The National Institute of Radiological Sciences (放射線医学総合研究所) (NIRS) is a radiation research institute in Japan. The NIRS was established in 1957 as the Japan's only one institute of radiology. The NIRS maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation.The National Institute of Radiological Sciences hospital established in 1961 is a research hospital with a basic focus on radiation therapy. In 1993 the HIMAC (Heavy Ion Medical Accelerator in Chiba) of NIRS was launched, and in 1997 the Research Center for Charged Particle Therapy was opened as one of the leading medical centers using carbon ions are in operation.On April 1, 2016, the Japan Atomic Energy Agency (JAEA) transferred some of its laboratories to the NIRS, and the NIRS body was renamed to the National Institutes for Quantum and Radiological Science and Technology (QST) which includes existing laboratories of the NIRS; the NIRS is currently a radiological research division of the QST.
This study reports the development of CO_2 laser interferometers for electron density measurements on the large helical device (LHD). Two types of interferometers using approximately 10 μ m are developed. One is an imaging two-color laser interferometer (I-TCI) for measuring density profiles and macroscopic fluctuations of MHD instabilities, and the other is a single channel phase-modulated dispersion interferometer (PMDI) designed for reliable density monitoring. The diagnostic principles, systems, and analysis techniques are outlined, and representative measurement results are presented. The I-TCI system was also designed to operate in the deuterium experiments performed on LHD from 2017 until 2022. Shielding against neutron and γ -ray irradiation was necessary to prevent damage to the I-TCI detection system. Design strategies for neutron and γ -ray shielding are presented in the appendices.
We report the results of an experiment to study the temporal properties of superfluorescence at a wavelength of 164 nm emitted from helium ions excited to either the 3p state or 4p state by pulses from a free-electron laser. The two different processes (direct 3p-2s superfluorescence; two-step cascade 4p-3s-2p or 4p-3d-2p superfluorescence) are compared to each other and to the results of numerical simulations.
We present the design and application of a general algorithm for Prediction And Control using MAchiNe learning (PACMAN) in DIII-D. Machine learning (ML)-based predictors and controllers have shown great promise in achieving regimes in which traditional controllers fail, such as tearing mode (TM) free scenarios, ELM-free scenarios and stable advanced tokamak conditions. The architecture presented here was deployed on DIII-D to facilitate the end-to-end implementation of advanced control experiments, from diagnostic processing to final actuation commands. This paper describes the detailed design of the algorithm and explains the motivation behind each design point. We also describe several successful ML control experiments in DIII-D using this algorithm, including a reinforcement learning controller targeting advanced non-inductive plasmas, a wide-pedestal quiescent H-mode ELM predictor, an Alfv & eacute;n Eigenmode controller, a Model Predictive Control plasma profile controller and a state-machine TM predictor-controller. There is also discussion on guiding principles for real-time ML controller design and implementation.
Fluorescent nanodiamonds (FNDs) containing negatively charged nitrogen-vacancy (NV-) centers are vital for many emerging quantum sensing applications from magnetometry to intracellular sensing in biology. However, developing a scalable fabrication method for FNDs hosting color centers with consistent bulk-like photoluminescence (PL) and spin coherence properties remains a highly desired but unrealized goal. Here, we investigate optimized ball milling of single-crystal diamonds produced via chemical vapor deposition (CVD) and containing 2 ppm of substitutional nitrogen and 0.3 ppm of NV- to achieve this goal. The NV charge state, PL lifetime, and spin properties of bulk CVD diamond samples are directly compared to milled CVD FNDs and commercial high-pressure high-temperature (HPHT) FNDs. We find that on average, the relative contribution of the NV- charge state to the total NV PL is lower and the NV PL lifetime is longer in CVD FNDs compared to HPHT FNDs, both likely due to the lower Ns0 concentration in CVD FNDs. The CVD bulk and CVD FNDs on average show similar average T1 spin relaxation times of 3.2 ± 0.7 ms and 4.7 ± 1.6 ms, respectively, compared to 0.17 ± 0.01 ms for commercial HPHT FNDs. Our results demonstrate that ball milling of CVD diamonds enables the large-scale fabrication of NV ensembles in FNDs with bulk-like T1 spin relaxation properties.
Laser-driven capacitor-coil targets provide a compact platform for generating strong magnetic fields and are widely used in magnetized high-energy-density (HED) plasma experiments. In addition to magnetic-field generation, these targets also produce plasma in the coil region, which can influence the subject physical processes and interact with secondary targets or external plasmas in their applications. However, direct, time-resolved measurements of the plasma density surrounding the coil remain limited. Here, we report interferometric measurements of the plasma density evolution in laser-driven capacitor-coil targets irradiated by the University of Osaka LFEX laser. Two-dimensional electron density maps reveal two distinct plasma sources loading the coil region: plasma generated in the coil itself and plasma produced by laser ablation of the target plates. These results provide quantitative information on plasma loading and evolution in capacitor-coil targets and are directly relevant to the design and modeling of magnetized HED plasma experiments.
