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The ion beam irradiation system based on the Metal Vapor Vacuum Arc (MEVVA) ion source has been developed at Korea Multi-purpose Accelerator Complex (KOMAC). The ion irradiation system consists of MEVVA ion source, ion irradiation chamber and sample stage along with the auxiliary systems such as power supplies, vacuum pumps, beam diagnostics and the control system. The initial beam test was carried out using the chromium ions after the system was installed. During stability measurement, peak beam current was measured to be 335 mA at the cathode voltage of 30 kV and its fluctuation was less than 5% in rms for 100 min. The beam extraction characteristic curve was measured depending on the arc power and cathode voltage from 30 to 60 kV. The beam profile was monitored through two different methods; multi-wire beam profile monitor and a small Faraday cup which measures the local current density along the radial direction. The results showed good agreements within 5%. The beam radius was measured depending on the arc power and a matched extraction condition of the ion source could be found. The average charge state of the beam was measured to be 2.18 which is an important parameter to specify the dose on the sample. The erosion rate of the cathode was found to be 34.2 μg/C.

This report reviews the overall status of the development and planning activities of compact accelerator-based neutron sources in Korea. For the last decade, the demand for the technology development and application of CANS has significantly increased, and becomes widely accepted by the science, engineering and industry sectors. Since the first technical workshop focused on CANS under the support of the Korea Nuclear Society in fall 2016, there have been numerous efforts to launch projects by several groups. Although unsuccessful, two CANS projects were newly launched in 2020. One is the 30-MeV cyclotron-based neutron source for industrial neutron imaging at the Korea Atomic Energy Research Institute (KAERI), and the other is the BNCT technology development at the Korea Institute of Radiological & Medical Sciences. A project proposal for an expansion of the proton LINAC facility at KAERI to 200 MeV for semiconductor irradiation testing through the produced neutron field is now almost complete and will be submitted to the government funding agency for review. The CANS project for BNCT based on the proton LINAC developed by the Dawonsys consortium is briefly described. The new neutron source based on electron LINAC is prepared by the Pohang Light Source laboratory, and the initial consideration and application targets are also described. A new strategic plan for national R&D on radiation technology and the enforcement of its infrastructure is still under way, and a more systematic approach to the development and application of neutron sources will be implemented through the strategic planning.

We have studied the feasibility of automatic and fast control of the low energy beam transport section in the newly developed radio-frequency quadrupole at KOMAC (Korea Multipurpose Accelerator Complex) by combining a simple neural network model with a beam profile monitor. Extensive beam dynamics simulations on the proton injector with varying beam transport parameters are performed to generate the training set for the machine learning and to obtain optimization model for the injector. These datasets are well-trained and show good ability to estimate the beam parameters at position under consideration. These results can be a steppingstone to develop an auto-tuning or feedback control system based on artificial intelligence for a high-intensity accelerator. This paper presents the calculation conditions and the training process in detail, as well as the cross-validation of the trained neural network model by using the results obtained by beam dynamics code.

Conventional magnetic resonance imaging (MRI) techniques cannot demonstrate microvascular alterations in mild Alzheimer's disease (AD). Thus, the diagnosis of microvascular pathology commonly relies on postmortem. The purpose of this study was to evaluate alterations of microvascular structures in patients with AD using a 3T clinical MRI system with a commercially available contrast agent.Eleven patients with AD and 11 cognitively normal (CN) controls were included in this cross-sectional prospective study. R2 and R2* relaxation rate changes (∆R2 and ∆R2*) before and after a Gadolinium (Gd)-based contrast agent injection were calculated from images obtained with a multi-echo turbo spin-echo sequence and multi-echo gradient-echo sequence to obtain microvascular index maps of blood volume fraction (BVf), mean vessel diameter (mVD), vessel size index (VSI), mean vessel density (Q), and microvessel-weighted imaging (MvWI). Two-sampleBVfs at the corpus callosum and at the thalamus were significantly increased in the AD group (P=0.024 and P=0.005, respectively). BVf at the gray matter (P=0.020) and white matter area (P=0.012) were also significantly increased in the AD group compared with the CN group. MvWIs at the hippocampus and parahippocampal gyrus were significantly increased in the AD group compared with the CN group (P=0.020 and P=0.006, respectively). Voxel-based analysis showed both mVD and VSI were significantly decreased at the prefrontal lobe in the AD group. Q were not significant difference between CN and AD groups. MvWI were significantly positively correlated with age.Microvascular index was a useful non-invasive method to evaluate microvascular morphology alteration. The microvascular morphology of AD was manifested as increasing BVf and microvessel-weighted.

This paper presents the experimental results of neutron spectra measurements with organic scintillators at the copper beam dump of the 100-MeV proton linear accelerator in the Korea Multi-Purpose Accelerator Complex (KOMAC). For the measurement of the fast neutrons generated by the proton-copper nuclear reaction, two organic scintillators made of a stilbene crystal and liquid EJ-309 combined with photomultipliers and fast digitizers were utilized. Both detectors were installed inside radiation shielding structures facing the conical-shaped 100-MeV proton beam dump. The neutron transport was calculated using two Monte-Carlo codes, MCNP6 and GEANT4, with a proper physical model and a nuclear data library, along with the appropriate consideration of the detailed geometrical factors in the vicinity of the beam-dump and the neutron detectors. Each pulse signal measured in the detectors was analyzed to identify whether it was induced by a neutron or a gamma-ray in a mixed radiation field by using pulse shape discrimination technique. For operation of beam current of 5 mA and duty of 0.2%, the neutron yield was measured to be approximately 9.0E+10 n/s, which was 23% smaller than the numerically estimated value. In addition, both the measured and the estimated neutron energy spectra were compared.

At the Korea Multi-purpose Accelerator Complex (KOMAC), a 100-MeV high-power proton linac has been used for proton-beam irradiation services for various applications and research programs, including material science, bio-medical science, semiconductor applications, as well as nuclear physics and basic science, since commissioning of the machine in 2013. Recently, demands for fast neutrons from users in the semiconductor industries are increasing to test the semiconductor device SER (soft error rate) or SEE (single event effect). At present, we provide pilot services to users with pulsed white-spectrum neutrons (max. neutron energy ∼100 MeV) generated at the beam dump, which is made of copper. However, the neutron energy should be increased at least to 200 MeV to meet international standards such as ISO26262 or JEDEC89A. For the upgrade of the linac energy to 200 MeV, we conducted a preliminary design study, including superconducting radio-frequency (SRF) based linac structure, a neutron generation target and a neutron utilization facility. The upgrade plan for the KOMAC linac, along with the preliminary results of the design study on the superconducting linac and neutron generation facility, will be given in this paper.

Neutron spectrum unfolding based on an artificial neural network (ANN) is a highly flexible and robust method that can be applied to any type of radiation detector and wide energy range of incident particles. In this study, we present details of neutron-spectrum deconvolution with well-established multilayer perceptron algorithms implemented in CERN ROOT with the aim of obtaining the incident neutron energy spectra for white neutron and mono-energetic beams with finite energy spreads. The ANN trained with experimental and simulation datasets successfully approximated incident neutron spectra with high accuracy for each case, indicating that a well-trained ANN has high potential for applications in radiation-related fields.

The beta-detected nuclear magnetic resonance (β -NMR) technique is a novel method that obtains depth-resolved information on samples by observing the asymmetric beta decay of nuclear probes. Although the beta-detected NMR has several advantages over the conventional NMR techniques, the number of user facilities in the world is severely limited. At the site of Korea Multi-purpose Accelerator Complex (KOMAC), we initiated a research project to develop a radioactive ion (RI) beam facility dedicated for the future beta-detected NMR facility at KOMAC based on a 100-MeV proton linear accelerator. In this endeavour, we developed a prototype of a target-ion-source (TIS) composed of low-Z production targets, target container, target heater, high-current feed through, and hot surface ion source. In recent on-line experiments, we have demonstrated that a Li-8 beam of the order of 106 pps could be extracted with the prototype design of the TIS. Here, we present the recent progress of the RI beam development study.

A test bench of the microwave ion source has been developed at Korea Multipurpose Accelerator Complex (KOMAC). Several modifications were done to improve the performance of the ion source. Beam properties such as an emittance and a profile were measured according to the operating parameters and extraction geometries. In this paper, the characteristics of ion source at test bench are presented in a viewpoint of the beam properties and the improvement of the ion source for 100 MeV linac based on the result is reported.

Fast neutrons with a broad energy spectrum, with which it is possible to evaluate nuclear data for various research fields such as medical applications and the development of fusion reactors, can be generated by irradiating proton beams on target materials such as beryllium. To generate short-pulse proton beam, we adopted a deflector and slit system. In a simple deflector with slit system, most of the proton beam is blocked by the slit, especially when the beam pulse width is short. Therefore, the available beam current is very low, which results in low neutron flux. In this study, we proposed beam modulation using a buncher cavity to increase the available beam current. The ideal field pattern for the buncher cavity is sawtooth. To make the field pattern similar to a sawtooth waveform, a multiharmonic buncher was adopted. The design process for the multiharmonic buncher includes a beam dynamics calculation and three-dimensional electromagnetic simulation. In addition to the system design for pulsed proton generation, a test bench with a microwave ion source is under preparation to test the performance of the system. The design study results concerning the pulsed proton beam generation and the test bench preparation with some preliminary test results are presented in this paper.

Korea Multi-purpose Accelerator Complex (KOMAC) has been operating 20 MeV and 100 MeV proton beam lines to provide proton beams for various applications since 2013. A new proton beam line of low-flux proton densities was constructed for space radiation effect testing in 2016, and the beam commissioning was completed in 2017. In this work, we introduce the new proton beam line and report the results of beam characterization. For the results, we conclude that the new beam line can provide a flux as low as 105 p/cm2/pulse with quality assurance, uniformity within ± 10% in a 100 mm × 100 mm irradiation area with various kinds of proton energies.

A beam line for radioisotope (RI) production was designed for the 100-MeV proton linear accelerator at Korea Multi-purpose Accelerator Complex (KOMAC). The specifications of the beam line are such that the energy is 100 MeV and the average current is 0.6 mA for a target size of 100 mm in diameter. The system consists of a beam transport system including a magnet, a vacuum system, beam diagnostics, power supplies and a control system. The key components of the system are the high-field 45 bending magnet, the beam scanning system and beam window. In this paper, the design of the beam line and its key components are presented.

Nickel nano-structured materials are synthesized by using a wire explosion in water. Based on an analysis of each step of the wire explosion, we propose insufficient energy deposition before a plasma restrike as the cause for the inclusion of coarse particles in the wire-explosion product. We confirmed that more energy, in excess of 30%, could be deposited by increasing the dwell time, which resulted from a compression of vapor by the surrounding water and from suppression of plasma restrikes. Because of an increased energy loss into the surrounding water, the specific energy increased by two-fold compared to a gas atmosphere. The synthesized nano-structured nickel showed a uniform particle size of 20 nm with a few coarse particles that were mainly metallic nickel with a little oxide and hydroxide phases. The possibility for large-volume production through a continuous explosion of 300 shots was confirmed.

A microwave proton source has been developed and is being used for 50-keV proton injection to the 20-MeV proton linac of the Proton Engineering Frontier Project (PEFP). It includes a 2-kW rf system for plasma generation. Because the rf system is electrically connected to a high-voltage beam extraction power supply, it is not easy to operate, control and maintain the rf system on the high-voltage platform. A 50-kV DC break has been developed on the waveguide between the proton source and the rf generator, and has been compared with the waveguide without the DC break. The results show the same operation performances, with very low radiation loss and no electrical breakdown, and will be helpful for easy operation and maintenance of the proton injector for the 100-MeV proton linac.

The Proton Engineering Frontier Project developed a 13-MHz pulsed, RF cavity for heavy-ion implanter applications. Typically, slow changes in the room temperature and the mechanical vibrations of the vacuum device may be primary sources of disturbances, and the accelerating cavity of the implanter may not be able to operate at the resonance frequency owing to disturbance effects. We need a voltage-controlled oscillator phased-locked loop circuit to make a control system that could suppress the disturbance effects; thus, the accelerating gradient of the cavity always reached a peak level for a given input power and coupling. An analog-circuit-based RF-frequency-tracking system was developed. Next, we obtained the optimal control parameters for the key control components. Finally, we measured the system performance between an open loop and a closed loop. The key point of the system design is to control the driving frequency that is used to operate the RF source by keeping the phase at around 0 degrees with respect to the resonance peak of the cavity. The experimental results showed that the fluctuations of the control loop error signal were suppressed by about a factor of 10. The presented feedback loop is implemented as a standard proportional controller. The loop p-gain is 120 k.

The beam position monitor (BPM) is an essential component for the PEFP 100-MeV linac's commissioning. A prototype stripline-type linac BPM was designed for this purpose. The electrode aperture is 20 mm in diameter, and the electrode is 25 mm long, so it can be installed between Drift Tube Linac (DTL)101 and DTL102, which is the shortest distance. One end of the electrode is connected to the Sub Miniature Type A (SMA) feed through for signal measurement, and the other end is terminated as a short. The signal amplitude of the fundamental component was calculated and compared with that of the second harmonic component. The designed BPM was fabricated and a low-power RF test was conducted. In this paper, the design, fabrication and low power test of the BPM for the PEFP linac are presented.

The microwave ion source has been operated as a proton injector for the 20-MeV proton linac. The microwave ion source consists of the 2.45-GHz microwave components, a solenoid magnet, a vacuum system, power supplies for beam extraction and bias electrodes, and a cooling system. The beam current was measured under various operating conditions by changing the gas flow rate, solenoid magnet current and microwave power in order to find optimum operating conditions. In this paper, the measurement results are presented, and the optimum conditions are discussed.

The properties of LTCC green sheets formed by the MLS-22 powder of NEG Inc. were investigated for acrylic binders with different PVB and Tg in the variation of temperature. The elongation of the green sheets showed large variation depending on the temperature, and was rapidly decreased near the Tg of the sheets. With the increase of the ratio of plasticizer/binder (P/B), large elongation of the sheets was observed due to the decrease of the Tg. In the stacking process of the multilayer ceramic, the optimal control of the temperature is highly required depending on the Tg of the binder and the ratio of P/Buniform coating.

A microwave ion source is used as an ion source for the 100-MeV proton accelerator at the Korea Multi-purpose Accelerator Complex (KOMAC). The specifications of the ion source are a 50-keV energy and a 20-mA peak current. The plasma is operated in the CW mode by using a magnetron, and the pulse beam is extracted using a semiconductor switch located in the extraction power supply. The beam characteristics were measured based on the pulse voltage and current. A test stand was also installed to study the beam characteristics of the ion source off-line. In this paper, the pulse beam characteristics of the ion source are presented, and the installation of the test stand is reported.

The diffusion properties of H+ in ZnO nanorods are investigated before and after 20 MeV proton beam irradiation by using 1H nuclear magnetic resonance (NMR) spectroscopy. Herein, we unambiguously observe that the implanted protons occupy thermally unstable site of ZnO, giving rise to a narrow NMR line at 4.1 ppm. The activation barrier of the implanted protons was found to be 0.46 eV by means of the rotating-frame spin-lattice relaxation measurements, apparently being interstitial hydrogens. High-energy beam irradiation also leads to correlated jump diffusion of the surface hydroxyl group of multiple lines at ~1 ppm, implying the presence of structural disorder at the ZnO surface.

The drift tube linac (DTL) is used to accelerate proton beams from 20 MeV to 100 MeV in the linear accelerator of the Proton Engineering Frontier Project (PEFP). The phase scan signature method is a common technique to determine the radio-frequency (rf) set point, including the rf amplitude and phase, in DTL tanks. In this work, we applied the phase scan method to the first tank of the PEFP’s DTL in order to study the procedure for determining the rf set point by using artificial experimental data generated by using the PARMILA code.

The 100-MeV proton linear accelerator (linac) for the Proton Engineering Frontier Project (PEFP) has been developed and will be installed at the Gyeong-ju site. For the linac, a total of 11 sets of RF systems are required, and the waveguide layout was fixed to install high-power RF (HPRF) systems. One of the important interfaces with the building construction is the high-power radio-frequency (HPRF) transmission line embedded in the tunnel, which is used to transmit 1-MW RF power to each cavity in the tunnel. The waveguide section penetrating into the linac tunnel was designed with a bending structure for radiation shielding, and the dependence of its voltage standing-wave ratio (VSWR) on the chamfer length of the bending was calculated. The HPRF transmission line was fabricated into a piece of waveguide to prevent moisture and any foreign debris inside the 2.5-m thick concrete block. Air leakage was checked with a pressure of 0.25 psig of nitrogen gas, and a maximum VSWR of 1.196 was obtained by measuring the vector reflection coefficients with the quarter-wave transmission section. In this paper, the design and the fabrication of the HPRF transmission line into the PEFP linac tunnel are presented.

The Proton Engineering Frontier Project (PEFP) 20-MeV proton linear accelerator is currently operating at the Korea Atomic Energy Research Institute (KAERI). The ion source of the 100-MeV proton linac needs at least a 100-hour operation time. To meet the goal, we have developed a microwave ion source that uses no filament. For the ion source, a remote control system has been developed by using experimental physics and the industrial control system (EPICS) software framework. The control system consists of a versa module europa (VME) and EPICS-based embedded applications running on a VxWorks real-time operating system. The main purpose of the control system is to control and monitor the operational variables of the components remotely and to protect operators from radiation exposure and the components from critical problems during beam extraction. We successfully performed the operation test of the control system to confirm the degree of safety during the hardware performance.

A microwave ion source with a permanent magnet solenoid has been developed as an ion source for industrial applications. The microwave ion source with a permanent magnet solenoid was designed and fabricated. It was installed in the experimental test setup with a 2-kW, 2.45-GHz RF generator. An argon plasma was generated easily without any ignition method, and argon ion beams, up to 7 mA with a 600-W RF power and a 40-kV extraction voltage, have been extracted.

A 20-MeV proton accelerator has been developed and tested at the Korea Atomic Energy Institute (KAERI) by the Proton Engineering Frontier Project (PEFP). Beam phase was measured at the end of the 20-MeV accelerator by using the beam position monitor (BPM) signal. The beam current and phase were measured by changing the relative RF phase between the 3-MeV radio frequency quadrupole (RFQ) and the 20-MeV drift; tube linac (DTL), and the results were compared with those simulated by using the PARMILA code. In tins paper, the beam phase measurement results are presented, and the phase scan results based on the normal operating condition are compared with the simulation results.

One of the PEFP (Proton Engineering Frontier Project) 100-MeV beam lines requires a large and uniform irradiation field of ±10% uniformity in the target area of 300 mm ◊ 300 mm. We studied the nonlinear optics method by using two octupole magnets in order to achieve a large uniform field at the target. We found that the particles can be uniformly distributed within ±10% in a 300 mm ◊ 300 mm irradiation field at the target. We also studied the conditions of the quadrupole and the octupole magnets to meet the requirement of a large and uniform irradiation field.

A 13 MHz Radio Frequency (RF) cavity for an RF implanter has been designed and fabricated at the Proton Engineering Frontier Project (PEFP). It consists of a coil having a circular cross-section, accelerating electrodes that are directly coupled to the beginning and the end of the coil, and a ground electrode for the inductor. The purpose of this paper is to explain the design concept and the measurement results for the RF properties of this cavity. A resonant frequency of 12.69 MHz with critical coupling and an unloaded quality factor of 1066 were achieved, agreeing well with the simulation results. The field distribution in the cavity was measured by using the bead-pull method. The field flatness is 6.5%, which satisfies the control requirements for the field in the cavity.

We studied the transverse beam dynamics including sextupole and octupole perturbations in a thermal wave model. A functional integration method was used to calculate the first order perturbation effects. We found that the model successfully explains a PARMILA simulation results for proton beams without space charge effects in a lattice with 10 FODO cells.

A 20-MeV proton accelerator has been developed and tested at the Korea Atomic Energy Institute (KAERI) by the Proton Engineering Frontier Project (PEFP). It consists of a 50-keV proton injector, a 3-MeV radio frequency quadrupole (RFQ), and a 20-MeV drift tube linac (DTL). The beam emttance was measured at the middle point between two solenoids of the proton injector. Based on the measured data, the beam properties through the proton injector were simulated using the T-step code for various operating conditions. Also, the transmission ratio through the RFQ was calculated using the output data obtained from the T-step code. In this paper, the emittance measurement results are presented, and the simulation results based on the measurement data are discussed.

The 100-MeV proton linear accelerator of the Proton Engineering Frontier Project (PEFP) has been developed and consists of a 3-MeV radio frequency quadrupole accelerator (RFQ), a 20-MeV drift tube linac (DTL), a medium energy beam transmitter (MEBT), and 100-MeV DTL tanks. The error of the accelerating field in the cavity should be within ±1◦ in phase and ±1% in amplitude, and the phase difference between adjacent cavities should be maintained continuously. To satisfy these requirements, high phase stability is required in the RF reference system for the PEFP lowlevel radio frequency (LLRF) control system. The RF reference system for the PEFP 100-MeV accelerator, which is composed of a local oscillator (LO), a rigid coaxial reference line of about 80-m length, Heliax cables, and LLRF analog components, was designed and its phase stability was evaluated. The reference signal was chosen to be the 300 MHz LO signal for phase stability of the LLRF control system. The phase noise of the local oscillator was measured and calculated as a phase error of 0.058 degrees. In the entire length of the RF reference distribution line, a phase stability of ±0.05 degrees was evaluated for a temperature change of ±0.1 ◦C. The phase stability of the LLRF analog system for up/down-conversion was also measured and depended on the temperature stabilization.

This work is related to the error analysis of the proton engineering frontier project (PEFP) beam lines. In order to evaluate the error e ects on the trajectory of the beam center, we used an error analysis code that included a rst-order perturbation of the translational and the rotational errors of the dipole and the quadrupole magnets in the beam lines. The distorted beam trajectory can be corrected by using corrector magnets. The speci cations of the correction dipoles are obtained by using an error correction algorithm that is included in the code.

Development of the Resonant-Frequency Monitoring System for the PEFP DTL Young-Gi Song, Han-Sung Kim, Hyeok-Jung Kwon and Yong-Sub Cho Proton Engineering Frontier Project, Korea Atomic Energy Research Institute, Daejeon 305-353 (Received 4 September 2008) A 20-MeV, 20-mA proton linac, which is comprised of a 50-keV proton injector, a 3-MeV radio frequency quadrupole (RFQ) and 20-MeV drift tube linac (DTL), has been developed in the Proton Engineering Frontier Project (PEFP). For a stable and e cient acceleration of a proton beam, the resonant frequency of the DTL cavities should be matched to the high power RF driving frequency. In PEFP DTL, a resonant control cooling system (RCCS) will be used to control the resonant frequency. The main objective of this study is to measure and transfer the resonance frequency error to the RCCS by measuring the RF eld pro le in the cavity. The algorithm derived by using a state-space model is used to represent the resonant frequency error. The control application program was developed with a VME-based PCI mezzanine card (PMC) extended board and a multitasking method based on the VxWorks. We tested the algorithm, the control board and the application program by using a dummy cavity. In this paper, the algorithm, the system con guration and the test results are presented. PACS numbers: 29.17.+w