Stabilized lasers for advanced gravitational wave detectors

Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described

Stabilized high-power laser system for the gravitational wave detector advanced LIGO

An ultra-stable, high-power cw Nd:YAG laser system, developed for the ground-based gravitational wave detector Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory), was comprehensively characterized. Laser power, frequency, beam pointing and beam quality were simultaneously stabilized using different active and passive schemes. The output beam, the performance of the stabilization, and the cross-coupling between different stabilization feedback control loops were characterized and found to fulfill most design requirements. The employed stabilization schemes and the achieved performance are of relevance to many high-precision optical experiments

Prototype tests for the ALICE TRD

A Transition Radiation Detector (TRD) has been designed to improve the electron identification and trigger capability of the ALICE experiment at the Large Hadron Collider (LHC) at CERN. We present results from tests of a prototype of the TRD concerning pion rejection for different methods of analysis over a momentum range from 0.7 to 2 GeV/c. We investigate the performance of different radiator types, composed of foils, fibres and foams.Comment: Presented at the IEEE Nuclear Science Symposium and Medical Imaging Conference, Lyon, October 15-20, 2000 (accepted for publication in IEEE TNS), Latex (IEEEtran.cls), 7 pages, 11 eps figure

Conodonts from the “Pelmatozoan Limestone” (Upper Ordovician), northern Sevilla, Ossa-Morena Zone (Spain)

27 páginas, 1 figura, 2 tablas, 2 láminas.[EN] Several limestone levels of the “Caliza de Pelmatozoos” were sampled for conodonts in sections of the Cerrón del Hornillo and Valle synclines. The conodont fauna includes: Amorphognathus ordovicicus, A. aff. ordovicicus, Amorphognathus sp., Amorphognathus? sp., Drepanoistodus cf. suberectus, Drepanoistodus? sp., Hamarodus europaeus, Icriodella cf. superba, Istorinus erectus, Panderodus gracilis, Plectodina tenuis?, Sagittodontina robusta, Scabbardella altipes, Scabbardella sp A., Walliserodus amplissimus? y Walliserodus? sp. This association is attributed to the Amorphognathus ordovicus Zone by the presence of the index species, and to the Sagittodontina-Scabbardella Biofacies of the Mediterranean Province of conodonts by the relative abundance of these two taxa. This fauna is close related to coeval associations from several localities of the Iberian Peninsula, except that of the Malaguide Complex, but the presence of Plectodina and Drepanoistodus suggest possible faunal exchange with Anglo-Baltic faunas.[ES] El estudio para conodontos de numerosos niveles de la “Caliza de Pelmatozoos” en secciones de los sinclinales del Cerrón del Hornillo y del Valle ha permitido identificar los taxones: Amorphognathus ordovicicus, A. aff. ordovicicus, Amorphognathus sp., Amorphognathus? sp., Drepanoistodus cf. suberectus, Drepanoistodus? sp., Hamarodus europaeus, Icriodella cf. superba, Istorinus erectus, Panderodus gracilis, Plectodina tenuis?, Sagittodontina robusta, Scabbardella altipes, Scabbardella sp A., Walliserodus amplissimus? y Walliserodus? sp. Esta asociación, que se adscribe a la Provincia Mediterránea de conodontos, es atribuida a la Zona de Amorphognahus ordovicicus, Kralodvoriense, por la presencia del taxón nominal. Dentro de esta provincia ha sido posible identificar la Biofacies de Sagittodontina-Scabbardella por la abundancia relativa de ambos taxones. Si bien existe una gran similitud entre esta fauna y las de edad equivalente reconocidas en el ámbito de dicha provincia, la presencia de Plectodina y Drepanoistodus sugieren que el área de estudio se encontraba emplazada en latitudes más bajas que el resto de la Península Ibérica, exceptuando la del Complejo Maláguide, y que este hecho favoreció el intercambio faunal con las provincias Británica y Báltica de conodontos.Este trabajo es una contribución al proyecto PATRIORSI (CGL2006-07628/BTE) del Ministerio de Ciencia e Innovación, al proyecto IGCP 503 “Ordovician Palaeogeography and Palaeoclimatology” y Grupo UCM 910231.Peer reviewe

Thermodynamic Properties of the Incommensurate Phase of CuGeO_3

We present high resolution measurements of the specific heat and the thermal expansion of the inorganic spin--Peierls cuprate CuGeO_3 in a magnetic field of 16 Tesla. At the transition from the incommensurate to the uniform phase both quantities show pronounced anomalies, which allow to derive the uniaxial pressure dependencies of the transition temperature. In high magnetic fields the specific heat is dominated by magnetic excitations and follows a T^3 law at low temperatures. The thermal expansion measurements show the occurrence of spontaneous strains along all three lattice constants and yield high resolution measurements of the temperature dependence of the incommensurate structural distortion. The sizes of the spontaneous strains in the incommensurate phase are significantly reduced, but both their anisotropy as well as their temperature dependencies are very similar to those in zero field.Comment: 12 pages (Latex), 4 Figs. (PS), to appear in Phys. Rev. B54 (Vol.21