Proton-Proton Bremsstrahlung at 61.7 MeV

The two final-state protons in the reaction $p+p\to p+p+\gamma$ at 61.7±0.1 MeV were detected by ($\Delta E, E$) telescopes placed at 30° on opposite sides of the beam. About 250 events were detected in a geometry with angular acceptance comparable to the maximum possible noncoplanarity. Additional data were obtained with apertures of smaller height, restricting the measurement to a more nearly coplanar geometry. The data indicate that the cross section is smaller for noncoplanar events. The estimated coplanar cross sections and differential cross section as a function of $\gamma$-ray angle are presented. The results agree with recent theoretical predictions.