摘要:

A new thermal, supersonic cluster source for the investigation of binary metal cluster formation at thermodynamically well-defined expansion conditions is described. The source consists of two separately heatable cartridges. A first cartridge can be heated up to 1220 K and the second high temperature cartridge reaches maximal temperatures of 1800 K. A temperature difference of 1000 K between the two cartridges can be maintained for at least 3 h. Clustering occurs upon supersonic expansion from a conical nozzle. This cluster source has two main applications: (a) the generation of mixed metal clusters and (b) the investigation of pure metal clusters at various expansion conditions. The performance and applications of this source are illustrated by presenting results of the heterocluster formation of mixed sodium/gold and sodium/silver heteroexpansions. In addition, the influence of the oven parameters on the internal temperatures of the generated clusters is illustrated with the example ofNa2.©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148015

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An automated system for controlling the interelectrode gap of the carbon arc and positioning the plasma, constructed from commercially available components, is described. The core components of the system are the linear photodetector array, analog, and digital integrated circuits, and two direct current motors. It allows for both maintaining constant arc gap and its positioning against the optical axis of the plasma diagnostic arrangement. The method of operation is demonstrated via the production of fullerenes and carbon nanotubes. This control contrivance has been used for more than one year in bench scale with very satisfactory results. In addition, the design presented here has been found to be simple to construct from readily available components and has the merit of being quite inexpensive, too (the entire cost is under $2400). ©1997 American Institute of Physics

ISSN:0034-6748    

DOI:10.1063/1.1148016

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article we describe the design and the operation of an original, high transmission, electrostatic “double toroidal” electron energy analyzer. The double toroidal analyzer allows the high resolution and high luminosity simultaneous measurement of the kinetic energy, and angular distribution of electrons, using a two-dimensional position sensitive detector. The exact shape of the electrodes is deduced from both analytical and numerical electron trajectory calculations. The electron detector is based on a charge analysis and optimized to attain a100kHz counting rate. The actual performances of the analyzer are illustrated with spectra obtained after resonant Auger decay ofN2Oexcited around the nitrogenKshell(h&ngr;=401eV), and of Kr after3d5/2→5pexcitation ath&ngr;=91.2eV. A “e´tendue” of15&percent;of the pass energy, as well as a resolving power(Ep/&dgr;E)of100were measured. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148017

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

By applying an after acceleration electric field, the detection and registration of the ion species and spectral distribution of low energy ion beams(<1 keV)have been achieved by the Thomson spectrometer with CR-39 nuclear track detector as detection plate. With the use of this modified spectrometer, the low energy and high energy density plasma ion beams generated by a coaxial plasma gun have been detected and investigated. The ion beams were mainlyN+ions and were distributed in the energy range fromE∼0.12to 0.4 keV. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148018

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A formula including correction due to change of beam injection angle is derived for measurements of beam energy using parallel plate energy analyzers. The formula is mainly aimed for potential measurements in high temperature plasma with heavy ion beam probes, and an example is presented to demonstrate the usage of the formula. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148019

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A glass polycapillary lens that both bends and focuses a cold neutron beam has been designed and constructed. The bender focuser guides part of the incident beam away from its line of sight and focuses it to a spot of width 0.65 mm at a distance 95 mm from the lens exit and 20 mm below the bottom edge of the beam path, with a gain of 20 in neutron current density. The neutron transmission characteristics of the lens have been determined with two types of position-sensitive detectors, a charge injection device, and an imaging plate. The lens has been tested with prompt gamma measurements on a gadolinium shard and titanium foil. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148020

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new type of small, simple, indirectly heatable Langmuir probe for measurements in alkaline plasmas is presented. The heating element of this probe consists of an elogated half-loop of Ta-wire wound helically, around a thin ceramic tube that carries the probe collector. It is situated as closely as possible to the latter. The necessary heating power is a few watts. It is shown that the inevitable alkaline coating of the probe collector can be removed by sufficient heating. Various types of coating and their influence on the probe characteristic are discussed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148021

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A Faraday-type magnetometer is described in which the magnetic force is measured capacitively by monitoring the displacement of a spring-suspended quartz sample holder. A double gradient coil is used in order to compensate the force on the empty sample holder, thus minimizing the background signal. The magnetometer can be used at any temperature down to 1.4 K and has an ultimate sensitivity for magnetic moments of2×10−6emu(G cm3).©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148022

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A superconducting quantum interference device magnetometer system designed for low field static and dynamic susceptibility measurements is described. Magnetic shields reduce the residual field in the sample space to about 0.04 A/m (0.5 mOe). A highly stable dc magnetic field is generated by a small superconducting solenoid working in the persistent mode. The temperature control system yields a resolution better than 10 &mgr;K in the range of 30–100 K. Combining ac susceptibility and dc magnetic relaxation measurements, the system allows dynamic susceptibility studies in a time window ranging from3×10−6to106s. The sensitivity of the system is10−12 Am2(10−9emu). ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148023

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Three-interval approximations ofT=f(R)andR=g(T)functions for germanium resistance thermometer (GRT)(1.4–5.7)K;(5.7–27.4)K;(27.4–100)K and platinum resistance thermometer (PRT)(14–31)K;(31–95)K;(95–325)K is carried out, using a weighted orthonormal polynomial expansion method (OPEM). A two-interval OPEM approximation ofT(R)andR(T)functions for PRT(14–70)K;(70–325)K is also presented. Our OPEM approximation of theT(R)function for the GRT and PRT, compared with other descriptions, based on Chebyshev or ordinary polynomials with the same calibration test data is discussed also. The results, shown in tables and figures, demonstrate the reliability and the advantages of the proposed OPEM, in cryogenic thermometry. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148024

出版商:AIP    

年代:1997

数据来源: AIP