Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session QR2: Plasma Applications in Accelerator Technology |
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Chair: Keith Cartwright, Sandia National Laboratory Room: State C |
Thursday, November 6, 2014 3:30PM - 4:00PM |
QR2.00001: The Grand Challenges for Engineering in the 21st Invited Speaker: Thomas Katsouleas The Grand Challenges for Engineering in the 21st century identified by the NAE re-frame the engineering profession in human facing terms rather than in terms of disciplines or devices. ~Nevertheless, plasmas will play a major role in solving many of these challenges. ~The challenges involve making the world more sustainable, more healthful, more secure and more joyful. ~From the challenge of Provide Clean Water (to nearly a billion people who lack regular access to it), to Provide Energy from Fusion and Engineer the Tools of Scientific Discovery, plasmas will play an essential role. ~This talk highlights progress on the NAE Grand Challenges and the role that plasmas are playing in addressing them. ~Particular attention will be given to plasma-based particle accelerators and the question of whether they really offer a path to smaller, cheaper accelerators that could impact human health through cancer therapies or enable new discoveries at the high energy frontier. ~ [Preview Abstract] |
Thursday, November 6, 2014 4:00PM - 4:30PM |
QR2.00002: Gaseous Electronics Phenomena in Particle Accelerators Invited Speaker: Svetozar Popovic The work is motivated by the development of new compact superconducting RF (SRF) accelerating structures that are capable of producing gradients in excess of 100 MV$/$m. Compact accelerators and accelerator-based light sources are currently expected to have numerous applications ranging from use in medicine to high-energy physics. However, they require more compact accelerating cavities and components for beam control. Developing and operation of compact particle accelerators involve a multitude of concepts that are analogue to those developed in the traditional disciplines of gaseous electronics. Non-planar, asymmetric superconductor surface treatment using radiofrequency discharges applies techniques that are analogue to those used in the development of planar micro- and nano-electronic devices, although performed on much larger and curved surfaces. During operation, compact particle accelerators behave as pulsed power devices. Just as in the pulsed power devices, it has been reported that all compact concepts are inclined to support the field emission and the multipactor effects that, in turn, limit their range of operation. Multipactor discharge presents a major boulder in the development of compact accelerators and light sources. Multipactor is a resonant discharge generated by the RF field where the growth in the electron density is sustained by secondary emission from cavity walls driven by the RF power that is used for particle acceleration. If more than one electron is emitted for each primary electron, the rate of electron density growth could become high enough to dissipate a significant fraction of the RF power inside the cavity before the saturation due to space-charge or other effects sets in. Using the archived data collection on the performance tests of SRF accelerator components, we identify the relevant gaseous electronics phenomena and their mechanisms. We also review the efforts on mitigation of detrimental effects. [Preview Abstract] |
Thursday, November 6, 2014 4:30PM - 4:45PM |
QR2.00003: Uniform Plasma Etching of Complex Shaped Three Dimensional Niobium Structures for Particle Accelerators Janardan Upadhyay, Do Im, Jeremy Peshl, Svetozar Popovic, Lepsha Vuskovic, Larry Phillips, Anne-Marie Valente-Felliciano Complex shaped three dimensional niobium structures are used in particle accelerators as super conducting radio frequency (SRF) cavities. The inner surfaces of these structures have to be chemically etched for better performance, as SRF performance parameters are very sensitive to their properties. Plasma etching of inner surface of three dimensional niobium structures has not been reported even though plasma etching of niobium has been reported earlier for Josephson junction and other applications. We are proposing an RF capacitively coupled coaxial (ccp) plasma etching method for nano machining of niobium structures for SRF applications. We are using gas mixture of Argon and Chlorine. We report the effects of the pressure, RF power, gas concentration, shape and size of the inner electrode, temperature of the structure, DC bias voltage and residence time on the etch rate of the niobium. We also show the method to reduce the asymmetry effect in coaxial ccp by changing the shape of the inner electrode in cylindrical structure, as well as a method to overcome the severe loading effect in etching of 3D structures for uniform mass removal purpose. [Preview Abstract] |
Thursday, November 6, 2014 4:45PM - 5:00PM |
QR2.00004: ABSTRACT WITHDRAWN |
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