The recent availability of single crystal (sc) CVD diamond samples of very good quality and suitable thickness and surface area has opened new application fields in nuclear detection and dosimetry ...such as hadron radiotherapy and neutron spectrometry in fusion reactors. At the same time, dot, strip, and pixel detectors with unprecedented performances have been successfully realized and exploited in the framework of high energy physics (HEP). While the goal of a charge collection distance (ccd) of 200 μm was reached with polycrystalline (pc) samples in the year 2000, values of ccd up to 0.42 mm at 0.2 V/μm are now reported for the new sc samples. From the point of view of “detector quality,” the mobility–lifetime product for carriers is now approaching that of one of the best nonsilicon detector materials like CdTe, but it seems still far from that of Si. The most important point seems to be related to the homogeneity of new sc samples, which now in some cases displays an energy resolution down to 0.4% for Am-241 alpha particles and of 2.9% for 14.1 MeV neutrons. CVD single crystal beam monitors are now currently running in HEP experiments and their performances are compared with more recent radiation hard Si detectors. CVD diamond detectors are quoted to be capable to withstand particle fluxes over 10
15 cm
−2 (which corresponds to a 10-year experiment run) with no counting losses and only a small reduction in S/N ratio. A more intriguing question is concerning priming, which is very important for detector performances: while no priming seems necessary for sc samples, in the case of pc samples, a simple priming with blue light instead of X-rays or beta-rays is possible, with the issue of different or better detector performances. The paper will review the more recent history of CVD diamond nuclear detectors with respect to material quality and priming. Some detectors and dosimeter performances in different top level fields will be quoted and possible future scenarios will be described.
Diamond pixel modules Asner, D.; Barbero, M.; Bellini, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2011, Letnik:
636, Številka:
1
Journal Article
Recenzirano
With the commissioning of the LHC in 2010 and upgrades expected in 2015, ATLAS and CMS are planning to upgrade their innermost tracking layers with radiation hard technologies. Chemical Vapor ...Deposition diamond has been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle, CDF and all LHC experiments. This material is now being considered as a sensor material for use very close to the interaction region where the most extreme radiation conditions exist. Recently the RD42 collaboration constructed, irradiated and tested polycrystalline and single-crystal chemical vapor deposition diamond sensors to the highest fluences expected at the super-LHC. We present beam test results of chemical vapor deposition diamond up to fluences of 1.8×10
16
protons/cm
2 illustrating that both polycrystalline and single-crystal chemical vapor deposition diamonds follow a single damage curve. We also present beam test results of irradiated complete diamond pixel modules.
Diamond displays a large variety of luminescence centers which define its optical properties and can be either created or modified by irradiation. The main purpose of the present work is to study the ...radiation hardness of several of such centers in homoepitaxial single-crystal CVD diamond by following the evolution of photoluminescence and ionoluminescence upon 2
MeV proton irradiation. Luminescence decays were observed with values of the fluence at half of the starting luminescence (
F
1/2) of the order of 10
14
cm
−
2
. The 3H center displayed a non-monotonic behavior, with a growing behavior and a subsequent decay with a rather high
F
1/2 value (in the order of few a 10
16
cm
−
2
), maintaining at the highest fluences an intensity significantly higher than the blue A-band. A simple model based on a double-exponential trend was defined to fit with satisfactory accuracy the evolution of the 3H center. Several PL centers (namely: 3H, TR12, 491
nm and 494
nm) exhibited clear correlations and anti-correlations in their fluence dependences, which were considered in the attempt to acquire some insight into their possible alternative attributions.
We report on a novel method for the fabrication of three-dimensional buried graphitic micropaths in single crystal diamond with the employment of focused MeV ions. The use of implantation masks with ...graded thickness at the sub-micrometer scale allows the formation of conductive channels which are embedded in the insulating matrix at controllable depths. In particular, the modulation of the channels depth at their endpoints allows the surface contacting of the channel terminations with no need of further fabrication stages.
In the present work we describe the sample masking, which includes the deposition of semi-spherical gold contacts on the sample surface, followed by MeV ion implantation. Because of the significant difference between the densities of pristine and amorphous or graphitized diamond, the formation of buried channels has a relevant mechanical effect on the diamond structure, causing localized surface swelling, which has been measured both with interferometric profilometry and atomic force microscopy. The electrical properties of the buried channels are then measured with a two point probe station: clear evidence is given that only the terminal points of the channels are electrically connected with the surface, while the rest of the channels extends below the surface. IV measurements are employed also to qualitatively investigate the electrical properties of the channels as a function of implantation fluence and annealing.
In this paper, we describe the main features of the ionoluminescence (IL) apparatus recently installed at the external scanning microbeam facility of the 3MV Tandetron accelerator of the INFN LABEC ...Laboratory in Firenze. The peculiarity of this IL set-up resides in the fact that the light produced by the ion irradiation of the specimen is collected by a bifurcated optical fiber, so that photons are shunted both to a CCD spectrometer, working in the 200–900nm wavelength range, and to a photomultiplier (PMT). The accurate focusing of the optical system allows high photon collection efficiency and this results in rapid acquisition of luminescence spectra with low ion currents on luminescent materials; simultaneously, luminescence maps with a spatial resolution of 10μm can be acquired through the synchronization of PMT photon detection with the position of the scanning focused ion beam. An optical filter with a narrow passband facing the photomultiplier allows chromatic selectivity of the luminescence centres.
The IL apparatus is synergistically integrated into the existing set-up for ion beam analyses (IBA). The upgraded system permits simultaneous IL and PIXE/PIGE/BS measurements. With our integrated system, we have been studying raw lapis lazuli samples of different known origins and precious lapis lazuli artworks of the Collezione Medicea of Museum of Natural History, University of Firenze, aiming at characterising their composition and provenance.
An Au/SiO2 system with most of the metal particles less than 2.0 nm in size were prepared by deposition on silica of preformed gold sols derived from Au(PPh3)3Cl. In this form, it was inactive in the ...CO + O2 reaction at ca. 333 K, because of the presence of phosphine ligands on the surface of metal particles. The system became catalytically active in this reaction after treatment in O2 at 673 K, which also resulted in a slight sintering of the metal phase (mean size = 2.9 nm). By subsequent heating in H2 at 673 K, the mean size of gold particles increased up to 3.4 nm. Such particles exhibited a lower amount of step surface sites able to adsorb CO, but became more active in the CO + O2 reaction. This suggested that the reaction steps involving oxygen can occur more effectively on Au sites present on larger and smoother gold particles.
SiC detectors for neutron monitoring Manfredotti, C.; Lo Giudice, A.; Fasolo, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2005, Letnik:
552, Številka:
1
Journal Article
Recenzirano
Semiconductor detectors equipped with a converter like
6LiF or
10B can currently be considered a very interesting alternative to conventional neutron detectors, especially because of their ...compactness and reliability. The materials for the detection of the ions produced in the converter are generally either Si or GaAs. SiC detectors presented in this work are completely new devices which are proved to be very suitable for neutron detection, dosimetry and beam monitoring. Their capability to withstand high radiation doses should largely overcome the performances of Si and GaAs; moreover, because of the lower
Z value, gamma-ray discrimination turns out to be more efficient. In this work, the results obtained with a series of large-area epitaxial SiC Schottky barrier detectors will be presented and discussed.
IBIC analysis of CdTe/CdS solar cells Colombo, E.; Bosio, A.; Calusi, S. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
06/2009, Letnik:
267, Številka:
12
Journal Article
Recenzirano
Odprti dostop
This paper reports on the investigation of the electronic properties of a thin film CdS/CdTe solar cell with the Ion Beam Induced Charge (IBIC) technique. The device under test is a thin film (total ...thickness around 10
μm) multilayer heterojunction solar cell, displaying an efficiency of 14% under AM1.5 illumination conditions. The IBIC measurements were carried out using focused 3.150
MeV He ions raster scanned onto the surface of the back electrode. The charge collection efficiency (CCE) maps show inhomogeneous response of the cell to be attributed to the polycrystalline nature of the CdTe bulk material.
Finally, the evolution of the IBIC signal versus the ion fluence was studied in order to evaluate the radiation hardness of the CdS/CdTe solar cells in a view of their use in solar modules for space applications.
The transport properties of a 4H-SiC Schottky diode have been investigated by the ion beam induced charge (IBIC) technique in lateral geometry through the analysis of the charge collection efficiency ...(CCE) profile at a fixed applied reverse bias voltage.
The cross section of the sample orthogonal to the electrodes was irradiated by a rarefied 4MeV proton microbeam and the charge pulses have been recorded as function of incident proton position with a spatial resolution of 2μm.
The CCE profile shows a broad plateau with CCE values close to 100% occurring at the depletion layer, whereas in the neutral region, the exponentially decreasing profile indicates the dominant role played by the diffusion transport mechanism.
Mapping of charge pulses was accomplished by a novel computational approach, which consists in mapping the Gunn’s weighting potential by solving the electrostatic problem by finite element method and hence evaluating the induced charge at the sensing electrode by a Monte Carlo method. The combination of these two computational methods enabled an exhaustive interpretation of the experimental profiles and allowed an accurate evaluation both of the electrical characteristics of the active region (e.g. electric field profiles) and of basic transport parameters (i.e. diffusion length and minority carrier lifetime).
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