W. W. Hansen

A Linear Electron Accelerator

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.

The Theory of Disk‐Loaded Wave Guides

The properties of circular wave guides loaded with apertured disks are discussed both qualitatively and quantitatively. Formulae and curves are given for various quantities including the wave and group velocities, the attenuation, and the power flow.

On the Resonant Frequency of Closed Concentric Lines

A new and more exact method of calculating the resonant frequency of closed concentric line resonators of the type shown in Fig. 1 is developed. The method becomes more accurate as the length of the line becomes small by comparison with a quarter wave‐length.

On Resonators Suitable for Klystron Oscillators

Various resonators, of the hohlraum type, suitable for driving by the klystron method, are described and their leading properties computed. Various mathematical techniques are used, including the application, for the first time in this field, of Stevensons method of determining a lower bound for the frequency.

On the Measurement of Cavity Impedance

A method of measuring cavity impedance is described.A method of measuring cavity impedance is described.

Transformations Useful in Certain Antenna Calculations

Transformation formulas are derived which greatly simplify computations relative to an antenna above a plane earth when the antenna is of a form easily specifiable in polar coordinates but not in cylindricals.

Disk‐Loaded Wave Guides

Dimensions of disk‐loaded wave guide suitable for use in a linear electron accelerator are calculated with high accuracy using Schwingers method. A qualitative explanation of the method is given.

On the General Theory of Electrometer Design

It is shown that Brownian motion sets a lower limit on the smallest charge detectable. This limit is approximately (kTC)12 with k Boltzmanns constant, T the temperature, and C the capacity of the system in centimeters. A discussion of the difficulties of reaching this limit with a vacuum tube electrometer is given with particular emphasis on the problem of shielding in which connection several suggestions are made. The ordinary electrometer is treated in much greater detail. A general theory of all electrometers is developed and it is shown that this theory together with various practical desiderata virtually dictate the essential features of the design of an electrometer. An electrometer of the design proposed will reach the limiting useful sensitivity; the quarter period when at this sensitivity is (πδθ/2)(I/2kT)12 where δθ is the least detectable change in angle of the suspended system and I is the moment of inertia. Without resorting to extreme construction this time can be made as short as fifteen s...

THE MEASUREMENT OF X‐RAY INTENSITIES AS FUNCTIONS OF VOLTAGE, UP TO 180 KV

The measurement of intensity of an x‐ray line presents two sets of technical requirements, quite different, according to whether the intensity is to be compared with those of other lines at the same voltage or of the same line at other voltages. The latter set of requirements is discussed here, with a description of a tube designed to meet them. This tube is built of steel and Pyrex, with several sections of each, permitting a variety of high‐voltage connections for special purposes related to possible sources of error. To prevent the deposition of carbon and tungsten on the target, the pumping speed is made very high, especially for grease vapors. The detection of carbon, and rough measurement of its retardation of the cathode rays, is accomplished by one of the special changes of connections. To minimize the effects of such positive ions as may be present in spite of the high pumping speed, the tube has a special form of cathode. And to measure the possible amount of error due to such ions, another of t...

Electrostatic Focusing at Relativistic Speeds

Power series are derived with which, given data on the electric field, the focal properties of some common electron lenses can be quickly computed even when the speed of the electrons approaches that of light. The expansion is in powers of the ratio of the P.D. across the lens to the sum of the P.D.s between its electrodes and the cathode (for electrons) or anode (for positive ions), squares of this ratio being neglected in comparison with unity. As an example the focusing properties of two cylinders almost in contact are calculated.