双束对射激光驱动超薄靶的超短脉冲中子源

Ultrashort pulsed neutron source driven by two counterpropagating laser pulses interacting with ultra-thin foil

使用粒子模拟程序和蒙特卡罗方法研究了双束对射圆极化激光与超薄氘靶相互作用中氘氘聚变反应产生中子的过程.研究发现,由于净光压和横向不稳定性发展的差异,激光电场矢量旋转方向和初始相对相位差对氘靶压缩及中子特性有重要影响.选择相对相位差为0且电场矢量旋转方向相同的双束光,可获得最高的中子产额;而采用相对相位差为0.5π或1.5π且电场矢量旋转方向不同的对射光,中子具有定向的空间分布.对于强度为1.23×10^(21)W/cm^(2)、脉宽为33 fs、相对相位差为0.5π的左旋光和右旋光,可获得产额为8.5×10^(4)n、强度为1.2×10^(19)n/s、脉宽为23 fs、前冲性较好且分布可调谐的脉冲中子源.

Neutron production via D(d,n)^(3)He nuclear reaction during the interaction of two counter-propagating circularly polarized laser pulses with ultra-thin deuterium target is investigated by particle-in-cell simulation and Monte Carlo method.It is found that the rotation direction and initial relative phase difference of laser electric field vector have important effects on deuterium foil compression and neutron characteristics.The reason is attributed to the net light pressure and the difference in transverse instability development.The highest neutron yield can be obtained by choosing two laser pulses with a relative phase difference of 0 and the same rotation direction of the electric field vector.When the relative phase difference is 0.5πor 1.5πand the rotation direction of electric field vector is different,the neutrons have a directional spatial distribution and the neutron yield only slightly decreases.For left-handed circularly polarized laser pulse and right-handed circularly polarized laser pulse,each with an intensity of 1.23×10^(21)W/cm^(2),a pulse width of 33 fs and a relative phase difference of 0.5π,it is possible to produce a pulsed neutron source with a yield of 8.5×10^(4)n,production rate of 1.2×10^(19)n/s,pulse width of 23 fs and good forward direction as well as tunable spatial distribution.Comparing with photonuclear neutron source and beam target neutron source driven by ultraintense laser pulses,the duration of neutron source in our scheme decreases significantly,thereby possessing many potential applications such as neutron nuclear data measurement.Our scheme offers a possible method to obtain a compact neutron source with short pulse width,high production rate and good forward direction.