The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can ...be used to address hotly debated problems in nuclear astrophysics, such as the accurate measurements of the cross sections of the 24Mg(γ,α)20Ne reaction, that is fundamental to determine the effective rate of 28Si destruction right before the core collapse and the subsequent supernova explosion. For this purpose, a silicon strip detector array (named ELISSA, acronym for Extreme Light Infrastructure Silicon Strip Array) will be realized in a common effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS), in order to measure excitation functions and angular distributions over a wide energy and angular range. A prototype of ELISSA was built and tested at INFN-LNS in Catania (Italy) with the support of ELI-NP. In this occasion, we have carried out experiments with alpha sources and with a 11 MeV 7Li beam. Thanks to our approach, the first results of those tests show up a very good energy resolution (better than 1%) and very good position resolution, of the order of 1 mm. Moreover, a threshold of 150 keV can be easily achieved with no cooling.
A novel technique for laser produced plasmas (LPPs) investigation is proposed. It combines high time resolved measurements using a compact Langmuir probe (LP) with simulated data obtained with a ...numerical model designated as hybrid laser ablation simulations (HYBLAS). The code simulates charged particle collection with what we will refer to as a virtual LP. With the use of an appropriate experimental setup and with a MATLAB software, which analyzes the experimental I-V curves, LPPs can be investigated properly even if the probe is placed very close to the target surface. The method permits to study the plume expansion with a high temporal resolution and to correctly estimate the self-generated Coulomb electric field inside the plume. It permits to detect the inner structure of the first upcoming expanding plasma. HYBLAS is able to describe the plume expansion at relatively low power densities if the initial conditions are set properly. A direct comparison of the theoretical data with the experimental ones realized on different metal targets shows that this method is able to predict properly the overall plasma expansion in the nanosecond laser pulse duration regime. The virtual probe method was moreover tested by comparing the numerical results with the numerical code called MULTI.
We have built and tested a computational unit for on-line processing of special algorithms to be embedded in the central processing unit VERSAmodule Eurocard (CPU VME)-crate of the CHIMERA data ...acquisition system. The computational unit consists of a number of VME digital signal processor (DSP)-based commercial boards delivering 720 MFlops/board.
In nuclear physics at intermediate energies, the use of multidetector arrays consisting of thousands of detectors is customary. This paper presents a novel approach to the automatic classification of ...data collected by the 4 pi detector CHIMERA, constituted by 1192 telescopes of a thin silicon transparent detector coupled to a thick CsI(Tl) scintillator. The method is based on spatial density data processing and produces frequency distributions of the most significant physical parameters. These one-dimensional spectra can be more easily analyzed than the standard two-dimensional scatter plots. With respect to manual or semiautomatic procedures, presently used for data analysis, our method offers the advantages of drastic time reduction and unbiased criteria for cluster identification. The proposed method can be successfully used in both off-line data analysis and multidetector stability control
This paper is concerned with the automatic analysis of data coming from the multidetector array CHIMERA, used in nuclear physics at intermediate energies. Each of Chimera's detection cells is a ...telescope made of a /spl Delta/E silicon detector and a CsI(Tl) crystal, thick enough to stop all the charged light particles. The signals produced in the CsI(Tl) scintillators can be subdivided into two components-fast and slow. These data are collected in the form of bi-dimensional matrices (Fast-Slow matrices), particularly important for light particle identification. The proposed approach consists in applying image processing techniques. In particular, Grossberg's pre-attentive neural networks are used as a first step in order to isolate the regions of physical interest in the matrices and to roughly identify the directions depicted by the most intense lines; a successive step of filtering based on Markov random fields is then performed.
The CHIMERA 4/spl pi/ detector trigger system is described. The trigger decisions are based on a combination of geometrical multiplicity of detected particles and other logic signals. The trigger can ...manage the buffer memory of the used analog to digital converters. This allows performance of parallel data conversion and readout and substantial improvement of the acquisition system dead-time performances. The trigger module generates all the necessary gate signals for the converters and the control signals necessary to synchronize the readout. It also allows the remote control of the whole system.
In this paper we propose a novel technique for LPP-Laser Produced Plasmas investigation, combining high time resolved measurements using compact Langmuir Probes with the output of a theoretical model ...called HYBLAS developed on purpose, which is able to simulate the charged particles collected by a so-called virtual probe. It will be shown that with an appropriate experimental set-up and with the use of a Matlab software able to accurately analyze the experimental I-V curves, laser plasmas can be investigated properly even if the probe is placed very close to the target surface. This permits not only to study the plume expansion with a high temporal resolution, but also to estimate correctly the self-generated coulomb electric field inside the plume and to detect the inner structure of the the first upcoming expanding plasma. HYBLAS is able to predict and describe the plume expansion at relatively low power densities and is a powerful method to compare directly the experimental current signals with the numerical results if the initial conditions are setted properly. A direct comparison of the theoretical data with the experimental ones realized on different metal targets shows that our method is able to predict properly the overall plasma expansion in the nanosecond laser pulse duration regime. The virtual probe method was moreover tested by comparing the numerical results with another numerical code called MULTI, which simulate the expansion by combining the hydrodynamics equations to a multigroup method in order to include the radiation transport.
Dysfunctions of dopaminergic homeostasis leading to either low or high dopamine (DA) levels are causally linked to Parkinson's disease, schizophrenia, and addiction. Major sites of DA synthesis are ...the mesencephalic neurons originating in the substantia nigra and ventral tegmental area; these structures send major projections to the dorsal striatum (DSt) and nucleus accumbens (NAcc), respectively. DA finely tunes its own synthesis and release by activating DA D2 receptors (D2R). To date, this critical D2R-dependent function was thought to be solely due to activation of D2Rs on dopaminergic neurons (D2 autoreceptors); instead, using site-specific D2R knock-out mice, we uncover that D2 heteroreceptors located on non-DAergic medium spiny neurons participate in the control of DA levels. This D2 heteroreceptor-mediated mechanism is more efficient in the DSt than in NAcc, indicating that D2R signaling differentially regulates mesolimbic- versus nigrostriatal-mediated functions. This study reveals previously unappreciated control of DA signaling, shedding new light on region-specific regulation of DA-mediated effects.
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