摘要:

Measurement and control circuits for recording small density changes by use of several photo‐tube circuits are given. The minimum drift rates obtained are 1×10−6part per minute with a differential photo‐tube circuit, 3×10−5part per minute with a single photo‐tube circuit, and 4×10−4part per minute with a photo‐multiplier circuit. The differential and single photo‐tube circuits have been used to measure density increments of roughly 2×10−4and 1×10−3with an accuracy of about 5 percent. These spectrophotometers are employed in studies of the kinetics of unstable intermediates in enzyme action. Although slow drift has been rendered negligible by suitable control circuits and stable amplifiers, the theoretical limit of performance is not achieved by this apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1741013

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1741014

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Design and construction details of d.c. and a.c. amplifier packages using subminiature tubes are given. In addition, applications to control and measurement circuits are shown. The purpose of these amplifiers is to decrease the time lost in the construction and repair of complicated electronic equipment for biophysical and other experiments.

ISSN:0034-6748    

DOI:10.1063/1.1741015

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A method is here described for generating circular cylindrical surfaces of large radius of curvature on blocks of steel or other material with a close approach to optical precision utilizing an ordinary machine shop surface grinder. Convex and concave surfaces about 3×5 inches in dimensions with radii of curvature of 79 inches (two meters) have been ground by this method both on cast iron and on stainless‐steel blocks with a precision of about 0.0002 inches as regards surface imperfections. A very moderate amount of subsequent lapping sufficed to give surfaces of optical precision. The surfaces are used for clamping lamina of crystalline quartz for use in a curved crystal focusing gamma ray spectrometer. A companion paper describes the gamma ray spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1741016

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Description is given of a transmission‐type, curved‐crystal focusing spectrometer for short wave‐length x‐rays, and gamma‐rays having a dispersion of 1.186 x.u. per mm at short wave‐lengths. The spectrometer utilizes the (310) planes of quartz in a crystalline plate of dimensions 80×70×1.0 mm curved cylindrically to a radius of two meters. High luminosity is obtained since the useful aperture in the crystal holder has an area of 10 cm2and subtends 0.00025 stereradians at the focus. It also affords high resolution since by photographic tests with x‐rays the curved plate has been shown to focus a specified x‐ray wave‐length to within 0.06 mm of the same position on the focal circle for all parts of its useful aperture and over the entire operating wave‐length range. The geometry of the mechanism permits absolute measurements with a precision screw of the sine of the Bragg angle on both sides of the reflecting planes, affording a wave‐length range which includes at longest wave‐lengths theK‐spectrum of silver and goes down to zero wave‐lengths. For short wave‐length gamma‐rays the source is placed at the focus. A multiple‐slit collimator of tapering die‐cast lead partitions spaced apart with tapering separators, is used at short wave‐lengths to transmit the monochromatic diffracted beam and absorb the directly transmitted and scattered heterogeneous beam. The present collimator limits the spectrum that can be studied to a shortest wave‐length of 7. x.u. corresponding to 1.75 Mev. The intensity of the diffracted beam is to be measured with a special multi‐cellular G. M. counting tube of high efficiency, provided with a number of thin lead partitions through which the beam passes successively. In photographic spectra made with this instrument the tungsten and also the silverK&bgr;1&bgr;3doublet is completely and clearly resolved. Reproductions of such photographic x‐ray spectra are shown in which the line breadths have substantially the natural breadth. Fluorescence spectra of silver have been made in 10‐minute exposures. A companion paper gives the all‐important precision technique of generating the curved cylindrical stainless steel clamping blocks for the crystal.

ISSN:0034-6748    

DOI:10.1063/1.1741017

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

In the routine testing of electronic equipment, particularly in a nuclear physics laboratory, there is frequently a requirement for a simple, lightweight pulse generator. The instrument described is built to fill such a role. It provides rectangular pulses of duration 1, 10, and 100 microseconds (or other chosen values) of amplitude smoothly variable from 0 to 75 volts. Either positive or negative pulses are available from low impedance sources, and an internal repetition rate, covering the range 1 to 10,000 cycles per second, is included. In addition, the circuit may be driven from an external signal generator, or a source of random pulses, where this is desired. The instrument has proved of utility in circuit research when used as a source of pulses in conjunction with a synchroscope.

ISSN:0034-6748    

DOI:10.1063/1.1741018

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A description is given of a chamber used for studying the angular distribution of scattering of neutrons by helium. This counter can be used either as an ionization chamber or as a proportional counter. Results of tests made with theN(n, p) reaction for slow neutrons are included. These tests show a width of the 0.6‐Mev line at half‐height to be about 35 kev, indicating that it should be possible to separate low energy neutron groups which differ in energy by about 50 kev.

ISSN:0034-6748    

DOI:10.1063/1.1741019

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1741020

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A compressor suitable for the delivery of air at pressures up to 12,000 p.s.i. is described. This unit employs a piston‐cylinder combination sealed by oil rather than a packed piston rod. This type of construction has been found to operate satisfactorily over a period of years and furnishes a supply of air at elevated pressures for the operation of equipment used in the investigation of the thermodynamic properties of fluids.

ISSN:0034-6748    

DOI:10.1063/1.1741021

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A ring‐decade counting circuit is presented, similar in design to that of Regener's. The triggering of the ring circuit has been further investigated, with reference to random pulses. A new input circuit is given so that the resulting scaler has a resolving time of 1.9 microseconds for any two consecutive pulses and 3.7 microseconds for any three consecutive pulses. A new simple method of indication is given which uses only a milliammeter and a triode instead of a cathode‐ray tube.

ISSN:0034-6748    

DOI:10.1063/1.1741022

出版商:AIP    

年代:1947

数据来源: AIP