1 BROOKHAVEN SCIENCE ASSOCIATES

Hard X-Ray Wiggler Sources at NSLS-IIHard X-Ray Wiggler Sources at NSLS-II

Oleg ChubarX-ray source scientist, XFD, NSLS-II

Workshop on Preparation of High-Pressure Beamline Proposal April 29, 2010

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Two main phenomena associated with the process of Emission of Photons by relativistic Electrons in High-Energy Electron Storage Rings:-Radiation Damping (associated with classical emission) tends to reduce Electron Beam Emittance-Quantum Fluctuations (due to discreteness of the emission “events”) result in the increase of Electron Beam Emittance and Energy Spread The “equilibrium” Electron Beam Emittance and Energy Spread is determined by the balance of these two phenomena.

Wiggler Impact on NSLS-II Electron Beam ParametersWiggler Impact on NSLS-II Electron Beam Parameters

Basic Parameters of Electron Beam at NSLS-IIBasic Parameters of Electron Beam at NSLS-IIEnergy 3 GeV

Max. Current 0.5 A

Bare Lattice(without DW)

With 3 x 7 m DW

With 8 x 7 m DW

Horizontal Emittance [nm] 2 0.9 0.5

Relative Energy Spread 0.5 x 10-3 0.89 x 10-3 1.0 x 10-3

Horizontal RMS Size [μm]* 64 / 204 43 / 137 33 / 107

Horizontal RMS Divergence [μrad]* 31 / 9.8 21 / 6.6 17 / 5.1Vertical RMS Size [μm]* 4.6 / 8.2 2.9 / 5.2 2.9 / 5.2Vertical RMS Divergence [μrad]* 4.3 / 2.4 2.7 / 1.5 2.7 / 1.5

* - Low-Beta section / High-Beta section values

If used in dispersion-free straight sections at NSLS-II,

high-field wigglers would further reduce e-beam emittance, however would increase energy spread

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Spectral Brightness of NSLS-II SourcesSpectral Brightness of NSLS-II Sources

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Spectral Flux of NSLS-II SourcesSpectral Flux of NSLS-II Sources

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Wiggler Comparisons: BrightnessWiggler Comparisons: Brightness

NSLS-II e-beamassumed: I = 0.5 A εx = 0.55 nm εy = 8 pm

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Wiggler Comparisons: Wiggler Comparisons: Flux per Unit Horizontal AngleFlux per Unit Horizontal Angle

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Wiggler Comparisons: Wiggler Comparisons: Peak Flux per Unit Solid AnglePeak Flux per Unit Solid Angle

Side Magnets

DW Reference Magnetic and Mechanical Design DW Reference Magnetic and Mechanical Design Magnetic Design with Side Magnets: 90 mm Period, 1.85 T Peak Field at 12.5 mm Gap (T. Tanabe)

Fixed-Gap Conceptual Mechanical Design (proposal of E.Gluskin and E.Trakhtengerg, APS)

3D Magnetic Model (with reduced number of periods) Calculated Magnetic Field (RADIA)

3.5 T SC Wiggler of MAX-Lab3.5 T SC Wiggler of MAX-LabThe Structure (E. Wallen, Max-Lab)The Structure (E. Wallen, Max-Lab)RADIA model with reduced number of periodsRADIA model with reduced number of periods

Peak Magnetic Field vs Horizontal PositionPeak Magnetic Field vs Horizontal Position

Vertical Magnetic Field on the AxisVertical Magnetic Field on the Axis Peak Magnetic Field vs Vertical PositionPeak Magnetic Field vs Vertical Position

Period: 61 mmMagnetic Gap: 10 mm

Figure courtesy of Nikolay Mezentsev (BINP, Novosibirsk, Russia)Figure courtesy of Nikolay Mezentsev (BINP, Novosibirsk, Russia)Example of Commercially-Available Multi-Pole SCWExample of Commercially-Available Multi-Pole SCW

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Power Output of NSLS-II IDsPower Output of NSLS-II IDs

Power per Unit Solid Angle

Total Power:

PDW90≈ 67 kW

PSCW60≈ 34 kW

In Vertical Median PlaneIn Horizontal Median Plane

Spectral-Angular Distributions of Emission from Spectral-Angular Distributions of Emission from 2 x 3.5 m Long DW90 in “Inline” Configuration2 x 3.5 m Long DW90 in “Inline” Configuration

Angular Profiles of DW Emission at Different Photon Energies

1/ ≈ 170 μrad

FWHM Angular Divergence of DW Emission

Spectral Flux per Unit Solid Angle Horizontal Profiles

Vertical Profiles

Wiggler Magnetic Fields and Electron TrajectoriesWiggler Magnetic Fields and Electron Trajectories

Typical perturbations due to imperfect magnets: ΔB/Bmax~3 x 10-3 (magnet specs: ΔBr/Br <10-2)

Suggested Tolerance for Horizontal Trajectory in DW: |x| < 120 μm(max. allowed deviation from “straightness”: 20 μm)

DW90 Modeling Magnetic Field Zoom

Magnetic Field (RADIA)

Horizontal Trajectory: Coordinate

Horizontal Trajectory: Angle

DW90DW90 SCW60SCW60

Example of SCW Parametric OptimizationExample of SCW Parametric Optimization(for SOLEIL High Pressure Beamline)(for SOLEIL High Pressure Beamline)

Spectral Flux Per Unit Horizontal and Vertical Angles Spectral Flux Per Unit Horizontal and Vertical Angles from Wigglers with Different Periods and Peak Fieldsfrom Wigglers with Different Periods and Peak Fields

at the Constraints on the Total Emitted Power at the Constraints on the Total Emitted Power PPmaxmax = 30 kW = 30 kW, and the Total Length , and the Total Length L L 2 m 2 m E = 2.75 GeV, I = 0.5 A, Sinusoidal FieldE = 2.75 GeV, I = 0.5 A, Sinusoidal Field

u 44 mm, Np 42Bmax 2.6 TF 1.2 x 1015 Ph/s/0.1%bw/mr2

u 35 mm, Np 44Bmax 2.85 TF 1.6 x 1015 Ph/s/0.1%bw/mr2

“Technology Limits” Data taken from:- presentations by N.Mezentsev (BINP) and S.Kubsky (ACCEL)- hybrid wiggler simulations by O.Marcouille

MAX-Lab / BINP SC Technology L

imit (gap >10 mm)

ACCE

L SC

Tec

hn. L

imit (

gap

10 m

m)

Hybrid/PM Technology Limit (gap 10 mm)

x max = 8 mr

x min = 2 mr

Photons/s/0.1%bw/mr2 at = 50 keV

MAX-Lab / BINP SC Technology L

imit (gap >10 mm)

ACCE

L SC

Tec

hn. L

imit (

gap

10 m

m)

Hybrid/PM Technology Limit (gap 10 mm)

x max = 8 mr

x min = 2 mr

W/mr2 at 20 keV < < 100 keV

SOLEIL, 2005

In-Vacuum Wiggler W50In-Vacuum Wiggler W503D Magnetic Model

(reduced number of periods)

On-Axis Magnetic Field

On-Axis Flux per Unit Solid Angle [Ph/s/0.1%bw/mrad2]Photon Energy: 50 keVPmax = 25 kW; L = 2 m

Approx. “Technology Curves” CAD Drawing

Magnetic Force vs Gap

O. MarcouilleO. Marcouille EPAC2008

Spectral Flux per Unit Horizontal and Vertical AnglesSpectral Flux per Unit Horizontal and Vertical Angles

Example of Spectral Performance of Optimized SCWExample of Spectral Performance of Optimized SCW(for SOLEIL High Pressure Beamline)(for SOLEIL High Pressure Beamline)

PPtottot 20 kW 20 kW for all structuresfor all structures PPtottot 30 kW, L 30 kW, L 2 m 2 m for all structuresfor all structures

Wiggler for NSLS-II High Pressure Beamline could be similarly optimized to provide maximal flux (per unit solid angle) in users’ spectral domain of interest, while satisfying all accelerator physics constraints.