超强短脉冲激光辐照电容线圈靶产生强磁场机理研究

Strong, shaped magnetic fields could be produced by laser irradiating capacitor-coil target. It offers a new experimental test bed to study atomic and molecular physics, astrophysics, inertial confinement fusion, etc. Nanosecond laser is usually used to produce magnetic field in this method, and the produced magnetic field has a strong relation to the electron energy. The temperature of electrons produced by ultraintense laser is much higher than that by nanosecond laser. Thus the magnetic field may be stronger when ultraintense laser is used. In our previous work, we propose to use ultraintense femtosecond laser pulse to produce the controllable magnetic field. And a phenomenological model based on ultraintense laser interaction with capacitor-coil target has been established. In our project, the major mechanisms to produce controllable magnetic field by ultraintense laser should be found out. Topics to be addressed include: (1) develop the method to produce magnetic field by ultraintense laser, and demonstrate experiments with different laser parameters; (2) study the mechanism for strong magnetic field production, and establish the methods to produce pulsed magnetic field by ultraintense laser. The requirements of laser parameters are expected to be released by our work, and it potentially opens new frontiers in basic physics which require strong magnetic field environments.

激光辐照电容线圈靶产生的磁场具有磁场强度高、形状可控等优点，在原子分子物理、天体物理、惯性约束聚变等研究领域均具有重要应用。该方法产生的磁场强度和热电子束能量密切相关，目前多使用纳秒激光作为驱动源；由于超强激光产生的超热电子能谱温度远高于纳秒激光情况，因而可能更有利于磁场的产生。基于上述想法，在本项目的前期工作中，创新性地利用具有相对论强度的飞秒激光来产生可控脉冲强磁场，并初步提出了一种超强激光辐照电容线圈靶产生磁场模型。本项目将在上述研究的基础上，拟解决激光辐照电容线圈靶驱动可控脉冲强磁场形成机理中的难点问题。内容包括：发展超强激光产生脉冲强磁场的新方法，开展不同激光参数下超强激光产生强磁场实验；研究强磁场产生机理，并建立超强激光辐照电容线圈靶产生磁场实验方法。本研究将放宽实验室脉冲强磁场产生对激光器的要求，对推动实验室强磁场相关研究领域的发展具有重要意义。

激光辐照电容线圈靶产生的强磁场具有磁场强度高、形状可控等优点，在原子分子物理、天体物理、惯性约束聚变等研究领域均具有重要应用。该方法产生的磁场强度和热电子束能量密切相关，目前多使用纳秒激光作为驱动源；由于超强激光产生的超热电子能谱温度远高于纳秒激光情况，因而可能更有利于磁场的产生。基于上述想法，在本项目的前期工作中，创新性地利用具有相对论强度的飞秒激光来产生可控脉冲强磁场，并初步提出了一种超强激光辐照电容线圈靶产生磁场模型。.本项目在上述研究的基础上，分析了超强激光产生磁场理论模型中各参数对磁场产生的影响,通过实验磁场弛豫过程可对线圈电阻值进行较精确测量。项目开展了超强激光辐照电容线圈靶实验，利用25J~130J皮秒激光获得了超过100T以上脉冲强磁场。通过质子照相诊断观察到磁场偏转质子形成空泡结构，空泡轮廓形状和位置均和仅含线圈磁场的粒子跟踪模拟结果一致，由此确认质子空泡来自线圈磁场并由此给出磁场强度信息。实验在不同激光能量和时序下获得的磁场数据，均能与相应条件下的理论模型曲线相符，在更大激光能量范围内验证了磁场产生理论模型。实验结果说明该模型可以通过激光和靶参数对磁场进行预期，建立起适用于10J~100J超强激光的可控脉冲强磁场实验平台。项目结果有利于推动强磁场环境下的激光等离子体相互作用相关领域研究。