage ring tunnel was chosen
  for this baseline configuration with due
  consideration of reliability, performance and
  cost.

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Parametric Comparison of Lattice
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The Preliminary Review of NSLS II Lattice and
Accelerator Configuration May 11-12, 2006

• The Committee
• Dr. Carlo Bocchetta, Sincrotrone Trieste
• Dr. Michael Boege, Swiss Light Source
• Dr. Michael Borland, Argonne National Laboratory
• Dr. Max Cornacchia, Stanford Linear Accelerator
  Center (retired), Chairman
• Dr. Mikael Eriksson, MAXLAB
• Dr. Thomas Roser, Brookhaven National Laboratory
• Dr. Christoph Steier, Lawrence Berkeley National
  Laboratory
• The approach of NSLS II is to achieve the
  performance goal
• with a lattice whose focussing strength is
  comparable to that of existing 3-rd generation
  sources, but that also includes a number of
  damping wigglers to further reduce the emittance
  without the deleterious effect on the dynamic
  aperture normally associated with strong
  focussing lattices.
• Thus, the proposed design includes innovative
  ideas for a light source (damping wigglers and
  soft bends), informed by the experience of
  state-of-the-art existing facilities.
• While the design presents challenges for the beam
  dynamics, beam instrumentation, controls and
  hardware, the performance goals appear achievable.

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DBA 30 and Its Expected Performances

• 3 GeV, 500 mA, top-up injection
• Fifteen Superperiod consisting of two identical
  cells
• Fifteen 8-m long straights and 15 5-m long
  straights
• ?min,x /?min,y _at_ 8-m straight 18.2 m/3.1 m
  (Hi-?)
• ?min,x /?min,y _at_ 5-m straight 2.7 m/0.95 m
  (Lo-?)
• Bare Lattice ?x 2.1 nm, ?y 0.008 nm
  (Diffraction limited at 12 keV)
• Pulse Length (rms) 2.9 mm/10 psec
• Ultimate performance with full complement (56m
  1.8T) of wigglers
• Emittance (?x, ?y) 0.5, 0.008 nm
• Flux 1016 photons/sec/0.1bw
• Brightness 7x1021 photons/sec/0.1bw/mm2/mrad2
• 19 user device (e.g., undulators) straights (15 x
  5 m 4 x 8 m)
• 5 user compatible (fixed gap) damping wigglers
• 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
• Ultimate total power loss by bending magnets and
  insertion devices 1 MW
• Initial scope and performance is reduced to fit
  in the budget constraint, while maintaining the
  upgrade path.

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Rendering of the NSLS II Ring (Rear View)
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Accelerator System Configuration
Booster
Booster injection was chosen for a high level of
reliability
Since we operate with top-up mode, having the
booster in the same tunnel will have little
impact on the operational reliability
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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
• The system commercially available in turn-key
  procurement
• ACCEL
• THALES
• Issue control of energy droop causes by beam
  loading

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Injector Linac Parameters
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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
• 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, lt10T/m, 45 kg
• 15 sextupoles 0.4 m long, lt200T/m2, 55 kg
• 15 sextupoles 0.2 m long, lt200T/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.
• Procure components, build, and commission
  in-house
• Options turn-key procurement of this booster or
  a compact booster in separate tunnel
• Detailed discussion on Injection system by Timur
  Shaftan on the second day.

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Booster Ring Parameters
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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

• DBA30 lattice with 15 super-periods, each 52m
  long, and 780m circumference
• Super-period two identical cell separated by
  alternating 5m and 8m straights
• Weak bends (0.4T) with damping wigglers to
  achieve ultra-small emittance (0.5 nm with 56 m
  of 1.8T wigglers)
• 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
• Utilization of straights and bending magnets
• 1 long straight for injection with 4 kicker
  magnets
• 2 long straights for fundamental and harmonic RF
  cavities
• Up to 8 long straights for damping wigglers in
  the ultimate configuration
• Five of them with fixed gap, being suitable for
  user beamlines
• 4 long straights for user insertion devices.
• 15 Short straight for user undulators, some with
  canting
• A number of bending magnet for soft X-ray beam
  lines (critical energy 2.4 keV)
• Several bending magnets for IR, far-IR, and THz
  beamlines
• Variable gap wigglers to compensate the change of
  undulator setting by users

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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
Alignment tolerance of multipoles on a girder is
30 ?m, whereas girder-to-girder tolerance is 100
?m
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 gt 50 Hz
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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.
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Storage Ring Parameters
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Storage Ring Parameters (Continue)
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Features of the Storage Ring Design

• A large circumference DBA for small bare lattice
  emittance (2.1 nm)
• The design of the facility mostly depends on the
  well established technology at other storage ring
  light sources
• Alternate Hi-Lo ? straights accommodate various
  requirement for injection, RF, and long damping
  wigglers for machine, and insertion devices for
  users
• The weak bend combined with damping wiggler
  reduces the horizontal emittance to sub nm level
  horizontal
• Robust dynamic aperture (20 mm) and wide
  momentum acceptance (3)
• 24 straights for the hard x-ray beam from
  insertion devices
• A number of dipoles can be used for soft x-ray
  and IR beams
• The level of RF power can be adjust according to
  the development of the facility with additional
  insertion devices and damping wigglers
• Booster injection for better reliability
• 1 meter beam height and good temperature control
  for better stability
• Extensive array of diagnostic devices for better
  control of the beam

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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 of 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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Current Baseline Scope/Specifications

• Linac
• 200 MeV S-band linac
• Turn key procurement
• Linac to booster transfer line with spectrometer
  arm
• Booster
• Air cooled magnet ring, 780 m circumference
• Full complement of magnets, powered in series,
  designed with 20 head-room
• Power supply rated for 1 Hz operation
• PETRA-type 500 MHz room temperature 5 cell RF
  cavity
• In house design, procurement, construction, and
  commissioning
• Booster to storage ring transport line

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Current Baseline Scope/Specifications (Continue)

• Storage Ring
• Water cooled storage ring, 780 m circumference
• All dipole magnets with 60 mm (instead of 35 mm)
  for IR beam extraction
• Dipoles powered in series by one power supply and
  multipoles and correctors by individual power
  supplies.
• Full complement of magnets designed to allow 20
  head room
• Extruded aluminum vacuum chambers a la APS
• Front end for damping wiggler that will
  accommodate high power density radiation
• Scope of user insertion devices not defined,
  subject to the user communitys proposal. Funds
  for devices and beamline front end set aside as
  trust funds
• Initial complement of damping wigglers are to be
  2 ? 7 m fixed gap and 1 ? 7 m variable gap.
  However, only one of each type with 1/3 of length
  are budgeted.
• Two 500 MHz superconducting RF cavities, CESR-B
  or KEK B type, with power source and a passive
  2-cell harmonic cavity will be installed. One
  spare cavity without power source will be
  purchased
• One refrigerator with 700W at 4.5K will be
  procured (turn-key) for the RF system
• Procurement of full complement of diagnostic
  instrumentation is included in the scope
• For control system, EPICS architecture has been
  adopted for now, subject to change

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High Level Project Schedule
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Accelerator System Division Organization
Began working on development of baseline
configuration in January 2006 42 people from
NSLS, C-AD, SMD many of them on part-time base.
Effective FTE for this period 16.5 Many people
from other laboratories (APS, ALS, MIT Bates)
provided help
The organization anticipated for the construction
effort
Accelerator Systems Division Director Deputy
Director
Accelerator Physics Group
Injector System Sub-Project
Mechanical Engineering Group
also support beamline efforts
Storage Ring System Sub-Project
Electrical Engineering Group
RF Group
Insertion Devices Group
Diagnostic Controls Group
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Synopsis of Accelerator Systems Presentations

• X-ray Storage Ring V. Litvinenko
• Nonlinear Dynamics, Tolerances,
• Dynamic and Momentum Aperture J. Bengtsson
• Beam Based Alignment, Beam Stability,
• Orbit Corrections, and Fast Feed-back S.
  Kramer
• Collective Effects S. Krinsky
• Mechanical Sub-Systems S. Sharma
• Magnet Power Supplies G. Ganetis
• Storage Ring Vacuum System H-C Hseuh
• Storage Ring RF System J. Rose
• Insertion Devices T. Tanabe
• Injection System Top-up Injection Scheme,
• Linac, Booster, and Beam Transfer Lines T.
  Shaftan
• Not covered
• Beam Line Front-End Follow experience at APS.
  As of now, details are not defined, waiting for
  the determination of the suit of beamlines.
• Control System EPICS was chosen as the backbone
  for now, but other systems are being studied
• Diagnostics Combination of standard
  instrumentation is planned.

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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, in some case more detailed,
  design of accelerator systems
• Assembled accelerator parameter tables
• We have a innovative design of highly optimized
  synchrotron light source capable of meeting
  requirement articulated in 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