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The data from the investigation of hollow superconducting cable based on keystoned NbTi wires are presented. The cable sample, consisting of 15 wires wound around a cooper-nickel tube 5 mm in diameter and cooled with two-phase helium flow has operated inside the magnet aperture at a current of 13.4 kA and the current ramp rate of 26.8 kA/s. The external magnetic field value was about 2 T and the field ramp rate of 4 T/s. The pulse repetition rate of 1 Hz was provided. The first 650 m of the new wire was manufactured based on the improved technology. A piece of hollow cable 40 m in length was fabricated. The outer cable diameter with electric insulation is 7.34 mm. A test winding for a 1.4 m superferric nucleotron-type window frame model dipole for SIS100 as part of the FAIR-project of GSI was fabricated and tested. The obtained results are discussed. The new approach to a 'cable-in-conduit' conductor cable design, based on the use of keystoned wires, is described.

The possibilities of construction superconducting synchrotron magnets with pulse repetition rate up to 20 Hz are analyzed. Different design concepts are considered. The expected AC power losses and the magnet cooling conditions are calculated based on the data which have been obtained under design, construction and long term tests of 2 T superferric dipoles of the Nuclotron at the frequencies up to f=2 Hz. New experimental data on the investigation of the dipole at higher frequencies are presented. Hollow multifilament NbTi composite cable cooled with two-phase helium flow is used. The essential features of the test bench are described.

The world's experience in application and manufacturing of superconducting cables for fast cycling synchrotrons (operating frequency f = 1 Hz) is limited up to now to a hollow multifilament NbTi cable cooled with two-phase helium flow. The cable of 7 mm in diameter has critical current of 8400 A at B = 2.5 T and dB/dt = 4 T/s. The degradation of critical current does not exceed 10% up to dB/dt = 8 T/s. The cable was designed and has been used for the magnets of the Nuclotron superconducting synchrotron at JINR in Dubna. The recent R&D was motivated by the new project of a superconducting synchrotron SIS100 at GSI in Darmstadt. Besides the basic option, i.e., the present Nuclotron-type cable, other design options are proposed. Their suitability for application in the conditions specified for the SIS 100 are considered. The improved characteristics of the Nuclotron-type cable and the magnet coil parameters are also presented.

New experimental results from the investigation of a superferric window frame type dipole magnet with the operating parameters: B=2T, dB/dt=4T/s and pulse repetition rate f=1Hz are presented. The magnet SC coil is made from a hollow multifilamentary NbTi cable, cooled with two-phase helium flow. Special attention is devoted to minimization of AC power losses in the magnet to the specified value of 13W/m. The value of 9W/m has been obtained for a model magnet with the yoke at T=50K. Different possibilities were investigated to reduce the losses in the case of a cold iron yoke (T=4.5K). Other problems, connected with the magnetic field quality, mechanical and cryogenic stability of the magnet under SIS100 operating conditions are also discussed.

Two new options for a hollow NbTi superconducting cable were considered. The first one is based on keystoned wires wrapped around a copper-nickel tube 5 mm in diameter. The second one is a hollow cable of rectangular cross section. The data from cable short sample tests are presented. Some problems with the production technology are discussed. This work is part of the R&D for the Future Accelerator Facility, at GSI in Darmstadt.

Experimental data of a fast cycling (f=1 Hz) 2T dipole magnet based on a superconducting NbTi multi filament hollow cable cooled with forced two phase helium flow at T=4.5K and iron yoke at T=80 K are presented. A new magnet design is proposed. The magnet yoke made of laminated steel consists of two parts: the internal smaller part has close mechanical and thermal contact with the coil while the outer part is separated from the cold mass with a gap of 1 mm and cooled with liquid nitrogen.

Two new prototype dipole magnets for the proposed new fast cycling (f=1 Hz) synchrotron at GSI in Darmstadt have been designed, fabricated and tested. The magnets are based on a window frame iron yoke cooled by liquid nitrogen and a superconducting winding made from a hollow NbTi composite superconductor cable cooled with forced two-phase helium flow at T=4.5 K. The cold mass of the magnet is separated from the yoke by a small vacuum gap of 0.75 mm to 2.5 mm. A decrease of ac power losses by a factor of 2.3 in comparison with a standard Nuclotron dipole is obtained. The design features of two prototype dipoles as well as the test results are presented.

GSI plans to upgrade its accelerator facilities. A fast-pulsed synchrotron (rigidity 100 Tm, dipole field/ramp rate 2T/4T/s) is one of the main parts of the GSI future project. Superconducting magnets of the Nuclotron type are foreseen for this synchrotron. R&D work has been done in order to improve the DC field quality and to reduce the cryogenic AC losses. Linear 2-D calculations were used to optimize the pole shape of the dipole magnet. Consequently, a negative shimming was introduced. Subsequent nonlinear extension led to the introduction of air slits in the iron yoke which improved the field quality at higher levels. Nonlinear 3-D simulations were then used to optimize the homogeneity of the integral field, by varying the ratio between the yoke and coil length. We built a model magnet with this optimized iron lamination cross section. In order to reduce the AC losses, we used stainless steel end plates, low coercitivity iron, better insulated iron lamination sheets and reduced the superconductor filament size to 6 /spl mu/m. Various contributions to the losses of the magnet were analyzed. Numerical calculations of the eddy current effects due to field components perpendicular to the iron laminations at the end of the magnet showed that this part must not be neglected. The magnet test results are presented and compared with the expected field quality and losses.

A superconducting magnetic system for the 250 to 500 MeV/Amu booster synchrotron of the Nuclotron is discussed. The repetition rate of the booster is 1 Hz and the circumference 84 m. There are 32 dipole and 24 quadrupole magnets with a "cold" iron yoke and a hollow superconductor winding (NbTi) in the accelerator ring. Basic parameters of the magnets, superconducting cable construction, cryogenic system and cryomagnetic assembly design are presented.

The results of the development of 2 T cold iron SC-magnet technology at the Laboratory of High Energies, JINR including a Nuclotron-type SC booster and a VLHC cryomagnetic assembly design are presented. New experimental data on the Nuclotron magnet system operation are discussed.

The performances of the installation used to measure a.c. energy losses of short superconducting samples in an external pulsed magnetic field are given. The calorimetric method at 4.2 K is used. The measurable range of losses is from 10 up to 1000 mW. The results of loss measurements of superconducting wires and tubular cables with a various diameter of superconducting filaments and twist length are presented. The experimental values of hysteresis and eddy current losses are compared with the calculated ones. The influence of the Nb barrier and solid-state diffusion on the loss values is investigated.

The new superconducting heavy ion synchrotron-Nuclotron was put into operation at the Laboratory of High Energies. The maximum design energy is 6 GeV/u. There are 160 pulsed SC magnets with a "cold" iron yoke and a hollow superconductor winding in the ring. A magnetic field of 2 T is provided under a supply current of 6 kA. The magnets were tested under a cycle dB/dt=4 T/s, B=2 T, and a ramp rate f=1.0 Hz. A two-phase helium flow was chosen as a coolant. The Nuclotron "cold" mass is about 80 tons. The cryogenic supply system capacity is 4.8 kW at 4.5 K. The total running time of the Nuclotron reached 1100 hours after the last run in March 1994. >