ترغب بنشر مسار تعليمي؟ اضغط هنا

Fusion excitation function revisited

44   0   0.0 ( 0 )
 نشر من قبل Philippe Eudes
 تاريخ النشر 2012
  مجال البحث
والبحث باللغة English




اسأل ChatGPT حول البحث

We report on a comprehensive systematics of fusion-evaporation and/or fusion-fission cross sections for a very large variety of systems over an energy range 4-155 A.MeV. Scaled by the reaction cross sections, fusion cross sections do not show a universal behavior valid for all systems although a high degree of correlation is present when data are ordered by the system mass asymmetry.For the rather light and close to mass-symmetric systems the main characteristics of the complete and incomplete fusion excitation functions can be precisely determined. Despite an evident lack of data above 15A.MeV for all heavy systems the available data suggests that geometrical effects could explain the persistence of incomplete fusion at incident energies as high as 155A.MeV.

قيم البحث

اقرأ أيضاً

178m2-Hf is an extremely interesting isomeric state due to its potential energy capacity level. One possible way to obtain it is by irradiation of a nat-Ta sample with a high-current proton accelerator. Up to now, there was no information in the inte rnational experimental nuclear data base (EXFOR) for this reaction. Irradiations of nat-Ta samples performed for other purposes provide an opportunity to address this question. This paper presents the 172m2-Hf independent production cross-sections determined by gamma-ray spectrometry. The nat-Ta(p,x)172m2-Hf excitation function is studied in the 20-3500 MeV energy range. Comparisons with results by several nuclear models (ISABEL, Bertini, INCL4.5+ABLA07, PHITS, CASCADE07, and CEM03.02) used as event-generators in modern transport codes are also reported. However, since such models are generally not able to separately predict ground and isomeric states of reaction products, only 178-Hf independent and cumulative cross-section data are compared.
The photoproduction of $eta$-mesons off nucleons bound in $^2$H and $^3$He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the $etarightarrow 2gamma$ and $etarightarrow 3pi^0$ decays and the recoil nucleons were detected with an almost $4pi$ electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of $gamma nrightarrow neta$. The results from the two measurements are consistent taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are $W$ = (1670$pm$5) MeV and $Gamma$ =(30$pm$15) MeV. For the first time precise results for the angular dependence of this structure have been extracted.
The ongoing discussion concerning the nature of the scalar resonances f_0(980) and a_0(980) implicated to extend the studies of the pp -> ppK+K- reaction near the production threshold. Furthermore, such elementary production processes allow to study the interaction of the outgoing particles due to their low relative momenta. Therefore, final state interactions in the pK or K Anti-K system can be perfectly studied in such experiments. The acquired data at the excess energies Q=10 and 28 MeV have been taken at COSY-11 and the status of the ongoing analysis will be presented.
330 - M. Avrigeanu , V. Avrigeanu 2011
We show that the model analysis of new measured (d,p), (d,t), (6He,5He), and (6He,4He) reaction cross sections at incident energies around the Coulomb barrier (J. Phys. G: Nucl. Part. Phys. 38 (2011) 035106) led to results that are not consistent wit h similar calculated and evaluated data. On the other hand, it should be corrected by taking into account the direct processes.
Background: The cross section for forming a heavy evaporation residue in fusion reactions depends on the capture cross section, the fusion probability, PCN, i.e., the probability that the projectile-target system will evolve inside the fission saddle point to form a completely fused system rather than re-separating (quasifission), and the survival of the completely fused system against fission. PCN is the least known of these quantities. Purpose: To measure PCN for the reaction of 101.2 MeV 18O, 147.3 MeV 26Mg, 170.9 MeV 30Si and 195.3 MeV 36S with 197Au. Methods: We measured the fission fragment angular distributions for these reactions and used the formalism of Back to deduce the fusion-fission and quasifission cross sections. From these quantities we deduced PCN for each reaction. Results: The values of PCN for the reaction of 101.2 MeV 18O, 147.3 MeV 26Mg, 170.9 MeV 30Si and 195.3 MeV 36S with 197Au are 0.66, 1.00, 0.06, 0.13, respectively. Conclusions: The new measured values of PCN agree roughly with the semi-empirical system- atic dependence of PCN upon fissility for excited nuclei.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا