High Pressure Diffraction and Spectroscopy at Bending Magnet Beamline Changyong Park
Beamline Staffs • Beamline operation and user support: • Changyong Park: beamline scientist • Dmitry Popov: beamline scientist • Daijo Ikuta: beamline associate • Hongping Yan: post-doc associate • Equipment support: • Curtis Kenney-Benson: beamline associate • Beamline maintenance: • Eric Rod: beamline technician • Arun Bommannavar: beamline control scientist • User administration: • Freda Humble
16BM-D • General micro-X-ray diffraction and x-ray absorption spectroscopy dedicated to high-pressure physics, chemistry, materials science, and earth and planetary sciences • Optimized for DAC, typically with ϕ ≥ 50 μm gasket (≤ 100 GPa) • 12 μm (v) x 5 μm (h) in FWHM • ~5 x 108 photons/sec at sample (at E = 30 keV) • 6-40 keV normal operation • Up to 60 keV with special request • Powder and single crystal • Sample temperature ranges from 4K to ~1,000K
Beamline Schematic 4 m 40 m from the source 0.6 m Post-mono slits Guard slits Pre-mono slits Vertical KB mirror Clean-up pinhole Si 111 Monochromator Horizontal KB mirror Beamstop E = 6-60 KeV Δ= ~100 μm fixed exit Area Detector 1 m long Cr+Pd mirror 1.5 mrad (45 keV) 200 mmm long Cr+Rh mirror 16BM-D 16BM-C
Equipment • MAR345 Image Plate, MAR165 CCD (APS Detector Pool), Pilatus 1M, and Pilatus 100K • Gearbox or Membrane Diaphragm • On-line Ruby Spectroscopy • Cryostat (4 K He, 10 K LN2) • Resistive heating with PID control • Pneumatic Ion-Chamber Mount • All equipment supports are dedicated to remote controls of the sample pressure and temperature.
Types of experiments suitable at BM-D • Powder diffraction of high scattering (high-Z) materials • Experiments that require various energies • anomalous scattering • low energy for higher resolution in d-spacing • high energy for larger Q coverage • Single crystal x-ray diffraction • Transmission mode XANES (>6 keV) • High-resolution powder x-ray diffraction (with rotating 2θ arm setup, ΔQ/Q = 10-3) • Cryostat (down to 4 K with He flow) • Resistive heating (typically up to 1,000 K) • Static compressional studies at wide range of sample temperature
Micro-XRD and XANES • Simultaneous probe of atomic and electronic structure changes at the same sample condition • Highly reproducible and easily accessible monochromator makes this possible
Improvement Plan • The low incident flux (~5 x 108 photons/sec at 30 keV) is currently the limiting factor to the efficiency. • The distance from the source and the small horizontal mirror acceptance only taking 0.3 mm is the main reason. • Possible improvement of beam flux by :
Concluding Remarks • The recent publication record of 16BM-D (2011: 19, 2012: 28 peer-reviewed publications, ~15-20% high profile journals) outperforms the average BM beamline at the APS. • 16BM-D not only off-loads the oversubscription of the ID beamline, but adds new capabilities in anomalous scattering, x-ray absorption, large Q single crystal diffraction, and high Q-resolution. • Stability of optics and integrity of support equipmentarethe key factors of the high level performance. • The upgrade of optics will promote the more effective use of APS beamtime.