Tsuyoshi Hamano

SPICE-NIRS microbeam: a focused vertical system for proton irradiation of a single cell for radiobiological research.

The Single Particle Irradiation system to Cell (SPICE) facility at the National Institute of Radiological Sciences (NIRS) is a focused vertical microbeam system designed to irradiate the nuclei of adhesive mammalian cells with a defined number of 3.4 MeV protons. The approximately 2-μm diameter proton beam is focused with a magnetic quadrupole triplet lens and traverses the cells contained in dishes from bottom to top. All procedures for irradiation, such as cell image capturing, cell recognition and position calculation, are automated. The most distinctive characteristic of the system is its stability and high throughput; i.e. 3000 cells in a 5 mm × 5 mm area in a single dish can be routinely irradiated by the 2-μm beam within 15 min (the maximum irradiation speed is 400 cells/min). The number of protons can be set as low as one, at a precision measured by CR-39 detectors to be 99.0%. A variety of targeting modes such as fractional population targeting mode, multi-position targeting mode for nucleus irradiation and cytoplasm targeting mode are available. As an example of multi-position targeting irradiation of mammalian cells, five fluorescent spots in a cell nucleus were demonstrated using the γ-H2AX immune-staining technique. The SPICE performance modes described in this paper are in routine use. SPICE is a joint-use research facility of NIRS and its beam times are distributed for collaborative research.

Single particle irradiation system to cell (SPICE) at NIRS

Selective irradiation by an ionizing particle of a targeted cell organelle may disclose such mechanisms as signal transaction among cell organelles and cell-to-cell communication in the processes toward an endpoint observed. Bystander effect, existence of which has been clearly evidenced by application of the particle microbeam to biological experiments, suggests potential deviation from the conventional risk estimation at low particle fluence rates, such as in an environment of space radiation in International Space Station. To promote these studies we started the construction of a microbeam facility (named as SPICE) by using our HVEE Tandem accelerator (3.4 MeV proton and 5.1 MeV 4 He 2þ ). For our primary goal, ‘‘irradiation of cell organelle with a single particle with a position resolution of 2 l mi n a reasonable irradiation time’’, special features are considered. Usage of a triplet Q-magnet for focussing the beam to micrometer levels is an outstanding feature compared to facilities of other institutes. Other features are almost similar to those of other institutes. Those are precise position control of a cell dish holder, design of the cell dish, data acquisition of microscopic image of a cell organelle (cell nucleus), data processing, reliable particle detection, soft and hard wares to integrate all these related data and system to control and irradiate a targeted spot with exactly determined number of particles.

DEVELOPMENT OF DROPLET-PIXE SYSTEM FOR ENVIRONMENTAL MONITORING SAMPLES

PIXE is a trace analytical method. During the sample preparation process for PIXE analysis, there may be loss of element due to sublimation or evaporation that must be considered for quantitative analysis. To avoid such problems, suitable droplet PIXE system has been developed for determination of elemental abundances of liquid samples in atmospheric condition. The system has several dripping modes in order to enhance advantage of dripping method over static liquid target method. The droplet-PIXE system has been applied to a few case studies. Its advantages over other PIXE system will be discussed in this paper.

Development of target system for intense neutron source of p-Li reaction.

A target cooling system was developed for an intense neutron source of p-Li reaction. The system consists of target cooling devices and protection devices for lithium evaporation. A pin-structure cooling device was developed to enhance cooling power. Functional graded material was utilized for the evaporation of lithium. Test experiments were performed by using the neutron exposure accelerator system for biological effect experiments (NASBEE) at the National Institute of Radiological Sciences (NIRS) in Japan. The target system was confirmed to be applicable for accelerator-based boron neutron capture therapy.

DIAGNOSIS OF SPATIAL RESOLUTION FOR MICROBEAM SCANNING PIXE USING STIM METHOD AND CR-39 TRACK DETECTOR IN PASTA

In PIXE analysis system and Tandem Accelerator facility (PASTA) of NIRS, we are using Scanning Transmission Ion Microscopy (STIM) method and solid track detector to diagnose the spatial resolution of scanning microbeam PIXE analysis system. These methods are widely used by many microbeam facilities.

Neutron Exposure Accelerator System For Biological Effect Experiments (NASBEE)

The neutron exposure accelerator system for biological effect experiments (NASBEE) was developed to study biological effects of fast neutrons. We have characterized the NASBEE neutron beams with neutron energy spectrum, absorbed dose energy distributions, and space distributions. The neutron energy spectrum shows 2.3 MeV as mean energy and 3.0 MeV as kerma of tissue‐equivalent‐plastic (A150) weighted mean energy, and the maximum neutron energy was determined to be 9 MeV. Neutron absorbed doses occupy 82% of the NASBEE neutron beam. NASBEE has been used to learn some of the outcomes of the biological effects of fast neutrons.

ELEMENTAL ANALYSIS OF ATMOSPHERIC PARTICLES COLLECTED ON POLYTETRAFLUOROETYLENE (PTFE) FILTER USING IN-AIR HELIUM ION INDUCED X-RAY EMISSION METHOD

In order to confirm the availability of an in-air Helium ion induced X-ray emission method for multi-elemental analysis of polytetrafluoroetylene (PTFE) filter sample containing atmospheric particles, NIST urban particulate matter (SRM 1648) collected on PTFE filter using a special small chamber was analyzed by an in-air PIXE method with Helium ions and a proton beam. In addition, we analyzed 10 elements, mixing a standard solution with different concentrations to confirm detection sensitivity of characteristic X-ray peaks. As a result, it is suggested that 1) elements that are lighter than Zn and Pb can be satisfactorily measured using the in-air Helium ion induced X-ray emission method if the amount contained in the filter sample is at least 0.1 mg/L, i.e., 15 ng/cm2, 2) the in-air Helium ion induced X-ray emission method is useful as a method for quantitatively analyzing the light elements such as Mg, Al, Si, S and Cl that are important for identifying the behavior and characteristics of atmospheric particles from the PTFE filter sample containing atmospheric particles, and 3) in the case of the PTFE filter sample containing atmospheric particles, it is possible to measure elements from Mg to Pb by means of analysis using Helium ions and protons.

Micro-PIXE analysis system at NIRS-electrostatic accelerator facility for various applications

A micro-PIXE analysis system based on the ion beam analysis system by Oxford Microbeams Ltd. has been developed at the NIRS-electrostatic accelerator facility. The introduction of the CdTe X-ray detector dramatically improved the detection efficiencies for heavy elements that are important in the life sciences and environmental science. This system has been used for various projects and has provided several meaningful results, thus establishing the micro-PIXE system as an effective tool for the determination of elemental distribution with a high spatial resolution. In this paper, outline of the features of the micro-PIXE system at NIRS along with its recent application in research are introduced.

L Band EPR Tooth Dosimetry for Heavy Ion Irradiation

Electron Paramagnetic Resonance (EPR) tooth dosimetry is being developed as a device to rapidly assess large populations that were potentially exposed to radiation during a major radiation accident or terrorist event. While most exposures are likely to be due to fallout and therefore involve low linear energy transfer (LET) radiation, there is also a potential for exposures to high LET radiation, for which the effect on teeth has been less well characterized by EPR. Therefore, the aim of this paper is to acquire fundamental response curves for high LET radiation in tooth dosimetry using L band EPR. For this purpose, we exposed human teeth to high energy carbon ions using the heavy ion medical accelerator in Chiba at the National Institute of Radiological Sciences. The primary findings were that EPR signals for carbon ion irradiation were about one-tenth the amplitude of the response to the same dose of 150 kVp X-rays.

Total Ionizing Dose Effects in Carbon Nanotube Network Transistors

Total ionizing dose effects on carbon nanotube network transistors were experimentally evaluated using 60Co gamma-ray irradiation up to 50 kGy(Si). The electrical characteristic of the devices after irradiation are reported for future space applications.