Tuesday, 6 September 2005 - 3:20 PM

This presentation is part of: Astrophysics and Cosmochemistry

Cross-section measurements for Astrophysics with Recoil Mass Spectrometers and AMS – a comparison

Christof Vockenhuber for the DRAGON collaboration1, Hisham Nassar2, Michael Paul2, Walter Kutschera3, and Anton Wallner3. (1) TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada, (2) Racah Institute of Physics, Hebrew University, Jerusalem, 91904 , Israel, (3) Vienna Environmental Research Accelerator (VERA), Institut für Isotopenforschung und Kernphysik, Universität Wien, Währinger Str. 17, Wien, A-1090, Austria

The DRAGON (Detector of Recoils And Gamma-rays Of Nuclear reactions) recoil mass spectrometer [1] is located at the radioactive beam facility ISAC at Canada's National Laboratory for Particle and Nuclear Physics TRIUMF in Vancouver. It is designed to measure cross-sections of proton and alpha capture reactions of astrophysical importance. Both, stable (e.g. 12C, 40Ca) and short-lived (e.g. 21Na, 26Al) ion beams with energies of 0.15 to 1.5 MeV/nucleon have been used. The measurement is carried out in inverse kinematics which means the beam hits a window-less gas target (H2 or 4He) surrounded by a gamma detector array and the desired recoils are separated from the beam by a subsequent electromagnetic recoil mass spectrometer and finally identified in a focal plane detector.

The challenge is similar to AMS, picking out a few recoils from the ocean of beam particles. The astrophysical interesting reaction yields (recoils per incoming beam particle) are as low as 10-10 down to 10-15. The situation is even more complicated since beam and recoils have nearly the same momentum after the gas target. A series of electrostatic and magnetic bending elements provides suppression of the beam by many orders of magnitude. Measurements of energy, energy-loss and time-of-flight as well as gamma-recoil coincidences are used to identify recoils from leaky beam particles.

In this talk we present a comparison of cross-section measurements for Astrophysics with AMS and recoil mass spectrometers, with the 4He(40Ca,g)44Ti reaction as an example, which has been recently measured with AMS [2] and is now investigated with DRAGON in more detail.

[1] D.A. Hutcheon, S. Bishop, L. Buchmann, M.L. Chatterjee, A.A. Chen, J.M. D'Auria, S. Engel, D. Gigliotti, U. Greife, D. Hunter, A. Hussein, C. Jewett, N. Khan, A. Lamey, W. Liu, A. Olin, D. Ottewell, J.G. Rogers, G. Roy, H. Sprenger, C. Wrede, Nucl. Instrum. Meth. A 498 (2003) 190-210.

[2] H. Nassar, M. Paul, S. Ghelberg, A. Ofan, N. Trubmikov, Y. Ben-Dov, M. Hass, B.S. Nara Singh, Proceedings of Nuclei in Cosmos VIII (2004).


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