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The effects of indole-2,3-dione on radiosensitivity of U251 cells and zebrafish embryos
No full textRadiotherapy is an effective treatment for gliomas, which are among the most malignant tumors in the central nervous system (CNS). A significant challenge in glioma radiotherapy is improving tumor control while minimizing damage to normal nervous tissue. In this study, we investigated the dual role of indole-2,3-dione (Isatin, ISA), a compound with diverse biological and pharmacological activities, including anticancer, antioxidant, and anti-inflammatory properties, in modulating radiosensitivity. The effects of ISA were examined in both human malignant glioblastoma U251 cells in vitro and zebrafish (Danio rerio) embryos in vivo. In U251 cells, irradiation significantly decreased cell viability and clonogenic capacity, while increasing reactive oxygen species (ROS) levels, inducing Cell cycle G2/M arrest, upregulating apoptotic gene expression, and inducing apoptosis. ISA pretreatment markedly enhanced these radiation-induced effects, potentiating clonogenic inhibition and proapoptotic activity. Moreover, combined ISA and irradiation treatment led to increased DNA damage and delayed DNA repair in U251 cells. In the in vivo zebrafish model, ISA pretreatment demonstrated significant radioprotective effects, reducing radiation-induced damage, including embryo mortality, behavioral alterations, ROS overproduction, and upregulation of proapoptotic genes. These findings suggest that ISA has dual functionality: acting as a radiosensitizer for glioblastoma cells and a radioprotector for normal CNS cells, primarily by modulating ROS production and apoptotic pathways. This study provides robust preclinical evidence supporting the potential clinical application of ISA in brain tumor radiotherapy, offering a promising approach to optimize therapeutic outcomes in glioma treatment.journal articl
Effect of coaxial HPGe detector structure on γ-ray beam measurements
No full textCoaxial high-purity germanium (HPGe) detectors are widely used in applications requiring high-resolution gamma-ray spectroscopy. However, the internal structure of HPGe detectors, particularly the geometry of the inactive volumes inside the core of the detector, can significantly influence their performance in beam detection configurations. In this work, we investigate the impact of detector structure on the spectral response to pencil-like gamma-ray beams by comparing gamma-ray spectra measured with two coaxial HPGe detectors with similar active volumes but distinct internal geometries. Experimental measurements were conducted at the UVSOR synchrotron facility using collimated laser Compton scattered (LCS) gamma-ray beams with an energy of 5.53 MeV. Monte Carlo simulations using Geant4 toolkit have been performed to refine the detector models and replicate experimental results. The results reveal that the front layer thickness and the presence of structural elements such as the cold finger strongly affect the spectral features, particularly the appearance of coincidence sum peak of the annihilation radiation at 1.022 MeV. Off-axis irradiation significantly improves the detection efficiency and reduces the undesired induced interactions with inactive volumes. Additionally, we validate the observed pair production signatures through the available theoretical cross section, confirming the dominant role of internal structures in shaping the detector response under beam geometry. These findings are essential for optimizing detector configurations in precision gamma-ray beam experiments.journal articl
Introduction and overview: Chapter 1 of the special issue: on the path to tokamak burning plasma operation
No full text国際トカマク物理活動（ITPA）では、トカマク装置における燃焼プラズマに向けたプラズマ物理の理解と開発を目指し、共同実験及び協力研究開発を実施してきた。本論文は、7つのITPAトピカルグループにて実施された過去20年間の共同実験及び協力研究の成果について、包括的な概要を報告する。燃焼プラズマに向けた重要な問題に対する主要な進歩、最も重要な結果についてまとめる。journal articl
Ultrathin glass as a continuously replaceable debris shield for laser systems
No full textHigh-repetition-rate laser systems require continuous protection of optical components from debris generated during laser–matter interactions. Conventional debris shields offer high optical quality at the cost of inflexible replacement mechanisms or allow easy roll-based replacement but suffer from degraded wavefront performance. In this study, we evaluated the feasibility of ultrathin glass, originally designed for flexible electronic applications, as a continuously replaceable debris shield combining excellent optical and mechanical properties. The optical transmission, wavefront error, and polarization behavior of 50-μm-thick ultrathin glass were characterized and benchmarked against fused silica and nitrocellulose film shields. The ultrathin glass showed high UV–NIR transmittance, minimal wavefront distortion (λ/5 PV, λ/20 RMS), and no observable birefringence. A compact roll-to-roll transport system was developed to support continuous shield renewal in vacuum. Optical stability was tested under active motion using a Ti:sapphire laser delivering 1-J and 40-fs pulses at 10 Hz. The beam pointing deviation remained below 40 μrad during shield translation. Furthermore, high-intensity ion acceleration experiments verified that the shield maintained stable focusing and target interaction over 4000 shots. Degradation was limited to the transmittance loss from debris accumulation with no laser-induced damage. The proposed shield system supports over 300 000 shots with a 20-m-long roll, which can be scaled to hundreds of meters for extended operation. These results demonstrate the viability of ultrathin glass as a practical and scalable debris protection solution for future laser facilities.journal articl
Identification of a magnetohydrodynamic trigger for plasma explosions in magnetic fusion beyond existing paradigms
No full textIn magnetic-fusion devices, magnetohydrodynamic (MHD) disturbances such as edge-localized modes (ELMs), have interesting similarities to explosive dynamical events observed in space. Various models for the mechanisms triggering such disturbances have been proposed. However, current studies have focused on developing methods for controlling such effects based on empirical scaling. Although unanswered questions remain regarding ITER, diverse viewpoints beyond the current paradigm can provide a deeper understanding, even for widely accepted answers. Herein, we define the triggering time of an ELM using precise diagnostics to eliminate the uncertainty that can accompany the determination of causal relationships. This has enabled us to identify a precursor MHD with tearing parity (poloidal/toroidal mode numbers m/n = 4/1) as the cause of an ELM; it leads to the development of a macroscopic ELM when the magnetic perturbation exceeds a threshold of ~10 Gauss within ≤100 μs, providing a consistent representation of this phenomenon that extends from the precursor to the collapse. The explosive growth timescale from the triggering time is consistent with a hyper-resistive model of magnetic braiding and stochasticity. This approach to solving the triggering problem provides valuable scientific insights into diverse magnetized-plasma-explosion physics.journal articl
Online un-supervised tearing mode detection with sequentially discounting algorithms for JT-60SA
No full textA non-empirical tearing mode detector model based on statistical anomaly detection with sequentially discounting algorithms has been developed, and its prediction performance has been demonstrated with experiment data in the JT-60SA initial operation phase. Detection and prediction of the occurrence of disruptions is an important issue to protect the tokamak device from the damage caused by disruptions, and empirical models using machine learning techniques are being developed. A non-empirical model based on anomaly detection is one possible solution to an inherent problem of uncertainty as to whether such empirical models can be extrapolated to future tokamaks. The developed detector model has shown a good prediction performance, and its processing time was smaller than the control cycle time of the JT-60SA without any advanced devices such as GPUs. The result suggests that the statistical anomaly detection with sequentially discounting algorithms is a good choice to be implemented in the plasma controller not only in the JT-60SA but also in the future devices such as ITER and DEMO.journal articl
Quantitative evaluation of a longitudinal rms emittance decrease using nonlinear space charge force in an intense deuteron linac
No full textRadio frequency (rf) bunchers are often utilized to control a longitudinal bunch length in low- and medium-energy transport lines. However, nonlinear rf fields in the bunchers deform a longitudinal phase space distribution, which causes emittance growth leading to beam quality degradation and unexpected beam losses. This paper describes a decrease in the longitudinal rms emittance in a high-intensity deuteron linac, where the longitudinal phase space deformed by a nonlinear rf field in the buncher is self-linearized by a longitudinal nonlinear space charge force. To quantitatively explain this phenomenon, we develop two formulas to express deformations of phase space and forces acting on the beam. We perform particle tracking simulations with the TraceWin code using a 125 mA, 5 MeV deuteron beam at the Linear IFMIF Prototype Accelerator (LIPAc) and validate the two formulas by applying them to LIPAc. The quantitative evaluations of the deformations with the formulas lead to a deeper understanding of beam physics and are also expected to be useful in mitigating phase space deformation.journal articl
Construction and analysis of guiding center distributions for tokamak plasmas with ambient radial electric field
No full textThe contribution of a time-independent toroidally-symmetric radial electric field E_r is implemented in VisualStart (Bierwage et al. (2022) [21]), a code whose purposes include the construction of guiding center (GC) drift orbit databases for the study of plasma instabilities in tokamaks. E_r alters the transit frequencies and orbit shapes of charged particles, and it shifts the trapped-passing boundary, especially in the thermal part of the velocity distribution. E_r can also affect fast particle resonances in the kHz frequency range. Here, KSTAR, JT-60U and ITER tokamak cases are used as working examples to test our methods. In the course of our detailed consistency checks, we unravel how nonuniformities in the moments of a GC distribution emerge from the collection of individual GC orbits. We also discuss technical and practical issues connected with E_r, two of which shall be emphasized here: First, the GC orbit space is sampled in the magnetic midplane as before, and we find that, in the presence of E_r, midplane-based coordinates are not only equivalent but superior to conventional constants of motion, allowing to attain high numerical accuracy and efficiency with a relatively simple mesh. Second, the periodic parallel acceleration and deceleration of GCs via the mirror force is modulated by E_r. Although its poloidal transit (bounce) average is zero, this parallel electric acceleration gives rise to a reference point bias: When measured at fixed GC launch coordinates, the toroidal transit frequency of passing orbits acquires an apparent E_r-dependence, which can cause confusion.journal articl
Design Study of Conical-Canted-Cosine-Theta Scanning Magnet for Heavy Ion Therapy
No full textIn heavy ion therapy, miniaturizing not only the accelerators, beamlines, or magnets but also the power supplies are crucial for downsizing the facility and reducing the installation costs. The use of combined-function superconducting magnets and discrete-cosine-theta combined X-Y scanning magnets (SCM) has already significantly reduced the gantry’s rotating radius.However, reducing the length of the beam delivery system by introducing conventional SCM significantly increases the power supply’s nominal capacity. In this study, a canted-cosine-theta (CCT) SCM is proposed to address these challenges while maintaining the same length of the beam delivery system. Its magnetic field strength is less dependent on the aperture, making it particularly suitable for SCM that requires a large aperture at the outlet. This paper describes the conceptual design of a combined X-Y SCM with conical-CCT winding and its performance.journal articl
Issues in monitoring orthopedic surgeons with active personal dosemeters when exposed to pulsed X-ray fields during orthopedic procedures
No full textIt is crucial to monitor healthcare workers’ radiation exposure, especially given the increasing reliance on X-ray imaging technologies. In response to new evidence that the threshold for lens opacity is lower than previously thought, the International Commission on Radiological Protection (ICRP) has revised the annual dose limit for exposure to the lens of the eye. After the revision of the annual eye lens dose limit, the new survey on the dosemeter wearing rate was conducted in Japan. The result showed that despite the presence of monitoring protocols, the dosemeter wearing rate among healthcare workers was still low. Compliance often lacked robust verification measures, especially in smaller medical facilities. Active personal dosemeters (APDs) are commonly used in Japan, although studies suggest that they may underestimate exposure in certain settings, such as pulsed X-ray fields. Passive dosemeters, on the other hand, serve as legal dosemeters, offering a more accurate assessment of radiation exposure. This article addresses issues related to the monitoring of healthcare workers using APDs and clarifies concerns regarding the use of APDs by orthopedic surgeons during procedures involving high-dose X-ray exposure. A series of performance tests suggested that the APDs worn by orthopedic surgeons, who are often exposed to higher dose rates near patients, may underestimate radiation levels during procedures. This underestimation occurs because the surgeons are exposed to pulsed, scattered X-ray fields with energies ranging from 20 and 100 keV. The results also suggest monitoring techniques should be improved to ensure the safety of healthcare workers.journal articl