Site:           National Laboratory for High Energy Physics (KEK)
                Research Cooperation Division
                1-1 Oh'ho, Tsukuba-shi
                Ibaraki-ken 305, Japan
                http://www.kek.jp/
Date Visited:   5 June 1996
WTEC Attendees: R. Schwall (report author), 
                R.D. Blaugher, 
                J. Daley, 
                G. Gamota, 
                H. Morishita, 
                R. Sokolowski
Hosts:          Yoshitaka Kimura, Vice Director
                Dr. Takakazu Shintomi, Professor
                Dr. Hiroshi Morita, Professor
                Dr. Akira Yamamoto, Professor
                Dr. Kiyosumi Tsuchiya, Professor
                Dr. Shinji Mitsunobu, Professor
                Dr. Kenji Hosoyama, Professor
                Dr. Shuichi Noguchi, Professor
                Dr. Eiji Ezura, Professor

BACKGROUND

The National Laboratory for High Energy Physics (KEK) was established in 1971 as the first Interuniversity Research Institute under the Science Council of the Ministry of Education, Science, and Culture (Monbusho). Its purpose is experimental research in elementary particle physics and other related studies. Its principal accelerators are a 12 GeV proton synchrotron, 2.5 GeV electron accelerator, and 30 GeV electron positron collider (TRISTAN). In addition to high energy physics, extensive studies of material and life science are executed with these accelerators.

In FY 1994 the budget totaled ¥27,228 million, of which ¥4,924 million was for salaries, ¥20,306 million for operating costs, and ¥1,998 million for capital improvements. The laboratory has about 650 total staff, of which about 540 are technical personnel.

SUPERCONDUCTIVITY PROGRAM

At the time of the WTEC visit, KEK had a limited program in HTS but wide-ranging efforts in applications of superconductivity to high energy physics. Of particular note is the extensive work in large helium cryogenic systems. The program is characterized by collaborations worldwide, and KEK representatives presented a very complete and helpful overview of those programs to the visiting WTEC team. A summary of the programs follows.

Magnet R&D for LHC

A CERN-KEK cooperation has been established for basic R&D on high field dipoles and the development of insertion quadrapoles. The dipole work is complementary to that at CERN, and a 50 mm single aperture short model has reached 10.3 T. The insertion quads for the two insertion regions will be developed in Japan; a design study for the model magnets was underway at the time of the WTEC team's visit. The first model magnet was to be constructed in 1996, two additional model magnets were to be constructed in 1997, and two prototype magnets were to be completed by 1998. Production of the insertion quads is to start in 2000, with 16 magnets to be completed by 2002.

Magnet R&D for KEKB B-Factory

The next major accelerator to be commissioned at KEK is the KEKB B-Factory. Work in superconductivity and cryogenics is centered on four tasks:

1. layout of the interaction region
2. compensation solenoid
3. final focus quadrapole
4. cooling system

Significant and detailed results on all four areas were presented to the WTEC team, and this work has been well documented in the high energy physics literature. Of particular interest to the team was the detailed experience with the cryogenic system for the TRISTAN superconducting rf cavities over a seven-year period from October 1988 to June 1995. The detailed failure analysis on this system is perhaps one of the most complete available on any large cryogenic refrigeration system.

Detector Magnet R&D

KEK has constructed and used a series of ever more sophisticated detector magnets since 1984. These magnets are particularly challenging because of the simultaneous and conflicting requirements for high magnetic field, a highly transparent winding and cryostat, high mechanical strength, and high thermal stability.

The design approach at KEK has involved using aluminum-stabilized Nb-Ti conductor, very thin windings (often with no bobbin), and conduction cooling from the ends of the coil to eliminate the less transparent components of the cryostat. Table KEK.1 gives a historical listing of the coils fabricated to 1996 and those that are planned. Details on each magnet have been published in the technical literature.

LTS Superconducting Cavity Development

KEK is engaged in a variety of R&D projects on superconducting cavities made of Nb. These cavities were used on TRISTAN and will be used on the KEK B-Factory. KEK, in collaboration with CEBAF, has developed relatively low-cost reliable methods for fabricating high Q, high gradient, accelerator cavities. Again, the technical details have been published by the KEK group.

HTS Cavity Development

The only currently active HTS project at KEK is an effort to measure the microwave properties of HTS films with the intent to apply them to accelerating cavities for future high energy physics machines. This work, in collaboration with NRIM and selected commercial companies that prepare the HTS films, involves measuring the surface resistance of films at 3 GHz and 13 GHz. The measurements are accomplished by fabricating a copper cavity with provision for mounting a HTS film in one end (Fig. KEK.1). The surface resistance is inferred by measurement of the cavity properties with a network analyzer; hence, the fields at the HTS film are rather low.

Table KEK.1
Superconducting Solenoids for Collider Experiments

* Air core solenoid; D-bore = D-coil -- 0.2 m, typically

Fig. KEK.1. Experimental set-up of surface resistance measurement.