NUCLEARASTROPHYSICSMEASUREMENTS WITHRADIOACTIVEBEAMS

Abstract

s Abstract Radioactive nuclei play an important role in a diverse range of astrophysical phenomena including the early universe, the sun, red giant stars, nova explosions, X-ray bursts, supernova explosions, and supermassive stars. Measurements of reactions with beams of short-lived radioactive nuclei can, for the first time, probe the nuclear reactions occurring in these cosmic phenomena. This article describes the astrophysical motivation for experiments with radioactive beams, the techniques to produce these beams and perform astrophysically relevant measurements, results from recent experiments, and plans for future facilities.

Recent astrophysical studies with exotic beams at ORNL

“…Spectroscopic factors have been extracted by comparing the measured angular distribu- tions with calculations using TWOFNR. The results are shown in table 1. The values of the spectroscopic factors all agree well with those from the work of refs.…”

“…Nuclear data is also an important ingredient in the interpretation of new observations made by ground-based observatories such as the Keck and European Southern Observatory (ESO) Very Large Telescopes, by space-borne observatories such as the Hubble Space Telescope and the Chandra X-Ray Observatory, and by large subterranean detectors such as the Sudbury Neutrino Observatory and Super-Kamiokande. More complete and precise nuclear physics measurements are therefore needed to improve astrophysical models and to decipher the latest observations [1].…”

Astrophysics experiments with radioactive beams at ATLAS

“…The in-flight technique, first proposed about 30 years ago, 8 makes use of simple one-or two-nucleon transfer reactions such as (p,n), (d,n), (d,p), (d, 3 He), or ( 3 He,n) in order to produce the radioactive nuclei of interest. These reactions are performed in inverse kinematics i.e., by bombarding a gas cell filled with hydrogen or helium with heavy-ion beams.…”

“…14 Since then, making use of the high-intensity (∼100 pnA) beams of stable isotopes from ATLAS and a cryogenically-cooled gas target filled with 1, 2 H or 3,4 He, about 25 different radioactive beams have been produced at ATLAS and used in experiments. A general description of the method has been presented in Ref.…”

“…At the Argonne Tandem Linac Accelerator System (ATLAS) astrophysics experiments with radioactive beams have been performed for about two decades starting with a 18 F beam for a measurement of the 18 F(p,α) 15 O reaction. 4 The first beams were produced with the 'two-accelerator method' 3 and were limited to isotopes with longer half-lives. [4][5][6] The in-flight method on the other hand, gave us access to more than 100 short-lived isotopes in the mass range up to A∼60.…”