Minimizing the Dick Effect in an Optical Lattice Clock

We discuss the minimization of the Dick effect in an optical lattice clock. We show that optimizing the time sequence of operation of the clock can lead to a significant reduction of the clock stability degradation by the frequency noise of the interrogation laser. By using a non-destructive detection of the atoms, we are able to recycle most of the atoms between cycles and consequently to strongly reduce the time spent capturing the atoms in each cycle. With optimized parameters, we expect a fractional Allan deviation better than 2E-16$\tau^{-1/2}$ for the lattice clock.Comment: 6 pages, 10 figures. Submitted to IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Contro

CPN Tools 4: Multi-formalism and Extensibility

Abstract. CPN Tools is an advanced tool for editing, simulating, and analyzing colored Petri nets. This paper discusses the fourth major re-lease of the tool, which makes it simple to use the tool for ordinary Petri nets, including adding inhibitor and reset arcs, and PNML export. This version also supports declarative modeling using constraints, and adds an extension framework making it easy for third parties to extend CPN Tools using Java.

The Laser of the ALICE Time Projection Chamber

The large TPC ($95 \mathrm{m}^3$) of the ALICE detector at the CERN LHC was commissioned in summer 2006. The first tracks were observed both from the cosmic ray muons and from the laser rays injected into the TPC. In this article the basic principles of operating the $266 \mathrm{nm}$ lasers are presented, showing the installation and adjustment of the optical system and describing the control system. To generate the laser tracks, a wide laser beam is split into several hundred narrow beams by fixed micro-mirrors at stable and known positions throughout the TPC. In the drift volume, these narrow beams generate straight tracks at many angles. Here we describe the generation of the first tracks and compare them with simulations.Comment: QM06 poster proceedings, 6 pages, 4 figure

Ultrastable lasers based on vibration insensitive cavities

We present two ultra-stable lasers based on two vibration insensitive cavity designs, one with vertical optical axis geometry, the other horizontal. Ultra-stable cavities are constructed with fused silica mirror substrates, shown to decrease the thermal noise limit, in order to improve the frequency stability over previous designs. Vibration sensitivity components measured are equal to or better than 1.5e-11 per m.s^-2 for each spatial direction, which shows significant improvement over previous studies. We have tested the very low dependence on the position of the cavity support points, in order to establish that our designs eliminate the need for fine tuning to achieve extremely low vibration sensitivity. Relative frequency measurements show that at least one of the stabilized lasers has a stability better than 5.6e-16 at 1 second, which is the best result obtained for this length of cavity.Comment: 8 pages 12 figure

INTEGRAL observations of the Large Magellanic Cloud region

We present the preliminary results of the INTEGRAL survey of the Large Magellanic Cloud. The observations have been carried out in January 2003 (about 10^6 s) and January 2004 (about 4x10^5 s). Here we concentrate on the bright sources LMC X-1, LMC X-2, LMC X-3 located in our satellite galaxy, and on the serendipitous detections of the Galactic Low Mass X-ray Binary EXO 0748-676 and of the Seyfert 2 galaxy IRAS 04575-7537.Comment: 4 pages, 7 figures. To be published in the Proceedings of the 5th INTEGRAL Workshop: "The INTEGRAL Universe", February 16-20, 2004, Munic

Ultraviolet Absorption Spectra at Reduced Temperatures. I. Principles and Methods

Low temperature absorption and fluorescence spectra of solids, liquids, and solutions often reveal increased spectral detail of use in analytical procedures and molecular structure studies. Nevertheless, while qualitative observations of the influence of liquid air temperatures upon optical properties were undertaken very early, investigations of the absorption and fluorescence of organic compounds at the temperature of liquid nitrogen (-195.6°; 77.4 °K.) and below have appeared only sporadically. Because of the potential usefulness of the technique we have undertaken a systematic study of the low temperature spectra of substances of biochemical interest. The present paper discusses the methods employed; subsequent papers will deal with the experimental results. In this work, we have emphasized the wave-length location of absorption bands and the accurate determination of relative optical densities rather than precision in the determination of absolute optical densities, thus permitting the use of simpler methods than would otherwise be necessary

An Infrastructure for Cost-Effective Testing of Operational Support Algorithms Based on Colored Petri Nets

Operational support is a specific type of process mining that assists users while process instances are being executed. Examples are predicting the remaining processing time of a running insurance claim and recommending the action that minimizes the treatment costs of a particular patient. Whereas it is easy to evaluate prediction techniques using cross validation, the evaluation of recommendation techniques is challenging as the recommender influences the execution of the process. It is therefore impossible to simply use historic event data. Therefore, we present an approach where we use a colored Petri net model of user behavior to drive a real workflow system and real implementations of operational support, thereby providing a way of evaluating algorithms for operational support before implementation and a costly test using real users. In this paper, we evaluate algorithms for operational support using different user models. We have implemented our approach using Access/CPN 2.0