Alkali vapor pressure modulation on the 100ms scale in a single-cell vacuum system for cold atom experiments

We describe and characterize a device for alkali vapor pressure modulation on the 100ms timescale in a single-cell cold atom experiment. Its mechanism is based on optimized heat conduction between a current-modulated alkali dispenser and a heat sink at room temperature. We have studied both the short-term behavior during individual pulses and the long-term pressure evolution in the cell. The device combines fast trap loading and relatively long trap lifetime, enabling high repetition rates in a very simple setup. These features make it particularly suitable for portable atomic sensors.Comment: One reference added, one correcte

Stability of a trapped atom clock on a chip

We present a compact atomic clock interrogating ultracold 87Rb magnetically trapped on an atom chip. Very long coherence times sustained by spin self-rephasing allow us to interrogate the atomic transition with 85% contrast at 5 s Ramsey time. The clock exhibits a fractional frequency stability of $5.8\times 10^{-13}$ at 1 s and is likely to integrate into the $1\times10^{-15}$ range in less than a day. A detailed analysis of 7 noise sources explains the measured frequency stability. Fluctuations in the atom temperature (0.4 nK shot-to-shot) and in the offset magnetic field ($5\times10^{-6}$ relative fluctuations shot-to-shot) are the main noise sources together with the local oscillator, which is degraded by the 30% duty cycle. The analysis suggests technical improvements to be implemented in a future second generation set-up. The results demonstrate the remarkable degree of technical control that can be reached in an atom chip experiment.Comment: 12 pages, 11 figure

Spin waves and Collisional Frequency Shifts of a Trapped-Atom Clock

We excite spin-waves with spatially inhomogeneous pulses and study the resulting frequency shifts of a chip-scale atomic clock of trapped $^{87}$Rb. The density-dependent frequency shifts of the hyperfine transition simulate the s-wave collisional frequency shifts of fermions, including those of optical lattice clocks. As the spin polarizations oscillate in the trap, the frequency shift reverses and it depends on the area of the second Ramsey pulse, exhibiting a predicted beyond mean-field frequency shift. Numerical and analytic models illustrate the observed behaviors.Comment: Will appear soon in Physical Review Letters - Typos correcte

Millimeter-long Fiber Fabry-Perot cavities

We demonstrate fiber Fabry-Perot (FFP) cavities with concave mirrors that can be operated at cavity lengths as large as 1.5mm without significant deterioration of the finesse. This is achieved by using a laser dot machining technique to shape spherical mirrors with ultralow roughness and employing single-mode fibers with large mode area for good mode matching to the cavity. Additionally, in contrast to previous FFPs, these cavities can be used over an octave-spanning frequency range with adequate coatings. We also show directly that shape deviations caused by the fiber's index profile lead to a finesse decrease as observed in earlier attempts to build long FFP cavities, and show a way to overcome this problem

Symmetric microwave potentials for interferometry with thermal atoms on a chip

International audienceA trapped atom interferometer involving state-selective adiabatic potentials with two microwave frequencies on a chip is proposed. We show that this configuration provides a way to achieve a high degree of symmetry between the two arms of the interferometer, which is necessary for coherent splitting and recombination of thermal (i.e., noncondensed) atoms. The resulting interferometer holds promise to achieve high contrast and long coherence time, while avoiding the mean-field interaction issues of interferometers based on trapped Bose-Einstein condensates

Design report of the KISS-II facility for exploring the origin of uranium

One of the critical longstanding issues in nuclear physics is the origin of the heavy elements such as platinum and uranium. The r-process hypothesis is generally supported as the process through which heavy elements are formed via explosive rapid neutron capture. Many of the nuclei involved in heavy-element synthesis are unidentified, short-lived, neutron-rich nuclei, and experimental data on their masses, half-lives, excited states, decay modes, and reaction rates with neutron etc., are incredibly scarce. The ultimate goal is to understand the origin of uranium. The nuclei along the pathway to uranium in the r-process are in "Terra Incognita". In principle, as many of these nuclides have more neutrons than 238U, this region is inaccessible via the in-flight fragmentation reactions and in-flight fission reactions used at the present major facilities worldwide. Therefore, the multi-nucleon transfer (MNT) reaction, which has been studied at the KEK Isotope Separation System (KISS), is attracting attention. However, in contrast to in-flight fission and fragmentation, the nuclei produced by the MNT reaction have characteristic kinematics with broad angular distribution and relatively low energies which makes them non-amenable to in-flight separation techniques. KISS-II would be the first facility to effectively connect production, separation, and analysis of nuclides along the r-process path leading to uranium. This will be accomplished by the use of a large solenoid to collect MNT products while rejecting the intense primary beam, a large helium gas catcher to thermalize the MNT products, and an MRTOF mass spectrograph to perform mass analysis and isobaric purification of subsequent spectroscopic studies. The facility will finally allow us to explore the neutron-rich nuclides in this Terra Incognita.Comment: Editors: Yutaka Watanabe and Yoshikazu Hirayam

Evidence-based school improvement. A research survey from an interdisciplinary point of view

Das Konzept der Evidenzbasierung von Steuerung und professionellem Handeln erfährt im Bildungswesen zunehmende Beachtung. Im Kern geht es darum, empirisch hinreichend belegte Erkenntnisse als "Steuerungswissen" für Politik und Praxis für die Qualitätsentwicklung nutzbar zu machen. Wie erste Befunde aus unterschiedlichen Forschungsdisziplinen jedoch zeigen, lassen sich empirische Erkenntnisse nicht umstandslos in erfolgreiches "evidenzbasiertes" Handeln umsetzen. In diesem Zusammenhang wird eine systematische Bestandsaufnahme des nationalen und internationalen Forschungsstands geleistet. (DIPF/Orig.)The concept of evidence based governance and praxis experiences increasing attention in education. Empirical evidence is meant to serve as \u27control knowledge\u27 for policy and practice to enhance the quality of education systems. However, first results from different research disciplines show that empirical findings cannot be implemented into successful, evidence-based action by implication. In this context, a systematic survey of national and international research is presented. (DIPF/Orig.

Gute Praxis Datenlinkage (GPD) : Good Practice Data Linkage

Das personenbezogene Verknüpfen verschiedener Datenquellen (Datenlinkage) für Forschungszwecke findet in den letzten Jahren in Deutschland zunehmend Anwendung. Jedoch fehlen hierfür konsentierte methodische Standards. Ziel dieses Beitrages ist es, solche Standards für Forschungsvorhaben zu definieren. Eine weitere Intention ist es, dem Lesenden eine Checkliste zur Bewertung geplanter Forschungsvorhaben und Artikel bereitzustellen. Zu diesem Zweck hat eine aus Mitgliedern verschiedener Fachgesellschaften zusammengesetzte Expertengruppe seit 2016 insgesamt 7 Leitlinien mit 27 konkreten Empfehlungen erstellt. Die Gute Praxis Datenlinkage beinhaltet die folgenden Leitlinien: (1) Forschungsziele, Fragestellung, Datenquellen und Ressourcen, (2) Dateninfrastruktur und Datenfluss, (3) Datenschutz, (4) Ethik, (5) Schlüsselvariablen und Linkageverfahren, (6) Datenprüfung/Qualitätssicherung sowie (7) Langfristige Datennutzung für noch festzulegende Fragestellungen. Jede Leitlinie wird ausführlich diskutiert. Zukünftige Aktualisierungen werden wissenschaftliche und datenschutzrechtliche Entwicklungen berücksichtigen

Magnetically trapped atoms for compact atomic clocks

International audienceWe investigate the hyperfine transition of magnetically trapped non-condensed atoms. The two principal frequency shifts, the second order Zeeman effect and the mean field interaction are considered. Analytic models of the mean frequency and its trap induced spread are developed. Comparisons with existing experiments evaluate the role of the atoms' oscillatory motion. The analytic model proves to be equivalent to existing Monte Carlo simulations. The formulae provide a simple tool for optimising the design of a new experiment. Applied to the two-photon transition | F=1, m <SUB> F </SUB>=-1>-->| F=2, m <SUB> F </SUB>=1> in <SUP>87</SUP>Rb and the conditions of a typical atom chip experiment, a line spread as small as 11 mHz is predicted giving a quality factor of 10<SUP>12</SUP>. The system is promising for application in precision instruments such as compact atomic clocks