Bulgaria at ISOLDE Georgi Rainovski

Few facts about ISOLDE ISOLDE (Isotope Separator On Line DEvice) is the CERN radioactive beam facility In operation since 47 years The largest selection of isotopes of any ISOL facility worldwide Provides low energy and post-accelerated beams Open to users from around the world Nuclear structure; Exotic decay modes; Laser spectroscopy and direct mass measurements; Radii and moments; Nuclear reactions of astrophysical interest; Fundamental physics; Solid state physics ; Medical physics (MEDICIS);

MoU from 2017 (following those in 1993, 2007 and 2012) ISOLDE collaboration 15 countries + CERN Belgium, Denmark, Finland, France, Germany, Greece, Italy, Norway, Poland, Romania, Slovakia, South Africa, Spain, Sweden, United Kingdom MoU from 2017 (following those in 1993, 2007 and 2012) Annual budget 870 kCHF (each country pays annual fee of 60 kCHF) support for beam developments; support for experiments (buying LN2, common equipment, consumables, etc.; support for some personnel – RILIS, visitors, secretary; support for students staying at CERN; Contributions to upgrades (HIE-ISOLDE); Presently there are 132 active experiments; 385 scientific publications in the period 2011 – 2015; 177 theses in the period 2012-2016;

Bulgarian participation at ISOLDE Prof. Krasimira Marinova (UNI Sofia, JINR Dubna) COLLAPS – laser spectroscopy Mean square charge radii for 17−28Ne Geithner et al, PRL 101, 252502 (‘08) Marinova et al, PRC84, 034313 (‘11) Clear correlation between the charge radii and the empirical β2 deformation parameters; 17Ne can be consider as a candidate for nucleus exhibiting proton halo; For neutron reach nuclei the neutron excess affects the spin-orbit and the proton-neutron interaction  different ordering of the single particle states;

Surprising simplicity Advanced laser spectroscopy of the very exotic odd-mass 107-129Cd isotopes All quadrupole moments associated with the unique-parity h11/2 orbital increase linearly with respect to the number of neutrons, as predicted by the extreme shell model.

Tilted-foil-beta-NMR Beta particles (e-,e+) can be used as a detection tool, instead of rf absorption (beams down to 1000 ions/s can be studied) Measured asymmetry: First spin-polarized beam (8Li) produced with tilted foils after the REX linac (300 keV/u). Polarization 30 % Lead by G. Georgiev & T. Nilsson

Nuclear physics groups at University of Sofia, Faculty of Physics Prof. G. Rainovski, Assoc. Prof. K. Gladnishki, Assist. Prof. M. Djongolov + 2PhD and 2 MSc student Nuclear structure studies – isovector collective states, phase transitions, magnetic moment measurements Main involvement -ray spectroscopy with post-accelerated RIBs – MINIBALL-C(T)REX @ HIE-ISOLDE IS485, IS494, IS496, IS510, IS523, IS524, IS546, IS548, IS549, IS551, IS557, IS559, IS562, IS596, IS628 T(C)REX Scattering chamber consisting of several E-E detectors allowing for identification and spectroscopy of charge particles or ions after Coulomb excitation or transfer reactions MINIBALL -ray array consisting of 24 six-fold segmented HpGe detectors (8 clusters) High efficiency – 20% @ 1.3MeV; High energy resolution; High segmentation  precise Doppler correction;

A study of collective isovector valence shell excitations in unstable nuclei in the vicinity of the double magic nucleus 132Sn PI: Prof. Nobert Pietralla (TU Darmstadt)&Prof. Georgi Rainovski (UNI Sofia) The one-phonon 2+1,ms is the fundamental quadrupole-collective isovector excitations in the valence shell for spherical vibrational nuclei unique experimental signature – strong M1 transition; sensitive to the p-n interaction in the valence shell; the fragmentation is reflects the underlying shell structure; the properties of MSSs reflect the p-n balance in the collective wave function; unambiguously fixes some parameters in shell model (effective charges and g factors); but difficult to be identified experimentally – requires complete spectroscopy 0+ 2+1 2+1,ms M1 E2 0+1 = a 0+10+1 + ... 2+1 =  0+12+1 +  2+10+1+ ... 2+2 =  0+12+1 –  2+10+1+ ...

REX-ISOLDE experiment IS496 Study of the effect of shell stabilization of the collective isovector valence-shell excitations along the N=80 isotonic chain – IS496 (TU Darmstadt – UNI Sofia) identify the MSSs of 140Nd and 142Sm (radioactive); method – inverse kinematics Coulomb excitation experiments – proven in the case of 132Te; problems – RIB of 140Nd and 142Sm need to be developed, the B(E2;2+1 → 0+1) need to be measured, beam energy of 85% CB (3.62 – 4.5 MeV/u); HIE-ISOLDE Z=50 N=80 N=82

REX-ISOLDE experiment IS496 - results Beams for 140Nd, 142Sm (primary target material: Ta) have been developed, tested and used successfully, including RILIS ionization scheme Beam intensities: 5105 pps Beam energy 2.85 MeV/u 140Nd (targets 48Ti, 64Zn) 142Sm (targets 48Ti, 94Mo) 140Nd: B(E2;2+10+1)= 33 (2) W.u. 142Sm: B(E2;2+10+1)= 32 (4) W.u. HIE-ISOLDE is operational delivering beams with 5.5 MeV/u (10 Mev/u in 2017?) HIE-ISOLDE experiment IS546 (expected 2017) Quantitative identification of 2+ MSSs of 140Nd and 142Sm via measurement of B(M1) strength HIE-ISOLDE experiment IS596 (expected 2017) 2+ Anomaly and Configurational Isospin Polarization of 136Te

Bulgarians at ISOLDE experiments COLLAPS Prof. Krasimira Marinova (JINR) Prof. Dimiter Balabanski (ELI-NP) Dr. Deyan Yordanov (CSNSM Orsay) REX-ISOLDE, MINIBALL Prof. Dimiter Balabanski (ELI-NP, Bucharest) Dr. Georgi Georgiev (CSNSM Orsay) Dr. Andrej Blazhev (Uni Köln) Prof. Georgi Rainovski (Uni Sofia) Assoc. Prof. Kalin Gladnishki (Uni Sofia) Assist. Prof. Martin Djongolov (Uni Sofia) ISOLTRAP Dinko Atanasov (TU Dresden) Mӧssbauer spectroscopy at ISOLDE: Dr. Petko Krastev (INRNE Sofia) Bulgarian summer students at ISOLDE: Bozidar Dimitrov (2015) Maria Trichkova (2014, PhD student at Uni Sofia) Vasil Karayonchev (2013, PhD student at Uni Köln) Antoaneta Damyanova (2011, PhD student at Uni Geneva)

Expenses for travels and stays at CERN only! Bulgaria at ISOLDE Bulgarian Nuclear physics community is relatively small but vital; The involvement of Bulgarian scientists in ISOLDE experiments is long standing and visible but it is mostly personal rather than institutional one; Funding National funding – National Science Fund (severely limited, excludes funding for long-term involvements, unpredictable funding cycles) 2009 – 2012 partial support  5 k€ (grant DO 02/219); 2017 – 2019 partial support  15 k€ (conditional) (grant DN 08/23); External funding – Alexander von Humboldt foundation and ENSAR TNA06 – in total  7 k€ for the period 2012 - 2015; CERN support – 4 summer students (2011-2014), 1 CAS (2016); Expenses for travels and stays at CERN only! No funding for M&O costs, upgrades, R&D and investments (detectors, DAQ etc.)! Bulgaria is not a member of ISOLDE collaboration!

Future scientific programs Reasons to join ISOLDE to “legalize” our participation in ISOLDE and to bear a part of the expenses for keeping the experiment running; to provide a more sustainable financing for Bulgarian teams involved in ISOLDE experiments; to allow the Bulgarian teams to assume more active role and responsibilities in the experiments; to allow more Bulgarian scientists and students to become involved; to continue nuclear structure studies - Search for MSSs in unstable nuclei (UNI Sofia, Georgi Rainovski) – experiment IS546&IS596 (approved), Nuclear moment measurements (UNI Sofia&Orsay, Kalin Gladnishki) – experiment IS560 (approved), Emission Mössbauer spectroscopy (INRNE, Petko Krastev) – experiment IS576&IS578 (approved), to get involved in preparing experiments with transfer reactions at HIE-ISOLDE (UNI Sofia); Future scientific programs to get involved in the project MEDICIS –huge interest even outside the nuclear physics community: Bio-physics and medical physics group at Uni Sofia, Leandar Litov; Cyclotron center for medical isotopes at INRNE, Dimiter Tonev, Nikolay Gutev; National Center of Radiobiology and Radiation Protection; National Oncology Medical Center – Elena Piperkova;

Can Bulgaria join ISOLDE? ISOLDE collaboration Bulgaria is welcomed to join ISOLDE at a reduced fee of 30 kCHF for the first 2 years; Ministry of Education and Science (Funding and coordinating agency for Bulgarian activities at CERN) summer of 2013 – after the visit of the minister in CERN we were encouraged to initiate the process; November 2013 – a formal request for joining ISOLDE was sent to the ministry; February 2014 – an advisory committee for coordinating the Bulgarian activities at CERN was established at the ministry. The committee endorsed the request for ISOLDE and requested a draft of the MoU; March 2014 – a draft of the MoU was presented. The committee approved the draft and made a recommendation to the minister to sign the MoU under the following conditions: - Bulgaria becomes member of ISOLDE collaboration at a reduced fee (30 kCHF) for 2015 and 2016; - activities of Bulgarian institutions at ISOLDE will be evaluated for those two years and depending on the results will be decided whether to continue the Bulgarian participation as a regular member; April 2014 – Prof. Sergio Bertolucci signed the MoU for CERN and the ministry starred the administrative procedure for signing the MoU  problem!

Can Bulgaria join ISOLDE? The problem: there is no legal basis to allow the minister to sign a MoU with financial commitments! The MoU expired in 2016 and was replaced by a new one in 2017 ISOLDE collaboration Bulgaria is welcomed to join ISOLDE at a reduced fee of 30 kCHF for the first 5 years; We are still waiting for a decision from the ministry! but there is a hope National program for participation at CERN Thank you for your attention!