We have designed and tested a novel linear actuator system with 1-angstrom closed-loop control resolution and 50-mm travel range. There are two major ultraprecision motion control techniques that have been applied to this actuator: A novel laser Doppler encoder system with multiple-reflection Optics. A specially designed high-stiffness weak-link mechanism with stacked thin metal sheets having sub-Angstrom driving sensitivity with excellent stability. In this paper, we present the system design and test results of this linear actuator. Applications of this new actuator system are also discussed. -Å
The design principles, construction and characterization of a 4-bounce dispersive crystal monochromator is discussed. This monochromator is designed to reduce the bandpass of synchrotron radiation to 10 - 50 meV level, without sacrificing angular acceptance. This is achieved by combining an asymmetrically-cut, low order reflection with a symmetrically-cut, high order reflection in a nested configuration. This monochromator is being used as a beam conditioner for nuclear resonant scattering of synchrotron radiation to produce x-rays with (mu) eV-neV resolution in the hard x-ray regime.
The insertion-device-based, third-generation, synchrotron radiation sources now under construction in Europe, the USA, and Japan bring new opportunities and challenges in the design and manufacture of x-ray optics. These high brightness sources provide new opportunities to overcome some of the outstanding problems associated with nuclear resonant monochromatization of synchrotron radiation. New methods such as polarizing monochromators, and zone plates provide alternative methods for production of (mu) eV-neV resolution in the hard x-ray regime. The design principles, and characterization, and performance of crystal monochromators and of nuclear coherent scattering optics, including Grazing Incidence Anti Reflection (GIAR) films, multilayers, zone plates, as well as single crystals are discussed.
A nuclear monochromator using grazing incidence anti-reflection (GIAR) films of 119SnO2 coated on a Pd backing mirror was designed, fabricated and characterized. 119SnO2/Pd/quartz GIAR films were synthesized by a magnetron reactive sputtering technique. The films were characterized by x-ray scattering of 23.87 keV synchrotron radiation source. From the measurement of off-resonance reflectivity and the simulation of the resonant nuclear reflectivity, approximately 0.8 reflectivity with 10-2 electronic reflectivity and an energy band width approximately 100 (Gamma) where (Gamma) is a natural line width, at a 2 mrad incident beam angle would be expected. The requirements and alternative methods to improve performance of a GIAR film nuclear monochromator were discussed.