122960849
Gamma irradiation of semitransparent amorphous silicon sensors
Abstract Semitransparent amorphous silicon sensors are the key elements for laser light 2D position reconstruction in the CMS alignment system. Some of them have to work in very extreme radiation environment. We have irradiated with gammas, up to 10 MRad, two different sensors and measured their change in performance.
26141595
First investigation of a novel 2D position-sensitive semiconductor detector concept
This paper presents a first study of the performance of a novel 2D position-sensitive microstrip detector, where the resistive charge division method was implemented by replacing the metallic electrodes with resistive electrodes made of polycrystalline silicon. A characterization of two proof-of-concept prototypes with different values of the electrode resistivity was carried out using a pulsed Near Infra-Red laser. The experimental data were compared with the electrical simulation of the sensor equivalent circuit coupled to simple electronics readout circuits. The good agreement between experimental and simulation results establishes the soundness of resistive charge division method in silicon microstrip sensors and validates the developed simulation as a tool for the optimization of future sensor prototypes. Spatial resolution in the strip length direction depends on the ionizing event position. The average value obtained from the protype analysis is close to 1.2% of the strip length for a 6 MIP signal.
123257317
PERFORMANCE TEST OF THE CMS LINK ALIGNMENT SYSTEM
Abstract A first global test of the CMS Alignment System was performed at the I4 hall of the CERN ISR tunnel. Positions of the network, reproducing a set of points in the CMS detector monitored by the Link System, were reconstructed and compared to survey measurements. Spatial and angular reconstruction precisions reached in the present experimental set-up are already close to the CMS requirements.
139842026
Test Results of the Semi-transparent Amorphous Silicon Sensors for the Link System of CMS
125314523
PROPOSAL FOR A TEST OF AN IMPACT PARAMETER TRIGGER AIMED AT A HIGH STATISTICS HEAVY QUARK STUDY
123499216
New silicon microstrip detectors optimized for tracker alignment
The resolution of tracking systems based on layers of silicon microstrips is comparable to the stability of the structures on which they are mounted. Environmental changes during operation will misalign the modules out of their nominal positions. A straight laser beam that sequentially traverses consecutive layers of microstrips can be used as an artificial track to align them. For such a laser track to reach the last sensor, high transmittance of microstrips to infrared (IR) light is needed. We have simulated the passage of a coherent beam of light through a microstrip detector and identified the minimum set of changes to the design that boosts its transmittance. The simulation has been validated against real microstrip detector samples.
119477379
The weak-line T Tauri star V410Tau I. A multi-wavelength study of variability
We present the results of an intensive coordinated monitoring campaign in the optical and X-ray wavelength ranges of the low-mass, pre-main sequence star V410Tau carried out with the aim to study the relation between various indicators for magnetic activity that probe emission from different atmospheric layers: optical photometric star spot (rotation) cycle, chromospheric Halpha emission, and coronal X-rays. Two X-ray pointings were carried out with the Chandra satellite simultaneously with the optical observations, and centered near the maximum and minimum levels of the optical lightcurve. A relation of their different count levels to the rotation period of the dominating spot is not confirmed by a third Chandra observation carried out some months later, during another minimum of the 1.87d cycle. Similarly we find no indications for a correlation of the Halpha emission with the spots' rotational phase. The extraordinary stability of the largest spot is confirmed by long-term photometric and radial velocity measurements. Joining our optical photometry with previous data we provide a new estimate for the dominant periodicity of V410Tau. This updated value removes systematic offsets of the time of minimum observed in data taken over the last decade. Furthermore, the combination of the new data with published measurements taken during the last decade allows us to examine long-term changes in the mean light level of the photometry of V410Tau. A variation on the timescale of 5.4yr is suggested. Assuming that this behavior is truely cyclic V410Tau is the first pre-main sequence star on which an activity cycle is detected.
18240213
VSOP: The Variable Star One-shot Project ⋆ I. Project presentation and first data release
Context. About 500 new variable stars enter the General Catalogue of Variable Stars (GCVS) every year. Most of them however lack spectroscopic observations, which remains critical for a correct assignement of the variability type and for the understanding of the object. Aims. The Variable Star One-shot Project (VSOP) is aimed at (1) providing the variability type and spectral type of all unstudied variable stars, (2) process, publish, and make the data available as automatically as possible, and (3) generate serendipitous discoveries. This first paper describes the project itself, the acquisition of the data, the dataflow, the spectroscopic analysis and the on-line availability of the fully calibrated and reduced data. We also present the results on the 221 stars observed during the first semester of the project. Methods. We used the high-resolution echelle spectrographs HARPS and FEROS in the ESO La Silla Observatory (Chile) to survey known variable stars. Once reduced by the dedicated pipelines, the radial velocities are determined from cross correlation with synthetic template spectra, and the spectral types are determined by an automatic minimum distance matching to synthetic spectra, with traditional manual spectral typing cross-checks. The variability types are determined by manually evaluating the available light curves and the spectroscopy. In the future, a new automatic classifier, currently being developed by members of the VSOP team, based on these spectroscopic data and on the photometric classifier developed for the COROT and Gaia space missions, will be used. Results. We confirm or revise spectral types of 221 variable stars from the GCVS. We identify 26 previously unknown multiple systems, among them several visual binaries with spectroscopic binary individual components. We present new individual results for the multiple systems V349 Vel and BC Gru, for the composite spectrum star V4385 Sgr, for the T Tauri star V1045 Sco, and for DM Boo which we re-classify as a BY Draconis variable. The complete data release can be accessed via the VSOP web site.
117452043
A direct imaging search for wide (sub)stellar companions around rad-vel planet host stars
We present an overview of our ongoing systematic search for wide (sub)stellar companions around the stars known to host rad-vel planets. By using a relatively large field of view and going very deep our survey can find all directly detectable stellar and brown dwarf companions (m>40 Mjup) within a 1000 AU orbit.
118504351
Multi-wavelength study of the disk around the very low-mass star Par-Lup3-4
Context. Par-Lup3-4 is a very low-mass star (spectral type M5) in the Lupus III star-forming region. It shows spectroscopic evidence of accretion and mass-loss. In the optical and near-infrared, the object is underluminous by ≈4 mag when compared to objects of similar mass in the same association. Aims. The aim of this work is to characterize the circumstellar environment of Par-Lup3-4 to better understand the origin of its underluminosity. Methods. We have analyzed high angular resolution near-IR observations and searched for extended emission from a disk and/or an envelope. We have studied the spectral energy distribution (SED) of the target from the optical to the sub-millimeter regime, and compared it to a grid of radiative transfer models of circumstellar disks. Since the target is strongly variable, we modeled two different near-infrared datasets. Results. The SED of Par-Lup3-4 resembles that of objects with edge-on disks seen in scattered light, that is, a double peaked-SED and a dip at ∼10 μm. The diffraction-limited infrared observations do not show obvious extended emission, allowing us to put an upper limit of ∼20 AU to the disk outer radius. Par-Lup3-4 is probably in a Class II (rather than a Class I) evolutionary stage, which is indicated by the lack of extended emission together with the non detection of a strong 9.8 μm silicate in absorption. This last feature is indeed seen in emission. We fitted the whole SED of Par-Lup3-4 with a single disk model. Our modeling predicts a disk inclination of 81 ◦ ± 6 ◦ , which agrees well with previous estimates, and provides a natural explanation for the under-luminosity of the target. The detection of the silicate feature in emission at such a high inclination might be related to a more complex disk structure (e.g. asymmetries, inhomogeneities) than the one assumed here. Our analysis allows us to put constraints on the disk inner radius, Rin ≤ 0.05 AU, which is very close to the dust sublimation radius, and the maximum size of the dust grains, amax ≥ 10 μm, which indicates that dust processing has already taken place in Par-Lup3-4. Some of the derived disk parameters vary depending on the modeled near-infrared data-set, which emphasizes the importance of taking variability into account when modeling the SED of young stellar objects.
17255900
CONSTRAINTS ON A SECOND PLANET IN THE WASP-3 SYSTEM*
There have been previous hints that the transiting planet WASP-3b is accompanied by a second planet in a nearby orbit, based on small deviations from strict periodicity of the observed transits. Here we present 17 precise radial velocity (RV) measurements and 32 transit light curves that were acquired between 2009 and 2011. These data were used to refine the parameters of the host star and transiting planet. This has resulted in reduced uncertainties for the radii and masses of the star and planet. The RV data and the transit times show no evidence for an additional planet in the system. Therefore, we have determined the upper limit on the mass of any hypothetical second planet, as a function of its orbital period.