where θ 0 is the initial flip angle. Then, for ratios γ 2 γ ∞ rd = 1 + ϵ larger but close to unity, and for flip angles close to π, θ 0 = π -h so that cos θ 0 = -cos h = 1 -h 2 2 to first order, one sees that the ratio of Equation 13 can be made arbitrarily small, meaning that γ rd ≪ γ ∞ rd . This is illustrated in Figure11 This allows to explain why, even for very broad lines such as the ones in our experiments (∼ 25 kHz), for extremely small flip angles (and low rf power on the order of the mW that excite only a small fraction of the NMR line) and a radiation damping rate that is almost equal to the line width, maser bursts lasting tens of ms are observed. In fact, this situation was met experimentally when monitoring the polarization buildup with small pulses that trigger the DNP-NMR maser when the growing magnetization approaches the condition γ 2 ≈ γ rd .