[en] Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nano-smoothness. Electropolishing (EP) is the technique of choice being developed for high-field SRF cavities. Previous study has shown that the mechanism of Nb electropolishing proceeds by formation and dissolution of a compact salt film under fluorine diffusion-limited mass transport control. We pursue an improved understanding of the microscopic conditions required for optimum surface finishing. The viscosity of the standard electrolyte has been measured using a commercial viscometer, and the diffusion coefficient of fluorine was derived at a variety of temperatures from 0 C to 50 C using an Nb rotating disk electrode. In addition, data indicate that electrode kinetics becomes competitive with the mass transfer current limitation and increases dramatically with temperature. These findings are expected to guide the optimization of EP process parameters for achieving controlled, reproducible and uniform nano-smooth surface finishing of SRF cavities.

[en] Superconducting rf (SRF) technology is evolving rapidly, as are its applications. While there is active exploitation of what one may call the current state-of-the-practice, there is also rapid progress in expanding in several dimensions the accessible and useful parameter space. While state-of-the-art performance sometimes outpaces thorough understanding, the improving scientific understanding from active SRF research is clarifying routes to obtain optimum performance from present materials and opening avenues beyond the standard bulk niobium. The improving technical basis understanding is enabling process engineering to improve both performance confidence and reliability and also unit implementation costs. Increasing confidence in the technology enables the engineering of new creative application designs. We attempt to survey this landscape to highlight the potential for future accelerator applications

[en] The Large Area Telescope (LAT) is one of two instruments on board the Gamma-ray Large Area Telescope (GLAST), the next generation high energy gamma-ray space telescope. The LAT contains sixteen identical towers in a four-by-four grid. Each tower contains a silicon-strip tracker and a CsI calorimeter that together will give the incident direction and energy of the pair-converting photon in the energy range 20 MeV - 300 GeV. In addition, the instrument is covered by a finely segmented Anti-Coincidence Detector (ACD) to reject charged particle background. Altogether, the LAT contains more than 864k channels in the trackers, 1536 CsI crystals and 97 ACD plastic scintillator tiles and ribbons. Here we detail some of the strategies and methods for how we are planning to monitor the instrument performance on orbit. It builds on the extensive experience gained from Integration and Test and Commissioning of the instrument on ground

[en] Culture is a set of behaviors and expectations that are common to a group. An organization’s culture is a reflection of common behaviors and expectations. Consequently, an organization’s culture will determine its success or failure. The challenge for most organizations is to develop its own culture, rather than to watch as it evolves. To develop an organizational culture, the organization’s leadership must understand the key attributes of culture, and how they relate to their mission and vision. The first step it to identify the key attributes of organizational culture. There are 12 key cultural attributes that should be considered, and then developed: • Mission Clarity • Standardization • Fully Empowered Employees • A High Integrity Workplace • Strong Trust Relationships • Highly Effective Leadership • Effective Processes • Responsiveness to Internal Customers • Effective Communications • A High Degree of Adaptability • High Accountability Standards • Emphasis on Recruiting/Retaining the Best Employees Each cultural attribute must be defined, and then be applied to help the organization meet its vision and mission. Policies and programs must then be developed and applied to ensure the organization’s culture is created and managed, rather than allowing it to evolve. Because cultural attributes are not easily quantified, a subjective scale will need to be developed, which can then be applied to compare a) trends in the organization’s culture over time, and b) to allow the culture to be compared to external organizations. This paper will discuss the 12 key organizational cultural attributes, describe why they are needed for an organization to be successful, and provide examples of strong and weak organizational cultural elements at selected nuclear energy programs. (author)

[en] A strategy to enable zero-carbon variable electricity production with full utilization of renewable and nuclear energy sources has been developed. Wind and solar systems send electricity to the grid. Nuclear plants operate at full capacity with variable steam to turbines to match electricity demand with production (renewables and nuclear). Excess steam at times of low electricity prices and electricity demand go to hybrid fuel production and storage systems. The characteristic of these hybrid technologies is that the economic penalties for variable nuclear steam inputs are small. Three hybrid systems were identified that could be deployed at the required scale. The first option is the gigawatt-year hourly-to-seasonal heat storage system where excess steam from the nuclear plant is used to heat rock a kilometer underground to create an artificial geothermal heat source. The heat source produces electricity on demand using geothermal technology. The second option uses steam from the nuclear plant and electricity from the grid with high-temperature electrolysis (HTR) cells to produce hydrogen and oxygen. Hydrogen is primarily for industrial applications; however, the HTE can be operated in reverse using hydrogen for peak electricity production. The third option uses variable steam and electricity for shale oil production. -- Highlights: •A system is proposed to meet variable hourly to seasonal electricity demand. •Variable solar and wind electricity sent to the grid. •Base-load nuclear plants send variable steam for electricity and hybrid systems. •Hybrid energy systems can economically absorb gigawatts of variable steam. •Hybrid systems include geothermal heat storage, hydrogen, and shale-oil production

[en] The US Department of Energy has funded a near-complete renovation of the SRF-based accelerator research and development facilities at Jefferson Lab. The project to accomplish this, the Technical and Engineering Development Facility (TEDF) Project has completed the first of two phases. An entirely new 3,100 m² purpose-built SRF technical work facility has been constructed and was occupied in summer of 2012. All SRF work processes with the exception of cryogenic testing have been relocated into the new building. All cavity fabrication, processing, thermal treatment, chemistry, cleaning, and assembly work is collected conveniently into a new LEED-certified building. An innovatively designed 800 m2 cleanroom/chemroom suite provides long-term flexibility for support of multiple RandD and construction projects as well as continued process evolution. The characteristics of this first 2nd-generation SRF facility are described

[en] Electron field emission (FE) from broad-area metal surfaces is known to occur at a much lower electric field than predicted by the Fowler-Nordheim law. This enhanced field emission (EFE) presents a major impediment to high electric field operation in a variety of applications, e.g., in superconducting niobium radio-frequency cavities for particle accelerators, klystrons, and a wide range of high voltage vacuum devices. Therefore EFE has been the subject of wide fundamental research for years. Although micron or submicron particles are often observed at such EFE sites, the strength and number of emitting sites and the causes of EFE strongly depend on surface preparation and handling, and the physical mechanism of EFE remains unknown. To systematically investigate the sources of this emission and to evaluate the best available surface preparation techniques with respect to resulting field emission, a DC scanning field emission microscope (SFEM) has been built at Thomas Jefferson National Accelerator Facility (Jefferson Lab). Broad-area samples can be moved laterally in a raster pattern (2.5 mu-m step resolution) under a high voltage micro-tip for EFE detection and localization in the SFEM. The emitting sites can then be characterized by SEM and EDX without breaking ultra high vacuum. EFE sources from planar Nb have been studied after preparation by chemical etching and electropolishing combined with ultrasonic deionized water rinse (UWR). Emitters have been identified and analyzed, and the preparation process has been refined and improved based on scan results. With the improved preparation process, field-emission-free or near field-emission-free surfaces at -140 MV/m have been achieved consistently on a number of samples

[en] Miles' equation models the amplitude modulation of a Faraday wave. A dynamical system study is conducted on this concrete physical model. It turns out that a quartet of heteroclinic orbits can be located, but we fail to locate any homoclinic orbit. For a generalized Miles' equation, a quartet of homoclinic orbits can be located, and existence of chaos can be proved under certain generic assumptions

[en] Sine-Gordon equation under a quasi-periodic perturbation or a chaotic perturbation is studied. Existence of a homoclinic tube is proved. Established are chaos associated with the homoclinic tube, and 'chaos cascade' referring to the embeddings of smaller scale chaos in larger scale chaos

[en] Electron field emission (FE) from broad-area metal surfaces is known to occur at much lower electric field than predicted by Fowler-Nordheim law. Although micron or submicron particles are often observed at such enhanced field emission (EFE) sites, the strength and number of emitting sites and the causes of EFE strongly depend on surface preparation and handling, and the physical mechanism of EFE remains unknown. To systematically investigate the sources of this emission, a DC scanning field emission microscope (SFEM) has been built as an extension to an existing commercial scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer (EDX/EDS) for emitter characterization. In the SFEM chamber of ultra high vacuum (∼10-9 Torr), a sample is moved laterally in a raster pattern (2.5 mm step resolution) under a high voltage anode micro-tip for field emission detection and localization. The sample is then transferred under vacuum by a hermetic retractable linear transporter to the SEM chamber for individual emitter site characterization. Artificial marks on the sample surface serve as references to convert x, y coordinates of emitters in the SFEM chamber to corresponding positions in the SEM chamber with a common accuracy of ±100-200 mm in x and y. Samples designed to self-align in sample holders are used in each chamber, allowing them to retain position registration after non-in situ processing to track interesting features. No components are installed inside the SEM except the sample holder, which doesn't affect the routine operation of the SEM. The apparatus is a system of low cost and maintenance and significant operational flexibility. Field emission sources from planar niobium, the material used in high-field RF superconducting cavities for particle accelerator, have been studied after different surface preparations, and significantly reduced field emitter density has been achieved by refining the preparation process based on scan results. Scans on niobium samples at ∼ 140 MV/m are presented to demonstrate the performance of the apparatus