bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvements in the 21-Foot Normal Incidence Vacuum Spectrograph
Authors: Harrison George R.
Published: February 2005

The twenty-one foot normal incidence vacuum spectrograph previously described by the writer has been improved by the provision of 30,000 line per inch glass and speculum gratings in addition to the 15,000 line per inch grating previously used, and by the installation of a simpler and much more rapid pumping system. The previous range of 2000 to 1000A has been extended so that the instrument can be used from 6000 to 300A, and orders up to and including the sixth have been photographed, giving dispersions ranging between 2.72A/mm and 0.22A/mm with the advantages of an almost normal spectrum. When a constant value for the dispersion is used over a 16 inch plate the correction factor seldom exceeds 0.3A. The errors introduced when Rowland's method of coincidences is used with these Wood gratings appear to be much less than 0.01A. Wave-lengths of numerous lines of the hot-spark spectra of copper and nickel, and of the high frequency discharge spectra of argon and neon, have been measured with the instrument, and the accuracy of many of the measurements appears to be in the neighborhood of ±0.005A. The resolving power thus far attained, while still below the theoretical limit of the gratings, is far above that previously claimed for this region. Instead of the four four-stage mercury condensation pumps previously used, a single steel oil condensation pump of eight inch internal diameter is used, together with a trap in which either solid CO2 or circulating tap water can be used as refrigerant. All high vacuum connections are of 8 inch steel tubing, and a satisfactory stopcock of this bore has been constructed. A new type of vacuum gate for installation between the main spectrograph body and the camera box is described. A vacuum of about 2×10−4 mm is found sufficient to photograph the complete spectrum covered by the instrument without appreciable absorption in the optical path of 42 feet; a higher vacuum can be obtained in the tube quite readily.
An Apparatus for the Growth of Metal Single Crystals
Authors: Hasler Maurice F.
Published: February 2005

A simple crystal growing apparatus is described which allows the production of very uniform single crystalline rods of low melting point metals. The crystals may be produced in any desired gas atmosphere or in a vacuum. Any orientation of crystal to rod may be obtained by a simple seeding procedure.
A Method for Realizing the Full Amplification Factor of High Mu Tubes
Authors: Schmitt Otto H. A.
Published: February 2005

In order to utilize even 25 percent of the theoretical amplification factor of high mu tubes, it is necessary to use a plate load resistance and plate potential too high to be practical. By the use of a dummy tube in the plate circuit, however, one can obtain a resistance characteristic which makes it possible to attain the full amplification of 1500–2500 per stage for the ``57'' tube using only 300–600 volts plate supply. Output voltages as great as 450 volts are attainable with negligible distortion.
A Vacuum-Tube Voltmeter with Logarithmic Response
Authors: Hunt Frederick V.
Published: February 2005

A new vacuum-tube voltmeter which has a response proportional to the logarithm of the input voltage is described. The operation of the device is based upon the distortion of the plate-current wave form occurring in a tube of the ``variable-mu'' type, and upon the use of a diode rectifier to select only that portion of the wave which has been ``compressed'' by the curvature of the tube characteristic. The elementary circuit may be cascaded for extension of the range of input voltage over which the response is logarithmic. The speed of response of the device to changes in signal intensity is practically unlimited, and the frequency fidelity is only slightly inferior to that of a comparable impedance-coupled amplifier designed for the same frequency band. Commercially available tubes are used throughout.
A Differential-Gear Speed Controller
Authors: Lansing William D.
Published: February 2005

A speed controller for a direct-current motor has been constructed, operating on the principle of the differential gear. It has been found that the speed of the direct-current motor is controlled by this arrangement with about the same degree of accuracy as the regulation of the frequency of the controlled-frequency a.c. power line which serves as a standard.
The Electrolysis of Sodium Through Pyrex Glass
Authors: Pike Eugene W.
Published: February 2005

A method for introducing gas-free sodium into a vacuum tube by electrolysis through Pyrex glass is described.
Temperature Coefficient of the Elastic Moduli of Spring Materials Used in Instrument Design
Authors: Brombacher W. G.
Published: February 2005

A summary is presented of the values obtained by various observers of the temperature coefficients of the modulus of rigidity and Young's modulus of elasticity for the metals and alloys of possible usefulness in the construction of the elastic members of instruments. The composition of each material is given and also the condition of heat treatment or cold work. Much of the data is the result of recent work at the Bureau of Standards.
On the Quantitative Theory of the Toepler-Holtz Static Machine. II
Authors: Simon A. W.
Published: February 2005

The complete quantitative theory of an eight-carrier bisymmetric Toepler-Holtz static machine with output circuit is developed. The original potentials being considered as given, the potentials (and charges) corresponding to any subsequent angle of rotation are calculated, inclusive of the transient state which occurs when the carriers make contact with the brushes. In the permanent or stable state the potentials (and charges) increase by a constant factor per eighth revolution, this factor being a function of the electrostatic coefficients of the elements of the machine in the configuration where they just break contact with the brushes; also in the permanent state the potentials of similarly placed elements are equal in value but opposite in sign. The transient currents which flow when the carriers make contact with the brushes are exponentials, the time constants being functions of the resistances and potential coefficients (or, inversely, capacity coefficients) involved in the machine. The energy formula is derived and applied to a determination of the energy loss occurring when the various conductors share charges. Finally, it is indicated how the theory can be applied to various other forms of static machines of the Toepler-Holtz type. The general method developed is applicable, moreover, to any sectored static machine.
Eclipse Cinematography
Authors: Korff S. A.
Published: February 2005

The technique of obtaining a motion picture record of a total eclipse of the sun is described. The extreme brightness of the solar image during the partial phases results in special filter problems. The slowness of the motion across the solar disk requires that exposures shall be made at longer than normal intervals. During totality a fast lens is required, and a higher film speed is desirable. A long focus and well-corrected lens should be used to give an image of sufficient size to show detail. The scientific value of such a record, especially as an aid in determining exact times of contact and duration, is pointed out.
A Large Grazing-Incidence Vacuum Spectrograph
Authors: Kruger P. Gerald
Published: February 2005

A grazing-incidence vacuum spectrograph for a twenty-one foot focal-length grating has been set up and adjusted. The angle of incidence is 79 degrees. The various adjustments on the instrument which enabled rapid focussing are described. Very sharp lines have been obtained, and some spectrograms of copper are compared with others which were taken by a one-meter grazing-incidence vacuum spectrograph. These definitely show the advantage of the large dispersion of the new instrument. Several groups of lines have been found which appear to be multiplets but as yet have not been classified. Work is being continued on Be, B, Al, Cu, Ni, Co and Zn.
A Practical Vacuum-Tube Circuit for the Measurement of Electromotive Force
Authors: Ellis Samuel B. , Kiehl Samuel J.
Published: February 2005

A sensitive and accurate method is described for measuring electromotive force through large resistances, up to around 100,000 megohms, or for measuring electromotive force in systems which are easily polarized. The measuring instrument is simply and inexpensively constructed of standard parts which are readily available, and in actual use it is convenient, dependable and rugged.
A. Ångström's Total Immersion Hydrometer
Authors: Gaehr Paul F.
Published: February 2005

The present paper presents a study of this hydrometer and makes several suggestions: (1) Care must be exercised in the choice of ferrous material for the core and of the weight of that core. Permalloy is recommended. (2) Unless permalloy is used, a mixture of d.c. and a.c. is recommended for producing the magnetic pulls, only the d.c. being measured. (3) The equations are used to give hints for calibration and design.
A High-Gain Audiofrequency Amplifier
Authors: Verman Lal C.
Published: February 2005

The design of a three-stage high-gain amplifier for laboratory use in audiofrequency investigations is described. Four-electrode tubes are used as screen-grid amplifiers and an amplification of the order of 200 per stage is obtained. The inaccuracy of McDonald's formula for calculation of stage-gain has been pointed out. The gain-frequency characteristics are given for power as well as voltage amplification. It is shown that extreme care is necessary in the design of shielding to obtain high-voltage amplification of the order of 120 decibels as obtained in this three-stage amplifier.
The Calibration of an Infrared Spectrometer with a Rocksalt Prism
Authors: Cross Paul C.
Published: February 2005

The dispersion data for rocksalt originally determined by Paschen are corrected to 25°C with the use of temperature coefficients derived from the measurements of Liebreich. Values of the angle of minimum deviation of a 60° prism and the prism table angles from the sodium D lines for a spectrometer with the Wadsworth mounting of a 60° prism and plane mirror are calculated for 25°C. Tables are given with which corrections may be easily made for temperatures other than 25°C and for prism angles between 59 and 61°.
An Automatic Apparatus Assembly for Thermal Analysis
Authors: Eddy C. T.
Published: February 2005

The apparatus described was developed to make possible a determination of thermal critical temperatures and the temperatures at which allotropic modifications take place, etc.; such determination to be accurate enough to be the basis for investigating the constitution and for determining or modifying heat treating practices for alloys now being investigated at the Michigan College of Mining and Technology. The assembly has been found satisfactory because of its flexibility and degree of accuracy and because of the ease with which it is operated, the arduous task of constant observation by a laboratory technician not being required as in the case of most similar apparatus. In addition, the apparatus is flexible and can be used for investigating other properties such as resistivity and thermoenergy. The records are made automatically and are sharp and easily read and interpreted. The important parts of the apparatus are standard, easily obtained and readily assembled; this constitutes an additional and important advantage.
Practical Methods of Starting the Conduction in Mercury Arcs
Authors: Buttolph L. J. , Dana D. W.
Published: February 2005

This article reviews the various methods previously used to initiate the discharge in commercial types of gaseous conduction arcs and details a recently developed method with the use of a copper oxide rectifier to supply direct current for the starting of alternating-current arcs.
Direct Fusion Method for Determining the Radium Content of Rocks
Authors: Evans Robley D.
Published: February 2005

New principles for removing radon from rocks and for measuring minute quantities of radon are presented. Powdered rock specimens are boiled without flux by direct heating in an evacuated, graphite-resistance furnace. The duration of heating is 2½ minutes, which is to be compared with about one hour for the quickest of former methods. The gases from the melt are led to the ionization chamber through an electrostatic ion-trap. A small insulation drying device in the ionization chamber protects the amber from water vapor. The natural observational limit for measurements of small quantities of radon is defined as the point at which the average ionization from the radon just equals the probable statistical variation in the background ionization due to cosmic and local radiation, and an apparatus is described which permits measuring radon down to this limit. A string electrometer measures only the difference in ionization in two identical ionization chambers, both of which contain the same background gases, but only one of which contains the radon to be measured. A systematic study of the percentage of the total radon removed from biotite granite as a function of (a) temperature, (b) duration of heating, (c) fineness of sample grains, showed that temperature is the only important factor, and that 1800°C effects complete radon removal.
A Simple Method of Determining the Refractive Index of a Liquid
Authors: Gladden Sanford C.
Published: February 2005

A simple method of measuring the refractive indices of transparent liquids is described, in which a watch-glass serves to give the liquid the form of a plano-convex lens. The image of the maker's trademark on an incandescent lamp is focussed by means of the liquid lens on a movable screen. The screen is supported on an optical bench mounted vertically. By using the image equation, 1/a+1/b=(n−1)(1/R), the refractive index, n, may be determined. A Wallace type G color filter is employed to give results comparable with the values of n determined with Na light. Results are given for distilled water, toluene, benzene and carbon tetrachloride. The greatest source of error lies in the vibration of liquids of low viscosity, which introduces difficulties in focussing.
The Measurement of the Power Factor and Capacitance of a Condenser by Comparison with a Mutual Inductance
Authors: Smith Arthur Whitmore
Published: February 2005

In this method a capacitance is compared with a mutual inductance in a 1000-cycle a.c. network. The secondary of the mutual inductance is in the telephone bridge circuit and carries zero current. By using a Wagner ground circuit there is complete silence in the telephone at the balance point. When used as a substitution method two nearly equal condensers can be compared with each other with an accuracy that is much greater than that of the resistances employed. The final balance is obtained by adjusting a small variable self-inductance in series with the primary of the mutual inductance. For a given capacitance and frequency the value of this self-inductance is directly proportional to the power factor of the condenser, and the scale of this inductance can be calibrated to read directly the value of the power factor. Vector diagrams are given to show the relations among the capacitance, power factor, and the inductances, and a few typical measurements are recorded.
On the Technique and Design of Wilson Cloud-Chambers
Authors: Dahl O. , Hafstad L. R. , Tuve M. A.
Published: February 2005

The alterations in design of a Wilson-Blackett automatic cloud-chamber apparatus, found necessary or convenient in adapting it to photographing tracks of high-speed ions from a high-voltage tube, are briefly described. An experimental cloud-chamber, which can be oriented in any position, constructed from a six-inch diameter metallic sylphon-bellows, free from leaks and with several other advantages, is shown. A convenient type of mercury spark-lamp which makes possible the use of fine-grained positive-emulsion films is described. Designs are given for a larger sylphon-type chamber based on the satisfactory experience with the smaller chamber.
Radiation Thermopiles for Use at Liquid Air Temperatures
Authors: Cartwright C. Hawley
Published: February 2005

Based on observations of thermoelectric power and the Wiedemann-Franz ratio λ/κ, a compensated radiation thermopile has been built and operated in a vacuum at low temperatures, which shows a more than tenfold increase in sensitivity when operated at the temperature of liquid oxygen, as compared to operation at 25°C.
A Vertical, Vacuum, Split-Tube, Graphite-Resistance Furnace
Authors: Evans Robley D.
Published: February 2005

By splitting the graphite resistor tube of a vertical, evacuated, high temperature furnace, the construction is simplified, the possibility of resistor breakage is circumvented and the zone of highest temperature is brought deeper in the furnace than in the spiral or solid tube types of vertical furnace. The construction of the furnace cover permits crucibles to be put in or removed from the furnace without breaking the main vacuum seal. The melt can be observed visually, or the gases from the melt can be drawn off to other apparatus, without having to pass through the main furnace volume. The furnace reaches 2000°C on 7 kw of power input.
The Measurement of the Permeability of Porous Media for Homogeneous Fluids
Authors: Wyckoff R. D. , Botset H. G. , Muskat M. , Reed D. W.
Published: February 2005

A detailed technique is described for the measurement of the permeability of porous media, by the use of either liquids or gases. Derivations are given of the formulae by which the permeability may be computed from the laboratory measurements. In addition to defining a convenient permeability unit, it is proposed to call it the ``darcy.'' Field measurements on the effective permeability of underground sands are discussed, and the appropriate formulae are derived. These include expressions for liquid flow, gas flow, gravity flow and composite artesian and gravity flow. Correction curves are given for application when the wells do not completely penetrate the producing sands.
An Improved Balanced Circuit for Use with Electrometer Tubes
Authors: Turner Louis A. , Siegelin C. O.
Published: February 2005

A modification of Soller's balanced circuit for use of a single FP-54 tube has been found which gives improved stability of balance and the possibility of use with galvanometers of high resistance. The theory of the circuit and detailed directions for calculating, setting up, and balancing it are given.
The Equivalent Circuit of a Blocking-Layer Photo-Cell
Authors: Wood Lawrence A.
Published: February 2005

A general method of determining the equivalent circuit elements of a network containing any number and arrangement of resistances with one variable impedance element involves plotting a graph of the reactive component of the impedance against the resistive component at different frequencies. Capacitance bridge measurements at audio-frequencies with a Weston Photronic cell at different illuminations yield data for such a graph. Circles are obtained from which it is concluded that the impedance element itself is capacitative and maintains a constant phase difference of the order of magnitude of 10° between current and voltage. The impedance of the cell as a whole decreases radically with frequency. From the circles it is found that the equivalent resistance in series with the impedance element is of the order of 35 ohms and is independent of illumination and other variable factors. The equivalent resistance in parallel with the impedance element is of the order of several thousand ohms, decreases with illumination and varies from day to day. After illumination, more than ten minutes elapse before steady conditions are again attained in the dark. The impedance element itself is regarded as capacitance of the order of 0.5μf and a series resistance, each decreasing with frequency. The capacitance varies approximately inversely as the frequency raised to the 0.1 power, and the resistance inversely as the frequency raised to the 0.9 power. Fricke's equation relating the former exponent to the phase difference is found applicable. The capacitance increases and the resistance decreases with illumination. A general similarity to electrolytic polarization capacitance is noted. When an inductance coil is placed across the cell and the cell is illuminated with light of sinusoidally-varying intensity, resonance is obtained at a definite critical frequency.
A Fast and Economical Type of Photographic Oscillograph
Authors: Draper C. S. , Luck D. G. C.
Published: February 2005

The problem of securing records economically over a relatively long period of time, at moderate or high film speeds, led to the design of a new type of oscillograph. Two such instruments, one applied to the study of the Barkhausen effect and the other to the recording of processes in the internal combustion engine, are described. By using a short distance from the mirror to the film it is possible to secure oscillograph records with standard motion picture film. It is shown that the record suffers no inaccuracy by this change from the conventional type of oscillograph. At the routine film speed of 25 feet per second, as used in the engine oscillograph, the shape of the record is similar to a standard oscillograph record at a speed of 160 feet per second. The fineness of the trace can be extended almost to the limit set by the resolving power of the film itself. The errors due to the increased values of the tangent of the angle of deflection are within one percent. Provision is made for viewing the light track, although the scale is too small to make the instrument especially valuable for viewing purposes. A time scale is established on the records without use of a vibrator element.
The Use of Triode Vacuum Tube Rectifiers to Supply Constant Voltage
Authors: Richards L. A.
Published: February 2005

When triode vacuum tubes are used as rectifiers approximately constant d.c. voltage can be obtained from a rectifier-filter circuit by having changes in the a.c. line voltage control the grid bias of the triode rectifiers. By using common radio receiving tubes in circuits which are described it is found that a 10 percent change in the a.c. voltage causes from 0.1 to 0.02 percent change in the d.c. voltage output of the filter.
String Controlled Alternating-Current Source
Authors: Stauffer L. H.
Published: February 2005

This paper describes a device for generating alternating current of variable frequency (50 to 1000 cycles per sec.). It consists of a stretched steel wire, the vibrations of which are maintained by an electromagnet. Vibrations from the wire are impressed upon a carbon disk modulator of special design. Modulated current from a battery is amplified and part of it is then used to maintain the wire in vibration while the remainder is fed into an output filter. The harmonics produced are fairly weak and are suppressed with the aid of a simple filter. Advantages of the device are simplicity, continuous frequency control, and ease of calibration. Other applications of the apparatus are described.
The Limitation in Currents of Positive Alkali Ions of Homogeneous Velocities
Authors: Keck Paul , Loeb Leonard B.
Published: February 2005

In endeavoring to obtain an intense source of positive K ions for the study of the radiation potential of K ions in A, a source was developed in which an atomic beam of K atoms was projected against a Pt strip filament at 1000°C in high vacuum. The resulting positive ions were accelerated by a field and yielded 2×10−4 amp./cm2 at 330° at a potential of 340 volts, of which about 60 percent had an energy distribution of less than 25 volts. The limitation of the homogeneity of the beam lay in part in collisions with atoms in the accelerating field and doubtless can be improved. The space charge limitation of the currents precludes the achievement of greater current densities at these potentials. It is possible that the device could be utilized in the study of the radiation potentials although the recently published method of Dempster and Holzer appears more suitable. Since Li is ionized quantitatively by impact with a hot filament, the device could be utilized in conjunction with a positive ray analyzer to separate the Li isotopes at the rate of at least 0.13 mg per day. It could also be used as a 3 electrode tube for the production of oscillations.
A Small Wind Meter
Authors: Hulburt E. O.
Published: February 2005

The paper describes a small, rugged, portable, quick period wind meter for measuring the speed of wind and of gusts of wind. The instrument consists essentially of a mica vane and pointer twisting a torsion wire.
The Production of High Rotational Speeds
Authors: Beams J. W. , Pickels E. G.
Published: February 2005

Methods of spinning rotors to very high speeds by means of compressed air are discussed. A detailed description is given of the construction of apparatus to spin rotors both in gases at various pressures and in vacuum. Some uses of the apparatus and its operating characteristics are outlined.
Apparatus for the Measurement of Breakdown Voltage Between Metal Electrodes in Vacuum
Authors: Anderson H. W.
Published: February 2005

This paper describes apparatus used for the measurement of breakdown voltages between electrodes in vacuum with potentials up to the order of 500 kv. The use of a direct voltage of this magnitude required special shielding to limit electrical stresses in the lead-in bushing of the vacuum tank. The source of power was an electrostatic belt generator with a corona-leak voltage control. Voltage was measured with a xylene alcohol high resistance voltmeter. Incidental work with stand-off insulators in vacuum is described. The results of a series of breakdown measurements are shown with a curve.
Multi-Lamellar Cylindrical Magnetic Shields
Authors: Sterne T. E.
Published: February 2005

A method is described by which the shielding ratio of a system of coaxial cylinders may be rapidly computed by means of recurrence formulae. For cylinders of infinite length the method is exact and general, being applicable to the case of n coaxial cylinders, of any radial dimensions, in contact or separated by gaps, and composed of the same or of different material. The method should give reasonably correct results when applied to systems of cylinders of finite length but with closed ends. It is illustrated by numerical applications to shields with more than nineteen components.
An Interference Method for Measuring the Piezoelectric Moduli of Alpha-Quartz; The Moduli
Authors: Osterberg H. , Cookson J. W.
Published: February 2005

Straight line, thick film interference fringes are formed between the quartz surface whose normal components of displacement are being measured and an auxiliary optical flat which is supported above this surface by means of a suitable holder. It is advantageous to form these fringes between the auxiliary optical flat and a small optical flat which is attached directly to the quartz surface. With this method one can measure periodic displacements whose amplitudes are even less than a wave-length of light with an accuracy greater than 99 percent. In measuring the piezoelectric modulus d11, one Y face of a conventional rectangular X cut is rigidly held, an alternating (60 cycles/sec.) electric field applied along X, and the corresponding displacements of the other Y face measured in the above manner. As required by theory, the normal component of displacement is found to be uniform over the Y face. This permits d11 to be measured with an accuracy which is considerably greater than 99 percent. It is necessary to employ electrode arrangements which produce a uniform electric field. The modulus d14 is measured from forced extensional vibrations in specially oriented X cuts. Its measurement is found to be more difficult than that of d11. The final values of d11 and d14 are, respectively, −6.22 ±0.03×10−8 cm/e.s.u. and +2.24±0.05×10−8 cm/e.s.u. These experiments show that d11 and d14 are constant in optically and mechanically flawless α-quartz and that the variations reported by Dawson and by Fox and Fink should be attributed to their experimental error and perhaps to the quality of the quartz employed. A comparison of our values of d11 and d14 with those of Pockels shows that the measurements of these moduli by the direct and converse methods agree within the error of experiment. The presence of the strain components exy and ezx is verified by direct experiment. Their magnitude is of the order predicted by the theory. It is shown that the effect of electrostriction upon the measured values of d11 and d14 is negligible. The effect of viscosity is negligible. These measurements can be improved when better means have been devised for generating and measuring high sinusoidal voltages.
A Two-Crystal Spectrometer for X-Rays of Wave-Length 0.030<λ<0.215A
Authors: Cuykendall T. R. , Jones M. T.
Published: February 2005

A two-crystal x-ray spectrometer for use in the wave-length region 0.030<λ<0.215A is described. Transmission and reflection of the x-rays through the body of the crystal, instead of the usual reflection from the surface, is employed. An ionization chamber containing argon at 80 atmospheres, and an FP-54 electrometer tube system is used to measure the intensity of the reflected radiation. A source of short wave-length x-rays, consisting of two specially designed induction coils and a cascade Coolidge tube, is described. Rocking curves in the (1, −1) position at 50 X.U., the K limits of lead and of uranium, and the Kα and Kβ-lines of tungsten were observed for the purpose of calibrating the spectrometer. The resolving power of the instrument with the present crystals is discussed.
Superiority of a Knudsen Type Vacuum Gauge for Large Metal Systems with Organic Vapor Pumps; Its Design and Operation
Authors: DuMond Jesse W. M. , Pickels W. M.
Published: February 2005

The McLeod, Pirani, Knudsen and ionization gauges have been studied as to their suitability in the operation of large metal vacuum systems with organic vapor pumps now coming into extensive use in modern physics. Advantages and disadvantages of each type based on our experience are critically discussed. The superiority of a gauge on the Knudsen principle for this work is stressed and we present a new design and a simpler mode of operation of such a gauge together with a full discussion of its construction, calibration and characteristics.
Resolving Power of the Two-Crystal X-Ray Spectrometer
Authors: Parratt Lyman G.
Published: February 2005

The physical meaning of resolving power when the shape of the involved diffraction pattern is unknown is experimentally studied with the double crystal x-ray spectrometer. Our concepts of resolving power have not been extended in effect beyond the formal numerical definition and now there is need for knowing more completely the perturbations introduced by the dλ interval. Sixteen different pairs of crystals, quartz and calcite, cleavage and etched surfaces, were used in measuring the widths and shapes of the Kα doublet lines of Mo, Cu and Ti and the Lα1 line of Ag with the spectrometer in various parallel and antiparallel positions. The crystal diffraction patterns are evidently asymmetrical, in qualitative agreement with theory; and the asymmetry evidently varies with different pairs of crystals as well as with wave-length. The (1, −1) width is invalidated as an adequate criterion of resolving power. New criteria for ``spectrometric'' perfection of calcite crystals are proposed and an equation is given for correcting observed x-ray line widths for the effects of ``spectrometrically'' perfect crystals.
A New Method of Making Extremely Thin Films
Authors: Lark-Horovitz K. , Howe J. D. , Purcell E. M.
Published: February 2005

A method for making extremely thin films has been developed for general use. A hole or slit in a metal plate is filled with a volatile solid and the surface is polished flat. This plate is clamped to the lower end of a liquid air container which extends into a high vacuum chamber. The material to be deposited is evaporated and covers slit and plate with a continuous film of desired thickness. The slit is then placed into the apparatus for the investigation of the film, and on evacuation the volatile material evaporates leaving the thin film supported on the slit. Camphor and naphthalene have been used as volatile material. For investigations in which residues of organic substances have to be avoided ammonium chloride, which may be driven off in vacuum at about 220°C, can be used to support the film.
Construction and Behavior of a High Voltage Cylindrical Condenser
Authors: Bundy F. P. , Pool M. L.
Published: February 2005

Cylinders of lumite glass 35 inches long by 10¼-inch diameter (such as are used on gasoline filling-station pumps) were used for dielectrics, and 0.005-inch aluminum foil for plates. A 7-inch glass margin was left at the ends of the cylinders. Each condenser had a capacity of 0.012 microfarad and would withstand steady voltages of over 100 kilovolts without ``flashing over.'' Sets of rings of 516−inch copper tubing were made to fit the cylinders at the edges of the plates, both inside and out. The rings provided a ``curled'' or ``rounded'' edge, in place of the rather sharp edge of the foil itself. The effect upon the ``edge corona'' and ``flash-over voltage,'' due to various-width bands of aluminum paint on the glass surface adjacent to the metal-plate edges, was tried, with and without the above-mentioned rings, in disruptive discharge and steady-voltage tests. The results showed that the highest voltages could be obtained, without break-over occurring, when the glass margins were chemically clean. It was also found that the best type of plate-edge construction was either the plain aluminum-foil edges without paint, or the curled edges (i.e., with copper rings) with a ¼-inch band of paint.
Note on a Greinacher Hydraulic Counter for Quanta and Ionizing Particles
Authors: Summers Rembrandt D.
Published: February 2005

A modified form of Greinacher counter is described with an auxiliary ionization gap to extend the frequency range. This sensitive detector of faint radiation and ionizing particles can be easily and quickly assembled from common and inexpensive parts.
A High Intensity Discharge Tube
Authors: Stevens Daniel S.
Published: February 2005

A high intensity discharge tube is constructed by placing a small constriction in a direct-current arc. The direct current is supplied by mercury vapor rectifiers. The tube has been operated with the rare gases, oxygen, hydrogen and nitrogen. With hydrogen the ultraviolet continuous spectrum is very strong and this tube should be a good source for absorption spectra in that region. The use of a wedge lens is also described.
A Direct-Reading Frequency Meter Suitable for High Speed Recording
Authors: Hunt Frederick V.
Published: February 2005

A modified two-tube thyratron inverter is employed to deliver an invariant current pulse to an indicating instrument each time the polarity of the input signal reverses. The average current in the indicator is strictly proportional to the frequency of the input signal below 7000 cycles and approximately so for higher frequencies. The current may be varied to permit a standard current instrument to be used as a direct-reading frequency indicator. The readings of the instrument are independent of the amplitude or wave form of the input signal over a wide range. When the frequency of the input signal is not constant either an accurate indication of the average frequency can be obtained or the output circuit of the instrument can be modified to permit the frequency to be recorded as a function of time. The problem of recording the frequency variations occurring in speech or singing is discussed and other applications of the instrument are suggested.
A Simplified Apparatus for X-Ray Quantitative Chemical Analysis with the Cathode-Ray Tube
Authors: Jesse William P.
Published: February 2005

A compact oil-immersed apparatus is here described where cathode rays from a cathode-ray tube strike the substance to be analyzed and excite characteristic x-rays. The measurement of these allows a quantitative chemical analysis of the substance to be made. The apparatus is a simplification of apparatus already in use in this Laboratory. Data are given showing the accuracy and sensitivity of the analysis method.
A Sixty Cycle Wave Recorder
Authors: Westendorp W. F.
Published: February 2005

A semi-automatic wave recorder has been developed for small alternating voltages in synchronism with the three phase power supply. The device has an input impedance of more than 250,000 ohms and records directly on metric paper so that 1 cm = 1 volt and 18 cm = 1 cycle = 360°. About one minute of the operator's time is required to plot a complete curve.
The Use of the Rotary Voltmeter for Measurements up to 830 Kilovolts
Authors: Henderson Joseph E. , Goss Wilbur H. , Rose John E.
Published: February 2005

The rotary voltmeter is shown to be a practical instrument for the measurement of both voltages and wave forms up to 830 kilovolts peak. A comparison of voltages so measured with the sphere gap shows that a downward revision of the A. I. E. E. standards is necessary.
A Two-Stage Oil Diffusion Pump
Authors: Henderson Joseph E.
Published: February 2005

A two-stage oil diffusion pump built of glass is described which makes possible the utilization of the advantages of oil without requiring the use of an unusually good coarse vacuum. The novelty of the pump resides in the first stage which is so designed that it cannot clog even with the small clearances needed to work against high pressures.
Precision Lattice Constants from X-Ray Powder Photographs
Authors: Cohen M. U.
Published: February 2005

A very general method is given for the calculation of lattice constants from powder photographs in which there is taken into account the various systematic errors inevitable in such photographs, including radius errors, film shrinkage, absorption, eccentricity and finite slit height. While the solution of the data is made by least squares, it is not at all laborious and is much simpler than the various methods, both analytical and graphical, which have previously been proposed. Examples are given of cubic, hexagonal and orthorhombic structures solved in this way using data from Debye and focusing cameras, extension to other structures and cameras being made evident. In effect, powder cameras become absolute instruments, independent of calibrating substances, and dependent only on the value of the x-ray wavelength.
A Bilateral Slit Mechanism
Authors: Barnes R. Bowling , Brattain R. Robert
Published: February 2005

A bilateral slit mechanism is described which is accurate in its performance and simple enough to be constructed in any laboratory workshop.
Direct-Current Amplifier Circuits for Use with the Electrometer Tube
Authors: Penick D. B.
Published: February 2005

A number of balanced, single-tube, direct-current amplifier circuits are compared, which are applicable to the four-element, low grid-current vacuum tube. The balance equations are stated for the most generally useful circuit, and magnitudes of the tube characteristics involved are given for the Western Electric No. D-96475 Tube. Experimentally determined values of circuit constants observed under balance conditions are also given. The stability of the circuit is discussed, and a convenient procedure for obtaining a balance by experimental methods is suggested.
A Linear Photoelectric Densitometer
Authors: Miller Carl W.
Published: February 2005

A photoelectric densitometer is described which makes use of the remote cut-off characteristic of a 58 type thermionic tube to give a meter reading which is very nearly proportional to density. Commercial alternating current is utilized throughout, resulting in a convenient and portable type of instrument. A method is described by which it can also be used to measure the blackness of opaque objects.
Apparatus for the Determination of Minute Quantities of Radium, Radon and Thoron in Solids, Liquids and Gases
Authors: Evans Robley D.
Published: February 2005

The radium content of ordinary materials is determined by removing and measuring the radon which is in equilibrium with the radium. I. Generalization of the direct fusion furnace method now permits the rapid and complete deemanation of any solid by direct boiling at 2000°C. II. Improved boiling apparatus for the removal of radon from liquids avoids loss of traces of radon by absorption. III. Gaseous samples, at atmospheric pressure, may be examined directly for radon. IV. Double ionization chambers, coupled to a high sensitivity string electrometer, permit observations on very feeble sources. Statistical fluctuations in the emission of contamination alpha-rays from the ionization chamber walls impose a natural observational limit of 7.2×10−14(n)−½ curies of radon, when the ionization currents are observed for n hours. V. Photographic recording of the ionization current, with hourly automatic recalibration of the electrometer at three arbitrary potentials, makes possible long runs and higher precision, particularly for weak sources. VI. Induction, null-induction and ionization methods for the measurement of the electrostatic capacity of ionization chamber systems are described. VII. Caution is given against a spurious ionization, of unknown origin, occasionally observed in connection with radon tests. VIII. The flow method for the measurement of thoron is shown to be more applicable to liquid samples than to solids. Under normal operating conditions the emanating power of liquid samples is about 0.6. IX. Mean values of the radium content of certain classes of rocks, sea waters and organisms are given.
A High Speed Oil Diffusion Pump
Authors: Edwards Hiram W.
Published: February 2005

The peculiarities of design in this pump are, the use of streamlines in regions of high pressure and the introduction of small angle conical surfaces for baffles in the regions of lower pressures. The conical baffles are particularly effective in preventing oil vapor from entering the chamber to be evacuated and at the same time in offering a minimum of impedance to the flow of gas through the pump. A three-inch pump with this design and operating on a Western mineral oil especially prepared for it in this laboratory has shown a pumping speed in excess of 50 liters per second at a pressure of 1.0×10−4 mm.
A Peak Voltmeter
Authors: Ruiz John J.
Published: February 2005

A circuit is described for measuring peak voltages with a gas-filled grid-controlled tube. The principle of operation is similar to that of the well-known Heising voltmeter.
Duplex Cathode-Ray Oscillograph
Authors: Garceau Lovett
Published: February 2005

A method is described for simultaneous visualization or photography of two separate phenomena, either transient or repetitive in nature, on the screen of a single cathode-ray oscillograph.
Temperatures of Continuously Operated Mobile X-Ray Focal Spots
Authors: DuMond Jesse W. M. , Watson Bernard B. , Hicks Bruce
Published: February 2005

We use the adjective ``mobile'' to describe a focal spot in an x-ray tube which moves cyclically in a closed path relative to the target surface on which it is generated quite without reference to whether the spot be fixed or in motion with respect to the tube. Alex Müller and also A. Bouwers have made calculations of the thermal effects in such spots energized for very short fractions of one cycle of motion. This paper treats the case where the focal spot is energized continuously so that a ``steady'' state of thermal oscillation is set up. The solutions obtained refer only to conditions after this steady state of oscillation is reached. Only the ideal case of a spot of uniform intensity with sharp boundaries is treated. For simplicity the flow of heat from front target surface to cooling water is assumed one dimensional and normal to the front surface over an everywhere uniform thickness d. Curves are plotted showing the ratio of temperature rise in moving spots to that in fixed spots of the same size as a function of r the size of the spot relative to the length of path it describes and of θ a variable depending on the speed of rotation, the thickness d and the thermal constants of the target material. Curves of the ratio of permissible energy input for moving and fixed spots, respectively, as a function of the aforementioned variables are also shown. The paper gives a solution reduced to figures and curves of the heat flow equation for certain boundary conditions which to the author's knowledge has never before been obtained and therefore has some interest beyond its immediate application to x-ray tubes. Certain mathematical difficulties of practical interest are also overcome in a way which may be helpful in other problems of similar nature. For the reader uninterested in mathematics the results are independently discussed in a separate section. Approximate methods are given for applying the results of the paper to targets consisting of two materials such as tungsten and copper.
Alternating-Current Operated Beat-Frequency Oscillator
Authors: Harnwell G. P. , Van Voorhis S. N.
Published: February 2005

An a.c. operated beat-frequency oscillator constructed from ordinary radio parts is described. The circuit design gives good wave form, and excellent stability of frequency with changing line voltage.
Current-Voltage Relations in Blocking-Layer Photo-Cells
Authors: Wood Lawrence A.
Published: February 2005

Observations have been made of current (0.1 to 10,000 μa) in a Weston Photronic blocking-layer photo-cell, as a function of illumination (1 to 100,000 lux) and of potential difference across the cell. The use of a graph of current against voltage is discussed, as well as the conditions for maximum external power (largest observed value about 1 milliwatt). The leakage current through the blocking layer is calculated and from it the d.c. conductance in the low resistance direction is obtained. This is found to consist of a constant term of the order of 80 micromhos, as well as terms proportional to the 0.8 power of the leakage current and the 0.4 power of the illumination. A fourth term is ascribed to the effect of the potential across the blocking layer in preventing the passage of low velocity photoelectrons across the layer. With maximum illumination a conductance as high as 9000 micromhos is obtained. This rises to 30,000 micromhos or more with the largest leakage currents. A Westinghouse Photox cell was found to possess an internal conductance which changes very little with current, and which contains a term varying as the 0.4 power of the illumination. Comparison of the two cells indicates that nonlinearity of the current-voltage characteristic and rectification (almost absent and becoming reversed in the Photox cell) are not essentials in blocking-layer photo-cells. The open circuit voltages of both cells are found to be nearly proportional to the illumination for voltages less than 5 mv and to be proportional to the logarithm of the illumination for voltages greater than 50 mv.
The Cryogenic Laboratory of the California Institute of Technology. Part I
Authors: Goetz Alexander
Published: February 2005

Of a description of the Cryogenic Laboratory this paper is the first part containing the general lay-out, the details of the equipment for the liquefaction of hydrogen including a method of purifying hydrogen and a description of the Simon liquefier and the vacuum system. The capacity of the hydrogen unit is 4.5±0.5 liters per hour; 1.3±0.1, liters liquid air are needed per liter liquid hydrogen. The plant can be run permanently by one man.