X-ray microprobe: The next step in microcharacterization

The combination of high brilliance of third generation synchrotrons and advanced x-ray microfocusing optics will revolutionize microcharacterization. Kirkpatrick-Baez elliptical mirrors, zone plates, and condensing capillaries have all achieved intense submicron focused beams. Other focusing options are also under study including Bragg-Fresnel optics and compound refractive lenses. The intense micron-scale beams from advanced x-ray optics on third generation sources will provide unique information about the elemental and crystallographic distribution in samples and will enable a variety experiments previously unimaginable. X-ray microbeams can be used to map elemental distributions in two and three dimensions and can be used to study the phase, texture, and strain distributions of inhomogenous samples in two and three dimensions

Modeling of X-ray beamlines and devices

X-ray beamlines on synchrotron sources are similar in size and complexity to beamlines at state-of-the-art neutron sources. The design principles, tools, and optimization strategies for synchrotron beamlines are also similar to those of neutron beamlines. The authors describe existing design tools for modeling synchrotron radiation beamlines and describe how these tools have evolved over the last two decades. The development of increasingly powerful modeling tools has been driven by the escalating cost and sophistication of state-of-the-art beamlines and by a world-wide race to exploit advanced synchrotron radiation sources

Neutron Halo Isomers in Stable Nuclei and their Possible Application for the Production of Low Energy, Pulsed, Polarized Neutron Beams of High Intensity and High Brilliance

We propose to search for neutron halo isomers populated via $\gamma$-capture in stable nuclei with mass numbers of about A=140-180 or A=40-60, where the $4s_{1/2}$ or $3s_{1/2}$ neutron shell model state reaches zero binding energy. These halo nuclei can be produced for the first time with new $\gamma$-beams of high intensity and small band width ($\le$ 0.1%) achievable via Compton back-scattering off brilliant electron beams thus offering a promising perspective to selectively populate these isomers with small separation energies of 1 eV to a few keV. Similar to single-neutron halo states for very light, extremely neutron-rich, radioactive nuclei \cite{hansen95,tanihata96,aumann00}, the low neutron separation energy and short-range nuclear force allows the neutron to tunnel far out into free space much beyond the nuclear core radius. This results in prolonged half lives of the isomers for the $\gamma$-decay back to the ground state in the 100 ps-$\mu$s range. Similar to the treatment of photodisintegration of the deuteron, the neutron release from the neutron halo isomer via a second, low-energy, intense photon beam has a known much larger cross section with a typical energy threshold behavior. In the second step, the neutrons can be released as a low-energy, pulsed, polarized neutron beam of high intensity and high brilliance, possibly being much superior to presently existing beams from reactors or spallation neutron sources.Comment: accepted for publication in Applied Physics

On controlling gravitational distortions in long synchrotron x-ray mirrors

X-ray mirrors for synchrotron radiation beamlines must have low roughness and small figure errors to preserve source brilliance. Gravitationally-induced slope errors can be particularly detrimental for large vertically-deflecting mirrors on ultra-high brilliance third generation beamlines. Although mirror support can greatly reduce gravitational distortions, in some cases mirror support can complicate dynamic bending. We discuss techniques for controlling gravitational distortions with particular emphasis on removing gravitational distortions from simple bendable mirrors. We also show that in beamlines with parallel mirrors, gravitation induced slope errors can be canceled through the mirror pair; gravitation induced slope errors of the first mirror can be canceled by matching slope errors with opposite signs on the second mirror

ORNL beam line optics: a presentation for the NSLS x-ray PRT meeting November 17-18, 1980

After considering numerous focusing and monochromatizing schemes, we have settled on an optical geometry which we consider near ideal. The main optical element is a conical crystal which focuses 15 mrad of horizontal divergence from 2 to 20 keV, and which focuses 12 mrad of horizontal divergence up to 40 keV. A model of the key conical crystal bender has been designed and is out for bids. We plan to test the model optically and then with synchrotron radiation from Cornell. Should the conical crystal geometry prove too difficult, we are prepared to fall back on the BNL paraboloidal mirror concept

A simple cantilevered mirror for focussing synchrotron radiation

A large cantilevered mirror was constructed to focus the vertical divergence from a synchrotron radiation source. The advantages of this mirror are its compactness, simple bending device, simplicity of construction, and good thermal contact to structures outside the vacuum. The central portion of the mirror is supported with variable loading springs to reduce gravitational sag. The figure and thermal stability of the mirror have proven to be excellent, though the focusing is limited by the roughness of the mirror-surface. This paper describes the design, construction, and performance of the mirror

X-Ray microprobe characterization of materials: the case for undulators on advanced storage rings

The unique properties of X-rays offer many advantages over electrons and other charged particles for the microcharacterization of materials. X-rays are more efficient in exciting characteristic X-ray fluorescence and produce higher fluorescent signals to backgrounds than obtained with electrons. Detectable limits for X-rays are a few parts per billion and are 10/sup -3/ to 10/sup -5/ less than obtained with electrons. Energy deposition in the sample by X-rays is 10/sup -3/ to 10/sup -4/ less than for electrons for the same detectable concentration. High-brightness storage rings, especially in the 6 GeV class with undulators, will be approximately 10/sup 3/ brighter in the X-ray energy range from 5 keV to 35 keV than existing storage rings and provide for X-ray microprobes that are as bright as the most advanced electron probes. Such X-ray microprobes will produce unprecedented low levels of detection in diffraction, EXAFS, Auger, and photoelectron spectoscopies for both chemical characterization and elemental identification. These major improvements in microcharacterization capabilities will be wide-ranging ramifications not only in materials science but also in physics, chemistry, geochemistry, biology, and medicine

Focusing optics for a synchrotron x radiation microprobe

We propose two constant deviation and energy-tunable fluorescent microprobe optical designs which efficiently use x rays available from ending magnets and insertion devices of synchrotron radiation sources. The simpler system consists of a cylindrically bent multilayer to focus the vertical opening angle by in-plane scattering, a fixed radius cylindrically curved multilayer which sagittally focuses the horizontal divergence, and a pinhole to further reduce the beam to microprobe dimensions. A more versatile system has a pair of flat nondispersively arranged diffracting optics followed by crossed elliptical mirrors. These nondispersive combinations can produce a fixed-exit beam. We compare the relative intensity with other optical systems