Search results for "Toe"
showing 10 items of 3824 documents
Silicon detector for a Compton camera in nuclear medical imaging
2002
Electronically collimated gamma ca\-me\-ras based on Com\-pton scattering in silicon pad sensors may improve imaging in nuclear medicine and bio-medical research. The work described here concentrates on the silicon pad detector developed for a prototype Compton camera. The silicon pad sensors are read out using low noise VLSI CMOS chips and novel fast triggering chips. Depending on the application a light weight and dense packaging of sensors and its readout electronics on a hybrid is required. We describe the silicon pad sensor and their readout with the newly designed hybrid. %The silicon detector of a Compton camera %may contain up to $10^5$~analogue channels requiring %a fast and low co…
Particle detectors made of high-resistivity Czochralski silicon
2005
We have processed pin-diodes and strip detectors on n- and p-type high-resistivity silicon wafers grown by magnetic Czochralski method. The Czochralski silicon (Cz-Si) wafers manufactured by Okmetic Oyj have nominal resistivity of 900 O cm and 1.9 kO cm for n- and p-type, respectively. The oxygen concentration in these substrates is slightly less than typically in wafers used for integrated circuit fabrication. This is optimal for semiconductor fabrication as well as for radiation hardness. The radiation hardness of devices has been investigated with several irradiation campaigns including low- and high-energy protons, neutrons, g-rays, lithium ions and electrons. Cz-Si was found to be more…
Electron-TOF-analyser for complete momentum analysis in photoemission from surfaces
2001
Abstract We present a new method for momentum-selective imaging by means of a time-of-flight (TOF) technique. The instrument employs a time- and space-resolving delayline detector in combination with a parabolic electrostatic field and a drift space. We use this kind of spectrometer, to raise the efficiency of experiments, which are total momentum resolved. The main difference to conventional photoemission experiments using a rotatable spectrometer is the simultaneous detection of all emitted photoelectrons. In addition to this feature, the angular distribution should be directly visible, to observe solid state symmetries. In order to facilitate these requirements, we use a delayline detect…
Efficiency studies for a tracking detector based on square 1.5m long scintillating fibers read out by SiPM
2009
Abstract A tracking detector based on 1.5 m long scintillating fibers is being developed for the electron arm of the KAOS spectrometer at the Mainz Microtron MAMI. Measurements on light attenuation, particle detection efficiencies and accidental coincidence rates with a prototype set-up using 2 × 2 mm 2 fibers read out by silicon photomultipliers (SiPM) are presented. The highest efficiency at the lowest accidental coincidence rate was reached for high trigger thresholds at the largest SiPM bias voltages. The influence of signal attenuation and dispersion on detection efficiencies is discussed. The results are in good agreement with a Monte Carlo model that was used to predict detector char…
Polarization phenomena in Al/p-CdTe/Pt X-ray detectors
2013
Over the last decades, CdTe detectors are widely used for the development of room temperature X-ray and gamma ray spectrometers. Typically, high resolution CdTe detectors are fabricated with blocking contacts (indium, aluminum) ensuring low leakage currents and high electric field for optimum charge collection. As well known, time instability under bias voltage (termed as polarization) is the major drawback of CdTe diode detectors. Polarization phenomena cause a progressive degradation of the spectroscopic performance with time, due to hole trapping and detrapping from deep acceptors levels. In this work, we studied the polarization phenomenon on new Al/p-CdTe/Pt detectors, manufactured by …
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…
A CdTe position sensitive spectrometer for hard X- and soft γ-ray polarimetry
2002
Coded Imager and Polarimeter for High Energy Radiation (CIPHER) is a hard X- and soft gamma- ray spectroscopic and polarimetric coded mask telescope based on an array of Cadmium telluride microspectrometers. The position sensitive detector (PSD) will be arranged in 4 modules of 32 x 32 crystals, each of 2 x 2 mm(2) cross-section and 10 mm thickness giving a total active area of about 160 cm(2), operating over a wide energy range (similar to10 keV to 1 MeV). Each PSD module is obtained by aligning 32 linear arrays of micro-detectors each also containing the integrated analog front end electronics on a thin ceramic layer. The CIPHER instrument will be proposed for a balloon experiment, both i…
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…
Single-component plasma of photoelectrons
2007
Abstract Ten-nanosecond pulses of photoelectrons liberated by intense UV laser pulses from a thin gold layer are captured into a single-component plasma that is ideally suited to cool antiprotons ( p ¯ ) for antihydrogen ( H ¯ ) production. Up to a billion electrons are accumulated using a series of laser pulses, more than are needed for efficient p ¯ cooling in the large traps now being used for loading p ¯ for H ¯ production. The method is demonstrated within an enclosed vacuum space that is entirely at 4 K, and is thus compatible with the exceptional cryogenic vacuum that is desirable for the long-term storage of antihydrogen. The pitfalls of other electron accumulation methods are entir…
Non-destructive diagnostics of thin fissile layers
2003
We have developed a non-destructive nuclear technique useful for the diagnostic of thin layers of fissile element. The method is based on the correlation between the fission fragment energy losses and the distortion of the energy spectrum of the alpha-particles emerging from the layer itself. We have also measured the sputtering rate of atoms from a fission layer which can be the cause of an important degradation in a working apparatus.