| In the cosmic environment,the magnetic field is a universal form of matter.It interacts with the plasma（such as stars,nebulae,interstellar media,accretion disks and jets）which widely exist in the space,and produces abundant cosmic magnetohydrodynamic phenomena.From geophysics to solar physics,from extragalactic galaxies to interstellar space,the exploration of astronomical phenomena has inspired the development and improvement of MHD.Laboratory astrophysics enables people to produce extreme phenomena under the condition of high energy density in the laboratory environment,which is used to simulate astronomical phenomena in space,especially for astronomical phenomena beyond the astronomical observation limit.On the other hand,the plasma can be fully diagnosed,especially the plasma magnetic field configuration and electron density.This method provides an important way to verify the theory of celestial body evolution described by magnetohydrodynamics or hydrodynamics,and also corrects our understanding of astronomical phenomena.In recent years,the magnetized jet system is a typical object of cosmic magnetohydrodynamics.The emission,collimation and propagation of the jet can vividly show the influence of the magnetic field on the plasma motion.In this paper,a series of typical magnetized jet experiments are presented to demonstrate the acceleration mechanism of the plasma jet under the magnetic pinch force in the emission region.We find that:（1）this kind of acceleration mechanism is more significant for the jets of non relativistic protostars（YSO）,but less relevant to the jets of highly collimated relativistic active nuclei（AGN）;（2）The collimating effect of magnetic field on the plasma outflow is focused on two aspects:the magnetic freezing effect in the annular field and the conical convergent flow in the axial field.The magnetic freezing effect is effective for the YSO jet with a certain temperature.For the AGN jet,it mainly acts on the baryon plasma with a certain temperature in the outer layer of the jet.The axial field collimation mechanism is effective for both YSO and AGN.The strong magnetic field generated in the laboratory provides an experimental platform for the study of plasma physics,beam physics,astrophysics,material physics,and atomic and molecular physics.The technology of high magnetic field generated by the interaction between laser and capacitor coil target is becoming more and more mature.A typical application of this method in laboratory astrophysics research is to modulate the plasma outflow.In this paper,the experiment of plasma ablation with a magnetic field modulated by tens of Tesla is introduced.The change of plasma state can be obtained by X-ray spectrum diagnosis of aluminum ion,and the spectrum diagnosis range is from 1540 e V to 1645 e V.The experimental results show that the magnetic field can effectively restrain the plasma expansion and increase the plasma electron temperature near the target surface through the anisotropic heat conduction mechanism.In addition,we demonstrate the emission scene of Kepler accretion disk jet system through the experiment of the interaction between the nanosecond laser and the vortex coil target to produce the poloidal magnetic field collimated plasma outflow.The strong magnetic field driven by laser is also of great value in the research of fast ignition laser fusion.The short pulse laser with relativistic intensity(≥1018 W/cm2)can instantly ionize the solid surface and generate a megaampere electron current.Just like driving a laser,this current of megaamperes and the megagauss magnetic field it excites are also in the form of ultrashort pulses.However,for the hot electrons behind the target,such a pulsed magnetic field can still be regarded as"static"and modulate the beam.In this paper,the experiment of particle beam magnetic field interaction between short pulse laser and micro multi turn metal solenoid is introduced,and a relatively uniform quasi-static magnetic field environment is constructed.The existing experimental and simulation results show that the magnetic field of this configuration can effectively reduce the electron beam divergence angle.On the basis of picosecond light experiment,we can further reduce the size of the solenoid and use femtosecond laser to drive it to obtain stronger magnetic field.In laser plasma experiments,it is often necessary to detect the particle beam quantitatively in two-dimensional space.As a continuous medium,Gafchromic radiochromic film（RCF）has excellent spatial resolution.Compared with previous generation products,the new generation of RCF（HD-V2,MD-V3,EBT3）has also improved in data integrity and dose accuracy.For the determination of absolute dose,we need to know the response efficiency（RE）of the film.RE is affected by the type and initial energy of irradiated ions.Theoretically,each element has different coloration efficiency in each energy band.Therefore,the calibration work required to obtain complete re data is huge.Taking the dose response characteristics of HD-V2 RCF to single energy argon ion as an example,this paper proposes a method to calculate the response efficiency of different kinds of ions by using track theory,which can be used to estimate the response of RCF to some uncalibrated ions.At the same time,the RGB three color calibration function is given to apply to the dose measurement of multi-channel dosimetry.These results are expected to provide reference for the measurement of ion dose in HEDP experiment. |
