ACCULINNA: with participation of the youth from Poland

News, 03 April 2018

On one March day, Elena Puzynina and me visited the Flerov Laboratory of Nuclear Reactions on the invitation of FLNR Head of the Sector Andrei Fomichev and his team to share with our readers what the Sector staff members are involved in jointly with colleagues from Poland.

Andrei Fomichev: Team from the Warsaw University headed by professor Marek Pfutzner addressed us a request to test a new method of registration of radioactive decay using optical time projection chamber. Radionuclides are placed into the chamber sized 30X30X20 cm filled with mixture of argon and helium in which they stop and undergo decay. The stop of a nucleus and type of its decay (prompt or delayed activation of one or several particles) is fixed by the optical CCD chamber and the photomultiplier.

Grzegorz Kaminski, Senior Researcher: The optical chamber fixes all particle tracks in 3D while a time stamp is received from the photomultiplier. As the result, we get information about the type of the decay.

A.F.: We have studied exotic decays. For example, helium-8 after the beta decay into litium-8 decays into three particles: a triton, an alpha particle and a neutron. It is a rare and underinvestigated decay mode. Today, we insert beryllium-11 into the chamber. About in the middle of the chamber, the particle stops and during the stop it is likely to undergo the decay. We are interested in very rare decay modes with emission of alpha particles and a proton. If Be-11 or any other particle flies through the whole chamber, then probability of decay is likely to decrease.

In 2007, this method was worked out at the ACCULLINA facility for the first time. Decay of Li-8 was observed that decays into Be-8 and emits 2 alpha particles flying out as a rule in different directions with the angle 180. Besides, other fiducial particles were used in tests: oxygen-13 and carbon-9 decay schemes decay modes of which are familiar. When all aspects of the method were studied and adjusted, equipment was sent to the first experiment in the Michigan University in the USA. The double proton decay of Fe-45 was sensationally discovered.

G.K.: It was the first such case. Two protons for Fe-45 were expected, and they were registered. As far as equipment allowed registration of any amounts of protons, then later emission of three protons for argon-31 was observed in GSI.

A.F.: Everything operates well, the results are published in prestigious journals, there are plans for future experiments in the leading laboratories of the world such as RIKEN, CERN, GSI.

G.K.: My Polish colleagues came here from the Physical Department of the Warsaw University. Nowadays, both students and post-graduate students work here, all of them are individuals, budding scientists.

In the photo from left to right: Wojciech Dominiс, Andrei Fomichev, Natalia Sokołowska, Andrei Bezbakh, Alexander Gorshkov, Eva Adamská, Grzegorz Kaminski, Zenon Janas, Vu Dus Cong.

Professor Wojciech Dominiс: This cooperation started, as far as I remember, in 2005. In this time, we were developing the chamber with optical information retrieval. Then ACCULINNA happened to have good conditions for measurements: first, adjustment of the detector, then physics tasks were set, and they changed every year. This year we are studying Be-11, and during this experiment, we managed to work out a new method of data taking never used before.

Experiments and facilities are developing, new ideas emerge. As you can see, there are many young scientists; I am the only one elderly person. The fact that the youth is eager to come here is a marker of good cooperation between the Polish University, the international institute in Russia and this group carrying out experiments here. Everything is developing well. There are contacts, joint grants, programmes, agreements. We cooperate with the team of Andrei Fomichev not only in Dubna but in other places as well: American universities, CERN, GSI, RIKEN. More than 10 years ago, we started cooperation with Dubna, and it seems to me that it is very useful for Andrei Fomichev team as well as for us. So, every year every experiment brings something new: there are new tasks, new people join us some of whom are newcomers in the experiment, we gain new experience. Here, in FLNR, some changes are observed as well: project of a higher level are planned, modern facilities are being developed, there is equipment they start actively study and implement in the experiment.

– Are these your students around you?

– Yes, they are. There are those who are preparing to defend their Master’s degrees, there are PhD candidates as well… Three other students took the 6 pm train to walk in Moscow.

– How often do you visit Dubna?

– I visited Dubna for the first time in 1979 and, by the way, I was a student, too. Nowadays, I visit Dubna virtually every year. I took part in the experiment at the RISK spectrometer in DLNP, in Protvino, in the team of Valentin Petrukhin.

We remembered together colleagues of Dominic… Some of them passed away, some of them are still with us. We fondly remembered Valentin Petrukhin, Yuri Merekov, Zinoviy Krumshteyn. Dominic conveyed greetings to Leonid Tkachev, Georgy Shelkov, and Leonid Vertogradov. We also remembered Jerzy Knapik who was Head of JINR staff members from Poland for many years and Deputy Head of the International Cooperation Department that was headed by Henrik Gajewski…

– At present time, I participate in the project of Lenya Tkachev on study of cosmic-ray showers at Baikal, but I have no time to go there. It seems that the research programme at the RISK facility was finished in 1986… So, our conversation about memories of past years and colleagues who have passed away is quite sad… However, I have a fresh impression: recently, in Świerk, I visited a photo exhibition dedicated to the 60th anniversary of JINR that was sent from Dubna. And suddenly I saw my portrait at one of the posters. I must admit, it was pleasing!

Evgeny Molchanov, JINR Weekly Newspaper,
Photo by Elena Puzynina