摘要:

A high temperature optical cell which allows simultaneous monitoring of thermally induced transformations by differential thermal analysis has been designed and constructed. The &agr; → &bgr; phase transformation in both evaporated thin films and bulk phthalocyanine has been studied with the cell and transformation rates determined. The rate constants were approximately three orders of magnitude larger for the bulk sample than for the evaporated films.

ISSN:0034-6748    

DOI:10.1063/1.1684803

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A compact, inexpensive, and surprisingly sensitive microwave frequency ESR spectrometer has been developed. A Gunn diode placed directly in the sample cavity and operated near the threshold of oscillation is the central feature of the unit.

ISSN:0034-6748    

DOI:10.1063/1.1684804

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A new vacuum system has been designed and constructed for a Siemens Elmiskop I electron microscope in order to provide a cleaner environment about the specimen during normal use of the instrument, and to prepare the instrument for the addition of an ultrahigh vacuum specimen chamber forin situfilm growth studies. Liquid nitrogen sorption pumps are used on the upper and lower parts of the microscope column, and an Orb‐Ion pump is used to pump differentially on the large Siemens specimen chamber (with airlock). An impedance tube at the top and an impedance aperture at the bottom of the specimen chamber restrict the gas flow rate into the chamber to 7.04×10−3liter/sec. Under operating conditions the pressure in the upper and lower parts of the microscope is <2×10−5Torr, the (large Siemens) specimen chamber pressure is <2×10−6Torr, the hydrocarbon contamination rate is ∼0.7 Å/min, the specimen changing time is 2 min, and the plate changing time is 4 min. The corresponding figures in the original unmodified microscope are ∼2×10−4Torr, ∼2×10−4Torr,∼ 500 Å/min, 1 min, and 4 min. Further advantages are noiseless and vibrationless operation.

ISSN:0034-6748    

DOI:10.1063/1.1684805

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A proton nuclear resonance probe for high field calibration of room temperature access superconducting solenoid fields is described. The probe may be made in a simple fixed‐tuned version, or a tunable version to cover the range from about 40 to 70 kG. Such a probe has the advantage that it may be used on the end of a long probe stem, may be made quite small if necessary, has a high Q, may be used to calibrate homogeneity and persistence easily, may be tested prior to use with DPPH, and may be constructed in just a few hours. The probe can be adapted to use at liquid helium temperatures utilizing3He samples.

ISSN:0034-6748    

DOI:10.1063/1.1684806

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An electronic system that provides for the unambiguous reading of simple mechanical shaft angle digitizers is described. The system is virtually insensitive to contact bounce, to bridging between adjacent contacts, and to the errors that can occur when several contacts change state at the same time. The system is based upon repetitive comparisons between the last valid reading and the current digitizer state. The output is updated only when the input is found to be unambiguous.

ISSN:0034-6748    

DOI:10.1063/1.1684807

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A simple and inexpensive microstrip transmission line of adjustable length is described. The device, although physically considerably smaller, is electrically similar to the usual coaxial line stretcher and can be fabricated easily from standard printed circuit or microstrip boards.

ISSN:0034-6748    

DOI:10.1063/1.1684808

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An experimental study has shown that dc arc welding generators can be used satisfactorily as an inexpensive power source for large magnet systems. A 120 Hz load current ripple of only 0.05% rms was measured at one‐half load and decreased for heavier loads. Random low frequency current fluctuations of⪞3%peak‐to‐peak were detected but were reduced to⪝0.5%peak‐to‐peak with a feedback technique.

ISSN:0034-6748    

DOI:10.1063/1.1684809

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A new electron beam injection gun has been developed to produce pulsed relativistic electron beams with a power of 1010W. The annular shaped beam propagates in a magnetic field with efficiencies approaching 100% and its radius may be controlled by the magnetic field configuration.

ISSN:0034-6748    

DOI:10.1063/1.1684810

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Superimposed modulation and lock‐in techniques have been successfully applied in order to minimize statistical fluctuations and to eliminate the low frequency internally generated noise in a sampling apparatus for fast, repetitive light signals detection. Some improvements are suggested here for applying the described technique to the study of ir fast light pulses, by means of electro‐optical sampling.

ISSN:0034-6748    

DOI:10.1063/1.1684811

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A new plasma source has been designed and tested which is capable of producing a stationary, quiescent spherical diffusion plasma of 69 cm diameter. This plasma is free of electric currents, and the electric fields in it can be kept below 10 mV/cm. Electron temperatures between 103and 3×103K and plasma densities between 108and 1010cm−3were measured with a Langmuir probe in the pressure range 0.1–10−4Torr. Radial variations of the plasma density smaller than 10% over about two thirds of the plasma radius were observed in argon at pressures between 10−2and 10−4Torr.

ISSN:0034-6748    

DOI:10.1063/1.1684812

出版商:AIP    

年代:1970

数据来源: AIP