Superconducting cavities

Pfister, Hugo

doi:10.1016/0011-2275(76)90281-2

Cited by 50 publications

(9 citation statements)

References 33 publications

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“…The highest competitive trait anxiety level was present in athletes engaged in collision sports, while the lowest was present in athletes from non-contact sports, which is consistent with foundings of Pfister (1976) and Ichraf et al (2013). Previous studies have shown that strong emotions, even the negative ones such as anxiety, anger, rage and tension, can generate more energy, and thus enable the athletes to withstand a larger effort needed in situations of high collision (Cerin, 2003;Martin & Gill, 1991;Ruiz & Hanin, 2011).…”

Section: Discussionsupporting

confidence: 88%

Competitive trait anxiety and general self-esteem of athletes according to the sport type and gender

Sanader

Petrović

Bačanac

et al. 2021

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Traditionally, anxiety has been interpreted as a negative emotional state characterized by nervousness, worry, fret, uncertainty and vague fear which could have an adverse effect on sports achievement. On the other hand, sport type and its specific nature and demands, may also be connected with the level of state and trait anxiety. This study aimed to investigate potential differences in the competitive trait anxiety level and general self-esteem according to gender in sports of different contact level. The sample consisted of 1024 (590 males and 434 females) young athletes. Independent variables were sport contact level (non-contact, contact and collision sports) and gender. Dependent variables were measured by the adjusted versions of Sport Competition Anxiety Test and Rosenberg Self-Esteem Scale. Basic descriptive statistics was calculated for all the groups, and the differences between them were established using χ² test and MANOVA. The results suggest significant differences in trait competitive anxiety per sport type, gender and their interaction, and no differences in the general self-esteem level. The current study reveals that not only the intensity but also the intergroup relationship of a sport contact level (non-contact, contact and collision sports) is gender determined. These findings are important in psycho-diagnostic procedure and choosing appropriate coping strategies for athletes.

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Section: Discussionsupporting

confidence: 88%

Competitive trait anxiety and general self-esteem of athletes according to the sport type and gender

Sanader

Petrović

Bačanac

et al. 2021

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“…It was a common practice in the early days of SRF cavities to anodize the inner surface to grow an oxide layer with a thickness in the range of 0:1 m [33,34]. It was found that the anodic oxide film not only proved suitable as a protective film, but also produced a considerable increase in the quality factor and the critical magnetic field.…”

Section: Fe Results and Discussionmentioning

confidence: 99%

Field emitter activation on cleaned crystalline niobium surfaces relevant for superconducting rf technology

Navitski

Lagotzky

Reschke

et al. 2013

Phys. Rev. ST Accel. Beams

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The influence of heat treatments at 122, 400, and 800 C on the field emission of large-grain and single-crystal high-purity niobium samples has been investigated. Buffered chemical polishing of 40 m and high pressure ultrapure water rinsing under clean-room conditions resulted in smooth surfaces with a linear surface roughness of 46 to 337 nm. By means of field emission scanning microscopy, an increasing number of emitters up to 40=cm 2 with temperature were found at surface fields up to 160 MV=m. Two different mechanisms of emitter activation were found, i.e. activation by the applied electric field and activation by temperature. Some emitters with an onset surface field of 50 to 100 MV=m appeared already after the low-temperature bakeout. Correlated scanningelectron-microscopy/energy-dispersive-x-ray measurements revealed particles and surface defects as emitters. Their activation will be discussed with respect to the thickness of the insulating oxide layer.

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“…Anodization was commonly used for the preparation of niobium cavities in the 1970s [16], allowing one to elec- trochemically grow an amorphous Nb 2 O 5 film whose thickness depends mainly on the voltage applied between the cavity (anode) and a cathode. For this study, the cavity is filled with NH 4 OH (15%), and a constant voltage is applied between the cavity and a Nb rod inserted in the cavity.…”

Section: Anodizationmentioning

confidence: 99%

Measurement of the high-fieldQdrop in a high-purity large-grain niobium cavity for different oxidation processes

Ciovati

Kneisel

Gurevich

2007

Phys. Rev. ST Accel. Beams

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The most challenging issue for understanding the performance of superconducting radio-frequency (rf) cavities made of high-purity (residual resistivity ratio >200) niobium is due to a sharp degradation (''Q-drop'') of the cavity quality factor Q 0 B p as the peak surface magnetic field (B p) exceeds about 90 mT, in the absence of field emission. In addition, a low-temperature (100-140 C) in situ baking of the cavity was found to be beneficial in reducing the Q-drop. In this contribution, we present the results from a series of rf tests at 1.7 and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm 2) grain niobium which underwent various oxidation processes, after initial buffered chemical polishing, such as anodization, baking in pure oxygen atmosphere, and baking in air up to 180 C, with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system allows measuring the local temperature rise of the cavity outer surface due to rf losses, which gives information about the losses location, their field dependence, and space distribution. The results confirmed that the depth affected by baking is about 20-30 nm from the surface and showed that the Q-drop did not reappear in a previously baked cavity by further baking at 120 C in pure oxygen atmosphere or in air up to 180 C. These treatments increased the oxide thickness and oxygen concentration, measured on niobium samples which were processed with the cavity and were analyzed with transmission electron microscope and secondary ion mass spectroscopy. Nevertheless, the performance of the cavity after air baking at 180 C degraded significantly and the temperature maps showed high losses, uniformly distributed on the surface, which could be completely recovered only by a postpurification treatment at 1250 C. A statistic of the position of the ''hot spots'' on the cavity surface showed that grain boundaries are not the preferred location. An interesting correlation was found between the Q-drop onset, the quench field, and the low-field energy gap, which supports the hypothesis of thermomagnetic instability governing the Q-drop and the baking effect.

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Superconducting cavities

Cited by 50 publications

References 33 publications

Competitive trait anxiety and general self-esteem of athletes according to the sport type and gender

Competitive trait anxiety and general self-esteem of athletes according to the sport type and gender

Field emitter activation on cleaned crystalline niobium surfaces relevant for superconducting rf technology

Measurement of the high-fieldQdrop in a high-purity large-grain niobium cavity for different oxidation processes

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