摘要:

Conformal mapping is used to determine the cross section of a shim in order to improve the uniformity of the field in the air gap of a magnet. Experimental measurements on a laboratory electromagnet demonstrate the improvement in field uniformity.

ISSN:0034-6748    

DOI:10.1063/1.1719972

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Design factors are considered for the use of emitting and nonemitting metallic probes for measuring static potential in electron streams. Both unneutralized streams and those neutralized by positive ions in a field free drift space are considered. Experimental results are given for potential measurements in a cylindrical diode and in a beam type tube. Good agreement with theory is found for the radial potential distribution in the diode using either probe. The emitting probe gives best results but is more complex in construction and circuitry. Qualitative agreement with theory is found for axial and radial potential distribution in a neutralized cylindrical electron beam.

ISSN:0034-6748    

DOI:10.1063/1.1719973

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Construction details are given for a He gas scintillation neutron detector which operates to 238 atm at room temperature. A bakeable pressure‐vacuum manifold, on which the detector is evacuated and filled, also serves to remove contaminants from the DPS waveshifter. The detector appears stable when permanently sealed off. Curves are given for light output vs pressure, and some effects of impurities on such curves are noted. Measurements were made of relative sensitivity to60Co gammas and Pu‐Be neutrons. The gamma flux required to induce a current equal to that from 1 neutron/cm2sec is 15 MeV/cm2sec when the scintillating gas is4He, and 23 MeV/cm2sec when it is3He.

ISSN:0034-6748    

DOI:10.1063/1.1719974

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A spark chamber system is described which is designed to detect &ggr; rays in the cosmic radiation on high altitude balloon flights. It has (1) an acceptance cone of 30° half angle; (2) time resolution of 150 msec; (3) energy resolution from 30 to 500 MeV; and for a 100 MeV &ggr; ray, (4) a conversion efficiency of 12.4%, and (5) angular resolution of 3°. Events are recorded photographically. The system is triggered by a large scintillator above the chamber in anticoincidence with a scintillator‐Cˇerenkov telescope beneath. Only the chamber and high voltage components are pressurized. A magnetometer direction monitor locates the &ggr; ray direction to ±3° in right ascension and declination. The system has operated successfully on day and night flights and has a total weight of 80 kg.

ISSN:0034-6748    

DOI:10.1063/1.1719975

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A detailed description is given of an apparatus which makes possible the propagation of ultrasonic pulses through very thin solid samples (foils, films, fine wires, whiskers, etc.). The apparatus includes means for mounting the sample, independent transducer supports, and means for bringing sample and transducer into nondestructive contact. Several sample holding devices and micromanipulator adaptations are described. The over‐all measurement system is briefly described together with a few typical results for metal foil and fine wire specimens. Some applications of the apparatus are listed.

ISSN:0034-6748    

DOI:10.1063/1.1719976

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A shorted superconducting coil carrying a persistent current can be made to reverse its field in less than 5 msec by subjecting the coil to an increasing external reverse field. The superconducting coil opposes a change in its interior field until its critical current is exceeded, whereupon rapid extinction of the persistent current occurs thus admitting the external field.

ISSN:0034-6748    

DOI:10.1063/1.1719977

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A specimen holder and a polishing unit with an automatic shutoff were designed for thinning disks taken from preselected areas of large metallic specimens or from specimens with small cross sectional areas. Since the disk precisely fits the specimen holder of the microscope, a supporting grid is unnecessary and deformation from cutting and handling after thinning is eliminated. The automatic shutoff device greatly improves conditions for transmission by stopping the polishing current at the optimum time.

ISSN:0034-6748    

DOI:10.1063/1.1719978

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A simple electron energy analyzer has been used to measure energy distribution functions of the ``hot electron plasma'' produced in a compression mirror machine. The analyzer is located in a region of a steady 1.2 kG field so that electrons which escape from the 23 kG mirror field have most of their transverse energy transformed into the parallel component. This parallel component of energy is determined by the transverse drift in a region of mutually perpendicular electric and magnetic fields; low velocity electrons drift farther as they spend more time in theE×Bfield region, and vice versa. Electrons are detected by being accelerated onto a plastic scintillator which is viewed through a light pipe by a photomultiplier. Good time resolution is obtained, but since only one narrow energy band can be observed on each shot, the electric field is varied between shots to measure the complete energy spectrum. The magnetic field of the analyzer joins smoothly with the plasma containment magnetic field so that the electrons do not pass through a zero field region. With the 1.2 kG field, the analyzer works well for electron energies up to 20 keV; at higher energies the energy resolution decreases, and at very low energies (<100 eV) secondary electrons cause difficulties.

ISSN:0034-6748    

DOI:10.1063/1.1719979

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An arc‐image stagnation‐flow reactor has been developed to study the rates of gas‐solid reactions between 2000 and 3000°K. Most refractory solids can be heated in this reactor to their melting points in a partial atmosphere of almost any gas except strong oxidizers such as fluorine. The standard deviation of a datum point, in the case of oxidation of tungsten by CO2at 100 Torr, is 6% at 2500°K, corresponding to a temperature uncertainty of ±9°K.

ISSN:0034-6748    

DOI:10.1063/1.1719980

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

J. Wadsworth and F. E. Stokes recently described a simple high speed camera. They formed an array of images using crossed rods of glass to form an array of small camera lenses, and each lens of this array formed a separate frame. They exposed successive frames by rotating a Nipkow disk in front of the crossed glass rods. Some years ago, I made some high speed cameras working on similar principles, but using lenticular plates as the array of camera lenses. Sequential operation could be by Nipkow disk or by control of the light sources, which could be an array of sparks, or more simply, the moving spot of a cathode ray tube. Rates of recording were in the range 105to 106pictures per second. The cameras are very simple and of low cost. They allow one to record long sequences of pictures. Picture quality was low but there is a reasonable prospect of improvement.

ISSN:0034-6748    

DOI:10.1063/1.1719981

出版商:AIP    

年代:1966

数据来源: AIP