Andrey Butenko

Upgrade of Nuclotron power supply system

One of the trends of Nuclotron development lies in modifying the power supply system and upgrading the energy evacuation system of structural magnets in order to provide reliable durable operation of the synchrotron at a dipole magnet field level of 2 T. This is necessary for Nuclotron operation as part of the injection chain of the heavy-ion NICA collider under design at JINR and for the current program of physical studies. The principles of construction and specific features of the existing system based on a separate power supply of structural dipole and quadrupole magnetic elements are considered. The main provisions of the upgrade of the power supply system, structural and schematic diagrams, control schemes, and energy evacuation switch schemes from superconducting elements are presented.

Progress in the Design of a Fast-Cycling Cos - style Dipole based on High Current Hollow Superconducting Cable *)

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.

Research and design of a new RFQ injector for modernization of the LU-20 drift-tube linac

A new NICA heavy-ion collider is now under construction at JINR. At the same time, the Nuclotron facility is being modernized. A joint team from the JINR, MEPhI, and ITEP are now reconstructing a proton and light-ion injection system. New results of the RFQ linac resonator testing and measurements and RF power load are discussed in this article.

Results of the Nuclotron-M project

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.

Progress in development of Nuclotron accelerator complex

The Nuclotron superconducting synchrotron was constructed in 1987–1992 [1]; it is the world’s first synchrotron based on fast cycling “window frame” electromagnets with a superconducting coil. For a design field of dipole magnets of 2 T, the magnetic rigidity is 45 T m, which corresponds to the energy of heavy nuclei (for example, gold) of 4.5 GeV/nucleon. The Nuclotron accelerator complex is currently being upgraded (the Nuclotron-M project); this upgrade is considered a key part of the first stage of fulfilling the new Joint Institute for Nuclear Research (JINR) project: the Nuclotron-based Ion Collider fAcility and Multi-Purpose Detector (NICA/MPD). The most important task of this new project is the preparation of basic Nuclotron systems for its reliable operation as part of the NICA accelerator complex. Basic results of activity on the project, which started in 2007, are presented and the results of the last Nuclotron runs are analyzed.

Calculation of magnetic field for 4 T fast cycling superconducting dipole magnet

The problem of optimization of the two-dimensional magnetic field distribution of a dipole magnet with a field of 4 T and aperture diameter of 100–110 mm for a fast cycling synchrotron is considered. A singlelayer winding with a small number of turns is made from a hollow NbTi superconducting cable with an operating current up to 30 kA. The mathematical method providing optimization of the higher harmonics amplitude of the magnetic field by varying the position of current windings is described. The results of calculation of two-dimensional magnetic fields of the superconducting magnet are given.

Spin Transparency Mode in the NICA Collider with Solenoid Siberian Snakes for Proton and Deuteron Beam

Two solenoid Siberian Snakes are required to obtain ion polarization in spin transparency mode of the NICA collider. The snake solenoids with a total field integral of 2×50 Tm are placed into the straight sections of the NICA collider. It allows one to control polarization of protons and deuterons up to 13.5 GeV/c and 4 GeV/c respectively. The snakes introduce a strong betatron oscillation coupling. The calculations of orbital parameters of proton and deuteron beams in the NICA collider with solenoid Snakes are presented.

First results on the measurements of the proton beam polarization at internal target at Nuclotron1

The spin program at NICA using SPD and MPD requires high intensity polarized proton beam with high value of the beam polarization. First results on the measurements of the proton beam polarization performed at internal target at Nuclotron are reported. The polarization of the proton beam provided by new source of polarized ions has been measured at 500 MeV using quasielastic proton-proton scattering and DSS setup at internal target. The obtained value of the vertical polarization of ~35 % is consistent with the calculations taking into account the current magnetic optics of the Nuclotron injection line.

NICA Collider Lattice Optimization

The Nuclotron-based Ion Collider fAcility (NICA) [1] is a new accelerator complex being constructed at JINR. It is aimed to collider experiments with ions and protons and has to provide the ion-ion (Au +79 ) and ion-proton collision in the energy range of 14.5 GeV/u and also polarized proton-proton (512.6 GeV) and deuterondeuteron (25.8 GeV/u) collisions. Two collider rings are designed and optimized to achieve the required luminosity at two interaction points (IP). Taking into account space charge effects of the intense ion beam the application of electron beam or stochastic cooling methods were proposed to provide beam or luminosity lifetime. This paper is considering one of the most challenging problems of accelerator physics that is finding the dynamic aperture (DA) of the collider ring.

Achievement of Necessary Vacuum Conditions in the NICA Accelerator Complex

NICA is the 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 a center of mass energy range from 4 to 11 GeV/u and an average luminosity up to 10 27 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 superconducting synchrotron Nuclotron, and a new superconducting collider consisting of two rings, each of about 500 m in circumference [1]. Vacuum volumes of the accelerator booster and Nuclotron and the superconducting collider are divided into volumes of superconducting elements thermal enclosure and beam chambers. The beam chambers consist regular cold periods, which are at a temperature of 4.2K to 80K, and warm irregular gaps at room temperature. Operating pressure in thermal enclosure vacuum volumes have to maintained in the range of 1×10 to 1×10 mbar, in the beam chamber cold and warm areas – not more than 2×10 mbar. The description of way to achievement and maintenance of the working vacuum in the NICA project