Inference on fission timescale from neutron multiplicity measurement in18O+184W

The pre-scission and post-scission neutron multiplicities are measured for the 18O + 184W reaction in the excitation energy range of 67.23−76.37 MeV. Langevin dynamical calculations are performed to infer the energy dependence of fission decay time in compliance with the measured neutron multiplicities. Different models for nuclear dissipation are employed for this purpose. Fission process is usually expected to be faster at a higher beam energy. However, we found an enhancement in the average fission time as the incident beam energy increases. It happens because a higher excitation energy helps more neutrons to evaporate that eventually stabilizes the system against fission. The competition between fission and neutron evaporation delicately depends on the available excitation energy and it is explained here with the help of the partial fission yields contributed by the different isotopes of the primary compound nucleus.

Fragmentation analysis of 105Ag∗ nucleus governed via complete and incomplete fusion channels at Ec.m. = 89MeV

A systematic study of dynamical aspects associated with heavy-ion-induced [Formula: see text] reaction is carried out at center-of-mass energy [Formula: see text] MeV. The complete fusion (CF) and incomplete fusion (ICF) contributions are estimated by using the dynamical cluster-decay model (DCM). The incomplete fusion component is examined by normalizing the incident beam energy for each of the breakup fragment. The fusion evaporation cross-sections that emerged from CF and ICF channels are duly addressed using the optimized value of neck-length parameter [Formula: see text]. Further, the mass yield of compound nuclei (CN) formed in the CF and ICF processes is analyzed with respect to angular momentum [Formula: see text] values. The DCM-based calculations indicate the possible contribution of deep inelastic collision (DIC) in the decay of [Formula: see text] at higher [Formula: see text] values, and DIC cross-sections are predicted which call for future validation.

The potential benefits of using higher X-ray energies for macromolecular crystallography

Using X-ray energies higher than those normally used (5–15 keV) for macromolecular X-ray crystallography (MX) at synchrotron sources can theoretically increase the achievable signal as a function of dose and reduce the rate of radiation damage. In practice, a major stumbling block to the use of higher X-ray energy has been the reduced quantum efficiency of silicon detectors as the X-ray energy increases, but hybrid photon-counting CdTe detectors are optimized for higher X-ray energies, and their performance has been steadily improving. Here the potential advantages of using higher incident beam energy together with a CdTe detector for MX are explored, with a particular focus on the advantages that higher beam energies may have for MX experiments with microbeams or microcrystals. Monte Carlo simulations are presented here which for the first time include the efficiency responses of some available X-ray detectors, as well as the possible escape of photoelectrons from the sample and their entry from surrounding material. The results reveal a `sweet spot' at an incident X-ray energy of 26 keV, and show a greater than factor of two improvement in diffraction efficiency at this energy when using microbeams and microcrystals of 5 µm or less.

Boron Nitride Nanotube Cyclotron Targets for Recoil Escape Production of Carbon-11

Boron nitride nanotubes (BNNTs) were investigated as a target media for cyclotron production of 11C for incident beam energy at or below 11 MeV. Both the 11B(p,n)11C and 14N(p,α)11C nuclear reactions were utilized. A sweep gas of nitrogen or helium was used to collect recoil escape atoms with a desired form of 11CO2. Three prototype targets were tested using an RDS-111 cyclotron. Target geometry and density were shown to impact the saturation yield of 11C and percent of yield recovered as carbon dioxide. Physical damage to the BNNT target media was observed at beam currents above 5 μA. Additional studies are needed to identify operating conditions suitable for commercial application of the method.

Analysis of complete, incomplete and total fusion data of 9Be +169Tm, 187Re, 209Bi reactions

We have analyzed the incomplete fusion (ICF), complete fusion (CF) and total fusion (TF) excitation functions for reactions induced by [Formula: see text] on [Formula: see text], [Formula: see text] and [Formula: see text] targets at near barrier energies using Wong’s formula in conjunction with the energy dependent Woods–Saxon potential. A phenomenological selection function is proposed to separate out the contribution of ICF and CF cross-sections in TF cross-section. The variation of relative contribution of ICF and CF in TF with respect to incident beam energy is very well reproduced through this approach.

PION PRODUCTION IN np COLLISIONS AT 1.25 GeV WITH HADES

Preliminary results on charged pion production in np collisions at an incident beam energy of 1.25 GeV obtained with HADES are presented. The np reactions were studied in dp collisions at 1.25 GeV/u using a Forward Wall hodoscope, aimed at registering spectator protons. The separation of np → ppπ-, np → npπ+π- and np → dπ+π- channels is demonstrated.

Determination of Selective Concentration Profile and Depth Resolved Partial Atomic Distributions for Multilayer Nanoheterostructures

A new method for studying multilayer structure using angle resolved XAFS measurements is proposed. The integral equation describing the relation between the fluorescence intensity for selective spectrum, the incident beam energy, the incident angle and a selective concentration profile, depth-dependent EXAFS has been derived. This integral Fredholm equation of the first kind belongs to the class of ill-posed problems and for the solution it needs special methods. We use the regularization Tikhonov method. The effectiveness of the proposed method was tested using the numerical simulations for trilayer system Cr-Fe-Cr. Some first experimental results for the thin films of pure Cr are also presented.

Absorption correction based on a three-dimensional model reconstruction from visual images

The results are presented of a feasibility study for the application of absorption corrections to macromolecular crystallographic X-ray diffraction data using a three-dimensional crystal model generated photographically. The model allows path lengths through the crystal, the solvent and the crystal mount system to be determined. The approach has been tested on the macromolecular crystallography beamline ID23-1 at the ESRF in Grenoble using a model insulin system with the standard mini diffractometer facilities, which incorporate high-quality camera systems for sample alignment. Data from the insulin crystal at low incident beam energy (6.0 keV or 2.1 Å) were recorded and processed using this approach. The resulting data are compared against those treated using an empirical method and show significant improvement. The methods described here are of general interest, particularly for long-wavelength X-ray work, and may also be applied to account for absorption effects in neutron crystallography.