Hani Negm

Non-destructive inspection system for special nuclear material using inertial electrostatic confinement fusion neutrons and Laser Compton Scattering Gamma-rays

A study of a non-destructive inspection system for hidden special nuclear materials in the cargo container at the sea port has been carried out under a promotion of Japan Science and Technology. This inspection system consists of an active neutron detection method for a fast screening purpose and a nuclear resonance fluorescence (NRF) method for isotope identification. The inertial electrostatic confinement fusion device has been developed for a neutron source and two neutron detection methods, the Feynman-alpha method and high energy neutron detection method, have been examined to realize the fast screening system. Generation of a quasi-monochromatic gamma-ray beam from the laser Compton Backscattering by using a compact microtron electron accelerator and an NRF experiment on uranium target using a new type of scintillation detector, LaBr3(Ce), has been studied to realize the isotope identification system.

Analysis of SNIP Algorithm for Background Estimation in Spectra Measured with LaBr3: Ce Detectors

LaBr3:Ce scintillating detectors exhibit excellent properties for γ-ray spectroscopy such as high energy resolution and operation under room temperature as well as MHz counting rates. On the other hand, sever background radiations exist due to the internal contamination of radioactive materials that are very difficult to be avoided during the manufacture. To decrease the effect of these background levels, some analytical techniques, e.g. background subtraction, should be applied. In the present work, we investigate the efficiency of the sensitive nonlinear iterative clipping peak (SNIP) method for background estimation and subtraction. Optimization of the clipping window is discussed for range of energy up to 3 MeV. Enhancement of energy resolution up to 50% was obtained.

Nuclear Resonance Fluorescence of 235U Measured with High-Resolution LaBr3(Ce) Scintillation Detectors

A nuclear resonance fluorescence (NRF) experiment was performed on a 235U target with quasi-monochromatic γ-rays at the High Intensity γ-ray Source (HIγS) facility using a 1733 keV resonant energy. A LaBr3(Ce) detector array consisting of eight cylindrical detectors, each with a length of 7.62 cm and a diameter of 3.81 cm, was implemented in this measurement. Moreover, a high-purity germanium (HPGe) detector array consisting of four detectors, each of which has a relative efficiency of 60%, was used as the benchmark for the measurement taken using the LaBr3(Ce) detector array. The integrated cross section of the NRF level, measured with LaBr3(Ce) detectors, showed good agreement with the available data.

Experimental demonstration of mode-selective phonon excitation of 6H-SiC by a mid-infrared laser with anti-Stokes Raman scattering spectroscopy

Mode-selective phonon excitation by a mid-infrared laser (MIR-FEL) is demonstrated via anti-Stokes Raman scattering measurements of 6H-silicon carbide (SiC). Irradiation of SiC with MIR-FEL and a Nd-YAG laser at 14 K produced a peak where the Raman shift corresponds to a photon energy of 119 meV (10.4 μm). This phenomenon is induced by mode-selective phonon excitation through the irradiation of MIR-FEL, whose photon energy corresponds to the photon-absorption of a particular phonon mode.

Study on detector geometry for active non-destructive inspection system of SNMs by nuclear resonance fluorescence

An active non-destructive detection system for special nuclear materials (SNMs) such as 235U has been developed for container inspection at sea ports. The SNMs can be detected by using nuclear resonance fluorescence (NRF) with a quasimonochromatic gamma-ray beam provided from a laser Compton Scattering (LCS) source. We have studied the optimum geometry for the detector array by Monte Carlo simulation code, GEANT4, which has been modified to take into account all physical processes in NRF. The simulation code has been checked by the experimental data taken in New-SUBARU and HIgS facility. NRF yield at different scattering angles were examined with different thickness of 235U target. The result shows that the backward angle is the optimum geometry for NRF detection in terms of NRF yield and S/N ratio caused by atomic scattering. Realistic simulation for a container cargo has been performed. Detector array of 100 LaBr3(Ce) detectors has been examined with 3 different size of crystals. Consequently, we can demonstrate the ability of the proposed inspection system.

Monte Carlo simulation of response function for LaBr 3 (Ce) detector and its internal-activity

Lanthanum halide scintillator LaBr3(Ce) could potentially improve the performance of spectroscopic systems because of their fine energy resolution in comparison with traditional scintillator materials and a good linearity of the energy response. Monte Carlo simulation of a detector response function presents a very challenging problem especially in 2 MeV region where internal radioisotopes inside the LaBr3(Ce) crystal make the energy response complex structure. The detector response functions of LaBr3(Ce) (38.1 mm × 76.2 mm cylindrical) have been calculated for standard γ-ray sources and internal sources using simulation toolkit GEANT4. The internal activity was investigated in details by comparison simulation results with the experimental. As a result we can reproduce the experimental spectra, however, there is still a few missing sources around 2 MeV region.

Feasibility of LaBr 3 (Ce) detector to measure nuclear resonance fluorescence from special nuclear materials

A nuclear resonance fluorescence (NRF) experiment was performed on a 235U target with the quasi-monochromatic γ-ray at High Intensity γ-ray Source (HIγS) using the 1733 keV resonant energy. A LaBr3(Ce) detector array consisting of 8 cylindrical detectors, each has length of 7.62 cm and a diameter of 3.81 cm, in diameter was implemented in this measurement. Moreover, high purity germanium (HPGe) detector array consisting of 4 detectors each has a relative efficiency of 60 %, was used as a benchmark for the measurement taken by LaBr3(Ce) detector array. The integrated cross-section of the NRF level measured with LaBr3(Ce) detector showed good agreement with the available data. Consequently, LaBr3(Ce) detector could be feasible to use as a detector for the special nuclear material inspection system.

Performance of LaBr 3 (Ce) array detector system for non-destructive inspection of special nuclear material by using nuclear resonance fluorescence

A LaBr3(Ce) detector array has been constructed for the non-destructive inspection of special nuclear materials (SNMs) using the nuclear resonance fluorescence (NRF) technique. The fundamental performance of the LaBr3(Ce) detector array, the proper data acquisition system and the analysis system are demonstrated. The developed LaBr3(Ce) array is shown to have a good energy resolution and an excellent energy linearity. The feasibility of using the LaBr3(Ce) array for the inspection system has been investigated by measuring the NRF integrated cross section for exciting the 1.73 MeV state in 235U.

Beam test of the coaxial cavity for the thermionic triode type RF gun

The KU-FEL (Kyoto University Free Electron Laser) facility uses an S-band 4,5 cell thermionic RF gun as an electron source. The gun is strongly suffering from back-bombarding effect. In order to mitigate the energy of back streaming electrons the used RF gun shall be modified to triode type. For this reason a RF driven pre-bunching small coaxial cavity should be attached to the main 4,5 cell gun. The coaxial cavity was designed and fabricated. We report here results of a hot test of the coaxial cavity.

Wide range automatic energy calibration of LaBr 3 :Ce detectors by the self-activity lines

A real-time automatic energy calibration (RAEC) algorithm of a LaBr3:Ce scintillation detector array has been developed. The energy markers for this calibration are the self-activity lines inherently existing inside the LaBr3 crystal. Five energy markers were used in this technique. Two lines are from the radioactive isotope of lanthanum, 138La, at 789 and 1436 keV while the other three are from the 227Ac which is thought to be the source of the self-activity of LaBr3 detectors near 2 MeV energy range. The energy calibration extracted from RAEC algorithm is evaluated by a comparison with the energy calibration that was established using 56Co radioactive checking source. The two energy calibrations showed a good agreement, indicating a high potential to use the self-energy calibration technique for LaBr3:Ce detectors.