Dense γ−rays emission in two consecutive pulses irradiating near critical density plasma

We report the overdense electron acceleration and dense gamma ray emission via the use of two continuous laser pulses irradiating near critical density plasma. Thanks to the ion channel formed behind the first laser pulse, the leading laser beam is well focused to a higher intensity. As a result, the noticeable electron re-injection and ion focusing when one laser incident is significantly suppressed in the two-consecutive- lasers scheme, efficiently improved the electron acceleration process. Moreover, owing to the stronger laser field and the higher electron energy, the probability rate of the accelerated electron emitting γ-rays is considerably enhanced. In this regime, the laser intensity is reduced from $1\times 10^{23}$ to $4\times 10^{22}$ W cm−2 with the competitive density of generated gamma rays.