Fig. 1. (a) Sketch of the detector setup. (b) Raw scintillation signal image recorded by the camera. (c) Experimental setup around the vacuum chamber.

Fig. 2. Three-dimensional view of the simulation setup rendered by the Flair code, showing a flange with a chamber wall, a magnet and a scintillator stack. The light-proof box is not shown in the figure.

Fig. 3. Examples of the signal unfolding for the forward and top scintillator stack detectors for the same shot. The signals are scaled by the same arbitrary value.

Fig. 4. Unfolded temperatures of the high-energy component of the bremsstrahlung radiation depending on the OAP shift (laser defocusing). The data were obtained as averages from the series of shots per given OAP shift, with the error bars represented by their standard deviation. The green curve represents theoretical predictions for the hot electron temperatures according to Beg’s scaling law, based on the laser intensities corresponding to each OAP shift. The ponderomotive law is out of scale for the given intensities.

Fig. 5. Ratios of the relative amplitudes of the high-energy and low-energy bremsstrahlung radiation components resulting from the unfolding procedure. The data were obtained as averages from the series of shots per given OAP shift, with the error bars calculated through error propagation techniques.

Fig. 6. Comparison of proton cutoff energy with total scintillation light yield of the EMC detectors (a) and unfolded ‘hot’ temperatures (b). The data were obtained as averages from the series of shots per given OAP shift, with the error bars represented by their standard deviation.

Fig. 7. Ratios between the proton cutoff energy and the bremsstrahlung radiation temperature for different laser defocusing for the forward and top EMC detectors. The data were obtained as averages from the series of shots per given OAP shift, with the error bars calculated through error propagation techniques.

Fig. 8. Shot-to-shot fluctuations of the photon flux measured by independent X-ray detectors.