Homogeneous magnetic fields are required in different applications. The resolution of MRI techniques depends on the quality of the magnetic field, as well as the efficiency of electron cooling systems used at particle accelerators. Unclosed magnetic shield made of superconducting tapes is able to nullify the radial component of a solenoidal magnetic field, forming the long region of the homogeneous magnetic field. The shield is a lengthwise winding made from YBCO tapes are wound along a carcass generatrix. Then it is positioned coaxially inside an electromagnet. The measurements were carried out under quasistationary conditions, magnetic fields up to 1 kG at 77K. This paper discusses the design of the superconducting shield and presents experimental and numerical studies into the homogeneity of the magnetic field in solenoids with the superconducting shield.

*e-mail: dorofeevgl@mail.ru Abstract The development of high-temperature superconducting (HTS) materials, especially HTS tapes of the second generation (2G HTS tapes) give us new opportunities to use superconductivity in high-energy physics devices and, in particular, in charged particle accelerators. The influence of the unclosed magnetic shield made of 2G HTS tape on the dynamics of a charged particles beam is studied in this paper. Within the framework of the simplest model of the interaction of the magnetic field of a charged particles beam with a superconducting shield, estimates of this influence are made. The superconducting shield shifts of a charged particles beam to its axis. In particular, the beam of ions 197Au79+ energy of 4 GeV per nucleon and a current of 5 A passing at a distance of 5 10 mm from the axis of the superconducting screen with a radius of 50 mm and a length of 5 meter is shifted to the axis of the screen at a speed of about 130 m/sec. That is, the beam itself can be centered for a lot less than 1 second. The possibilities of using an unclosed superconducting shield to compress a charged particles beam are discussed, as well as the possibilities of controlling the shield.

Ensuring the high homogeneity of a magnetic field in the straight solenoid of an electron cooling system is a very important task. In the electron cooling system of the collider in the NICA project, it is planned to use superconducting solenoids for the generation of a longitudinal magnetic field. Using of the superconducting shield is proposed to achieve the required homogeneity of the magnetic field in the cooling section. This article discusses the design of the superconducting shield and presents experimental and numerical studies into the homogeneity of the magnetic field in solenoids with the superconducting shield.

Recent data from the design of new optimized options of NbTi composite wires and hollow cables for fast cycling synchrotron SIS100 at GSI and NICA collider at JINR are presented. The SIS100 new cable is proposed to be used for manufacturing of single-layer coil for dipole magnet with maximal amplitude of pulsed magnetic field up to 2 T. The cable should provide continues pulsed operation at the current amplitude of I = 13 kA and magnetic field ramp rate of dB/dt = 4 T/s. The results of experimental study of energy losses in the new wire and cable samples for SIS100 magnets are presented. The design cable parameters for the NICA 4 T dipole magnet are fixed at the level of I = 17 kA and dB/dt = 1 T/s. The status of the work is presented and discussed.

The so-called reflex mode of Electron String Ion Source (ESIS) operation has been under intense study, both experimental and theoretical at JINR during the last decade. The idea of using a tubular electron string ion source (TESIS) has been put forward recently to obtain 12 orders of magnitude increase in the ion output as compared with ESIS. The project is aimed at creating TESIS and studying an electron string in the tubular geometry. The new tubular source with a superconducting solenoid up to 5 T should be constructed in 2010. The method of the off–axis TESIS ion extraction will be used to get TESIS beam emittance comparable with ESIS emittance. It is expected that this new TESIS (Krion T1) will meet all rigid conceptual and technological requirements and should provide an ion output approaching 10 mA of Ar ions in the pulse mode and about 10 μA of Ar ions in the average current mode. Analytical, numerical study of the tubular electron strings and the design of the TESIS construction are given in this report. The experiments with quasi tubular electron beams performed on the modified ESIS Krion 2 are also discussed there. TUBULAR ELECTRON STRING ION SOURCE The Electron String Ion Source is based on a specially designed electron gun and an electron reflector that allows multiple uses of beam electrons [1-3]. At some conditions the electron string is formed with about few hundreds reflections for each electron. The electron string can be used for production of highly charged ions similarly to beam electrons. The interest in the ESIS mode was motivated by the attractive possibility of decreasing the electron beam power by a factor of 100 preserving simultaneously the same ion yield. The Krion2 ESIS has been used successfully at the injection complex of JINR synchrotron Nuclotron for production of highly charged ion beams: Ar 200 μA, Fe 150 μA in 8μs pulses (see Table 1) [3]. The idea of using TESIS was proposed in [4] to obtain a considerable increase of ion outputs (Table 1) in comparison with the ESIS and simultaneously a small ion beam emittance, usually provided by ESIS. The method of the off–axis TESIS ion extraction was proposed in [45] to get beam emittance comparable with ESIS one. In fact, the number of produced ions is proportional to the number of the stored electrons and for a given source length it is proportional to the beam cross-section area. The ratio of the stored electrons/ions in the tubular source NTESIS and in the solid cylindrical beam NESIS of the same length is NTESIS/NESIS≈4r/a≈25÷50, where a is the radial electron beam thickness and r is the main radius for the tubular electron beam. Second crucial point is that the use of tubular geometry of drift tube structure allows avoiding the virtual cathode formation for the corresponding amount of accumulated electrons in comparison to the cylindrical drift tube structure. It was found experimentally [1-3] that the maximum number of electrons Ne accumulated in a linear string was proportional to a confined magnetic field B to the third power:

The project started in 2007 is aimed at creating a Tubular Electron String Ion Source (TESIS) and to studying an electron string in the tubular geometry. The collaboration consists of JINR (Dubna) and the Russian Federal Nuclear Center (Sarov, Russia), the Manne Siegbahn Laboratory (Stockholm, Sweden), TRIUMF and the Atomic Energy of Canada Ltd. (Canada). The tubular concept of the ion source was proposed a few years ago. Preliminary theoretical estimations and numerical simulations were done, which allowed experimental realization of this project to start. The new tubular source with a superconducting solenoid up to 5 T should be constructed in 2009. It is expected that this new TESIS (Krion-T1) will meet all rigid conceptual and technological requirements and should provide an ion output approaching 10 mA of Ar ions in the pulse mode and about 10 μA of Ar ions in the average current mode. Having these output parameters, Krion-T1 should be an operational prototype of further TESIS sources for possible applications. Simulation results and a basic sketch of the TESIS construction is presented. ELECTRON STRING ION SOURCE The so-called reflex mode of Electron Beam Ion Source operation has been under intense studies, both experimental and theoretical at JINR during the last decade [1-3]. The Electron String Ion Source (ESIS) corresponding to the reflex mode of EBIS operation is based on a specially designed electron gun and an electron reflector that allows multiple use of beam electrons [1-3]. At some conditions the electron string could form that provide efficient electron accumulation with about few hundreds reflections for each electron. The electron string can be used for production of highly charged ions similarly to beam electrons. The interest in the ESIS mode was motivated by the attractive possibility of decreasing the electron beam power by a factor of 100 preserving simultaneously the same ion yield. Krion-2 ESIS has been used successfully at the injection complex of JINR synchrotron Nuclotron for production of highly charged ion beams: Ar 200 μA, Fe 150 μA in 8μs pulses (see Table 1), which were accelerated up to relativistic energies and used in physics experiments [3]. TUBULAR ELECTRON STRING ION SOURCE The idea of using a tubular electron string ion source (TESIS) has been put forward recently [4-5] to obtain 1-2 orders of magnitude increase in the ion output as compared with ESIS (Table 1). The gain of the highly charged ion input in TESIS compared with ESIS is characterized by a ratio of tubular beam diameter d to radial beam thickness a: NTESIS/NESIS=2·d/a ≈ 10-100.The main point is that use of tubular geometry of drift tube structure allows to avoid virtual cathode formation for the corresponding amount of accumulated electrons. It was found experimentally [1-3] that the maximum number of electrons accumulated in a string was proportional to a confined magnetic field B to the third power Q=aB. Increases in the magnetic field from 3 T in Krion-2 to 5 T in Krion-T1 could permit about 5 times increase in the number of stored electrons and their density. The increase in the electron density at 5T reduces the ion confinement time, which determines the injection repetion frequency. The method of the off–axis TESIS ion extraction was proposed in [4-5] to get TESIS beam emittance comparable with ESIS emittance. Table 1: Parameters of electron string ion source Ion source Krion-2 Ar TESIS Ar Electron energy, keV 3-5 5-7 Number of electrons 5⋅10 2⋅10 Magnetic field, T 3 5 Ion current, mA 0.15 10 Pulse duration, μs 8 8 Number of extracted ions 5⋅10 3⋅10 Injection frequency, Hz 1 5 Average current, μA 0.15 10 Proceedings of EPAC08, Genoa, Italy MOPC141 04 Hadron Accelerators T01 Proton and Ion Sources

Pinning and magnetic flux diffusion in composites with artificial pinning centers (APC) are studied using a magnetic step method. It is revealed experimentally, that a magnetic flux pinning is determined by boundaries of superconducting filaments and matrix in composites with thickness of filaments less of London's penetration depth. The elementary pinning force on n-s boundary for Cu-NbTi, Nb-NbTi,.. composites is measured. The value of elementary pinning force is controlled by thickness n-s boundary. And the thickness n-s of boundary can be large in result of solid state diffusion during technological process. The thickness n-s boundary is estimated through the dependence of superconducting filaments effective volume from the magnetic field value. These results for elementary pinning force and thickness n-s of boundary are compared to results of direct measurements of critical currents in these APC superconducting composites.

A new compact version of the"liquid He-free"superconducting Electron Cyclotron Resonance Ion Source,to be used as an injector for the U-400M cyclotron,is presently under construction at the FLNR in collaboration with LHE（JINR）.The axial magnetic field of the source is created by the superconducting magnet,and the NdFeB hexapole is used for the radial plasma confinement.The microwave frequency of 14GHz will be used for ECR plasma heating.The DECRIS-SC2 superconducting magnet is designed for the induction of a magnetic field on the axis of the source of up to 1.4T（extraction side）and 1.9T（injection side） at nominal current of 75A.Cooling of the coils is carried out by CM cryocooler with cooling power of 1W at the temperature 4.5K.The basic design features of the superconducting magnet and of the ion source are presented.The main parts of the source are in production.The first beam test of the source is expected in the beginning of 2007.

A new compact version of the "liquid He-free" superconducting Electron Cyclotron Resonance Ion Source, to be used as an injector for the U-400M cyclotron, is presently under construction at the FLNR in collaboration with LHE (JINR). The axial magnetic field of the source is created by the superconducting magnet, and the NdFeB hexapole is used for the radial plasma confinement. The microwave frequency of 14GHz will be used for ECR plasma heating. The DECRIS-SC2 superconducting magnet is designed for the induction of a magnetic field on the axis of the source of up to 1.4T (extraction side) and 1.9T (injection side) at nominal current of 75A. Cooling of the coils is carried out by GM cryocooler with cooling power of 1W at the temperature 4.5K. The basic design features of the superconducting magnet and of the ion source are presented. The main parts of the source are in production. The first beam test of the source is expected in the beginning of 2007.

The experimental results of curling effect investigation (sharp increasing of the normal phase propagation speed under influence of the magnetic flux avalanche) in superconducting Nb-Ti and Nb-Zr wires are presented. The external magnetic field was imposed parallel to an axis of a sample of a superconducting wire by thickness from 0.16 mm up to 0.30 mm without a normal stabilizing covering, the transport current was put, and after initiation of a normal phase on a short part of a sample the normal phase propagation and the magnetic flux avalanche along a sample were registered simultaneously. It was found, that the thickness of the magnetic flux avalanche L-mfa and the thickness of the normal phase front L-npf (length of the part of a sample engaged by S-N transition) achieves 3-4 mm, that is more than 10 diameters of the sample. The heating of a superconducting wire by the magnetic flux avalanche is accompanied by increase of the speed of normal phase propagation V-npp. In a narrow range of change of a transport current the sharp increasing of the speed of normal phase propagation V-npp up to the speed of a magnetic flux avalanche V-mfa occurs. The further increasing of a transport current is accompanied by reduction of a distance (spacing) between the normal phase and the magnetic flux avalanche. In turn V-mfa increase with increasing of critical current dencity J(c) and thickness of a superconducting wire. In particular the speeds V-mfa and V-npp achieve the value 9-13 km/s for the wire Nb-25%Zr by thickness of 0.24 mm with the critical current J(c) = 2-4 MA/cm(2) in magnetic fields 0.5-1 T.

A superconducting magnet system (SMS) for the multicharged ion source DECRIS-SC was designed and manufactured at the Joint Institute for Nuclear Research. Successful tests of the SMS were conducted in late 2003 and early 2004. The peculiarities of this system are stipulated by the use of a cryocooler 1 W in power for the cryostating of the magnet and also by the special configuration of the magnetic field demanded for the source of ions. Four coils ensure the induction of a magnetic field on the axes of the source of up to 3 T (the stopper ratio of ∼6), which considerably extends the possibilities of the ion source from the point of view of producing intense highly charged ion beams. The problem of compensating the large forces of interaction between the coils and surrounding iron yoke in this magnet has been successfully solved, and a reliable suspension of the magnet in a cryostat realized. To compound the windings, which work in vacuum at indirect cryostating, prepreg (thermosetting fiberglass fabric impregnated with epoxide) is used. A new technology of superconducting magnet protection has been applied with the help of sectionalized windings, using passive elements of protection based on “cold” diodes and resistances. A new technology of active protection has also been applied, with normal zone detectors and heaters.

A superconducting magnet system (SMS) for the multicharged ion source DECRIS-SC was designed and manufactured at the Joint Institute for Nuclear Research. Successful tests of the SMS were conducted in late 2003 - early 2004. The peculiarities of this system are stipulated by using of a cryocooler 1 W in power for the cryostabilization of the magnet, and also by a special configuration of the magnetic field demanded for the source of ions. Four coils ensure induction of a magnetic field on the axes of the source of up to 3T (the mirror ratio of ~ 6) which considerably extends possibilities of the ion source from the point of view of producing intense highly charged ion beams. The problem of compensating large forces of interaction between the coils and surrounding iron yoke in this magnet has been successfully solved, and a reliable suspension of the magnet in a cryostat realized. For compounding of the windings working in vacuum at indirect cryostabilization prepreg is used. There has been applied a new technology of the superconducting magnet protection with the help of sectionalization of the windings, using passive elements of the protection based on "cold" diodes and resistances, as well as a new technology of active protection with normal zone detectors and heaters.

A superconducting magnet system (SMS) for the multicharged ion source DECRIS-SC was designed and manufactured at the Joint Institute for Nuclear Research. Successful tests of the SMS were conducted in late 2003 – early 2004. The peculiarities of this system are stipulated by using of a cryocooler 1 W in power for the cryostabilization of the magnet, and also by a special configuration of the magnetic field demanded for the source of ions. Four coils ensure induction of a magnetic field on the axes of the source of up to 3T (the mirror ratio of ~ 6) which considerably extends possibilities of the ion source from the point of view of producing intense highly charged ion beams. The problem of compensating large forces of interaction between the coils and surrounding iron yoke in this magnet has been successfully solved, and a reliable suspension of the magnet in a cryostat realized. For compounding of the windings working in vacuum at indirect cryostabilization prepreg is used. There has been applied a new technology of the superconducting magnet protection with the help of sectionalization of the windings, using passive elements of the protection based on cold diodes and resistances, as well as a new technology of active protection with normal zone detectors and heaters.

Magnetic flux flow in layered NbTi/Nb and textured superconducting ceramics Bi2Sr2CaCu2O8+d with the nearly reversible magnetization curve are measured. The characteristic time of the magnetic moment relaxation of such superconductors is determined by the viscous flux flow. It is observed, that in a parallel to superconducting layers external magnetic field the characteristic time of the magnetic flux inflow into the sample and the time of the flux outflow from the sample differ in several times. This difference in the characteristic times is unequivocally due to the flux flow into the sample through the end plates of the thin superconducting layers (plates), where Bean-Livingston barrier is effectively suppressed, but the flux flow out from the superconducting layers (plates) through the wide sides of the plates freely. The experimental proof of the barrier absence for the outflow of the magnetic flux on the border of the superconductor is received. Thus is shown, that the border (surface) of the type-II superconductor is the "semiconductor" for the magnetic flow: it lets the flux to flow out from the superconductor freely, but it interferes with the flux to flow into the superconductor.

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.

New data on the spin-dependent np observables measured with quasi-monochromatic polarized neutron beam in the energy region from 1.2 to 3.7 GeV are presented. Further measurements of np scattering observables using the JINR LHE polarization facility (longitudinal and transverse polarized neutron beams and a polarized proton target) are discussed. The aim of these studies is to determine the imaginary and real parts of the forward scattering amplitudes for np and for isospin I=0 systems above 1.1 GeV.

New results for the np spin-dependent total cross section difference Δσ p ( np ) at neutron beam kinetic energies of 1.59, 1.79 and 2.20 GeV are presented. Measurements of the Δσ p ( np ) energy dependence were carried out at the Synchrophasotron of the Laboratory of High Energies of the Joint Institute for Nuclear Research in Dubna. The values of Δσ L were measured as a difference between the np total cross sections for parallel and antiparallel beam and target polarizations, both oriented along the beam momentum. A fast decrease of Δσ p ( np ) with increasing energy above 1.1 GeV, as it was first seen from our previous data, was confirmed. The new results are also compared with model predictions and with the phase shift analysis fits. The Δσ L quantities for isosinglet state I=0, deduced from the measured values of Δσ p ( np ) and known Δσ p ( pp ) data, are given.