F. Rizzo

Particle identification via pulse shape analysis for large-area silicon detectors of the CHIMERA array

Mass and atomic-number identification (ID) of reaction products is a fundamental requirement of any nuclear reaction study. An effective particle-ID method is demonstrated, based on pulse shape analysis/discrimination (PSD) applied to large-area, single-element silicon detectors. This technique uses commercial electronic modules and achieves atomic number resolution rivaling that typically obtained with multi-element (/spl Delta/E-E) detector telescopes. The method is applied to the CHIMERA detector system without compromising its time-of-flight (TOF) resolution. In-beam tests of the PSD method have been performed with large-area, 300-/spl mu/m thick CHIMERA silicon detectors, measuring particles from the /sup 19/F+/sup 12/C reaction at Tandem energies. Performance of a simple PSD set up is discussed, for front and rear particle injection.

Digital Signal Processing for Mass Identification in a

CHIMERA is the only 4 pi-multidetector, used in intermediate nuclear physics experiments, able to perform mass identification of the reaction products. To this purpose, it employs time of flight measurements done with traditional time to digital converters. In order to improve the resolution in mass identification, we have applied digital signal processing to time of flight measurements. This paper presents the methodology for data analysis, the adopted algorithms and the results obtained at different sampling frequencies (mass identification up to A = 33 for the reaction products produced by a 20.5 MeV/u 20Ne beam on 27Al target).

4\pi

Abstract An apparatus for detecting light and heavy fragments, in coincidence with γ-rays is described. Its use is foreseen for studying heavy ion complete and incomplete fusion reactions at low and intermediate energy. The ΔE-E and TOF techniques are used for charged particle identification at small angles using a combination of Si strip detectors and CsI(Tl) crystals. The γ-ray detection is performed by using a coverage of 9 clusters, each consisting of 7 BaF2 crystals, similar to the TAPS configuration, resulting in a large solid angle and a high granularity. We report on recent results about the charged particle discrimination and the time and energy resolution for the whole detector. Initial tests were performed using 12C, 19F and 28Si beams accelerated by the 15 MV tandem of the Laboratorio Nazionale del Sud in Catania.

-Detector, Using Time of Flight Measurement

Odd-even staggering effects on charge distributions are investigated for fragments produced in semiperipheral and central collisions of 112Sn+58Ni at 35 MeV/nucleon. For fragments with Z<16 one observes a clear overproduction of even charges, which decreases for heavier fragments. In peripheral collisions staggering effects persist up to Z about 40. For light fragments, staggering appears to be substantially independent of the centrality of the collisions, suggesting that it is mainly related to the last few steps in the decay of hot nuclei.

TRASMA, a detector for γ-charged particle coincidences

The digital pulse shape data acquisition (DAQ) system used by the large area telescopes of the 4pi-multidetector CHIMERA requires transferring large amount of data to the computer. This is necessary so that the same information can be extracted from the detector pulses as in previous analog based systems. To overcome this problem, we have used a sampling ADC-board equipped with two TigerSHARC digital signal processors. The board receives the data and reconstructs the event parameters online. The data volume is significantly reduced by transmitting to the DAQ only the reconstructed event parameters

Persistence of odd-even staggering in charged fragment yields from the

The capability of digital pulse shape technique to acquire data from CHIMERA detection cells (Si-CsI(Tl) telescopes) has been evidenced in our previous works. /spl Delta/E-E scatter plots to obtain charge identification for the detected reaction products and fast-slow scatter plots from the CsI(Tl) light pulses for light charged product identification have been carefully reconstructed. We have now applied this technique to the charge discrimination of the products which stop in the silicon detectors, by using large area totally depleted CHIMERA silicon detectors (300 /spl mu/m thick, 5/spl times/5 cm/sup 2/ area) in reverse mount. In preliminary tests full charge identification for the reaction products up to Z=11 have been obtained for products both crossing the silicon detector (/spl Delta/E-E technique) and stopping in it, using a 21.1 MeV/u /sup 20/Ne beam at the LNS superconducting cyclotron in Catania. The quality of the obtained results clearly indicates that the digital signal processing approach is able to give excellent results in this application, too.

^{112}Sn + ^{58}Ni

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).

collision at 35 MeV/nucleon

The dependence of the CsI(Tl) scintillation time constants and intensities on the particle ionization profile is at the basis of the Charge and Mass identification technique for Light Charged Products in Intermediate Energy Nuclear Physics multi-detector arrays. The possibility of storing the digitized waveforms in true beam experiments allows performing further offline analyses and makes available a data set related to the interaction of different particle types in a wide energy range.

On-Board Digital Signal Processing for 4

The on-line computation of special algorithms, as power-law for particle identification in nuclear physics, is a basic problem requiring real-time computational resources that have to fit time constraints, due to the randomness of nuclear events, and assure correctness. Present work concentrates on the possibility to use a low cost commercially available DSP boards for this purpose. The used DSP board computes in real-time transcendental functions expanded in Chebychev polynomial series with assembler routines ad hoc written, in order to perform the identification of the charged particles emitted in nuclear reactions. In particular a presentation of an emulation framework is described where Assembler DSP algorithms are tested at full speed, while input and output are tested at low velocity, by using two host PC, simulating peripherals for the I/O data.

\pi

The present paper concerns the study of reactions induced by radioactive beams of halo and weakly bound nuclei at energies around and above the Coulomb barrier. The results obtained for the reaction induced by the halo nucleus 6He on 64Zn have been compared with the results for the reaction induced by 4He on the same target. The results of the reaction induced by the weakly bound unstable 13N on the weakly bound 9Be have been compared with those for the reaction 10B + 12C.