Comparison of adsorption behavior of multiple inorganic ions on kaolinite and silica in the presence of humic acid using the multitracer technique

This work involves a validation of the photon and electron transport of the GEANT4 particle simulation toolkit for radiotherapy physics applications. We examine the cross sections and sampling algorithms of the three electromagnetic physics models in version 4.6.1 of the toolkit: Standard, Low-energy, and Penelope. The depth dose distributions in water for incident monoenergetic and clinical beams are compared to the EGSNRC results. In photon beam simulations, all three models agree with EGSNRC to within 2%, except for the buildup region. Larger deviations are found for incident electron beams, and the differences are affected by user-imposed electron step limitations. Particle distributions through thin layers of clinical target materials, and perturbation effects near high-Z and low-Z interfaces are also investigated. The electron step size artifacts observed in our studies indicate potential problems with the condensed history algorithm. A careful selection of physics processes and transport parameters is needed for optimum efficiency and accuracy.

Accuracy of the photon and electron physics in GEANT4 for radiotherapy applications.

Simultaneous determination of stability constants of humate complexes with various metal ions using multitracer technique

This article describes an efficiency study of directional bremsstrahlung splitting (DBS) for x-ray tube modeling. DBS is shown to be up to five or six orders of magnitude more efficient at 50 or 135 kV tube potential than a simulation without splitting, and 60 times more efficient compared to uniform bremsstrahlung splitting. A methodology is presented to determine the optimum splitting number for a given situation using a second degree polynomial expression derived from theoretical considerations. Very large optimum splitting numbers are found for small fields (5 mm radius) at 1 m from the x-ray source, which are relevant for half-value layer (HVL) calculations and for simulations related to primary air kerma standards. Two approaches for the calculation of kerma at a plane and inside a volume using track-length estimation are implemented in BEAMnrc, a user-code from the EGSnrc Monte Carlo simulation system for photon and electron transport. A practical application of DBS to HVL calculations for a Comet MXR-320 x-ray tube is reported. The agreement with measured HVLs at different constant tube potentials is found to be better than 2.3%.

Efficient x-ray tube simulations.

We established “Multitracer”, a new versatile radiotracer technique, for simultaneous tracing of a number of elements in various chemical, environmental, and biological systems. Metal foil targets (typically Au, Ag, Ge, Cu and Fe) are irradiated with C, N, or O ions accelerated up to 135 MeV/nucleon by RIKEN Ring Cyclotron. Radiochemical procedures have been developed to remove the target material leaving the nuclides as Multitracer solutions containing various radionuclides of Be, Na, Mg, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, I, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Pt, and Hg. Multitracers enable efficient tracing of a number of elements, and comparison of their behavior under strictly identical experimental conditions. Such features will be demonstrated by means of an example of application to a model experiment for the study of removal mechanism of various elements from the ocean.

“Multitracer” a new tracer technique — Its principle, features, and application

An irradiation facility and a radiochemical procedure for preparing a radioactive multitracer solution are reported Gold foil was irradiated with 135 MeV/nucleon 14N-ion beam The foil was dissolved in aqua regia and precipitation of gold as metal with hydrogen peroxide yielded a carrier- and salt-free multitracer solution

Preparation of a Radioactive Multitracer Solution from Gold Foil Irradiated by 135 MeV/nucleon 14N Ions

Au, Ag, and Cu foils were irradiated with high-energy heavy ions accelerated by the RIKEN Ring Cyclotron. Each foil was dissolved in aqua regia or nitric acid. The target materials, Au, Ag, and Cu, were precipitated as metallic Au, AgCl, and CuSCN, respectively, and filtered out to yield carrier- and salt-free multitracer solutions containing a large number of radioactive nuclides

Preparation of radioactive multitracer solutions from Au, Ag, and Cu foils irradiated with high-energy heavy ions

A high mass-resolution TOF-ERDA system installed at RILAC of RIKEN is presented. The target chamber was designed for TOF-ERDA. A charged-particle detector and a time detector for TOF measurements were installed in the chamber. The data-acquisition system, comprising CAMAC modules, is controlled by a personal computer. The analysis of the spectra is performed off-line. The mass resolution of the system for masses of around A = 28 was evaluated to be 1.9. H, C, N and O in a PIQ film could be measured simultaneously, and the peaks of C, N and O were separated.

Development of a high mass-resolution tof-erda system for a wide mass range

A heavy noble gas ion beam sputtering (HIBS) technique was developed to prepare carbon stripper foils with a characteristic of long lifetime. The dependence of lifetimes on the mass of noble gas was also investigated. Compared with foils made by lighter ions such as Ne and Ar, the foils made by Kr and Xe noble gases were not so much stronger mechanically, but were long-lived under bombardment with a 3.2 MeV Ne+ ion beam 3 μA in intensity and 3.5 mm in diameter. The mean lifetime in the case of Kr sputtering gas was around 51 mC, 20 times longer than that of commercially available foils. The key point in producing long-lived foils with Kr or Xe noble gas ions was found to be to decrease the amount of oxygen contaminants as much as possible.

Minoru Yanokura

Papers

Preparation of a Radioactive Multitracer Solution from Gold Foil Irradiated by 135 MeV/nucleon 14N Ions

Preparation of radioactive multitracer solutions from Au, Ag, and Cu foils irradiated with high-energy heavy ions

Development of a high mass-resolution tof-erda system for a wide mass range

Development of heavy ion beam sputtering method for long-lived carbon stripper foils

Preparation of radioactive multitracer solutions from a high-energy heavy-ion irradiated au target by means of a supported liquid membrane