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تسجيل مستخدم جديد$^8$He nuclei stopped in nuclear track emulsion
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The fragment separator ACCULINNA in the G. N. Flerov Laboratory of Nuclear Reactions of JINR was used to expose a nuclear track emulsion to a beam of radioactive $^{8}$He nuclei of energy of 60 MeV and enrichment of about 80%. Measurements of decays of $^{8}$He nuclei stopped in the emulsion allow one to evaluate possibilities of $alpha$-spectrometry and to observe a thermal drift of $^{8}$He atoms in matter. Knowledge of the energy and emission angles of $alpha$-particles allows one to derive the energy distribution of $alpha$-decays Q$_{2alpha}$. The presence of a tail of large values Q$_{2alpha}$ is established. The physical reason for the appearance of this tail in the distribution Q$_{2alpha}$ is not clear. Its shape could allow one to verify calculations of spatial structure of nucleon ensembles emerging as $alpha$-pairs of decays via the state $^8$Be$_{2+}$.
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Nuclear track emulsion is exposed to a beam of radioactive $^8$He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the $^8$He nuclei stopped in the emulsion allow the potential of t
he $alpha$ spectrometry to be estimated and the thermal drift of $^8$He atoms in matter to be observed for the first time.
The technique of nuclear track emulsions is used to explore the fragmentation of light relativistic nuclei down to the most peripheral interactions - nuclear white stars. A complete pattern of therelativistic dissociation of a $^8$B nucleus with targ
et fragment accompaniment is presented. Relativistic dissociation $^{9}$Be$to2alpha$ is explored using significant statistics and a relative contribution of $^{8}$Be decays from 0$^+$ and 2$^+$ states is established. Target fragment accompaniments are shown for relativistic fragmentation $^{14}$N$to$3He+H and $^{22}$Ne$to$5He. The leading role of the electromagnetic dissociation on heavy nuclei with respect to break-ups on target protons is demonstrated in all these cases. It is possible to conclude that the peripheral dissociation of relativistic nuclei in nuclear track emulsion is a unique tool to study many-body systems composed of lightest nuclei and nucleons in the energy scale relevant for nuclear astrophysics.
Possibilities of the nuclear emulsion technique for the study of the systems of several relativistic fragments produced in the peripheral interactions of relativistic nuclei are discussed. The interactions of the $^{10}$B and $^{9}$Be nuclei in emuls
ion are taken as an example to show the manifestation of the cluster degrees of freedom in relativistic fragmentation. For the case of the relativistic $^{9}$Be nucleus dissociation it is shown that exact angular measurements play a crucial role in the restoration of the excitation spectrum of the alpha particle fragments. The energy calibration of the angular measurements by the $^{9}$Be nucleus enables one to conclude reliably about the features of internal velocity distributions in more complicated systems of relativistic $alpha$ particles.
The results of investigations dealing with the charge topology of the fragments produced in peripheral dissociation of relativistic $^8$B nuclei in emulsion are presented. 55 events of peripheral dissociation of the $^8$B nucleus were selected from t
he events which do not involve the production of the target-nucleus fragments and mesons (`` whiterqrq ~stars). A leading contribution of the $^8$B$to^7$Be+p mode having the lowest energy threshold was revealed on the basis of those events. Information on the relative probability of dissociation modes with a larger multiplicity was obtained. The dissociation of a $^7$Be core in $^8$B indicates an analogy with that of the free $^7$Be nucleus.par The transverse momentum distributions of the fragments from the $^8$B$to^7$Be+p dissociation mode were obtained. Their small average value, $<$P$_t>$= 52 MeV/c, in the c.m.s. suggests a low binding energy of the external proton in the $^8$B nucleus. An indication for a strong azimuthal correlation of the $^7$Be and p fragments was got.
A role of the unstable nuclei ${}^{6}$Be, ${}^{8}$Be and ${}^{9}$B in the dissociation of relativistic nuclei ${}^{7,9}$Be, ${}^{10}$B and ${}^{10,11}$C is under study on the basis of nuclear track emulsion exposed to secondary beams of the JINR Nucl
otron. Contribution of the configuration ${}^{6}$Be + $mit{n}$ to the ${}^{7}$Be nucleus structure is 8 $pm$ 1% which is near the value for the configuration ${}^{6}$Li + $mit{p}$. Distributions over the opening angle of $alpha$-particle pairs indicate to a simultaneous presence of virtual ${}^{8}$Be$_{g.s.}$ and ${}^{8}$Be$_{2^+}$ states in the ground states of the ${}^{9}$Be and ${}^{10}$C nuclei. The core ${}^{9}$B is manifested in the {${}^{10}$C} nucleus with a probability of 30 $pm$ 4%. Selection of the ${}^{10}$C white stars accompanied by ${}^{8}$Be$_{g.s.}$ (${}^{9}$B) leads to appearance in the excitation energy distribution of 2$alpha$2$mit{p}$ quartets of the distinct peak with a maximum at 4.1 $pm$ 0.3 MeV. ${}^{8}$Be$_{g.s.}$ decays are presented in 24 $pm$ 7% of 2He + 2H events of the ${}^{11}$C coherent dissociation and 27 $pm$ 11% of the 3He ones. The channel ${}^{9}$B + H amounts 14 $pm$ 3%. The ${}^{8}$Be$_{g.s.}$ nucleus is manifested in the coherent dissociation ${}^{10}$B $to$ 2He + H with a probability of 25 $pm$ 5% including 14 $pm$ 3% of ${}^{9}$B decays. A probability ratio of the mirror channels ${}^{9}$B + $mit{n}$ and ${}^{9}$Be + $mit{p}$ is estimated to be 6 $pm$ 1.
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