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We have measured at GSI-Darmstadt (Germany) the reactions 136 Xe + p and 136 Xe +12 C, using the inverse-kinematics technique at 1 A.GeV and the large acceptance SPALADiN setup. The combination of both provides a very good coverage of the phase-space of the excited system decay channels, allowing the study of the relative importance of those decay channels, as well as a very efficient filter to reject from the detection the particles and nuclear fragments of high energy in the projectile centre-of-mass frame, essentially produced in the first-instant nucleon-nucleon collisions, prior to the decay of the excited nuclear system. Our analysis in the two-step scenario permits one to estimate on an event basis E*/A, the excitation energy per nucleon of the decaying nuclear system, and to study the E*/A dependence of the different decay channels. The E*/A range of overlap of the 136 Xe + p and 136Xe+12 C reactions is large and allows for an extensive comparison between both reactions, and therefore provides a strong test bench of the entrance-channel-independence hypothesis of the excited-system decay. We address the two-step-scenario assumption in the light of our data and their comparison with different up-to-date models.

The SEPAGE spectrometer (Spectrometre Electrons Protons A Grandes Energies) was realized within the PETAL+ project funded by the French ANR (French National Agency for Research). This plasma diagnostic, installed on the LMJ-PETAL laser facility, is dedicated to the measurement of charged particle energy spectra generated by experiments using PETAL (PETawatt Aquitaine Laser). SEPAGE is inserted inside the 10-meter diameter LMJ experimental chamber with a SID (Diagnostic Insertion System) in order to be close enough to the target. It is composed of two Thomson Parabola measuring ion spectra and more particularly proton spectra ranging from 0.1 to 20 MeV and from 8 to 200 MeV for the low and high energy channels respectively. The electron spectrum is also measured with an energy range between 0.1 and 150 MeV. The front part of the diagnostic carries a film stack that can be placed as close as 100 mm from the target center chamber. This stack allows a spatial and spectral characterization of the entire proton beam. It can also be used to realize proton radiographies.