摘要:

A Helmholtz probe made from two parallel‐plate bracelet resonators for nuclear magnetic resonance imaging experiments possesses a number of advantages such as high unloaded quality factor, absence of tuning capacitors, low cost, accessibility, easy to design, patient comfort, etc. Energy transfer to and from the probe is assured by a one‐turn loop magnetically coupled to the coils, disposing the pair of current feed lines needed for conventional Helmholtz coils. Design procedure and a practical example are given, showing good agreement between calculated and experimental results. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146078

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A semiautomatic atomic force microscope for imaging in solution is described. With this new design, the laser beam is focused into a fine line, and a rotating mirror is used to deflect the optical signal onto a fixed photodetector. The alignment is now operated with stepper motors. Combined with a three stepper motor sequential advancement for tip engagement, the operation of the atomic force microscope for imaging in solution is much simplified, and the crashing of the tip is largely avoided. Since all controls are now coupled with stepper motors, this system is fully compatible with automation and operation in a self sealed temperature controlled chamber. The design and the construction of this system is relatively simple and can be fitted into any existing system. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146079

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Scanning force microscopes (SFMs) are sometimes used to obtain a force curve, which shows the force variation as a function of tip–sample distance. In the force curve measurement, if the spring constant of the force detecting lever is small, the measured force curve has discontinuity and is different from the true force curve. In this paper, we present a new type of force balancing force sensor built in SFM. This force sensor employs an optical lever for detecting the rotation of the lever and two electrostatic force actuators with transparent electrodes. This sensor has two operating modes;withandwithoutfeedback. In the feedback mode, the force detecting lever is balanced with the electrostatic force. This system has the effect of enlarging the effective spring constant of the whole sensor. In the nonfeedback mode, this sensor acts as an ordinary force sensor. By using this sensor in both modes we will show the effectiveness of the force feedback in force curve measurements. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146080

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A spin rotator for observing magnetic domains with all three magnetization components of a sample surface by spin‐polarized scanning electron microscopy (spin SEM) has been developed. The spin rotator is placed between the sample and the spin detector in a spin SEM, and can rotate the polarization vector of secondary electrons by &pgr;/2. Although the spin detector itself can detect only two independent polarization components, the rotation of polarization makes third‐component detection possible. The conventional spin rotator, which is a well‐known energy filter named a Wien filter, has been much improved to have a large focusing area by using hyperbolic cylindrical pole pieces as a magnet and several auxiliary electrodes. As a result, all the secondary electrons emitted from the area of a surface as large as 1 mm in diameter can pass the spin rotator with uniform spin rotation, and the distribution of all three magnetization components can be imaged successfully by spin SEM. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146081

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new mechanical system and a convenient piezoelectric driven Kelvin probe for the measurement of the contact potential difference (CPD) under ultrahigh vacuum are described. Charging effects on CPD measures are discussed. The probe is small (2.2 mm diam) and allows cartography of the surface. The mechanical system is frictionless so the distance between the sample and the probe can be maintained constant and at a low value (≊20 &mgr;m). By elimination of charging effects, reliable and reproducible results can be obtained within ±10 mV. The system is tested on gold vicinal surfaces. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146082

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A method and a device to measure temperature using bicolor optical pyrometry are presented. The device is equipped with an optical fiber probe designed forinsitumeasurements in severe conditions (high temperatures, difficult accessibility, and electromagnetic fields). The directional monochromatic emissivities, at two wavelengths 1.3 and 1.55 &mgr;m, were deduced from reflection measurements. The device can be used for opaque Lambertian surfaces in the temperature range from 500 to 2500 °C. The method was put in practice on rare‐earth metal oxide powders at temperatures up to 1000 °C. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146083

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Results for the calibration and testing of a 16‐beam grating‐based division‐of‐amplitude photopolarimeter, that take into account the effect of source polarization and imperfections of the polarization state generator, are presented. A model is developed to analyze the elements of the instrument matrix obtained from calibration. The experimental results are compared with the predictions of the model, and useful information is extracted about the optical elements of the system. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146476

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present an improved design for far‐infrared (FIR) circular polarizers used in a lightpipe transmission system for magneto‐optical experiments. A peak efficiency of nearly 100% is achieved for FIR laser radiation by reducing the multiple reflections within the polarizer system, as well as scattering from the walls of the lightpipe. Broadband low‐resolution measurements are less susceptible to errors due to multiple reflections, but incorporation of these improvements is still found to reduce systematic errors due to the reflection from the sample. Also, we have measured the low temperature index of refraction of quartz and find significant disagreement with published values for frequencies below 100 cm−1. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146084

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Optical beam deflection is a simple and reliable method for the detection of small displacements. This paper describes its application to the measurement of the displacement of the membrane of a condenser microphone, where the displacement is induced by supplying an alternate voltage to the transducer terminals. A sensitive reconstruction of the dynamic deformation of a microphone membrane in a wide frequency range is obtained. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146085

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A special arrangement of electrodes and a differential system were employed for measuring the lateral conductance of Langmuir monolayers. Such an experimental system obviates the major difficulties inherent in this type of measurement which may have prevented the enhanced conductance from being observed in recently published data. It is shown unequivocally that both dc and ac conductances of monolayers increase when the monolayer is compressed beyond a critical density, thus resolving a controversy from the literature. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146022

出版商:AIP    

年代:1995

数据来源: AIP