Investigation of Proton Beam-Driven Fusion Reactions Generated by an Ultra-Short Petawatt-Scale Laser Pulse

Figure 4

Postshot gamma spectroscopy of the pitcher-catcher shots. A strong peak at 511 keV is measured, verifying the existence of positron emitters (in contrast to, e.g., excited nuclei from photoexcitation). The second peak at about 250 keV is from backscattered 511 keV primary photons in the lead shielding nearby. The photograph in the inset shows one of the detectors inside of the lead housing with the top removed.