Preliminary Design of Control Network for HT-7U Tokamak Cryogenic System

In the course of the cryoplant modernization, a control network will be set up in order to facilitate the control, the supervision, the centralized data acquisition and the alarm handling of the cryogenic system for HT-7U tokamak. The paper introduces the preliminary design of control network based on the Controller Link Network for HT-7U tokamak cryogenic system. The multi-layer structure mentioned in the paper is the mainstream of automatic control. The control philosophy, the structure of the network and the components for control are also presented.

Present status and one upgrading method with a cold compressor of the EAST sub-cooling helium cryogenic system

Since 2006, the superconducting toroidal field（TF） coils of the Experimental Advanced Superconducting Tokomak（EAST） have been successfully cooled by supercritical helium at a temperature of 4.5 K and a pressure of 4 bara in eleven experiments. To obtain higher operating currents and magnetic fields it is necessary to lower the operating temperature of the TF coils.The EAST sub-cooling helium cryogenic system, with a warm oil ring pump（ORP）, was tested twice in cool-down experiments, which made the TF coils operate at 3.8 K. However, the long term operational stability of the sub-cooling system cannot be guaranteed because of the ORP＇s poor mechanical and control performance. In this paper, the present status of the EAST subcooling helium cryogenic system is described, and then several cooling methods below 4.2 K and their merits are presented and analyzed. Finally, an upgrading method with a cold compressor for an EAST sub-cooling helium cryogenic system is proposed. The new process flow and thermodynamic calculation of the sub-cooling helium system, and the main parameters of the cold compressor, are also presented in detail. This work will provide a reference for the future upgrading of the sub-cooling helium system for higher operation parameters of the EAST device.

Optimization Analysis and Simulation of the EAST Cryogenic System

This paper presents the optimization cycle of the EAST cryogenic system. A simulation analysis and simulation of the main Claude program of this cycle was developed on the basis of the characteristics of the components and verified with the experimental results. The built-in volume ratio of the No. 7 compressor was tested with the purpose of finding the optimum internal pressure ratio to comply with the external pressure ratio so as to increase the isothermal efficiency and cycle efficiency. In addition, the UA （U, heat transfer coefficient; A, heat transfer area） values of the heat exchangers, efficiencies of turbines, mass flow fraction of the turbine stream were analyzed in order to improve the capacity or efficiency of the cycle. Finally, in view of the estimated heat loads of EAST in future, an upgraded operational cycle of 1500 W/4.5 K ＋1000 W/3.5 K ＋5 g/s is proposed according to the simulation.

The Application and Improvement of Helium Turbines in the EAST Cryogenic System

The helium cryogenic system supplies supercritical helium cooling capacity at 4.5 K for the superconducting magnets in the EAST superconducting tokamak.Four low-temperature helium turbines are used in the 2 kW helium refrigeration system,and their performance and reliability are critical for the continuous operation of the tokamak.The turbines were made by the Helium Mechanics Company in Russia.The start-up process is very unstable,easily broken,and thus testing and improvements are needed.In this paper,we analyze the structure of the helium turbine,make improvements,and describe the testing process and results of the improved helium turbines.Some of the operational experiences during the start-up process and tests are also presented.

Optimal design of the first stage of the platefin heat exchanger for the EAST cryogenic system

The size of the heat exchanger is an important factor determining the dimensions of the cold box in helium cryogenic systems. In this paper, a counter-flow multi-stream plate-fin heat exchanger is optimized by means of a spatial interpolation method coupled with a hybrid genetic algorithm.Compared with empirical correlations, this spatial interpolation algorithm based on a kriging model can be adopted to more precisely predict the Colburn heat transfer factors and Fanning friction factors of offset-strip fins. Moreover, strict computational fluid dynamics simulations can be carried out to predict the heat transfer and friction performance in the absence of reliable experimental data. Within the constraints of heat exchange requirements, maximum allowable pressure drop, existing manufacturing techniques and structural strength, a mathematical model of an optimized design with discrete and continuous variables based on a hybrid genetic algorithm is established in order to minimize the volume. The results show that for the first-stage heat exchanger in the EAST refrigerator, the structural size could be decreased from the original2.200？×？0.600？×？0.627（m^3） to the optimized 1.854？×？0.420？×？0.340（m3）, with a large reduction in volume. The current work demonstrates that the proposed method could be a useful tool to achieve optimization in an actual engineering project during the practical design process.

ADS Injector-I 2 K superfluid helium cryogenic system

The Accelerator Driven Sub-critical(ADS)system is a strategic plan to solve the nuclear waste problem for nuclear power plants in China.High-energy particle accelerators and colliders contain long strings of superconducting devices,superconducting radio frequency cavities,and magnets,which may require cooling by 2 K superfluid helium(HeliumⅡ).2 K superfluid helium cryogenic system has become a research hot spot in the field of superconducting accelerators.In this study,the ADS Injector-I 2 K cryogenic system is examined in detail.The cryogenic system scheme design,key equipment,and technology design,such as the 2 K Joule–Thomson(J–T)heat exchanger and cryomodules CM1+CM2 design,are examined,in addition to the commissioning and operation of the cryogenic system.The ADS Injector-I 2 K cryogenic system is the first 100 W superfluid helium system designed and built independently in China.The ADS proton beam reached 10 Me V at 10 m A in July 2016 and 10 Me V at 2 m A in continuous mode in January 2017 and has been operated reliably for over 15,000 h,proving that the design of ADS Injector-I 2 K cryogenic system,the key equipment,and technology research are reasonable,reliable,and meet the requirements.The research into key technologies provides valuable engineering experience that can be helpful for future projects such as CI-ADS(China Initiative Accelerator-Driven System),SHINE(Shanghai High Repetition Rate XFEL and Extreme Light Facility),PAPS(Platform of Advanced Photon Source Technology),and CEPC(Circular Electron-Positron Collider),thereby developing national expertise in the field of superfluid helium cryogenic systems.

Cryogenic system design for HIAF iLinac

A helium cryogenic system is designed by the Institute of Modern Physics,Chinese Academy of Sciences,to supply different cooling powers to the cryomodules of ion-Linac(iLinac)accelerator,which serves as the injector of the High Intensity Heavy-Ion Accelerator Facility project.The iLinac is a superconducting heavy-ion accelerator approximately 100 m long and contains 13 cryomodules cooled by superfluid helium.This article describes the cryogenic system design of the iLinac accelerator.The requirements of the cryogenic system,such as cooling mode,refrigeration temperature,operating pressure and pressure stability,are introduced and described in detail.In addition,heat loads from different sources are analyzed and calculated quantitatively.An equivalent cooling capacity of 10 kW at 4.5 K was determined for the cryogenic system according to the total heat load.Furthermore,a system process design was conducted and analyzed in detail.Further,the system layout and the main equipment are presented.

Cryogenic System for PKU-FEL

PKU-FEL based on superconducting (SC) accelerator facility is under construction at PekingUniversity. It will run in IR (5 - 10 μm) and THz (100 - 3000 μm) region as an ideal experimental FEL platform for universities. The SC accelerator facility is composed of a DC-SC injector and a 1.3-GHz 2 × 9-cell SC accelerator. In order to better the performance, the injector and the accelerator are bath-cooled by 2 K super fluid helium in cryostats. A 2 K cryogenic system has been designed, constructed and assembled.

6-31 Progress of Cryogenic System in 2014

During the year of 2014, the work of cryogenic group was mainly focused on operation of refrigerator system,test of TCM1, design and machining of HCM6. At the end of 2014 refrigerator system has achieved closed-loopoperation and recycle of helium gas, which did great contribution to superconducting cavity and superconductingmagnet test. Since the refrigerator was put into use(Fig. 1), it has operated continuously and reliably for more than5 110 h, reached helium lique ed capacity 270 L/h at 850 W.

6-22 Cryogenic System at IMP in 2015

In 2015, the work of cryogenic group mainly focused on HCM6 and the operation of cryogenic system in ADS injector Ⅱ.Last year we completed the design, assembling and running of HCM6-1. And it has been running 2 376 h stably. ADS injector II got proton beam with 11 mA@CW for 1 h. Fig. 1 shows the Assembling of HCM6-1. The temperature, pressure, helium level can be read and written in HCM6-1.

Reliable ferroelectricity down to cryogenic temperature in wakeup free Hf_(0.5)Zr_(0.5)O_(2)thin films by thermal atomic layer deposition

The performance and reliability of ferroelectric thin films at temperatures around a few Kelvin are critical for their application in cryo-electronics.In this work,TiN/Hf_(0.5)Zr_(0.5)O_(2)/TiN capacitors that are free from the wake-up effect are investigated systematically from room temperature(300 K)to cryogenic temperature(30 K).We observe a consistent decrease in permittivity(εr)and a progressive increase in coercive electric field(Ec)as temperatures decrease.Our investigation reveals exceptional stability in the double remnant polarization(2P_(r))of our ferroelectric thin films across a wide temperature range.Specifically,at 30 K,a 2P_(r)of 36μC/cm^(2)under an applied electric field of 3.0 MV/cm is achieved.Moreover,we observed a reduced fatigue effect at 30 K in comparison to 300 K.The stable ferroelectric properties and endurance characteristics demonstrate the feasibility of utilizing HfO_(2)based ferroelectric thin films for cryo-electronics applications.

Bio-Based Rigid Polyurethane Foams for Cryogenic Insulation

Cryogenic insulation material rigid polyurethane(PU)foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled polyethylene terephthalate were used to develop rigid PU foam formulations.The 4th generation physical blowing agents with low global warming potential and low ozone depletion potential were used to develop rigid PU foam cryogenic insulation with excellent mechanical and thermal properties.Obtained rigid PU foams had a thermal conductivity coefficient as low as 0.0171 W/m·K and an apparent density of 37-40 kg/m^(3).The developed rigid PU foams had anisotropic compression strength properties,which were higher parallel to the foaming direction.Moreover,the compression strength was also influenced by the type of applied bio-based polyol.The bio-based polyols with higher OH group functionality delivered higher crosslinking density of polymer matrix;thus,the mechanical properties were also higher.The mechanical strength of the foams increased when materials were tested at liquid nitrogen temperature due to the stiffening of the polymer matrix.The thermal properties of the developed materials were determined using differential scanning calorimetry,dynamic mechanical analysis,and thermogravimetric analysis methods.Lastly,the developed rigid PU foams had good adhesion to the aluminium substrate before and after applying cyroshock and an excellent safety coefficient of 4-5.Rigid PU foams developed using Solstice LBA delivered adhesion strength of~0.5 MPa and may be considered for application as cryogenic insulation in the aerospace industry.

EAST Cryogenic Supervisory and Control System Based on Delta-V DCS

The control system for the Experimental Advanced Superconductive Tokamak （EAST） cryogenic system is designed and constructed based on Delta-V DCS （Distribution Control System）, which consists of engineering workstations, operator workstations, application workstations, redundant controller units, input/output （I/O） cards and a redundant control network. Our task is to design a supervisory and control system to provide the operator interface for control and monitoring, sending alarms, archiving of selected signals, and other routines to analyze realtime and historic data. The hardware configuration, software structure and control algorithms are illustrated in detail in this paper. Hvpothetic oroblems and further research are also mentioned.

Numerical analysis of the static performance of an annular aerostatic gas thrust bearing applied in the cryogenic turbo-expander of the EAST subsystem

The EAST superconducting tokamak, an advanced steady-state plasma physics experimental device, has been built at the Institute of Plasma Physics, Chinese Academy of Sciences. All the toroidal field magnets and poloidal field magnets, made of NbTi/Cu cable-in-conduit conductor, are cooled with forced flow supercritical helium at 3.8 K. The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of coils, structures, thermal shields, bus-lines, etc. The high-speed turbo-expander is an important refrigerating component of the EAST cryogenic system. In the turbo-expander, the axial supporting technology is critical for the smooth operation of the rotor bearing system. In this paper, hydrostatic thrust bearings are designed based on the axial load of the turbo-expander. Thereafter, a computational fluid dynamics-based numerical model of the aerostatic thrust bearing is set up to evaluate the bearing performance. Tilting effect on the pressure distribution and bearing load is analyzed for the thrust beating. Bearing load and stiffness are compared with different static supply pressures. The net force from the thrust bearings can be calculated for different combinations of bearing clearance and supply pressure.

Study on cooling process of cryogenic system for superconducting magnets of BEPCⅡ

In the upgrade project of the Beijing Electron Positron Collider （BEPC Ⅱ ）, three superconducting magnets are employed to realize the goal of two orders of magnitude higher luminosity. A cryogenic system with a total capacity of 0.5 kW at 4.5 K was built at the Institute of High Energy Physics （IHEP） to support the operations of these superconducting devices. For preparing the commissioning of the system, the refrigeration process was simulated and analyzed numerically. The numerical model was based on the latest engineering progress and focused on the normal operation mode. The pressure and temperature profiles of the cryogenic system are achieved with the simulation. The influence of the helium mass flow rates to cool superconducting magnets on the thermodynamic parameters of their normal operation is also studied and discussed in this paper.

A New Method for Determining Fluid Compositions in the H_2O-NaClCaCl_2 System with Cryogenic Raman Spectroscopy

Raman peaks of various hydrates in the H20-NaCl-CaCl2 system have been previously identified, but a quantitative relationship between the Raman peaks and XNaCl （i.e.,NaCl/ （NaCl＋CaCl2）） has not been established, mainly due to the difficulty to freeze the solutions. This problem was solved by adding alumina powder to the solutions to facilitate nucleation of crystals. Cryogenic （-185℃） Raman spectroscopic studies of alumina-spiced solutions indicate that XNaCl is linearly correlated with the total peak area fraction of hydrohalite. Capsules of solutions made from silica capillary were prepared to simulate fluid inclusions. Most of these artificial fluid inclusions could not be totally frozen even at temperatures as low as -185℃, and the total peak area fraction of hydrohalite is not correlated linearly with XNaCI. However, the degree of deviation （△XNaCl） from the linear correlation established earlier is related to the amount of residual solution, which is reflected by the ratio （r） of the baseline ＂bump＂ area, resulting from the interstitial unfrozen brine near 3435 cm^-1, and the total hydrate peak area between 3350 and 3600 cm^-1. A linear correlation between △XNaCl and r is established to estimate XNaCl from cryogenic Raman spectroscopic analysis for fluid inclusions.

Design and Implementation of Quench Protection in the EAST Cryogenic Control System

An outline of the complete design of the cryogenic system, including the detection of quench signals, the processing flow after a quench and the concrete measures of pressure release for EAST is described in this paper. The hardware and software configurations on DeltaV DCS are illustrated in detail. The results of quench protection testing in cooling experiments are also analyzed.

Determining Fluid Compositions in the H_2O-NaCl-CaCl_2 System with Cryogenic Raman Spectroscopy:Application to Natural Fluid Inclusions

Previous cryogenic Raman spectroscopic analysis of H_2O-NaCl-CaCl_2 solutions has identified the Raman peaks of various hydrates of NaCl and CaCl_2,and established a linear relationship between Raman band intensity of the hydrates and the composition of the solution（NaCl/（NaCl＋CaCl_2） molar ratio,or X_（NaC1）） using synthetic fluids,which created the opportunity to quantitatively determine the solute composition of aqueous fluid inclusions with cryogenic Raman spectroscopy.This paper aims to test the feasibility of this newly established method with natural fluid inclusions.Twenty-five fluid inclusions in quartz from various occurrences which show a high degree of freezing during the cooling processes were carefully chosen for cryogenic Raman analysis.X_（Na）Cl was calculated using their spectra and an equation established in a previous study.These inclusions were then analyzed with the thermal decrepitation-SEM-EDS method.The X_（NaCl） values estimated from the two methods show a 1：1 correlation,indicating that the new,non-destructive cryogenic Raman spectroscopic analysis method can indeed be used for fluid inclusion compositional study.

A 400 MHz Low Noise Amplifier at Cryogenic Temperature for Superconductor Filter System

A cryogenic low noise amplifier （LNA） using Agilent high electron mobility transistor （HEMT） for 380 MHzto 480 MHz is designed and fabricated, and the excellent cryogenic performance in superconducting receiver front-end for communication system is achieved. A special input impedance matching topology is implemented to provide low noise figure （NF） and good input matching in this cryogenic LNA design. The measurement results show that the NF is within 0.25 dB from the minimum NF of a single transistor, the power gain is above 20 dB, the flatness is within 1 dB, and the maximum input return loss is lower than -20 dB in bandwidth.

Utilizing natural cryogenic resources to improve the stability of natural-technical systems in the permafrost zone

Siberia and the Russian Far East contain about 75% of the country's hydrocarbon and mineral resources. These regions pose many engineering and environmental problems for economic development due to the cold climate and difficult geologic conditions, including the occurrence of permafrost. One of the major challenges in permafrost areas is to maintain the stability of both individual structures and large-scale engineering projects. The use of natural cryogenic resources of the Earth is proposed here as one possible solution.