Simulations of Coaxial Wire Measurements of the Impedance of Asymmetric Structures

Coaxial wire measurements have provided a simple and effective way to measure the beam coupling impedance of accelerator structures for a number of years. It has been known how to measure the longitudinal and dipolar transverse impedance using one and two wires for some time. Recently the ability to measure the quadrupolar impedance of structures exhibiting top/bottom and left/right symmetry has been demonstrated. A method for measuring the beam coupling impedance of asymmetric structures using displaced single wires and two wire measurements is proposed. Simulations of the measurement system are presented with further work proposed

Comparison of the current LHC Collimators and the SLAC Phase 2 Collimator Impedances

One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design

Evaluation of the Beam Coupling Impedance of New Beam Screen Designs for the LHC Injection Kicker Magnets

During the 2011 run of the LHC there was a significant measured temperature increase in the LHC Injection Kicker Magnets (MKI) during operation with 50ns bunch spacing. This was due to increased beam-induced heating of the magnet due to beam impedance. Due to concerns about future heating with the increased total intensity to nominal and ultimate luminosities a review of the impedance reduction techniques within the magnet was required. A number of new beam screen designs are proposed and their impedance evaluated. Heating estimates are also given with a particular attention paid to future intensity upgrades to ultimate parameters

Coaxial Wire Measurements of Ferrite Kicker Magnets

Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed

Angiogenic Effect of Bioactive Borate Glass Microfibers and Beads in the Hairless Mouse

The purpose of this project was to investigate the angiogenic mechanism of bioactive borate glass for soft tissue repair in a \u27hairless\u27 SKH1 mouse model. Subcutaneous microvascular responses to bioactive glass microfibers (45S5, 13-93B3, and 13-93B3Cu) and bioactive glass beads (13-93, 13-93B3, and 13-93B3Cu) were assessed via: noninvasive imaging of skin microvasculature; histomorphometry of microvascular densities; and quantitative PCR measurements of mRNA expression of VEGF and FGF-2 cytokines. Live imaging via dorsal skin windows showed the formation at two weeks of a halo-like structure infused with microvessels surrounding implanted borate-based 13-93B3 and 13-93B3Cu glass beads, a response not observed with silicate-based 13-93 glass beads. Quantitative histomorphometry of tissues implanted with plugs of 45S5, 13-93B3, and 13-93B3Cu glass microfibers revealed microvascular densities that were 1.6-, 2.3-, and 2.7-times higher, respectively, than the sham control values whereas 13-93, 13-93B3, and 13-93B3Cu glass beads caused the microvascular density to increase 1.3-, 1.6-, and 2.5-fold, respectively, relative to sham controls. Quantitative PCR measurements indicate a marginally significant increased expression of VEGF mRNA in tissues with 13-93B3Cu glass beads, an outcome that supported the hypothesis that copper-doped borate glass could promote VEGF expression followed by angiogenesis for enhanced wound healing

Scaffold for Tissue Regeneration in Mammals

A three-dimensional scaffold with interconnected pores for repair of tissue comprising a scaffold body for structural support of the tissue scaffold, where the scaffold body comprises scaffold body components bonded to each other and made from component materials comprising about 40 to about 90 wt % B2O3, and two or more other oxides, wherein the scaffold body has a porosity between about 15 and about 90 vol %

Exploring the Unknown: Selected Documents in the History of the U.S. Civilian Space Program

The documents selected for inclusion in this volume are presented in three chapters, each covering a particular aspect of the evolution of U.S. space exploration. These chapters address (1) the relations between the civilian space program of the United States and the space activities of other countries, (2) the relations between the U.S. civilian space program and the space efforts of national security organizations and the military, and (3) NASA's relations with industry and academic institutions

Combining uretdione and disulfide reversibly degradable polyurethanes : route to alternating block copolymers

Uretdione (temperature and catalyst controlled) and disulphide (REDOX controlled) functionalised polyurethanes have been described and the reversibility of these bonds tested. The polymers have been synthesised with reversible covalent groups present throughout their backbone, developing routes to reversibly degradable polyurethanes. These materials degrade and reheal in response to different external stimuli, which supplies a proof of concept for controlling the molecular weight, and therefore, the physical properties of a polyurethane. Further, a unique route to an alternating block copolymer is also discussed that utilises a mixture of disulphide and uretdione functionalised polymers as the reagents to form a thiourethane. The dramatically reduced safety hazards of dealing with the functionalised polymers, in comparison to the free isocyanate and thiols, could be of great interest to industrial application for current drives towards safer routes to polyurethanes