A Device for Selecting and Rejecting X-ray Harmonics

DESCRIPTION (provided by applicant): Synchrotron radiation is an important tool for structural biological studies using X-ray diffraction, X-ray scattering, and X-ray absorption spectroscopy. The quality of data often depends critically on beam spectral quality. The technical limitations (e.g. energy range) of beamlines can make or break experiments. In this application we propose to optimize, design, construct, and test over a wide range of energies a novel, inexpensive, easy to align device ("beam cleaner"). The device has several benefits: improving X-ray beam spectral quality; extending (e.g. tripling) the useful energy range of existing beamlines at third generation synchrotron radiation sources by selecting specific harmonics for experimental use; passively compensating for vertical beam motion as the monochromator angle is changed; and focussing the beam. Beam cleaners offer the potential to simplify new beamline designs by permitting use of channel-cut monochromators in vacuum, followed by a beam cleaner arranged so as to passively compensate for vertical beam motion, without the need for precise in-vacuum mechanics. This device also potentially can be used as a non-beam-hardening variable attenuator for experiments on radiation sensitive biological samples at intense third generation sources, and the devices also appear to be applicable to laboratory research.