Bits and Pieces for the Nuclear Puzzle - Exploring light exotic nuclei with radioactive ion beams

Atomic nuclei are a fascinating case of many-body systems governed by quantum behaviour. This fact and the complex nuclear interaction are reasons why there is not yet a complete theory describing all atomic nuclei. Both experimental and theoretical efforts are needed to change this situation. Stable nuclei have been studied extensively, but more exotic nuclear systems are not yet well understood, and it is there where we expect to find improvements to our understanding of the complex nuclear interaction. Beams of light exotic nuclei have become accessible for experiments, and together with recent advances in detection systems, they open up possibilities for studying extreme nuclear systems up to and beyond the driplines, into the continuum. Experiments with light exotic beams deliver important data from extreme nuclear systems, which help to improve the description of atomic nuclei in general. This thesis is focused on light neutron-rich nuclei, and studies them in different ways. Proton-removal cross sections from boron and carbon isotopes are used to test the reaction model ABRABLA07. The agreement is surprisingly good, but the need for a better understanding of the induced excitation energy is demonstrated. Unbound nuclei beyond the dripline are produced via proton-knock-out reactions and studied. The data on the oxygen isotopes agree well with 3N-interaction shell-model calculations. The rare (β p) decay channel is observed in the halo nucleus 11Be. Nuclear reactions also play an important role in astrophysics and the question of how heavy elements are generated in our universe. Coulomb dissociation cross sections can be used to determine astrophysically important (n,γ) rates. Measured cross sections for 20N, 21N and 17C provide improved input for r-process network calculations

Coulomb dissociation of N 20,21

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at

Across the drip-line and back: examining 16B

Until today, after about one century of research, the atomic nucleus, a basic building block of nature, is still a fascinating puzzle. The field of nuclear physics strives for a better understanding employing both experimental and theoretical efforts. To gain further knowledge, nuclear physics experiments grow more and more sophisticated, pushing the limits of feasibility. Nuclei beyond the drip-lines are a target believed to supply information about the nuclear interaction which is not accessible otherwise.High-energy nuclear reactions are versatile tool to study nuclei at and beyond the drip-lines. One of the world-leading experimental-setups for high energy nuclear reactions is the LAND/R3B setup at GSI which offers excellent opportunities to study exotic nuclei close to and beyond the drip-lines. The present work centers around the study of the unbound nucleus 16B, analyzing an experiment performed at the LAND/R3B setup. 16B is the lightest unbound boron isotope, while heavier bound boron isotopes exist.It is studied by quasi-free scattering, produced by 17C undergoing a (p,2p) reaction, which is the production mechanism leaving the produced fragment least disturbed.The relative energy, transverse momentum distributions, and momentum profile of the 16B system are presented. At the current stage of analysis, relative energy and transverse momentum distributions are in agreement with previous measurements. A momentum profile has not been extracted before.Due to the nature of these experiments trying to push the frontier, developments of experimental techniques are an integral part of research. A significant share of this work is dedicated to developments, enabling or facilitating the analysis of the present and other experiments performed with the same setup

A characterisation of electronic properties of alkaline texturized polycrystalline silicon solar cells using IBIC

In this study, electronic properties of p-type alkaline texturized polycrystalline silicon solar cells were investigated using ion beam induced charge (IBIC) analysis. With this technique, quantitative information on electronic diffusion lengths and average electronic capture cross sections of lattice defects generated by high energy protons were obtained. Angular-resolved IBIC analysis was used to quantify the electronic diffusion lengths. For this purpose, the experimental data were fitted using a simulation based on the Ramo-Shockley-Gunn (RSG) theorem and the assumption of an abrupt pn-junction. In order to determine the average electronic capture cross section of proton-induced lattice defects, the loss of charge collection efficiency (CCE) was plotted vs. the accumulated ion fluence. As will be demonstrated, a simple model based on charge carrier diffusion and Shockley-Read-Hall (SRH) recombination is able to fit the CCE loss well. Furthermore, spatially and energetically highly resolved IBIC-maps of grain boundaries were recorded. A comparison with PIXE-maps shows that there is no correlation observable between CCE variations at grain boundaries and metallic impurities within the PIXE detection limits of a few ppm. On the contrary, there is an evident correlation to the morphology of the sample\u27s surface as was observed by comparing IBIC-maps and SEM-micrographs. These local CCE fluctuations are dominated by the interplay of charge carrier diffusion processes and the sample surface morphology

CALIFA, a Dedicated Calorimeter for the R3B/FAIR

The R3B experiment (Reactions with Relativistic Radioactive Beams) at FAIR (Facility for Antiproton and Ion Research) is a versatile setup dedicated to the study of reactions induced by high-energy radioactive beams. It will provide kinematically complete measurements with high efficiency, acceptance and resolution, making possible a broad physics program with rare-isotopes. CALIFA (CALorimeter for In-Flight detection of gamma-rays and high energy charged pArticles), is a complex detector based on scintillation crystals, that will surround the target of the R3B experiment. CALIFA will act as a total absorption gamma-calorimeter and spectrometer, as well as identifier of charged particles from target residues. This versatility is its most challenging requirement, demanding a huge dynamic range, to cover from low energy gamma-rays up to 300 MeV protons. This fact, along with the high-energy of the beams determine the conceptual design of the detector, presented in this paper, together with the technical solutions proposed for its construction

Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R3B/LAND setup with incident beam energies in the range of 300–450  MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type AO(p,2p)A−1N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry