Erlangen 2001 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 23: Kernphysik/Spektroskopie III - Reaktionen
HK 23.6: Vortrag
Dienstag, 20. März 2001, 18:15–18:30, D
News from 252Cf Fission: The Low Energy Ternary Alpha’s — •U. Jahnke1, V. Tishchenko1,2, C.-M. Herbach1, D. Hilscher1, and F. Goldenbaum3 — 1HMI Berlin — 2JINR Dubna — 3FZ Jülich
The investigation of light-charged-particle (LCP) accompanied fission has 50 years of history by now which was fed by the hope that the LCPs would provide access to the dynamics and nuclear shapes of the scission configuration. While this hope has not become quite fulfilled yet because of the many unknown parameters involved in the fission process, modern multi-detector systems still can replenish the experimental knowledge.
Fission of 252Cf was studied with the 2x4π detector system NESSI with particularly low thresholds for neutrons, γ-rays and charged particles.
We observe polar and equatorial emission of ternary p, t and He. In the well known upper energy range ELPC>10MeV of the neck particles our findings corroborate the anticorrelation between ELPC on the one hand and the sum energy TKE of the fission fragments, the neutron multiplicity ν and the total γ-energy Eγ, on the other hand. Here the emission is alimented from the excitation of the fission fragments and at the expense of their TKE. The surprise, instead, comes for ELPC<10MeV. With ELCP decreasing from 10 to 1.5MeV, ν and Eγ do not increase any more but stay constant. Conversely, TKE now increases definitely more strongly than in the high ELCP-region. One could imagine that the LCPs with ELCP<10MeV have the same origin as the ones close to 10MeV, but start with initial emission angles such that they are backscattered from the fragments thereby transfering part of their kinetic energy to them. This hypothesis still has to be substantiated by trajectory calculations.