摘要:

An instrument developed to measure the magnetic properties of materials in a variety of forms by oscillographic techniques is described. Magnetic hysteresis loops can readily be obtained for specimens in rod, powder, tape, or wire form having cross‐sectional areas as small as 10−5cm2or as large as 0.3 cm2(¼ in. rod).With slight modifications, the instrument can be adapted to magnetic measurements of materials as a function of frequency, temperature, tension, torsion, or pressure using the appropriate setup.

ISSN:0034-6748    

DOI:10.1063/1.1741286

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

Elapsed time between two or more transient events that occur within a time interval of 12 milliseconds is measured with a maximum error of ±6 microseconds. Higher accuracies are attained when the time interval is reduced.A spiral trace is presented on the screen of a cathode‐ray tube. The trace is modulated by a crystal‐controlled oscillator to provide accurate time markers. Each transient event produces a momentary radial deflection of the spiral trace. Elapsed time between any two events is determined by counting the time markers between the corresponding signals.

ISSN:0034-6748    

DOI:10.1063/1.1741287

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

A coincidence counting apparatus of high resolution is described. It employs proportional counters whose amplified pulses trigger blocking‐oscillators to give artificial pulses which are used in the coincidence discriminator. A continuously variable time delay is provided in one of the amplifier channels for determining the resolving time and for studying delayed coincidences. Under favorable conditions the passage of an ionizing particle through a counter can be determined to within an uncertainty of about 10−8sec.

ISSN:0034-6748    

DOI:10.1063/1.1741288

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

Two simple rotating systems have been designed for the determination of the specific impulse of rocket propellants. The pin wheel consists of a bicycle wheel mounted horizontally in a steel frame. A small rocket motor containing the propellant which is to be tested is mounted on the wheel so that the thrust delivered by the rocket accelerates the speed of rotation of the wheel. A photographic record of the rotational speed is then used to calculate the impulse delivered as a function of the time. The rotating bar is operated in a manner similar to that of the pin wheel.The rotating systems have been used for the determination of relative effective gas velocities of a number of double‐base rocket powders. Impulse measurements of miniature rockets of the order of 1 pound‐second were made. An investigation of the effect of expansion ratio of rocket nozzles on the reduced specific impulse showed good agreement with theoretical calculations.

ISSN:0034-6748    

DOI:10.1063/1.1741289

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

A magnetic field discriminator is described which uses the nuclear induction signal from protons to give a ±75‐volt change of d.c. voltage for a ±0.3‐gauss change in magnetic field without using direct coupled amplifiers.An ordinary degenerative current regulator with the addition of information from the magnetic field discriminator will control a magnetic field to within 0.02 gauss for a 10 percent line voltage change or for normal changes in magnet geometry.The magnitude of the magnetic field is maintained in terms of a frequency, the value of which gives the absolute magnitude of the magnetic field.

ISSN:0034-6748    

DOI:10.1063/1.1741290

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

A magnet with ring‐shaped pole pieces and a central core makes a large reduction in weight possible, thus eliminating the main obstacle to the use of &pgr;‐radian mass spectrometers.

ISSN:0034-6748    

DOI:10.1063/1.1741291

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

The effect of beta‐radiation from C14has been examined on nineteen different films. The method employed uses a ``radiator,'' a set of eight radiating sources of different intensities, to replace the stable light source and absorbing wedge common in spectral photometry. With this device sensitivity and contrast of the nineteen films have been measured. Based upon these results and a microscopic estimation of grain size, recommendations are made for the most desirable film for use in radioautography and detection of radioactivity. Of the films examined, Eastman No‐Screen x‐ray film appears best for the detection of the beta‐rays, and Ansco Reprolith, and Eastman Type M x‐ray stripping films appear to be most desirable for work with radioautographs.

ISSN:0034-6748    

DOI:10.1063/1.1741292

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

The peak voltmeter circuit to be described was developed to minimize the error encountered in measuring pulses of short duration and low repetition frequency. Essentially the instrument contains an automatic switch connected in series with a condenser and a high d.c. source (B‐supply). Closing of the automatic switch by an input voltage allows the high d.c. source to charge the condenser. As soon as the condenser voltage becomes equal to the peak amplitude of the measured voltage the automatic switch opens. The condenser voltage is coupled through a high input resistance circuit, bridge‐balanced cathode follower, to an indicating meter. High accuracy is attained over wide ranges.

ISSN:0034-6748    

DOI:10.1063/1.1741293

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

A vacuum‐tube voltmeter circuit is described which is capable of measuring voltages within the range of from 0 to −5000 volts with an accuracy of 0.05 percent and a linear characteristic over the entire range. The input impedance is greater than 5×1010ohms. The circuit was developed for the purpose of measuring accurately high voltage sources of extremely low current drain which were employed for cosmic‐ray studies. It is based on a null method, using a vacuum tube having a high amplification factor as one arm of a balanced circuit and a constant current source as the other arm. The negative terminal of the measured voltage is applied to the plate of the tube, and the grid voltage is varied to maintain the same grid current which balances the current from the constant current source. Linearity results from the negligible varying space‐charge effect at constant grid current, and high precision measurements are obtained by means of a special circuit for measuring the change in grid voltage. By setting the grid current equal to the value of 1/&mgr;, where &mgr; is the amplification factor of the tube, the meter can be made to read directly the measured voltage.

ISSN:0034-6748    

DOI:10.1063/1.1741294

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

The various methods of dead‐time reduction are investigated and discussed. The application of a large negative voltage pulse to the center wire, just after the discharge starts, reduces the dead‐time. This effect is due to a combination of stopping the propagation of the ion sheath, ion neutralization, and ion multiplication. In the most favorable case found, the dead‐time of a Geiger tube having a normal dead‐time of 160 microseconds is reduced to 80 microseconds by this means. Increasing the gain of the detecting circuit without a negative pulse does not reduce the dead‐time more than a factor of two, unless the counting rate is greatly increased so that all pulses are small. Operation with high gain just below the Geiger threshold shows efficiency of the order of 50 percent for beta‐particles, and no measurable dead‐time.

ISSN:0034-6748    

DOI:10.1063/1.1741295

出版商:AIP    

年代:1948

数据来源: AIP