A rotatable electron spectrometer for multicoincidence experiments

Highly segmented detector arrays for studying the resonant decay of unstable nuclei

New results and future plans with real photons at MAMI

Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera-based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photoemitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station.

<p>The PKU energetic particle instrument (EPI) is designed to make measurements of the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV.  The EPI consists of four dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range of 20–400 keV and ions from 20 keV–6 MeV. The output of front detectors is taken in anti-coincidence with center detectors, to achieve the low background. The magnet telescopes also employ the well-established dE/dx vs. total energy approach to determine the nuclear charge and mass of some ion species.</p>

The WFM (Wide Field Monitor) instrument of eXTP (Enhanced X-ray Timing and Polarimetry Mission) covers a large fraction of the sky in the (2 - 50) keV energy range, with good angular (5 arcmin - FWHM) and energy (better than 500 eV - FWHM at 6 keV) resolutions. The WFM instrument is part of the scientific payload of the eXTP X-ray satellite, together with the Spectroscopic Focusing Array (SFA), the Large Area Detector (LAD) and the Polarimetry Focusing Array (PFA) instruments. The WFM is distributed in three camera pairs with a broad field of view (180° × 90° FWZR). Each camera is composed by a coded mask assembly, a collimator, a DSP (detector support plate) which hosts four DAs (Detector Assemblies) - each DA including an SDD (Silicon Drift Detector) and its corresponding FEE (Front-End Electronics) - and one BEE (Back-End Electronics). The coded mask area is 260 × 260 mm. It is manufactured from 150 μm thick Tungsten foil. The mask shall keep a flatness of ±50 μm over its surface for the whole operating temperature range of the WFM instrument. A pretension mechanism is carried out with a set of mask frames to fulfil this requirement. A collimator structure supports the coded mask assembly and the detector box. The collimator will provide the stiffness required to avoid deformations due to accelerations and thermal stresses. In this paper, we present the mechanical design drivers of the camera structure (i.e. coded mask assembly, collimator and DSP), the alignment procedure of the detector plane (i.e. the four Silicon tiles) and the detector plane with the coded mask and the camera thermal control system.

A brief review of the indirect detection signatures of dark matter is given. In particular, detection methods of dark matter particle annihilation to antimatter and γ-rays are reviewed. With the GLAST satellite soon to be launched, a crucial window in the energy range of a few GeV up to 300 GeV will open. The good angular and energy resolution of the instrument means that structures predicted by cold dark matter models can be searched for. Large, currently planned ground-based imaging Cherenkov telescope arrays, may further improve the limits, or discover a signal, if the current understanding of halo dark matter structure is correct.

The energy-resolved photon counting detector provides the spectral information that can be used to generate images. The novel imaging methods, including the K-edge imaging, projection-based energy weighting imaging and image-based energy weighting imaging, are based on the energy-resolved photon counting detector and can be realized by using various energy windows or energy bins. The location and width of the energy windows or energy bins are important because these techniques generate an image using the spectral information defined by the energy windows or energy bins. In this study, the reconstructed images acquired with K-edge imaging, projection-based energy weighting imaging and image-based energy weighting imaging were simulated using the Monte Carlo simulation. The effect of energy windows or energy bins was investigated with respect to the contrast, coefficient-of-variation (COV) and contrast-to-noise ratio (CNR). The three images were compared with respect to the CNR. We modeled the x-ray computed tomography system based on the CdTe energy-resolved photon counting detector and polymethylmethacrylate phantom, which have iodine, gadolinium and blood. To acquire K-edge images, the lower energy thresholds were fixed at K-edge absorption energy of iodine and gadolinium and the energy window widths were increased from 1 to 25 bins. The energy weighting factors optimized for iodine, gadolinium and blood were calculated from 5, 10, 15, 19 and 33 energy bins. We assigned the calculated energy weighting factors to the images acquired at each energy bin. In K-edge images, the contrast and COV decreased, when the energy window width was increased. The CNR increased as a function of the energy window width and decreased above the specific energy window width. When the number of energy bins was increased from 5 to 15, the contrast increased in the projection-based energy weighting images. There is a little difference in the contrast, when the number of energy bin is increased from 15 to 33. The COV of the background in the projection-based energy weighting images is only slightly changed as a function of the number of energy bins. In the image-based energy weighting images, when the number of energy bins were increased, the contrast and COV increased and decreased, respectively. The CNR increased as a function of the number of energy bins. It was concluded that the image quality is dependent on the energy window, and an appropriate choice of the energy window is important to improve the image quality.

The stability and performance of nanoscale junctions are closely related to the local effective temperature. The local effective temperature is mainly caused by the competition between heating and cooling processes in inelastic electron-phonon scat- tering. Local cooling occurs when the rate of energy in cooling exceeds that in heating. Previous research has been done using either specific potential configuration or an adatom to achieve local cooling. We propose an engineer-able local-cooling mechanism in asymmetric two-terminal tunneling junctions, in which one electrode is made of metal, whereas the other is made of a selectable bad-metal, such as heavily-doped polysilicon. The width of energy window of the selectable material, defined as the width covering all possible energy states counting from the conduction band minimum, can be engineered through doping. Interestingly, we have shown that substantial local cooling can be achieved at room temperature when the width of energy window of the low-density electrode is comparable to the energy of the phonon. The unusual local cooling is caused by the narrowed width of energy window, which obstructs the inelastic scattering for heating.

We discuss the physics case for a new experimental setup that consists of the Crystal Ball multiphoton spectrometer and the CLAS12 forward detector installed at the tagged photon beam of Hall‐B at JLab. The proposed apparatus will provide nearly 4π sr coverage and good energy and angular resolution for photons and protons allowing a detailed high statistics investigation of the reactions with multiple photons. Such setup can be used to investigate the spectrum of doubly‐strange Ξ via their neutral decays, test C, CP, and T invariance in the neutral and charged decays of η and η′ perform precise measurements of the Dalitz and double Dalitz decays of pseudoscaler and vector mesons, etc. Such data may also shed new light on the existence and the properties of the earlier claimed light exotic mesons.

High-resolution Schottky CdTe diode for hard X-ray and gamma-ray astronomy

The status of the CYGNUS experiment: Past, present, and future

The ANTARES Collaboration successfully completed in May 2008 the deployment of an underwater neutrino detector in the Mediterranean Sea, offshore the France coast, at 2475 m b.s.l. The main purpose of this experiment is the detection of high energy neutrinos produced in astrophysical sources. Neutrinos being neutral, stable and weakly interacting particles can travel undeflected trough the Universe reaching the Earth even from the inner core of very distant objects. They are therefore very powerful messengers which can provide us invaluable information about processes which are hardly accessible with other messengers like photons. The detection of astrophysical neutrinos is very challenging due to the very small neutrino interaction cross-section and the huge background produced by other cosmic rays. Very large instrumented volumes and a very efficient shielding are therefore needed to detect astrophysical neutrinos. Moreover a very good angular resolution is mandatory to trace detected neutrinos back to their origin. ANTARES with 0.04 km2 muon effective area at Ev > 10 TeV shielded by more than 2000 m of water and an angular resolution of 0.3° at Ev > 10 TeV, perfectly fits these requirements. The ANTARES deployment started in 2006 and many data have been already collected with a partial detector. The detector in its final configuration is described and preliminary results of data analysis, especially about calibration issues, are shown. The completion of the ANTARES detector paved the way towards an even larger submarine neutrino telescope in the Mediterranean Sea like the one planned by the KM3NeT project.

Monte-Carlo simulation for scatter correction compensation studies in SPECT imaging using GATE software package

A high-sensitivity low-energy electron diffraction (LEED) system based on an electron energy loss spectrometer is described. This instrument is found to have the advantages of good angular resolution, very good energy resolution, low target current and high dynamic range. The experimental control and data collection are automated, which is found to be necessary to reduce measurement times to practicable levels. The performance of the system is illustrated by LEED data obained for a submonolayer of C6H6 physisorbed on graphite at 35 K where a weak diffraction feature is observed for the first time.

Single-crystal Diamond Detectors (SDDs), due to their high radiation hardness, fast response time and small size, are good candidates as fast neutron detectors in those environments where the high neutron flux is an issue, such as spallation neutron sources and the next generation thermonuclear fusion plasmas, i.e. the ITER experiment. Neutron detection in SDDs is based on the collection of electron-hole pairs produced by charged particles generated by neutron interactions with 12C. Recent measurements have demonstrated the SDD capability of measuring the neutron flux with a good energy resolution and at high rates. In this work a novel detector based on a 12-pixels SDD matrix will be presented. Each pixel is equipped with an independent electronic chain: the fast shaping preamplifier coupled to a digitizer is able to combine the high rate capability and the good energy resolution. Two CAEN digitizers are compared and the possibility of performing good energy resolution measurements (<2%) and at high rates (>1 MHz per channel) is described. Each pixel was characterized and calibrated using an 241Am source: the energy resolution was evaluated and gives a mean value of 1.73% at 5.5 MeV. The good energy resolution achieved and its uniformity between pixels are the demonstration of the capability of this novel detector as a spectrometer. This system will be installed during the next Deuterium-Tritium campaign on a collimated vertical line of sight at JET for 14 MeV neutron measurements.