摘要:

A radioactive source Fe55was used to measure the density of high‐temperature combustion products through a flame zone 6.5 cm long. Premixed propane‐oxygen and argon were used for the experiments with a porous metal burner. Temperatures were determined downstream of the main reaction zone in the flame at one atmosphere. Temperature profiles were obtained through the preheat and main reaction zone using radioactive Fe55coated on a small platinum wire as a line source.

ISSN:0034-6748    

DOI:10.1063/1.1716144

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An apparatus is described which is based on the technique introduced by Kistiakowsky utilizing the absorption of soft x‐rays to measure densities behind gaseous shock and detonation waves. Experimental conditions leading to the smallest absorption statistical uncertainty consistent with maximum sensitivity are defined. These may be approximated at reasonable pressures and tube diameters by adding a strongly absorbing rare gas diluent to the experimental gas mixture. Under such conditions measured densities are accurate to ±1%, as demonstrated by comparison of experimental and calculated densities for shock waves in krypton. At some sacrifice in accuracy, space resolution of 1 mm and time resolution of 1 &mgr;sec may be achieved.A continuously pumped, laboratory‐built, demountable, pulsed x‐ray tube with anL‐cathode and tungsten target is used at an accelerating voltage of 20–‐30 kv to obtain currents up to 0.2 amp for durations of the order of 1 msec. Copper and chromium targets were also investigated.For calibration purposes the tube is operated at a steady current of ≈0.2 ma and detector signals are measured potentiometrically to obtain transmission as a function of gas density.

ISSN:0034-6748    

DOI:10.1063/1.1716145

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Circuitry is described that is capable of delivering sparks with current pulses adjustable from square through damped oscillatory form, energies up to 100 j, peak currents to 50 000 amp, and rise times less than 2 &mgr;sec.To observe the spark current, a novel differential measurement scheme was developed. This scheme eliminates errors inherent in establishing reference grounds, provides a method of reducing high‐frequency and high‐peak current distortions inherent in current viewing shunts, and provides a method of determining the potential across a spark gap.Electrical characteristics of spark discharges in a saturated NaCl&sngbnd;H2O solution, as well as the rate of growth of the luminous plasma of a spark in air, are described to illustrate the flexibility and general characteristics of the spark circuitry and the differential measurement scheme.

ISSN:0034-6748    

DOI:10.1063/1.1716146

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The apparatus consists of a calorimeter of basically simple design, above which is a movable, vertical furnace for heating the specimen contained in a hermetically sealed platinum capsule. A complete series of measurements may thus be carried out on one sample. The capsule is dropped directly into a metal dry‐chamber in the calorimeter in contact with a stirred liquid for measurement of heat content changes. A recommended procedure, based on experiments in pairs is described; one of each pair being a calibration drop, the other the specimen drop. The computation of heat content changes from the temperature changes observed is described. The limits of error of this and other calorimetric assemblies are critically discussed. Data to illustrate the results for the LiCl&sngbnd;KCl eutectic mixture (mp 354.1°C) and the reproducibility of the measurements are given. The calorimetric assembly is capable of measurements of heats of fusion of inorganic compounds to an accuracy of ±2%.

ISSN:0034-6748    

DOI:10.1063/1.1716113

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An FFAG accelerator accommodating two beams circulating in opposite directions is proposed. Analytical expressions for the equilibrium orbits and the betatron oscillations are developed and are compared with numerical results obtained by digital computation. Typical design parameters are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1716114

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A cryostat for continuously bathing samples in liquid nitrogen or other heat transfer liquids during nuclear reactor irradiation has been constructed and successfully operated. The samples to be irradiated at low temperature are immersed in the heat transfer fluid which is high‐purity liquified nitrogen circulating in a closed system at a pressure greater than that of the atmosphere. The liquid is kept below its boiling point throughout its cycle by use of a heat exchanger located outside the reactor shield. The heat exchanger is cooled by commercial liquid nitrogen boiling at atmospheric pressure. Since oxygen and water vapor from the air cannot enter the closed pressurized system, no chemical explosions inside the nuclear reactor have occurred. Baths at other temperatures may be obtained by substituting suitable liquids for the high‐purity nitrogen heat transfer fluid and by keeping the heat exchanger at the desired temperature.

ISSN:0034-6748    

DOI:10.1063/1.1716115

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The appearance of a common‐mode voltage at both grids of a conventional twin‐triode differential amplifier produces, by cathode follower action, an equal swing of the common cathode point. The resulting change in the operating point of the tubes causes undesired shifts of both the differential gain and the balance of the amplifier. In the present work, the change of voltage at the common cathode point is entirely transferred (``bootstrapped'') to the plate supply, with the result that a common‐mode voltage does not affect the operating points of the differential amplifier tubes. By this means, a common‐mode rejection ratio of >104:1 is readily achieved without tube selection or adjustments. With tube selection and some adjustment, >105:1 may be obtained. A common‐mode signal of ±35 v changes the differential gain of the circuit by 0.5% or less. A bootstrapped differential VTVM circuit which deflects a 1 ma 1.5K‐ohm pen recorder to full scale with ∼0.2 v dc input is described in detail.

ISSN:0034-6748    

DOI:10.1063/1.1716116

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A device for the sensitive detection of ultraviolet radiation in the range 1080–1260 A is described. This device is a Geiger‐Mu¨ller counter in which the counts are initiated by the photoionization of iodine vapor used in the tube's filling. The range of response is determined by the ionization potential of iodine and the short wavelength cutoff of LiF, through which radiation enters the counter. Because of iodine vapor in the filling, the electrical characteristics of the tube are those of a halogen‐quenched counter.

ISSN:0034-6748    

DOI:10.1063/1.1716117

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Thermal precipitation is attractive for airborne particle collection because of the high collection efficiencies which may be attained and the convenient examination of the deposit. Most thermal precipitators, however, have very low sampling capacities or flow rates. To take fullest advantage of the desirable features of thermal precipitation, a new precipitator was designed and constructed. It operated continuously, and deposited particles upon a moving tape or substrate. Complete collection of particles resolvable with an electron microscope was attained in a 3‐in. diameter precipitating zone at a flow rate of 1 l/min.

ISSN:0034-6748    

DOI:10.1063/1.1716118

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A device is described which stabilizes the energy of the 32‐Mev proton linear accelerator. The general system is similar to that developed for the Princeton cyclotron, with the exception of the control on the output energy. This control is obtained by slightly detuning the exit end of the rf cavity by means of a rotating paddle. Range is used to predetermine the proton energy. An auxiliary circuit is provided for direct control of the correcting paddle. Two ionization‐chamber currents are compared by a difference amplifier which is quite sensitive but very stable and can be located at any distance from the ionization chamber. An energy stabilization of ±40 kev is achieved.

ISSN:0034-6748    

DOI:10.1063/1.1716119

出版商:AIP    

年代:1958

数据来源: AIP