430 research outputs found
Utilization of Low Voltage D-T Neutron Generators in Neutron Physics Studies
No full textIn a small nuclear laboratory of a developing country a low voltage D-T neutron generator can be a very useful scientific apparatus. Such machines have been used successfully for more than 40 years in teaching and scientific research. This thesis is a description of contributions by the author to make a few more additions to their existing variety of applications.<p /> The original continuous mode 150-kV D-T neutron generator has been modified to have also a capability of producing 2-ns pulsed neutrons. Together with a carefully designed 10 m long flight path collimator and shielding of a 25 cmØ x 10 cm thick BC-501 neutron detector, the pulsing system was successfully used for measuring the double differential cross-section (DDX) of natural iron for 14.1-MeV neutron from the angle of 30 deg to 150 deg in 10 deg steps.<p /> In order to extend the utility of the generator, two methods for converting the almost monoenergetic 14-MeV neutrons to monoenergetic neutrons of lower energy were proposed and tested. Both designs used the neutron-proton interaction at a circular surface-of-revolution made of hydrocarbon materials. The first design is for a pulsed neutron generator and the second design is for an ordinary continuous mode generator. The latter method was successfully used to measure the scintillation light output of a 1.4 cmØ spherical NE-213 scintillation detector
Development and Use of Neutron Scintillator Systems for Fusion Plasma Diagnostics
No full textThis thesis reports on research and development work, made in connection with the use of organic scintillators, for neutron spectrometry. It also gives a general review on the use of organic scintillators for the detection of neutrons generated from fusion of deuterium (D) and fusion between a mixture of deuterium and tritium (T) in thermonuclear plasmas. The basic mechanisms and limitations of organic scintillators are described. A library of computer routines utilizing Monte Carlo technique for neutron transport in organic media written by the author of this thesis, is presented. The applications of organic scintillators in different neutron time-of-flight spectrometers developed at, or with, participation of the Dept. of Reactor Physics, are also described. <p> The thesis is based on 6 papers. Paper 1 gives a method how to make a relative and absolute calibration of an array of 16 neutron scintillator detectors. The method utilizes the measurement of differential count rates for different high voltages applied on the photomultiplier tubes at different discriminator levels. If the maximum of the differential count rate is plotted as a function of high voltage, calibration coefficients for each neutron detector are obtained and these coefficients can then be used for the calibration. <p> Papers 2 and 3 describe a Monte Carlo code for the 14.1 MeV combined proton-recoil and neutron time-of-flight neutron spectrometer TANSY. Paper 2 is a short version of paper 3. The TANSY spectrometer will be installed at the Joint European Torus (JET) before the D-T phase starts and the papers describe the calculation methods and the calculated response functions of this instrument. The response functions will be used for the unfolding of measured neutron energy distributions. <p> Paper 4 gives a detailed description of the D-D neutron time-of-flight spectrometer which was in use at JET for several years. The hardware, the software for the random correction and some typical neutron energy spectra measured at JET are presented and described. <p> Papers 5 and 6 describe an upgraded version of the D-D spectrometer which recently has been installed at JET. Paper 5 gives some experimental results from measurements of JET plasmas while paper 6 describes a Monte Carlo program simulating the neutron transport of this spectrometer. The calculated response functions have been used for the unfolding of the measured neutron energy spectra
Superior Mesenteric Artery Thrombectomy with Retrograde Aortomesenteric Bypass for Acute Thrombotic Mesenteric Ischemia
No full textSuperior Mesenteric Artery Embolectomy with Primary/Patch Closure for Acute Embolic Mesenteric Ischemia
No full textSuperior Mesenteric Artery Thrombectomy with Retrograde Aortomesenteric Bypass for Acute Thrombotic Mesenteric Ischemia
No full textSuperior Mesenteric Artery Thrombectomy with Retrograde Aortomesenteric Bypass for Acute Thrombotic Mesenteric Ischemia
No full text
Superior Mesenteric Artery Embolectomy with Primary/Patch Closure for Acute Embolic Mesenteric Ischemia
No full textSuperior Mesenteric Artery Embolectomy with Primary/Patch Closure for Acute Embolic Mesenteric Ischemia
No full text- …
