A number of open questions remain in the manipulation of the spins of colliding beams, which is a key aspect in the operation of polarized beam colliders such as the Nuclotron-based ion collider facility (JINR, Dubna, Russia) and the electron ion collider (BNL, United States). The spin transparency regime, which is the only realistic regime to control the deuteron polarization, has not yet been approved experimentally. With the existing configuration of the JINR accelerator complex, a pilot spin transparency experiment could be performed on a proton beam in the Nuclotron synchrotron. The dynamics of the proton beam polarization during the fast crossing of spin resonance guided by spin navigators based on regular orbit-steerer dipoles has been analyzed in this work. A scheme has been designed to compensate the coherent action of Nuclotron lattice imperfections on spin. In this scheme, the spin field induced by lattice imperfections is determined from the adiabatic deviation of spins in the resonance region, taking into account the synchrotron energy modulation. Integer-resonance strengths can be compensated down to the limits conditioned by orbital beam emittances. The numerical simulation of the proposed spin compensator has confirmed that the spin transparency regime in an imperfect Nuclotron lattice with a strongly distorted closed orbit can be experimentally verified.

In Nuclotron, there are no intrinsic spin resonances for protons up to 3.5 GeV/c, and in this momentum range beam depolarization is associated with the crossing of integer spin resonances. Correction dipoles are used to deliberately increase the resonance strength due to controlled deflection of the closed synchrotron orbit. When the closed orbit is deflected up to 10 mm and the field ramp rate in arch dipoles is 0.6 T/s, almost all integer resonances will cross adiabatically without loss of polarization, with the exception of the first two resonances at energies of 108 and 631 MeV. Adiabatic crossing of these resonances can be provided by introducing a weak longitudinal field with an integral of 50 mT m. Conserving polarization by the proposed method will allow the injection of protons into the NICA collider up to 3.5 GeV/c, as well as experiments on external targets.

A possible magneto-optical structure of the Nuclotron is considered, which could provide the conditions for an experiment to measure the electric dipole moment of the deuteron. To this end, it was necessary to solve four problems for eight superperiodic structures: implement the concept of “quasi-frozen spin” in the proposed optics, increase the lengths of the straight sections between arcs, ensure zero dispersion in the straight sections, and, as far as it is possible, preserve the length of the accelerator ring, taking into account accommodation of the required equipment. In addition, the transition to a magneto-optical structure with superperiodicity N = 16 is considered, which will bring the properties of the “quasi-frozen” structure closer to those of the “frozen” structure by reducing the beam rotation angle on each arc. At such angles for deuterons, the feasibility of searching for the electric dipole moment of the proton is also considered.

The NICA accelerator complex intended for studying baryonic matter and research in spin physics is currently at the stage of construction and mounting at the JINR. The NICA injection complex was designed to produce heavy ions with an energy of 1–3.9 GeV/u. The injection complex consists of two new accelerators: Heavy Ion Linear Accelerator, HILAC, and the superconducting synchrotron, Booster, and the modernized superconducting synchrotron, Nuclotron. The injection facility provides heavy ion beams for the NICA collider and the fix target experiments. The results of the fourth Booster-Nuclotron beam run for fix target experiments on the BM@N setup are discussed. The completion of the facility equipment construction and mounting are also presented along with the plans of first collider runs.

This study is motivated by the search for the electric dipole moment (EDM) of elementary particles. The most promising idea in that regard is the “Frozen Spin” concept first proposed by the BNL. This concept, however, requires the building of a brand-new facility devoted to the EDM-search. NICA is not such a facility, hence the need for a modification compatible with the existing optics; one that wouldn’t disrupt the ring’s capability for parallel experiments. Such a modification is the “Quasi-Frozen Spin” idea, realized by adding transport channels, bypassing the ring’s straight sections. Wien-filters are placed in these channels in order to compensate spin-rotations caused by the ring’s arc dipoles, thus making its net spin-transfer matrix unitary. Even though, during its movement along the beam line, the beam’s polarization vector deviates from alignment with the momentum vector, this motion is regular and fits within one beam revolution, allowing for the buildup of the EDM-signal. The present study shows that the “Quasi-Frozen Spin”-specific optics is consistent with the existing NICA lattice and that the modified structure is capable of maintaining a requisite spin-coherence time.

The original program of the NICA (Nuclotron based Ion Collider fAcility) accelerator complex is focused on a heavy ion and polarized deuteron and proton collider physics and did not include precision searches for the electric dipole moments (EDM) and the galactic axion condensate. It is of importance to note the approaches to the search for the EDM of deuterons usually discussed by CPEDM and srEDM collaborations only envision the development of a dedicated ring corresponding to the “frozen spin” mode with spin pointing all the time along the momentum due to using special deflectors with crossed electric and magnetic fields. Taking advantage of the smallness of the magnetic anomaly of deuterons, we propose to use in the NICA collider the “quasi-frozen spin” mode, when the precession of spin away from momentum in arcs is compensated by Wien filters in straight sections. The simplest technical solution at the NICA collider currently under construction is to create bypasses at the collider equipped with Wien filters, which make it possible to explore the deuteron EDM without affecting any infrastructure of the MPD and SPD detectors. Concurrently, modulation of the spin precession by Wien filters in bypasses will make NICA a broadband axion antenna. The new role of the bypass as an axion antenna, in addition to searching for the EDM of protons and deuterons, will significantly enhance the potential of the NICA complex as a unique platform for precision tests of basic symmetries in elementary particle physics

A new method for deuteron spin-flip is proposed, which uses the spin resonance crossing with betatron frequencies. The resonance is induced by quadrupole correctors of the Nuclotron, which make it possible to control simultaneously the detuning from the resonance and its power. The deuteron spin-flip is due to adiabatic resonance crossing by the slow variation of the betatron frequency. An advantage of this method is that the beam energy remains constant at the induced resonance crossing; it is determined by the chosen frequency of vertical betatron oscillations. The possibility of experimental verification of the deuteron spin-flip in the Nuclotron is discussed.

The NICA accelerator complex includes beam transfer lines and stations for applied research. The first commissioning of the Station of Chip Irradiation (SOCHI) was performed at the end of 2021with С4+ heavy ions extracted from the linear accelerator (HILAC) at an energy of 3.2 MeV/n. The new SOCHI beam transfer line is integrated in the existing HILAC-Booster beamline. The Irradiation Setup for Components of Radioelectronic Apparatus (ISCRA) with ion energy ranging from 150 to 500 MeV/n and the Setup for Investigation of Medical Biological Objects (SIMBO) with the ion energy ranging from 400 to1100 MeV/n are based on the beams extracted from Nuclotron. The equipment of ISCRA and SIMBO stations has been manufactured and is planned to mount in the end of 2022. The beamlines are being designed now. The technical parameters of the beamlines and stations and the results of the first run of the SOCHI station are presented in this study.

A possible magneto-optical structure of the Nuclotron creating the conditions for conducting an experiment to measure the electric dipole moment of the deuteron is considered. The main problems that need to be solved when reconstructing the Nuclotron for the stated task and methods for solving them are presented.

This article has been withdrawn by IOP Publishing following the request by the authors to augment their affiliation by an institution. Upon reviewing the matter, IOP Publishing found that the institution (Moscow Institute of Physics and Technology) is subject to sanctions by the UK government. To ensure compliance with sanctions regulations, this article has been withdrawn from IOPscience.

This paper describes experiments with the main parameters of the RF accelerating systems of the Booster and the Nuclotron of the Nuclotron based Ion Collider fAcility (NICA) complex, which affect the capture and acceleration, as well as the additional hardware solutions used in this case. The operating modes of accelerating stations of the Booster and the Nuclotron are considered. In particular, the paper describes the principle of formation of the law of the change in the amplitude of the accelerating voltage during the adiabatic capture of particles both in the Booster and in the Nuclotron, as well as the features of setting the sequence of synchronization pulses.

We propose a system to produce multiple spin reversals of a polarized proton beam based on orbit-steerer dipoles already installed in the Nuclotron, a superconducting synchrotron at the Joint Institute for Nuclear Research, when the latter operates in the spin-transparency regime. The beam momentum of 3.54 GeV/ c corresponds to the integer spin resonance γ G = 7 . We report the results of numerical simulation of the proton spin dynamics pertinent to the acceleration up to γ G = 7 , including the adiabatic capture of spins by navigators and the subsequent multiple spin flips. A feasibility of the pilot experiment to verify our approach with the current magnetic lattice of the Nuclotron is discussed. To preserve the beam polarization during the crossing of integer resonances we propose to employ intentional resonance-strength enhancements effected by controlled variations of the beam orbit during acceleration.

In November +/- December 2020 and in September 2021, the first two beam runs of the Booster Synchrotron - a new cyclic accelerator of the NICA (Nuclotron-based Ion Collider fAcility) complex - were performed at the Laboratory for High Energy Physics, Joint Institute for Nuclear Research. New technologies (previously not used in Russia) were developed for the Booster's construction based on new physical and technological solutions. We describe these technologies and solutions and also the methods used in constructing and testing the accelerator systems. We present the results of the first two runs.

A spin navigator based on correcting dipoles has been proposed to manipulate the directions of protons spins in experiments at the Nuclotron synchrotron (JINR, Dubna). The polarization is controlled by means of the controllable distortion of the beam closed orbit by correcting dipoles, which ensures the significant enhancement of the action of the navigator on the spins of particles. A method has been proposed to measure the coherent effect of the lattice imperfection on the spin dynamics by the navigator. An idea of a spin compensator based on correcting dipoles is presented, which allows one to eliminate the effect of the lattice imperfection on the polarization. The proposed navigator and spin compensator make it possible to perform a series of experiments at the Nuclotron to verify a new polarization control technique called the spin transparency mode. The results are relevant for experiments with polarized beams in the spin transparency regime at the NICA (Dubna, Russia) and EIC (Brookhaven, United States) and the COSY synchrotron (Julich, Germany).

The most important condition for starting work at the NICA accelerator complex, which is a powerful source of ionizing radiation, is to obtain a sanitary-epidemiological conclusion with the justification of a sanitary-protection zone around the facility. The size and configuration of the sanitary-protective zone around the NICA complex are determined by the mode of operation and the loss of particles in its various elements. Based on the calculations of the radiation situation performed earlier, the boundaries of the sanitary-protective zones have been defined for the heavy ions collision mode of the collider operation and for the additional mode in which high-energy protons interact in the collider.

Two schemes of the polarized proton beam formation are considered for the NICA accelerator complex. In the first scheme, the polarized proton beams are injected from the LILAC linear accelerator into the Nuclotron, where they are accelerated up to a kinetic energy of 1.5–2 GeV and then extracted to the Collider. The injected proton beams are accumulated in the Collider using the RF barriers and electron cooling. After accumulation, the protons are accelerated by the RF1 induction voltage up to the critical relativistic factor γtr = 7.089, where a jump of the betatron frequency occurs. After transition through the critical energy, the protons are accelerated up to the energy of the experiment. For this scheme, a specialized optical lattice is considered. The critical proton energy (γtr = 18.6) for this lattice is larger than the maximal energy of the experiment (12.6 GeV). The so-called spin transparency mode is planned to be used for formation of polarized beams in the Collider. In the second scheme, the polarized proton beams are injected into the Booster from LILAC. The protons are cooled in the Booster, accelerated, and extracted to the Nuclotron. During their acceleration in the Nuclotron, the protons cross the integer spin and spin-betatron resonances. After accelerating protons to the kinetic energy of the experiments of 6–10.86 GeV, the vertically polarized proton beams are transferred to the Collider. At the integer spin resonances following each other with the energy interval of 0.523 GeV, the partial Siberian snake permits the longitudinal polarization to be formed for beams used in the SPD and MPD detectors.

Injector of NICA accelerating facility based on the Heavy Ion Linear Accelerator (HILAC) is aimed to inject the heavy ions having atomic number A≈200 and ratio A/Z ≤ 6.25 produced by ESIS ion source accelerated up to the 3.2 MeV for the injection into superconducting synchrotron (SC) Booster. The project output energy of HILAC was verified on commissioning in 2018 using the beams of carbon ions produced with the Laser Ion Source and having ratio A/Z=6 that is close to the project one. Beams of He1+ ions were injected into Booster in its first run and accelerated in 2020. In 2021 ions of Fe14+ produced with the LIS were injected and accelerated up to 200 MeV/u. Beam formation of Fe ions and perspectives of using LIS for the production the ions with high atomic mass A and ratio A/Z matching to HILAC input parameters are described. HEAVY ION LINEAR INJECTOR Heavy ion injector of the NICA project is based on the heavy ion linear accelerator (HILAC) and aimed to be injector of gold ions into SC Booster synchrotron of the NICA facility. The main features of it are presented in the Table 1. Table 1: Main Features of HILAC

Heavy Ion Linear Accelerator (HILAC) is designed to accelerate the heavy ions with ratio A/Z ≤ 6.25 produced by ESIS ion source up to the 3.2 MeV for the injection into superconducting synchrotron (SC) Booster. HILAC was commissioned in 2018 using the carbon beams from Laser Ion Source (LIS). The project output energy was verified. Transmission could be estimated only for DTL structure because of the presence at the RFQ input the mixture of ions with different charge states extracted from laser plasma. To estimate transmission through the whole linac the ion source producing the only species He+ was designed. The beams of He+ ions were used for the first run of SC Booster. Design of the helium ion source and results of the He+ beam acceleration and injection are described. HEAVY ION LINEAR INJECTOR Heavy ion linear accelerator (HILAC) is proposed to be injectors for SC Booster synchrotron of the NICA facility. The main features of it are presented in the Table 1. Table 1: Main Features of HILAC HILAC Species of ions Au31+ Z/A ≥ 0.16 Input energy 17 keV/u Output energy 3.2 MeV/u Beam current, mA 10 Operating frequency, MHz 100.625 Beam transmission rate, % 98 The accelerator is based on 4-rod RFQ [1] and IH DTL cavities with the KONUS accelerating structure inside [2]. The Heavy Ion Linear accelerator (HILAC) is to inject the gold ions into the superconducting synchrotron Booster and designed to accelerate particles with a ratio A/Z ≤ 0.16 up to energy 3.2 MeV/u. In 2015-2018, HILAC commissioning had been done [3, 4]. The carbon beams С2+, С3+, С4+, С5+ и С6+ were accelerated and measured energy of accelerated carbon ions was in good agreement with the design value of 3.2 MeV/u. Beams transmission through DTL structure was estimated ~65% [3, 4]. To estimate transmission through the whole linac the only species of ions should be injected in RFQ. On that reason the ion source producing the only He+ ions was developed and assembled.