摘要:

A discussion of what is known experimentally about the thermal contact problem at very low temperatures is given. Liquid4He is a particularly promising contact agent. Methods of using liquid4He, thermometry using cerium magnesium nitrate, and solutions to the filling and isolation problems using an open capillary are discussed. The techniques are applied to an apparatus suitable for heat capacity measurements to below 0.02°K and to an apparatus for measurement of superconductive properties at temperatures substantially below 0.01°K. The performance of the apparatus for heat capacity and superconductivity measurements is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1720340

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An instrument for producing contour diagrams using a conventional X‐Y plotter is described. It consists of a specially designed pulsed current plotting head controlled by gating circuits which use commercial analog and digital modules. The X‐Y plotter scans the head over electrosensitive paper and symbols consisting of dot patterns are plotted with no mechanical delay. The gating circuits may be adjusted to any desired set of contour intervals.

ISSN:0034-6748    

DOI:10.1063/1.1720341

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A modified rotating cryostat and its use forin situinfrared studies are described. An improvement in sensitivity over present low temperature infrared cells and much shorter deposition times have been obtained.

ISSN:0034-6748    

DOI:10.1063/1.1720342

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Experiments to determine the heat transfer from hot wires with length‐to‐diameter ratios on the order of 102, which are commonly used in hot wire anemometry, were performed. The Reynolds numbers used were less than 10, the overheat ratio was kept at 0.80, and the fluid was air. The results indicate that the exponentnin the relationshipEb2=A+BUn, whereEbis the bridge voltage andUthe fluid velocity, was equal to 0.45 for wires operated at constant temperature. A linearization circuit which provides an accurate means of recovering the velocity from the above relationship for values ofnof 0.45 and 0.50 is described. The main component of the circuit is a temperature compensated, ten segment silicon diode function generator manufactured by Philbrick Researches, Inc. The frequency response of the linearizer is from dc to 36 kc or from dc to 180 kc depending on the operational amplifiers used in the circuit.

ISSN:0034-6748    

DOI:10.1063/1.1720343

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A new type of viscometer operated by electromagnetic force is described. Two versions of such an apparatus are presented, one involving the measurement of mechanical entities only, the other based upon the measurement of ionic current density and of a magnetic field. These viscometers are both closely related to ordinary flow viscometers since the force setting the liquid into motion acts directly on the liquid itself, with no mechanical moving part interposed. The force is much less intense than gravity and is easily adjusted at will down to very small values. For this reason and because of a better design of the channel in which the liquid flows, very low values of shear stress can be obtained; thus making the apparatus described ideal for use with non‐Newtonian liquids, like high polymeric solutions or suspensions of DNA. The fact that the liquid must be subjected to electrolysis is a serious drawback, which can be circumvented by resorting to relative measurements. Improvement of the apparatus is under study.

ISSN:0034-6748    

DOI:10.1063/1.1720344

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Currents flowing through an electrode, in contact with a plasma, can be measured by inserting Rogowsky coils in the electrode itself. In order to avoid uncontrollable shunting of the current and damage of the coil owing to the plasma, a thin metallic foil is inserted between the coil and the plasma. The effects of such a screen on the measurements are calculated and compared with experimental results.

ISSN:0034-6748    

DOI:10.1063/1.1720345

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

The design of a balance for measurement over the range from 4.2 to 300°K of the static magnetic susceptibility of weakly magnetic substances is described. The balance is a Curie‐Che´neveau type torsion balance which incorporates photocompensation to achieve a null measuring instrument. The maximum sensitivity of the balance is approximately 10−3dyne and performance with less than 1% error is possible for magnetic susceptibility values in the range from 10−5to 10−8emu/g (cgs units). Some typical susceptibility data obtained with the aid of this balance are presented.

ISSN:0034-6748    

DOI:10.1063/1.1720346

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A molecular beam electron bombardment detector is described and operational data are presented. The detector makes use of a Paul mass filter to increase its versatility. The detector is calibrated by the use of molecular beams of neon, argon, and krypton. Respective detection efficiencies are 1 atom in 2400, 320, and 80.

ISSN:0034-6748    

DOI:10.1063/1.1720347

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An ultrahigh vacuum system is described which was designed to study particles emitted from surfaces under bombardment by hydrogen ions. Stress has been laid on obtaining pressures ∼10−9Torr in the presence of the ion beam. The beam is mass analyzed and its energy is variable from 5 to 30 keV. A maximum current of 300 &mgr;A over 0.1 cm2is obtainable at the target, so that a beam/neutral gas bombardment ratio of better than 1000/1 can be achieved. A target mounting turntable is described which allows up to six targets to be bombarded in turn. A quadrupole mass filter is incorporated in the target chamber as a residual gas analyzer and as a means of identifying gas species resulting from the bombardment of surfaces.

ISSN:0034-6748    

DOI:10.1063/1.1720348

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A cold trapped McLeod gauge, a capacitance manometer, and an ion gauge have been used simultaneously to measure gas pressure in the range 10−4to 3×10−3Torr. Data were obtained for He, Ne, Ar, Kr, Xe, N2, O2, CH4, CO, H2, and CO2. The capacitance manometer and pressure chamber were maintained at a constant room temperature to avoid thermal transpiration corrections. Comparison of data among gases clearly showed the systematic McLeod gauge error attributed to mercury streaming to the cold trap. The capacitance manometer and McLeod gauge readings agreed within 2% at 10−3Torr for He, while the McLeod reading was 15% low for Xe at the same pressure. The errors for the other gases were intermediate. Spurious mercury capillary wetting effects, leading to serious errors in the McLeod gauge reading, were also noted for some of the molecular gases. The capacitance manometer was clearly superior to the McLeod gauge as a universal pressure sensor, and appears capable of reliable readings accurate to a few per cent at 10−4Torr.

ISSN:0034-6748    

DOI:10.1063/1.1720349

出版商:AIP    

年代:1966

数据来源: AIP