摘要:

The cryogenic apparatus and techniques used to calibrate 3 platinum‐encapsulated 4‐lead germanium resistance thermometers for use in precision calorimetry from 1 to 25°K are described. The calibration data for each thermometer were fitted with the aid of a digital computer by a polynomial expressing logRin terms of powers of logT. The sensitivity and temperature‐cycling stability of these thermometers were adequate to recommend this type of temperature sensor for accurate low temperature calorimetry. A test of the temperature scale and of an isothermal type calorimeter was made by measuring the heat capacity of a sample of 99.99+% copper from the 1965 Calorimetry Conference Copper Standard and comparing the results with those obtained by other investigators. An equation to represent the heat capacity of pure copper from 1 to 25°K, based upon appropriate literature results and the present data, is offered as a convenient copper reference equation for intercomparison of heat capacity results from various laboratories.

ISSN:0034-6748    

DOI:10.1063/1.1771348

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A new shunt‐series amplifier section was developed for fast rise time pulse amplifiers intended primarily for use with accelerator beam probes, solid state detectors, and fast ionization chambers. Design equations for the gain section were derived from a high frequency model and were validated by computer analysis and experimental results. Two amplifiers were built, with three gain sections cascaded in each. The gain of these amplifiers was 270 and 135, and the rise time was 1 and 0.9 nsec, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1771349

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The single electron statistics of a porous KCl transmission dynode are studied experimentally. Pulse amplification for subsequent analysis in a multichannel analyzer is obtained by coupling the output of the transmission dynode to a 14 stage electron multiplier. The observed pulse height distribution is quasiexponential. Single primary electrons, emitted thermionically from a hairpin filament and accelerated to 8–9 kV impact energy, produce stable secondary electron yields of 30–40 electrons at pulse counting rates up to 2×106cps. In a second experiment, the KCl transmission dynode is preceded by an Al2O3target surface, which is bombarded by single ions and produces a peaked secondary electron distribution from this surface. In this case, the anode pulse height distribution of the electron multiplier also is peaked, but has a relative variance greater than that expected from Poisson statistics. The two physical arrangements cover a wide range of shapes of pulse height distributions, and the resulting compound distributions are in good agreement with theoretical shapes calculated from a Polya statistical model, which includes Poisson and exponential distributions as limiting cases.

ISSN:0034-6748    

DOI:10.1063/1.1771350

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An apparatus for the determination of interaction virial coefficients is described. The new design, which makes use of a pressure transducer, is a modification of a differential device previously employed for mixtures of the permanent gases. Dead space corrections have been completely eliminated and the technique is now applicable to a broad range of substances.

ISSN:0034-6748    

DOI:10.1063/1.1771351

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A multichannel analyzer using time‐amplitude conversion for time of flight mass spectrometry is described. This system extends the ultimate sensitivity of the Bendix mass spectrometer from about 10−8mm to about 10−11mm partial pressure of H2in the source, while still retaining whole spectrum presentation. It is equally applicable to negative and positive ion pulses, and so greatly improves the flexibility of the spectrometer. Examples of mass spectra from low partial pressures of gas are given showing the signal to noise improvements up to 103obtained for a minute's operation.

ISSN:0034-6748    

DOI:10.1063/1.1771352

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Internal turbulent water cooling is used to limit electrical conductor peak temperature rise to 8°C, only 2°C above the outlet water temperature, and average temperature rise to 2°C, at a current density of 6750 A/cm2, and a power transfer of 13 W/cm2. The water is continuously purified to maintain a resistivity ≈107&OHgr;‐cm, to keep electrical leakage through 200 water junctions to less than 10−5of the current in the conductors. A thermostating system using transient‐limiting ``anticipator'' thermocouples keeps temperature excursions associated with large power steps (1–80 kW) to 1°C, a sevenfold improvement over the system without anticipators.

ISSN:0034-6748    

DOI:10.1063/1.1771353

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The development of a membrane type pressure probe is reported in which the position of the membrane is recorded by frustrated internal reflection. The probe has a risetime of not more than 5 &mgr;sec, and records pulses of any length, as well as static pressure. It can have a static sensitivity of several volts per atm, and is relatively unaffected by electrical pickup noise. Examples for application are given, and the probe is compared with a piezo probe.

ISSN:0034-6748    

DOI:10.1063/1.1771354

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A harmonic bridge circuit has been developed for measuring linear and nonlinear electric coefficients and quadratic electrooptic coefficients in high dielectric perovskite crystals. Third and fifth harmonic components are added to the fundamental audio‐frequency driving voltage. The bridge is balanced when the charge or displacement of the crystal is sinusoidal. The harmonic content of the driving voltage may then be measured on a harmonic analyzer, from which measurements the electric coefficients of the crystal may be calculated. The same sinusoidal displacement may be used to display the electrically induced phase retardation intensity pattern on the oscilloscope. The effective electrooptic coefficients are readily determined from the oscillographs. The advantages of the harmonic bridge method are illustrated by measurements of the electric and electrooptic coefficients of a crystal of potassium tantalate niobate (KTN).

ISSN:0034-6748    

DOI:10.1063/1.1771355

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A method is proposed and a device described for creating a hot zone which can be moved down a long tube in a controlled manner without the use of any moving parts. The heat source is an arc whose position can be controlled by small magnetic fields. The details and performance of the critical control circuit are discussed. Applications to the zone growth of crystals are apparent.

ISSN:0034-6748    

DOI:10.1063/1.1771356

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An apparatus is described for the measurement of the kinetics of fairly fast (half times 1–5 min), homogeneous, liquid chemical reactions, by recording the temperature‐time curve in an adiabatic batch reactor. Adiabatic conditions are maintained by keeping the metal reactor as closely as possible at the same temperature as the reacting species by passing a heating current directly through the walls. Allowance is made for controller set point changes which accompany a temperature increase of the system. Specific heat determinations were carried out on water to test the ability of the control system to maintain adiabatic conditions. The operation of the apparatus is illustrated with kinetic measurements of the hydrolysis of acetic anhydride in dilute aqueous solutions.

ISSN:0034-6748    

DOI:10.1063/1.1771357

出版商:AIP    

年代:1967

数据来源: AIP