D. Pascoli

Scintillation efficiency of nuclear recoil in liquid xenon

Abstract We present the results of a test done with a Liquid Xenon (LXe) detector for “Dark Matter” search, exposed to a neutron beam to produce nuclear recoil events simulating those which would be generated by WIMPs elastic scattering. The aim of the experiment was to measure directly the scintillation efficiency of nuclear recoil. The nuclear recoil considered in the test was in the tens of keV range. The ratio of measured visible energy over the true recoil energy was evaluated to be about 20%, in good agreement with the theoretical predictions.

Detection of scintillation light in coincidence with ionizing tracks in a liquid argon time projection chamber

A system to detect light from liquid argon scintillation has been implemented in a small, ICARUS-like, liquid argon time projection chamber. The system, which uses a VUV-sensitive photomultiplier to collect the light, has recorded many ionizing tracks from cosmic-rays in coincidence with scintillation signals. Our measurements demonstrate that scintillation light detection can provide an effective method for absolute time measurement of events and eventually a useful trigger signal

Calibration of BC501A liquid scintillator cells with monochromatic neutron beams

Abstract The recoil proton energy response has been measured by exposing cylindrical cells, filled with BC501A BICRON liquid scintillator, to mono-energetic neutron reference fields. We determine the required calibration parameters and report the detailed procedures for the experimental data handling. A dedicated Monte Carlo simulation of the detector response and efficiency has been performed. It showed good agreement with the measured quantities. The results from this calibration are necessary for a detailed study of the neutron spectrum at the underground Gran Sasso Laboratory, with a neutron detector made of 32 liquid scintillator cells, like those used during the calibration.

Performance of the 10 m 3 ICARUS liquid argon prototype

Abstract We report on the performance of a liquid Argon Time Projection Chamber, operating in a 10 m 3 cryostat. This device built in the framework of the ICARUS T600 programme to serve as a full test facility for the adopted cryogenics and mechanical solutions, was successfully tested in 2000 as the last step before the tests of the first 600 t ICARUS module 1 year later. In a final run at the Gran Sasso Laboratory, whose outcome provides the main subject of this paper, also the readout and imaging capabilities of the installed wire chamber and the overall performance of the detector have been successfully tested.

Daedalus: A hardware signal analyser for Icarus

Icarus detector [1] is a large-volume (400 cm) liquid Argon TPC that requires continuous high rate sampling signal recording on each channel (about 50 000) to produce event images quite similar to the ones from bubble chambers. In order to optimize the memory usage, a signal feature extractor, that commands memory writing only upon signal detection, has been designed in VLSI CMOS. ( 1998 Elsevier Science B.V. All rights reserved.

ARIANNA: the Icarus experiment readout module

Icarus detector is a liquid Argon Time Projection Chamber that requires continuous signal recording for each channel to provide three dimensional images of any ionizing event. A complete drift volume imaging of the next 600 ton module will result in 1.15 Gbit, with a data rate of 1.15 Tbit/s. The collected data can be highly reduced by recognizing Regions Of Interest (ROI) of the signal by means of a custom hit finding unit (DAEDALUS) working pipelined in the data acquisition path. DAEDALUS is an ASIC that implements an algorithm developed for hit detection and proven to be very efficient both on real and on simulated data. Since only ROIs are saved in memory and contiguous regions can be correlated to enhance detector self triggering capability, a high efficiency zero skipping is obtained in real time. A VME board hosting 16 Icarus digital channels has been designed and built as a demonstrator for functionality and performance test. The board, named ARIANNA, and DAEDALUS chip are here presented in detail.

Study of solar neutrinos with the 600 t liquid argon ICARUS detector

Abstract The ICARUS time projection chamber can yield sound information on 8 B solar neutrinos. Owing to the high-energy resolution and the good capability of event reconstruction it can make a contribution to our understanding of neutrino intensities and their energy spectrum. Moreover, the MSW oscillation probability for sterile and active neutrinos can be well studied because both elastic scattering by electrons and absorption reaction on argon nuclei can be measured independently. The main problem in detecting the low-energy neutrino interactions arises from the environmental radioactivity. In the present work we study by Monte Carlo simulation the topology and the rates of the events, induced by neutrinos and background neutrons, in a 470 t (fiducial mass) liquid-argon TPC detector. For neutrino interactions we use the standard solar model BP98 and the recent experimental confirmation of the shell model computation of absorption cross section. The noise is estimated from new data on natural neutron background, collected in the hall C of the Gran Sasso laboratory. It is confirmed that, with a relatively modest neutron shielding and particular off-line event triggers, the weight of spurious events can be made to have little influence on the ICARUS solar neutrino measurement. Indeed, we expect 6 (26) background events per year in the 212 (759) elastic scattering (absorption reaction) sample.

THE MAGIC EXPERIMENT AND ITS FIRST RESULTS

With its diameter of 17m, the MAGIC telescope is the largest Cherenkov detector for gamma ray astrophysics. It is sensitive to photons above an energy of 30 GeV. MAGIC started operations in October 2003 and is currently taking data. This report summarizes its main characteristics, its first results and its potential for physics.

ICARUS 600 ton: A status report

The goal of the ICARUS Project is the installation of a multi-kiloton LAr TPC in the underground Gran Sasso Laboratory. The programme foresees the realization of the detector in a modular way. The first step is the construction of a 600 ton module which is now at an advanced phase. It will be mounted and tested in Pavia in one year and then it will be moved to Gran Sasso for the final operation. The major cryogenic and purification systems and the mechanical components of the detector have been constructed and tested in a 10 m3 prototype. The results of these tests are here summarized.

An interconnect bus to link VME multiprocessor systems and host mainframes

Abstract A high performance bus and modules have been developed to provide fast control and data transfers between the industry standard VME multiprocessor systems and Qbus/Unibus ∗ compatible computers. This concept makes it possible to build complex low cost data acquisition and computing systems with very high performances, as needed in the large high energy particle physics experiments. This paper concentrates on the basic philosophy of the multicrate system and, in particular, of the connection to host computers.