An explicit partition of the fusion-like cross section

The evaporation residue cross section for fusion-like reactions of 309 MeV 14N+159Tb has been decomposed into cross sections for complete fusion and a number of specific incomplete fusion channels using a novel technique involving light-particle-KX-ray coincidences. With this partition it is possible to successfully describe the incomplete momentum transfer observed in velocity spectra of evaporation residues from a very similar system

Generation and division of excitation energy in heavy-ion collisions studied by measuring charged-particle survival fractions

Charged-particle survival fractions of primary projectile-like fragments from the 40Ar + 197Au reaction at 450 MeV were measured by using a large array of 32 phoswich detectors operating in coincidence with a detector of projectile-like fragments. Differential survival fractions of the primary pickup and stripping reaction products indicate a dependence of the average excitation energy generated in the primary fragments on the direction of the mass transfer

CALIBRATION OF PHOSWICH DETECTORS

Two important aspects for the calibration of phoswich detector arrays have been investigated. It is shown that common gate ADCs can be used: The loss in particle identification due to fluctuations in the gate timing in multi-hit events can be corrected for by a simple procedure using the measured time difference between gate and phoswich signal. The response of phoswich detectors to particles with given Z, A and E was studied using a magnetic spectrograph. In the absence of mass identification the energy calibration is limited by the width of the experimental mass distribution for a given element

Evidence for lifetime effects on the two-particle correlation function at small relative momenta for 4He induced reactions on 58Ni at 120 MeV

Small-angle correlations between two protons produced in the inclusive reaction He-4 + Ni-58 --> p + p + X at 120 MeV have been measured. The data show an enhanced cross section for a relative energy DELTA-E approximately 400 keV. Comparison with model calculations suggests an influence of a finite lifetime of the emitting source. A size parameter of 3 fm and a lifetime of approximately 10(-22)s were deduced

THE NE-20+TB-159 REACTION STUDIED WITH THE KX-RAY METHOD AT 15 MEV NUCLEON

Employing the KX-ray method, in which coincidences are measured between projectile-like fragments (PLF) and the characteristic KX rays from the target-like fragments (TLF), partial cross section d-sigma-(Z(PLF), Z(TLF))/d-OMEGA-PLF were obtained for the Ne-20 + Tb-159 reaction at E(lab) = 294 MeV for both the quasi-elastic (QE) and the deep-inelastic (DI) components. By in addition measuring triple coincidences with charged particles at back angles the results could be correct for charged particle evaporation from the TLF. Primary PLF cross section were reconstructed for both components and the corresponding probabilities for sequential charged particle decay of the fragments were deduced. The very different behaviour of the QE and DI components will be discussed. As in a previous study of the N-14 + Tb-159 reaction large cross section are observed for channels in which only nucleons and alpha-particles are emitted. Statistical model calculations were performed to deduce the excitation energy distribution of the primary PLF's. Comparison with other methods to reconstruct primary cross sections are made. The predictions of several models are evaluated

Quasi-elastic and deep-inelastic primary cross sections in the 20Ne+159Tb reaction at 15 MeV/u

The 2°Ne + 159Tb reaction was studied at E~,b = 294 MeV with the KX-ray method. Partial cross sections da(ZvLv, ZXLF)/dl2pLv were obtained for the quasi-elastic as well as the deep-inelastic components. Primary projectile-like fragment cross sections were reconstructed for both components and the corresponding probabilities for sequential charged particle decay of the fragments were deduced. These probabilities are used to extract information about the excitation energy of the primary fragments

FUSION-LIKE PROCESSES IN THE N-14+TH-232 REACTION AT 30 MEV NUCLEON

Fusionlike processes were studied in the N-14 + Th-232 reaction at 30 MeV per nucleon. Partition of the fusionlike cross section was determined by detecting nonequilibrium charged particles with an array of phoswich detectors (plastic wall) in coincidence with fission fragments for which the folding angle and thus the momentum transfer was measured. By measuring both single and multiple hits in the plastic wall and by correcting for its incomplete angular coverage a very extensive database of the fusionlike channels was obtained. The results were compared with model predictions comprising the BUU, Fermi jetting, the Boltzmann master equation model, and the nucleon-exchange transport model. It was found that these models which globally describe the dependence of the inclusive momentum transfer in fusionlike reactions cannot account for the associated particle production, in particular if the nucleons bound in the observed complex particles (d,t,alpha) are included in the comparison. Calculations of the energy spectra of the complex particles with the coalescence formalism indicate that a large fraction of the observed complex particles in the fusionlike reactions cannot be accounted for by pre-equilibrium emission from the fused composite system. They most probably originate from massive-transfer-type reactions that contribute to the beam-velocity component in the energy spectra