摘要:

Experiments or devices requiring the joint use of liquid helium and magnetic fields can make use of superconducting electromagnets. Solenoids capable of producing up to 4300 gauss in large volumes are described. Higher fields, up to 14 kilogauss, have been produced by iron‐core superconducting magnets. A small power supply may be used to energize one of these magnets and then disconnected after a persistent current has been set up. A stable magnetic field is thus maintained for many hours if the magnet is kept cold.

ISSN:0034-6748    

DOI:10.1063/1.1716985

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The design of high field cylindrical solenoid magnets for continuous operation is discussed. Equations are given relating power input, allowable temperature rise, coolant rate, and pressure drop to give the detailed dimensions required for the electrical conductor and the cooling annuli. The stresses from electromagnetic forces acting upon conductors are discussed, equations are given, and some devices and factors concerned in resisting these forces are described. The properties of kerosene as a magnet coolant and safety precautions for its use are discussed. The details for a magnet with a 4‐in. air core, constructed for good homogeneity, and 7.5 megawatts of power are given. A procedure for preparing laminated insulation in the form of a spiral is described and a method of squaring the magnet ends to improve heat transfer, reduce heat production, and facilitate support at the ends has been devised. Equations are given which enable the evaluation of the conductor temperature at any point along the coil by making use of the temperature coefficient of resistance for thermometric purposes. A graph of conductor and kerosene temperatures as a function of axial length has been prepared from data obtained from magnet operation. The particular magnet described here, which is the first of several to be built, gave a field of 99 500 gauss at 7.5 megawatts. Some suggested improvements based on experience with the present magnet have been included.

ISSN:0034-6748    

DOI:10.1063/1.1716986

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Although a great variety of methods have already been described for measuring magnetic susceptibility, the present instrument has the advantage that it makes possible measurements on weakly magnetic high‐purity metals having extremely small resistivities. Most servo‐balances for measuring susceptibility that have been described in the literature have been for strong paramagnetics or ferromagnetics and in none of the balances has the effect due to strong induced eddy currents been allowed for. The present instrument consists of a sensitive electrodynamic balance which is operated as a null instrument by allowing it to form part of a servomechanical network. The feedback system provides a stiffness of balance movement of 8×104d/deg deflection. The sensitivity of this instrument is such that changes of 10−9emu/g may be detected in the susceptibility of large metallic samples having electrical resistances less than 10−9ohm cm.

ISSN:0034-6748    

DOI:10.1063/1.1716987

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The construction and performance of disk‐shaped thin‐walled flow counters suitable for measuring very small beta activities of solids is described. The circular faces, which serve as the cathode, consist of conducting films. Either a single pear‐shaped loop of wire whose plane is parallel to that of the faces, or a group of straight wires stretched across the midplane serves as the anode. The counters are operated in the Geiger region. Samples can be counted against both faces of the counter. Performance data are given for counters having active volumes ranging from 0.2 to 7 cc, and having active areas from 1.6 to 23 cm2. Counting efficiencies for natural potassium (mounted on Lucite) vary from 30% to 47%, depending on the relationship of sample area to counter dimensions. Inside a 20‐cm steel shield and an anticoincidence ring the background counting rates varied approximately as 1 count/hr/cm2of counting area. Backgrounds as low as 1 count/hr were obtained.The disk geometry permits the use of a smaller metal and anticoincidence shield than is possible with cylindrical geometry. Counters shielded successively with 1.9‐cm mercury, 5‐cm steel, and 5‐cm lead, and operated with a flat multiple‐anode anticoincidence counter (15 cm2), actually gave lower background than with the 20‐cm steel and anticoincidence ring assembly. An integral counter assembly, consisting of ∼2‐cm diam disk‐shaped counter and a disk‐shaped guard counter (∼7‐cm diam), was constructed and gave satisfactory results.

ISSN:0034-6748    

DOI:10.1063/1.1716988

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The construction of a unidirectional integrating precession camera is described. The camera is a modification of a Buerger‐Supper precession camera. It is designed to be used in conjunction with an integrating microphotometer. The instrument has been used to gather zero‐level data. Its reliability has been tested by measuring the intensity of the diffracted beams from a single crystal of sodium chloride. The results of the test show good agreement between single crystal data from the precession method and powder data from a spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1716989

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

It is experimentally shown that the ratio of light reflected by a nonhemolysed blood sample at two suitable wavelengths is a linear function of the oxygen saturation. A simple instrument to determine oxygen saturationin vitro, based on these findings, is described.

ISSN:0034-6748    

DOI:10.1063/1.1716990

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The White cathode follower is a two‐tube series device that provides output impedances of the order of 5 ohms and transmits pulses of either polarity with minimal distortion. A dc and transient analysis of the White cathode follower is made, and a typical circuit is analyzed. The effect on the transient response of varying the circuit parameters is discussed. Throughout the paper the White cathode follower is compared to the well‐known conventional cathode follower. The White cathode follower may have an advantage in gain‐bandwidth over the conventional cathode follower by a factor of five.

ISSN:0034-6748    

DOI:10.1063/1.1716991

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Accurate and convenient microwave cavity wavemeters are described that are suitable for many precise physical measurements. HighQ's were attained by refined construction techniques. At 9000 Mc a precision of 0.02 Mc was obtained. The absolute accuracy also may be very high after strains in the metal have stabilized. A calibration table containing 104entries, easily formed by means of a high speed computer, makes the wavemeters convenient to use. The curve fitting method, accurate to one in 106, is described.

ISSN:0034-6748    

DOI:10.1063/1.1716992

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

For Raman spectroscopy of gases, intense illumination is required. The relatively low tensile strength of transparent materials has always severely limited such studies at high pressures. This paper describes a method by which use is made of the very high compressional strength of glass. The essence of the method is that the compressed gas is contained in an enclosed spaceoutsidea thick‐walled glass tube; inside the tube a water‐cooled mercury lamp is inserted. Pyrex tubes of 0.5 in. i.d. and 0.75 in. o.d. thus withstand pressures in excess of 3000 atm. The scattered light is observed through a conventional self‐sealing window. High resolution Raman spectra have been obtained, for various simple gases, at pressures up to 2500 atm.

ISSN:0034-6748    

DOI:10.1063/1.1716993

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The high field solenoid described in this paper operates at liquid nitrogen temperature (78°K), and uses a relatively small dc power source (100 kw). It has operated continuously and steadily at 36 kgauss and 62 kw under steady state conditions. This is done by forcing the liquid nitrogen coolant through the annuli between the electrical conductors with a circulation pump. The first magnet designed has a 4.6‐cm diam core and the length is such that the central portion of the solenoid gives an experimental ``working space'' 10 cm in length where the field is quite uniform. The cost is modest compared to comparable water‐cooled solenoids both as to initial investment and operation.

ISSN:0034-6748    

DOI:10.1063/1.1716994

出版商:AIP    

年代:1960

数据来源: AIP