[en] There are hundreds of high power klystrons operated in the Linac gallery and about fifty to sixty tubes fail every year. The lifetime ranges from a few thousand up to seventy thousand hours except those which fail during an early period. The overall percentage of failures due to emission problems is approximately 25%. It is also noted that a 10% increase in mean lifetime of klystrons will reduce the overall cost per hour as much as a 10% increase in efficiency. Therefore, it is useful to find some method to predict the expected life of an individual tube. The final goal has not been attained yet, but some useful information was obtained. It is thought that this information might be helpful for those people who will study this subject further

[en] A new scheme is proposed for the muon collider cooling RF, on which the cavity is almost a simple pillbox. The principle is to divide the accelerating cells into three separate channels with a phase difference of 2π/3 between each other. A special structure is designed in which each channel is like a side-coupled cavity structure operating at π/2-mode, but an extra phase shift of π is introduced so that the phase difference between two cells is 2π. Therefore, the beam sees a 2π/3-mode implying a high interaction between cavities and beam, while the RF system sees a π/2-mode implying a high stability. In other words, it combines the advantages of both traveling wave and standing wave. The mechanical structure is also simple and compact because the side-coupled cavity is formed by a uniform rectangular-like waveguide, which is simply an arc section attached on the main cavities. The principle and the preliminary simulation are addressed in detail. This principle is also applicable for a 2π/4 mode and other machine provided the coupling due to aperture is weak enough

[en] Morphology, dielectric breakdown and mechanical properties have been studied in a number of model polyolefin systems. The TEM investigation of the morphology of a propylenelethylene copolymer containing a clarifying additive showed that the addition of the clarifier generally results in enhanced nucleation and the consequent formation of a more uniform structure. However, the morphology of the copolymer is shown to change abruptly from a fine to a coarse structure when the crystallisation temperature exceeds 128 deg. C. This is associated with a marked reduction in nucleation efficiency of the additive, which permits the growth of distinct spatially separated morphological features. These morphological features have further been clarified by investigation of the morphology of the pure copolymer, which was nucleated using self-seeding technique. A number of characteristic forms of lamellar aggregates present either in the clarified or pure copolymer are evidenced as a result of different directions in which they are viewed. Two distinct types of lamellae are found: lath-like crystals and cross-hatching lamellae. The former results from primary crystallisation, whereas the later is associated with secondary crystallisation. The different populations of lamellae correspond to multiple melting peaks observed in DSC traces. The electric strength of the clarified propylenelethylene copolymer exhibits a clear dependence on sample morphology. The parallel trend is also found in the mechanical ultimate failure stress and strain of the material, as recorded at the relatively high strain rate of 100 mm/min. The electrical tree growth in this material is significantly dependent on morphology. At the same electrical treeing condition, a branch-type tree forms in the quenched sample with a uniform structure, whereas a bush-type tree develops in the 134 deg. C crystallised sample with a coarse morphology. A CCD camera shows that the branch-type tree is electrically conducting, whereas the bush-type tree is non-conducting. The tree growth rate as a function of applied voltage in the two samples also exhibits different forms. The morphology of a linear/branched polyethylene blend has been investigated by SEM. The morphology of this system can be controlled appropriately by varying the thermal history. Open banded spherulites are formed at lower crystallisation temperatures, which impinge upon one another, whereas higher temperature crystallisation results in sheaf-like lamellar aggregates, which are distinct and separated by a low crystallinity matrix. The mechanical properties of this system are also examined, and are found to vary with the morphology of the material. Tree channels in the polyethylene blend are very clearly revealed. The location of the channels is significantly dependent on the microstructure of the material. Most of channels are distributed in low crystallinity regions, particularly, at the boundaries of spherulites. The structure of channels themselves is also revealed. Two types of channel are found; one, with a shell, appears electrically conducting, whereas, the other, with no shell, appears non-conducting. The formation of the different types of channel depends on both the treeing conditions and the morphology of the material. (author)

[en] This note addresses the general concerns for the design of a ferrite cavity. The parameters are specified for the RCMS, for which the frequency ramp is in the range of 1.27 MHz to 6.44 MHz, or a ratio of 1:5

[en] An FFAG moot likely requires rapid cavity tuning. The cavity must also have a very high gradient. To satisfy both the high power and rapid tuning requirements is a big challenge. Detailed investigation of the possibility is addressed. Included are general thoughts, dual-loop and simple loop analyses, and a study of using ferrite or PIN diodes. Also proposed is a phase control scheme, which may be a better solution if the needed components can be developed. Finally, an energy analysis reveals the difficult of high power tuning

[en] The cluster klystron project required a beam monitor to check the quality of the hollow beam shape. Since the power density of the beam is very large, a common phosphorescent screen doesn't work. We investigated varies types of monitors. The related problems were also discussed

[en] This note addresses the various options for the Rapid Cycling Medical Synchrotron (RCMS) RF. The study was divided into three cases, namely non-tuning, tuning and filter. Each case also includes a few options. The primary study was focused on the non-tuning options. However, it was found that it requires too much driver power to cover the wide band and thus causes the cost being too high to be competitive. The proposal of RCMS is not yet clear if it can be approved or not. The results of this study might be useful to other similar machines

[en] A superconducting cavity used in a microwave gun requires that the launcher and the pickup probes be on the same side of the cavity, which causes direct coupling between them, or crosstalk. At room temperature, the crosstalk causes serious distortion of the RF response. This note addresses the phenomenon, the simulation results and the analysis, so that one can extract the desired information from the confusing signal

[en] The Muon Collider and Neutrino Factory projects require low frequency rf cavities because the size and emittance of the muon beam is much larger than is usual for electron or proton beams. The range of 30 MHz to 200 MHz is of special interest. However, the size of an accelerator with low frequency will be impractically large if it is simply scaled up from usual designs. In addition, to get very high peak power in this range is difficult. Presented in this paper is an alternative structure that employs a quasi-lumped inductance that can significantly reduce the transverse size while keeping high gradient. Also addressed is a power compression scheme with a thyratron. This gives a possible solution to provide very high peak power

[en] Cone-cylinder intersections are used commonly in pressure vessels and piping, and internal pressurization is often an important loading condition. For the intersection of the large end of a cone and a cylinder, internal pressurization causes large circumferential compressive stresses in the intersection. These stresses can lead to failure of the intersection by either axisymmetric collapse or non-symmetric buckling. This paper first presents a brief summary of recent experiments on cone-cylinder intersections under internal pressure. A rational finite element model based on the experimental and the corresponding numerical results is next described. Finite element results from a major parametric study on the postbuckling behaviour and strength of cone-cylinder intersections employing this finite element model are then presented. Finally, a design proposal in the Eurocode format for internally pressurized cone-cylinder intersections is established for practical use