M. Geraci

Light response and particle identification with large CsI(TI) crystals coupled to photodiodes

The light response of large CsI(TI) crystals supplied by various companies and coupled to photodiodes has been investigated. Energy resolution measurements and Z = 1 isotopic identification using the two gates method have been performed with in-beam experiments.

Characterization of Nuclear Sources from Neutron-neutron, Proton-proton and Neutron-proton Correlation Functions

Two-neutron, two-proton and neutron–proton correlation functions have been measured simultaneously for the E/A=45 MeV 58 Ni + 27 Al reaction. Calculations from a statistical model have been compared to singles energy spectra as well as to total and gated correlation functions. This imposes very strong constraints on the model parameters. The use of directionally gated correlation functions helps to disentangle space and time information. Values of Gaussian radii, emission lifetimes, initial temperatures, source velocities and flow velocities are extracted. Correlation functions gated on total momentum of the nucleon pairs suggest that more energetic particles are emitted on a fast time scale ( < 100 fm / c ) and that the fraction of pre-equilibrium to equilibrium emission is larger for protons than for neutrons.

Timing performances and edge effects of detectors worked from 6-in. silicon slices

Abstract Prototypes of new passivated implanted planar silicon detectors, obtained for the first time from 6 in. silicon slices, have been tested. The time and energy resolutions have been studied as a function of the type and energy of the detected particles, in order to test the performances of these detectors for time of flight measurements in the Chimera project. Some problems arising from edge effects observed in double-pad detectors have been solved by using a guard ring.

Light charged particle and neutron velocity spectra in coincidence with projectile fragments in the reaction 40Ar(44A MeV)+27Al

Abstract We present a three source analysis of velocity spectra of light charged particles (LCP) and neutrons emitted in the reaction 40 Ar+ 27 Al at 44 A MeV . The light particle (LP) velocity spectra are studied as a function of the detection angle (1.5° θ 3 He, 4 He, d , t ratios and the PLF proton temperature parameter. The characteristics of the PLF sources are derived. Present results are discussed with regards to the degree of thermalization which could be achieved in the PLF and TLF sources.

The enhanced data acquisition system for the 4/spl pi/ detector CHIMERA

CHIMERA is a second generation 4/spl pi/ detector for high resolution light particles and fragments measurements in the field of intermediate energy nuclear physics. An enhanced data acquisition, control and trigger system has been developed to manage the almost 5000 electronic channels of the detector. Data acquisition is based on fast data link (FDL) connection between 9U VME crates. FDL is a highly programmable VME device. It performs data readout and transfer to a destination board VME CPU, FIC8243, running the real time OS9 operating system. Data read and transfer is performed by a fast protocol (sparse data scan) whose performances have been improved introducing the chained block transfer mode (CELT) technique. Data collected by the CPU are broadcasted to the analysis stations for on-line data analysis and storage. All commands from and to VME CPU are sent by socket based network protocols. Complete remote control of the electronic front-end is obtained by a system of client-server applications. A first level event selection and control during readout is assured by a trigger system based on a new VME 9U board (MUSE), fully integrated with the FDL readout system.

The data acquisition and control system for the 4/spl pi/ detector CHIMERA

CHIMERA (Charged Heavy Ions Mass and Energy Resolving Array), a new 4/spl pi/ detector for charged particles is under development at various sites of the Istituto Nazionale di Fisica Nucleare. This paper describes the new data acquisition system built to handle the signals coming out from the detector with a rate up to 1 kHz on almost 5000 electronic channels. The required average throughput for the system is in the order of the 1 MB/s. The used converters allow double-range conversion on 15 bits, in less than 50 /spl mu/s for all the 64 channels. The FDL link connects the different VME 9U crates performing a programmable hardware readout with a rate up to 100 MB/s. It uses a fast hardware protocol (Sparse Data Scan) to read the data buffers and send them to a FIC 8243 CPU board. A FIC 8243 dual-processor board forwards data (through Ethernet) to the analysis station (266 MHz Digital AlphaStation or Sun Sparcstation). A DLT (Digital Linear Tape) unit connected to analysis station is used to store data. The new data acquisition system has been tested under beam conditions at the Laboratorio Nazionale del Sud (Catania, Italy) and at GANIL (Caen, France).

Detector array control and triggering

A commercial DSP-based board installed in a host-PC was employed for the fast, on-line and real-time computation of special algorithms, in order to perform event selection and operate as a 2nd level trigger. Moreover an ad hoc built interface, realized using PLDs with a view to connecting the DSP-board to the ADCs and to the data acquisition system, has been tested in order to evaluate the performances of these programmable devices used as a look-up-table and as a decisional part of a 1st level trigger.

The on-line computational and control system for the 4/spl pi/-detector CHIMERA

A commercial two-DSP-based board is the basic unit of the on-line computational and control system under development for the multidetector CHIMERA. The system design includes a small scale parallel and distributed architecture of PCs, used as both host and user and network interface, and of DSP boards, up to three for each host. The system is able to accomplish the on-beam control of CHIMERA, by means of the on-line computation of special algorithms, instead of using the usual techniques of special pulses to be sent off-beam. The physical data, collected and organized in UDP-packets by the data acquisition system, are read through a 10 Mbit/s Ethernet network. The PC-software, running under Windows NT 4.0, is based on threads and assures the communication and program managing and the result presentation. The DSP-software written in C++ takes care of the communication with the PC and of the computation. The preliminary on beam results for the first three wheels (about 100 telescopes), obtained employing two bi-processor boards located in the PCI-bus of a Pentium MMX PC are also presented.

Characterization of nuclear sources via two-neutron intensity interferometry

The neutron energy spectrum and the two-neutron correlation function have been measured for the E/A = 45 MeV Ni + Al reaction in order to assess the space-time characteristics of the neutron emitting source. When comparing the data to a statistical model,

Plasma effects for heavy ions in implanted silicon detectors

Abstract Plasma effects for heavy ions in implanted silicon detectors have been investigated for different detector characteristics as a function of type and energy of the detected particles. A new approach is presented and used to reproduce the effect of the plasma delay in the timing performances. The results are in good agreement with the present data and with previous measurements found in the literature.