190 research outputs found
Cross sections relevant to gamma-ray line emission in solar flares:He-induced reactions on O nuclei
Gamma-ray production cross sections have been measured for gamma-ray lines
copiously emitted in the He bombardment of O nuclei: the 937, 1042
and 1081 keV lines of F and the 1887 keV line of Ne. Four Ge
detectors with BGO shielding for Compton suppression were used to measure the
angular distributions of the gamma-rays. The excitation functions have been
obtained for He bombarding energies from 3.7 to 36 MeV. Total cross
sections are tabulated for calculations relevant to gamma-ray astronomy. The
importance of these lines as diagnosis for the presence and properties of
accelerated He in solar flares is discussed in light of the measured cross
sections.Comment: Phys. Rev. C68 (2003) 0258XX, in pres
A new experiment for the determination of the 18F(p,alpha) reaction rate at nova temperatures
The 18F(p,alpha) reaction was recognized as one of the most important for
gamma ray astronomy in novae as it governs the early 511 keV emission. However,
its rate remains largely uncertain at nova temperatures. A direct measurement
of the cross section over the full range of nova energies is impossible because
of its vanishing value at low energy and of the short 18F lifetime. Therefore,
in order to better constrain this reaction rate, we have performed an indirect
experiment taking advantage of the availability of a high purity and intense
radioactive 18F beam at the Louvain La Neuve RIB facility. We present here the
first results of the data analysis and discuss the consequences.Comment: Contribution to the Classical Novae Explosions conference, Sitges,
Spain, 20-24 May 2002, 5 pages, 3 figure
D(18F,pa)15N reaction applied to nova gamma-ray emission
The 18F(p,alpha)15O reaction is recognized to be one of the most important
reactions for nova gamma-ray astronomy as it governs the early E <= 511keV
gamma emission. However in the nova temperature regime, its rate remains
largely uncertain due to unknown low-energy resonance strengths. We report here
the measurement of the D(18F,p)19F(alpha)15N one-nucleon transfer reaction,
induced by a 14 MeV 18F radioactive beam impinging on a CD2 target; outgoing
protons and 15N (or alpha-particles) were detected in coincidence in two
silicon strip detectors. A DWBA analysis of the data resulted in new limits to
the contribution of low-energy resonances to the rate of the 18F(p,alpha)15O
reaction.Comment: Rapid Communication to appear in Phys. Rev. C., 4 pages and 4 figure
- …