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The Joint European Torus (JET) gamma-ray camera has been recently upgraded with the installation of new gamma-ray detectors, based on LaBr3(Ce) scintillation crystals, which add spectroscopic capability to the existing system allowing measurements with good energy resolution (5% at 0.622 MeV), a dynamic range from hundreds of keV up to about 30 MeV, and high counting rate capabilities of MCps. First gamma-ray measurements during the C38 campaign of the JET have been successfully carried out, in particular, in D-3He plasmas from three-ion ion cyclotron resonance heating experiments, where the detection of 16.4 MeV γ-rays from D + 3He → γ + 5Li reactions with the gamma-ray camera upgrade allowed determining the spatial profile of alpha particles born in D + 3He fusion reactions.

Bu çalışma, 01-03 Haziran 2016 tarihleri arasında İstanbul[Türkiye]’da düzenlenen 6. Congress and Exhibition on International Advances in Applied Physics and Materials Science (APMAS)’da bildiri olarak sunulmuştur. In addition to PWO and CsI(Tl) crystals, cerium doped LYSO crystal is considered for the electromagnetic calorimeter part of the Turkish Accelerator Center Particle Factory (TAC-PF) detector, because of its high light yield, fast decay time and good radiation hardness. In this work, LYSO crystals arranged in 3 x 3 and 5 x 5 matrices have been simulated against photons in the energy range between 50 MeV and 2 GeV, using Geant4 simulation code. Energy resolutions have been estimated considering the contribution of photoelectron statistics coming from the avalanche and PIN photodiodes.

Silicon Carbide (SiC) is a relatively new entry in the world of solid-state detectors. Although SiC response to neutrons is more complex than the one obtained with diamonds, the measured energy resolution (FWHM/ E d 4 % ) makes SiC an interesting alternative to diamond and silicon detectors for fast neutrons. The results obtained from the measurements of the response of a 100 μ m thick SiC detector to neutrons in the energy range between 3 and 20 MeV at the n_TOF spallation source at CERN are presented in this paper. By selecting the neutron energy by means of the time of flight, the detector response to quasi-mono-energetic neutrons was measured. The main neutron-induced nuclear reactions were identified in the measured pulse height spectrum. Detection efficiency as a function of neutron energy was measured and interpreted based on available neutron cross section and by making use of Monte Carlo simulations.

We present limits on spin-independent dark matter-nucleon interactions using a $10.6$ $\mathrm{g}$ Si athermal phonon detector with a baseline energy resolution of $\sigma_E=3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.19}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from $93$ to $140$ $\mathrm{MeV}/c^2$, with a raw exposure of $9.9$ $\mathrm{g}\cdot\mathrm{d}$ acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches., Comment: 7 pages, 4 figures, this version includes ancillary files from official data release

Given the good performances in terms of geometrical acceptance and energy resolution, calorimeters are the best suited detectors to measure high energy cosmic rays directly in space. However, in order to exploit this potential, the design of calorimeters must be carefully optimized to take into account all limitations related to space missions, due mainly to the mass of the experimental apparatus. CaloCube is a three years R&D project, approved and financed by INFN in 2014, aiming to optimize the design of a space-borne calorimeter by the use of a cubic, homogeneous and isotropic geometry. In order to maximize detector performances with respect to the total mass of the apparatus, comparative studies on different scintillating materials, different sizes of crystals and different spacings among them have been performed making use of Monte Carlo simulations. In parallel to this activity, several prototypes instrumented with CsI:Tl cubic crystals have been constructed and tested with particle beams (muons, electrons, protons and ions). Both simulations and prototypes showed that the CaloCube design leads to a good particle energy resolution (< 2% for electromagnetic showers, < 40% for hadronic showers) and a good effective geometric factor (> 3:5 m2 sr for electromagnetic showers, > 2:5 m2 sr for hadronic showers). Thanks to these performances, in 5 years of operation it would be possible to measure the ux of electrons+positrons up to some tens of TeV and the uxes of protons and nuclei up to some units of PeV/nucleon, hence extending these measurements by at least one order of magnitude in energy compared to the experiments currently operating in space.

In this paper we present the measurement of the response of 50 $\mu$m thin diamond detectors to 14 MeV neutrons. Such neutrons are produced in fusion reactors and are of particular interest for ITER neutron diagnostics. Among semiconductor detectors diamond has properties most appropriate for harsh radiation and temperature conditions of a fusion reactor. However, 300-500 $\mu$m thick diamond detectors suffer significant radiation damage already at neutron fluences of the order of $10^{14}$ n/cm$^2$. It is expected that a 50 $\mu$m thick diamond will withstand a fluence of $>10^{16}$ n/cm$^2$. We tested two 50 $\mu$m thick single crystal CVD diamonds, stacked to form a "sandwich" detector for coincidence measurements. The detector measured the conversion of 14 MeV neutrons, impinging on one diamond, into $\alpha$ particles which were detected in the second diamond in coincidence with nuclear recoil. For $^{12}C(n,\alpha)^{9}Be$ reaction the total energy deposited in the detector gives access to the initial neutron energy value. The measured 14 MeV neutron detection sensitivity through this reaction by a detector of effective area 3$\times$3 mm$^2$ was $5\times 10^{-7}$ counts cm$^2$/n. This value is in good agreement with Geant4 simulations. The intrinsic energy resolution of the detector was found to be 240 keV FWHM which adds only 10 % to ITER's 14 MeV neutron energy spread., Comment: submitted in NIM A

In this work, we describe the solution developed by the gamma ray camera upgrade enhancement project to improve the spectroscopic properties of the existing JET γ-ray camera. Aim of the project is to enable gamma-ray spectroscopy in JET deuterium-tritium plasmas. A dedicated pilot spectrometer based on a LaBr3 crystal coupled to a silicon photo-multiplier has been developed. A proper pole zero cancellation network able to shorten the output signal to a length of 120 ns has been implemented allowing for spectroscopy at MHz count rates. The system has been characterized in the laboratory and shows an energy resolution of 5.5% at Eγ = 0.662 MeV, which extrapolates favorably in the energy range of interest for gamma-ray emission from fast ions in fusion plasmas.

Future space experiments dedicated to the observation of high-energy gamma and cosmic rays will increasingly rely on a highly performing calorimetry apparatus, and their physics performance will be primarily determined by the geometrical dimensions and the energy resolution of the calorimeter deployed. Thus it is extremely important to optimize its geometrical acceptance, the granularity, and its absorption depth for the measurement of the particle energy with respect to the total mass of the apparatus which is the most important constraint for a space launch. The proposed design tries to satisfy these criteria while staying within a total mass budget of about 1.6 tons. Calocube is a homogeneous calorimeter instrumented with Cesium iodide (CsI) crystals, whose geometry is cubic and isotropic, so as to detect particles arriving from every direction in space, thus maximizing the acceptance, granularity is obtained by filling the cubic volume with small cubic CsI crystals. The total radiation length in any direction is more than adequate for optimal electromagnetic particle identification and energy measurement, whilst the interaction length is at least suficient to allow a precise reconstruction of hadronic showers. Optimal values for the size of the crystals and spacing among them have been studied. The design forms the basis of a three-year R&D; activity which has been approved and financed by INFN. An overall description of the system, as well as results from preliminary tests on particle beams will be described.

The GAMMA-400 gamma-ray telescope currently under development is designed to measure fluxes of gamma rays and electron-positron cosmic-ray components, which could be associated with the annihilation or decay of dark matter particles, and to survey in detail the celestial sphere in order to search for and investigate discrete gamma-ray sources; to measure the energy spectra of Galactic and extragalactic dif- fuse gamma-ray emissions; and to study gamma-ray bursts and the gamma-ray emissions of active Sun. The GAMMA-400 energy range is 100 MeV to 3000 GeV. The gamma-ray telescope has an angular resolution of ∼0.01°, an energy resolution of ∼1%, and a proton rejection factor of ∼106. The GAMMA-400 will be installed on Russia’s Navigator space platform. Observations are planned to commence in 2018.

An update of the Resolution Elastic Neutron Scattering (RENS) approach consisting in measuring the elastically scattered neutron intensity versus the instrumental energy resolution is presented. In particular it is shown that the measured elastic scattering law as a function of the logarithm of the instrumental energy of resolution gives rise to an increasing sigmoid trend whose inflection point can be connected with the system relaxation time. The validity of the RENS approach is supported by a numerical simulation, taking into account a Gaussian resolution function and a Lorentzian scattering law, and experimentally by integrated EINS and QENS measurements performed as a function of temperature on three homologous disaccharide/water mixtures showing different relaxation times. Furthermore, the most important advantages of the RENS approach are discussed; in particular, in comparison with QENS, the RENS approach requires a smaller amount of sample, which is an important point in dealing with biological and exotic systems, is not affected by the use of model functions for fitting spectra, and furnishes a direct access to the system relaxation time.

Yıldız, Süleyman Cenk (Dogus Author) -- The conference paper was firstly submitted to 12th International Conference on Topics in Astroparticle and Underground Physics. Micromegas readouts are an attractive option for many of the rare event searches, due to their performance regarding energy resolution, gain stability, homogeneity and material budget. The T-REX project aims at developing further these novel readout techniques for Time Projection Chambers and their potential use in experiments searching for rare events. Here we will refer to the latest results regarding the use and prospects of Micromegas read-outs in axion physics (CAST and the future helioscope), as well as the R&D carried out within NEXT, to search for the neutrinoless double-beta decay.

Bu çalışma, 10-14 Mayıs 2010 tarihleri arasında Beijing[Çin]’da düzenlenen 14. International Conference on Calorimetry in High Energy Physics (CALOR 2010)’da bildiri olarak sunulmuştur. The energy deposited in the active medium of the crystal fluctuates event by event. This fluctuations in the lateral shower containment contributes to the stochastic term. The lateral shower shape determines the distribution of the energy deposition in a cluster of crystals around the impact point. The contribution to the stochastic term coming from fluctuations in the lateral shower containment of calorimeter prototypes of PbWO4 crystals have been simulated by GEANT4 for incident electrons at different energies.

The University of Pisa and INFN Pisa are developing a small animal PET prototype scanner employing continuous LYSO crystals and the silicon photomultiplier (SiPM) matrices fabricated at FBK-irst. The SiPM matrices have 64 SiPM pixel elements in a common substrate. The SiPM elements are 1.4 mm×1.5 mm size, in a 1.5 mm×1.5 mm pitch. The test of the first detector heads is taking place in collaboration with IFIC, Valencia. The detectors consist of a LYSO crystal of 12 mm×12 mm coupled to a SiPM matrix. Characterization and position determination tests have been carried out. The energy resolution obtained is 14.5% FWHM at 511 keV. The spatial resolution with center-of-gravity algorithms is 0.9 mm FWHM. A Maximum likelihood method is also being tested. This method allows to separate points at 1 mm distance, and to reconstruct correctly the interaction position also at the edges of the detector.

Superconducting tunnel junctions are promising as radiation detectors because of their larger energy resolution with respect to conventional Si-based detectors. We have developed a fabrication process for Nb-based STJ devices which allows to fabricate junctions with leakage currents well below 50 pA at 300 mK. a factor of 10~6 less than the leakage current at 4.2 K. The junctions are diamond-shaped with areas between 20times20 and 100times100 mum2. We report the details of the fabrication process, together with an analysis of the structure of films by AFM, SEM and X-ray spectroscopy. We show the measured I-V curves at 300 mK, together with preliminary results on x-ray measurements at 300 mK with a 5 mC 55Fe source.

Bu çalışma, 04-08 Haziran 2012 tarihleri arasında Santa Fe[New Mexico]’da düzenlenen 15. International Conference on Calorimetry in High Energy Physics (CALOR)’da bildiri olarak sunulmuştur. According to the Turkish Accelerator Center (TAC) project, a tau-charm factory is proposed based on colliding a 1 GeV electron beam against a 3.5 GeV positron beam. The Particle Factory (TAC-PF) detector will be constructed for the detection of the producing particles from this collision. PbWO4 and CsI(Tl) crystals are considered for the construction of the electromagnetic calorimeter. The photons generated from incident particles in the crystal material are detected by Avalanche photodiodes (APD) or PIN photodiodes placed at the end of the crystal. In this work, the contribution to the calorimetric energy resolution from both the shower fluctuations in the crystal and photoelectron statistics in the detectors have been simulated for PbWO4-APD and PbWO4-PIN combinations. Devlet Planlama Teşkilatı (DPT) 2006K-120470

Yıldız, Süleyman Cenk (Dogus Author) Micromegas detectors have shown a low and stable background level in the CAST experiment due to their low radioactive materials, good energy resolution and spatial resolution. Since 2008, four ultralow background periods have been observed with the new microbulk detectors. During these periods, the background level reduced one order of magnitude, reaching a value around 10-7 s-1 keV-1 cm-2 between 2 and 7 keV. In all cases, the intensity of the three fluorescence lines (at 3, 6 and 8 keV) presented at the background spectrum reduced but the relative ratio remained stable. To clarify the origin of these periods and might determine the ultimate background level of these readouts, a CAST-like detector has been installed at the Canfranc Underground Laboratory. The actual level is compatible with the one measured in CAST. A new Micromegas detectors is being developped for working in CAST experiment during 2011, based on the conclusions of this work.

For good energy resolution, the planar contact configuration requires good collection efficiency of both carriers. With shperical contacts, nuclear spectroscopy with energy resolutions as good as 3 % and nearly full charge collection is possible with only single carrier collection. This widens the class of semi-conductors that can be used for nuclear detectors. Theoretical and experimental results demonstrate that the differences in performance obtained with planar, semi-cylindrical and hemispherical devices occur because the induced charge depends on the geometry and the charge displacement and because the charge trapping is reduced by high electric fields. For hemispherical detectors, the effects of contact radii, electron and hole mobility-lifetime products, and voltage magnitude and polarity on the values of energy resolutions and full energy efficiency for γ-rays, are shown. Examples of gamma spectra observed with hemispherical HgI2 and CdTe detectors are given.