In the environment of a hot plasma, as achieved in stellar explosions, capture and photodisintegration reactions proceeding on excited states in the nucleus can considerably contribute to the astrophysical reaction rate. Usually, such reaction rates including the excited-state contribution are obtained from theoretical calculations as the direct experimental determination of these astrophysical rates is currently unfeasible. Future experiments could provide constraining information on the current reaction models which would improve the predictive power of the theoretical reaction rates. In the present study, experiments of photodisintegration with charged-particle emission leading to specific excited states in the residual nucleus are proposed. The expected experimental results can be used to determine the particle-transmission coefficients in the model calculations of photodisintegration and capture reactions. With such constrained transmission coefficients, the astrophysical reaction rates especially involving the excited-state contributions can be better predicted and implemented in astrophysical simulations. In particular, ($\gamma ,p$) and ($\gamma ,\alpha$) reactions in the mass and energy range relevant to the astrophysical $p$ process are considered and the feasibility of measuring them with the ELISSA detector system at the future Variable Energy $\gamma$-ray (VEGA) facility at Extreme Light Infrastructure–Nuclear Physics is investigated. To this end, in a first step 17 reactions with proton emission and 17 reactions with $\alpha$ emission are selected and the dependence of calculated partial cross sections on the variation of nuclear property input is tested. The simulation results reveal that, for the ($\gamma ,p$) reaction on 12 targets of ${}^{29}\mathrm{Si}$, ${}^{56}\mathrm{Fe},{}^{74}\mathrm{Se},{}^{84}\mathrm{Sr},{}^{91}\mathrm{Zr},{}^{96,98}\mathrm{Ru},{}^{102}\mathrm{Pd},{}^{106}\mathrm{Cd}$, and ${}^{115,117,119}\mathrm{Sn}$, and the ($\gamma ,\alpha$) reaction on five targets of ${}^{50}\mathrm{V},{}^{87}\mathrm{Sr},{}^{123,125}\mathrm{Te}$, and ${}^{149}\mathrm{Sm}$, the yields of the reaction channels with the transitions to the excited states in the residual nucleus, namely ($\gamma ,X_i$) with $i\ne 0$, are relevant and even dominant. Therefore, these 17 reactions are considered in the further feasibility study. For each of the 17 photon-induced reactions, in order to attain the detectable limit of 100 counts per day for the total proton or $\alpha$-particle yields, the minimum required $\gamma$-beam energies $E_{\mathrm{low}}$ for the measurements are estimated. It is further found that for each considered reaction, the total yields of the charged-particle $X$ may be dominantly contributed from one, two, or three ($\gamma ,X_i$) channels within a specific, narrow energy range of the incident $\gamma$ beam. If the actual measurements of these photon-induced reactions are performed in this energy range, the sum of the yields of the dominant ($\gamma ,X_i$) channels can be approximated by the measured yields of the charged particle $X$ within acceptable uncertainty. This allows to experimentally obtain the yields of the ($\gamma ,X_i$) channels which dominantly contribute to the total yields of $X$. Using the simulated yields, these energy ranges for each of the 17 photon-induced reactions are derived. Furthermore, the energy spectra of the ($\gamma ,X_i$) channels with $0\le i\le 10$ are simulated for each considered reaction, with the incident $\gamma$-beam energies in the respective energy range as derived before. Based on the energy spectra, the identification of the individual dominant ($\gamma ,X_i$) channels is discussed. It becomes evident that measurements of the photon-induced reactions with charged-particle emissions considered in this work are feasible with the VEGA+ELISSA system and will provide knowledge useful for nuclear astrophysics.

The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics. For this purpose, a silicon strip detector array (named ELISSA) will be realized in a common effort by ELI-NP and INFN-LNS (Catania, Italy), in order to measure excitation functions and angular distributions over a wide energy and angular range. A prototype of ELISSA was built and tested at Laboratori Nazionali del Sud (INFN-LNS) in Catania with the support of ELI-NP. On this occasion, we carried out experiments with alpha sources and with a 11 MeV ⁷Li beam. Thanks to our approach, the first results of those tests show up a very good energy resolution (better than 1%) and very good position resolution, of the order of 1 mm. Below 1 MeV, a resolution of the order of 6 mm is found, still good enough for the measurement of angular distribution and the kinematical identification of the reactions induced on the target by gamma beams.