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Boron–neutron capture therapy (BNCT) is a cancer treatment method that exploits the high neutron reactivity of boron. Monitoring the prompt gamma rays (PGs) produced during neutron irradiation is essential for ensuring the accuracy and safety of BNCT. We investigate the imaging of PGs produced by the boron–neutron capture reaction through Monte Carlo simulations of a gamma camera with a SrI2 scintillator and parallel-hole collimator. GAGG scintillator is also used for a comparison. The simulations allow the shapes of the energy spectra, which exhibit a peak at 478 keV, to be determined along with the PG images from a boron–water phantom. It is found that increasing the size of the water phantom results in a greater number of image counts and lower contrast. Additionally, a higher septal penetration ratio results in poorer image quality, and a SrI2 scintillator results in higher image contrast. Thus, we can simulate the BNCT process and obtain an energy spectrum with a reasonable shape, as well as suitable PG images. Both GAGG and SrI2 crystals are suitable for PG imaging during BNCT. However, for higher imaging quality, SrI2 and a collimator with a lower septal penetration ratio should be utilized.

Versatile high-power pulsed electron-beam accelerators that meet the requirements of pulsed high-power specifications are needed for appropriate applications in medical industry, defense, and other industries. The pulsed electron beam accelerator comprising a Marx generator and Blumlein pulse forming line (PFL) is designed to accelerate the electron beams at the level of 1 MeV when electrostatically discharging. The performance specifications of Marx generators consisting of a 100 kV DC power supply, R-L-C circuit, and high voltage switch are at a maximum 800 kV. At this time, by using the capacitance mismatching principle between the Marx generator and the Blumlein PFL under the law of preserving the amount of charge, it is possible to generate a high voltage in the form of a square pulse up to about 1.1 MV, as much as 1.37 times the charged voltage of the Marx generator. As a result, energy transmission from the Marx generator with a high efficiency of about 85% to the Blumlein PFL is possible. The aim of this study is that the pulsed high-power electron-beam accelerator can be used to change the diode impedance, and the energy of the accelerated electron beam reaches a level of 1 MeV with the square pulse width of about 100 ns at the flat-top in the range of relativistic electron beam generation. Performance tests were securely carried out by installing a dummy load based on CuSO4 solution varying the diode impedance to deter damage to the circuit by preventing reflected waves from being generated in the load.

Generally, as the operating frequency of the electromagnetic wave increases, the maximum output becomes smaller and the wavelength of the wave becomes smaller, so that the size of the circuit cannot but be reduced. Particularly, fabrication of a circuit with a high-power terahertz (THz) wave frequency band of kW or more is limited due to the problem of circuit size on the order of μm to mm. In order to overcome these limitations, this paper proposes a source design technique of 0.1THz-0.3GW levels with a cylindrical shape with a diameter of about 2.4cm. Modeling and computational simulation were performed to optimize the design of high power electromagnetic sources based on the Cherenkov radiation generation technology using the principle of plasma wake-field acceleration with ponderomotive force and artificial dielectrics. An effective design guideline has been proposed to facilitate the fabrication of large-power terahertz wave vacuum devices of large diameter that are less restricted in circuit size through objective verification.

A versatile digital Low-Level Radio Frequency (LLRF) system has been designed for the various energy cyclotrons being developed by Korea Institute of Radiological and Medical Sciences (KIRAMS). In this study, the contents of LLRF of $\pmb{8\mathrm{MeV}\sim 30\mathrm{MeV}}$ cyclotron, which is a typical circular accelerator for neutron capture therapy, are discussed. Here we present blue print to construct an effective LLRF control system of the cyclotron.

This experimental visualization study was conducted to investigate and define the phenomena of an initially pressurized liquid water target that can prevent the boiling of water when the target is irradiated with a 30-MeV proton beam produced using the MC-50 Cyclotron at Korea Institute of Radiological and Medical Sciences. At various initial pressures and proton beam currents, the behavior of the target water was investigated using a complementary metal-oxide-semiconductor camera. We confirmed that an appropriate initial pressure could indeed prevent local bulk boiling, and be determined by solving Rayleigh's equation and the Clausius-Clapeyron equation for homogeneous bubble growth using the measured bubble size generated at the Bragg-peak region. The saturation temperature of the initial pressure must be higher than the calculated local water temperature at the Bragg-peak region. The final pressure of the water target increased proportionally with the initial pressure and proton beam current. The penetration depth of the beam varied with beam current and slightly with the final pressure, as evidenced by the emission of blue light in all experimental cases.

In radiation therapy, the carbon beams has more advantages with respect to biological properties then a proton beam. The carbon beam has a high linear energy transfer (LET) to the medium and a higher relative biological effectiveness (RBE). To design the spread-out Bragg peak (SOBP) of biological dose for a carbon beam, we propose a practical method using the linear-quadratic (LQ) model and the Geant4-based Monte Carlo simulation code. Various Bragg peak profiles and LETs were calculated for each slice in the target region. To generate an appropriate biological SOBP, we applied a set of weighting factors, which are power functions in terms of energy steps, to each obtained physical dose. The designed biological SOBP showed a uniformity of 1.34%.

The active scanning technique is a pencil beam delivery method in particle therapy. The active scanning beam delivery system consists of a beam scanner, beam monitor, energy modulator, and related programs, such as the irradiation control and planning programs. A proposed prototype active scanning system was designed and installed on MC-50 at the Korea Institute of Radiological and Medical Science (KIRAMS) with a 45-MeV proton beam. The laminated magnetic yoke of the scanning magnet supported fast ramping. The beam intensity and the beam profile monitors were designed for measuring the beam’s properties. Both the range shifter and the ridge filter modulate the incoming beam energy. The LabVIEW®-based beam-irradiation-control program operates the system in a sequential operation manner for use with the MC-50 cyclotron. In addition, an in-housecoded irradiation-planning program generates an optimal irradiation path. A scanning experiment was successfully completed to print the logo of the Korea Heavy Ion Medical Accelerator (KHIMA) on GaF film. Moreover, the beam’s position accuracy was measured as 0.62 mm in the x-direction and as 0.83 mm in the y-direction.

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.

A klystron is an important vacuum device which is useful in medical linear accelerators because it amplifies the radio-frequency (RF) signals required to produce high-energy particle beams. The properties of the nonlinear input and output dynamics in the klystron circuit arouse distortion in various types of parameters pertaining to the beam voltage, beam current, RF power, and operating frequency from unpredictable external factors. Therefore, low-level RF (LLRF) control systems can facilitate the regulation of the output of the klystron to a desired level. Low-level RF control system of the klystron is designed to stabilize the applied voltage and control the resonance frequency of the cavity of the klystron. In this work, an infallible low-level RF control system, the most suitable for a klystron, is designed to use a beam monitoring and an interlock system with components that include an isolator and a phase shifter. Moreover, with regard to pulse distortion at the flap top at the RF output power, the stability of the RF power pulse at the flap top part was improved somewhat by a variable inductor which controlled the inside of the pulse modulator. In this LLRF control experiment, the pulse modulator generated 140kV-95A and succeeded in generating RF output power of 2.856GHz-6MW level of an S-band klystron. During this process, the efficiency of the RF power was approximately 42∼45% and the pulse repetition rate was 10 Hz. The flattop pulse width was measured and found to be 1 µs.

A control system of the 14.5 GHz electron cyclotron resonance (ECR) ion source has been designed and developed in KHIMA(Korea Heavy Ion Medical Accelerator) project which will use C6+ ions for heavy ion therapy. Production of the selected ion beam in stable operation with safety is a development goal with flexibility by easy access and modification which are necessary during development process with an accelerator. The control system of the ECR ion source system consists of electric control cabinet (ECC) as hardware and main control program (MCP) as software, respectively. ECC developed to manage power and control flow with electric components and controllers controls the injection system, RF system, high voltage & extraction system, analyzing system, vacuum system, cooling system, diagnosis system and safety system. MCP is the supervisory program developed for effective automation and data acquisition by LabVIEW-based graphical programming. The isolated network from a control computer to ECC and bleeder resistors in a steel plate box composed by the simulation result for high voltage power supplies increase reliability and safety. The performance of the developed control system has been verified successfully by beam extraction of C4+ ion from CO2 as main gas and He as support gas through an analyzing magnet and a faraday cup with the acquired spectrum at the control system. After optimization with C4+ ions, measurement of characteristics of C6+ ions including emittance of the ion beam will be planned early 2013. Also, quantity of C6+ ions in the same charge to mass ratio will be estimated by using 13CO2 as main gas and He as support gas.

The Korea heavy ion medical accelerator (KHIMA) project is developing and constructing the heavy ion medical accelerator for the first time in Korea since 2010. This paper describes the status of high energy beam transfer line (HEBT), which connects the superconducting cyclotron to the treatment rooms. The HEBT provides a patient with 145–430 MeV/u carbon (12C6+) beam to cure cancer. The HEBT is consisted of 6 beam lines (4 horizontal, 1 vertical and 1 oblique). The size of the design HEBT is 41 m in length, 11 m in width and 17 m in height. Total number of magnets is 53 for focusing magnets and 22 for bending magnets. In the description, the current design status of the HEBT is described.