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showing 10 items of 753 documents
Precision measurement of the mass of the tau lepton
2014
An energy scan near the $\tau$ pair production threshold has been performed using the BESIII detector. About $24$ pb$^{-1}$ of data, distributed over four scan points, was collected. This analysis is based on $\tau$ pair decays to $ee$, $e\mu$, $eh$, $\mu\mu$, $\mu h$, $hh$, $e\rho$, $\mu\rho$ and $\pi\rho$ final states, where $h$ denotes a charged $\pi$ or $K$. The mass of the $\tau$ lepton is measured from a maximum likelihood fit to the $\tau$ pair production cross section data to be $m_{\tau} = (1776.91\pm0.12 ^{+0.10}_{-0.13}$) MeV/$c^2$, which is currently the most precise value in a single measurement.
In-beam tests of scintillating fibre detectors at MAMI and at GSI
2008
The performance of scintillating fibre detectors was studied with electrons at the spectrometer facility of the Mainz microtron MAMI, as well as in a C-12 beam of 2 AGeV energy and in a beam of different particle species at GSI. Multi-anode photomultipliers were used to read out one or more bundles of 128 fibres each in different geometries. For electrons a time resolution of FWHM = 1 ns was measured in a single detector plane with a detection efficiency epsilon > 99%. A time resolution of 310 ps (FWHM) between two planes of fibres was achieved for carbon ions, leading to a FWHM = 220 ps for a single detector. The hit position residual was measured with a width of FWHM = 0.27 mm. The var…
A time-differential Mössbauer emission spectrometer with high efficiency and high time resolution
1986
A high-efficiency, high rate-capability, computer-based measuring setup for Time-Differential Mossbauer Spectroscopy was constructed. Applying NaI(Tl) and plastic scintillators for the detection of the 14.4 keV and 122 keV γ-radiation respectively, a superior timing (2, 3 ns FWHM) was achieved by a “fast-fast-ultra fast” timing method developed for that purpose.
Digital performance improvements of a CdTe pixel detector for high flux energy-resolved X-ray imaging
2015
Abstract Photon counting detectors with energy resolving capabilities are desired for high flux X-ray imaging. In this work, we present the performance of a pixelated Schottky Al/p-CdTe/Pt detector (4×4) coupled to a custom-designed digital readout electronics for high flux measurements. The detector (4×4×2 mm 3 ) has an anode layout based on an array of 16 pixels with a geometric pitch of 1 mm (pixel size of 0.6 mm). The 4-channel readout electronics is able to continuously digitize and process the signals from each pixel, performing multi-parameter analysis (event arrival time, pulse shape, pulse height, pulse time width, etc.) even at high fluxes and at different throughput and energy re…
Timing results using an FPGA-based TDC with large arrays of 144 SiPMs
2015
Silicon photomultipliers (SiPMs) have become an alternative to traditional tubes due to several features. However, their implementation to form large arrays is still a challenge especially due to their relatively high intrinsic noise, depending on the chosen readout. In this contribution, two modules composed of SiPMs with an area of roughly mm mm are used in coincidence. Coincidence resolving time (CRT) results with a field-programmable gate array, in combination with a time to digital converter, are shown as a function of both the sensor bias voltage and the digitizer threshold. The dependence of the CRT on the sensor matrix temperature, the amount of SiPM active area and the crystal type…
The EM imaging reconstruction method in γ-ray astronomy
1998
Abstract The simpler imaging reconstruction methods used for γ-ray coded mask telescopes are based on correlation methods, very fast and simple-to-use but with limitations in the reconstructed image. To improve these results, other reconstruction methods have been developed, such as the maximum entropy methods or the Iterative Removal Of Sources (IROS). However, such kind of methods are slower and can be impracticable for very complex telescopes. In this paper we present an alternative image reconstruction method, based on an iterative maximum likelihood algorithm called the EM algorithm, easy to implement and that can be successfully used for not very complex coded mask systems, as is the …
Effects of scintillation light collection on the time resolution of a time-of-flight detector for annihilation quanta
1990
Monte Carlo methods were used to simulate the production and collection of scintillation light in a BaF/sub 2/ crystal. The calculated results were compared to measured values for detectors with different heights. Based on this simulation, a TOF (time-of-flight) detector consisting of two conical BaF/sub 2/ crystals (base radius 18 mm, top radius 15 mm, height 25 mm) was assembled. The total time resolution of this system was (210+or-5) ps FWHM (full width at half maximum) for 511-keV annihilation quanta and was found to be independent of the source position between the detectors. Since the time resolution of the TOF detector system consisting of two conical BaF/sub 2/ crystals is sufficien…
Spectroscopic response of a CdZnTe multiple electrode detector
2007
Abstract The spectroscopic performances of a CdZnTe detector (crystal size: 5×5×0.9 mm 3 ) with five electrodes (cathode, anode and three steering electrodes) were studied. The anode layout, which consists of a circular electrode ( φ =80 μm) surrounded by two ring electrodes (gap=100 μm; radial width Δ r =100 μm) and by one electrode that extends to the edge of the crystal, is mostly sensitive to the electron carriers, overcoming the well known effect of the hole trapping in the measured spectra. We report on the spectroscopic response of the detector at different bias voltages of the electrodes and at various photon energies ( 109 Cd, 241 Am and 57 Co sources). The CdZnTe detector exhibits…
Experimental results from Al/p-CdTe/Pt X-ray detectors
2013
Abstract Recently, Al/CdTe/Pt detectors have been proposed for the development of high resolution X-ray spectrometers. Due to the low leakage currents, these detectors allow high electric fields and the pixellization of anodes with the possibility to realize single charge carrier sensing detectors. In this work, we report on the results of electrical and spectroscopic investigations on CdTe diode detectors with Al/CdTe/Pt electrode configuration (4.1×4.1×0.75 and 4.1×4.1×2 mm 3 ). The detectors are characterized by very low leakage currents in the reverse bias operation: 0.3 nA at 25 °C and 2.4 pA at −25 °C under a bias voltage of −1000 V. The spectroscopic performance of the detectors at b…
Longitudinal and transverse momentum distributions of 9Li fragments from break-up of 11Li
1995
7 pages, 3 figures, 1 table.