arXiv subjects

S. Ventura

Publications and source records attributed to S. Ventura.

50 records · Page 3Linked to original sources

arXiv2011

Demonstration and Comparison of Operation of Photomultiplier Tubes at Liquid Argon Temperature

Liquified noble gases are widely used as a target in direct Dark Matter searches. Signals from scintillation in the liquid, following energy deposition from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should be recorded down to very low energies by photosensors suitably designed to operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter searches currently implement photo multiplier tubes for signal read-out. In the last few years PMTs with photocathodes operating down to liquid Argon temperatures (87 K) have been specially developed with increasing Quantum Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod. R11065 with peak QE up to about 35%, has been extensively tested within the R&D program of the WArP Collaboration. During these testes the Hamamatsu PMTs showed superb performance and allowed obtaining a light yield around 7 phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12% range, sufficient for detection of events down to few keVee of energy deposition. This shows that this new type of PMT is suited for experimental applications, in particular for new direct Dark Matter searches with LAr-based experiments.

physics.ins-det↗

arXiv2011

The ICARUS Front-end Preamplifier Working at Liquid Argon Temperature

We describe characteristics and performance of the low-noise front-end preamplifier used in the ICARUS 50-litre liquid Argon Time Projection Chamber installed in the CERN West Area Neutrino Facility during the 1997-98 neutrino runs. The preamplifiers were designed to work immersed in ultra-pure liquid Argon at a temperature of 87K.

physics.ins-det↗

arXiv2011

Underground operation of the ICARUS T600 LAr-TPC: first results

Open questions are still present in fundamental Physics and Cosmology, like the nature of Dark Matter, the matter-antimatter asymmetry and the validity of the particle interaction Standard Model. Addressing these questions requires a new generation of massive particle detectors exploring the subatomic and astrophysical worlds. ICARUS T600 is the first large mass (760 ton) example of a novel detector generation able to combine the imaging capabilities of the old famous "bubble chamber" with an excellent energy measurement in huge electronic detectors. ICARUS T600 now operates at the Gran Sasso underground laboratory, studying cosmic rays, neutrino oscillation and proton decay. Physical potentialities of this novel telescope are presented through few examples of neutrino interactions reconstructed with unprecedented details. Detector design and early operation are also reported.

hep-ex↗

arXiv2010

A hardware implementation of Region-of-Interest selection in LAr-TPC for data reduction and triggering

Large Liquid Argon TPC detectors in the range of multikton mass for neutrino and astroparticle physics require the extraction and treatment of signals from some 105 wires. In order to enlarge the throughtput of the DAQ system an on-line lossless data compression has been realized reducing almost a factor 4 the data flow. Moreover a trigger system based on a new efficient on-line identification algorithm of wire hits was studied, implemented on the actual ICARUS digital read- out boards and fully tested on the ICARINO LAr-TPC facility operated at LNL INFN Laboratory with cosmic-rays. Capability to trigger isolated low energy events down to 1 MeV visible energy was also demonstrated.

physics.ins-det↗

arXiv2010

Free electron lifetime achievements in Liquid Argon Imaging TPC

A key feature for the success of the liquid Argon imaging TPC (LAr-TPC) technology is the industrial purification against electro-negative impurities, especially Oxygen and Nitrogen remnants, which have to be continuously kept at an exceptionally low level by filtering and recirculating liquid Argon. Improved purification techniques have been applied to a 120 liters LAr-TPC test facility in the INFN-LNL laboratory. Through-going muon tracks have been used to determine the free electron lifetime in liquid Argon against electro-negative impurities. The short path length here observed (30 cm) is compensated by the high accuracy in the observation of the specific ionization of cosmic ray muons at sea level as a function of the drift distance. A free electron lifetime of (21.4+7.3-4.3) ms, namely > 15.8 ms at 90 % C.L. has been observed over several weeks under stable conditions, corresponding to a residual Oxygen equivalent of about 15 ppt (part per trillion). At 500 V/cm, the free electron speed is 1.5 m/ms. In a LAr-TPC a free electron lifetime in excess of 15 ms corresponds for instance to an attenuation of less than 15 % after a drift path of 5 m, opening the way to the operation of the LAr-TPC with exceptionally long drift distances.

physics.ins-det↗

arXiv2008

Oxygen contamination in liquid Argon: combined effects on ionization electron charge and scintillation light

A dedicated test of the effects of Oxygen contamination in liquid Argon has been performed at the INFN-Gran Sasso Laboratory (LNGS, Italy) within the WArP R&D program. Two detectors have been used: the WArP 2.3 lt prototype and a small (0.7 lt) dedicated detector, coupled with a system for the injection of controlled amounts of gaseous Oxygen. Purpose of the test with the 0.7 lt detector is to detect the reduction of the long-lived component lifetime of the Argon scintillation light emission at increasing O2 concentration. Data from the WArP prototype are used for determining the behavior of both the ionization electron lifetime and the scintillation long-lived component lifetime during the O2-purification process activated in closed loop during the acquisition run. The electron lifetime measurements allow to infer the O2 content of the Argon and correlate it with the long-lived scintillation lifetime data. The effect of Oxygen contamination on the scintillation light has been thus measured over a wide range of O2 concentration, spanning from about 10^-3 ppm up to about 10 ppm. The rate constant of the light quenching process induced by Oxygen in LAr has been found to be k'(O2)=0.54+-0.03 micros^-1 ppm^-1.

nucl-ex↗

arXiv2008

Effects of Nitrogen contamination in liquid Argon

A dedicated test of the effects of Nitrogen contamination in liquid Argon has been performed at the INFN-Gran Sasso Laboratory (LNGS, Italy) within the WArP R&D program. A detector has been designed and assembled for this specific task and connected to a system for the injection of controlled amounts of gaseous Nitrogen into the liquid Argon. Purpose of the test is to detect the reduction of the Ar scintillation light emission as a function of the amount of the Nitrogen contaminant injected in the Argon volume. A wide concentration range, spanning from about 10^-1 ppm up to about 10^3 ppm, has been explored. Measurements have been done with electrons in the energy range of minimum ionizing particles (gamma-conversion from radioactive sources). Source spectra at different Nitrogen contaminations are analyzed, showing sensitive reduction of the scintillation yield at increasing concentrations. The rate constant of the light quenching process induced by Nitrogen in liquid Ar has been found to be k(N2)=0.11 micros^-1 ppm^-1. Direct PMT signals acquisition at high time resolution by fast Waveform recording allowed to extract with high precision the main characteristics of the scintillation light emission in pure and contaminated LAr. In particular, the decreasing behavior in lifetime and relative amplitude of the slow component is found to be appreciable from O(1 ppm) of Nitrogen concentrations.

nucl-ex↗

arXiv2007

A new, very massive modular Liquid Argon Imaging Chamber to detect low energy off-axis neutrinos from the CNGS beam. (Project MODULAr)

The paper is considering an opportunity for the CERN/GranSasso (CNGS) neutrino complex, concurrent time-wise with T2K and NOvA, to search for theta_13 oscillations and CP violation. Compared with large water Cherenkov (T2K) and fine grained scintillators (NOvA), the LAr-TPC offers a higher detection efficiency and a lower backgrounds, since virtually all channels may be unambiguously recognized. The present proposal, called MODULAr, describes a 20 kt fiducial volume LAr-TPC, following very closely the technology developed for the ICARUS-T60o, and is focused on the following activities, for which we seek an extended international collaboration: (1) the neutrino beam from the CERN 400 GeV proton beam and an optimised horn focussing, eventually with an increased intensity in the framework of the LHC accelerator improvement program; (2) A new experimental area LNGS-B, of at least 50000 m3 at 10 km off-axis from the main Laboratory, eventually upgradable to larger sizes. A location is under consideration at about 1.2 km equivalent water depth; (3) A new LAr Imaging detector of at least 20 kt fiducial mass. Such an increase in the volume over the current ICARUS T600 needs to be carefully considered. It is concluded that a very large mass is best realised with a set of many identical, independent units, each of 5 kt, "cloning" the technology of the T600. Further phases may foresee extensions of MODULAr to meet future physics goals. The experiment might reasonably be operational in about 4/5 years, provided a new hall is excavated in the vicinity of the Gran Sasso Laboratory and adequate funding and participation are made available.

hep-ph↗

arXiv2007

First results from a Dark Matter search with liquid Argon at 87 K in the Gran Sasso Underground Laboratory

A new method of searching for dark matter in the form of weakly interacting massive particles (WIMP) has been developed with the direct detection of the low energy nuclear recoils observed in a massive target (ultimately many tons) of ultra pure Liquid Argon at 87 K. A high selectivity for Argon recoils is achieved by the simultaneous observation of both the VUV scintillation luminescence and of the electron signal surviving columnar recombination, extracted through the liquid-gas boundary by an electric field. First physics results from this method are reported, based on a small 2.3 litre test chamber filled with natural Argon and an accumulated fiducial exposure of about 100 kg x day, supporting the future validity of this method with isotopically purified 40Ar and for a much larger unit presently under construction with correspondingly increased sensitivities.

astro-ph↗

arXiv2006

A novel architecture for DAQ in multi-channel, large volume, long drift Liquid Argon TPC

Recently a large interest has been shown for multi-ton Liquid Argon Time-Projection-Chambers (LAr-TPC). The physics issues are very challenging, but the technical problem of long drifts and adequately long life-time of free electrons are not solved at all so far. Also one should take into account the extremely large number of channels required for such large volumes. In this paper we propose an architecture for DAQ that is based on recent developments in consumer electronics that made available, at a quite interesting price, components aimed to high-resolution delta-sigma conversion. This type of ADC is not at all popular in HEP experiments where normally signals related to events, well defined in time (triggered), should be converted and recorded. In the LAr-TPC however we have to deal rather with waveforms that should be converted and recorded continuously, that is the paramount case of delta-sigma ADC application.

physics.ins-det↗

arXiv2003

Run Control and Monitor System for the CMS Experiment

The Run Control and Monitor System (RCMS) of the CMS experiment is the set of hardware and software components responsible for controlling and monitoring the experiment during data-taking. It provides users with a "virtual counting room", enabling them to operate the experiment and to monitor detector status and data quality from any point in the world. This paper describes the architecture of the RCMS with particular emphasis on its scalability through a distributed collection of nodes arranged in a tree-based hierarchy. The current implementation of the architecture in a prototype RCMS used in test beam setups, detector validations and DAQ demonstrators is documented. A discussion of the key technologies used, including Web Services, and the results of tests performed with a 128-node system are presented.

cs.DC↗

arXiv2003

Using XDAQ in Application Scenarios of the CMS Experiment

XDAQ is a generic data acquisition software environment that emerged from a rich set of of use-cases encountered in the CMS experiment. They cover not the deployment for multiple sub-detectors and the operation of different processing and networking equipment as well as a distributed collaboration of users with different needs. The use of the software in various application scenarios demonstrated the viability of the approach. We discuss two applications, the tracker local DAQ system for front-end commissioning and the muon chamber validation system. The description is completed by a brief overview of XDAQ.

hep-ex↗

arXiv2002

The LXeGRIT Compton Telescope Prototype: Current Status and Future Prospects

LXeGRIT is the first prototype of a novel concept of Compton telescope, based on the complete 3-dimensional reconstruction of the sequence of interactions of individual gamma rays in one position sensitive detector. This balloon-borne telescope consists of an unshielded time projection chamber with an active volume of 400 cm$^2 \times 7$ cm filled with high purity liquid xenon. Four VUV PMTs detect the fast xenon scintillation light signal, providing the event trigger. 124 wires and 4 anodes detect the ionization signals, providing the event spatial coordinates and total energy. In the period 1999 -- 2001, LXeGRIT has been extensively tested both in the laboratory and at balloon altitude, and its response in the MeV region has been thoroughly characterized. Here we summarize some of the results on pre-flight calibration, event reconstruction techniques, and performance during a 27 hour balloon flight on October 4 -- 5. We further present briefly the on-going efforts directed to improve the performance of this prototype towards the requirements for a base module of a next-generation Compton telescope.

astro-ph↗

arXiv2002

On the Background Rate in the LXeGRIT Instrument during the 2000 Balloon Flight

LXeGRIT is the first prototype of a novel Compton telescope for MeV gamma-ray astrophysics based on a Liquid Xenon Time Projection Chamber (LXeTPC), sensitive in the energy band of 0.15-10 MeV. In this homogeneous, 3D position sensitive detector, gamma rays with at least two interactions in the sensitive volume of 2800 cm$^{3}$, are imaged as in a standard Compton telescope. Gamma-rays with a single interaction cannot be imaged and constitute a background which can be easily identified and rejected. Charged particles and localized beta-particles background is also easily suppressed based on the TPC localization capability with millimeter resolution. A measurement of the total gamma-ray background rate in near space conditions and the background rejection power of the LXeTPC was a primary goal of the LXeGRIT balloon flight program. We present here a preliminary analysis addressing this question, based on balloon flight data acquired during the Oct 4-5, 2000 LXeGRIT balloon flight from Ft. Sumner, NM. In this long duration (27 hr) balloon experiment, the LXeGRIT TPC was not surrounded by any gamma-ray or charged particle shield. Single site events and charged particles were mostly rejected on-line at the first and second trigger level. The remaining count rate of single-site \g-ray events, at an average atmospheric depth of 3.2 g cm$^{-2}$, is consistent with that expected from atmospheric and diffuse gamma-ray background, taking into account the instrument mass model and response.

astro-ph↗