! (Inverse-kinematics) fission investigations in active targets 1. First experiment performed in GANIL.! 2. Exploring exotic fissioning systems with ACTAR TPC. C. Rodríguez-Tajes et al., rodriguez@ganil.fr! GANIL (France), University of Santiago de Compostela (Spain)!! ACTAR TPC Collaboration Workshop. 18th-20th November 2015, Caen (France). 1
Motivations fission Fission fragment yields Calculated Exp. Atomic number Randrup et al., Phys. Rev. C. 88 (2013) 064606. Fission barrier (MeV) Z=84, Po Neutron number Mamdouh et al., Nucl. Phys. A 679 (2001) 337. Accurate fission models are phenomenological. Requirements of fundamental and applied research remain unaccomplished. 2
Exotic fissioning systems r-process of nucleosynthesis: fission forced at: distributions of : s ces o r r-p sio s fi y c n g n i cl Goriely et al., Nuclear Structure and Dynamics 2012. Search for superheavy nuclei: Stability predictions,! survival probability in experiments. Nuclear energy: Transmutation, Th cycle. Properties of the fission fragments, fission probabilities, fission barriers, etc. are needed. 3
The experimental perspective Transfer-induced fission in inverse kinematics target-like The light recoil characterises the transfer reaction. heavy-ion beam! 5-7 MeV/u light target compound nucleus CN heavier, and more neutron rich than the beam.! Exotic heavy-ion beams will bring access to new systems, but I~106pps! Could we use an active target? How does the use of a transfer reaction aect fission? J.E. Escher et al., Phys. Rev. C 74 (2006) 054601. 4
A first experiment in MAYA E653 collaboration : GANIL, University of Santiago de Compostela, University of Huelva, University of Lisbon, KU Leuven, KVI. 238U beam +12C target.! Gas: ic4h10 at 50 mbar. religh co t! il e- Detection of light target-like recoil in ancillary Si telescope.! Tracking of the two FF in MAYA. Objectives: Fission probabilities, and anisotropies for each transfer channel. 238U beam first step towards future projects with ACTAR TPC! 5
Adaptations of the setup Beam: 238U at ~6 MeV/u, I~106pps. Ebeam~ 1 GeV and ~1013 electron-ion pairs/s created. Deformation of electric drift field! Development of a dedicated beam mask. Tested with 136Xe beam (June 2013). field simulation! (J. Pancin, S. Damoy) C. Rodríguez-Tajes et al., Nucl. Instr. Meth. A 768 (2014) 179. 6
Measuring fission. GANIL, December 2014. Despite the use of the beam mask, amplification needed to be limited to avoid beaminduced signals, and sparks on the detector. Ibeam~104 pps 12C Typical energybeam loss/cm! dump! beam mask 7
Two running modes 1. Fission runs: Low gain, high intensity: Only FF detected in MAYA. Si detectors! 40 um, DSSSD! 500 um! 700 um 2. Normalisation runs: Higher gain, low intensity. Light nuclei detected in MAYA. light recoil light recoil 238U beam 8
Fission runs Angle of the reaction plane: Ibeam~106 pps beam Vertical position (mm) 1 2D 2 deformation of UP trajectories 1 mask 2 e- position of anode wires (mm) up up,reconstructed +5 Limit of the beam-mask performance: 238U, I 6 beam~10 pps.!! Down trajectories can be accurately reconstructed. 9
Transfer reaction Identification of transfer channels: 12,13,14C 11B 4He 7Li 9,10Be Eight fissioning systems: 236-238U, 239Np, 240-242Pu, 243Am. Reconstruction of the reaction kinematics will provide the excitation energy. In normalisation runs, light-particle trajectories need to be reconstructed in MAYA. 10
Normalisation runs Very light particles (like p) could not be measured. For the heavier ones: Ibeam~105 pps 12C Biased trajectory reconstruction. Real trajectory. DSSSD Standard" reconstruction Improved reconstruction 2cm 11
ACTAR TPC The MAYA experiment has shown the feasibility, and diiculties of the technique. Will it be improved in ACTAR TPC? Gain on the pads can be adjusted individually. HIGHER GAIN FOR light LIGHT PARTICLE Beam DETECTION REDUCED GAIN Better angular coverage of the recoil.! FF measured in ancillary silicon detectors. recoil Beam 12
Future experiments 238U+12C in the MAYA active target. New opportunities at HIE-ISOLDE: Heavy radioactive-ion beams, I~106 pps. Cm (96) N=126 Am (95) Pu (94) Np (93) U (92) Pa (91) Th (90) Ac (89) Ra (88) Fr (87) Rn (86) At (85) Bi (83) Po (84) Tl (81) Pn (82) Z=82 13
Short term (d,p) transfer-induced fission of heavy radioactive beams: 193Tl, 199Bi, 201At, 209Fr. M. Veselsky, R. Raabe et al. 28 shifts (~10 days) of beam time approved.! 5.5 MeV/u expected in July 2016.! Beam time expected by the end of 2016! reduced fissility parameter Future experiments: HIE ISOLDE Exp. fission barriers lower than! model predictions. I2=(N-Z)2/A2 M. Dahlinger, D. Vermeulen and K.H. Schmidt, Nucl. Phys. A 376 (1982) 94. Longer term (2018?) Multi-nucleon transfer-induced fission. More n-rich systems and heavier transfer reactions.! Project submitted at the university of Lisbon (C. Rodríguez-Tajes, D. Galaviz, et al.) 14
Backup slides 15
MAYA ic4h10 100 mbar r ge é l uit od pr 238U, I=106 pps 16
Angles in the laboratory: Dependence of the fusion-fission cross-section with the beam energy Elastic on Ti window 238U+12C -> 250Cf* Energy in CM fission fragments Angular distributions to be corrected from geometric eiciency, and transformed to the centre of mass. 1.13VB 1.03VB 49 43 Fission of energies. 250Cf 0.94VB Excitation! energy (MeV) 36 at dierent excitation 17
238U+12C elastic scattering f usion f ission 1.13VB 1.03VB 0.94VB 0 Energy in CM 18
Transfer-induced fission at HIE-ISOLDE transfer 221-228Ra 218-228Fr Intensities: up to 109 pps (105 pps at GSI), at 106pps, 0.5 fissions/s. 19