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The results of the first run (December 2020) for the commissioning of the new superconducting synchrotron Booster at the Joint Institute for Nuclear Research are presented. Vacuum conditions and measurements of the lifetime of the single-charged helium ion beam at injection energy of 3.2 MeV per nucleon have been analyzed and the acceleration of ions up to energy of 100 MeV per nucleon has been demonstrated. The measured lifetime of the beam $${{\tau }_{{\exp}}} = (1.32 \pm 0.06)$$ s is compared to the theoretical value $${{\tau }_{{{\text{theor}}}}} = (1.74 \pm 0.50)$$ s calculated with original program code. The results of the first switching-on of the electron cooling system are presented.

The lattice of the NICA collider includes 80 twin-aperture superconducting dipole magnets. Measurements of the magnetic field parameters should be done for both apertures of each collider magnet. For the time being 25% of the magnets are successfully passed the tests. This paper describes the state of serial magnetic measurements and results of test at helium temperature.

The NICA accelerator complex will consist of two injector chains, a new 600 MeV/u superconducting booster synchrotron, the existing superconducting synchrotron—Nuclotron, and the new superconducting collider that has two storage rings each of about 503 m in circumference. The influence of the fringe fields and misalignments of the structure magnets, the field imperfections and natural chromaticity should be corrected by the correction system. The main parameters, arrangements and the field calculations of the corrector magnets are presented.

NICA is an international project accelerator collider complex under construction at the Joint Institute for Nuclear Research in Dubna. The facility is aimed at providing collider experiments with heavy ions up to gold in the center of mass energy from 4 to 11 GeV/u and an average luminosity up to 1 $\times\, 10^{27}$ cm $^\mathbf {-2}$ s $^\mathbf {-1}$ for Au $^{79+}$ . Collision experiments with polarized deuterons and protons 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 503 m in circumference. The planned FAIR synchrotron SIS100 has to deliver high-intensity beams for the FAIR project at GSI, Darmstadt. This machine will use fast-cycling 4 T/s magnets with a magnetic field up to 2 T. The NICA booster synchrotron, the NICA collider, and the heavy ion synchrotron SIS100 are based on iron-dominated window frame-type magnets with a hollow superconductor winding analogous to the Nuclotron magnet. Progress in the manufacturing and testing of the NICA magnets and the SIS100 superconducting magnets is presented.

The magnetic system of the NICA collider includes 80 twin-aperture superconducting dipole magnets. Measurements of the magnetic-field parameters should be done for both apertures of each collider magnet. This paper describes the methods, the first results of magnetic measurements, and developments of a dedicated system for mass-produced dipole magnets of the NICA collider.

The quality of booster closed-orbit correction is estimated. The distribution of the maximum orbit distortion in both directions and the results of numerical simulation using the singular value decomposition method are given. The estimation of closed-orbit distortion with the worst correction quality is given.

NICA is a new accelerator complex under construction at JINR in Dubna. For the NICA booster synchrotron and NICA Collider requires more than 390 superconducting magnets. The magnetic system of the booster of NICA project includes 48 quadrupole superconducting magnets. The paper describes a probe designed for series magnetic measurements of the doublet of quadrupole lenses for the booster, as well as methods of measurement. Presents the first results of cryogenic measurements for the two doublets of quadrupole.

The international project “NICA” (Nuclotron-based Ion Collider fAcility) is an accelerator complex which is under construction at the Joint Institute for Nuclear Research (Dubna, Russia). Basing on the NICA project demands NRC “Kurchatov Institute” (Moscow, Russia) designed and manufactured two trial 12 kA 1G current leads (CLs) intended for powering of the JINR superconducting magnets test bench. The main requirements for the CLs were: a reliable and robust design, usage of liquid nitrogen from the NICA cooling circuits as a resistive section coolant, low resistance joints, current ramp rates up to 10 kA/s and the total heat load to the 5 K end not exceeding 0.4 W/kA per one CL. An in-situ cold test of the trial 12 kA CLs held at JINR in 2015 demonstrated the operational reliability of our technological approaches. Following the successful test results the serial production of 20 pairs of 10.5 kA HTS CLs with very few design updates for the accelerator powering started. The first 10 pairs were fabricated, tested and shipped to JINR as a part of the NICA commissioning framework in June 2017. All the CLs fulfilled the acceptance test requirements. The production of the remaining 10 pairs is to be finished in 2018. The paper gives an overview of the 12 kA and 10.5 kA HTS CLs’ design, discusses their thermal, magnetic and electrical characteristics and presents the acceptance tests results. We also compare our CLs with earlier works by other groups in the context of HTS stack-and-soldering technique, joints’ resistances, relative heat loads into the cryogenic environment etc.

Nuclotron-based ion collider facility (NICA) is an international project-accelerator collider complex under construction at the Joint Institute for Nuclear Research in Dubna. The facility is aimed at providing collider experiments with heavy ions up to gold in the center of mass energy from 4 to 11 GeV/u and an average luminosity up to 1·1027 cm−2·s−1 for Au79+. Collision experiments with polarized deuterons and protons 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 503 m in circumference. The planned FAIR synchrotron SIS100 has to deliver high intensity beams for the FAIR project at GSI, Darmstadt. This machine will use fast-cycling 4 T/s magnets with a magnetic field up to 2 T. The NICA booster synchrotron, the NICA collider, and the heavy ion synchrotron SIS100 are based on iron-dominated “window frame”—type magnets with a hollow superconductor winding analogous to the Nuclotron magnet. The status on the manufacturing and testing of the NICA magnets and the SIS100 superconducting quadrupole and corrector magnets are discussed.

Nuclotron-based Ion Collider fAсility (NICA) is a new accelerator collider complex currently under construction at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The facility includes a new superconducting booster synchrotron whose layout includes 40 dipole and 48 quadrupole superferric magnets. Booster magnets are under serial production, assembling and testing at the new test facility at JINR, Dubna. The designs of NICA magnets are based on the Nuclotron magnet design. The dipole magnets for the NICA booster have a length of 2.14 m, an aperture of 128/165 mm, and a curved yoke with bending radius of 14.1 m. Two quadrupole magnets are connected together to form a doublet. Measurement of the magnetic field parameters are assumed for each booster magnet. 80% of the dipole magnets and 10% of the doublets have successfully passed the tests. We present the cold test results that were obtained from the magnetic measurements of dipole magnets and compare them with the requirements of the specification. Preliminary results of cold magnetic measurements of the first serial doublets are summarized here.

In the 1990s, for Nuclotron, the pioneer accelerator using fast ramped superconducting magnets, a novel cable with superconducting strands wrapped around a cooling tube was developed. Such cable fabrication technology was advanced and adopted for the SIS100 or NICA project. In parallel with major application for fast ramped superferric magnets, application for high field magnets with a cosine-theta type is investigated. In this paper, we give an overview of the history of Nuclotron-type cables, list its advantages, and outline its applicability far beyond the original usage field.

Joint Cryogenic Engineering Conference (CEC) / International Cryogenic Materials Conference, ICMC, Hartford, United States, 21 Jun 2019 - 25 Jun 2019; IOP conference series / Materials science and engineering 755, 012133 (2020). doi:10.1088/1757-899X/755/1/012133, Published by IOP Publ., London [u.a.]

The schematic diagram, design, and technical characteristics of the pulsed current source developed and produced for the magnetic-field measurement system of superconducting magnets for accelerators are described. The current source is based on the current regulator with pass transistor bank in the linear mode. Output current pulses (0–100 A) are produced by utilizing the energy of the preliminarily charged capacitor bank (5–40 V), which is additionally charged between pulses. The output current does not have the mains frequency and harmonics ripple. The relative noise level is less than–100 dB (or 10–5) of RMS value (it is defined as the ratio of output RMS noise current to a maximal output current of 100 A within the operating bandwidth, expressed in dB). The work was performed at the Veksler and Baldin Laboratory of High Energy Physics, Joint Institute for Nuclear Research (JINR).

Serial assembly and tests of dipole and quadrupole magnets of the NICA Booster have started at the Laboratory of High Energy Physics of the Joint Institute for Nuclear Research (JINR). The accelerator is fitted with Nuclotron-type magnets with a superconducting winding and an iron yoke for shaping the needed magnetic field. The design of magnets for NICA was optimized (based on the experience gained in constructing and operating the JINR Nuclotron) for the production of magnetic fields of the required configuration in terms of the beam dynamics in the accelerator and the collider. Measurements of parameters of the field of each magnet are expected to be performed in the process of assembly and testing of each module of the magnet-cryostat system of the NICA Booster and Collider. The results of magnetic measurements for the NICA Booster dipole magnet are presented.

The Facility for Antiproton and Ion Research (FAIR) is currently being constructed at GSI Darmstadt. Around 500 superconducting magnets are being procured for the heavy ion synchrotron SIS100, and around 180 are being procured for the Super Fragment Separator (Super-FRS). All these magnets have to be tested at cryogenic temperature in order to verify and guarantee their performances before they are installed in the tunnel. Test stations, measurement equipment, and the required infrastructure are being built up at the host laboratory and, due to the large number of magnets and testing requirements, at CERN and JINR. We report on the plans, testing strategy, developments, and, particularly, the status of preparations for testing of the SIS100 dipoles at GSI.

Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator collider complex under construction at the Joint Institute for Nuclear Research. The facility is aimed at providing collider experiments with heavy ions up to Gold in the center of mass energy from 4 to 11 GeV/u and an average luminosity up to 1 · 10 27 cm -2 s -1 for Au 79+ . 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 503 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 serial production and test of the magnets for the booster synchrotron and the development of the full-size model magnets for the NICA collider is presented. The test results of magnets are discussed. The status of the construction of the facility for serial tests of superconducting magnets for the NICA project is described.

SIS100, i.e., the core component of the FAIR project, is now heading into the realization phase. While the First of Series SIS100 dipole has already been produced and tested, the main quadrupole magnets are now being designed with the first magnets being built. For these magnets, we report on the first experience of production technology adjustment concentrated on field quality optimization. Along these high-current magnets, the low-current correctors and the special quadrupoles of the injection and extraction modules are made of a Nuclotron cable with insulated strands. This design implies significant different cooling conditions and was first implemented in the chromaticity sextupole. This sextupole was produced last year and was thoroughly tested this year. We report on the status of the various magnets, comment on the optimizations on the first step toward series production, and report on the test results of the first low-current corrector magnet.

Journal of Instrumentation 15(12), T12013 - T12013 (2020). doi:10.1088/1748-0221/15/12/T12013, Published by IOP Publ., London

Particle accelerator complex NICA (Nuclotron-based Ion Collider fAcility) comprises superconducting Booster and Nuclotron synchrotrons which magnets operating at pulse mode in opposite phase with period of about 4 seconds. Summary stored energy of Booster and Nuclotron magnets will vary from 1 to 2.6 MJ during the period. NICA power supply system can be significantly improved by Superconducting Magnetic Energy Storage (SMES) application that will help to move the energy back and force between Booster and Nuclotron. The useful energy at this SMES must be about 1.6 MJ so the maximum total SMES energy should be 3-5 MJ. SMES with this energy should have several Tesla magnetic fields to keep a reasonable size. SMES operating current can be not less than Booster and Nuclotron magnets current so it might be 10-12 kA. It is better to make such a SMES magnet from an HTS (high temperature superconductor) cable for the stability at 6-7 T and 4 s pulse mode. The SMES magnet is planned to be wound as a short solenoid (Brooks coil) of cables optimized for several coaxial sections. HTS cables with helical structure similar to well-known CORC (conductors on round core) cables are under the development at JINR. The HTS cabling technology is based on the same principle as Nuclotron type cable manufacturing technology. HTS tapes, cables and magnets experimental study and testing methods are being developed on the base of an existing test facility at LHEP. First HTS cable short sample with 6 HTS tapes was prepared and tested at 77 K in self-field. Its critical current is about 800 A that will allow achieve required operating currents of SMES magnet with a reasonable amount of HTS tapes in cables. Developments of high field high current fast cycling HTS magnets for accelerators are also being planned at JINR.

Generation of magnetic field in units of booster synchrotron for the NICA project is one of the most important conditions for getting the required parameters and qualitative accelerator operation. Research of linear and nonlinear dynamics of ion beam 197Au31+ in the booster have carried out with MADX program. Analytical estimation of magnetic field errors tolerance and numerical computation of dynamic aperture of booster DFO-magnetic lattice are presented. Closed orbit distortion with random errors of magnetic fields and errors in layout of booster units was evaluated.

Since 1992, the largest Russian cryogenic helium complex of the superconducting accelerator Nuclotron with the cooling capacity of 4000 W at 4.5 K has been operating at the Joint Institute for Nuclear Research in Dubna. The construction of this high-efficient cryogenic system included a large number of technical ideas that had never been applied before in the world. The helium complex of the Nuclotron has become the most advanced and largest Russian liquid helium plant consisting of two KGU–1600/4.5 units, which are capable to operate for a common collector of the liquid helium delivery to the consumer and provide the total capacity of 1000 l/h. In 1992 its use allowed one to begin for the first time the export of liquid helium by means of 40 m3 auto transport containers. The annual level of export deliveries reached 1 million liters. In the near future it is planned to construct a new accelerator complex comprising beside the Nuclotron a superconducting booster and collider to provide collisions of high-intensity beams of heavy ions up to gold Au+79. The cryogenic system of this megaproject includes the latest Russian developments: helium liquefiers with the capacity of 1100 l/h and screw helium compressor aggregates with the outlet pressure of 3 MPa and capacity of 6600 Nm3/h. The assembling and tests of pilot units are being carried out at present. This equipment being commissioned to mass production may lay the foundation for the technology of industrial liquefaction of helium for the development of new deposits in Eastern Siberia.

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.

NICA is a new accelerator collider complex under construction in JINR, Dubna. More than 390 SC-magnets are needed for the NICA booster and collider. One of the parameters measured during the cold testing of superconducting magnets for the NICA project is the dynamic heat releases in the magnet at pulse operation mode. These losses are due to eddy currents, hysteresis losses and other effects. The system for measuring of dynamic heat releases in the SC-magnets by electrical method that is implemented at the facility for testing of superconducting magnets at JINR is described. The results of measured dynamic heat releases in the dipole magnets at series tests are presented.

The main goal of the Nuclotron-M project, approved in 2007, was formulated as follows: modernization of the main accelerator systems for reliable and safe operation of the Nuclotron as a part of the accelerator facility NICA (Nuclotron-based Ion Collider Facility) being constructed at JINR. Demonstration of heavy-ion beam acceleration (with atomic mass number higher than 100) as well as safe and stable operation of the main superconducting system operation at a magnetic field of up to 2 T had been defined as criteria of successful project fulfillment. Another very important issue is performance of stable, long-term beam runs and increase of the accelerated beam intensity. All the main goals of the Nuclotron-M project had been successfully achieved by the end of 2010. In this report we give an overview of the project realization chronology and present the main experimental results obtained at LHEP Nuclotron accelerator facility in the period from 2007 to early 2011.

At the beginning of the 1970s, the stage of development and assimilation of magnetic and accelerator technologies based on superconductivity started in the leading scientific centers in world which were studying the fundamental problems of nuclear physics and the structure of matter. Superconductivity for developing magnets for the proton synchrotron with field amplitude much greater than the limit for ordinary magnets (B ~ 2 T) was harnessed at Fermi Lab (Batavia, USA). The magnetic system of the Tevatron with field amplitude in the working aperture to 4.7 T, placed inside the synchrotron tunnel at energy 500 GeV, made it possible to double the energy of the accelerator. The field in the Tevatron magnets is formed by a multi-turn winding, fabricated on precision equipment. The accuracy of its geometric dimensions determines the quality of the magnetic field in the aperture. Superconducting magnets of this type in their modern form were used in the designs of other accelerators and were termed cos θ magnets. The magnets are cooled successively; the cool-down time of the magnetic system to the working temperature is weeks. A precision cos θ magnet, cryostat with a vessel for liquid helium, heat screen, vacuum jacket, and anchoring of the magnet are integral parts of an extremely labor-intensive, metal-intensive, and expensive cryogenic-magnetic system. Magnets of a new type [3] were developed in the High-Energy Laboratory at the Joint Institute for Nuclear Research (OIYaI) to considerably simplify and reduce the cost of the construction of the superconducting magnet and its cryostating system for the Nuclotron ‐ a specialized synchrotron for relativistic nuclei [1, 2]. Their fundamental difference lay in the use of a magnetic with a window-frame cross-sectional geometry instead of the cos θ precision magnet and a specially developed tubular superconducting cable, intended for pulsed magnets with rapid ramping of the field, instead of the flat superconducting Rutherford cable. In the case of tubular cable, as opposed to Rutherford cable, there is no coil or frame electric insulation in the path of heat flow from the superconductor to the helium; this improves considerably the conditions for cryostating of the superconductor. In addition, the use of two-phase helium as the cryogenic coolant makes the conditions for cooling the superconductor in the tubular cable of the pulsed magnets of the accelerator unique, making it possible to operate with record high field ramping 4 T/sec and higher [4]. On the whole, the concept adopted made it possible to minimize the transverse cross section of the Nuclotron magnet, eliminate the helium vessel inside the cryostat, secure an operating regime with field rise and fall rate 4 T/sec, economize on materials and power supply, simplify the external infrastructure, and most importantly organize the fabrication and testing of the magnets on the basis of the production capacity of OIYaI. OIYaI Nuclotron ‐ SIS100 Prototype. The development of the Nuclotron, a superconducting, strongly focusing accelerator of relativistic heavy nuclei, was motivated by the problems of relativistic nuclear physics and quantum chromodynamics and investigations of the color degrees of freedom in atomic nuclei. To study these problems experimentally, it was necessary to have appropriate beams of accelerated particles, which could not be obtained with the proton synchrotron operating at the time without creating an essentially new accelerator complex. The choice of the maximum energy of the new

A full-size prototype dipole magnet has been designed, fabricated and tested for the Booster synchrotron of a new collider facility NICA at JINR in Dubna. The magnet is based on a cold window frame iron yoke and a curved single-layered superconducting winding made from a hollow NbTi composite superconductor cable cooled with a forced two-phase helium flow at T=4.5 K. The maximal operating magnetic field in the elliptical aperture of 128 mm x 64 mm is 1.8 T. The magnetic field ramp rate of 1.2 T/s should be achievable. The design features of the magnet 2.2 m long as well as the test results are presented.

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.

The MultiPurpose Detector (MPD) is designed to study heavy-ion collisions at the Nuclotron-based heavy Ion Collider fAcility (NICA) at JINR, Dubna. Its main components located inside a superconducting solenoid are a tracking system composed of a silicon microstrip vertex detector followed by a large volume time-projection chamber, a time-of-flight system for particle identification and a barrel electromagnetic calorimeter. A zero degree hadron calorimeter is designed specifically to measure the energy of spectators. In this paper, all parts of the apparatus are described and their tracking and particle identification (PID) parameters are discussed in some detail.

The conceptual design of the magnetic system of the SIS100 synchrotron was described in the Technical Design Report of the FAIR project. The accelerator superconducting magnetic system consists of different types of modules containing the main dipole and quadrupole magnets, different corrector magnets and special units like beam position monitors, particle catchers and others. The first set of full size dipole and quadrupole prototypes was manufactured. Their tests are continued. The final engineering design is carried out by the GSI/JINR collaboration addresses all technical issues of the system units for which adequate solution will be defined. Special designs have to be worked out for the switching-modules needed for beam injection, extraction and transfer. Many special issues are connected with the quadrupole modules. There are 84 such modules of about 4 m long each in the accelerator ring. The essential features of the modules are discussed. General status of the system engineering design is presented.

Superconducting corrector magnets are planned to be installed at the SIS 100 accelerator ring for FAIR. The Nuclotron cable, used for the main dipole and quadrupole magnets, is adopted for the corrector magnets taking into account its advantages as high cooling efficiency and the compatibility to the whole accelerator lattice. The error compensation multipole corrector and the steerer are built as nested magnets to save longitudinal space in the ring, the chromaticity sextupole is a superferric magnet. We present the progress of design studies on these magnets.

A design study of the multipole corrector magnet for the SIS 100 is in progress. This magnet, which has to integrate functions of a quadrupole, a sextupole and an octupole magnet, contains nested three windings to save longitudinal space in the accelerator ring. Although the windings are made from a Nuclotron type cable as for the SIS 100 main dipole magnet, insulated superconducting wires which are connected in series to allow low current operation, are used for the cable. In this paper, we describe the design principle and mechanical structure of the magnet and present computation results.

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 magnet's 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.

The study of superferric synchrotron magnets with a pulse repetition rate up to 20 Hz is performed at the Laboratory of High Energies of the JINR during the last years. The magnet feature is a low inductance superconducting coil made of a high current hollow cable, cooled with two-phase helium flow at 4.5 K. After the successful tests of fast-cycling 1.4 m model dipoles at the field ramp up to 7 T/s, a proper quadrupole is under design and construction. The new magnet yoke length is about 420 mm and the distance between the pole shoes is 90 mm. The cable comprises 24 wires of 0.73 mm diameter are wound around a copper-nickel tube with an outer diameter of 5 mm. The wire consists of 10374 NbTi filaments of 4.2 mum diameter. It is expected that the new 32 T/m quadrupole magnet will operate at pulse repetition rate up to 10 Hz providing the field gradient ramp of 600 T/m per second. The first tests have been carried out in August 2006. Status of the work and obtained results are presented and discussed.

The synchrotron SIS100 is one of the two basic accelerators of the future Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt. The SIS100 should provide acceleration of high intensity U28+ and proton beams for 0.5 s, with a pulse repetition rate of 0.6 Hz. In the accelerator magnetic system superferric 2 T dipoles of about 3 m length and 32 T/m quadrupoles of about 1 m length will be used. The magnet coils are made from hollow NbTi composite cable cooled with two phase helium flow at 4.5 K. The lattice comprises 108 dipoles and 168 quadrupoles. The elliptic beam pipe inner dimensions have been fixed at 130 times 60 mm2 for the dipole and 135 times 65 mm2 for the quadrupole. Both the dipole and quadrupole design approaches are based on improved versions of the original Nuclotron fast-cycling magnets and provide significantly less AC loss at 4.5 K, better quality of the magnetic field, and a higher long-term mechanical stability of the magnet coils. The results are based on the investigation of 1.4 m dipole and 0.4 m quadrupole Nuclotron-type magnet models. The status of the new magnets design and its manufacturing are presented. Essential features and new results are discussed.

The SIS 100 magnets of the Nuclotron-type are fast- pulsed superferric cold iron magnets. The dipole coil is a double layer saddle-shaped coil with 16 turns. The cable is a hollow tube NbTi composite cable of about 7.2 mm outer diameter, cooled with two phase helium flow at 4.5 K. A 2D structural analysis of the dipole cross section has been performed to determine the stress levels in the components of the coil package and to suggest an appropriate support structure for the conductor. Different design proposals with the focus on limiting stress in the CuNi cooling tubes and on feasibility of industrial manufacturing procedures have been conceived and analysed. The chosen coil support structure (substrate or "comb"), together with new insulation and modification of the winding scheme, seems to be an appropriate way to stabilize the coil better and offers important advantages like precise positioning of the conductor, more uniform distribution of loads on the CuNi tubes, an easier winding process on a guiding support, and simplified production procedures. Samples of the new coil structure were produced and tested. The obtained results are presented and discussed.

New results from the investigation of 2 T superferric model dipoles operating at 4 T/s, 1 Hz are presented. The works are performed within the R&D program on the design of the SIS100 synchrotron at GSI in Darmstadt. One of the main research goals is minimization of overall AC power losses in the magnet at 4 K level. Different modifications of the dipole were proposed and tested experimentally. By the present time, the losses are reduced to about 17 W/m of the magnet length, while the reference Nuclotron dipole produces about 38 W/m in the same operating mode. Essential design details of the model magnets are described and further R&D steps are outlined

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

The progress in the design of a fast-ramped, fast-cycling Cos-style 4 T dipole based on high current hollow superconducting cable is presented. New results obtained in the optimization of both the 40 kA hollow cable and the magnet coil structures are discussed. Experimental data from recent tests of the model dipole coil made from the NbTi keystoned wire are reported. The joint optimization of the angular distribution of the coil turns and the internal shape of iron boundary makes it possible to achieve a relative non-linearity of the magnetic field better than 5 • 10−4 within 82% of the coil aperture over a dynamic range from 0.3 T to 4.5 T. The diameter of the new hollow cable is 8.92 mm. It consists of 40 keystoned NbTi composite wires and a 3mm bore coolant tube. The designed operating current is 40.1 kA at 4.5 T. Full scale tests of the model dipole coil will be performed after completion of the necessary test facility upgrade. The actual maximum of 11.4 kA for the operation current is limited by the power supply and current leads of the test stand. The new current leads aimed at a current of 20 kA have been designed and manufactured.

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.

A new option of a superconducting dipole magnet for a fast cycling ( f =1 Hz) synchrotron is presented. The magnet is based on cos θ -type geometry, but its cold mass ( T =4.5 K) consisting of SC-coil and a reinforcing shell is separated from the iron yoke ( T =50–80 K) by a small vacuum gap. The arc-type one layer SC-coil is made of a hollow NbTi composite cable.

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.