Stability Requirements for Superconducting Wiggler Beamlines

Zhong Zhong

NSLSII SCW Design

Magnet Peak Field B0 : 6 T 3.5 TPeriod Length λ: 6 cm 6 cmNumber of Main Poles (N) : 29 29number of end poles 4 4Wiggler Length (L): 0.87 m 0.87 mCritical Energy EC (0.665BE2): 36 keV 21 keVDeflection Parameter ( K=0.93B0λ ): 33.6 19.5Radiated Power at 500mA (3.9B02LI ): 61 kW 21 kWFan size (2K/): 11.4 milli-radians 6.7 milli-radiansAmpli. e- oscillation (X0= λw K/(γπ)) 0.11 mm 0.063 mmhoriz. 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 polesNSLS X17 Oxford 6 17.4 5BESSY II Novosibirsk 7 14.8 13CLS Novosibirsk 4.2 4.8 25ELETTRANovosibirsk 3.6 6.4 45MAX lab ? 3.5 6.1 47Table  II. A partial list of working super-conducting wigglers similar in specifications

NSLSII SCW Performance

1012

1013

1014

1015

1016

Flu

x [p

hoto

ns/s

ec/0

.1%

bw

/mra

d]

10 eV 100 eV 1keV 10keV 100keV

Photon Energy

Wigglers

VUVhcrit

NSLS-II DW100-1.8T,B=1.8T, 100mm,L=7m, K=16.8

NSLS-II, 25m-radius bend,B=0.4T, Ec=2.39keV

Bending magnets

NSLS-II DW100-1.8T,B=1.8T, 100mm,L=2m, K=16.8

NSLS-I 6.88m-radius bend,B=1.36T, Ec=7.09keV

NSLS-II SCW,B=3.5T, 60mm,L=1m, K=19.6

NSLS-II SCW,B=6T, 60mm,L=1m, K=33.6

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.

Center Hutches

Side Hutches

2-D focusing sagittally bent Laue monochromator

Sagittal focusing tunable Laue

monochromator

Vertical focusing mirror

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.

NSLSII SCW Beamlines

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

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

First crytalSecond Crystal

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 5010-6 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

ObjectAnalyzer Synchrotron DEI Setup

Synchrotron RadiographyDetector

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.