Cavity Section Research Articles

A Racetrack Microtron RF System

The rf system for the National Bureau of Standards (NBS)/Los Alamos cw racetrack microtron is described. The low-power portion consists of five 75-W amplifiers that drive two input ports in each of two chopper deflection cavities and one port in the prebuncher cavity. A single 500-kW klystron drives four separate 2380-MHz cavity sections: the two main accelerator sections, a capture section, and a preaccelerator section. The phases and amplitudes in all cavities are controlled by electronic or electromechanical controls. The 1-MW klystron power supply and crowbar system were purchased as a unit; several modifications are described that improve power-supply performance. The entire rf system has been tested and shipped to the NBS, and the chopper-buncher system has been operated with beam at the NBS.

Coupled-cavity semiconductor lasers under current modulation: Small-signal analysis

The modulation characteristics such as the power response and the chirp (dynamic line broadening) of single-frequency coupled-cavity semiconductor lasers are analyzed theoretically. The model is based on the small-signal analysis of a set of generalized rate equations and neglects the lateral variations of the optical field and the carrier density in the two cavity sections. When the controller section is biased below threshold in a three-terminal device the modulation response is not significantly affected by the intercavity coupling. By contrast, new features arise when both sections are biased above threshold. It is found that the chirp can be significantly reduced by a proper combination of the bias levels and the modulation splitting between the two sections. The chirp reduction also depends on the strength of the intercavity coupling and its phase, and the best performance is achieved for the case of in-phase coupling. The calculated results are in qualitative agreement with the reported experimental data and are useful as a guide to optimize the performance of a coupled-cavity device.

Mode conversion in a Gyrotron at a waveguide-taper junction

The output power levels of Gyrotron II are very much higher than those predicted when one assumes that a single waveguide mode exists throughout the cavity and output section. In this paper we demonstrate the importance of mode conversion at the point where the uniform waveguide meets the first down-taper.

Distribution of guaiacol peroxidase in human endometrium and endocervical epithelium during the menstrual cycle.

Guaiacol peroxidase (G-Px) was measured in extracts from five sections along the length of human uterus on different days of the menstrual cycle or after menopause. The lower uterine-endocervical region had a significantly higher G-Px content (expressed as enzyme units per g wet tissue) than the other sections, although in postmenopausal patients the G-Px activity was uniformly low in all sections of the uterine cavity. We observed no significant changes in G-Px levels during the menstrual cycle, except, possibly, a decrease around ovulation, which precluded a positive correlation between plasma estrogen levels and uterine G-Px content; such estrogen dependence of G-Px has been previously shown in the rat. In vitro, G-Px was inhibited by estriol and 17 beta-estradiol, marginally inhibited by estrone, and most notably inhibited by the catecholestrogens tested (2-hydroxy-17 beta-estradiol, 2-hydroxy-estriol, and 2-hydroxy-estrone), which were equipotent inhibitors; LH and FSH, progesterone, or cortisol had no effect on G-Px activity. We hypothesize that catecholestrogens are natural substrates and regulations of G-Px activity in the human uterus.

Phonograph tone arm system

A device improves a tone arm of a phonograph (33) wherein the "pick-up", including the style, is supported on a low friction support, has a bearing air (25) which provides a motion substantially without friction of the tone arm (33) and the "pickup" (34) has both horizontal linear displacement and vertical pivot to ensure adequate style pressure. The tone arm of the support system comprises a support member (25) having a top surface (29) having a circular cavity or cylinder section and a float member (30) having a concave lower surface or convex corresponding juxtaposed . A recess (31) in the bottom surface of the floating member form a compression chamber in which air is supplied from one or more openings (28) provided in the support member. The length of the compression chamber is such that the feed openings are still below the limits of the compression chamber during the entire crossing in the style of a disc is playing to reduce the required minimum air quantity and give maximum support uniformity in the floating body. Other embodiments can play either the top side or the underside of a disc.

On the formulation of the problem of the motion of a body in water

The selection of solutions describing steady irrotational flow of an ideal incompressible fluid over bodies is considered. The selection is based on restrictions that follow from the physical properties of a real fluid and from the presence of a boundary layer on the body. In particular, for any body one can specify a minimal Euler number below which flow without cavitation becomes physically impossible. In the limiting case of an Euler number equal to zero, only the Kirchhoff scheme is physical admissible, and the cavity section tends to a circle. An equation is derived for the limiting shapes of cavities at small cavitation numbers, and a comparison is made with known results.

Photographic study of melting about an embedded horizontal heating cylinder

INTRODUCTION THE OBJECTIVE of this note is to provide direct visual information to supplement and extend the results of [l] relevant to the role of natural convection in the melting of solids. In [l], experiments were described in which a horizontal heating cylinder was embedded in a solid at its fusion temperature. By energizing the heater with a constant power input, a steadily growing melt region surrounding the cylinder was created. The heating cylinder was instrumented to provide information about the surface heat-transfer coefficient, and a grid of 92 thermocouples was deployed throughout the phase change medium to detect the passage of the solid-liq~d interface. The experiments were performed with a eutectic mixture of sodium hydroxide and sodium nitrate [fusion temperature u 244°C (471”F)l. The experiments demonstrated that natural convection was the dominant mode of heat transfer. One of the evidences of this dominance was the shapes of the melt region. These shapes were inferred from temperature measurem~ts in the phase change medium. Owing to mechanicat constraints, it was not possible to make detailed temperature measurements below and at the sides of the cylinder, so that the shapes presented in [l] were confined to the region above the cylinder. In the present investigation, photographic evidence of actual meh layer shapes was obtained to corroborate those inferred in [l]. The photographs show the melt Iayer both below and above the cylinder, thereby extending the results of [l]. Another extension was made in connection with the initial state of the solid at the onset of melting. Whereas in [I] all of the experiments were concerned with a solid at its fusion temperature, the present experiments encompassed both that condition and an initially subcooled condition (i.e. initial temperature of the solid lower than the fusion temperature). The general approach used in the investigation was to embed a horizontal heating cylinder in a solid phasechange material and to create a growing melt region about the cylinder by a steady input of heat. At a preselected time, the heating was discontinued and the liquid was extracted from the melt region by means of suction and gravity. The unmetted solid was allowed to cool to room temperature and then was removed from the test apparatus and cut along a vertical plane, thereby revealing the cross section of the melt cavity. To obtain a clear photographic record of the shape of the cavity, it was filled with a dark sand. The experiments were performed using the same eutectic salt as in [l J.

Reflection of elastic waves by a cylindrical cavity in an absorptive medium

The analytical formulation for the total scattering cross section of a cylindrical cavity in an elastic medium is given for the case of inclusion of compressional and shear wave attenuations. Examples are computed of relatively small attenuations exemplified by the material polymethacrylate and relatively large attenuations exemplified by polyethylene. The inclusion of wave attenuations known to exist in these materials cause the scattering cross section to diminish significantly for wave-number cylindrical-cavity-radius product up to 10.

RF System for the PEP Storage Ring

The main parameters of the rf system for the PEP storage ring are given. A total of 6 MW will be provided by twelve klystrons, each capable of delivering 500 kW of continuous rf power. Each klystron feeds two accelerating cavity sections, each 2.1 meters in length. The general layout is shown. The klystrons are housed in shelters above ground. The wave guides run through vertical penetrations to connect the klystrons to the accelerating cavities in the tunnel. The shelters are placed at three symmetrical regions around the ring. At each of regions 4, 8, and 12 there will be four klystrons and their eight cavities with the eight cavities all being grouped together in the long straight section on one side of an interaction region. The klystron power supplies are on pads outside the shelters. They are unregulated but their voltage may be slowly varied over a 40 percent range by means of variable voltage transformers in the 12 kV input line to each power supply. The output of each power supply passes into the shelter to a high voltage cabinet which contains filter capacitors, crowbars, interlock circuits, and control and metering circuits.

Glacier Sliding Down an Inclined Wavy Bed With Friction

The effects of frictional tangential traction combined with regelation on the basal sliding of a temperate glacier down an inclined wavy bed are examined. Two friction models are treated. First, a Coulomb law model having the assumptions that sliding occurs everywhere and that the tangential traction is proportional to the normal pressure. Secondly, a velocity power law in which the tangential traction is proportional to a power of the slip velocity. The ice motion is approximated by steady slow Newtonian flow and the bed undulation about a mean bed-line has a maximum slope ∊ ≪I. Flow solutions are constructed as perturbations (in powers off ∈) of the plane laminar flow corresponding to non-slip on the mean bed-line assuming that the ice remains everywhere in contact with the bed; that is, no cavitation takes place. If the normal traction is predicted to be tensile over part of the bed, implying that cavitation has occurred, then a new solution is needed in which the ice base over cavities is traction-free. Since the cavity sections and profile of the free ice base are then part of the overall solution, an intricate mixed boundary-value problem is set up for the flow and the present analysis is inadequate.For a sinusoidal bed the perfect-slip (zero tangential traction) solution predicts compressive normal traction everywhere on the bed provided that the mean bed-line inclination α (to the horizontal) is less than a critical value αe which is of order ε. For greater values of α including a range of order ∊, the normal traction is tensile on some parts of the bed, and a solution with cavitation is needed. If the tensile sections are relatively small it is expected that the resulting cavitation will not change the overall solution significantly. However, the Coulomb friction solution has extensive zones of tensile traction for all values of α, so that extensive cavitation would occur. In contrast, the velocity-power friction solution has compressive traction everywhere on the bed for α ⩽αe=0(I) provided that the ice depth is not too large, and also for deep glaciers for α ⩽αe=O∊ Furthermore, the predicted basal sliding velocity varies much less with the length scale of the bed undulation than in the perfect-slip solution, and is smaller.

Glacier Sliding Down an Inclined Wavy Bed With Friction

The effects of frictional tangential traction combined with regelation on the basal sliding of a temperate glacier down an inclined wavy bed are examined. Two friction models are treated. First, a Coulomb law model having the assumptions that sliding occurs everywhere and that the tangential traction is proportional to the normal pressure. Secondly, a velocity power law in which the tangential traction is proportional to a power of the slip velocity. The ice motion is approximated by steady slow Newtonian flow and the bed undulation about a mean bed-line has a maximum slope ∊ ≪I. Flow solutions are constructed as perturbations (in powers off ∈) of the plane laminar flow corresponding to non-slip on the mean bed-line assuming that the ice remains everywhere in contact with the bed; that is, no cavitation takes place. If the normal traction is predicted to be tensile over part of the bed, implying that cavitation has occurred, then a new solution is needed in which the ice base over cavities is traction-free. Since the cavity sections and profile of the free ice base are then part of the overall solution, an intricate mixed boundary-value problem is set up for the flow and the present analysis is inadequate.For a sinusoidal bed the perfect-slip (zero tangential traction) solution predicts compressive normal traction everywhere on the bed provided that the mean bed-line inclination α (to the horizontal) is less than a critical value αewhich is of order ε. For greater values of α including a range of order ∊, the normal traction is tensile on some parts of the bed, and a solution with cavitation is needed. If the tensile sections are relatively small it is expected that the resulting cavitation will not change the overall solution significantly. However, the Coulomb friction solution has extensive zones of tensile traction for all values of α, so that extensive cavitation would occur. In contrast, the velocity-power friction solution has compressive traction everywhere on the bed for α ⩽αe=0(I) provided that the ice depth is not too large, and also for deep glaciers forα ⩽αe=O∊ Furthermore, the predicted basal sliding velocity varies much less with the length scale of the bed undulation than in the perfect-slip solution, and is smaller.

Status of the Cern-Karlsruhe Superconducting RF Particle Separator

The present status of the rf separator is given. Measurements of single cavity sections and of two joined sections are reported. The problem of storing heat treated sections until final assembly has been investigated. Flooding a cavity at room temperature with nitrogen deteriorates its performance, after the cavity was once excited to a peak electric field of 30 MV/m, corresponding to a peak magnetic field of 850 G and a deflecting field of 5.5 MV/m. This effect is assumed to be due to a sensibilization of the surface oxides by field emission electrons. The effect is not observed after a electric field of up to 15 MV/m and it also does not appear when the cavity is flooded with argon.

Numerical Calculation of the Arc-Driven Supersonic Laser Operating in the Gas-Dynamic Mode

Numerical results derived from a theoretical model for the nozzle and cavity sections of a CO2–N2–H2O gas-dynamic laser are compared with the output of an arc-driven supersonic laser operating in the gas-dynamic mode at about 10% CO2 and H2O concentrations ranging from 0.7 to 7%.

Numerical simulation of injection mold filling

AbstractThis paper illustrates a numerical simulation of polymer flow as applied to the injection molding fill process. The simulation model considers heat conduction and viscous heat generation along with the temperature dependence of the flow parameters to predict fill lengths and fill times of thin constant crossection cavities. This simulation is designed for molding situations where fill is difficult, such as thin cavity sections, long flow length requirements, or difficult‐to‐process materials. The simulation sensitivity is explored by performing experimental molding trials with two different cavity thicknesses. The thinner cavity illustrated a short shot in all cases with the thick cavity completely filling. The simulation accurately distinguishes between the short shot and fill conditions, although significant error is noted for the length prediction of the short shot and the time‐to‐fill of the full shot condition.

S-band traveling-wave parametric amplifier using a filter circuit

An operating S-band traveling-wave parametric amplifier is described. The amplifier signal-idler circuit consists of four rectangular cavities centrally loaded by variable capacitance diodes. The cavities are inductively coupled through irises which may be exchanged to vary the size and characteristics of the passband. The pump, at C-band, is supported by a second circuit capacitively coupled to each of the signal cavities. Stable gains of greater than 20 db have been obtained by incorporating non-reciprocal loss ferrite elements in the irises between cavities. Gains of 10 db have been achieved over 10% bandwidth and more gain over wider passbands can be obtained by simply adding more cavity sections. The critical effect of pump phase shift on stability, shape of response curves and bandwidth is illustrated. Results of noise measurements will be given and compared with theory.

A Resonant Cavity Linear Accelerator

A folded rectangular wave guide cavity, resonant at a frequency of 2800 megacycles, is used to accelerate electrons which are injected at 2000 volts energy to an energy of 300 kilovolts. Three accelerating stages are provided, the power source being a type 4J33 radar magnetron operating on a duty cycle of 2×10−4. Power output of the magnetron is 800 kilowatts, the power consumed by the cavity being approximately 250 kilowatts. Design data for the cavity are obtained from slotted wave guide models of the cavity sections.

Studies on Amphibian Metamorphosis

ABSTRACT The histolysis of the anuran operculum during forelimb perforation formation has been accredited to the action of autolysing gill tissue, to cutaneous gland secretions, and to self-degeneration of the integument by Helff, Weber, and Blacher et al. respectively. The writer has reinvestigated the problem as follows: Opercular integument, homoplastically transplanted to the back and side of R. temporaria larvae, underwent a process of partial degeneration. The histolysis was not confined to any localized region of the transplant. Autoplastic transplantation of opercular integument to the back and side produced a variety of results. Normal histological structure was maintained in certain transplants, generalized degeneration was observed in others, while in several instances localized histolysis resulting in perforation formation occurred. Homoplastic and autoplastic transplantation of back and side skin to the opercular region resulted in histolysis and perforation formation in such transplants during larval involution. The right forelimbs (in early stages of development) with attached portions of the shoulder girdle were extirpated in R. temporaria and B. bufo. During subsequent metamorphosis, normal opercular histolysis followed by perforation formation in many cases was observed. In most instances, serial sections of the peribranchial cavity revealed the absence of cutaneous glands. Extirpation of the right forelimb only was made in the same two species. Opercular histolysis subsequently occurred in all instances, resulting in perforation formation in the great majority of cases during larval involution. In many of the B. bufo animals two separate perforations developed, one filled with limb stump and the other with gill tissue. It is concluded that in R. temporaria a particular area of the operculum may in some individuals possess self-degenerative potentialities conducive to histolysis and perforation formation during metamorphosis. In both R. temporaria and B. bufo histolytic influences emanating from the atrophying gill tissue and the cutaneous glands of the forelimb are probably also responsible for operêular histolysis and perforation formation. Limb pressure must be considered a supplemental factor. The results are discussed in general and attention called to the fact that opercular histolysis and perforation formation are “doubly assured” in some species and possibly even “triply assured” in others. Emphasis is placed on the evidently wide divergence between species as regards the particular combination of factors responsible for opercular histolysis and perforation formation. Apparently, no one explanation can serve to account for the phenomenon as it occurs in various species of anurans.

Notes upon some Specimens of Shropshire Rocks

(55) Lyd's Hole, Pontesbury .—A rhyolite, with well-marked fluidal structure, much stained with ferrite and with occasional patches of opacite. The rock exhibits a devritrified structure, the crystallites in most parts assuming an acicular form, the majority no doubt being felspar; but some, of a pale golden colour, must be a different mineral, possibly a mica allied to sericite. There seems in parts a tendency to a microspherulitic and even micrographic structure; the ferruginous constituents assume many forms, from mere specks to little rods and granules. There are two or three larger crystals of felspar, containing apparently glass inclusions: the fluidal bands are crossed transversely by a much more deeply stained zone. The rock has a general similarity to those common in the neighbourhood of the Wrekin. (56) Pontesford Hill, North-End Quarry .—A remarkably beautiful specimen. The slide gives a complete section of an elongated cavity filled with chalcedony . The enclosing border of rock is a rhyolite; this has a fluidal structure parallel to the longer axis of the concretion, is deeply stained with ferrite, and exhibits in tis crstallites indications of radial structure normal to the longer axis; within this is a zone of chalcedony, sometimes containing fragments of the rhyolite, the microliths of quartz being grouped in radiating tufts like the hairs in a sable-brish, a familiar appearance in agates; in places also they form regular spherulites; within this is an enclosure of minutely crystalline quartz. These hollow spherulitic concretions, subsequently partially or wholly filled by infiltrated minerals,