摘要:

A spectrometer has been developed with the object of achieving a high diffraction efficiency, low background, and stability and convenience in operation. A mechanism is used to position the detector and crystal in relation to the sample, for determining extended spectra by Johann's and Cauchois' methods. Sample‐chambers with radiation shielding walls are used, and the outlet for fluorescent radiation is designed for reducing background. Microsamples can be used to simplify the evaluation of quantitative results. A vacuum‐chamber has been designed for further reducing background. 4×7 cm crystal lamellae on glass supports are prepared from blocks of NaCl or LiF and bent cylindrically for line focusing, or double‐curved for point‐focusing to increase the intensity at particular wavelengths, the focusing always being aberration‐free. The equipment has been calibrated for microquantitative determination of 30 elements, and an absolute sensitivity of 2×10−10g has been achieved for the elements Co&sngbnd;Zn.

ISSN:0034-6748    

DOI:10.1063/1.1716194

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The magnetoresistance effect of the metal bismuth has been used in measuring magnetic induction for many years. This report describes significant features of the electrical and mechanical design of an electrically temperature‐regulated resistor assembly and associated equipment. Commercial ductile bismuth wire was successfully used in a small probe. Useful resolution of 2 gauss in fields above 5000 gauss was readily attained. Limitations and advantages of bismuth resistors as devices for measuring magnetic induction are discussed briefly. Some data from the use of the first units are presented.

ISSN:0034-6748    

DOI:10.1063/1.1716195

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A method is presented for instantaneously obtaining a numerical value proportional to the area of a recurring voltage transient. The underlying principle is the summation of pulses from a generator whose repetition rate is a linear function of the instantaneous input voltage. The technique allows accurate gating to reduce the effects of unwanted signal and noise and has a high order of stability and linearity. The particular device actually constructed and tested was designed to measure the area of the roughly triangular voltage change, about 1 msec in duration, produced by ventral root nerve fibers activated in a monosynaptic reflex.

ISSN:0034-6748    

DOI:10.1063/1.1716196

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

We have modified a conventional concentric‐cylinder flow birefringence instrument (built by the Rao Instrument Company) by adding a photocell and a rotating disk that scans the annulus with a moving spot of light. In this way the optical intensity pattern formed in the image of the annulus by the combination of polarizer, analyzer, and quarter‐wave plate is converted into an electrical wave which is then analyzed by an electronic device. Full advantage can be taken of the increased sensitivity to birefringence caused by the presence of the quarter‐wave plate, since the presence of a bright background, so disturbing to the eye, is not important to the photocell. In effect, the system is converted to a linear dependence on the magnitude of the birefringence, instead of the quadratic one found in the conventional method of observation. The sensitivity is in fact increased by about a factor of ten over the same instrument used in the conventional way, and at the same time the measurements are made independent of the visual judgment of the experimenter. The linearity of the system also has considerable advantages when extraneous sources of birefringence are present, as is commonly the case.

ISSN:0034-6748    

DOI:10.1063/1.1716197

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An ultra‐high vacuum pump has been developed based on the combined effects of ionization, excitation and sputtering. A cold‐cathode discharge in magnetic field is employed with no hot filaments nor moving parts. The ultimate vacuum attainable is not yet known but is probably below 2×10−10mm Hg. A pumping speed of about 10 liters/sec for air has been recorded at 1×10−7mm Hg. The pump replaces liquid nitrogen‐trapped oil diffusion pumps for pumping microwave tubes.

ISSN:0034-6748    

DOI:10.1063/1.1716198

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A low‐noise 30‐Mc amplifier with Western Electric Type 416B triodes used in a cascode circuit is described. The theoretical noise figure of the amplifier, with the optimum value of source resistance, is 1.06 or 0.26 db. The amplifier is being used to study noise in semiconductors.

ISSN:0034-6748    

DOI:10.1063/1.1716199

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A conventional Stern‐Gerlach separation of hydrogen molecules is proposed for the supplying of a radio‐frequency or PIG ion source of standard type to produce microampere beams of polarized protons for acceleration in electrostatic accelerators, cyclotrons, etc. The long nuclear relaxation time of molecular hydrogen gas allows the accumulation of polarized protons (as molecules) for the production of microampere average beams by means of a pulsed ion source. The polarized protons after acceleration have the energy‐ and angular‐spread characteristic of the machine with which they were accelerated. There is no apparent reason why polarized H−may not be produced in the same strong‐field rf ion source, accelerated in a weak field to preserve polarization and stripped in a tandem machine, all without significant depolarization.

ISSN:0034-6748    

DOI:10.1063/1.1716200

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A calorimeter designed for measuring the heats of rapid reactions such as dissolution and hydrolysis near room temperature is described. The instrument consists of a sealed copper bomb suspended in an evacuated submarine immersed in a thermostat; stirring is accomplished by rocking the assembly through an arc of 150°. Measurements of the heat of solution of potassium chloride in water at 25.00°C have been performed.

ISSN:0034-6748    

DOI:10.1063/1.1716201

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The well‐known difficulties with preparation, handling, and mounting of thin foils are avoided by the use of aluminum oxide foils (25 to 250 &mgr;g/cm2, or 700 to 7000 A thickness) which are grown on a solid piece of mechanically shaped aluminum that serves also as the necessary robust frame. These foils have excellent properties for an application in the spectroscopy of particle and quantum radiation. A simple method for the mechanical and chemical preparation will be described. The foils are gas tight, smooth, and withstand a considerable pressure. A formula describes the relation between breaking pressure, diameter, and thickness for circular shaped foils.

ISSN:0034-6748    

DOI:10.1063/1.1716202

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A Rankine balance type magnetic susceptometer of much greater sensitivity than previously obtained and combined for the first time with a flow system for the study of chemical reactions is described. The instrument can detect in one measurement a change in volume magnetic susceptibility of 5×10−12emu. The response time is adjustable down to a fraction of a second by means of an electronic servo system. The time resolution of the flow system is presently limited by the flushing time of the cell to five seconds. A time resolution of hundredths of a second is feasible, as is the detection, in one measurement taking a second, of a change of 1.5×10−12emu corresponding to the rms Brownian force arising from air resistance to the motion of the magnet.

ISSN:0034-6748    

DOI:10.1063/1.1716203

出版商:AIP    

年代:1958

数据来源: AIP