1 BROOKHAVEN SCIENCE ASSOCIATES Hard X-Ray Wiggler Sources at NSLS-II Oleg Chubar X-ray source scientist, XFD, NSLS-II Workshop on Preparation of High-Pressure Beamline Proposal April 29, 2010

2 BROOKHAVEN SCIENCE ASSOCIATES 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 Parameters Basic Parameters of Electron Beam at NSLS-II Energy 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] Relative Energy Spread 0.5 x x x Horizontal RMS Size [μm]* 64 / / / 107 Horizontal RMS Divergence [μrad]* 31 / / / 5.1 Vertical RMS Size [μm]* 4.6 / / 5.2 Vertical RMS Divergence [μrad]* 4.3 / / 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

3 BROOKHAVEN SCIENCE ASSOCIATES Spectral Brightness of NSLS-II Sources

4 BROOKHAVEN SCIENCE ASSOCIATES Spectral Flux of NSLS-II Sources

5 BROOKHAVEN SCIENCE ASSOCIATES Wiggler Comparisons: Brightness NSLS-II e-beam assumed: I = 0.5 A ε x = 0.55 nm ε y = 8 pm

6 BROOKHAVEN SCIENCE ASSOCIATES Wiggler Comparisons: Flux per Unit Horizontal Angle

7 BROOKHAVEN SCIENCE ASSOCIATES Wiggler Comparisons: Peak Flux per Unit Solid Angle

Side Magnets 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-Lab The Structure (E. Wallen, Max-Lab) RADIA model with reduced number of periods Peak Magnetic Field vs Horizontal Position Vertical Magnetic Field on the Axis Peak Magnetic Field vs Vertical Position Period: 61 mm Magnetic Gap: 10 mm

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

11 BROOKHAVEN SCIENCE ASSOCIATES Power Output of NSLS-II IDs Power per Unit Solid Angle Total Power: P DW90 ≈ 67 kW P SCW60 ≈ 34 kW In Vertical Median PlaneIn Horizontal Median Plane

Spectral-Angular Distributions of Emission from 2 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 Trajectories Typical perturbations due to imperfect magnets: ΔB/B max ~3 x (magnet specs: ΔB r /B r <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 DW90SCW60

Example of SCW Parametric Optimization (for SOLEIL High Pressure Beamline) Spectral Flux Per Unit Horizontal and Vertical Angles from Wigglers with Different Periods and Peak Fields at the Constraints on the Total Emitted Power P max = 30 kW, and the Total Length L  2 m E = 2.75 GeV, I = 0.5 A, Sinusoidal Field u  44 mm, N p  42 B max  2.6 T F  1.2 x Ph/s/0.1%bw/mr 2 u  35 mm, N p  44 B max  2.85 T F  1.6 x Ph/s/0.1%bw/mr 2 “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 Limit (gap >10 mm) ACCEL SC Techn. Limit (gap 10 mm) Hybrid/PM Technology Limit (gap 10 mm)  x max = 8 mr  x min = 2 mr Photons/s/0.1%bw/mr 2 at  = 50 keV MAX-Lab / BINP SC Technology Limit (gap >10 mm) ACCEL SC Techn. Limit (gap 10 mm) Hybrid/PM Technology Limit (gap 10 mm)  x max = 8 mr  x min = 2 mr W/mr 2 at 20 keV <  < 100 keV SOLEIL, 2005

In-Vacuum Wiggler W50 3D Magnetic Model (reduced number of periods) On-Axis Magnetic Field On-Axis Flux per Unit Solid Angle [Ph/s/0.1%bw/mrad 2 ] Photon Energy: 50 keV P max = 25 kW; L = 2 m Approx. “Technology Curves” CAD Drawing Magnetic Force vs Gap O. Marcouille EPAC2008

Spectral Flux per Unit Horizontal and Vertical Angles Example of Spectral Performance of Optimized SCW (for SOLEIL High Pressure Beamline) P tot  20 kW for all structures P tot  30 kW, L  2 m for 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.