Improved time-of-flight (ToF) capability has been added to the University of Michigan (UM)University of Notre Dame (UND) TwinSol low-energy dual 6T solenoid-based radioactive nuclear-beam (RNB) facility at the UND FN tandem Van de Graaff accelerator. An extended low-background beam line has been combined with a newly-constructed ca.1 meter diameter ISO-250 based scattering chamber capable of sub-ns ToF of RNBs. These together with the intrinsic, low ToF spread in the TwinSol ion-optical system yields improved ToF information for low-energy RNB nuclear reaction studies. Using either the intrinsic accelerator bunched and pulsed-selected beams with RF timing, or with the addition of an MCPfoil timing system (or similar) detector at the dual-solenoid cross-over region allows for reduction of the energy spread inherent in these low-energy RNB reactions. As an example, using the ToF information reduces the FWHM energy spread in a high-intensity 28 MeV 8Li beam from about 1 MeV to <ca. 600 keV or more without excessive collimation (which reduces the beam). This has been utilized in a recent experiment measuring the Coulomb excitation of a short-lived 8Li RNB on gold targets. The use of ToF permitted a much more efficient measurement of this reaction as certain background measurements were no longer needed and the full 8Li beam intensity could be utilized. A number of other improvements are planned to further improve the ToF resolution and count-rate limits of the various ToF systems and we hope to utilize these in the future.
|Original language||English (US)|
|Number of pages||5|
|Journal||Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|State||Published - Oct 1 2011|
Bibliographical noteFunding Information:
We thank the UND operating staff and in particular acknowledge the assistance provided by the late Dr. L. Lamm. This work was supported by the U.S. National Science Foundation under contracts PHY-0652591 and PHY-0758100 .
- Coulomb excitation
- Exotic beams
- Ion-beam time of flight
- Radioactive beams