Date of Award
Doctor of Philosophy
Dr. Alan H. Wuosmaa
The Helical Orbit Spectrometer (HELIOS) at Argonne National Laboratory is the first implementation of a radical new concept for measuring nuclear reactions. Direct nuclear transfer reactions are powerful tools for studying the properties of the atomic nucleus. A traditional example is the neutron-transfer reaction (d ,p), wherein an accelerated beam of deuterons d bombards a heavy target. The incoming deuteron transfers a neutron to the target nucleus and the outgoing proton p is detected to study the properties of the residual heavy nucleus. A new frontier of nuclear reaction studies involving short-lived exotic nuclei—which are unsuitable for use as targets—is being made available through the development of radioactive ion beam facilities.
In measurements made with radioactive beams, the role of the beam and target are reversed, with a heavyion beam bombarding a light target. In this regime of “inverse kinematics,” the center-of-mass system has a substantial velocity in the laboratory frame, the consequence of which is that the energy of the emitted light ion is highly angle-dependent. A successful measurement made in inverse kinematics thus requires a detector system with excellent resolution. HELIOS is a new approach to detecting the charged light ion reaction products which addresses the technical challenges of studying reactions in inverse kinematics.
The HELIOS spectrometer is based on a large-bore superconducting solenoid which uses a slender position- sensitive detector array to measure the energy and position of charged particles along the solenoid axis. This dissertation describes the advantages of the HELIOS concept as they relate to measurements made in inverse kinematics. The technical specifications of the spectrometer are described in detail. Three reaction measurements are discussed: the measurement used to commission HELIOS, the 28Si(d ,p)29Si reaction; the first experimental results from HELIOS, the 12B(d ,p)13B measurement; and an important measurement which is planned to be made with HELIOS, the 132Sn(d ,p)133Sn reaction. Each of these measurements is compared to past measurements made with other detector systems.
Lighthall, Jonathan C., "Commissioning of the Helical Orbit Spectrometer: A New Device for Measuring Nuclear Reactions in Inverse Kinematics" (2011). Dissertations. 432.