Characterization of 3D thermal neutron semiconductor detectors Uher, J.; Fröjdh, C.; Jakůbek, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2007, Letnik:
576, Številka:
1
Journal Article
Recenzirano
Neutron semiconductor detectors for neutron counting and neutron radiography have an increasing importance. Simple silicon neutron detectors are combination of a planar diode with a layer of an ...appropriate neutron converter such as
6LiF. These devices have limited detection efficiency of not more than 5%. The detection efficiency can be increased by creating a 3D microstructure of dips, trenches or pores in the detector and filling it with a neutron converter. The first results related to the development of such devices are presented. Silicon detectors were fabricated with pyramidal dips on the surface covered with
6LiF and then irradiated by thermal neutrons. Pulse height spectra of the energy deposited in the sensitive volume were compared with simulations. The detection efficiency of these devices was about 6.3%. Samples with different column sizes were fabricated to study the electrical properties of 3D structures. Charge collection efficiencies in silicon columns from 10 to 800
μm wide and 80–200
μm high were measured with alpha particles.
The neutron detection efficiency of a full 3D structure was simulated. The results indicate an increase in detection efficiency by a factor of 6 in comparison with a standard planar neutron detector.
An attempt is made to develop a polarized deuteron source suited for the Van de Graaff accelerator of Czech Technical University in Prague. We based on Kaminsky’s experiment on channeling deuterons ...through a Ni single crystal. The setup is described, which contains permanent magnets with a transversal magnetic field to increase the deuteron polarization using Sona-method (zero transition). The measurements of tensor polarization were carried out with TiT target. The result is
for a weak field at the target without channeling. The ultimate aim is to produce 14-MeV polarized neutrons which will be used jointly with the frozen-spin polarized deuteron target for measurement
and
asymmetries in the
‑transmission experiment.
In a spectroscopic study of non-irradiated and proton-irradiated silicon diodes, the detectors were illuminated from the front side and from the rear side by various alpha particle sources (mainly ...ThC’) and by monoenergetic protons with energies from 1.0 to 2.5 MeV. Their response characteristics have been studied as a function of the incoming particle energy and the applied bias voltage. The charge collection efficiency was determined as a function of fluence.
For the study and detection of neutrons in space environments such as planetary and earth orbiting missions semiconductor silicon diode detectors have been characterized and calibrated at various ...thermal neutron sources. Two types of diodes adapted for thermal neutron detection were investigated: silicon MESA planar detectors equipped with thin 6 LiF layers and silicon heterodiodes with a layer of natural boron or enriched 10 B. The response and absolute detection efficiency have been measured. The influence of bias voltage and converter layer thickness were studied. As neutron sources we used a homogenous isotropic thermal neutron field by a set of PuBe radionuclide sources placed in a graphite pile as well as a parallel thermal neutron beam with high Cd ratio (10 5 ) and suppressed gamma background. Depending on the converter layer thickness and/or boron layer thickness as well as the choice of the threshold level, efficiencies of approximately 1% are obtained for both the silicon diodes with thin 6 LiF and the boron rich silicon detectors. These values guarantee optimal stability of operation in remote and different environments as well as maximum signal-to-noise ratio by enhanced suppression of unwanted signals and gamma background.
Charged-particle coincidence correlated measurements such as angular correlations between rare and main fission fragments measured with conventional detectors provide only partial and limited ...information (energy cutoff, narrow range of studied ion Z numbers). Many of these drawbacks arise from the standard solid state detectors used so far which can be solved simultaneously by usage of highly segmented single-quantum counting pixel detectors. The Timepix pixel device, which is equipped with energy and time sensitivity capability per pixel, provides high granularity, wide dynamic range and per pixel threshold. This detector operated with integrated USB-readout interfaces such as the USB 1.0 and FITPix devices and the data acquisition software tool Pixelman, both developed for the pixel detectors of the Medipix-family, enables a variety of instrumental configurations, visualization, real-time event-by-event selection as well as vacuum and portability of operation for flexible measurements on different targets and setups. These features combined with event track analysis provide enhanced signal to noise ratio with a high suppression of background and unwanted events. The detector provides multi-parameter information (position, energy and time) for basically all types of ionizing particles in a wide dynamic range of energy (pixel energy threshold ≈ 4 keV), interaction/arrival time (timepix clock step ≥ 100 ns) and position (pixel size = 55 μm). High selectivity is achieved by spatial and time correlation in the same sensor. In addition, several detectors can be run in coincidence. The open and close exposition (shutter) time as well as the readout DAQ can be fully synchronized. For this purpose, we have assembled a modular multi-parameter, tunable and extendable coincidence detector array system based on two and more Timepix devices which can be coupled with supplementary detectors (solid state ΔE detectors and/or ionization chambers) for enhanced ion selectivity. We describe the individual configurations and techniques together with the experiments carried out at several neutron beam/source facilities. We summarize the results and capabilities of application.
Studying of hypernuclei with nuclotron beams Averyanov, A. V.; Avramenko, S. A.; Aksinenko, V. D. ...
Physics of atomic nuclei,
12/2008, Letnik:
71, Številka:
12
Journal Article
Recenzirano
A spectrometer is created to study relativistic hypernuclei produced with beams of accelerated nuclei from the Nuclotron facility (Dubna, JINR). Test runs have been carried out and the conclusion is ...drawn that the properties of the facility meet the requirements of the task of searching for unknown and studying poorly known neutron-rich hypernuclei.
Planar semiconductor diodes supplemented with a layer of an appropriate neutron converter such as 6 LiF can be used for thermal neutron counting or imaging. Neutrons interacting in the converter ...generate alphas and tritons which enter the semiconductor and are detected there. However, simple planar devices suffer from limited detection efficiency which cannot reach more than about 5%. The limit in detection efficiency can be overcome by etching a 3D microstructure of trenches, pores or columns in the detector and filling it with the neutron converter. The overall neutron detection efficiency of such structure with pores was simulated. The results indicate an increase in the detection efficiency by factor of 6 in comparison with a standard planar neutron detector. Samples with different silicon column sizes were fabricated to study the electrical properties of 3D structures. The charge collection efficiency in silicon columns from 10 mum to 800 mum wide and 80 mum high was measured. Single pad detectors with pores were also fabricated and tested for thermal neutron detection. The samples have square pores of 20 mum wide, ~60 mum deep. The pore pitch is 70 mum. 6 LiF was used as the neutron converter in all cases. Pulse height spectra of the filled samples irradiated by thermal neutrons were measured. The measurement proved functionality of such detectors and its usability for thermal neutron detection.
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