摘要:

A design of a total electron yield detector to collect x‐ray absorption fine structure spectra between 80 K and room temperature is described. In addition, a three‐stage goniometer setup has been incorporated into the detector to facilitate manipulation of the sample. The results of simple linearity checks to investigate the detector’s electrical performance are presented. Finally, the detector’s thermal stability is discussed. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144489

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A cylindicral cavity of TE111mode with an aperture of 3 mm in diameter has been used to measure the electron paramagnetic resonance (EPR) spectrum of a large object placed over the aperture. EPR spectra of a precious fossil of a dinosaur tooth piece and a fossil bone of the Machikane Alligator were measured nondestructively in addition to a jadeite sculpture, a pearl and turquoise necklace, a large turmaline, a star ruby, and ceramic pottery. Thus, EPR can be a nondestructive tool to detect forgery and to test the authenticity in art as well as to allocate ancient objects in archaeological provenance study. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144490

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A versatile and modular nuclear magnetic resonance (NMR) instrument is described that is particularly suited for the study of moisture transport in porous media such as various building materials in which moisture can give rise to several kinds of damages. Quantitative measurements of one‐dimensional moisture profiles and their time evolution can be performed on cylindrical samples having a diameter up to 20 mm with a spatial resolution better than 1 mm. Water absorption and drying experiments on various building materials demonstrate that the instrument can also be used for materials containing relatively large amounts of magnetic impurities, which until now were hardly accessible by NMR techniques. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144491

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A Windows application has been developed for management and operation of beam instruments such as electron or ion microscopes. It provides a facility that allows an operator to manage a complicated instrument with minimal effort, primarily under mouse control. The hardware control components used on similar instruments (e.g., the scanning transmission electron microscopes in our lab), such as toggles, buttons, and potentiometers for adjustments on various scales, are all replaced by the controls of the Windows application and are addressable on a single screen. The new controls in this program (via adjustable software settings) offer speed of response and smooth operation providing tailored control of various instrument parameters. Along with the controls offering single parameter adjustment, a two‐dimensional control was developed that allows two parameters to be coupled and addressed simultaneously. This capability provides convenience for such tasks as ‘‘finding the beam’’ and directing it to a location of interest on the specimen. Using an icon‐based display, this Windows application provides better integrated and more robust information for monitoring instrument status than the indicators and meters of the traditional instrument controls. As a Windows application, this program is naturally able to share the resources of the Windows system and is thus able to link to many other applications such as our image acquisition and processing programs. Computer control provides automatic protection and instant diagnostics for the experimental instrument. This Windows application is fully functional and is in daily use to control a new type of electron microscope developed in our lab. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144492

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A quantitative thermionic projection microscope, employing computer image processing, is described. In this system, thermionic emission from a single‐crystal hemispherical cathode is projected onto a phosphor screen and the resulting image is digitized by means of a video camera. Single‐plane effective work functions for the highest emitting planes of the cathode may be measured to within a tenth of an electron volt. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144493

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A highly sensitive displacement sensor for atomic force microscopy is described which enables one to measure the relative displacement of the tip from a sample surface. The sensor is based on the differential heterodyne interferometer formed between the reflections from the microscope cantilever backside and the sample surface. As a result of using an optical common‐path construction, the sensor is essentially insensitive to the mechanical vibration, and achieves high stability at low frequencies, even though there are certain restrictions imposed by the reflection from the examined surface and the variable deflection mode. Images are presented demonstrating the atomic resolution of mica and graphite. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144494

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A new force sensor element based on multilayer thin film technology and adapted for optical readout in a conventional scanning force microscope has been developed. The use of polymers as cantilever materials enables the introduction of mechanical properties otherwise not accessible with microfabrication based on Si technology. The fully batched fabricated cantilevered force transducer is based on the photoresist novolak and incorporates an integrated EBD tip. Bending experiments on microstructures indicate that the Young’s modulus of novolak is about two orders of magnitude lower than for Si. Therefore, in using a cantilever design similar to that with Si it is possible to fabricate more flexible structures from polymeric materials. The new force sensors have been tested and their performance has been evaluated on different samples. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144495

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The operating criteria of analog and digital methods for obtaining field emission fluctuation autocorrelation functions for the determination of surface diffusion coefficients are discussed and the strengths and limitations of both methods pointed out. Two digital systems, one using a spiraltron for pulse counting, the other a fast phosphor‐photomultiplier combination for the same purpose, are described and test results presented. Some results obtained digitally for W self‐diffusion on W(123) and for oxygen diffusion on W(110) are presented and shown to agree with previous results obtained by the analog method. To illustrate the potential of the digital method for obtaining very smallDvalues results for the diffusion of H on Re(112¯0) at 80 K are also presented. For this case &tgr;0=13 s, andD=1×10−14cm2 s−1. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144496

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The electron optical properties of an electrostatic triplet quadrupole lens used as an electron beam transport device were reexamined, both analytically and by computer simulation, in order to derive limits on the choice of the design parameters of the lens. Furthermore, computer simulation of electron trajectories through a single quadrupole lens, and comparison with experimental results obtained by other authors, have led to a graphical relation between the fringing field end correction and the aspect ratio of the lens. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1144497

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We present a differential retarding potential (DRP) method for improving the kinetic energy resolution of a reactant ion beam for scattering experiments. This method allows ion‐molecule reaction absolute total cross‐section measurements to be performed down to thermal energies using the simple electrostatic aperture ion lenses of a tandem quadrupole mass spectrometric ion‐molecule reaction apparatus, even though the reactant ions are formed originally with a broad kinetic energy distribution. To illustrate the principle of the DRP method, examples are given for its application to reactant ion beams prepared in an electron impact ion source and in an ion‐molecule reaction ion source. ©1994 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145217

出版商:AIP    

年代:1994

数据来源: AIP