Stability Requirements for Superconducting Wiggler Beamlines Zhong Zhong

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

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.

Sagittal focusing tunable Laue monochromator 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. Center Hutches Side Hutches 2-D focusing sagittally bent Laue monochromator Sagittal focusing tunable Laue monochromator Vertical focusing mirror

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) Strain mapping Imaging and radiation therapy research Diffraction Enhanced Imaging Microbeam Radiation Therapy

ADXD, large samples First crytal Second Crystal 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 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

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.

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

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. Synchrotron Beam Double Crystal Monochromator Object Detector Analyzer Synchrotron DEI Setup Synchrotron Radiography

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.