Hamlet Khodzhibagiyan

Optimization of a superferric nuclotron type dipole for the GSI fast pulsed synchrotron

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.

Design of new hollow superconducting NbTi cables for fast cycling synchrotron magnets

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.

Superconducting Magnets for the NICA Accelerator Complex in Dubna

NICA is the new accelerator complex being under design and construction at JINR. The facility is aimed at providing collider experiments with heavy ions up to Uranium in a center of mass energy range from 4 to 11 GeV/u and an average luminosity up to 1027 cm-2 · s-1. The collisions of polarized deuterons are also foreseen. The facility includes two injector chains, a new superconducting Booster synchrotron, the existing 6 A · GeV superconducting synchrotron-Nuclotron, and the new superconducting Collider consisting of two rings of about 500 m circumference each. The Booster synchrotron and the NICA Collider are based on an iron-dominated “window frame”- type magnet with a hollow superconductor winding analogous to the Nuclotron magnet. The status of the design and construction of the full size model magnets for the Booster synchrotron as well as for the NICA Collider is presented.

Fast Ramped Superferric Prototypes and Conclusions for the Final Design of the SIS 100 Main Magnets

The 100 Tm synchrotron SIS 100 is the core component of the Facility of Antiproton and Ion Research (FAIR). An intensive R&D allowed reducing the AC losses considerably as well as improving the field quality. High priority was also given to the investigation of the mechanical stability of the superconducting coil to guarantee a long term life time of at least 20 years with more than 2middot108 operation cycles and to position the cable windings precisely. Prototype magnets were built last year with the first dipole magnet completed by Babcock Noell GmbH and currently being under preparation for intensive testing. After a brief description of the main R&D results the key features of three full scale dipoles and a quadrupole prototype are given as well as the expected heat load at 4 K for the 3 m long dipoles for the most important operation modes requested for the SIS100 accelerator. During prototyping additional, more intensive operation cycles were requested by beam dynamics and more cooling power by the vacuum requirements. The consequences for the cooling stability of the dipoles were estimated and preliminary tested on a hydraulic equivalent magnet system and will be verified by the upcoming measurements of the full size models. Necessary modifications for the series production are discussed and the actual chosen SIS100 dipole design fulfilling also the additional operation requirements is outlined.

Some aspects of cable design for fast cycling superconducting synchrotron magnets

The worlds 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.

Superferric model dipole magnet with the yoke at 80 K for the GSI future fast cycling synchrotron

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.

Superconducting Magnets for the NICA Accelerator Collider Complex

NICA is a new accelerator collider complex under construction at JINR. The facility is aimed at providing collider experiments with heavy ions up to Uranium in a center of mass energy range from 4 to 11 GeV/u and an average luminosity up to 1027 cm -2 s-1. The collisions of polarized deuterons are also foreseen. The facility includes two injector chains, a new superconducting booster synchrotron, the existing 6 AGeV superconducting synchrotron Nuclotron, and a new superconducting collider consisting of two rings, each of about 500 m in circumference. The booster synchrotron and the NICA collider are based on an iron-dominated “window frame”-type magnet with a hollow superconductor winding analogous to the Nuclotron magnet. The status of the development of the full size model magnets for the booster synchrotron as well as for the NICA collider is presented. The test results of model magnets are discussed. The status of the creation of a facility for serial tests of superconducting magnets for the NICA project is described.

Full Size Model Magnets for the FAIR SIS100 Synchrotron

The planned FAIR synchrotron SIS100 has to deliver high intensity beams. Following the JINR Nuclotron, GSI has chosen to build this machine using fast-cycling 4 T/s, 2 T superferric magnets. Cycle repetition rates of about 1 Hz cause high AC power losses in the magnet components. Eddy currents deteriorate the field quality. After millions of operation cycles and high radiation flux the coil support structure can loose mechanical stability. Therefore these effects were analyzed to warrant the magnets performance over its lifetime. Following intensive experimental and computational investigations on short test models three full size dipoles and a 1.2 m long quadrupole with a maximum field gradient of 27 T/m in the aperture of 135 mm 65 mm will be manufactured until the end of 2007. Two of the dipoles are straight 2.7 m long 2.1 T magnets with a beam aperture of 130 mm 60 mm (width x height), while the third one is a curved 1.9 T dipole 3.0 m long with a reduced horizontal aperture of 115 mm. All the models use a superconducting hollow NbTi/Cu composite cable cooled with two-phase helium flow. The main design features and estimated operation parameters are given. In parallel preliminary tests of a 2.8 m SIS100 equivalent dipole system was performed. The cooling stability of the system at different SIS100 operation cycles was checked experimentally for the first time. These results are discussed as well as possible design options to fulfil additional operation requirements.

New Design for the SIS100/300 Magnet Cooling

Two superconducting synchrotrons, SIS100 and SIS300, are planned for the new International Accelerator Facility of Antiprotons and Heavy Ions (FAIR) at GSI, Darmstadt. These accelerator rings, operating at liquid helium temperatures, are placed in one tunnel of 1100 m length. The SIS100 structural superferric dipoles and quadrupoles are based on the Nuclotron-type hollow NbTi composite multi wire cable and cooled in parallel with two-phase helium flows. The peak operating mode for the SIS100 dipoles corresponds to Bmax=2 T, dB/dt=4 T/s, f=1 Hz. Fast-ramped dipoles ( dB/dtap1 T/s, fap0.05 Hz) with a field strength of 4 T and above are required for the SIS300 ring. A 4.5 T, costhetas-style, curved magnet with a coil made of a high current hollow cable cooled with two-phase helium flow is proposed for SIS300. The necessary modifications of the magnet cooling scheme are presented and discussed. General optimization of the SIS100/300 cryogenic system namely cooling with three refrigerators, the number of parallel channels, the length of helium transfer lines, and a closed nitrogen loop for the heat shield cooling is considered. The new design will make it possible to reduce the FAIR project cost

Status of the SC Magnets for the SIS100 Synchrotron and the NICA Project

The upcoming machines, the SIS100 accelerator and the NICA booster and collider are a direct offspring of the successful NUCLOTRON magnet concept. SIS100 is now being realized with the dipoles ordered. NICA is in its R&D stage with the first prototype magnets built. The experience gained in the GSI-JINR collaboration dedicated to improving the magnets during the last decade of R&D led now to the common agreement to realize the magnet production and testing in a cooperation for both projects. We describe the parameters, the optimization and tradeoffs made for these magnets and outline the differences. The status of the different magnets next to first results obtained on model or prototype magnets are given. Special attention is given to the advantages of cooling the superconducting magnets with a forced two-phase Helium flow.