Charles Susskind

Statistical Theory of Electron Transport in the Smooth‐Bore Magnetron

Electron transport across the magnetic field in the cutoff smooth‐bore magnetron is described on the basis of random fluctuations in the fields. The theory is formulated in terms of the slipping‐stream instability, so that a definite mechanism behind the fluctuations in the fields is established. The transport equation appropriate to the analysis is shown to be the diffusion equation; the diffusion tensor follows from the characteristics of the slipping‐stream instability. Application of the theory is made to find the cutoff characteristics of the smooth‐bore magnetron. Expressions for the electric field, the space‐charge distribution, the anode current, and the circulating current are obtained; the results are compared with available experimental results. The agreement between theoretical and experimental results is good, particularly for the anode current. The new theory thus provides, for the first time, an acceptable theoretical explanation of the cutoff characteristics of the smooth‐bore magnetron.

Infrared and microwave communication by moths

Analytical and experimental studies seeking to confirm or refute the hypothesis that moths communicate with each other by coherent electromagnetic waves have been under way at Berkeley for several years. This article is the first report from the bioengineering group conducting these studies.

Electronics and the Blind

Publisher Summary This chapter describes the role of electronics in development of technological aids for the blind. Guidance devices may be conveniently classified according to their mode of operation. Most of the early devices were of the echo type. A beam of sound or electromagnetic energy is transmitted, and its echo from an obstacle is received and modified to provide information to the user. Specular reflection constitutes an important and sometimes insurmountable impasse to proper functioning. Along with error-free detection of obstacles it is equally important that the false-alarm rate of the instrument be kept as low as possible. The development of the curb detector led to the proposal that the user should receive the signal indicating a down-step, up-step, or hole at least one step in advance to enable him to alter course in time. In the pulse system the variable pulse repetition rate is adjustable by the user. Sufficient time is allowed between pulses for echoes to be detected without ambiguity. The received echo is heterodyned with an oscillator at a frequency lower by 4 kc to produce audible pulses. Some devices have been developed specifically as tactile stimulators for sensory-aid devices. The development of electronic devices to aid the blind in various industrial tasks is also elaborated.

Electron Guns and Focusing for High-Density Electron Beams

Publisher Summary The incorporation of a high-density electron beam in an electron tube poses two problems: the design of an electron gun capable of providing a sufficient number of electrons, and the selection of an efficient method of holding the resulting electron beam together in the face of space-charge forces and other effects leading to divergence. This chapter describes the principal methods by which these two problems can be solved and provides a critical review of the various suggestions that have been made to improve these methods or to replace them by new techniques. It describes the Pierce method and evaluates several methods of arriving at a Pierce gun by alternate design procedures, which are thought to be more systematic than that proposed originally. Other interesting configurations that differ from Pierces are evaluated in the chapter. To describe the methods of counteracting beam spreading three schemes are presented in the chapter: (1).the magnetic field surrounds the entire tube, so that the cathode is immersed in the field; (2). the magnetic field is excluded from the cathode by a ferromagnetic shield; and (3). the magnetic focusing field is periodic in nature, being produced by a series of magnetic lenses of alternating polarities.

Processing and Stereophonic Presentation of Physiological Signals

Since the inception of electroencephalography (EEG), several devices have been built that make brain waves audible; they are known as electroencephalophones (EEP). None has so far taken advantage of the human binaural hearing capability. The system described here presents an effective stereophonic display of four channels of EEG, each from one quadrant of the skull. The signals from the two front quadrants are represented by a single tone whose pitch varies about a center frequency of 1250 Hz and which appears to move laterally in auditory space. The signals from the two occipital quadrants are similarly represented about center frequency of 700 Hz, so that they are readily distinguished from frontal activity. All channels are played through a single pair of headphones. The left headphone represents the combined activity of the two left-hand quadrants; the right headphone, of the two right-hand quadrants. The scheme may be used to supplement conventional graphic EEG records; under special conditions (e. g., routine monitoring, sleep research, training,) it may replace them altogether. Moreover, it may be adapted to vector electrocardiography (EKG) and even to the presentation of signals other than physiological, for instance in seismography.

Dual energy CT scanning for analysis of brain damage due to X-irradiation

Therapeutic irradiation is commonly used in the treatment of malignant brain tumors and has the potential to cause severe injury to normal tissues adjacent to a lesion. Computed tomography (CT) can be used not only to visualize tissue damage but to monitor the development of a lesion using advanced quantitative CT techniques. We have used a postprocessing dual energy CT method to quantify changes in tissue composition following large single doses of X-rays to the normal canine brain. The results suggest that these techniques will provide more information about the character of a lesion than is obtainable from conventional imaging procedures.

Stiffness of Electron Beams

A new parameter for use with electron-beam devices is defined as a quantitative measure of the extent to which the beam withstands the effects of transverse forces. The new figure of merit can be used to compare the effectiveness of various methods of constraining the beam, as illustrated by application to the cases of space-chargebalanced flow (including Brillouin flow and immersed flow), periodic focusing, Harris flow, E- and C-type flow, and M- type flow. Stiffness is defined as the rate of change of force (in the direction transverse to that of beam travel) that acts to restore a displaced electron to its equilibrium trajectery in a laminar beam. (auth)

Ferdinand Braun: Forgotten Forefather

Publisher Summary This chapter provides a biographical sketch of Karl Ferdinand Braun born on June 6, 1850 in Fulda. He earned the doctorate cum laude in 1872 with a dissertation in acoustics and had begun to look for a job as a school teacher when his thesis advisor engaged Braun as his assistant. But the assistantship turned out to be a blind alley. After two years, Braun had enough and went back to his original plan to become a school teacher. He got a job at the well-known Thomas-Gymnasium in Leipzig, center of the German publishing industry and stayed there for three years. It was during these years that he published his only book; an amusing set of mathematical and scientific puzzles, experiments, and other entertainments for young people. It was during these same years, that he finally found time to write some experiments he must have initiated while he was still at Wurzburg.

Proposed System of Periodic Reports to Government Agencies

A new scheme is proposed for simplifying the preparation, submission, and distribution of quarterly and other periodic reports required under most technical and scientific government contracts. Each organization would submit a single report each quarter covering work under all contracts in a given field, with suitable acknowledgments of the support of each sponsor, standardized distribution, and time-saving elimination of contradictory reporting practices.