摘要:

This article describes the use of the Fabry–Perot laser interferometer in the fringe mode to measure velocities of fast‐moving reflecting surfaces, and includes a review of previously published work. We begin by describing the theory of the Doppler shift that applies to these situations, and include an experimental test of whether surface normal direction affects Doppler shift. Formulas are derived for the analysis of the effects of shocked, dispersive, moving transparent media on velocity measurements, including expressions for the velocity of light in a moving medium with moving boundaries. The Fabry–Perot method is compared with other techniques such as the VISAR interferometer. We then describe in detail a standard configuration developed at our facilities, discuss other configurations using optical fibers and more than one cylinder lens, and describe a new laser amplifier developed specifically for velocimetry. Methods of alignment, instrument calibration, surface preparation, and operation are included. Next, we present several methods of analysis, the choice of which depends on the absolute accuracy required, and examine many sources of possible error. These analytical techniques allow the motion of surfaces of reflectivity of at least 1% to be measured with an absolute precision of 0.5%. Time resolution can be a few nanoseconds, and is traded off for velocity resolution. One can make continuous velocity records of surfaces whose reflectivity under shock loading decreases to less than 1% of its initial value. We have simultaneously recorded three distinct velocity–time histories without ambiguity.

ISSN:0034-6748    

DOI:10.1063/1.1140014

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The design, construction, and operation of a high‐resolution electron energy‐loss spectrometer incorporating a multidetector of 96 discrete anodes are described. In conjunction with temperature and pressure perturbations, this fast data‐acquisition spectrometer allows studies of surface kinetics and reaction mechanisms by accumulating spectra in as fast as 2 ms. A comprehensive hardware and software system has been developed that permits experimental control and data acquisition with an LSI 11/23 microcomputer. A routine increase in data‐acquisition speed of ≊10, when compared to a conventional electron energy‐loss apparatus, has been achieved when the spectrometer is operated with 10–20‐meV resolution.

ISSN:0034-6748    

DOI:10.1063/1.1140015

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The design and construction of an imaging bandpass electron energy analyzer which operates in the intermediate magnetic field of a photoelectron spectromicroscope is described. Image electrons injected parallel to the magnetic field are guided, using crossed magnetic and nonuniform electrostatic fields, to a low‐pass electron mirror and subsequently a high‐pass retardation filter. The nonuniform electrostatic fields compensate for the energy‐dependent dispersion of the crossed fields. A bandwidth‐limited photoelectron image demonstrates the spatial integrity of the image after passage through the image bandpass filter. The performance of the device as an energy analyzer is assessed. An energy resolution of less than 30 meV is demonstrated and thermionic electron spectra are presented with electron energies ranging from 10 to 200 eV with a 250‐meV bandwidth. Area‐selected photoelectron spectra from Au and W show UPS and XPS performance of the device. In the case of Au, the spectrum was obtained from a 400‐×400‐nm area.

ISSN:0034-6748    

DOI:10.1063/1.1140016

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A new method is described which allows the accurate absolute calibration of an electron‐spin polarization analyzer. It is based on measuring spin–orbit‐induced scattering asymmetries and simultaneous polarization analysis of the scattered electrons in elastic electron scattering. It is shown how the effective Sherman function of a classical high‐energy Mott detector can be determined easily to within better than ±2%. The method is applicable to other types of electron‐spin polarization detectors as well.

ISSN:0034-6748    

DOI:10.1063/1.1139964

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A scanning soft x‐ray microscope has been built and operated at the National Synchrotron Light Source. It makes use of a mini‐undulator as a bright source of 3.2‐nm photons. An electron beam fabricated Fresnel zone plate focuses the beam onto the specimen, which is scanned under computer control. The scanning stage can be moved by both piezoelectric transducers and stepping motors, and the location is monitored by a high‐speed laser interferometer. X rays transmitted through the specimen are detected using a flow proportional counter. Images of biological specimens and of artificial microstructures have been made with resolution in the 75–100‐nm range. Acquisition time for 256×256‐pixel images is about 5 min.

ISSN:0034-6748    

DOI:10.1063/1.1139965

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

In this paper a simple and inexpensive angular positioning apparatus is described which can be applied to measurements of x‐ray reflectivity and extended x‐ray absorption fine structure (EXAFS) at glancing angles of incidence. An efficient interactive alignment procedure is discussed and the performance of the device is given.

ISSN:0034-6748    

DOI:10.1063/1.1139966

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A rapid temperature‐jump (T‐J) device was designed for the kinetic measurements of small‐angle x‐ray scattering from solutions of biological macromolecular systems. The dead time of the apparatus is reduced to a few hundred milliseconds. The structural change of biological macromolecules in solutions can be monitored in the time scale of a few hundred milliseconds by the synchrotron small‐angle x‐ray scattering with a combination of a CAMAC data‐acquisition system and the present T‐J apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1139967

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The design and performance of a high‐precision X–Y stage which uses a unique type of flexure pivots is described. Performance achieved with a symmetrical arrangement of four arm/pivots for each axis is such that pitch, roll, and yaw is less than one arcsecond for 1×1‐mm stage motion. Vertical vibration during stage motion is less than 2.5 nm peak to valley, with the major limitation being insufficient decoupling from the drive mechanism. Also described is the application of the stage for performing microtopographic mapping with a stylus transducer.

ISSN:0034-6748    

DOI:10.1063/1.1139968

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A new apparatus has been constructed for high‐precision hyperfine structure measurement of atomic ions by laser‐radio‐frequency double‐resonance technique involving a slow ion beam and a laser in collinear geometry. The low ion energy (1–1.5 keV) leads to longer interaction time with the applied rf field. Consequently, extremely narrow linewidths of ∼60 kHz have been observed for the first time in such systems. The apparatus has been used for the measurement of hyperfine structure of the 4f7(8S0)5d9D02,3,4,5metastable levels in151Eu+and153Eu+. The magnetic dipole and the electric quadrupole hyperfine constants,AandB, respectively, have been determined with higher precision (2–3 orders of magnitude).

ISSN:0034-6748    

DOI:10.1063/1.1139969

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A computerized spectrophotometer using an acousto‐optic tunable filter is described. The equipment operates between 400 and 700 nm and is applied, for example, to reflected color measurement.

ISSN:0034-6748    

DOI:10.1063/1.1139970

出版商:AIP    

年代:1988

数据来源: AIP