We report on the measurement of the \(^{7}\)Be(\(n, p\))\(^{7}\)Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF ...facility at CERN. This reaction plays a key role in the lithium yield of the Big Bang Nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and showed a large discrepancy between each other. The measurement was performed with a Si-telescope, and a high-purity sample produced by implantation of a \(^{7}\)Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low-energy, relative to current evaluations, in the region of BBN interest the present results are consistent with the values inferred from the time-reversal \(^{7}\)Li(\(p, n\))\(^{7}\)Be reaction, thus yielding only a relatively minor improvement on the so-called Cosmological Lithium Problem (CLiP). The relevance of these results on the near-threshold neutron production in the p+\(^{7}\)Li reaction is also discussed.
We report on the measurement of the \(^{7}\)Be(\(n, p\))\(^{7}\)Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the ...n\_TOF facility at CERN. This reaction plays a key role in the lithium yield of the Big Bang Nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and showed a large discrepancy between each other. The measurement was performed with a Si-telescope, and a high-purity sample produced by implantation of a \(^{7}\)Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low-energy, relative to current evaluations, in the region of BBN interest the present results are consistent with the values inferred from the time-reversal \(^{7}\)Li(\(p, n\))\(^{7}\)Be reaction, thus yielding only a relatively minor improvement on the so-called Cosmological Lithium Problem (CLiP). The relevance of these results on the near-threshold neutron production in the p+\(^{7}\)Li reaction is also discussed.
A controlled and precise determination of the cross-sections of the fusion
reactions 7Be(p,gamma)8B and 3He(4He,gamma)7Be, which play an important role in
determining the solar neutrino flux, ...necessitates the knowledge of a precise
value of the electron-capture half-life of 7Be. This half-life may depend on
the material hosting the 7Be atoms via small modifications of the electron
density around the 7Be nucleus. In this brief communication we report on the
measurement of 7Be implanted in four materials: copper, aluminum, sapphire and
PVC. The four results are consistent with a null host dependence within two
standard deviations and their weighted average of 53.236(39)d agrees very well
with the adopted value in the literature, 53.22(6)d. The present results may
exhibit a slight (0.22%) increase of the half-life at room temperature for
metals compared to insulators that requires further studies.
A controlled and precise determination of the cross-sections of the fusion reactions 7Be(p,gamma)8B and 3He(4He,gamma)7Be, which play an important role in determining the solar neutrino flux, ...necessitates the knowledge of a precise value of the electron-capture half-life of 7Be. This half-life may depend on the material hosting the 7Be atoms via small modifications of the electron density around the 7Be nucleus. In this brief communication we report on the measurement of 7Be implanted in four materials: copper, aluminum, sapphire and PVC. The four results are consistent with a null host dependence within two standard deviations and their weighted average of 53.236(39)d agrees very well with the adopted value in the literature, 53.22(6)d. The present results may exhibit a slight (0.22%) increase of the half-life at room temperature for metals compared to insulators that requires further studies.
Six cylindrical lead bismuth eutectic (LBE) targets having fixed diameter of 6 mm and varying lengths of 8–50 mm were irradiated with a 1.4 GeV proton beam at CERN-ISOLDE. Both short-lived (
5
h
<
T
...1
/
2
<
5
days
) and long-lived (
T
1
/
2
>
5
days
) radionuclides were identified by off-line
γ
-spectrometry and their activities at the end of bombardment (EOB) were determined. Total 80
γ
-emitting radionuclides, ranging from
7
Be
to
209
At
, were identified in the 50 mm long LBE target. The yields of all the radioisotopes were compared with the Monte Carlo Code FLUKA. The spallation reaction was the dominant mode whereas fission induced reactions had no significant contribution. The high energy proton irradiated LBE target may act as a large source of several clinically important and other exotic radionuclides.
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