Nobuhiro Kikuzawa

Proposal of Nondestructive Radionuclide Assay Using a High-Flux Gamma-Ray Source and Nuclear Resonance Fluorescence

A nondestructive assay system for radioactive waste management is proposed. The system utilizes nuclear resonance fluorescence triggered by a quasi-monochromatic high-flux gamma ray generated from the Compton scattering of laser photons by relativistic electrons. We employ an energy-recovery linac as an electron source and a mode-locked fiber laser followed by a laser supercavity as a photon source. The combination of these novel technologies realizes a gamma-ray flux much higher than existing sources using electron storage rings. The proposed gamma-ray source produces a quasi-monochromatic gamma ray with a flux of 1010/s/keV, which is high enough for industrial applications such as the nondestructive analysis of radionuclides in nuclear waste and the interrogation of fissile material in cargoes. The nuclear resonance fluorescence triggered by quasi-monochromatic gamma rays provides a versatile method of nondestructive analysis of both radioactive and stable nuclides.

Nondestructive Detection of Heavily Shielded Materials by Using Nuclear Resonance Fluorescence with a Laser-Compton Scattering γ-ray Source

We perform a proof-of-principle experiment for a nondestructive method for detecting the elemental and isotopic composition of materials concealed by heavy shields such as iron plates with a thickness of several centimeters. This method uses nuclear resonance fluorescence (NRF) triggered by an energy-tunable laser-Compton scattering (LCS) γ-ray source. One-dimensional mapping of a lead block hidden behind 1.5-cm-thick iron plates is obtained by measuring an NRF γ-ray of a lead isotope 208Pb. We observe a 5512-keV γ-ray from 208Pb excited by the quasi-monochromatic LCS γ-rays with energies up to 5.7 MeV. The edge position of the lead block is consistent with the exact position within the uncertainty.

Nondestructive detection of hidden chemical compounds with laser Compton-scattering gamma rays

A nondestructive assay method for measuring a shielded chemical compound has been proposed. The chemical compound is measured by using a nuclear resonance fluorescence (NRF) measurement technique with an energy tunable laser Compton-scattering (LCS) gamma-ray source. This method has an advantage that hidden materials can be detected through heavy shields such as iron plates of a thickness of several centimeters. A detection of a chemical compound of melamine, C(3)H(6)N(6), shielded by 15-mm-thick iron and 4-mm-thick lead plates is demonstrated. The NRF gamma-rays of (12)C and (14)N of the melamine are measured by using the LCS gamma-rays of the energies of up to 5.0 MeV. The observed ratio ((12)C/(14)N)(exp)=0.39+/-0.12 is consistent with (C/N)(melamine)=0.5.

Status of the JAERI FEL - beam test for injection system

Abstract The injection system of the JAERI superconducting linac for far infrared FEL oscillation was installed and commissioned. The characteristics of the electron beam measured, so far, are as follows: an electron beam of 100 mA with 4 ns bunch length was extracted from the gun at the accelerating voltage of 180–220 kV. The beam was compressed tentatively to less than 70 ps at the end of the transport line by preliminary operation of both the sub-harmonic buncher and the buncher.

Nondestructive identification of isotopes using nuclear resonance fluorescence

Nondestructive identification of heavy isotopes concealed in a thick iron box has been demonstrated by using nuclear resonance fluorescence. A quasi-monochromatic photon beam produced by the collision of laser quanta with high energy electrons was used for resonant excitation of nuclear levels in (206)Pb and (208)Pb. By measuring the resonant γ rays emitted from (206)Pb and (208)Pb, each of these isotopes were clearly identified. The ratio of the effective thickness, i.e., concentration distribution, of these isotopes was deduced from the relative intensities of the measured nuclear resonance fluorescence strengths.

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.

Performance of the LaBr 3 (Ce) scintillator for nuclear resonance fluorescence experiment

Performance of the LaBr3(Ce) scintillator for nuclear resonance fluorescence (NRF) experiment was investigated. Linearity and energy resolutions of the LaBr3(Ce) scintillator of 3 inch in diameter × 3 inch in thickness were measured using NRF scattering gamma ray from 208Pb (5.5 MeV and 7.3 MeV) and 24Mg (10.7 MeV). The linearity of the output for the gamma ray energy was less than 1 % and the energy resolution of the scintillator in keV was almost proportional to the square root of the gamma ray energy up to 10.7 MeV.

JAERI quasi-cw, and high-average power free electron laser driven by a superconducting rf linac

Abstract We have developed and constructed a prototype for a quasi-cw, and high-average power free electron laser driven by a superconducting rf linac at the Japan Atomic Energy Research Institute (JAERI), Tokai. We have successfully demonstrated expected performances of the JAERI 250 keV electron gun and bunching system, and completed an extension to an old 5.5 MV electrostatic accelerator building as an FEL accelerator vault in the 1991 Japanese fiscal year. All solid state rf amplifiers, liquid He refrigerators, a hybrid undulator and vacuum pumping stations are ready for use now. The first superconducting accelerator module is now under preparation for a cold rf test, and the other three modules are now under assembly. A description and the latest results of the JAERI superconducting rf linac FEL will be discussed, and reported in detail.

Two-Dimensional Isotope Imaging of Radiation Shielded Materials Using Nuclear Resonance Fluorescence

A novel method for two-dimensional (2D) imaging of a specific isotope in a material, which is hidden by a thick radiation shield is presented. Nuclear resonance fluorescence and the laser Compton scattering are used in the present method. We measured γ-rays of 5512 keV from the nuclear resonance fluorescence of 208Pb at several points, and obtained a 2D image of isotope distribution.

Design concept for the second phase project of the JAERI free electron laser facility

Abstract We present a conceptual design of the second phase project of the JAERI FEL facility. The FEL project is planned with the electron beam accelerated by low-frequency superconducting cavities to accomplish high average output laser power. While in the first phase the project the FEL wavelength is in far infrared region, in the second phase it is planned to ge in the near-infrared or shorter range.