Stability Requirements for Superconducting Wiggler Beamlines

1. Stability Requirements for Superconducting Wiggler Beamlines Zhong Zhong

2. NSLSII SCW Design Magnet Peak Field B0 : 6 T 3.5 T Period Length λ: 6 cm 6 cm Number of Main Poles (N) : 29 29 number of end poles 4 4 Wiggler Length (L): 0.87 m 0.87 m Critical Energy EC (0.665BE2): 36 keV 21 keV Deflection Parameter ( K=0.93B0λ ): 33.6 19.5 Radiated Power at 500mA (3.9B02LI ): 61 kW 21 kW Fan size (2K/): 11.4 milli-radians 6.7 milli-radians Ampli. e- oscillation (X0= λw K/(γπ)) 0.11 mm 0.063 mm horiz. beam chamber aperture (mm) ? ? vert. beam chamber aperture (mm) 10 10 magnetic (iron) gap (mm) 15 15 Table I: specifications of the 6 T wiggler and the alternative 3.5 T wiggler Facility Manufacturer Field(T) Period (cm) # full-field poles NSLS X17 Oxford 6 17.4 5 BESSY II Novosibirsk 7 14.8 13 CLS Novosibirsk 4.2 4.8 25 ELETTRA Novosibirsk 3.6 6.4 45 MAX lab ? 3.5 6.1 47 Table  II. A partial list of working super-conducting wigglers similar in specifications

3. NSLSII SCW Performance Flux of the NSLS-II superconducting wiggler, compared with that of NSLS-II bending magnets, damping wigglers, and an alternative superconducting wiggler (W60 in NSLS-II CD0 proposal) with 3.5 T peak field.

4. Center Hutches Vertical focusing mirror 2-D focusing sagittally bent Laue monochromator Sagittal focusing tunable Laue monochromator Side Hutches NSLSII SCW Beamlines • Beamline Optics & Instrumentation: • 2 fixed-wavelength side stations and • 2 center stations, white beam or focused monochromatic beam, or both • 6-circle Huber diffractometer with bent Laue analyzer for high-resolution diffraction experiments.

5. NSLSII SCW Experimental Programs • Angular dispersive x-ray diffraction (ADXD) • Large volume press • Diamond Anvil cell • Diffuse scattering • Powder diffraction • Energy-dispersive x-ray diffraction (EDXD) • Large volume press • Diamond Anvil cell • Strain mapping • Imaging and radiation therapy research • Diffraction Enhanced Imaging • Microbeam Radiation Therapy

6. Sagittal bending enables sagittal-focusing Anticlastic bending Allows meridional focusing Lattice strain increases integrated reflectivity by 1-2 orders of magnitude compared to perfect crystal Second Crystal First crytal ADXD, large samples • large volume press, diffuse scattering, powder diffraction, sample size ~ 1 mm. • x-rays are focused by a sagittal focusing Laue monochromator at a magnification of approximately unity. • A position stability of 10% of sample size results in a source-position stability of approximately 100 µm horizontally and vertically. • Vertical angular stability: 10 µrad • A wavelength stability of 10-4 • Si 111 monochromator at a Bragg angle of approximately 0.1 rad

7. EDXD • Strain mapping, deformation experiments, diamond anvil cell, large volume press • Most challenging for orbit stability: use the peak position as a figure-of-merit. • Angle of the incident beam is defined by a fixed slit and the source • Diffraction angle (2) typically being 0.1 rad. • To obtain 10 micro-strains (10-5 d/d) accuracy, the incident angle as defined by the slit and source should be maintained to within 10-6 rad. • The source and beam-defining slit being 50 meters apart, the vertical source position should have a stability of 5010-6 meters, or 50 µm.

8. ADXD, small samples • Diamond anvil cell, sample size: a few microns • Source position stability of 100 µm horizontally and vertically. • K-B mirrors (at a magnification of approximately 100:1) are used to focus the x-rays. • A position stability of 1 µm at the sample • Vertical angular stability: 10 µrad • A wavelength stability of 10-4 • Si 111 monochromator at a Bragg angle of approximately 0.1 rad

9. Synchrotron Radiography Detector Object Double Crystal Monochromator Synchrotron Beam Detector Synchrotron DEI Setup Analyzer Object Imaging and radiation therapy • DEI and micro-CT, micro-beam radiation therapy (MRT) • The distance between the subject and detector is typically 1 meter, and a resolution of ~1 µm is typically desirable. • 50 meters source-to-subject distance, • The source position should be stable to within 50 µm horizontally and vertically.

10. Summary: superconducting wiggler • The source position should be stable within 50 µm horizontally and vertically • Source vertical angle should be stable within about 10 µrad. • There is no requirement on source horizontal angle due to the large horizontal divergence afforded by a superconducting wiggler.