The next generation of 4π detector arrays for heavy ion studies will largely use Pulse Shape Analysis to push the performance of silicon detectors with respect to ion identification. Energy ...resolution and pulse shape identification capabilities of silicon detectors under prolonged irradiation by energetic heavy ions have thus become a major issue. In this framework, we have studied the effects of irradiation by energetic heavy ions on the response of neutron transmutation doped (nTD) silicon detectors. Sizeable effects on the amplitude and the risetime of the charge signal have been found for detectors irradiated with large fluences of stopped heavy ions, while much weaker effects were observed by punching-through ions. The robustness of ion identification based on digital pulse shape techniques has been evaluated.
In equation (1) of this Letter, the closing bracket was missing; in Extended Data Fig. 1 and the accompanying legend, 'Φ(p
)' should have been 'Φ
(p
)', and in the Methods the text "Odd J assignments ...are uncertain by ±1." has been added. These errors have all been corrected online.
Carbon burning powers scenarios that influence the fate of stars, such as the late evolutionary stages of massive stars
(exceeding eight solar masses) and superbursts from accreting neutron stars
. ...It proceeds through the
C +
C fusion reactions that produce an alpha particle and neon-20 or a proton and sodium-23-that is,
C(
C, α)
Ne and
C(
C, p)
Na-at temperatures greater than 0.4 × 10
kelvin, corresponding to astrophysical energies exceeding a megaelectronvolt, at which such nuclear reactions are more likely to occur in stars. The cross-sections
for those carbon fusion reactions (probabilities that are required to calculate the rate of the reactions) have hitherto not been measured at the Gamow peaks
below 2 megaelectronvolts because of exponential suppression arising from the Coulomb barrier. The reference rate
at temperatures below 1.2 × 10
kelvin relies on extrapolations that ignore the effects of possible low-lying resonances. Here we report the measurement of the
C(
C, α
)
Ne and
C(
C, p
)
Na reaction rates (where the subscripts 0 and 1 stand for the ground and first excited states of
Ne and
Na, respectively) at centre-of-mass energies from 2.7 to 0.8 megaelectronvolts using the Trojan Horse method
and the deuteron in
N. The cross-sections deduced exhibit several resonances that are responsible for very large increases of the reaction rate at relevant temperatures. In particular, around 5 × 10
kelvin, the reaction rate is boosted to more than 25 times larger than the reference value
. This finding may have implications such as lowering the temperatures and densities
required for the ignition of carbon burning in massive stars and decreasing the superburst ignition depth in accreting neutron stars to reconcile observations with theoretical models
.
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