[en] In order to develop the superconducting cavity for the International Linear Collider, a superconducting RF test facility (STF) has been proposed and the construction has just started at KEK. This paper briefly explain the present status of the cryostat that will be a main equipment of the STF, and also gives a short review of the cryogenic system of the TESLA, since the cryostat design has a close connection with the cryogenic system. (author)

[en] Forty-three superconducting (SC) correction coils with maximum currents of about 60 A are installed in the SuperKEKB final focusing magnet system. Current leads to energize the SC correction coils should have an affordable heat load and fit the spatial constraints in the service cryostat where the current leads are installed. To address the requirements, design optimization of individual lead was performed with vapor cooled current lead made of a brass material, and a compact unit was designed to accommodate eight current leads together in order to be installed with one port in the service cryostat. The 2nd generation high temperature SC (HTS) tape was adopted and soldered at the cold end of the brass current lead to form a hybrid HTS lead structure. A prototype of the compact lead unit with HTS tape was constructed and tested with liquid helium (LHe) environment. This paper presents a cryogenic measurement system to simulate the real operation conditions in the service cryostat, and analysis of the experimental results. The measured results showed excellent agreement with the theoretical analysis and numerical simulation. In total, 11 sets of the compact HTS lead units were constructed for the 43 SC correction coils at KEK. One set from the mass production was tested in cryogenic conditions, and exhibited the same performance as the prototype. The compact HTS lead unit can feed currents to four SC correction coils simultaneously with the simple requirement of controlling and monitoring helium vapor flow, and has a heat load of about 0.762 L/h in terms of LHe consumption. - Highlights: • The requirements of the SC correction coils on current leads are introduced. • The optimum design of the brass vapor cooled current lead is described. • The compact structure of eight leads with HTS tape is presented. • The theoretical, numerical, and experimental results are compared. • The current lead heat load is evaluated for cryogenic system.

[en] A heat exchanger for cooling the TRISTAN final focusing superconducting quadrupole magnet was studied. This heat exchanger could produce subcooled liquid helium of 20 g/s and 0. 16 MPa below 4.4 K with saturated liquid helium at 0.11 MPa. For the heat transfer of single phase flow in the heat exchanger, the calculations with the Dittus-Boelter and Kutateladze equations agreed well with the measurements. For the heat transfer during the condensation process, the Shah equation including vapor quality was applied. The calculated heat transfer energy was twice as large as the measured value and the vapor effect on the heat transfer coefficient was not as large as that calculated by the Shah equation

[en] The contribution of superconduction techniques to high energy physics has increased recently, and the experiment on high energy physics is no more possible if superconduction techniques are neglected. The development of superconducting magnets for a proton ring in the phase 2 of TRISTAN project of KEK, the superconducting proton synchrotron in Fermi National Accelerator Laboratory already in operation, the superconducting supercollider of 20TeV x 20TeV proton-proton in USA, and the JSC project of 30TeV x 30TeV proton-antiproton collision type accelerator are the examples. For the superconducting electromagnets of the SSC project, the full scale mass production lines will be completed. The intensity of their magnetic field is from 3T to 8T. As to the electromagnets for the JSC project, the intensity of magnetic field as high as 9T is required. The material of wires, two-layer shell type structure, cold iron and cold bore type, self correction coil and so on are discussed. The problems of electromagnetic force acting on coils and stored electromagnetic energy at the time of quenching are described. The present status and the project of superconducting electromagnet development in KEK are explained. (Kako, I.)

No abstract available

[en] Idea of the use of double cos20 winding superconducting quadrupole magnets as final focus quadrupole magnets for the KEK B-Factory is presented. This type of quadrupole produces very small leakage field outside the magnet and can minimize field disturbance at particle detectors for the B-Factory. We explain the principle of leakage field reduction and the result of field calculation

[en] A bobbinless superconducting solenoid has been constructed, and successfully excited without training up to the critical current of the conductor. The central field was 5.86 T at the maximum overall current density of 300 A/mm². The inner diameter of the windings is 19.0 cm. the outer diameter is 23.4 cm, and the length is 26.7 cm. The conductor is a NbTi/Cu keystoned compacted strand cable, of which the critical current is 4.6 kA at 6.3 T and 4.2 K. The magnet consists of two layers, namely 345 turns of edgewise windings, and a GFRP outer cylinder and two sheets of cooling channel between them. It has no metallic part except the superconducting cable, therefore it is suitable to pulsed operation. Local wire movement was reduced in this magnet, which is considered to cause training. However, the magnet deformed elastically during excitation. The strain of the windings in axial and circumferential directions, and the voltage oscillation synchronizing with the mechanical vibration of the magnet were measured. The thermal stability of the magnet was examined. The finite element analysis was performed. These results are reported. (Kako, I.)

[en] A new method has been developed to control the temperature of a 1-m cylindrical hydrogen bubble chamber at the National Laboratory for High Energy Physics, KEK. The temperature and pressure control system uses liquid hydrogen as a coolant. The system has been working successfully, keeping the bubble chamber temperature to within 0.03 K at about 26 K and the pressure to within 0.05 atm at about 5 atm. This paper describes this temperature and pressure control system and the basic operational characteristics. (author)

[en] A high-temperature superconducting (HTS) sextupole magnet was proposed for the chromaticity correction of the SuperKEKB interaction region. The magnetic field strength of the magnet was designed to be 200 T/m² at 30 K. The magnet consists of six rectangular coils wound with a REBCO conductor. Each coil has an inner radius of 75 mm and a length of 200 mm. In this paper, we present the design, fabrication, and excitation test result at 77 K and 4.2 K of the HTS sextupole magnet. As a result, we successfully excited the magnet to the design current of 250 A at 4.2 K. We also confirmed that the magnet had been fabricated with no degradation of the conductor properties. (author)

[en] Management of the ambient magnetic field is one of the key issues for a successful operation of superconducting RF cavities used in many particle accelerators. The tolerance for the ambient magnetic field depends on factors such as the operating RF frequency and acceleration gradient but it can be as low as several mG. The vacuum vessels are usually made of iron, which is expected to shield the magnetic field to some extent. There is another magnetic shield made of permalloy surrounding the cavities to reduce the ambient magnetic field to the desired level. The non-annealed iron vessel that we measured presented strong magnetization, creating a stronger magnetic field inside the vessels than the earth magnetic field. Demagnetization of the vessels was performed on-site using coils wound on the vessels. We demagnetized the vessels using two different patterns of coil windings. Demagnetization by different windings are compared and summarized in this report. (author)