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Co-simulation of Cryoplant and Tokamak superconducting magnet system (referred to as Magnet) has been performed to characterize operating condition associated with control strategies. Cryoplant model, developed by EcosimPro®, consists of three identical refrigerators connected with integrated Cryoplant Termination Cold Box (CTCB) which distributes the coolant to five Auxiliary Cold Boxes (ACB) for Magnet and CryoPump (CP) cooling. Meanwhile, Magnet model, developed by Visual Modeler®, consists of Toroidal Field (TF) coil, Central Solenoid (CS), TF STructure (ST) and Poloidal Field (PF)/Correction Coil (CC). Magnet model computes thermo-hydraulic behavior of a forced-flow Supercritical Helium (SHe), with specified thermal energy deposition along the conductor in the case of Deuterium-Tritium (DT) operation as well as plasma disruption followed by the fast energy discharge of CS and PF. Global simulation of ITER cryogenic system provides its operating characteristics for complex cryogenic processes. The paper discusses the coupling of Cryoplant and Magnet models and the control strategy for Cryoplant to manage substantial dynamic heat loads.

Process studies for Toroidal Field Structure (TF ST) system with a dedicated Auxiliary Cold Box (ACB-ST) have been conducted under 15 MA baseline, including plasma disruptions. ACB-ST consists of two heat exchangers immersed in the Liquid Helium (LHe) subcooler, which are placed at the inlet/outlet of a Supercritical Helium (SHe) cold circulator (centrifugal pump). Robustness of ACB-ST is a key to achieve the stability of TF coil operation since it provides the thermal barrier at the interface of the TF Winding Pack (WP) with ST. The paper discusses the control logic for the nominal plasma operating scenario and for Mitigation to regulate the dynamic heat loads on ST. In addition, the operation field of a cold circulator is described in the case of plasma disruptions. The required performance of heat exchangers in the ACB-ST is assessed based on the expected operating conditions.

During the first two years of the LHD experiment the following results have been achieved: (i) higher Te (Te(0) = 4.4 keV at ne = 5.3 × 1018 m-3 and Pabs = 1.8 MW); (ii) higher confinement (τE = 0.3 s, Te(0) = 1.1 keV at ne = 6.5 × 1019 m-3 and Pabs = 2.0 MW); (iii) higher stored energy, Wpdia = 880 kJ at B = 2.75 T. High performance plasmas have been realized in the inward shifted magnetic axis configuration (R = 3.6 m) where helical symmetry is recovered and the particle orbit properties are improved by a trade-off of MHD stability properties due to the appearance of a magnetic hill. Energy confinement was systematically higher than that predicted by the International Stellarator Scaling 95 by up to a factor of 1.6 and was comparable with the ELMy H mode confinement capability in tokamaks. This confinement improvement is attributed to configuration control (inward shift of the magnetic axis) and to the formation of a high edge temperature. The average beta value achieved reached 2.4% at B = 1.3 T, the highest beta value ever obtained in a helical device, and so far no degradation of confinement by MHD phenomena has been observed. The inward shifted configuration has also led to successful ICRF minority ion heating. ICRF powers up to 1.3 MW were reliably injected into the plasma without significant impurity contamination, and a plasma with a stored energy of 200 kJ was sustained for 5 s by ICRF alone. As another important result, long pulse discharges of more than 1 min were successfully achieved separately with an NBI heating of 0.5 MW and with an ICRF heating of 0.85 MW.

Seasonal variations of activity and horizontal propagation direction of gravity waves in the MLT region at mid-latitude over Shigaraki, Japan (35 N) are investigated for various time and spatial scales using the MU radar observations and recent airglow imaging observations. Semiannual variation with solsticial maxima and equinoctial minima are generally observed for short period (

The pressure drop of two prototype cable-in-conduit conductors (CICCs) were measured. The NET conductor is a conventional type CICC, while the CEA conductor has a central flow channel to reduce hydraulic impedance. The pressure drop measurements were conducted with helium at temperatures ranging from 2 K to 4.7 K, and pressure from the saturated vapor pressure to in excess of 3 bar. Computer image analysis was used to estimate the flow cross sectional area and wetted perimeter of the conductors. The data are expressed in terms of a classical friction factor, and compared with previous experimental results. >

Implementation of a conventional current lead with a pulse tube refrigerator has been validated to be working as an Integrated Current Lead (ICL) system for the Superconducting Magnetic Energy Storage (SMES). Realization of the system is primarily accounted for the flexibility of a pulse tube refrigerator, which does not posses any mechanical piston and/or displacer. As for an ultimate version of the ICL system, a High Temperature Superconducting (HTS) lead links a superconducting coil with a conventional copper lead. To ensure the minimization of heat loads to the superconducting coil, a pulse tube refrigerator has been upgraded to have a second cooling stage. This arrangement reduces not only the heat loads to the superconducting coil but also the operating cost for a SMES system. A prototype two-stage pulse tube refrigerator, series connected arrangement, was designed and fabricated to satisfy the requirements for the ICL system. Operation of the first stage refrigerator is a four-valve mode, while the second stage utilizes a double inlet configuration to ensure its confined geometry. The paper discusses the optimization of second stage cooling to validate the conceptual designImplementation of a conventional current lead with a pulse tube refrigerator has been validated to be working as an Integrated Current Lead (ICL) system for the Superconducting Magnetic Energy Storage (SMES). Realization of the system is primarily accounted for the flexibility of a pulse tube refrigerator, which does not posses any mechanical piston and/or displacer. As for an ultimate version of the ICL system, a High Temperature Superconducting (HTS) lead links a superconducting coil with a conventional copper lead. To ensure the minimization of heat loads to the superconducting coil, a pulse tube refrigerator has been upgraded to have a second cooling stage. This arrangement reduces not only the heat loads to the superconducting coil but also the operating cost for a SMES system. A prototype two-stage pulse tube refrigerator, series connected arrangement, was designed and fabricated to satisfy the requirements for the ICL system. Operation of the first stage refrigerator is a four-valve mode, while the...

Development of Cryogenic Process Real-time SimulaTor (C-PREST) has been finalized to provide a platform to study the entire cryo-plant processes of Large Helical Device (LHD). Although LHD utilizes three different cooling schemes, a pool boiling, a forced-flow supercritical helium cooling and a two-phase flow cooling, C-PREST successfully demonstrated its capability to simulate the LHD cooldown process and filling five Liquid helium (LHe) reservoirs independently. To understand the dynamic behaviors of the cryo-plant, the simulations have been carried out for a transient operating condition as introducing the thermal disturbance(s) to the 20,000 liter LHe reservoir of the refrigerator. This paper describes simulations of a large cryogenic plant and discusses dynamic behavior of helium refrigerator/liquefier under various thermal disturbances. Computational speeds associated with these operating conditions were also discussed.

A dynamic simulation of a large scale cryogenic plant has been conducted, using the Cryogenic Process REal‐time SimulaTor (C‐PREST) developed as a platform to study cryogenic plant processes. The target plant, Large Helical Device (LHD), consists of a 10 kW class helium refrigerator/liquefier and superconducting coil systems with their supporting structure. Since the development of helium refrigerator/liquefier had been completed, the simulation model was focused on the superconducting coil systems. As the preliminary step for the entire cryogenic plant, the coils are simplified and modeled to have certain temperature efficiencies. Cooldown of the coil systems were conducted from the room temperature to close to 4.4 K, utilizing automatic cooldown sequence programs for the actual cryogenic plant. The paper discusses the computational speed just before establishing the two‐phase flow condition and the validity of the simulations compared with the real plant operation.

Dynamic behavior of a helium liquefier has been studied in detail with a Cryogenic Process REal‐time SimulaTor (C‐PREST) at the National Institute for Fusion Science (NIFS). The C‐PREST is being developed to integrate large‐scale helium cryogenic plant design, operation and maintenance for optimum process establishment. As a first step of simulations of cooldown to 4.5 K with the helium liquefier model is conducted, which provides a plant‐process validation platform. The helium liquefier consists of seven heat exchangers, a liquid‐nitrogen (LN2) precooler, two expansion turbines and a liquid‐helium (LHe) reservoir. Process simulations are fulfilled with sequence programs, which were implemented with C‐PREST based on an existing liquefier operation. The interactions of a JT valve, a JT‐bypass valve and a reservoir‐return valve have been dynamically simulated. The paper discusses various aspects of refrigeration process simulation, including its difficulties such as a balance between complexity of the adopted models and CPU time.

The authors measured the pressure drop of supercritical helium and He II counterflow heat transport in subscale cable-in-conduit conductors (CICCs) at a variety of different temperatures. These measurements were made on various conductors with different flow areas, void fractions, and strand diameters. Classical friction factor analysis was used to correlate the pressure drop results. The results of this analysis revealed systematic variations in the friction factor which appear to be dependent on the temperature of the helium. In a separate experiment heat transport in He II contained in the CICCs was analyzed in terms of the Gorter-Mellink relationship to obtain an independent determination of the flow cross-sectional area. These cross-sectional areas were used to reanalyze previously reported pressure drop data on the same conductors. Use of He II counterflow measurements as a general method to characterize the hydraulics of these conductors is discussed. >

A collaborative MU radar and imaging observations of nightglow emissions over Shigaraki (35oN, 136oE), Japan, was carried out between January and March as part of the Planetary Scale Mesopause Observing System (PSMOS) campaign to investigate the horizontal structure of gravity waves around the mesopause region. The horizontal wavenumbers and apparent frequencies of quasi-monochromatic wave events of short periods ( (10 ∼ 80 km) were determined from four nightglow emission layers, OI 557.7 nm (∼ 96 km), O2 A (0-1) band (∼ 94 km), Na 589.3 nm (∼ 90 km) and NIR OH bands (∼ 87 km). This information was combined with simultaneous MU radar wind and SATI temperature measurements at the same height range to derive the intrinsic wave parameters for these events. Using the background structure information, the propagating characteristics such as wave ducting, evanescence and vertical propagation as internal modes was investigated. The study revealed a significant fraction of occurrence of non-propagation events with approximately 60% of all events. These results suggest that the small-scale gravity waves are highly susceptible to the variations of the mean flow and that the ducted effects are relatively common in the upper mesosphere.

Publisher Summary A dummy heat load experimental apparatus is developed to test a refrigeration system of the Large Helical Device (LHD). It establishes a full automatic operating scenario of the helium refrigeration system for the LHD. The apparatus primarily consists of a forced-flow low temperature helium line, a liquid helium supply line and a liquid helium bath. The helium refrigeration system is operated with three refrigeration modes under steady-state condition. It is confirmed that the refrigeration system maintain reliable operation with a dummy load apparatus. However, the system is not fully satisfied its full-automatic operating mode. In other words, control valves of the refrigerator or liquefier are required some adjustment by an operator while operating with various refrigeration modes. Additional experiments are still necessary to establish full-automatic condition of the refrigeration system.

The optimal dose of cisplatin (CDDP) for combination chemotherapy for the treatment of inoperable, advanced gastric cancer has yet to be established. We therefore performed a randomized study to compare the therapeutic usefulness of two dose levels of cisplatin. 5'-deoxy-5-fluorouridine (5'-DFUR 1,400 mg/m(2)/d) was given orally on days 1 to 4 and 15 to 18. Mitomycin C (MMC, 5.75 mg/m(2)/d) was injected intravenously on day 5. In addition, 80 mg/m2/d of CDDP (regimen A) or 60 mg/m(2)/d of CDDP (regimen B) was given by 2-h intravenous drip infusion on day 5. This treatment cycle was repeated every four weeks. Fifty-six patients were enrolled. Clinical response was evaluated in 32 patients (regimen A, 16 patients; regimen B? 16 patients) with measurable lesions. The response rate was significantly higher with regimen A (9 PR/16, 56.3%) than with regimen B (3 PR/16, 18.9%) (p=0.028, chi(2) test). Median survival was slightly but not significantly longer with regimen A (7.4 months) than with regimen B (6.3 months). Drug toxicity included myelosuppression and gastrointestinal symptoms, but there were no serious adverse reactions or differences in safety between the treatment regimens. Regimen A was associated with a high response rate and low toxicity. The optimal dose of CDDP in combination with 5'-DFUR and MMC for the treatment of advanced gastric cancer is regarded to be 80 mg/m(2).

The thermal hydraulic characteristics of a prototype CEA Cable-in-Conduit Conductor (CICC) have been studied in steady state and transient conditions. The supercritical helium velocity in the central channel was measured with a Pitot tube located at the down stream end of the conductor. An inductive heater, located at the center of the conductor, initiated thermally induced transient flow of the helium within the conductor. The induced flow velocity was measured as a function of Reynolds number and heat input. A calorimetric calibration technique was used to estimate the total heat input to the conductor. In a separate part of the experiment, a thermometer array was installed in the central channel to record the helium temperature. The associated reduction of central channel flow area significantly affects the thermal hydraulic characteristics of the conductor.

The dynamic simulation of a sub-scale ITER Central Solenoid (CS)/STRucture (STR) cooling loop has been performed to investigate the cryogenic control strategies against pulsating heat loads. HELIOS facility has been modified for this particular study, which consists of a Liquid Helium (LHe) reservoir with two immersed heat exchangers, a circulation pump and an approximately 130 m long piping with three evenly distributed heated sections. The setup provides the equivalent thermo-hydraulic configuration of the ITER CS/STR, cooled by the forced-flow Supercritical Helium (SHe). The dynamic simulator, C-PREST, has been utilized to model the HELIOS test loop and to compare the results with the experimental data sets. This paper presents the dynamic simulation results and discusses the control strategy to minimize the cooling power requirements, to have high reliability.

One of the main challenges of the ITER cryogenic system is to manage the large pulsed heat load variation generated by the superconducting magnet system during the fusion experiments. A solution proposed to smooth such pulses and verified by numerical simulations is to use the ITER magnet structure (ST) system as a thermal buffer by taking advantage of its large mass of about 5,000 tons and consequent thermal inertia. In order to validate the simulated predictions, tests have been executed on existing cryogenic facilities. In this paper we will present the results of the ITER cryogenic system feasibility tests performed at KSTAR. The tests were concentrated on the heat load mitigation scenario of the ITER ST via variation of the coolant mass flow rate by using a flow by-pass valve in parallel with an in-line valve.

A new procedure of fuel layering for the Fast Ignition Realization Experiment (FIREX) target is proposed. A conical laser guide heating technique was experimentally demonstrated in principle as the followings. It employed the target consisting of a polystyrene (PS) shell, a fill tube and a conical laser guide. At first, liquid fuel was fed into the shell and existed around the conical laser guide because the surface tension of the fuel must cause it. Then, it was solidified. The laser light provided a heat source to the conical laser guide so that the solid fuel was moved to the other interior of the shell. This process resulted in missing solid fuel around the conical laser guide. To fill the vacant space, liquid fuel was added as temperature was raised to the melting point. After the liquid fuel addition, temperature was lowered to the solidification point again. During this process, most of the solid fuel could survive.

Performance of the LHD cryogenic system in the first year's operation was described making importance on the recovery process after the normal transition of the helical coils. During the excitation tests of the LHD superconducting coils up to 2.75 T, the normal zone propagation was observed in the helical coil and the emergency shut-off of the coil power supplies was carried out. 2,700 l of liquid helium evaporated from the helical coils. The coils and the helium refrigerator were separated automatically and the helium refrigerator could keep its steady state operation. After the pressure and flow rate of the recovery gas from the helical coils were settled down to the normal state, the coils were connected to the helium refrigerator and the cooling was restarted. The system could return to the steady state in which coil excitation is enabling, by only three and a half hours.