Results of All ITER TF Full-Size Joint Sample Tests in Japan

Nine toroidal field (TF) coils have been developed in Japan for the international thermonuclear experimental reactor (ITER). The joint resistance of TF coil should satisfy the requirement of smaller than 3 nano-ohm at 2 T of external magnetic field and 68 kA of transport current. Full-size joint sample (FSJS) tests were performed for joint development and for TF coil manufacture, as part of the process control. 11 FSJS tests are conducted in total. FSJS tests were conducted with assistance from a test faculty in the National Institute for Fusion Science as reported in a previous paper. All FSJS tests successfully satisfied the requirement of resistance less than 3 nΩ at 2 T. Additionally, the TF coil joints are subjected to cyclic electromagnetic force and warm-up/cool-down during the ITER operation. The authors investigated the joint performance for the abovementioned influence. The results showed no degradation in the joint resistance. Thus, the TF joint developed in Japan was qualified successfully

An Analytical Formula for Determining the Electrical Impedance between a Single Adherent Cell and Sensor Substrate

An analytical formula for electrical impedance between an adherent living cell and sensor substrate measured using a microelectrode is presented for the first time. Previously-reported formula has been applicable only for the case where many cells are on a large electrode. In contrast, our formula is valid even when a microelectrode smaller than the cell size is underneath the cell, which is often the case for the state-of-the-art single-cell analysis. Numerical simulations for verifying the accuracy of our formula reveals that the discrepancies between the theoretical impedances calculated by our formula and numerical simulation results are negligibly small. Our formula will be useful for describing cell-substrate impedance properties in equivalent circuit model analysis or sensor design optimizations.Comment: 29 pages, 7 figures, journal manuscrip

Design of the energy spectrometer for laser-accelerated protons using stacked CR-39 detector

In the laser-driven ion acceleration experiment, CR-39 track detectors have been used for the measurement of laser-accelerated ions. This is because CR-39 detectors are insensitive for X-rays and energetic electrons, which are simultaneously generated with ions by the interaction between intense laser pulse and the target material. To evaluate the energy spectrum of laser-accelerated protons, which has the broad energy spectrum, the stacked CR-39 detectors are required because the energetic protons penetrate through the single layer of CR-39. For example, in the case of HARZLAS (TD-1) type CR-39 detector, which can detect up to 20 MeV protons, with the thickness of 0.9 mm, more than 9.63 MeV protons penetrate through the single layer. In other words, the protons with the energies more than 9.63 MeV create the etch pits not only on first layer but also on second layer. In such case, the accurate energy spectrum is not able to obtain by the numbers of etch pits on each layer of CR-39. In the present study, to measure the precise energy spectrum of laser-accelerated protons, we have designed the stacked detector using HARZLAS (TD-1) and energy moderators. Particle and Heavy Ion Transport Code System (PHITS) has been used for the optimization of the thickness of energy moderator and proof-of-principal calculation of the designed detector. We have applied polytetrafluoroethylene (PTFE) as the energy moderators because PTFE has the largest stopping power in the plastics. The thickness of PTFE has been determined as 1.8 mm to avoid a 20 MeV proton entering into the second layer of HARZLAS (TD-1). Therefore, the repetition of 0.9 mm thick HARZLAS (TD-1) and 1.8 mm thick PTFE can obtain the accurate energy spectrum of broad energy spread proton beams. In order to confirm the capability of the designed stacked detector, we have tried to reconstruct the model energy spectrum using the PHITS code simulation. Figure 1 shows the comparison between the model spectrum and the calculated spectrum. From the results of this simulation, the obtained energy spectrum almost reconstructed the model energy spectrum. Thus, the designed stacked detector can be applied to laser-driven ion acceleration experiments as the energy spectrometer for laser-accelerated protons.The 12th International Workshop on Ionizing Radiation Monitorin

Results of ITER TF coil double pancake heat treatment in Japan

In Japan, 9 ITER TF coils were manufactured for the ITER project. Each TF coil consists of seven Nb3Sn conductor double pancakes (DPs). In DP manufacturing, heat treatment is one of the most important processes, because the insertion of a heat treated conductor into the radial plate groove (i.e., transfer) is complicated owing to the elongation of the conductor under heat treatment. A critical current distribution over the DP may also occur owing to the temperature distribution and disturbance in the heat treatment process. To address these issues, this study developed a procedure wherein the conductor length elongation caused by heat treatment is precisely considered, and transfer can be successfully achieved for all the DPs. In addition, strand witness samples were simultaneously heat treated with the DPs, and their critical current (Ic) was measured. Subsequently, it was confirmed that the average Ic is equivalent to those in the strand acceptance test while the standard deviation of Ic for the witness samples is approximately 4 % larger than that for the strand acceptance test. It was also confirmed that the disturbance of the heat treatment was negligible. Related results are described herein

Commissioning of a conformal irradiation system for heavy-ion radiotherapy using a layer-stacking method

The commissioning of conformal radiotherapy system using heavy-ion beams at the Heavy Ion Medical Accelerator in Chiba (HIMAC) is described in detail. The system at HIMAC was upgraded for a clinical trial using a new technique: large spot uniform scanning with conformal layer stacking. The system was developed to localize the irradiation dose to the target volume more effectively than with the old system. With the present passive irradiation method using a ridge filter, a scatterer,a pair of wobbler magnets, and a multileaf collimator, the width of the spread-out Bragg peak (SOBP) in the radiation field could not be changed. With dynamic control of the beam-modifying devices during irradiation, a more conformal radiotherapy could be achieved. In order to safely perform treatments with this conformal therapy, the moving devices should be watched during irradiation and the synchronousness among the devices should be verified. This system, which hasto be safe for patient irradiations, was constructed and tested for safety and for the quality of the dose localization realized. Through these commissioning tests, we were successfully able to prepare the conformal technique using layer stacking for patients. Subsequent to commissioning the technique has been applied to patients in clinical trials