Cryogenics for the future accelerator complex NICA at JINR

The NICA cryogenics will be based on the modernized liquid helium plant that was b uilt in the early 90’s for the superconducting synchrotron known as the Nuclotron. The main goals of the modernization are: increasing of the total refrigerator capacity from 4000 W to 8000 W at 4.5 K, making a new distribution system of liquid helium, and ensuring the shortest possible cool down time. These goals will be achieved by means of an additional 1000 l/hour helium liquefier and “satellite” refrigerators located near the accelerator rings. This report describes the design choices of the NICA, demonstrates helium flow diagrams with major new components and briefly informs of the liquid nitrogen system that will be used for shield cooling at 77 K and at the first stage of cooling down of three accelerator rings with the total length of about 1 km and “cold” mass of 290 tons.     

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.     

Measurement of the magnetic-field parameters of the NICA Booster dipole magnet

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.     

Full-scale prototype of the circular track detector for the multipurpose detector facility at the NICA acceleration complex

The development of the NICA heavy ion collider, which is now under way, assumes the development of a Multipurpose Detector (MPD), including an end-cap tracker (EC) (which can be a wheel-type tracker based on thin-wall drift tubes (straws) similar to the inner detector of the transition radiation tracker (TRT) in the ATLAS experiment). The identical front and back tracker modules mounted behind the TPC are to ensure the detection of Au-Au ion collision products in the pseudorapidity range from 1.4 to 2.1 with good track parameters of reconstructed events. Each module will contain 60 circular straw planes and maximum straw occupancy will be no higher than 0.2 particle per collision. The NICA EC is substantially different from its analogue and requires a certain amount of R&D. The first results from applying new technology to make a full-scale prototype of the circular EC detector for NICA are presented.     

Beam-cooling methods in the NICA project

The Nuclotron-based Ion Collider Facility (NICA) is a new accelerator complex under construction at the Joint Institute for Nuclear Research (JINR) for experiments with colliding beams of heavy ions up to gold at energies as high as 4.5 × 4.5 GeV/u aimed at studying hot and dense strongly interacting nuclear matter and searching for possible indications of the mixed phase state and critical points of phase transitions. This facility comprises an ion source of the electron-string type, a 3-MeV/u linear accelerator, a 600-MeV/u superconducting booster synchrotron (Booster), a Nuclotron (upgraded superconducting synchrotron with a maximum energy of 4.5 GeV/u for ions with the charge-to-mass ratio Z/A = 1/3), and a collider consisting of two vertically separated superconducting rings with an average luminosity of 10²⁷ cm^?2 s^?1 in an energy range over 3.0 GeV/u. Beam cooling is supposed to be used in two NICA elements, the Booster, and the collider rings. The Booster is intended for the storage of ¹⁹⁷Au³¹⁺ ions to an intensity of about 4 × 10⁹ particles; their acceleration to the energy 600 MeV/u, which is sufficient for the complete stripping of nuclei (an increase in the injection energy and the charge state of ions makes the requirements for vacuum conditions in the Nuclotron less stringent); and the formation of the necessary beam emittance using the electron cooling system. Two independent beam-cooling systems, a stochastic one and an electron one, are supposed to be used in the collider. The parameters of the cooling systems, the optimum mode of operation for the collider, and the arrangement and design of the elements of the systems are discussed.     

Status of the High-Voltage Electron-Cooling System of the NICA Collider

Physics of Particles and Nuclei Letters - In order to achieve the design luminosity in the NICA collider, it is planned to equip it with both stochastic and electron cooling. The electron-cooling...     

Low-Inductance High-Voltage Input of Pulsed Power to the Cryogenic Module of the Septum Magnet for the NICA Collider

Physics of Particles and Nuclei Letters - A design for a device for pulsed-power input to the cryogenic module of a septum magnet of the NICA collider is presented. This design allows the input...     

Design of the 2.5 MV Electron Cooling System and the Potential for Increasing NICA Collider Luminosity

The design and capabilities of the electron cooling system for the NICA collider are discussed. This system should suppress the intrabeam scattering and beam–beam interactions.     

Estimating the main radiation source terms for the NICA collider

The various radiation sources at the NICA collider were identified and specified. It is found that the most powerful ones are the beam catchers restricting the beam ??halo??. The double differential neutron yields from the catcher are calculated using the GEANT4 code. A simulation of the total absorbed dose in the magnet superconducting winding due to the catcher radiation is carried out for the accepted levels of beam losses. The induced radioactivity of the catcher is predicted for the collider schedule.     

Modeling of the internal tracking system of the NICA/MPD detector

The internal tracking system of the NICA/MPD detector is aimed at efficiently detecting the short-lived products of nucleus–nucleus collisions. We consider various geometries of the internal tracking system based on microstrip silicon sensors and simulate its identification power in reconstructing the Λ⁰ hyperons formed in central Au + Au collisions at \(\sqrt {{S_{NN}}} \; = 9\;GeV\).     

Electromagnetic Modeling of NICA Collider Structure Elements

Physics of Particles and Nuclei Letters - The coupling impedances of individual elements of the NICA collider are simulated in order to determine, at an early stage of design, the possible...     

Feasibility study of heavy ion physics program at NICA

There are strong experimental and theoretical evidences that in collisions of heavy ions at relativistic energies nuclear matter undergoes a phase transition to the deconfined state—Quark Gluon Plasma. The caused energy region of such transition was not found at high energy at SPS and RHIC and search for this energy is shifted to lower energies, which will be covered by the future NICA (Dubna), FAIR (Darmstadt) facilities and BES II at RHIC. Fixed target and collider experiments at the NICA facility will work at the energy range from a few AGeV up to \(\sqrt {\;{S_{NN}}} \; = \;11\;GeV\) GeV and will study the most interesting area on the nuclear matter phase diagram. The most remarkable results were observed in the study of collective phenomena occurring in the early stage of nuclear collisions. Investigation of the collective flow will provide information on Equation of State (EoS) for nuclear matter. Study of the Event-by-Event fluctuations and correlations can give us signals of critical behavior of the system. Femtoscopy analysis provides the space-time history of the collisions. Also, it was found that baryon stopping power revealing itself as a “wiggle” in excitation function of curvature of the (net)proton rapidity spectrum relates to the order of the phase transition. The available observations of an enhancement of dilepton rates at low invariant masses may serve as a signal of the chiral symmetry restoration in hot and dense matter. Due to this fact, measurements of the dilepton spectra are considered to be an important part of the NICA physics program. The study of strange particles and hypernuclei production gives additional information on the EoS and “strange” axis of the QCD phase diagram. In this paper a feasibility of the considered investigations is shown by the detailed Monte Carlo simulations applied to the planned experiments (BM@N, MPD) at NICA.     

Study of the Electron Cooling System of the NICA Booster

The electron cooling system for the NICA booster has been under construction and tested over the last few years at the Institute of Nuclear Physics. The design of this setup and the results of tests are detailed.     

Influence of Fringle Fields in Quadrupole Lenses on the Dynamics of Particles in the NICA Collider

A study of the NICA collider dynamical aperture (DA) using the MADX code has shown that, in the chosen working point (Q_x,Q_y ～ 9,43), the DA sharply decreases when taking into account the fringe fields of the quadrupole lenses and dipole magnets. An analytical theory is developed to calculating the strength of resonances generated by the fringe fields of the quadrupole lenses in a circular machine. It is shown that the formulae derived for these parameters have a general character and do not depend on the lens design. The codes for a numerical calculation of the anharmonicity coefficients and resonance strength in the NICA collider are written. The method is developed to estimate the resonance strength by using the numerical simulation of the trajectories with the help of the MADX code. For the NICA collider structure, the results of the analytical calculation of the resonance strength for a chosen resonance coincide with the results obtained using the MADX code with a satisfactory accuracy.     

Optical Structure and Dynamic Aperture of the NICA Сollider

The optimized optical structure of the NICA collider is considered. Studies and calculation methods of the stability region of the motion of charged particles in the collider—the dynamic aperture—are presented. The influence of the magnetic-field nonlinearities, in particular, the fringe fields of the magnetic elements on the dynamic aperture, is considered. The dependences of the dynamic aperture on optical properties of the collider, the choice of the working point of betatron frequencies, and tuning parameters of the beam-interaction region are shown. The methods for compensating the effect of the fringe fields on the stability of beam dynamics are discussed.     

Longitudinal dynamics of <Superscript>197</Superscript>Au<Superscript>32+</Superscript> and <Superscript>197</Superscript>Au<Superscript>79+</Superscript> ions in NICA injection chain

The main objective of the NICA project developed at the Joint Institute for Nuclear Research (JINR) is to conduct experimental studies with colliding heavy ion beams in an energy range of 1–4.5 GeV/nucleonucleon with luminosity on the level of 1 × 10²⁷ cm⁻² s⁻¹. In this paper the operation regime of the collider injection chain providing the bunch with experimentally desirable parameters at the output of the Nuclotron is considered for gold ions as an example.     

Beam transportation lines for the NICA project

A heavy-ion collider, i.e., the Nuclotron-based Ion Collider Facility (NICA), is being developed at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The aim of this project is to construct a new accelerator complex for conducting experiments with colliding ion beam (at the first stage of the project) and with polarized proton and deuteron beams (at the second stage). The NICA accelerator complex will consist of two linear accelerators, two synchrotrons, two collider rings, and beam transportation lines. The magnetic lattice and diagnostic and correction systems for the NICA beam transportation lines are described in this report.     

Electron-cloudless operation mode of the Nica collider

The effect of electron clouds in NICA collider was analyzed first in 2008 at development of NICA CDR [1]. The simulation results were revised and renewed numbers are presented in this section. Both simulations were performed with ECLOUD code, version 3.3 [2].     

Status of NICA complex at JINR

New scientific program is proposed at Joint Institute for Nuclear Research (JINR) in Dubna aimed a study of hot and dense baryonic matter in the wide energy region from 2 GeV/amu to √s _NN = 11 GeV, and investigation of nucleon spin structure with polarized protons and deuterons maximum energy in the c.m. 27 GeV (for protons). To realize this program the development of JINR accelerator facility in high energy physics has started. This facility is based on the existing superconducting synchrotron—Nuclotron. The program foresees both experiments at the beams extracted from the Nuclotron, and construction of ion collider—the Nuclotron-based Ion Collider fAcility (NICA).     

Mössbauer optics of synchrotron radiation at an isotopic boundary

The inelastic coherent Mössbauer scattering (ICMS) of synchrotron radiation at an isotopic boundary—a flat interface between two regions of matter which have different concentrations of the Mö ssbauer isotope—is investigated theoretically. Attention is focused primarily on the ICMS component for which the absorption of a synchrotron radiation photon by a nucleus occurs with recoil, i.e., with the creation or annihilation of lattice phonons, and the subsequent process of reemission of a photon by the Mössbauer nucleus occurs without recoil, as a result of which radiation is pumped from the wide synchrotron radiation line into the narrow Mö ssbauer line. Formulas similar to the Fresnel formulas, well known in optics, for the transmission and reflection of light at a dielectric boundary are obtained for ICMS at an isotopic boundary. Specifically, it is shown that the angle of reflection for ICMS at an isotopic boundary is different from the angle of mirror reflection of a synchrotron radiation beam, and the direction of the ICMS transmitted through the isotopic boundary depends on the deviation of its frequency from the exact value of the Mössbauer resonance frequency and in general is different from the direction of propagation of the synchrotron radiation beam. The suppression of ICMS at grazing angles of incidence of the synchrotron radiation beam is analyzed. A similar problem is solved for a plate-shaped sample containing a Mössbauer isotope. It is shown that the specific nature of the ICMS at an isotopic boundary could be helpful in the problem of Mö ssbauer filtering of synchrotron radiation.