Beam Irradiation System Research Articles

Development of Beam Irradiation System for Life Science Research at RAON

Development of Beam Irradiation System for Life Science Research at RAON

A simulation study of MR-guided proton therapy system using iron-yoked superconducting open MRI: a conceptual study.

Radiotherapy platforms integrated with magnetic resonance imaging (MRI) have been significantly successful and widely used in X-ray therapy over the previous decade. MRI provides greater soft-tissue contrast than conventional X-ray techniques, which enables more precise radiotherapy with on-couch adaptive treatment planning and direct tracking of moving tumors. The integration of MRI into a proton beam irradiation system (PBS) is still in the research stage. However, this could be beneficial as proton therapy is more sensitive to anatomical changes and organ motion. In this simulation study, we considered the integration of PBS into the 0.3-T superconducting open MRI system. Our proposed design involves proton beams traversing a hole at the center of the iron yoke, which allows for a reduced fringe field in the irradiation nozzle while maintaining a large proton scan field of the current PBS. The shape of the bipolar MRI magnets was derived to achieve a large MRI field-of-view. To monitor the beam position and size accurately while maintaining a small beam size, the beam monitor installation was redesigned from the current system. The feasibility of this system was then demonstrated by the treatment plan quality, which showed that the magnetic field did not deteriorate the plan quality from that without the magnetic field for both a rectangular target and a prostate case. Although numerous challenges remain before the proposed simulation model can be implemented in a clinical setting, the presented conceptual design could assist in the initial design for the realization of the MR-guided proton therapy.

Development of proton beam irradiation system for the NA65/DsTau experiment

Tau neutrino is the least studied lepton of the Standard Model (SM). The NA65/DsTau experiment targets to investigate Ds , the parent particle of the ντ , using the nuclear emulsion-based detector and to decrease the systematic uncertainty of ντ flux prediction from over 50 % to 10 % for future beam dump experiments. In the experiment, the emulsion detectors are exposed to the CERN SPS 400 GeV proton beam. To provide optimal conditions for the reconstruction of interactions, the protons are required to be uniformly distributed over the detector's surface with an average density of 105 cm-2 and the fluctuation of less than 10%. To address this issue, we developed a new proton irradiation system called the target mover. The new target mover provided irradiation with a proton density of 1.01 × 105 cm-2 and the density fluctuation of 1.9 ± 0.3% in the DsTau 2021 run.

In situ single particle characterization of the themoresponsive and co-nonsolvent behavior of PNIPAM microgels and silica@PNIPAM core-shell colloids

Poly(N-isopropylacrylamide) (PNIPAM) microgels and PNIPAM colloidal shells attract continuous strong interest due to their thermoresponsive behavior, as their size and properties can be tuned by temperature. The direct single particle observation and characterization of pure, unlabeled PNIPAM microgels in their native aqueous environment relies on imaging techniques that operate either at interfaces or in cryogenic conditions, thus limiting the observation of their dynamic nature. Liquid Cell (Scanning) Transmission Electron Microscopy (LC-(S) TEM) imaging allows the characterization of materials and dynamic processes such as nanoparticle growth, etching, and diffusion, at nanometric resolution in liquids. Here we show that via a facile post-synthetic in situ polymer labelling step with high-contrast marker core–shell Au@SiO2 nanoparticles (NPs) it is possible to determine the full volume of PNIPAM microgels in water. The labelling allowed for the successful characterization of the thermoresponsive behavior of PNIPAM microgels and core shell silica@PNIPAM hybrid microgels, as well as the co-nonsolvency of PNIPAM in aqueous alcoholic solutions. The interplay between electron beam irradiation and PNIPAM systems in water resulted in irreversible shrinkage due to beam induced water radiolysis products, which in turn also affected the thermoresponsive behavior of PNIPAM. The addition of 2-propanol as radical scavenger improved PNIPAM stability in water under electron beam irradiation.

Development of a direct point electron beam exposure system to investigate the biological functions of subcellular domains in a living biological cell

Electron microscopy studies have demonstrated that the diameter of a focused electron beam is small enough to probe or manipulate subcellular domains of a single biological cell. Here, we report the development of a direct point electron beam irradiation system to investigate the biological functions of subcellular domains in a living cell. Subcellular structures of a single living cell cultured on a thin film can be selectively irradiated by the point electron beam generated by our system. We have demonstrated controlled beam positioning capability to selectively irradiate 500 nm size structure with a point electron beam. We determined beam irradiation parameters that did not cause irreversible plasma membrane perforation after beam exposure and the irradiation caused intracellular Ca2+ elevation in an irradiated neuronal cell. Since the neuronal cell express fine subcellular structures such as neurites, we tried to position a beam on the structure and observed a Ca2+ wave originated from the intended point, which showed that our system had enough selectivity to target a subcellular structure. Point electron beam exposure is expected to be employed for various cellular stimulation protocols, and this enables the investigation of the biological functions of subcellular domains.

Beam Loss Studies at the High Energy Beamlines of the RAON Accelerator

The RAON accelerator is currently under construction to generate and accelerate stable ions and rare isotopes for various kinds of scientific programs, and it will be completed by the end of 2021. In the RAON accelerator, the beams generated by using ion sources such as electron cyclotron resonance ion source and isotope separation on-line can be used in high energy experiments such as a beam irradiation system and a muon spin rotation/relaxation/resonance system after having been accelerated by low energy and high energy superconducting linacs. After the high energy superconducting linac, the beam passes through the high energy beamline and then collides with the target. In 2015, the lattices of the high energy beamlines were designed achromatically to minimize the emittance growth. However, as the specification of magnets in the beamline was changed after first lattice design, a beam dynamics simulation has been performed newly, and beam loss studies have also been conducted. Here, we will present the simulation results for the beam dynamics and describe the beam loss studies performed on the high energy beamlines of the RAON accelerator.

Development of a Wide Dose-Rate Range Electron Beam Irradiation System for Pre-Clinical Studies and Multi-Purpose Applications Using a Research Linear Accelerator

Development of a Wide Dose-Rate Range Electron Beam Irradiation System for Pre-Clinical Studies and Multi-Purpose Applications Using a Research Linear Accelerator

Improving transport and optimizing deceleration of ion beams from electron cyclotron resonance multicharged ion sources.

Electron cyclotron resonance ion sources (ECRISs) are widely applied for ion beam applications, e.g., plasma processing, cancer therapy, and ion engine of an artificial satellite. In our ECRIS, we aim at producing and extracting various ion beams from this device, in particular, Xeq+ ion beams at low energy. In the aerospace engineering field, there are problems of accumulated damages on various component materials caused by low energy of Xe ions from the engine. There are not enough experimental sputtering data for satellite materials at the Xeq+ in the low energy region. Then, we are trying to investigate the sputtering yield experimentally by irradiating the low energy Xe ion beams. To perform this experiment, it is necessary to acquire a certain amount of beam current with low energy. Then, we generate the low energy ion beams by the following steps: First, the ion beams are extracted from the ECRIS at high voltage. Next, these are transported to an ion beam irradiation system (IBIS). Finally, the ion beams are decelerated by the deceleration voltage in the IBIS. We adjusted the beamline. We measure the characteristics of the transport efficiency and decelerated ion beam currents. In this paper, we describe the experimental setup using an existing ECRIS for decelerated heavy ion beams and the results of decelerated ion beam currents.

Current status of experimental facilities at RAON

The Rare Isotope Science Project (RISP) was established in December 2011 for the construction of the accelerator complex RAON (Rare isotope Accelerator complex for ON-line experiments) which will be used for the rare isotope science in Korea. The rare isotope accelerator at RAON will provide both stable and rare isotope (RI) beams with an energy range from a few keV to a few hundreds of MeV per nucleon for research in the fields of basic and applied sciences.At the moment, there are 7 experimental facilities considered at RAON: KOrea Broad acceptance Recoil spectrometer and Apparatus (KOBRA) and Large Acceptance Multi-Purpose Spectrometer (LAMPS) for nuclear physics, High Precision Mass Measurement System (HPMMS) with Multi-Reflection Time-of-Flight (MR-ToF) and Collinear Laser Spectroscopy (CLS) for nuclear physics using atomic physics techniques, Nuclear Data Production System (NDPS) for nuclear reaction data, Muon Spin Rotation/Relaxation/Resonance (μSR) for material science, and Beam Irradiation System (BIS) for bio-medical science.In this paper, the current status including detail design and research goal of 7 experimental facilities at RAON will be discussed.

Development of proton beam irradiation system for small animals using FFAG accelerator

To evaluate the biological effect of boron compounds on normal tissues in boron neutron capture therapy, it is necessary to compare the radiation effects of neutron irradiation and gamma ray irradiation on small animals in nonclinical studies. Neutron beams and gamma rays are difficult to collimate; thus, it is impossible to administer a dose on each part of the normal tissues of small animals. Therefore, we have developed a method to compare biological effects by irradiating neutrons and gamma rays after irradiating a proton beam to the point just before the threshold dose at which the biological effects occur. We aim to develop an irradiation field that irradiates proton beams locally using a fixed-field alternating-gradient (FFAG) accelerator and a small ridge filter.An aluminum scatterer, transmission dose monitor, ridge filter, range shifter, collimator, and a proton beam from the FFAG accelerator were used to form an irradiation field with a spread out Bragg peak (SOBP) with a length of 10 mm and a size of 10 mm2.Dose measurement was performed using a Gafchromic film and an ionization chamber. The irradiation system was simulated using the PHITS Monte Carlo simulation code, and simulation results were compared with experimental results.We succeeded in forming an irradiation field with a dose rate of 14.3 ± 0.24 Gy/min, an SOBP length of 10 mm, and a size of 10 mm2.

RF System of Linear Accelerator for Natural Rubber Research

The natural rubber research is ongoing project at the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The project aims to use electron beam irradiation for high quality vulcanization process for natural rubber. The main accelerator system consists of a DC thermionic electron gun, 5-cell linear accelerator structure, control system, RF system and electron beam irradiation system. This accelerator system aims to generate adjustable electron beam energy range from 0.5 to 4.0 MeV with pulse current of 10 – 100 mA and pulse repetition rate of 20 – 200 Hz. The 4 MeV electron beam with current of 100 mA produced at pulse repetition rate of 200Hz is expected to achieve the maximum absorbed dose of 320 Gy. The control system is designed and built in-house to fit the accelerator system requirement. The RF system consists of Pulse Forming Network (PFN), trigger board and thyratron switch, pulse transformer and pulse magnetron. This RF system can achieve RF power of 0.9 to 2.0 MW with pulse width of 4 μs. The pulse repetition rate can be varied from 20 to 200 Hz to control RF average power. The performance of RF system as well as the results of RF commissioning will be present and discussed.

Study on Penetration of 4-MeV Electron Beam in Natural Rubber Latex

Vulcanization with electron beam irradiation provides unique and high efficient processing for natural rubber latex. It is one of very interesting and effective industrial applications of particle accelerators. A radio-frequency (RF) linear accelerator (linac) and electron beam irradiation system have been developed for natural rubber vulcanization at the PBP-CMU Electron Linac Laboratory of the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University (CMU). This accelerator will be able to produce electron beams with maximum energy up to about 4 MeV. In this research, we used a Monte Carlo simulation program called GEANT4 to study transportation of 4-MeV electron beam with Gaussian transverse distribution through a vacuum window, an air gap and natural rubber latex. The vacuum window is made of 50-micron titanium foil and the natural rubber was placed 18 cm downstream the foil exit. Simulations of electron depth dose and transverse distribution in these media were conducted. In addition, calculation on the irradiation throughput was performed. The study results revealed that for the electron beam with Gaussian transverse distribution and an average energy of 4.06 MeV, the irradiation area should be 2.8 mm×2.8 mm with the depth of 8 mm. With this condition, the irradiation time of 0.02 second will provide the dose of at least 50 kGy per irradiated point, which is enough for the rubber vulcanization process. The overall irradiation throughput rate is 6.865 kg/hr.

Design of dual flattening filter for 4-MeV electron beam irradiation system

A 4-MeV electron radio-frequency linear accelerator (RF linac) at the Plasma and Beam Physics Research Facility is used to irradiate electron beam on the natural rubber latex for vulcanization process. The irradiation area and uniformity of electron dose have significant influence on the vulcanization quality and throughput. This research focuses on the design of electron beam flattening filter to enlarge the transverse beam size with more uniform energy and dose distribution. The flattening filter system consists of two different filters. The primary one is used to increases the transverse beam size while the secondary one is used to modify the beam for achieving more uniform transverse distribution. Optimization of the filter system was performed for 4 MeV electron beam by using the GEANT4 Monte Carlo simulation program. The initial electron beam has a pencil shape with transverse Gaussian distribution and an RMS radius of 2 mm. The optimized parameters of the filters are thickness, shape and position. The results of the optimization suggest that the primary filter should have high atomic number. The tantalum (Ta) sheet with a thickness of 30 micron was chosen. The material and shape of the secondary filter were also studied. It is found that the aluminium (Al) plate with a shape of the truncated cone can smear the beam to uniformly distribute over the irradiating area. The output of this work can be used to construct the flattening filter system in the electron beam irradiation system for increasing the vulcanization throughput.

Synthesis of Diamond‐Like Carbon Films Deposited by the Ionization Vapor Method and Development of its Semiconductive Devices Fabricated by the Focused Ga Ion Beam Implantation

SUMMARYIn this study, we have attempted to synthesize the Gallium (Ga)‐implanted diamond‐like carbon (DLC) film for new functional devices as substituting Si‐based materials. Intrinsic‐DLC (i‐DLC) films (energy gap: 1.45 eV) were deposited by the ionization vapor method with applying the negative pulsed bias voltage (frequency: 2 kHz, duty ratio: 30%, peak voltage: 500 V) to SiO2 substrates. Ga atoms were implanted to i‐DLC films as accepters utilizing by focused ion beam irradiation system. The Raman scattering spectra of i‐DLC and Ga‐DLC films showed typical DLC characteristics which consisted of I(D) and I(G) peaks. In order to evaluate working function of the Ga‐DLC film, several electrode materials (Au, Pt, Cu, Al, and Sn) were deposited on the films. Current–voltage characteristics of Au and Pt electrodes on Ga‐DLC films showed Ohmic contacts, and Cu, Al, and Sn electrodes were Schottky contacts. These results suggested that a work function of the Ga‐DLC film was in the range of 4.47 eV to 4.58 eV. To apply these contact properties to DLC semiconductive devices, we produced the DLC Schottky diode using Al and Pt electrodes deposited on the Ga‐DLC film. A current–voltage characteristic of DLC Schottky diode showed diode property in which amount of forward and backward voltage were 7.0 V and 17.0 V, respectively. The ideality factor n of produced diode was 11.3.

Conceptual Design of Scanning Magnets for Superconducting Proton Therapy Facility

The performance of scanning magnets is the key to the treatment of proton accelerator in nozzle of the Superconducting Proton Therapy System (SPTS), which directly affects the quality of the proton beam and the size of the radiation field. The scanning magnets set at the entrance of the beam irradiation system are two dipole magnets to scan the beam in both horizontal and vertical directions and form the irradiation field to be tumor shape. In this paper, the theoretical calculation and software simulation have carried out to design scanning magnets for the SPTS in brief. The distribution of magnetic field is improved by structure optimization of scanning magnet and comparative analysis of magnetic induction intensity distribution curve in medium plane. The optimum structures of scanning magnets are got, which can meet the beam integral field uniformity and improve scanning accuracy. The study provides the key technical support to proton therapy of the SPTS.

Energy deposition evaluation for ultra-low energy electron beam irradiation systems using calibrated thin radiochromic film and Monte Carlo simulations.

For evaluation of on-site dosimetry and process design in industrial use of ultra-low energy electron beam (ULEB) processes, we evaluate the energy deposition using a thin radiochromic film and a Monte Carlo simulation. The response of film dosimeter was calibrated using a high energy electron beam with an acceleration voltage of 2 MV and alanine dosimeters with uncertainty of 11% at coverage factor 2. Using this response function, the results of absorbed dose measurements for ULEB were evaluated from 10 kGy to 100 kGy as a relative dose. The deviation between the responses of deposit energy on the films and Monte Carlo simulations was within 15%. As far as this limitation, relative dose estimation using thin film dosimeters with response function obtained by high energy electron irradiation and simulation results is effective for ULEB irradiation processes management.

Alignment of liquid crystal molecules on solution-derived zinc-tin-oxide films via ion beam irradiation

We present the characteristics of annealing temperature-dependent, zinc-tin-oxide (ZTO) films deposited by a solution process for application in liquid crystal displays (LCDs). ZTO surfaces supported homogeneously-aligned liquid crystal (LC) molecules based on an ion beam irradiation system. Uniform LC alignment and a precise pretilt angle were obtained at an annealing temperature greater than 300 °C. The oxidation of ZTO films was confirmed using field-emission-scanning electron microscopy and X-ray photoelectron spectroscopy. The electro-optical characteristics of electrically controlled birefringence (ECB) cells based on the ZTO films were superior to those based on polyimide. Especially, IB-irradiated ZTO films exhibited superior performance with respect to response time. This result indicates that this approach will allow for the fabrication of advanced LCDs with high performance.

Development of mobile electron beam plant for environmental applications

Due to the necessity of pilot scale test facility for continuous treatment of wastewater and gases on site, a mobile electron beam irradiation system mounted on a trailer has developed. This mobile electron beam irradiation system is designed for the individual field application with self-shielded structure of steel plate and lead block which will satisfy the required safety figures of International Commission on Radiological Protection (ICRP). Shielding of a mobile electron accelerator of 0.7MeV, 30mA has been designed and examined by Monte Carlo technique. Based on a 3-D model of electron accelerator shielding which is designed with steel and lead shield, radiation leakage was examined using the Monte Carlo N-Particle Transport (MCNP) Code. Simulations with two different versions (version 4c2 and version 5) of MCNP code showed agreements within statistical uncertainties, and the highest leakage expected is 5.5061×10−01 (1±0.0454) μSv/h, which is far below the tolerable radiation dose limit for occupational workers. This unit could treat up to 500m3 of liquid waste per day at 2kGy or 10,000Nm3 of gases per hour at 15kGy.

Combined treatment of swine wastewater by electron beam irradiation and ion-exchange biological reactor system

Swine wastewater was treated using an ion-exchange biological reactor after an electron beam irradiation. Organic matter and nutrient in swine wastewater were pre-treated by an electron beam irradiation. The optimal dose for the solubilization of organic matter in swine wastewater ranged from 20kGy to 75kGy. To investigate solubilized organic fraction of swine wastewater, carbohydrates, proteins and lipids were measured. Most solubilized organic matter was proteins and lipids. The maximum chemical oxygen demand (COD) removal efficiency was 85.1% at an organic loading rate of 1.41kg/m3day (75kGy). For the removal of nitrogen, the nitrogen removal was significantly affected by the current density. The maximum total nitrogen removal efficiency was 75.0% at 1.09A/m2. On the other hand, amorphous phosphorus precipitation was formed in the IEBR because calcium ions competed highly with magnesium.

Ridge filter design for a particle therapy line

The beam irradiation system for particle therapy can use a passive or an active beam irradiation method. In the case of an active beam irradiation, using a ridge filter would be appropriate to generate a spread-out Bragg peak (SOBP) through a large scanning area. For this study, a ridge filter was designed as an energy modulation device for a prototype active scanning system at MC-50 in Korea Institute of Radiological And Medical Science (KIRAMS). The ridge filter was designed to create a 10 mm of SOBP for a 45-MeV proton beam. To reduce the distal penumbra and the initial dose, [DM] determined the weighting factor for Bragg Peak by applying an in-house iteration code and the Minuit Fit package of Root. A single ridge bar shape and its corresponding thickness were obtained through 21 weighting factors. Also, a ridge filter was fabricated to cover a large scanning area (300 × 300 mm2) by Polymethyl Methacrylate (PMMA). The fabricated ridge filter was tested at the prototype active beamline of MC-50. The SOBP and the incident beam distribution were obtained by using HD-810 GaF chromatic film placed at a right triangle to the PMMA block. The depth dose profile for the SOBP can be obtained precisely by using the flat field correction and measuring the 2-dimensional distribution of the incoming beam. After the flat field correction is used, the experimental results show that the SOBP region matches with design requirement well, with 0.62% uniformity.