Collinear cluster tri-partition as a probe of clustering in heavy nuclei D. Kamanin, JINR Dubna

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1 Collinear cluster tri-partition as a probe of clustering in heavy nuclei D. Kamanin, JINR Dubna Exciting Makutsi, South Africa, November 2011

2 FOBOS 4π-detector of charged particles,

3 Challenge Make presentation in a pedagogic way W. Greiner to the modern nuclear physics Is it possible after so many years of the study of nuclear fission to observe some new bright phenomena in the fission experiment? With rather simple equipment and within low run time? With a well studied simple system Cf(sf) or 235 U(n th,f)? Multi-clustering studied with mosaic TOF-E spectrometer Possible with analysis of unusual information

4 I. Background: Theory and experiment

5 Starting point in theoretical treatment Nucl. Phys. 46 (1963) 639 X~z 2 /A is the conventional liquid drop model parameter W(x)- is the difference of the potential energy of the deformed nucleus and that of the initial sphere - two-neck shapes (3) and three-neck shapes (4) are marked by the red arrows; - red points are shown as most favorable for the formation of a quasi-molecule

6 Ways of tripartition H. Diehl & W. Greiner, Nuclear Physics A229 (1974)

7 Theory at the edge of new Millenium 132 Sn 46 Ar 28 Aligned and compact configurations for α-accompanied and α+ 6 He+ 10 Be Yu.V. Pyatkov, V.V. Pashkevich, A.V. Unzhakova et al., Physics of Atomic Nuclei 66 (2003) 1631 accompanied cold fission of 252 Cf D.N. Poenaru et al., Phys. Rev. C 59 (1999) 3457

8 Nowadays theoretical results V. Zagrebaev and W. Greiner Proc. Internat. Symp. on Atomic Cluster Collisions (ISACC07), GSI Darmstadt, 2007, (Imperial College Press, London, 2008), Eds. J.-P. Connerade and A. V. Solov'yov, pp

9 Experimental study of true ternary fission: contradictory results P. Schall, P. Heeg, M. Mutterer, J.P. Theobald (1987) Y 3 <10-8 /bin.fiss Diogenes P. Schall, P. Heeg, M. Mutterer, J.P. Theobald, Phys. Lett. B 191 (1987) 339] M.L. Muga et al., (1967) - Y 3 ~10-6 /bin. fiss., but it was strongly criticized ;

10 Polar emission : in fact previous CCT experiments Y 3 ~10-5 /bin. fiss. no chance to detect heavy LCP

11 Usual ternary fission of low excited nuclear systems Conventional ternary fission ~2x10-3 /bin.fiss. S.A.Karamyan Activation analysis ( 4 He ) F. Gönnenwein, Nucl. Phys. A 734 (2004) 213

12 II. Novel way of analysis of the experimental data: Fine structure of the TKE-M distributions

13 Fine structures of mass-energy distribution The typical contour map of the experimental mass-energy distribution of fission fragments

14 Fine structure of the mass (charge) distribution Fragment mass Resolution of unresolved doublet by the second derivative method

15 MEPhI spectrometer (TOF-E) TKE (MeV) Mass (amu) Cosi fan tutte spectrometer Yu.V. Pyatkov et al., NIM A 488 (2002) 381 NIM A303 (1991) 323; NIM 219 (1984) 569

16 Cooperation with SUN and MSU on Morphological filtering test Band-pass filter M-filter TKE TKE Fragment mass Fragment mass Workshop Imaging and Clustering 31 October 6 November 2007, CT

17 Presumable shapes of the fissioning system in the framework of Ge-Sn fission mode for: The most compact configuration (a), some grater elongation (b), prescission phase (c) Yu. V. Pyatkov, V.V.Pashkevich, W. H. Trzaska et al., Physics of Atomic Nuclei, V. 67( 2004) 1726

18 III. Experiments with FOBOS detector: Search of CCT by study the missing mass

19 Collinear Cluster Tripartition

20 Individual masses measured by TOF-E no kinematical assumptions, Z -sensitive variables & experimental neutron multiplicity ν exp for selection of the CCT events

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22 the same can happened at the edge of the detector!

23 JYFL Spectrometer Mesh effect check Al foil 252Cf Silicon detector #5 MCP detector #4 MCP detector #3 MCP detector #2 MCP detector #1 Silicon detector # till window 72 till window

24 Ni-bump observed in several experiments

25 Z evidence: it is really Ni-bump!

26 Internal structure of the Ni-bump: the ridges M1+M2=const

27 Results were published in:

28 CCT as a new kind of cluster decay (radioactivity) H.J. Rose and G.A. Jones, Nature 307 (1984) 245 Yu.V. Pyatkov, D.V. Kamanin et al., EPJ A 45 (2010) 29

29 Additional bumps based on deformed magic clusters Y Mo ~1% / bin.fiss.

30 236 U* Selection of symmetric decays Each point: V1 V2 P1 P2 Z1 Z2 6 independent experimental parameters 252 Cf V1 V2 P1 P2

31 Selection of the CCT events using drift-time CCT Yu.V. Pyatkov et al., Bulletin of the Russian Academy of Sciences. Physics, 75 (2011) 949

32 Presumable scenario of the LCP accompanied collinear cluster tri-partition At some stage of elongation of the decaying system it clusterizes into two magic constituents such as Sn/Mo, Cd/Ru etc. Each initial cluster clusterises during an elongation of the fissioning system (secondary clusterization) forming lighter magic cluster and at least one light particle. The mechanism seems to be close to this standing behind a well known Ikeda rule.

33 IV. Experiments with mosaics of PIN with MCP timing: Measurement of ternary correlations

34 Experiments in JYFL 252 Cf(sf) and 236 U+α

35 Preliminary results on observation of collinear cluster tripartition in 232 Th +d (10 MeV) reaction. ISINN May 2009 Dubna 8 6 Ms_cor Ms counts/2amu Ms(amu) Total mass of 3 correlated fragments measured to be improved

36 COMETA Correlation Mosaic E-T Array

37 COMETA data: Ni-bump & Ge-bump without any gating 134 Te 80 Ge 144 Ba 72 Ni 128 Sn 68 Ni 68 Ni/ 128 Sn 68 Ni/ 134 Te

38 Neutron gated data, n=3 & V-E gate prescission neutrons? dm=4 Rectangular structure similar to these observed earlier but: based on deformed magic clusters 1. Neutron source being at rest; 2. Low missing mass; prescission neutrons? 38

39 Ternary decays, all 3 fragments were detected By definition: m1>m2>m3 Bright manifestation of clustering dm12s ~ 40amu &Ms12<258 39

40 Collinear ternary decays, (secondary) clusterization of m3? d d boundary for the lightest LCP 40

41 COMETA-2 setup, TOF-E part

42 LI te nearspectrometer = LIS

43 Conclusions 1. New bright phenomenon is observed CCT. 2. CCT is due to the preformation of at least two magic clusters, deformed as well. The CCT modes based on these combinations are more preferable. 3. There is a open field for systematic study of CCT since it may bring us a new knowledge on fission process. 4. There are new sources of information (FS, trajectories in MM). This work is supported in part Collaboration in experiments and analysis JINR (Dubna), MEPhI (Moscow), ATOMKI (Debrecen), JYFL (Yuväskylä), HMI (Berlin), MSU (Moscow), SUN (Stellenbosch) with support of INP (Kiev), INR RAS (Moscow), KRI (St-Peterburg), by the grant of the Department of Science and Technology of South Africa by the grant of the Federal Ministry of Education and Research of Germany

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45 Next steps: another CCT modes

46 Drift time application Drift time 1 calculated (channels) CCT True drift time D even for scattered fragments Drift time 1 (channels) Yu.V. Pyatkov et al., Phys. Of Atomic Nuclei 73 (2010) 1309

47 Symmetric cluster configurations in the CCT of 236 U* Momentum & Drift_time selection Selection of symmetric decays

48 Selection of the CCT events using drift-time CCT Yu.V. Pyatkov et al., Bulletin of the Russian Academy of Sciences. Physics, 75 (2011) 949

49 Parameters of the LCP detected 12, 14 C Be Ne

50 Experimental summary and theoretical support Symmetrical valley Asymmetrical valley V. Pashkevich et al., International Journal of Modern Physics E, v. 19, (2010) 718

51 Next steps: common approach to physics of -conventional ternary fission -polar emission -heavy ion radioactivity - CCT

52 Upgrade of the COMETA setup: increase of aperture COMETA-2: 32 PIN-diodes & neutron belt 28 3 He counters

53 Sequential (cascade) ternary fission (excitation energy of a heavy fragment is enough for the second scission appears to occur). 238 U, 197 Au + 22 Ne (185 MeV) 209 Bi, 238 U + 40 Ar (310 MeV) Karamian S.A., Kuznetsov I.V., Oganessian Yu.Ts. and Penionzkevich Yu.E., Jadernaja Fizika 5 (1963) 959 Two and three-body exit channels in the reactions 84 Kr Er Xe Sn at 12.5 MeV/u A fast two-step mechanism where a sequential fission-like process follows a deep inelastic collision with very large energy losses. An orientation of the fission axis is approximately collinear with the axis of the first fission. All the properties observed present consistent evidence for a new phenomenon of non-equilibrium fission Besides the already observed sequential binary process, the presence of prompt ternary break-up of the composite system is revealed in 32 S + 59 Co 91 Tc 32 S + 63 Cu 95 Rh reactions at 5.6 MeV/u. The decay appears to occur in a collinear configuration. In spite of the large energy dissipation some events shows structure effects, i.e. the possible presence of slustering phenomena in the reaction (at least one fragment is an α-like nucleus) P.Glässel et al., Z. Phys. A310 (1983) 189 first ruptures second L.Vannuci et al., Eur.Phys. J. A 7 (2000) 65 prompt ternary break-up of a collinear configuration

54 Background Cluster radioactivity Ra 14 C 221 Fr 242 Cm 14 C H.J. Rose and G.A. 34 Si Jones, Nature 307 (1984) ( ) P α 245 Lead radioactivity Binary decays Cold fission Tin radioactivity... Light α cluster nuclei Ikeda et al. [Suppl. Prog. Phys. (Japan) Extra (1969) 464] speculated a rang of different cluster structures might occur in 24 Mg nucleus: α + 20 Ne, 8 Be + 16 O, 12 C + 12 C, 12 C + 12 C chain and a 6α chain state. There is now evidence for all these different structures [B.R. Fulton, Z. Phys A349 (1994) 227] Multicomponent nuclear molecules

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57 New mosaic spectrometer COMETA (Correlation Mosaic E-T Array) Direct detection of all CCT partners

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60 The missing mass method The major structures observed

61 Start PAC with source inside Al 2 O 3 Separation of the correlated pair by the grid Stop PSAC Ionization chamber 50 cm 252 Cf Probability

62 The missing mass method The major structures observed

63 Experiment #1 (FOBOS) The layout of the Run #1 Module1 Module Cf start MCP detector Collected 2x10 7 events dispersed intact baseline effect counts (Ma+Mb) amu

64 What is observed? With different setups, by different teams, with variation of the experimental conditions More than two massive fragments TOF-E analysis, confirmed by Z selection Perfect collinear configuration alignment of the order of 1 Two or more fragments are magic clusters known shells and sub-shells Total yield ~10-3, individual modes Recognizable trajectories in mass-mass and mass-energy distributions Positive theory background Strong indication of multi-clustering decays of actinides!!! Reason for systematical study of multi-clustering

65 Experimental setup Data array 5.5*10 6 ATOMKI, June 2008 slow fast

66 Energy of A3 fragment from ternary decay W. von Oertzen, K.R. Vijayaraghavan, M. Balasubramaniam, et al., EPJ A (to be submitted) 66