On The Principle Of High-intensity Pulsed Ion Beam And The Energy Deposition Of Its Irradiation

The generation of high-intensity pulsed ion beam (HIPIB) and modification mechanism of its irradiation have been studied as considering the two aspects that the HIP IB technology itself and its applications in the field of material surface engineering. The response of magnetically insulated ion diode (MID) under the two pulse mode of bipolar-and unipolar-is analyzed for unfolding the principle of HIPIB generation, respectively. And, the energy deposition by HIPIB irradiation for the two pulse mode is also calculated by utilizing Monte Carlo (MC) method, respectively, to explore the interaction mechanism between HIPIB and materials.In allusion to the response of self-magnetic field MID during the pulse of bipolar-pulse mode, unltilizing the experimental results of the diode response characteristics, the behaviour of diode during the negative pulse stage is analyzed by constructing a planar diode model. Calculation of the field enhancement effect of the whisker-like microprotrusions on anode surface shows that the microscopic field is enhanced by 2-4 orders as compared to the macroscopic field. A dimensionless parameter magnetic divergence Dm is introduced to characterize the magnetic insulation behaviour, and found that a better insulation effect is related to a lower DM.Moreover, the role of middle delay pulse of the bipolar pulse on the diode response is established, one is facilitate the expansion of anode plasma to expanding the anode plasma sufficiently, and the other is enlarge the plasma density in the anode-cathode (A-K) gap to supplying enough ions for ion beam extraction in the positive pulse. The successive time field transfer of different effects in the different pulse stage during the diode response is obtained by the analysis of diode impedance and perveance during the whole bipolar pulse.Aiming at the response of external-magnetic field MID during the pulse of bipolar-pulse mode, unltilizing the experimental results of the diode response characteristics, the initial anode plasma formation mechanism and region is understood by calculating the distribution of electric field and critical magnetic field in A-K gap via constructing a coaxial columniform ion diode model. The exist of anode polymer film enhancing the electric field on polymer surface by 2-3 times, and the electric field in diode narrow region is outclass that in diode wide region due to the asymmetry A-K gap of diode. The avalanche breakdown firstly takes place to form the initial anode plasma in diode narrow region in 15 ns of unipolar pulse owing to the large electric field grads. After that, the flashover on anode surface under the grads of electric field and magnetic field, increasing the plasma density, and the breakdown and flashover region expanding towards the diode wide region. The distribution of extracting velocity and time of flight (TOF) of 14.5 cm in vacuum of ions is given as considering the energy difference of extracting ions during the pulse. The TOF difference of ions resulting in the duration of ion current density larger than that of the applied diode voltage pulse, and also leading to the diversity of the ion energy profile on the material surface from that extracting in diode.The energy deposition profile of HIPIB irradiation with different and single energy as well as given pulse width is founded by using MC method, respectively. The energy deposition of HIPIB irradiation is a process from inner to outer on materials suface layer, and ion range is growing with the increasing of incident ion energy, as its tendency correlating to ion mass. Incident ions are straggling during transmitting in material and tendency of which is consistent with that of ion range, but scope of ion staggle is much more less than that of ion range. However, the deposited energy of HIPIB irradiation is discontinuous increasing with the enhancing of incident ion energy, there is a deposited energy extremum related to the property of materials itself. The deposited energy of HIPIB irradiation is increasing during the pulse and the increase velocity is dependent on the characteristic of HIPIB.Taking into account the TOF of ions, obtaining the energy deposition rule of HIPIB irradiated on material surface under the two pulse mode. Due to the TOF effect of diverse ions during the pulse duration, a evident separate peak structure appearce in the energy profile of ions acting on material surface, and elongating the time field duration. The energy distribution of HIPIB on material surface is a complex profle with a transform from a single species ion energy distribution to a multi-species ion complex energy distribution. A practical ion current density profile on material surface is deduced by correlateing the ion energy and ion current density. The energy deposition rule of HIPIB irradiation on solid materials is obtained considering the influence of TOF effect of ions on HIPIB energy profile. The enengy deposited region of HIPIB irradiation has a shallowing trend, and deposited energy is accumulating in shallower layer. A discontinuity occurs in energy deposition profile of HIPIB irradiation due to the discontinuous HIPIB energy distribution on material surface. There is a obvious transition both on energy deposition profile of differ stage or total of the pulse while the C+ arrives at material surface. The presence of separate peak structure during the energy deposition process by HIPIB irradiation is one of the important characteristics of its material surface modification.