Yoshiyuki Morita

Performance of the eight superconducting quadrupole magnets for the TRISTAN low-beta insertions

The low-beta insertion quadrupoles are iron-free superconducting magnets with an inner coil diameter of 140 mm, an effective length of 1.14 m, and a nominal gradient of 70 T/m. The coils, which are of the cos 2 Theta type, are made from four layers of 27-strand NbTi Rutherford-type cable with Kapton insulation and are firmly clamped with 316LN stainless steel collars. Following the development of prototype magnets, eight magnets have been produced and were thoroughly tested and measured prior to installation in the TRISTAN main ring. A brief description of the design and manufacturing technique and the results of tests and measurements are presented.

Fabrication and Testing of 1-M-Long SSC Model Dipole Magnets

A series of fifteen 5-cm-aperture, 1-m-long, SSC model dipole magnets with various types of cable have been designed and fabricated at the National Laboratory for High Energy Physics (KEK). These magnets have been quench tested in a 4.2-K vertical cryostat and a 1.8-K pressurized-superfluid cryostat. In order to improve the quench characteristics of the magnets, we have carried out modifications of the coil end and splice design. We will describe the basic features of the magnet design, the various fabrication steps of the magnets, and results of quench tests.

Superconducting quadrupole magnet system for TRISTAN mini-beta insertions

Superconducting quadrupoles for the mini-beta insertions were installed close to every interaction point and their performances were tested successfully. The system consists of four subsystems, which can be operated individually at the local control rooms located near the subsystems and/or at the remote central cryogenic control room.<<ETX>>

Field measurement of superconducting quadrupole magnets for TRISTAN mini-beta insertions

Eight superconducting quadrupole magnets for TRISTAN minibeta insertions (QCS) have been measured by the rotating coil method before installation in the TRISTAN electron-positron colliding ring. Following the alignment of the magnet to the measuring system by use of a movable QCS-support, harmonics and field gradients were measured as functions of current and the median plane was determined for each magnet. Details of the measuring systems and results of the measurements are presented. The results of the field measurements show that the relative errors of the integral field gradient can be kept within +or-0.001 for all the magnets and that the higher multipole components are small enough for the tolerance required to the QCS.<<ETX>>

Cryogenic System for TRISTAN Superconducting RF Cavities: Description and Operating Experience

Publisher Summary A large scale helium refrigeration system was constructed and operated for about 7 years for superconducting RF accelerating cavities (SCC) in TRISTAN electron positron collider at National Laboratory for High Energy Physics (KEK). The 32 x 5 cell 508 MHz SCC in 16 cryostats were installed in TRISTAN electron-positron collider at KEK for further upgrading of the beam energy, from 27 GeV to 32 GeV. This chapter provides a short description of the main components of the cryogenic system together with the operating experience gained during the commissioning and 7 years operation. The total number of failures in the cryogenic system during about 7 years operation was 85. The experience in long operation of the large cryogenic system shows the compressor is the key component and the regular maintenance of the system including utilities is essential to attain the system reliability.

Magnetic Field Measurement of Superconducting Dipolemagnets with Harmonic Coil and Hall Probe

Magnetic field measurements and field analyses of 1-m long superconducting dipole magnets fabricated at the National Laboratory for High Energy Physics (KEK) have been carried out using a harmonic coil with the bucking scheme.1 Conditions of the data acquisition are optimized to achieve the accurate and efficient measurements. Not only in the steady state of the magnet excitation by constant currents, but also on the way the excite current increases until the magnet quenches the field measurements have been tried, and the results are discussed in this paper on the possibility of the “on-the-fly” measurement using a harmonic coil. Some results on the so-called remnant field of the magnets measured with a Hall probe are also described.

Operational Experience and Reliability of the Cryogenic Systems for the Tristan Insertion Quadrupole Magnets

Four sets of helium cryogenic systems for the mini-beta insertion quadrupole magnets were installed near the interaction points of the TRISTAN main ring in 1990. Each system consists of a helium compressor, a cold box, a subcooler, transfer lines, two magnet-cryostats, two helium gas tanks and a liquid nitrogen storage tank, and its nominal cooling capacity is 140 W at 4.2 K + 25 L/h. The four systems are controlled automatically by a process control computer system. The first operation started in 1991 and by the middle of 1995, the total operating time for each system reached about 28,000 hours. In this paper we report the experience gathered during 28,000 × 4 operating hours in running four cryogenic systems together with the control system. Maintenance experience and statistics of failures of different components are also described.

Mini-beta superconducting quadrupole magnet system for the TRISTAN main ring

The design parameters of the superconducting quadrupole magnets for the mini-beta insertions of the TRISTAN main ring are given. The performance of the QCS magnets and cryogenic systems is described. >