A. Kabe

RF systems for the KEK B-Factory

This paper describes the design features and operational status of the RF systems for the KEK B-Factory (KEKB). Two types of new RF cavities have been developed to store very high-intensity beams with many short bunches. The design and performance of the cavities and other critical components, such as the input couplers and HOM dampers, are reported. The configuration of the RF systems is given and descriptions of various control loops are made, including a direct RF feedback loop and a 0-mode damping loop. The effects of transient beam loading due to a bunch gap on bunch phase modulations were simulated and measured. The development of a superconducting crab cavity, which is a component of luminosity upgrade strategy, is also presented.

Development of a High Performance Transfer Line System

High performance transfer lines are key components for design and construction of cryogenic systems for superconducting magnets and cavities. We have developed two types of high performance transfer lines; main transfer lines with liquid helium flow and cold gas return dual path and sub-transfer line with single path, all helium lines in these are guarded by 80K liquid nitrogen cooled thermal shields. We have adopted the aluminum molding made by extrusion for the 80K thermal shields. The structure of the transfer lines was designed to be easy to assemble. The performance of these transfer lines were tested. The heat loss of the main transfer lines at straight section are 0.04W/m and 0.06W/m for supply and return line, respectively.

A Status Report on the Development of 5-cm Aperture, 1-m Long SSC Dipole Magnet at KEK

The design and construction of a series of eleven 5-cm aperture, 1-m long SSC model dipole magnets KEK#1-#11 was started in May 1990. We have paid much attention to the design of magnet end part and developed new-type end spacers1 which have constant perimeter profiles to minimize internal stress of the cables at the coil end. Except for length, these short magnets have the same baseline design and features as the long magnet. We have performed the quench test, ramp rate quench dependence, and AC loss measurement in 1.8K superfluid helium cryostat.3

Cryogenic system for TRISTAN superconducting RF cavities

The superconducting RF cavities (32 × 5 cell) will be installed in TRISTAN electron-positron collider at KEK to upgrade the electron-positron beam energy up to 33 GeV × 33 GeV. Two 5-cell cavities are coupled together, enclosed in a cryostat and cooled by liquid helium pool boiling. Cryogenic system for the superconducting RF cavities was designed. The capacity of helium refrigerator is 4 kW at 4.4 K with liquid nitrogen precooling and two expansion turbines. The present system is designed to be easily upgraded to 6.5 kW without liquid nitrogen with an addition of expansion turbines and compressors.

Cryogenic System for the Tristan Superconducting RF Cavities: Performance Test and Present Status

The cryogenic system for the TRISTAN superconducting RF cavities (SCC) was constructed and commissioned successfully. Sixteen 5-cell SCC in 8 cryostats were installed in the TRISTAN electron-positron collider at KEK. The cryostats were connected to the helium refrigerator (4 kW at 4.4 K) through a helium transfer line (total length about 330 m) and cooled by pool boiling liquid helium. It took about 3 days to cool down the 16 SCC, a total cold mass of about 8000 kg, from room temperature to liquid helium temperature and 1 day to fill the liquid helium up to about 830 L in each SCC cryostat. The liquid helium level and the pressure fluctuation due to the RF losses in the cryostats were automatically controlled by liquid supply valves and the compensation heaters in the cryostats respectively. The performance test, the present equipment status of the cryogenic system and the six months of operational experience are described.

Upgrading of TRISTAN by superconducting RF system

The energy upgrade of TRISTAN by a superconducting RF system is progressing. Sixteen five-cell 508 MHz cavities made of niobium have been installed and started to operate in November 1988. Superconducting cavities have raised the energy of e/sup -/e/sup +/ to 30.4 GeV from 28.5 GeV with a normal conducting RF system. Construction, vertical tests, horizontal tests and three months of operational experience are described.<<ETX>>

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.

Cryogenic System for KEKB Superconducting RF Cavities

KEKB (KEK B-Factory) is a double-ring electron-positron collider used for studies of CP-violation and other topics on decays of B mesons. Because of the high beam current of KEKB, installation of superconducting cavities has been proposed for the KEKB, and 4 niobium single-cell superconducting cavities were installed in the KEKB ring in the summer of 1998. For cooling of these cavities, an existing cryogenic system with a capacity of 8 kW at 4.4 K and helium transfer lines, which were constructed and used for TRISTAN superconducting cavities, were reused. In this system newly developed, high performance, sub-transfer lines cooled with 80 K liquid nitrogen thermal shields were chosen and constructed to connect the cavity cryostats with the main transfer line. The operation of the complete system for the commissioning of KEKB was initiated at the end of 1998. This paper describes the cryogenic system and the operating experience gained during the commissioning.

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.

Quench Characteristics 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 end design and cable have been designed and fabricated at National Laboratory for High Energy Physics (KEK).1,2,3 The ramp-rate-dependent quench tests of the magnets KEK#3 to #15 were performed in a 4.2-K vertical cryostat. A ramp-rate-dependent test of the magnet KEK#6′ was also performed in 1.7-K pressurized superfluid helium. Special ramp tests so called “heating” and “cooling” experiments4 were also performed on the magnet KEK#10, as well as heat induced quench tests using the spot heaters installed in midplane of inner coils of the magnets KEK#7′ and #15 and in the splice part of the magnet KEK#13Y.