High Gradient Superconducting Cavity with Low Surface EM Fields and Well-Suppressed HOMS for the ILC

We present an optimized geometry for a 1.3 GHz superconducting cavity in which the surface electromagnetic fields have been minimized and the bandwidth of the fundamental mode has been maximized. We refer to this design as the New Low Surface Field (NLSF) cavity. Earlier work focused on properties of the fundamental mode. Here we additionally study higher order modes (HOMs), means of damping them, and short range wake fields. A two-band circuit model is employed in order to facilitate rapid characterization of cavity HOMs.Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 201

Hie-Isolde High Beta Cavity Study and Measurements

The upgrade of the ISOLDE machine at CERN foresees a superconducting linac based on two gap independently phased Nb sputtered Quarter Wave Resonators (QWRs) working at 101.28MHz and producing an accelerating field of 6MV/m on axis. A careful study of the fields in the cavity has been carried out in order to pin down the crucial e-m parameters of the structure such as peak fields, quality factor and e-m power dissipated on the cavity wall. A tuning system with about 200kHz frequency range has been developed in order to cope with fabrication tolerances. In this paper we will report on the cavity simulations. The tuning plate design will be described. Finally the frequency measurements on a cavity prototype at room temperature will be presented.Comment: 5 pages, SRF09 Conference in Berli

The design and development of a release mechanism for space shuttle life-science experiments

The design, development, and testing of a release mechanism for use in two life science experiments on the Spacelab 1, 4, and D1 missions is described. The mechanism is a self latching ball lock device actuated by a linear solenoid. An unusual feature is the tapering of the ball lock plunger to give it a near constant breakout force for release under a wide range of loads. The selection of the design, based on the design requirements, is discussed. A number of problems occurred during development and test, including problems caused by human factors that became apparent after initial delivery for crewtraining sessions. These problems and their solutions are described to assist in the design and testing of similar mechanisms

Undergraduate research in primary care: Is it sustainable?

To describe the research project component of the BSc in Primary Health Care and to discuss the issues faced by students and faculty in attempting to complete a student-led research project. Medical schools increasingly expect medical students to undertake research as part of intercalated BSc’s or in self-selected study modules. This research has historically been laboratory based, ‘piggybacking’ onto existing projects. Projects initiated by students themselves and studies in primary care or community settings are more unusual. A qualitative study, based on interviews with students and examiners, triangulated with data from the peer review process and personal observations on the running of the course. A London medical school, running an intercalated BSc in Primary Health Care. We interviewed 24 of 26 students and two external examiners during the interview period of the study. Students successfully undertook research, from initial question through to publication. Overall, 90 dissertations were completed since 1997, of which half used a qualitative methodology (45/90). Ten projects have subsequently been published; there were also 16 conference presentations and 6 research letters. Themes from the interview data include: the students’ strong sense of project ownership, the difficulties of being a novice researcher, the difficulties posed by the research governance hurdles, the beneficial and for some students adverse impact (stress and coping with unsuccessful projects) and finally, the impact on their careers. Students gain considerably from this learning process, not only by undertaking their own research, but they also gain in terms of acquisition of transferable skills such as critical appraisal and improved self-directedness. Project completion and publication rates suggest that programmes developing undergraduate initiated research projects can be as successful as those for other novice researchers. The student-led project is a fragile endeavour, but currently is sustainable. © 2008, Cambridge University Press. All rights reserved

The applicability of MFD thrusters to satellite power systems

The high power self field MPD thruster uses electromagnetic forces rather than electrostatic to accelerate a neutral plasma. The most attractive application of MPD thrusters to satellite power systems is in the area of electric propulsion for a cargo orbit transfer vehicle (COTV). Calculations were performed in order to compare the performance of a COTV using an ion or MPD propulsion system. Results show that the MPD propulsion system gives a shorter trip time with the same power and payload when compared to the ion thruster propulsion system at either value of specific impulse. More important than the trip time benefit may be the advantage a MPD propulsion system provides in system simplicity. Another interesting COTV concept using MPD thrusters is the use of a remote power supply located on the Earth, at GEO, or somewhere in between to transmit power to the COTV in a microwave transmission. The specific impulse at thrust levels of tens of newtons makes a MPD propulsion system a candidate for stationkeeping and attitude control of large space structures such as a SPS

Optically pumped submillimeter-waves and applications

Rapid development of optically pumped lasers has shown the potential to be used as a source for a high resolution spectrometer. In this connection, a compact, stable FIR laser was designed, fabricated, and assembled, integrating both the pump laser and the FIR cavity in the same mechanical structure for its improved (both thermal and mechanical) stability and mobility. Performance of the mixer structure which was designed and constructed for the evaluation of the Schottky diodes was found to be satisfactory. The feasibility of generating tunable sideband for molecular spectroscopy studies was demonstrated

Study of Beam Diagnostics with Trapped Modes in Third Harmonic Superconducting Cavities at FLASH

Off-axis beams passing through an accelerating cavity excite dipole modes among other higher order modes (HOMs). These modes have linear dependence on the transverse beam offset from the cavity axis. Therefore they can be used to monitor the beam position within the cavity. The fifth dipole passband of the third harmonic superconducting cavities at FLASH has modes trapped within each cavity and do not propagate through the adjacent beam pipes, while most other cavity modes do. This could enable the beam position measurement in individual cavities. This paper investigates the possibility to use the fifth dipole band for beam alignment in the third harmonic cavity module. Simulations and measurements both with and without beam-excitations are presented. Various analysis methods are used and compared. A good correlation of HOM signals to the beam position is observed.Comment: 2nd International Particle Accelerator Conference (IPAC '11), San Sebastian, Spain, Sep 4-9, 201