bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulated Optical Null Spectrophotometer for Flash Excitation Reactions
Authors: Green Maurice , Tollin Gordon
Published: February 2005

A differential flash-photolysis kinetic spectrophotometer has been developed for studies of photo-induced reactions. The instrument system has a response time of 1.4 msec and an average differential sensitivity of 0.004 OD in the 400–700 nm region. A modulated monochromatic source and phase-lock detection are employed for signal-to-noise enhancement. The maximum actinic flash input is 360 J.
Focusing Properties of Magnetic Laminas and Their Applications to the Microtron
Authors: Campolattaro A. , Porreca F.
Published: February 2005

The possibility of attaining vertical focusing in small accelerating machines, like the microtron, without destroying their marked simplicity, is pointed out. Indeed, it is shown that a vertical focusing in low energy accelerators can be obtained by the location of a magnetic lamina inside and at a suitable distance from the equilibrium orbit. In the case of the microtron, the location of the lamina inside the first orbit and at a distance from the resonant cavity of 0.42 times the radius of this orbit produces a vertical focusing for all orbits. Experiments performed on a 2.5 MeV microtron are in agreement with the theoretical predictions.
Improvement of the Characteristics of Photo-Voltaic and Photo-Conductive Cells by Feedback Circuits
Authors: Rittner Edmund S.
Published: February 2005

The decrease of current sensitivity of photo-voltaic and photo-conductive cells with increasing load resistance can be avoided by maintaining constant voltage across the cell. Two stable electronic circuits are described which were designed to accomplish this end and to serve as amplifiers.
A Mechanical Switch for Use in Some Bioelectric Measurements
Authors: Hoyt R. C.
Published: February 2005

A rapid, mechanical switch for alternately applying current and measuring potentials in biological systems is described. The switch operates at 15 c.p.s., allowing d.c. instruments to be used for current and potential measurements. The switching method described allows changes in bioelectric potentials to be followed which would otherwise be masked by the large IR drop due to the applied current.
A General Purpose Linear Amplifier
Authors: Jordan W. H. , Bell P. R.
Published: February 2005

An amplifier that is suitable for use in a variety of nuclear-particle counting experiments is described. The high and low frequency response of the amplifier can be varied by means of a three-position switch. In the wide-band position the transient response to a step function is a voltage pulse with a rise time of 0.15 μsec. and a total duration of less than 0.5 μsec. In the narrow-band position a signal of 3 microvolts produces a voltage pulse at the output equal to r.m.s. noise. A pulse-height selector is included for measuring pulses up to 100-volts amplitude.
Ionization Currents from Extended Alpha-Sources
Authors: Blau M. , Carlin J.
Published: February 2005

A series of investigations on ionization currents from extended two-dimensional sources is described with immediate application to a new area measuring instrument. The sources of radiation employed were nickel disks uniformly coated with polonium. The results of these measurements interrelating saturation currents and voltages with polonium density, disk area, and alpha-particle range, are presented and discussed.
Note on the Efficiency of Radiation Shields
Authors: Lawson A. W. , Fano Robert
Published: February 2005

The familiar problem of radiation shields is analyzed by matrix algebra. A general method is developed for the calculation of the efficiency of thick radiation shields of infinite thermal conductivity. If the shields are thin, the method leads to an explicit, general expression for the efficiency of n radiation shields. It is found that, in this case, the ratio of the power required to maintain a radiating surface at temperature T with n thin shields to the power required to maintain the same temperature without shields is given by [{Σ lim 1n(1εmk+1εml)}−(n−1)]−1,where εmk and εml are emissivities of the two sides of the mth shield.
Experiments on the Design of Synchrotron Magnets
Authors: Parkinson W. C. , Grover G. M. , Crane H. R.
Published: February 2005

An important aspect of the problem of synchrotron magnet design is that of obtaining a given magnetic energy in the guide field with the minimum expenditure of iron, copper, and condensers. Tests were made on d.c. magnet models of several configurations, using as criteria (1) the ratio of the peak energy in the useful portion of the magnet air gap to the peak energy which must be stored in the condensers, and (2), the ratio of magnetic flux in the gap to the flux in the return path of the magnetic circuit. Comparative performance data are tabulated. The method of shaping the pole faces to obtain the desired fall-off of B with r over the greatest range in r is discussed, and a shape worked out by trial and error is given.
Electrostatic Accelerator for Electrons
Authors: Buechner W. W. , Van de Graaff R. J. , Sperduto A. , McIntosh L. R. , Burrill E. A.
Published: February 2005

An account is given of the design and operation of five electrostatic accelerators constructed to supply an urgent radiographic need of the Navy. Each generator is housed in a steel tank 4.5 feet in diameter and 10 feet long, the insulating medium being gas at 200 pounds gauge pressure. The x-ray generators are rated at 2-million volts but were frequently operated at somewhat higher potentials. Tests were made with various insulating media, including air, nitrogen, Freon, and sulfur hexafluoride. With a 3-foot extension to tank and insulating column and without a vacuum tube, a potential of 5.6-million volts was attained with sulfur hexafluoride. Both continuously pumped and sealed-off x-ray tubes were used. These were supplied by the Machlett Laboratories, Inc., following a cooperative development. The use of focal spots only .01 inch in diameter made possible radiographs of extremely high definition. Target currents up to 300 microamperes produced in this voltage range an x-ray output of great intensity and penetration.
An Instantaneous Recording Cardiotachometer
Authors: Sturm Ralph E. , Wood Earl H.
Published: February 2005

The instrument described records the time interval between successive r wave impulses of the electrocardiogram, thereby providing a graphic record of the rate of each beat. A description is given of the electronic circuits, which are of the simplest type, requiring a minimum of adjustment during construction. Tube and circuit elements are not critical in value and are available at any radio supply house. Application of the instrument in the measurement of the heart rate in man during exposure to positive acceleration on the human centrifuge is briefly discussed.
An Electrical Network for Determining the Eigenvalues and Eigenvectors of a Real Symmetric Matrix
Authors: Many Abraham , Meiboom Saul
Published: February 2005

An electrical network for determining the eigenvalues and eigenvectors of a real symmetric matrix of order n is described. It consists of n LC-circuits, each one coupled to each of the others by two condensers. The values of the condensers are adjusted according to the elements of the matrix. Both positive and negative values of the elements can be dealt with by changing the connections of the coupling condensers. The network is excited by a variable frequency source, the resonance frequencies being observed on an oscillograph. The eigenvalues are given by these resonance frequencies and the components of the eigenvectors by the voltages across the coils. The construction of the network and the operating procedure are described. The theory of the network when losses in the coils are taken into account is also given, and the case of multiple roots is discussed. The accuracy of the eigenvalues obtained is better than 0.1 percent of the greatest eigenvalue, while the accuracy of each eigenvector is about one percent of its greatest component.
A Laboratory Four-Channel Electronic Switch
Authors: Replogle F. S. , Albers V. M.
Published: February 2005

A four-channel electronic switch and amplifier designed for direct connection to the deflection plates of commercial oscilloscopes are described. The system permits the simultaneous presentation of four signals and responds uniformly to d.c. voltages and a.c. voltages with frequencies up to 100 Kc. It may be used for visual observation in this range, for film recording of the wave form of individual cycles up to 1 Kc frequency, and for recording the modulation on carrier signals with frequencies up to 100 Kc. A discussion of the principles, circuit, and results are given.
The Synchronization of Auxiliary Apparatus with a Betatron
Authors: Baldwin G. C. , Klaiber G. S. , Hartzler A. J.
Published: February 2005

A method is described by which the radiation from a betatron can be controlled by external apparatus; such as a cloud chamber, whether the betatron magnet is energized continuously from alternating current, or is ``pulsed'' by connecting the previously-charged capacitor bank to the magnetizing coils. Upon receiving an initiating signal from the cloud chamber, a relay and thyratron circuit actuates pulsing of the magnet if desired, and permits injection of electrons into the betatron vacuum tube only during a single cycle after the initiating signal. A series of three thyratrons delivers to output terminals a sequence of synchronizing signals at one-half cycle before injection, injection time, and the time of x-ray production; this permits various functions of the auxiliary apparatus to be synchronized with the betatron. By this method, a cloud chamber can be expanded shortly before electron injection into the betatron, so as to be fully sensitive at the time radiation is produced; the tracks can be illuminated and photographed within a short, adjustable interval after their formation, thereby reducing the effects of ion diffusion, distortions from turbulence, and the number of cosmic-ray or contamination tracks.
A Stable Selective Audio Amplifier
Authors: Sturtevant Julian M.
Published: February 2005

A selective audio amplifier is described, the center frequency and band width of which are readily changed. Both frequency-dependent and independent degeneration are used to give a high degree of stability and linearity. Direct coupling is used throughout each feedback loop, so that the circuit can be employed at very low frequencies.
Energy Sensitivity of Fast Neutron Counters
Authors: Barschall H. H. , Bethe H. A.
Published: February 2005

The energy sensitivity of counters using recoils from a radiator or recoils produced in a gas is discussed.
Spiral Chronograph for Measurement of Single Millisecond Time Intervals with Microsecond Accuracy
Authors: Emrich R. J.
Published: February 2005

A chronograph is described which measures time intervals up to 2000 microseconds with an error not exceeding one microsecond. The chronograph traces a spiral on a cathode-ray tube at a known constant angular velocity; the spiral trace starts with the reception of an electrical pulse marking the beginning of the time interval and stops with the reception of a second pulse marking the ending of the interval so that the number of revolutions in the spiral is a direct measure of the time interval. The cathode-ray tube screen is of long persistence so that an immediate measurement of the time interval, as well as a photographic record, is obtained. Measurements may be made as rapidly as one every 30 seconds. A circuit used in conjunction with the chronograph selects the beginning of a slowly rising pulse, sharpens the pulse to one rising in about 0.2 microsecond, and blocks all subsequent pulses from the chronograph until reset manually.
A Simple Pulse Converter for Gas Tube Applications
Authors: Reiffel Leonard , Rothschild Kurt
Published: February 2005

A circuit for gas tube applications is described by means of which it is possible selectively to reverse the polarity of pulses entering a given set of input terminals so as to obtain monopolar output pulses for bipolar input signals; this is accomplished without a serious time delay difference through the network for input signals of either polarity.
A Pulse Timing Circuit for Cosmic-Ray Research
Authors: Ticho Harold K.
Published: February 2005

This paper describes a timing circuit for the measurement of short time intervals between pulses from Geiger-Mueller counters. By means of a direct comparison with the frequency of a piezoelectric crystal time intervals from 0 to 10 microseconds can be measured within ±0.03 microsecond. This circuit has already been used at Climax, Colorado for the determination of the mean life of cosmic-ray mesotrons.
An a.c. Operated Mass Spectrograph of the Mattauch Type
Authors: Shaw A. E. , Rall Wilfrid
Published: February 2005

A mass spectrograph for chemical analysis of solid samples has been developed. The Mattauch arrangement of a 31° 50′ electric deflection followed by a 90° deflection in a magnetic field was used in order to obtain a large mass range in focus on one plate. The accelerating and deflecting voltages, and the current for the electromagnet were obtained from stabilized rectifier circuits connected to the 60-cycle a.c. supply. The electromagnet with 100 milliamperes gave a field of 18,800 gauss across a ⅛″ gap. During the introduction of the plate or insertion of new electrodes a gate valve was closed to isolate the spectrograph from the pumping system. In this way different samples could be examined rapidly. The ion source was energized by a compact Tesla transformer wound on Lucite cylinders. One exposure covered a mass range from any mass M to a mass 10M.
A Null Method for the Comparison of Two Ion Currents in a Mass Spectrometer
Authors: Nier Alfred O. , Ney Edward P. , Inghram Mark G.
Published: February 2005

A method of determining the ratio of two small currents which vary intermittently or continuously, but always have the same relative magnitudes, is described. Although applied only to the case of making precise measurement of ratio of two ion currents in a mass spectrometer for the purpose of measuring the relative abundance of isotopes, the method would be useful in other applications as well.
Design of Dynamic Condenser Electrometers
Authors: Palevsky H. , Swank R. K. , Grenchik R.
Published: February 2005

The theory and design considerations for dynamic condenser electrometers are presented. The main features of such instruments are simple and dependable operation, extremely low drift and high sensitivity. (10,000 divisions/volt is easily obtainable.) Also included is the description and performance of two instruments specifically designed to measure d.c. currents of the order of 10−15 ampere.
Magnetic Field Measurement in Beta-Spectroscopy
Authors: Cork J. M. , Shreffler R. G. , Shull F. B.
Published: February 2005

To measure precisely the instantaneous value of a magnetic field, a device consisting of a drum-armature wound on a Lucite form and rotated by a synchronous motor is described. The direct voltage output is taken off by commutator and brushes, both of silver, to a potentiometer. Changes of 0.01 gauss can be observed. A simple self-regulating circuit is described.
The Approximate Determination of Piezoelectric Properties by Measurements on Small Crystals
Authors: Burstein Elias
Published: February 2005

Procedures for testing and determining the piezoelectric properties of materials by measurements on very small crystals (1- to 3-mm cubes) are described. These include the Giebe-Scheibe method, the bridge method, and the antiresonance method. A mathematical analysis and an evaluation of these methods are also given. Data obtained from several tiny crystals are compared with data obtained from large specimens.
A Sensitive Direct Current Electrical Integrator
Authors: Gilbert R. W.
Published: February 2005

A permanent magnet-movable coil d.c. instrument mechanism is used as an oscillating relay for time integration of d.c. potential. It is operated in conjunction with an input-reversing relay and a vacuum tube circuit to promote oscillation, the frequency of which is proportional to the input potential, and the number of oscillations is related to the potential-time integral.

In operation the accuracy of integration is within 1 percent over an input-level ratio of over 100. And the energy demand from the source of input is comparable or less than that required to operate conventional d.c. indicating instruments.
A Pneumatic Infra-Red Detector
Authors: Golay Marcel J. E.
Published: February 2005

Work on infra-red detectors, and particularly on infra-red pneumatic detectors, pursued in the Signal Corps Engineering Laboratories from 1932 to date, has been briefly reviewed. A typical pneumatic infra-red detector and laboratory techniques are described.
The Technique of Bombarding Organic Compounds with Deuterons
Authors: Honig Richard E.
Published: February 2005

In order to study the chemical effects of heavy charged particles, a number of organic compounds—gases, liquids, and solids—have been bombarded with deuterons from the M.I.T.cyclotron. This work, carried out under American Petroleum Institute Project 43c, included paraffins, organic acids, salts, and some complex mixtures. Gas bombardments were made at approximately atmospheric pressure in a water-cooled gas chamber (volume: 2.54 liters) provided with a 2-mil copper window for the entry of the external deuteron beam. A thermocouple and a Bourdon gauge connected to a Microtorque potentiometer allowed the gas temperature and pressure to be recorded electrically at the control bench during the bombardment of liquids and solids. Water-cooled target-holders provided with 2-mil copper windows were mounted inside the gas chamber which served to collect the product gases. To prevent chemical reactions of the compounds with the metal parts, chamber and target-holders were gold-plated.
Time Lags in Geiger-Mueller Counter Discharges
Authors: Montgomery C. G. , Montgomery D. D.
Published: February 2005

The probability of the occurrence of a time lag in a counter discharge is expressed in terms of the probability of capture of an electron by an oxygen molecule. The capture probability is shown to be independent of the number of electrons produced and to correspond to a value for the capture cross section in agreement with direct determinations.
The Capacitative Commutator
Authors: Scherbatskoy S. A. , Gilmartin Thomas H. , Swift Gilbert
Published: February 2005

The design and construction of a vibrating capacitor-type electrometer is described. Experimental data are presented to show that this electrometer reaches, within a small factor, the theoretical limit of sensitivity. The principle of the electrometer is a time-varying capacitor at the input of the device, which inverts the low frequency signal to a relatively high frequency, and raises its energy level, thereby simplifying the amplification of the voltage being measured, permitting the use of ordinary vacuum tubes, and producing an electrometer that is mechanically rugged and free from long period drift. Stabilization is obtained by negative feed-back. The electrometer was originally developed for radiation well-surveying in the petroleum industry, but has found other application in general radiation measurements.
A Simple Technique for the X-Ray Determination of Fiber-Axes in Electro-Deposited Metals
Authors: Wyllie M. R. J.
Published: February 2005

A special camera has been designed for the determination of orientation in electro-deposited metals and its construction is described. An account is also given of a method of computing the numerical value of the fiber-axis of the orientated crystals from simple linear measurements on the films obtained using this camera.
New Meters Employing Light-Sensitive Cells for the Measurement of Erythemal Energy
Authors: Kerr George P.
Published: February 2005

The applications of some well-known principles to the measurement of erythemal energy with light-sensitive cells are described. In one meter described the differential current of two cells is registered, and by selection of the proper filter for each cell, this current can be made a measure of the intensity of radiant energy weighted approximately according to its erythemal efficiency.

In the other meter, the radiant energy to be measured is incident on a filter which transmits ultraviolet energy but absorbs visible energy almost completely. A phosphor having a suitable spectral sensitivity is then activated, and the resulting fluorescent light is transmitted to the cell through filters which totally absorb ultraviolet energy. The spectral response of the device is then almost identical to that of the phosphor.

Quantitative data are presented on the spectral and absolute sensitivities of the meters.
The Design of Fast Thermopiles and the Ultimate Sensitivity of Thermal Detectors
Authors: Hornig Donald F. , O'Keefe B. J.
Published: February 2005

The design criteria for fast thermopiles of maximum sensitivity are obtained, with particular reference to their use with interrupted radiation in infra-red spectroscopy. It is shown that since the heat capacity of short, fine wires can be made small compared to that of the receiver, the conventional construction has certain advantages over evaporated thermopiles. Sources of noise are discussed and it is shown that in the cases treated the noise caused by the temperature fluctuations of the receiver is somewhat less than that resulting from Johnson noise. If Johnson noise is the chief factor, the minimum detectable power in the form of incident radiation is inversely proportional to a quantity S=E/R½ (E=voltage sensitivity; R=thermopile resistance) defined as the absolute sensitivity. The optimum design of d.c. thermopiles is derived and a factor of merit for thermoelectric materials, Q/(κρ)½ (Q=thermoelectric power; κ=thermal conductivity; ρ=electrical resistivity) is obtained. Physical constants and factors of merit for various materials are tabulated. Cd–Sb and Te alloys have the highest factor of merit but it is concluded that their irreproducibility outweighs their slight advantages. General relations for the time constant are given in terms of the construction and it is shown that response times of less than 0.02 second are practicable. By using these relations the optimum design of thermopiles for use with interrupted radiation is obtained. Several concrete designs for use at a 5 c.p.s. interruption frequency are given. With a receiver area of 0.005 cm2 the incident radiation, interrupted at 5 c.p.s., equal to the Johnson noise in a 1 c.p.s. frequency range is 5×10−5 μwatts. At this frequency the response is 90 percent of the equilibrium value. Approximately the same performance may be obtained at 10 c.p.s. Using the best available materials this sensitivity may be almost doubled. If ideal materials should ever be found there is still an ultimate limit to the sensitivity of any detector, thermopile or bolometer, which measures temperature, set by the temperature fluctuations. At 300°K this limit of detection is 4×10−6 μwatt for a detector of 0.005 cm2 area and a measurement in a 1 c.p.s. frequency band.
Internal Cyclotron Targets
Authors: Reid Allen F.
Published: February 2005

Preparation of cyclotron targets to be used within the dee enclosure for the production of radio-elements is discussed from both the theoretical and the application angles. Both general and quantitative considerations are advanced in target design.
High Temperature Furnace for Electron Diffraction Studies
Authors: Gulbransen Earl A.
Published: February 2005

A furnace is described for use with the electron diffraction camera for the study of chemical and physical reactions occurring on surfaces up to 1000°C. The specimens are mounted in the body of a 25 Cr-12 Ni alloy block which is surrounded by a series of radiation shields. The metal block is heated internally by a tungsten-wire heating element mounted on a BeO core and operates in a hydrogen atmosphere. The several motions necessary for manipulation of the specimens are accomplished through a Wilson seal. Temperatures of 1000°C are achieved with a heat input of the order of 450 to 500 watts in forty minutes. The use of the furnace is illustrated.
A Study of Pulse Shapes in a Parallel-Plate Ionization Chamber
Authors: Sherr Rubby , Peterson Rolf
Published: February 2005

The general features of electron collection in a parallel-plate ionization chamber are discussed with reference to the detection of single particles. If the particles come from the surface of one of the electrodes and end their paths within the chamber, the pulses obtained by electron collection can give information regarding the energy of the particles, their range, the angle between the tracks and the field of the chamber, and their ``range-energy'' function. Electronic and photographic measurements are described which confirm the expected form of the pulses and indicate the quantitative possibilities of this method of detection.
A High Resolving Power, Curved-Crystal Focusing Spectrometer for Short Wave-Length X-Rays and Gamma-Rays
Authors: DuMond Jesse W. M.
Published: February 2005

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 cm2 and 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 the K-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 silver Kβ1β3 doublet 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.
Counter for Use in Scattering and Disintegration Experiments
Authors: Koontz P. G. , Hall T. A.
Published: February 2005

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 the N (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.
A Laboratory Compressor for Higher Pressures
Authors: Sage B. H. , Lacey W. N.
Published: February 2005

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.
A Versatile Electronic Stimulator for Nerve and Muscle
Authors: Nastuk William L. , Borison Herbert L.
Published: February 2005

A simple, inexpensive, reliable electronic stimulator for student and research use is described. It includes many features which are generally found only in more complex instruments. The stimulator is especially useful in carrying out a number of fundamental experiments which demonstrate physiological properties of nerve and muscle.
Studies of Thermal Injury. VIII. Automatic Recording Caloric Applicator and Skin-Tissue and Skin-Surface Thermocouples
Authors: Henriques F. C.
Published: February 2005

An automatic recording caloric applicator is described and evaluated. This apparatus enables the skin surface to be brought immediately to and maintained at a constant, predetermined temperature. Further, it continuously records the rate of the perpendicular flow of heat through this skin site during the entire heat exposure.

A 120×0.04-cm stainless-steel hypodermic needle thermocouple is described and evaluated. This instrument was designed to enable a 10- to 25-cm lateral penetration of cutaneous and subcutaneous tissue and, therefore, is especially suited to the measurement of temperature changes within a skin site subjected to the caloric applicator. In view of its small diameter, maneuverability, accuracy, and non-fragility, this trocar is well suited for the measurement of tissue temperatures in general.

A 0.05-mm wire thermocouple of simple design, which was constructed to measure ``true'' skin-surface temperature, is described and evaluated.
Vacuum Pumping Equipment and Systems
Authors: Sullivan H. M.
Published: February 2005

Typical rotary mechanical pumps, booster pumps, and diffusion pumps available today are described. Fundamental operating principles are discussed. The method for making theoretical computations of the conductance and speed of evacuation of a vacuum system is outlined.
A Study of Adjustments of a Zinn-Type Ion Source
Authors: Jorgensen Theodore
Published: February 2005

The ion current from a Zinn-type ion source has been determined for various values of three parameters of the source. These parameters are the diameters of the probe and plate holes and the spacing of the nose and plate. The ion current from the source was found to increase linearly with the diameter of the plate hole up to a certain value while above this value there was little further increase. The ion current likewise increased with probe hole diameter, but the increased gas flow prevented extensive increases in this parameter. A smaller gap between nose and plate gave the maximum ion current for a smaller current to the filament and therefore at a smaller power dissipation in the arc. Gas consumption was 10 cc per hour.
Unidirectional Pulse Operation of a 22-Mev Betatron
Authors: Koch H. W. , Robinson C. S.
Published: February 2005

A circuit is described for providing unidirectional current pulses to a betatron magnet. By means of the resulting pulses of magnetic flux, electrons have been accelerated in a 22-Mev betatron. Minor changes are necessary in the methods of electron injection and orbit expansion used with a continuously excited betatron magnet.
The Measurement of Radioactivity in Solution
Authors: Solomon A. K. , Estes Hilliard D.
Published: February 2005

The conditions for measuring radioactivity in solution have been examined, and recommendations are given for optimum counting efficiency. The relative sensitivity of a dip counter has been found to compare favorably with other methods of counting, provided the beta-radiation being measured has an energy of about 1 Mev or higher.
An Improved Conductance Bridge
Authors: Foy Walter L. , Martell Arthur E.
Published: February 2005

The design and construction of a bridge for the determination of the conductance of electrolytic solutions is described. The best recommendations of other workers are incorporated into the apparatus, and a number of new features and improvements are included. An important characteristic of the bridge is the fact that it may be constructed from easily obtained parts. The instrument has considerable accuracy over a wide range of resistance and may be adapted to the measurement of capacitance.
A Counter for Low Energy Ionizing Particles
Authors: Thomas H. C. , Underwood N.
Published: February 2005

A counter which combines large solid angle, low operating voltage, ease of changing source, and ability to detect particles of very low energy is described.

By means of a revolving plate a sample may be rotated to a position inside the counting chamber through which helium is slowly passing. A large solid angle with low operating voltage is achieved by placing side by side several semicylindrical cathodes whose central wires are electrically connected.

Fe55, which has a half-life of four years, was used as a sample with which to examine the operational characteristics of the counter.
An Electrokinetic Transducer
Authors: Williams Milton
Published: February 2005

A description is given of a transducer which utilizes, for the transformation of sonic to electrical energy, the electrokinetic potential developed by the movement of a fluid through a porous solid. The construction and calibration of the transducer are discussed, and results of measurements of the pressure fluctuations in oil pipe lines are presented.
A Simple Temperature Controller
Authors: Mouzon J. C.
Published: February 2005

A simple electronic temperature controller has been developed which incorporates ``proportional'' control action. Utilizing a resistance thermometer element, its precision of operation is determined ultimately by the stability of the resistance element and the gain of the amplifier. Its operation is essentially independent of line voltage.
A Comparison of Mercury Diffusion Pumping Speeds for Five Gases
Authors: Fluke Donald
Published: February 2005

Mercury diffusion pumping speeds for hydrogen, helium, air, argon, and Freon have been measured for a pump of small aperture and found to vary inversely as the square root of the molecular weight.
A New Pump
Authors: Lewis Louis W.
Published: February 2005

A new type of pump is described which has the unique property of being able to move a fluid without change in pressure, volume, or temperature. Against a small external resistance, it can be used for pressure, vacuum, or circulation of a gas, and with a simple attachment, liquids may be pumped.
The Photo-Multiplier Radiation Detector
Authors: Marshall Fitz-Hugh , Coltman J. W. , Bennett A. I.
Published: February 2005

The photo-multiplier radiation detector consists of a commercial multiplier photo-tube arranged to register the scintillations produced in a fluorescent screen by radiation quanta. The signal pulses thus obtained are large for alpha-particles and other high velocity ions, much weaker for x-rays, gamma-rays, and high velocity electrons. The method is limited by the presence of noise pulses caused by electrons thermally emitted at the photo-cathode; signal pulses can be discriminated from noise pulses only to the extent that their amplitudes are greater. Satisfactory detection of the weaker signal pulses has been accomplished by careful attention to (1) selection of photo-tubes, (2) choice of fluorescent screen, (3) efficient collection of light, and (4) proper circuit design.

The new detector is especially suited to narrow-beam measurements where high counting rates are desired. However, it compares favorably with conventional detectors even when low counting rates and weak signal pulses are involved. The detector is rugged and fast, requires no special thin-window technique, and shows high efficiency. The primary detecting medium, being a solid, has high absorption and is well defined in position.

This article includes full construction details, an analysis of performance characteristics, particularly with weak signal pulses, and numerous suggestions for further improvement.
The Speed of Oil and Mercury Diffusion Pumps for Hydrogen, Helium, and Deuterium
Authors: Dayton B. B.
Published: February 2005

Data on several standard diffusion pumps indicate that the speed for hydrogen may be considerably less than 3.8 times the rated speed for air depending on the jet design, pump fluid, heater input, and speed of the fore pump. Evidence is presented that this reduction in speed is partly the result of diffusion of hydrogen back through the vapor jet from fore vacuum to high vacuum and partly the result of diffusion of hydrogen back out of the jet after entering from the high vacuum side. Measurements of the back diffusion of hydrogen, helium, and air in an experimental pump are correlated with the diffusion coefficient through an extension of the theories of Gaede and Matricon. The mechanism of jet breakdown has been observed with the aid of a glow discharge and a pilot dye.
Some Properties of BF3 in Ionization Chambers
Authors: Bistline John A.
Published: February 2005

Measurements of the collection of electrons in BF3 due to alpha-particle ionization pulses are described. Comparison of pulse heights showed that 1.33 as much energy is required to produce an ion pair in BF3 as in argon. The mean drift distance of an electron before capture in BF3 at 76 cm varies from 1.25 cm at an E/P of 5 (volts/cm/cm of Hg) to 7.25 cm at an E/P of 20. The drift velocity is observed and varies from 0.5×106 cm/sec. to 2.5×106 cm/sec. over the range of E/P used. The method of preparation of pure BF3 is described.
A Vacuum Spectrograph for the Infra-Red
Authors: Badger Richard M. , Zumwalt Lloyd R. , Giguère Paul A.
Published: February 2005

A description is given of a 1-meter focus vacuum grating spectrometer for the infra-red which is distinguished by its versatility and compactness of design. The vacuum container is tubular in form and all optical parts are mounted on a carriage which is readily retractable from the case for adjustment. A novel feature is the use of a sine screw drive which gives a linear wave-length scale. A representative spectrum tracing is given.
The Electron Multiplier as a Counter for 10-Kev Protons
Authors: Robson J. M.
Published: February 2005

Electron multipliers similar to the type described by J. S. Allen are being used as counters for low energy protons. Multipliers with electrodes made from soft beryllium copper count protons in the energy range 5 kev to 10 kev with an efficiency between 80 percent and 100 percent. Efficiencies of about 100 percent have been obtained with a radioactive alpha-source and about 0.2 percent with a RdTh gamma-source.
Constant Temperature Operation of the Hot-Wire Anemometer at High Frequency
Authors: Ossofsky Eli
Published: February 2005

Constant temperature operation of the hot-wire anemometer offers advantages in the study of large velocity fluctuations, of frequency as high as 30,000 cycles per second. To avoid spontaneous oscillations in this type of instrument a carefully designed bridge and amplifier are necessary. Such a design, treating the whole instrument as a feed-back amplifier, is presented, and minimum requirements for the amplifier proper are found in terms of wire parameters. The thermal noise level of the constant temperature instrument is calculated to be five times higher than that of a comparable constant current instrument because of the additional band width necessary for stable operation.
A Linear Electron Accelerator
Authors: Ginzton E. L. , Hansen W. W. , Kennedy W. R.
Published: February 2005

The theory, design, and some experimental results relative to linear electron accelerators are discussed. It is shown that, though the orbits are unstable, this instability is so small as to be negligible in general, provided the electrons are injected at relativistic velocities. Likewise, space-charge spreading may be neglected. The optimum loading design is found for various types of power feeds and curves are given by means of which any design may be evaluated. A number of illustrative cases are discussed. Operation of a low power, 38-section accelerator is described.
Voltage Regulators of the Shunt Type
Authors: Hoyle Wilfred G.
Published: February 2005

A general equation for the shunt regulator is derived, giving the relation between the nominal required input voltage and the maximum shunt regulating current for any per unit variation of the input voltage, and for any load. The necessary relation between the shunt regulating current and the output current for maximum electrical efficiency is obtained. It is shown that, for a fixed load, the maximum average efficiency of any shunt regulator is (1 − (k)½)2, where k is the maximum per unit variation of the voltage to the regulator.
A High Resolution Nuclear Spectrometer
Authors: Langer Lawrence M. , Cook C. Sharp
Published: February 2005

A magnetic spectrometer for the measurement of beta- and gamma-ray energies has been constructed. By using an inhomogeneous field varying radially in the proper manner, it is possible to bring electrons which leave the source with an extremely wide spread in angle to essentially a perfect focus in 180°. It has thus been possible to use a large mean radius of curvature of 40 cm in order to obtain high resolution combined with a reasonable transmission of about 0.1 percent of the total solid angle. Under operating conditions, with a 0.4-cm wide source, the full width at half maximum for an internal conversion line is 0.5 percent. Scattering and background effects are negligible.
Alpha-Particle and Deuteron Tracks in Eastman NTA Photographic Plates
Authors: Brock Robert L. , Gardner Eugene
Published: February 2005

Eastman NTA photographic plates have been bombarded with alpha-particles and deuterons in the 184-in. Berkeley cyclotron, and photomicrographs of sections of tracks have been made and are reproduced here. The trajectories do not lie in the emulsion for the entire range of the particles, and only short sections of track are available for study. In the tracks of low energy alpha-particles, and low energy deuterons, there are enough developed grains so that the tracks are nearly continuous. As the energy increases, the number of developed grains in the track decreases, the number for the deuterons decreasing more rapidly than that for the alpha-particles. In the tracks of alpha-particles of 200 Mev and lower, and of deuterons of 20 Mev and lower, there are enough developed grains so that the tracks can be followed easily.
Vacuum Properties of Synthetic Dielectrics
Authors: Hogg Benjamin G. , Duckworth Henry E.
Published: February 2005

An experiment has been done to determine the relative vacuum properties of a number of the commercially available synthetic dielectrics. The results show wide differences in vapor pressures and indicate that certain materials are particularly well adapted for use in vacuum systems.
The Vacuum Divider: A Low Pressure Multiplier
Authors: Monk G. W.
Published: February 2005

An instrument utilizing a 5-liter per second diffusion pump is described which allows pressures in the range 0.01 to 5 microns to be measured on a Pirani, thermocouple, McLeod or any other gauge ordinarily operating in the 0.5- to 50-micron range.
A Ball-Bearing Drive for the Ultracentrifuge
Authors: Ecker Paul Gerard , Blum Josef
Published: February 2005

A design for a simple stable ball-bearing support for ultracentrifuge turbines is presented. The ball-bearing drive eliminates the axial oscillations associated with the use of the air bearing.
A Proton-Controlled Magnetic Field Regulator
Authors: Packard Martin E.
Published: February 2005

A magnetic field discriminator is described which uses the nuclear induction signal from protons to give a ±75-volt change of d.c. voltage for a ±0.3-gauss change in magnetic field without using direct coupled amplifiers.

An ordinary degenerative current regulator with the addition of information from the magnetic field discriminator will control a magnetic field to within 0.02 gauss for a 10 percent line voltage change or for normal changes in magnet geometry.

The magnitude of the magnetic field is maintained in terms of a frequency, the value of which gives the absolute magnitude of the magnetic field.
A Mass Spectrometer Magnet
Authors: Anker H. S.
Published: February 2005

A magnet with ring-shaped pole pieces and a central core makes a large reduction in weight possible, thus eliminating the main obstacle to the use of π-radian mass spectrometers.
Vacuum Systems, Seals, and Valves
Authors: Kurie Franz N. D.
Published: February 2005

This paper is concerned with certain aspects of the technique of all-metal, kinetic vacuum systems which have proven their reliability. A brief account is given of the constitution of a system to operate down to pressures of the order of 10−5 mm. Precautions to be observed in assembling such a system and in its general care and maintenance are discussed. In all systems reliable, high speed valves are needed. Some which are quite satisfactory for many uses are available. In the event that it is necessary to construct such a valve, a modification of a standard brass gate valve is described. The problem of rubber gaskets is discussed in some detail, and suggestions are made which may relieve some of the difficulties which are occasionally encountered with them. The attention of experimenters is called to the usefulness of O-rings and a number of examples of their use is given.
Some Geiger-Müller and Proportional Counters of Spherical Shape
Authors: Salvini Giorgio
Published: February 2005

A Geiger-Müller counter with a spherically shaped cathode is described. The pulse shape from this counter is similar to that of cylindrical counters. It may be used satisfactorily in ordinary coincidence work.

Some of the counters, slightly modified to avoid spurious discharge, were filled with boron trifluoride and used as proportional counters for detection of neutrons.
Sensitive Ultraviolet Meters
Authors: Pal A. B.
Published: February 2005

A glow tube with thorium electrodes can be used to measure the intensity of ultraviolet light. The simple circuit used for this purpose does not give reliable results for photo-currents below 10−10 amp., and the exposure time to light may become several hours. The writer has devised certain improved methods which can measure small photo-currents of the order of 10−13 amp., requiring an exposure time of only a few minutes. If the exposure time is increased to several hours, then it is possible to measure currents even below 10−14 amp., provided the components are carefully insulated.
A Mass Spectrograph for Radioactive Isotopes
Authors: Lewis Lloyd G. , Hayden Richard J.
Published: February 2005

A mass spectrograph for the separation of small quantities of radioactive isotopes is described. This allows a direct determination of the mass numbers of radio-isotopes. It also permits the determination of the radiation characteristics of each of several radio-isotopes of an element where these have long half-lives, or have half-lives of the same order of magnitude. Slit counter and photographic plate techniques for analysis of deposits are described. An example, the analysis of a rare earth mixture, is described.