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Abstract: A new detection system KRATTA, Kraków Triple Telescope Array, is presented. This versatile, low threshold, broad energy range system has been built to measure the energy, emission angle, and isotopic composition of light charged reaction products. It consists of 38 independent modules which can be arranged in an arbitrary configuration. A single module, covering actively about 4.5msr of the solid angle at the optimal distance of 40cm from the target, consists of three identical, thick, large area photodiodes, used also for direct detection, and of two CsI(1500ppm Tl) crystals of 2.5 and 12.5cm length, respectively. All the signals are digitally processed. The lower identification threshold, due to the thickness of the first photodiode, has been reduced to about 2.5MeV for protons ( of Si equivalent) by applying a pulse shape analysis. The pulse shape analysis allowed also to decompose the complex signals from the middle photodiode into their ionization and scintillation components and to obtain a satisfactory isotopic resolution with a single readout channel. The upper energy limit for protons is about 260MeV. The whole setup is easily portable. It performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are described using the results of Au+Au collisions at 400MeV/nucleon obtained in this experiment. [Copyright &y& Elsevier]

Abstract: The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around 124La and 107Sn were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable 124Sn projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods. [Copyright &y& Elsevier]

KATANA - the Krakow Array for Triggering with Amplitude discrimiNAtion - has been built and used as a trigger and veto detector for the S π RIT TPC at RIKEN. Its construction allows operating in magnetic field and providing fast response for ionizing particles, giving an approximate forward multiplicity and charge information. Depending on this information, trigger and veto signals are generated. The article presents performance of the detector and details of its construction. A simple phenomenological parametrization of the number of emitted scintillation photons in plastic scintillator is proposed. The effect of the light output deterioration in the plastic scintillator due to the in-beam irradiation is discussed. [ABSTRACT FROM AUTHOR]

A multiplicity trigger detector (MTD) was developed for the S π RIT experiment that aims to probe the high-density symmetry energy via heavy-ion collisions (HICs). The MTD is designed to measure the charged-particle multiplicity in HICs to provide a trigger signal that can be used to select high-multiplicity events induced by central collisions. The MTD consists of two side-walls segmented into 30 plastic scintillation paddles, each equipped with a multi-pixel photon counter. A custom board with EASIROC front-end ASIC is used as readout electronics. A multiplicity logic signal is generated by an on-board FPGA that processes the discriminated signals from EASIROCs. The overall latency of the whole detector system for outputting the trigger is less than 100 ns, including 52 ns of electronics latency for processing the signals. During the measurement of 112 Sn + 124 Sn reactions at an incident energy of 270 MeV/nucleon, the minimum multiplicity threshold of the MTD was set to 4, where the overall trigger efficiency was obtained to be about 39 % for inclusive nuclear reactions. A simulation study with a numerical calculation of HICs found that the central collisions of impact parameters of less than 4 fm can be triggered with a high efficiency of more than 95 % by the experimental trigger condition. [ABSTRACT FROM AUTHOR]

When Time Projection Chambers (TPCs) are used in low to intermediate heavy ion collisions, the mass and momentum range of the emitted particles cover a wide range in energy losses. Many TPC readout electronics currently only have a single gain output with a fixed dynamic range. In a recent set of experiments using the SAMURAI Pion-Reconstruction and Ion-Tracker (S π RIT) TPC, it was important to simultaneously measure relativistic pions and heavy ion tracks from the same collisions. As the ionization from a track's energy loss is collected and multiplied by the anode wires, a distribution of image charges is induced on the TPC read-out pads. If the avalanche on a wire is large enough, the charge collected by pads directly underneath will saturate the readout electronics; pads farther away in the distribution will not be saturated. Using these unsaturated pads and the known pad distribution function, we can estimate the charge on saturated pads, increasing the dynamic range by a factor of 5. [ABSTRACT FROM AUTHOR]