Y. Namito - Academia.edu (original) (raw)

Papers by Y. Namito

Applied Radiation and Isotopes, 1993

A parallel plate free-air ionization chamber was filled with air, nitrogen and argon, and the ion... more A parallel plate free-air ionization chamber was filled with air, nitrogen and argon, and the ionization current was measured for 30-keV monoenergetic incident photons, using a synchrotron radiation source. The photon intensity was measured using a total absorption calorimeter placed behind the chamber. Because the W value for each gas is accurately known, photon mass energy-absorption coefficients for each gas were measured. The measured coefficients are in agreement with published tables by Hubbell within 2%.

Health Physics, 1995

A Monte Carlo code EGS4 expanded for low energy photon transport was validated by measuring absor... more A Monte Carlo code EGS4 expanded for low energy photon transport was validated by measuring absorbed doses in a phantom for 30 and 10 keV monoenergetic photons from synchrotron radiation. Using the EGS4 code, depth doses at 0.07 mm, 0.02 to 0.1 mm, and 10 mm in the ICRU slab phantoms were calculated for 1.5 to 50 keV photons using the updated photon cross section data PHOTX. The results show that the doses at 0.02 to 0.1 mm below 10 keV are practical indices of effective dose as calculated by others, based on the 1990 ICRP recommendations (1991).

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1991

A total absorption calorimeter was developed to measure the absolute intensity of monoenergetic X... more A total absorption calorimeter was developed to measure the absolute intensity of monoenergetic X-ray beams from 10 keV to 70 keV of synchrotron radiation. Experiments with synchrotron radiation have demonstrated that the heat power above about 1 +W due to monoenergetic synchrotron radiation is measured with an accuracy of about 1%.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1995

A previously developed total-absorption calorimeter was improved by replacing a thermostated air ... more A previously developed total-absorption calorimeter was improved by replacing a thermostated air bath by a vacuum chamber in order to reduce the applicable photon energy up to several keV, and to extend the measurable photon intensity up to about 10 W of synchrotron radiation. The calorimeter maintained linearity over the power range from about 10 p.W to a few W within 0.1%. Experiments with monoenergetic and white-spectrum photons have proven the designed performance. in which the heat power due to monoenergetic photons was measured within an uncertainty of 3%. and the heat power due to white-spectrum photons was up to about 2 W.

We have performed a comparison of an electron backscattering coefficient between experiments and ... more We have performed a comparison of an electron backscattering coefficient between experiments and calculations. Electron backscattering coefficients η were measured previously for a few keV to tens of MeV mono-energetic electrons on targets of Z=4 to 92 materials. We calculated the η using Monte Carlo codes as EGS5, EGSnrc, PENELOPE and ITS3.0, and compared with the experiments. Those codes uses Goudsmit-Sounderson scattering model for a multiple scattering, and considers spin relativistic effect. For Al, Cu and U target, EGS5, EGSnrc and PENELOPE calculations were agree within about 10%, and ITS3.0 calculation was lower than other calculations in whole. In addition, the η was calculated using EGS5 code with applying spin relativistic effect to GS model (Spin-GS) and Molière model (Spin-Molière) and ignored spin relativistic effect to Molière model (NoSpin-Molière). The η of those models and the experiments agreed within 25% for Cu target and 16% for U target, respectively. The η using the Spin-GS and the Spin-Molière were nearer the experiments than that using the NoSpin-Molière for several hundred keV to 20 MeV.

2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515), 2003

ABSTRACT There are several well-known and widely-used simulation packages. However, comparing bet... more ABSTRACT There are several well-known and widely-used simulation packages. However, comparing between different simulation tools often raises controversial issues. Geant4 has rich flexibility and expansibility brought by its Object-Oriented approach, especially in adding physics processes. We can use Geant4 as a framework and plug-in the part of physics processes of other packages as Geant4 modules. In this paper, we focused on interfacing EGS4 with Geant4. EGS4 is one of the most wellknown simulation packages for electromagnetic physics. Taking advantage of the capability of Geant4 as a framework, we developed a plug-in interface for using EGS4 as a module of Geant4 physics process. This is useful and important for making comparisons between EGS4 and Geant4 especially in users' application level. In this paper, we describe our approach of design and implementation of the interface, and the results of basic benchmarks are also presented.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010

We incorporated the Landau-Pomeranchuk-Migdal (LPM) effect and the dielectric suppression effect ... more We incorporated the Landau-Pomeranchuk-Migdal (LPM) effect and the dielectric suppression effect for bremsstrahlung and the LPM effect for pair production in the EGS5 code. To verify the validity of the EGS5 code with the LPM plus dielectric cross section for bremsstrahlung, we compared the bremsstrahlung spectrum calculated using this code with that obtained considering the LPM effect. The values calculated using the EGS5 code reproduced the experimental value of the LPM effect well.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1993

A modification to the general-purpose Monte Carlo electron-photon transport code EGS4 [Nelson, Hi... more A modification to the general-purpose Monte Carlo electron-photon transport code EGS4 [Nelson, Hirayama and Rogers, was made in order to include linear polarization in the simulation of photon scattering . Both the Compton and Rayleigh scattering routines were modified to property account for the electric-field vector of the photon . This vector is calculated at each photon scatter, and is passed along with the photons in the radiation transport, thereby allowing for a precise simulation of polarized multiple scattering . A simulation of the absorbed-dose distribution in a soft tissue equivalent phantom for a linearly polarized incident photon beam, scattering many times, was successfully performed

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994

A modification to the general-purpose Monte Carlo electron-photon transport code EGS4 [1] was mad... more A modification to the general-purpose Monte Carlo electron-photon transport code EGS4 [1] was made in order to include Doppler broadening of Compton-scattered photon energy due to electron pre-collision motion. The Compton-scattered photon energy is sampled from a cross section formula based on the Compton profile, and the Compton scattering is sustained if the energy imparted to the electron is less than its binding energy. The electron binding effect modifies the scattered photon energy, angular distribution, and total cross section of the Compton scattering, and affects the photon mean free path used in the calculations. In the improved EGS4 code, all of these electron binding effects in Compton scattering are treated consistently. A simulation of 40 keV photon scattering by C and Cu samples was performed using the improved EGS4 code; the calculated scattered photon spectra agreed well with the measurements.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1990

Electrons that are IOSI from the beam during nom-A operation of a synchrotron radiation source an... more Electrons that are IOSI from the beam during nom-A operation of a synchrotron radiation source and during a beam dump at the end of 1 mn produce both ionizing radiation and neutrons. This radiation has the potentirl oi damaging sensitive maxials. in particular those that ne:rd to be very close to the beam. In the ~1, 'ooiers and undulators for the .Wxnced Light Source (ALS) 31 LBL. magnetic materials such 3s the veq-high-performance neodymium-iron-boron uill be 3s close 3s I cm 3wny from the electron beam during operation. TINS mxctial. which is preferred because of its high rcmsnsnce. is known 'o be more sensitive IO radiation than some other magnetic m;ltcrisls. Simple energy loss estimates and the EGSJ code were used to estimztr the radiation levels in the ALS insertion devices in the regions of the magnetic mzmxi~ls. The radiation levels were estimated for both aluminum and stanless steel vacuum chambers to determine if one would provide significantly better shis!ding. \Vs conclude that SVd-Fe-B can be used in the ALS insertion devices and that there is little difference in the radiation levels for aluminum 2nd stainless steel vacuum vessels.

Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 2001

This report consists of vugraphs concerning the EGS4 code system. It begins with a brief history ... more This report consists of vugraphs concerning the EGS4 code system. It begins with a brief history of EGS codes. Then a description of the EGS4 code system is given including: (1) how it is organized and the physics within it; (2) basic features of the code; and (3) mechanics of running the code. It concludes with a discussion on benchmarks.

On-board experiments were carried out in a spent-fuel shipping vessel, the Pacific Swan, in which... more On-board experiments were carried out in a spent-fuel shipping vessel, the Pacific Swan, in which 13 casks of TN-12A and Excellox 3 were loaded in five holds, and neutron and gamma-ray dose rates were measured on the hatch covers of the holds. Before shipping those casks, dose rates were also measured on the cask surfaces, one by one, to eliminate

Integral shielding experiments using iron-polyethylene slab shields were carried out to determine... more Integral shielding experiments using iron-polyethylene slab shields were carried out to determine an optimum arrangement for the neutron dose rate. The total thickness of the iron slabs was fixed at 32 cm, while several thicknesses of polyethylene slabs were employed as a parameter. Some measured data were analyzed by the Mone Carlo code MORSE-CG with the splitting technique.

We have performed a mono-energetic X-ray (8 keV and 20 keV) scattering experiment at a BL-14C bea... more We have performed a mono-energetic X-ray (8 keV and 20 keV) scattering experiment at a BL-14C beam line in KEK Photon Factory. Photons scattered with Al, Si, Ti, Fe, Cu, C and Ag target were measured with a silicon PIN photo detector located at θ =9 0 ◦. The measured data were compared with calculations using EGS5 code. The calculations and the measured data for K-X and L-X peak agreed within 11%, and those for Compton peak agreed within 8%.