摘要:

The only generally available source of monochromatic microwave energy in the shorter mm‐ and sub‐mm‐wave region is still some form of the point contact silicon diode harmonic generator, usually driven by a cw fundamental frequency source operating in the 8–12 mm wave region. It has been found experimentally that the performance and stability of diodes for this application can be greatly improved by bombarding the silicon surface with positive ions. Described here are the methods used for the bombarding and mounting of silicon for this harmonic generating application, the construction of two practical wave guide circuits, the operating conditions for the most successful use of the material, and finally, the measured high‐frequency output is compared with that calculated on the basis of a simplified equivalent circuit for the harmonic generator.

ISSN:0034-6748    

DOI:10.1063/1.1716751

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A bearing dynamometer has been devised and built which enables ready evaluation of bearing materials. Coefficient of friction and shaft speed are presented on an X‐Y recorder. By varying the load on the bearing a family of curves may be quickly obtained yielding the basic performance characteristics of the bearing materials under actual bearing conditions.Prolonged tests can be performed during which observation of the bearing characteristics as a function of time can be studied.At present, bearings of ½‐in. diameter are being studied to speeds of 2000 rpm and coefficients of friction to 0.7. These ranges are easily extended.The speed determination is made by a dc tachometer‐generator. The essential element of the friction measuring system is a linear variable differential transformer acting as a transducer for the friction torque of the bearing.

ISSN:0034-6748    

DOI:10.1063/1.1716752

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A compact, portable pulse generator with output pulses in the millimicrosecond region at high repetition rates is described. The generator has repetition rates of up to 107pulses/sec, pulse rise times of less than 2.5 m&mgr;sec, and pulse widths adjustable from 2.5 to 25 m&mgr;sec. The output pulse is negative in polarity and is adjustable over an amplitude range of from 0 to 12 v into 125 ohms output impedance. The instrument has provisions for gating, single pulsing, and operation with drive from an external signal source.

ISSN:0034-6748    

DOI:10.1063/1.1716753

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The Hall effect can be measured in a ring‐shaped sample placed in an alternating magnetic field normal to the plane of the ring. The resultant circular electric field produces a current around the ring proportional to the time derivative of the magnetic field. This current interacts with the magnetic field, establishing a Hall voltage between the inner and outer radii of the annulus. For extrinsic semiconductors with single effective mass charge carriers, this Hall voltage is, in mks units,VH=&mgr;&ohgr;B02(a2−b2)sin2&ohgr;t/8,where &mgr; is the mobility, &ohgr; the field angular frequency,Bothe peak value of the magnetic field,athe inner radius, andbthe outer radius. This technique eliminates voltages arising due to misaligned probes and end‐effects in the conventional method. In addition, the measurement is independent of the conductivity for the case above. Experimental measurements on germanium, silicon, and indium antimonide rings yield mobility values in agreement with customary results.

ISSN:0034-6748    

DOI:10.1063/1.1716754

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A target positioner for use in the accelerating chamber of the Bevatron is described. This positioner has a rise time of 75‐msec and equally fast drivedown. The mechanism has proven reliable to 106cy between maintenance periods.

ISSN:0034-6748    

DOI:10.1063/1.1716755

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A standard Model 14M Cary recording spectrophotometer has been equipped with a special cell assembly for studies of the liquid state, particularly of water and radioactive aqueous solutions over a working range of 0 to 250°C and 0 to 1000 psia. The stability and reproducibility of measurements are comparable to those obtainable at room temperature.

ISSN:0034-6748    

DOI:10.1063/1.1716756

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A new x‐ray technique for the study of explosively accelerated metal systems is described. X‐rays from a 7‐Mev electron linear accelerator operated with a pulse length of 10 &mgr;sec pass through the assembly under study and are detected by NaI scintillators viewed by photomultipliers. Collimation is used to achieve time resolution of 0.2 &mgr;sec and space resolution of 0.025 cm parallel to the direction of motion and 1 cm perpendicular to the motion.

ISSN:0034-6748    

DOI:10.1063/1.1716757

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Convenient, tunable, sealed‐off cavity resonators are described at frequencies of 1, 2, 9, and 24 kMc, for use with internal pressures up to 1000 psi. The modes of oscillation employed were TE01n, TE11n, and TM01hybrid, all in a circular cylinder. A convenient method for sealing an iris, applicable over a wide‐frequency range, is to insert a tapered Teflon plug. A Kovar‐glass seal for coaxial lines is described that provides a good impedance match in a 50‐ohm line. The measuring procedure is described. Accuracy of dielectric loss measurements was increased by calibrating the loss changes of the cavity arising from reresonating it upon admission of lossless gas.

ISSN:0034-6748    

DOI:10.1063/1.1716758

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A voltage pulse spectrum generator is described which delivers the following distributions of pulse heights: (1) delta function distribution; (2) uniform distribution; or (3) triangular distribution. The pulses are available at either a regular rate or a random rate. The delta function distribution is calibrated and continuously variable over the ranges 0–100 v and 0–0.1 v. The duration of the pulses is adjustable over 1–4 &mgr;sec.

ISSN:0034-6748    

DOI:10.1063/1.1716759

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A method for analyzing the pulse‐height distribution of a single NaI crystal gamma ray spectrometer is presented. The method consists in solving the matrix equation,P=KN(hv), forN(hv), the incident gamma ray spectrum in whichPis the pulse‐height distribution, andKis the sensitivity matrix of the detector. A procedure for obtaining the elements ofKfrom curves obtainable from the pulse‐height distributions produced by a few standard monoenergetic sources has been devised. Experimental results are presented which demonstrate the validity of the method.

ISSN:0034-6748    

DOI:10.1063/1.1716760

出版商:AIP    

年代:1959

数据来源: AIP