Investigation of two-frequency Paul traps for antihydrogen production

Radio-frequency (rf) Paul traps operated with multifrequency rf trapping potentials provide the ability to independently confine charged particle species with widely different charge-to-mass ratios. In particular, these traps may find use in the field of antihydrogen recombination, allowing antiproton and positron clouds to be trapped and confined in the same volume without the use of large superconducting magnets. We explore the stability regions of two-frequency Paul traps and perform numerical simulations of small, multispecies charged-particle mixtures that indicate the promise of these traps for antihydrogen recombination.Comment: 11 pages, 10 figure

Dynamics of gas phase Ne∗^* + NH3_3 and Ne∗^* + ND3_3 Penning ionization at low temperatures

Two isotopic chemical reactions, $\mathrm{Ne}^*$ + NH$_3$, and $\mathrm{Ne}^*$ + ND$_3$, have been studied at low collision energies by means of a merged beams technique. Partial cross sections have been recorded for the two reactive channels, namely $\mathrm{Ne}^*$ + NH$_3$ $\rightarrow$ Ne + NH$_3^+$ + $e^-$, and $\mathrm{Ne}^*$ + NH$_3$ $\rightarrow$ Ne + NH$_2^+$ + H + $e^-$, by detecting the NH$_3^+$ and NH$_2^+$ product ions, respectively. The cross sections for both reactions were found to increase with decreasing collision energy, $E_{coll}$, in the range 8 $\mu$eV$<E_{coll}<$ 20 meV. The measured rate constant exhibits a curvature in a log(k)-log($E_{coll}$) plot from which it is concluded that the Langevin capture model does not properly describe the $\mathrm{Ne}^*$ + NH$_3$ reaction in the entire range of collision energies covered here. Calculations based on multichannel quantum defect theory were performed to reproduce and interpret the experimental results. Good agreement was obtained by including long range van der Waals interactions combined with a 6-12 Lennard-Jones potential. The branching ratio between the two reactive channels, $\Gamma = \frac{[NH_2^+]}{[NH_2^+]+[NH_3^+]}$, is relatively constant, $\Gamma\approx 0.3$, in the entire collision energy range studied here. Possible reasons for this observation are discussed and rationalised in terms of relative time scales of the reactant approach and the molecular rotation. Isotopic differences between the $\mathrm{Ne}^*$ + NH$_3$ and $\mathrm{Ne}^*$ + ND$_3$ reactions are small, as suggested by nearly equal branching ratios and cross sections for the two reactions

Robust Reliability or reliable robustness? - Integrated consideration of robustness and reliability aspects

Commonly, the terms reliability and robustness are used to describe products and processes, which are in accordance with the customer requirements and fulfil high quality expectations. However, significant differences between the underlying definitions raise the questions how reliable robust products are and vice versa. For a comprehensive understanding and to use existing synergies between both domains, this paper discusses the basic principles of Reliability- and Robust Design theory. The development of a comprehensive model will enable an integrated consideration of both domains in the future, will offer guidance for a systematic choice of corresponding methods and is thus aiming to pave the way for future research.Als zuverlässig bzw. robust werden im Allgemeinen Produkte oder Prozesse beschrieben, die den bestehenden Qualitätsanforderungen entsprechen. Gleichzeitig haben Definitionen aus dem Bereich Zuverlässigkeitstechnik und Robust Design allerdings keine grundlegende Übereinstimmung. In Wissenschaft und Praxis ist weitgehend ungeklärt, inwieweit die Entwicklung robuster Produkte zwangsläufig die geforderte Zuverlässigkeit sicherstellt bzw. ob eine Zuverlässigkeitsanalyse notwendigerweise zur Robustheit führt. Um den zwischen beiden Theorien bestehenden Zusammenhang zu verdeutlichen und gezielt auszunutzen, werden im vorliegen Beitrag Vorteile und potentielle Synergien diskutiert. Die Entwicklung eines grundlegenden Modells für eine integrierte Betrachtung von Produktzuverlässigkeit und -robustheit bietet darüber hinaus erste Leitlinien für die Auswahl geeigneter Entwicklungsmethoden und somit eine geeignete Grundlage für zukünftige Untersuchungen

Modifying the surface electronic properties of YBa2Cu3O7-delta with cryogenic scanning probe microscopy

We report the results of a cryogenic study of the modification of YBa2Cu3O7-delta surface electronic properties with the probe of a scanning tunneling microscope (STM). A negative voltage applied to the sample during STM tunneling is found to modify locally the conductance of the native degraded surface layer. When the degraded layer is removed by etching, the effect disappears. An additional surface effect is identified using Scanning Kelvin Probe Microscopy in combination with STM. We observe reversible surface charging for both etched and unetched samples, indicating the presence of a defect layer even on a surface never exposed to air.Comment: 6 pages, 4 figures. To appear in Superconductor Science and Technolog

Vibration Budget for SuperB

International audienceWe pre­sent a vi­bra­tion bud­get for the Su­perB ac­cel­er­a­tor. This in­cludes ground mo­tion data, mo­tion sen­si­tiv­i­ty of ma­chine com­po­nents, and beam feed­back sys­tem re­quire­ments