Search

Development of the LHC low-/spl beta/ insertion quadrupole magnet has been in progress at KEK since 1995 as a cooperative program between CERN and KEK. Five 1-m short model magnets have been fabricated and three of them have been tested. From the various test results of the first two models, the coil configuration was further optimized to reduce the higher magnetic field harmonic coefficients. The cold test of the third model showed satisfactory performances of the field harmonics. After this R&D work, the authors are at a stage for the fabrication of two prototype magnets which have the same scale as the production magnets. The status of the R&D for the LHC low-beta insertion quadrupole magnet at KEK is described.

Two superferric quadrupoles with a pole-tip radius of 170 mm and a maximum pole-tip field of 2.4 T are designed for the BigRIPS projectile fragment separator at RIKEN. Taking the feasibility of coil winding into account, the shape of quadrupole coil has been optimized.

The fabrication of the outer module has been completed, which is one of the central solenoid (CS) model coils being developed as the most important R&D for ITER construction. The inner and outer diameters are 2.8 m and 3.6 m, respectively. The weight is 63 tons. The conductor is a Nb/sub 3/Sn cable-in-conduit conductor with a square Incoloy 908 conduit. The coil that consists of 8 layers was fabricated with a solenoid winding with two conductors-in-hand. The outer module will be connected with the inner module coil in series and contribute to the generation of 13 T at 46 kA. The test will be started in November 1999.

The central solenoid (CS) model coil-outer module being fabricated to demonstrate the justification of the CS design for the ITER, was almost completed except for epoxy impregnation to concrete whole layers. All the wound and heat treated layers have been assembled symmetrically with the insulation on the same axis, and for layer-to-layer joints the newly developed butt joint, has been installed.

The Japan Atomic Energy Research Institute (JAERI) has been designing and developing the central solenoid (CS) model coil for International Thermonuclear Experimental Reactor (ITER). The CS model coil is composed of two modules and they will be manufactured by a United States Home Team and a Japanese Home Team. The coil winding method is two-conductors-in-hand and the coil, which has an inner diameter of 1.6 m and an outer diameter of 3.6 m, produces a maximum field of 13 T. The coil will be tested in the JAERI facility. This paper describes the coil design, manufacturing procedure, stress analysis on the winding pack and AC loss analysis.

The ITER coil insulation systems are required for operating voltages up to 10 kV and to support shear and normal compression loads through the winding pack. Manufacturing considerations and nuclear radiation resistance also influence the choice of suitable systems. A screening program of candidate systems is being conducted in stages. The first stage is reported in this paper. Present R&D data based on small samples indicate a static shear strength of about 85 MPa for a glass or alumina and epoxy resin vacuum pressure impregnation system and 50 MPa for a pre-impregnated glass/epoxy resin system with polyimide interleaved at a temperature of 4 K. The preliminary irradiation results show that coating the steel surface with inorganic materials such as Al/sub 2/O/sub 3/ or ZrO/sub 2//8Y/sub 2/O/sub 3/ is beneficial in increasing the radiation resistance as far as shear strength is concerned. In addition tetrafunctional epoxy (TGDM) systems appear to be more radiation resistant then diglycidyl ether of bisphenol-A (DGEBA) systems. Further R&D work will focus on prototypical samples to continue evaluation of the performance of the insulation systems.

The DPC-TJ coil is being developed so as to demonstrate the advanced technology for the next Fusion Experimental Reactor. The DPC-TJ is (NbTi)3Sn coil designed for high current density (40 A/mm2), large current (24 kA) and high field (12 T). The key issue is the development of a double-walled cable-in-conduit conductor so called “Preformed Armor Type CICC” for the high mechanical and electrical performance. These advantages were verified by a test winding fabrication and a mechanical testing. This paper describes the development work and mechanical testing for the DPC-TJ coil.

Two large Nb 3 Sn coils, so called cluster back up coil (CBC), with the dimension of 400 mmID, 840mmOD and 258 mmH, have been constructed to increase the resultant field at the cluster test facility in Japan Atomic Energy Research Institute (JAERI). The operating current is 2, 145 A at 10 T. The component and performance tests, such as the critical current, mechanical properties and cryogenic stability were extensively investigated, before the CBC fabrication. Prior to installing the CBC in the cluster test facility, an individual coil test of the CBC was carried out and the CBC were successfully operated at a rated current of 2, 145 A.

Development of low-/spl beta/ quadrupole magnets for the LHC beam interaction regions has been carried out. The magnet is designed with a field gradient of 240 T/m in a coil aperture of 70 mm, and is to be operated at /spl les/215 T/m with absorption of beam loss heating. Three 1-m models with the final design have been developed and tested with satisfying requirements of field quality and training characteristics. A full-scale (6.3-m) prototype has been developed, and is being tested. Progress of the LHC low-/spl beta/ quadrupole development at KEK is reported.