摘要:

A versatile zone‐refining apparatus which employs liquid nitrogen as the refrigerant to maintain the compound to be purified in the solid state while appropriately spaced resistance heaters generate the moving liquid zones to purify compounds whose melting point lies between 200 and 350 K is described. As much as 0.750 kg of substance can be purified at one time to a purity better than 99.95 mole %.

ISSN:0034-6748    

DOI:10.1063/1.1137674

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The application of an electron‐beam controlled diffuse discharge to high‐power (>109W), repetitive opening switches is analytically formulated under a set of assumptions. Basic physics considerations are combined with energy transfer requirements to obtain analytical estimates of thee‐beam controlled switch parameters for given circuit requirements. The switch design is optimized by minimizing the switch pressure subject to the constraint of system efficiency. The result of this optimization is that each of the major energy losses—conduction, opening, and electron‐beam production—are roughly equal to each other. This formulation is used to relate the switch parameters to the desired operating characteristics for an arbitrary number of pulses. As an example, the formalism is utilized in outlining the design of a single pulse, high‐power (&bartil;1010W) inductive storage system. A judicious choice of gas or gas mixture results in desirable changes in the system design or efficiency.

ISSN:0034-6748    

DOI:10.1063/1.1137675

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

For experiments involving SQUID’s it is sometimes desirable to have a small source of confined magnetic field in order to provide a dc or rf flux bias. This has been done by closely winding ♯50 AWG copper wire on a 250‐&mgr;m‐diam optical fiber. The resulting solenoid is very small and has excellent mechanical and electrical properties at 4 K.

ISSN:0034-6748    

DOI:10.1063/1.1137676

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A system is described which allows on‐line control of uniaxial stress and magnetic field for the investigation of the magnetic properties of materials under stress. This has been of considerable importance in studies of the properties of samples of steel, in particular the investigation of ferromagnetic hysteresis and the magnetomechanical effect. As a result, exact algorithms for the demagnetization of samples and for obtaining the anhysteretic or ideal magnetization curve have been devised.

ISSN:0034-6748    

DOI:10.1063/1.1137677

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A fast multichannel scaler has been developed with a resolution of 12.5 ns and and a channel memory of 215(32 768), yielding a timing range of 410 &mgr;s. The maximum cycle time of the instrument is 30 starts/s. Fast timing is achieved by the use of multiplexing and parallelism in data collection and transfer. When operating at the highest resolution, each channel is a 1‐bit counter (flip‐flop). The scaler is intimately interfaced to an 8‐bit Z80 microcomputer. The characteristics of the scaler are ideal for ion time‐of‐flight measurements in multiphoton ionization experiments. The time resolution is illustrated with a photoelectron–photoion coincidence time‐of‐flight mass spectrum. In addition, the MCS is compared to a time‐to‐pulse‐height converter/multichannel analyzer system by collecting random stop signals.

ISSN:0034-6748    

DOI:10.1063/1.1137678

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We present a coplanar flip‐chip mounting technique for broadband microwave and high‐speed opto‐electronic devices. The technique is based on coplanar waveguides with tapered structures that can be fabricated with high precision by photolithographic means on planar dielectric substrates and device chips. It allows the inclusion of micrometer size devices into broadband circuits and serves for the transmission of high‐speed signals with low reflection over waveguides with varying geometry and to external coaxial lines with millimeter dimensions. As demonstrated by flip‐chip mounted high‐speed photoconductors, by a coplanar pulse‐forming circuit, and by a coplanar line termination, this technique allows broadband transmission with reflections not exceeding a few percent in the frequency range from dc to 25 GHz and signal durations at least as short as 20 ps.

ISSN:0034-6748    

DOI:10.1063/1.1137679

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A technique has been developed for fabricating electromagnetic induction coils in a reproducible manner. The process utilizes a split mandrel that can be disassembled to remove the mandrel from the coil. The technique has increased coil production rates by a factor of 8 over the freehand winding method. The success rate for producing a functional levitation coil has been increased from 50% to 95%. The levitation coil designed during this work has successfully levitated and melted a variety of alloys including Cu, Ag, Ag–Ni, Cu–Fe, Fe–C, and Nb–Ge. W was also levitated but not melted at temperatures as high as 2700 °C. The highest sample melt temperature achieved was 2400 °C for the Nb–Ge samples.

ISSN:0034-6748    

DOI:10.1063/1.1137680

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A portable multichannel data logger is described. The system utilizes a commercially available compact computer which is coupled to a single‐chip voltmeter via a UART. Channel selection, under the direction of the computer, is performed by an analog multiplexer. Substantial data storage capabilities are provided by resident RAM within the computer.

ISSN:0034-6748    

DOI:10.1063/1.1137638

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A dc motor electronic controller, driving a rotating chopper, is presented. The controller uses an integral feedback technique, consisting of charging a storage capacitor by means of width modulated pulses. These pulses are obtained by comparing the revolution time of the chopper with a fixed time. It is shown that the steady‐state angular speed is independent both of the friction coefficient and the feedback loop gain. The stability condition of the feedback loop gain is also derived.

ISSN:0034-6748    

DOI:10.1063/1.1137639

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We describe a simple and inexpensive diagnostic for rapid measurement and display of the radial profile of the ion beam generated by an experimental ion source. The technique may be useful for other kinds of beams also.

ISSN:0034-6748    

DOI:10.1063/1.1137640

出版商:AIP    

年代:1984

数据来源: AIP