Korea Multi-purpose Accelerator Complex Research Articles

Study on scintillation properties and proton-induced radiation damage of LaCl[formula omitted] crystals

A Cs2LiYCl6 (CLYC) scintillation crystal is a promising candidate for fast neutron spectroscopy due to its dual mode gamma/neutron capability and good energy resolution. Despite promising features, CLYC’s limited radiation tolerance and inability to separate alpha/proton particles using pulse shape discrimination (PSD) method restrict its applicability in fast neutron spectroscopy. The significant cross-sections for 35Cl(n,p)35S and 35Cl(n, α)32P reactions make 35Cl-containing crystals attractive candidates for fast neutron detection, prompting their development as a promising new solution. This study reports the growth of LaCl3 crystals via the Bridgman technique, enabling further exploration of their scintillation and material properties for fast neutron detection applications. The effects of the proton irradiation on LaCl3 crystals were investigated by irradiating them with a 100 MeV proton beam at the Korea Multi-purpose Accelerator Complex. The study quantified radiation damage by comparing the pre- and post-irradiation scintillation properties and PSD of the LaCl3 crystals. The results of the measurements demonstrate that LaCl3 crystals are promising candidates for applications in fast neutron identification, spectroscopy, and space mission, maintaining performance even under high-radiation environments.

Production cross sections of radionuclides in the proton induced reactions on natural iron with the proton energy of 57 MeV

The production cross sections of 55,56,57Co, 52gFe, 52g,54Mn, 51Cr, and 48V from the natFe (p,x) reactions were measured using a proton energy of 57 MeV at the Korea Multi-purpose Accelerator Complex (KOMAC) in Gyeongju, Korea. The conventional stacked-foil activation method and offline γ-ray spectroscopy were used to determine the excitation functions of proton induced nuclear reactions on iron. The measured excitation functions were compared with experimental data in literature and theoretical data from the TENDL-2021 library. The present data show generally good agreement with other experimental data, but discrepancies were found between the present data and the excitation functions of the TENDL-2021 library in the investigated energy range, except for 56,57Co and 54Mn.

Three-dimensional measurement of a proton beam profile at KOMAC with a scintillating fiber detector

The time structure of proton beam pulses has been measured using a three-dimensional beam profile monitor (BPM) with scintillating fibers at the Korea Multi-purpose Accelerator Complex (KOMAC). The BPM measured the spatial and temporal distributions of 100-μs-long macropulses at the 20-MeV and 100-MeV proton beamlines. The scintillating fiber BPM covers an effective area of 120(x)×120(y) mm2, with 12 fibers separated by 10 mm in each direction. Signals from 1-mm-diameter fibers were read out with a 1.3×1.3mm2 multi-pixel photon counter (MPPC) and fed into a 500-MHz flash ADC. We successfully measured the beam profile and its time structure at the same time. Using multi-layered collimators, the beam intensity could be sufficiently reduced so that the BPM could measure individual beam particles.

Mn2+ doping inside glass substrate utilizing metal ion beam implantation technique

The Korea multi-purpose accelerator complex (KOMAC) has been providing metal ion beam services such as Cr+, Fe+, Co+, Cu+, Mg+ and Ni+ using a modified Bernas ion source for diverse users. In this study, metal ion implantation facilitated by KOMAC has been utilized to implant Mn+ ions into a glass substrate. First, phosphate glass substrate doped with CeBr3 was fabricated following melt-quenching technique and then Mn+ ion beam was irradiated with flounces of 5 × 1016 ions/cm2. The irradiated sample was heat-treated at 400 °C, and characterized by absorption, excitation, and emission spectra. The presence of Mn2+ and the existence of energy transfer from Ce3+ to Mn2+ were explored by characteristic emission and excitation spectra. The emission intensity of Mn2+ was significantly higher when excited by Ce3+ excitation than Mn2+.

Operational status of and upgrade plan for the 100-MeV proton linac at the Korea multi-purpose accelerator complex.

The report presents the operation status of and upgrade plan for the 100-MeV proton linac at the Korea Multi-purpose Accelerator Complex (KOMAC). First, an operation history of the 100-MeV linac since its commissioning in 2013, such as operation hours, user services, machine availabilities, and downtimes, is discussed. Second, the status of the beamlines in service or under development is described in a detailed manner. Finally, the Korea Spallation Neutron Source (KSNS), which is part of the upgrade plan for the 100-MeV proton linac to expand its utilization fields, is discussed.

Beam test of the ion beam facility based on the metal vapor vacuum arc ion source at Korea multi-purpose accelerator complex

Beam test of the ion beam facility based on the metal vapor vacuum arc ion source at Korea multi-purpose accelerator complex

100-MeV KOMAC Proton Accelerator at Gyeongju: Operational Status and Upgrade Plan

In 2012, the Korea Multi-purpose Accelerator Complex (KOMAC) facility with a total construction budget of about $300M was constructed at Gyeongju in Korea. It has a 75 m long 100 MeV proton accelerator, which can supply the highest average beam current of 1.6 mA. Since 2013, the KOMAC has been operating the 100 MeV proton accelerator for the official user beam service with two multi-purpose beamlines, one at 20 MeV and the other at 100 MeV. In 2015, the first new high-flux beamline was constructed for a medical isotope production, and the second new beamline was added in 2016 to provide a low-flux proton beam irradiation service mainly for research on the effects of radiation on semiconductors, spacecraft parts, and medical/biological samples. By the help of recent increased usages of Korean semiconductor manufacturing companies, such as SAMSUNG and SK hynix, the competition rate for requesting beam time of the proton accelerator was increased as high as 3.54:1 in 2020. To support various research fields with good user satisfaction, we have been preparing to increase the beam energy of the proton accelerator from 100 MeV to at least 500 MeV. In this article, we describe the construction history, current operational status, and various applications of the KOMAC proton accelerator and its future upgrade plan.

Measurement of the Neutron Energy Spectra by Using Organic Scintillators at the Beam Dump of the 100-MeV Proton Linear Accelerator in the KOMAC

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.

Upgrade Plan of the KOMAC Proton Linac for the Atmospheric Radiation Test on Semiconductor Devices

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.

Ti+ and Mg+ Ion Beam Extraction from the Modified Bernas Ion Source

The korea multi-purpose accelerator complex (KOMAC) has a metal-ion-beam irradiation facility (150 keV/1 mA) equipped with a Bernas ion source. Metal-ion beams such as Cr+, Fe+, Co+, and Cu+ have been successfully extracted from our facility. Recently, some research groups have requested us to irradiate Ti+ and Mg+ ions into materials. These two kinds of ions have never been provided before. In response to these requests, we carried out the extraction of Ti+ and Mg+ beams at our facility. The vaporization temperatures of TiCl(III) and MgCl(II) under a pressure of 10−4 Torr were less than 300 °C and more than 600 °C, respectively. In this study, optimal extraction conditions for Ti+ and Mg+ ion beams were acquired successfully. To confirm the fluences of the Ti+ and the Mg+ beams, we prepared a silicon wafer sample and a gallium nitride (GaN) sample. Ti+ ions were irradiated with a current density of ∼6 μA/cm2 onto a silicon wafer sample for 90 min, and the dose was 1.68 × 1016 ions/cm2, we measured by using Rutherford backscattering spectrometry (RBS) analysis. Mg+ ions implanted in GaN were confirmed by using secondary ion mass spectroscopy (SIMS). The depth and the concentration of Mg+ ions at the peak were found to be 130 nm and 7.4 × 1019 ions/cm3, respectively. We would expect the newly extracted Ti+ and Mg+ ions to be helpful for research in the fields of material science and condensed matter physics.

Characterization Study of Fast Neutron Sources Based on Proton Accelerators at KOMAC

We introduce two neutron sources based on proton accelerators; a quasi monoenergetic neutron source driven by a 1.7 MV tandem accelerator and a pulsed white neutron source based on a 100 MeV linear proton accelerator, which are installed at Korea Multi-purpose Accelerator Complex (KOMAC) of Korea Atomic Energy Research Institute (KAERI). The neutron sources are characterized in terms of Monte Carlo simulations, and experiments based on various type of detectors and activation methods. In the manuscript, specifications of the neutron sources and the partial results of characterization study including energy and flux density measurements of the neutron sources are presented.

Beam characterization of the low-flux proton beam line at KOMAC for application to radiation effect testing

Abstract 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.

Status and Utilization of the Beam Facility at KOMAC

Korea Multi-Purpose Accelerator Complex (KOMAC) has been supporting a user beam service using 20- and 100-MeV proton beam facilities since the second half of 2013, and recently, beam facilities for radioisotope production and a low-flux proton beam have been built. A 100-MeV low-flux proton beam facility was constructed in 2007, which was due to the strong requirements of users in various R&D fields, such as space radiation, medical/biology, and radiation detectors. For the low-flux beam facility, the compact modules for beam flux control were designed, and various beam diagnosis tools were installed in the target room. In the process room, a user-friendly measurement system, consisting of DC power supplies, electrometers, NIM modules, was designed for data processing and acquisition. In addition, the ion beam facilities based on gas and metal ion sources provide an ion implantation service. In particular, beam analysis services, such as PIXE and RBS, have been started using the tandem accelerator. Moreover, analysis equipment for the material, device/electronic, and bio/medical fields was installed at KOMAC for confirming the effects of beam irradiation on various samples. Finally, we aim to provide users with a one-stop service from beam irradiation to measurement at KOMAC.

Design of the 100 MeV Proton-Beam Target System for the Pulsed Neutron Source at the KOMAC

Among various types of neutron generators, the spallation neutron source is a unique way to generate high-energy and high-flux neutrons in a laboratory. The advantages of the spallation neutron source over other types of generators have been recognized; as a result, several spallation neutron facilities are in operation to provide users with high-quality neutron beams. For satisfying the demand for such a neutron facility in Korea, we have launched a project to construct a spallation neutron source facility by fully utilizing the high-power proton linear accelerator at the Korea Multipurpose Accelerator Complex (KOMAC) of the Korea Atomic Energy Research Institute (KAERI). In the facility, high-energy spallation neutrons can be generated by bombarding a thick metal target with a 100-MeV, 20-mA pulsed proton beam. In the present study, a neutron target system involving a target, moderator, and reflector (TMR) has been studied through extensive Monte- Carlo simulations. The detailed design of the TMR for generating thermal neutrons and guiding them to the experimental hall will be presented. Here, we present the result of numerical studies and the details of fundamental instruments, and we discuss future plans for the construction of the spallation neutron source facility at the KOMAC.

Experimental and Simulation Studies on EBIS at KOMAC

At the Korea Multipurpose Accelerator Complex (KOMAC), we have been working on electron beam ion sources (EBIS). An EBIS test bench consists of an EBIS-A, a newly designed Wien filter for the charge separation and a short pulse electronics for the production of short pulse ion beams. We also have a plan for another EBIS that has a 7 T superconducting magnet. Simulations of the electron beam in the 7 T EBIS are on progress. We report experimental results from the EBIS test bench and show simulation results on the electron gun design and the electron beam transmission through the 7 T magnetic field.

Temperature Stabilization of the Klystron Cooling Water at the KOMAC

A total of nine klystrons each with a high peak power are used to deliver RF power to the 100 MeV proton linac at the Korea Multi-purpose Accelerator Complex (KOMAC). We found that the temperature of the cooling water to the klystron cavity was deeply related to the RF power output from the klystron when the klystron was operated either in the open loop mode or at a saturation power level. To stabilize the RF power from the klystron, we need to stabilize the cooling water’s temperature as much as possible. To keep the cooling water’s temperature constant, we used an inverter-driven cooling fan at the cooling tower with proportional integral derivative (PID) controller. Through a proper tuning of the control parameters, we could suppress the temperature fluctuation to within ±0.2 °C and stabilize the output RF power from the klystron, regardless of the ambient temperature. Details on the dependency of the output RF power on the coolant temperature and stabilization method will be given in this paper.

Design Study and Fabrication of the Target/Ion Source to Generate a Li-8 Beam

The Korea Multi-purpose Accelerator Complex (KOMAC) has developed a target/ion source (TIS) to generate a Li-8 radioactive isotope beam. The basic concept of the TIS is that the Li isotope is produced at a beryllium-oxide target irradiated by a 100-MeV proton beam, and Li atoms are ionized at a surface ionization ion source (SIS). Various numerical studies were conducted to design the TIS. The FLUKA code was utilized to estimate the Li-8 production rate and to find an optimum target thickness. Also, a simple Monte Carlo code was developed to estimate the ionization efficiency of the SIS. In addition, a zero-dimensional power balance model of the TIS was developed, and a three-dimensional finite-element method was applied to obtain detailed thermal analysis results. On the basis of the thermal analysis, the related design and operation parameters were determined. The TIS designed by using various numerical studies was fabricated and tested. The TIS will be irradiated by a proton beam and generate Li-8 beam for β-NMR facility.

Measurement of production cross sections in proton induced reactions on natural zirconium

The production cross sections of 90g,92m,95gNb, 86,88,89g,95Zr, 86g,87m,87g,88Y, 85gSr, and 83Rb in a proton induced nuclear reaction of natural zirconium were measured within the proton energy range of 35.7–66.6 MeV at the Korea Multi-purpose Accelerator Complex (KOMAC), Gyeongju, Korea. The excitation functions of radionuclides produced from the natZr(p,x) reactions were determined through a stacked-foil activation method and an off-line γ-ray spectroscopy. A high purity germanium (HPGe) detector was used to measure the induced activities of the radionuclides. The incident beam energy in each foil was calculated from the SRIM code. The proton flux was determined by using the natCu(p,x)62Zn monitor reaction. The measured data were compared with the experimental data in the literature and the data from the TENDL-2017 library based on the TALYS code. The present results are in general agreement with the literature data and in some cases with the calculated data from the TENDL-2017 library. However, in some of the cases, the calculated data from the TENDL-2017 library overestimate or underestimate the experimental data.

Comparison of the proton irradiation-induced damage in SiCf/SiC with Sc-nitrate and Al2O3-Y2O3 sintering additives

We report microstructural evaluation in proton-irradiated SiCf/SiC up to a fluence level of 1018 p+/m2 (E = 20 MeV) performed at the Korea Multi-purpose Accelerator Complex (KOMAC). To fabricate the SiCf/SiC, a SiC-based matrix with two different sintering additives, Sc-nitrate and Al2O3-Y2O3, were infiltrated into the Tyranno® SiC preform by electrophoretic deposition and subsequent hot pressing. Scanning (SEM) and high resolution (HREM) electron microscopy was used to probe crack formation, pore generation and surface amorphization upon irradiation. SiC matrix was comparatively more crack-resistant in the SiCf/SiC with Sc-nitrate than that with Al2O3-Y2O3. Subsurface porosity evolved in the form of continuous bands for Al2O3-Y2O3 and discrete pockets for Sc-nitrate additives. Selective leaching of Si from the grain surface leads to the formation of a graded structure and surface amorphization. Irradiation-induced roughness on the fibers facilitates easy debonding at the SiCf-PyCcoating interface but no significant changes in the flexural behavior were observed.

Measurement of excitation functions for natPb(p,xn)199,200,201Pb reactions with stacked foil activation technique at KOMAC

The excitation functions of natPb(p,xn)199,200,201Pb reactions within the proton energy of 71.5 - 91.7 MeV were measured by using the 100-MeV linear accelerator at the Korea Multi-Purpose Accelerator Complex (KOMAC). The stacked foil activation and off-line gamma-ray spectrometric technique was used in the present study. The 27Al(p, 3p + n)24Na monitor reaction was used to estimate the proton flux. The excitation functions of natPb(p, xn)199,200,201Pb reactions were derived from the photo-peak activities of delayed γ-rays of the produced nuclei. The present results have been compared with the literature data and the theoretical values from TENDL-2015 library. The natPb(p,xn)199,201Pb reaction cross-sections at the proton energy of 91.7 MeV has been measured for the first time, whereas for the proton energies of 71.5 - 84.5 MeV are in general agreement with the literature data within limits of uncertainty. Overall, the experimental data from the present work and literature show increase trend with proton energy similar to the theoretical values of TENDL-2015 library with some systematic differences.