In March 2017, the new fragment separator ACCULINNA-2 was launched in the Flerov Laboratory of Nuclear Reactions as part of the implementation of the DRIBs-III project. The new ACCULINNA-2 fragment separator is the basis of FLNR research in the fields of light exotic nuclei near the nucleon drip-line. Studies in the field have been already twice marked by the JINR Prize in 2018 and 2019. Andrey Fomichev, Head of FLNR Sector No.6, told the JINR Weekly Newspaper about the progress in the project.

Ten years ago, in July 2010, our first meeting with representatives of the French company “SIGMAPHI” was held to discuss the creation of the new fragment separator ACCULINNA-2.

President of the company Jean Luc Lancelot and a leading ion optics specialist William Beeckman visited FLNR JINR for the first time and got acquainted with the installation place of the facility in the hall of the U-400M accelerator and beyond as well. In further reports, when the facility was constructed, W. Beeckman quoted the Bible “At the first there was chaos…” thus expressing first impressions of what he saw in 2010 (photo 1, on the left). Anyway, one year later, on 28 September 2011, a long-term contract was signed for the supply of turnkey equipment (39 magnets with power sources, vacuum equipment and special units for beam monitoring), its installation, adjustment, and launch.

Photo 1. Equipment installation in the hall of U-400M in 2010 (on the left) and in 2014 (on the right)

In 2014, all parts of the ACCULINNA-2 fragment separator consisting of a 53-metre long S-shaped line for transporting the initial beam from the accelerator to the conducting target in the F1 zone and the secondary beam from F1 into F5 (photo 2) were installed and adjusted in 3D space with an accuracy of 100 microns. In December 2015, the technical launch of the facility with the initial beam was held. In 2016, the first radioactive beams were obtained in the final focal plane of the F5 separator. In 2017, the first experiments started. It is important to note that all the calculated parameters (output of fragments per a time unit, the coefficient of purification from impurities, the cross-sectional size of the beam in focal planes) were experimentally confirmed. Now, W. Beeckman would say: “We have built not only a precision facility but also a strong friendship.” The strength of these relations was reinforced by the two further contracts with the SIGMAPHI company for the production of dipole magnet as a part of the zero-angle spectrometer in F5 (2017) and a high-frequency filter for purification of the secondary beam from impurities in the F3 plane (2019). This year, jointly with employees of the RFNC “All-Russian Research Institute of Experimental Physics” (Sarov) and the DZHM (Dzerzhinsk), the facility will be equipped with unique devices (the only one in the world) for work with the cryogenic tritium target. This will provide new opportunities for the study of neutron-excessive isotopes that are far from the drip-line, such as ⁷H, ¹⁰He, ¹³Li, ¹⁶Be and others./p>

Photo 2. Installing equipment of ACCULINNA-2 in the experimental hall and beyond it in 2020

In less than three years of the facility’s operation, a series of bright experiments was carried out to study the properties of neutron-excessive nuclei ⁷H, ^6,7He, ^9,10Li, as well as a joint experiment with a group from Warsaw University on the study of rare decay channels of neutron-deficient isotopes ²⁷S and ²⁶P. Information about it was published in well-known refereed journals Nucl. Instruments and Methods, Eur. Phys. Journal A, Phys. Rev. Lett., “Izvestia RAS” and others. It is also available on the website http://aculina.jinr.ru/a-2.html. The facility is equipped with the unique detectors of charged particles, neutrons and gamma quanta. It has advanced electronics and auxiliary equipment. A close-knit team of young and talented employees work under the guidance of famous professors and leading specialists, such as G. M. Ter-Akopian, M. S. Golovkov, L. V. Grigorenko, R. Wolski and E. Yu. Nikolsky. The core of the team is represented by Sergey Krupko, Alexander Gorshkov, Vratislav Chudoba, Pavel Sharov, Andrei Bezbakh, Bogumił Zalewski. Research is conducted in close cooperation with colleagues from the JINR Member States and world-leading centres, such as GSI (Germany), RIKEN (Japan), RAON (South Korea), NSCL@MSU (USA). And, to continue the biblical saying we may say that today, the fragment separator ACCULINNA-2 is a blooming garden with high potential for scientific discoveries.

Andrey Fomichev,
Head of Sector No.6, Flerov Laboratory of Nuclear Reactions JINR