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In this work properties of a vacuum phototriode (VPT) and preamplifier unit designed for the electromagnetic calorimeter of the PANDA experiment being built at FAIR are investigated. With the use of lead tungstate and lanthanium bromide scintillators the VPT properties are studied at low photon energies, from tens of keV in the lanthanium bromide measurements and between 10 MeV and 60 MeV in the lead tungstate measurements. At these energies the noise of the VPT unit can be expected to influence its performance significantly. It is shown that the noise contribution to the measured energy resolution, under optimal conditions, is consistent with a fluctuation of (one standard deviation) approximately 200 electrons at the VPT anode. For a lead tungstate crystal this is equivalent to a noise of 1.2 MeV. For lanthanium bromide this makes it possible to use VPTs for gamma ray spectroscopy above a few hundreds of keV without noticeable effects on the energy resolution compared to measurements with a standard photomultiplier. [ABSTRACT FROM AUTHOR]

Abstract: The response of a matrix of 25 lead tungstate (PWO) scintillator detectors, operated at −25°C, to photons in the range 13MeV–64MeV has been measured at the tagged-photon facility at MAX-lab, Lund. The tapered PWO crystals, each with a length of 200mm and a cross-section of 24.4×24.4mm2 in the front end, read out by 19mm photomultiplier tubes, were arranged in a 5×5 matrix. The response was measured for photons directed towards the centre of the central crystal as well as for photons directed towards the corner of the central crystal, where four crystals meet. The obtained energy resolution surpasses what has been published so far and is close to the limit given by Poisson statistics and escaped energy. For photons directed towards the centre(corner) of the central crystal the relative energy resolution, defined as (FWHM/2.35), decreases from 7.3%(11.0%) at to 3.3%(3.6%) at . The reconstructed point of impact of a photon in this energy range is determined with an uncertainty (one standard deviation) of 7.3±0.1mm. [Copyright &y& Elsevier]

Abstract: The use of High Purity Germanium detectors (HPGe) has been planned in some future experiments of hadronic physics. The crystals will be located close to large spectrometers where the magnetic fringing field will not be negligible and their performances might change. Moreover high precision is required in these experiments. The contribution of magnetic field presence and long term measurements is unique. In this paper the results of systematic measurements of the resolution, stability and efficiency of a crystal operating inside a magnetic field of 0.8T, using radioactive sources in the energy range from 0.08 to 1.33MeV, are reported. The measurements have been repeated during several months in order to test if any permanent damage occurred. The resolution at 1.117 and 1.332MeV gamma-rays from a 60Co source has been measured at different magnetic fields in the range of 0–0.8T and the results are compared with the previous data. [Copyright &y& Elsevier]

Abstract: Experimental data from the reaction close to threshold have been used to investigate time-dependent properties of the WASA pellet target and the stored beam of 892.8MeV protons in the CELSIUS accelerator. The detection of 3He ions in solid-state detectors provides an excellent almost background free trigger for production. Pellet interactions with the surrounding material and with the beam lead to evaporation of deuterium gas into the beam pipe. Approximately 30% of the registered decay events are due to interactions in deuterium gas outside the pellets. Due to beam–target interaction the beam is transversely heated and appears to acquire a component of a slightly lower energy. [Copyright &y& Elsevier]

A digital algorithm for real-time feature extraction, i.e. determination of pulse amplitude and timing, has been developed for the forward-spectrometer electromagnetic calorimeter in the PANDA experiment. The algorithm, which is based on the well known optimal-filter algorithm, has been designed to allow reconstruction of pile-up signals in real time and to work in a free-running DAQ system such as PANDA. To benchmark the algorithm, a Geant4-based Monte Carlo model of photon interactions in the calorimeter has been developed to generate realistic detector signals which were used as inputs to a VHDL simulation of the algorithm. The results of this simulation study show that the developed algorithm improves the time resolution by almost 50% compared to a conventional linear constant fraction discriminator algorithm. For the PANDA calorimeter, this results in a time resolution close to 100 ps/ GeV per detector element at high energies. The algorithm allows reconstruction of the amplitude and timing of pile-up pulses separated by as little as 30 ns with good efficiency, fulfilling the PANDA requirements. [ABSTRACT FROM AUTHOR]