On Energy Deposition Effect Of High-intensity Pulsed Ion Beam Irradiation

The generation of high-intensity pulsed ion beam (HIPIB) and interaction mechanism of its irradiation have been studied on TEMP-6-type HIPIB apparatus. The response of magnetically insulated ion diode (MID) during the pulse, the key issue for HIPIB technology, is analyzed for principle of HIPIB generation in bipolar-pulse mode. And the energy deposition of HIPIB irradiation is calculated using Monte Carlo (MC) method, to explore the interaction mechanism between HIPIB and target materials.On the bipolar-pulse mode HIPIB apparatus, a planar diode model of self-magnetic field MID is proposed for analysis of the diode behaviour during the negative pulse stage. The field enhancement effect of whisker-like microprotrusions on the anode surface is calculated, it is found that the microscopic electric field is enhanced by 2-4 orders higher as compared to the macroscopic electric field. The formation of self-magnetic field generated by electrons emitted from the anode surface bridging the grounded cathode plate follows a sequence from narrow part of the anode-cathode (A-K) gap to the wide part during the negative pulse. A dimensionless parameter magnetic divergence D_M is introduced to characterize the magnetic insulation behavior. It is found that an ideal insulation is related to a lower D_M. Moreover, the role of middle delay of the bipolar pulse on the diode response is established. On the one hand, it facilitates the expansion of anode plasma. On the other hand, it contributes to supplying sufficient ions for HIPIB extraction by enlarging the ions number in the A-K gap.The energy deposition principle of HIPIB irradiation is founded by using MC method. The energy deposition of HIPIB irradiation is a process from inner to outer of the target material surface layer, and ion range is growing with the enhancing of incidence ion energy, as its tendency correlating to ion mass. Incidence ion is straggling during transmitting in target material and tendency of which is consistent with that of ion range, but scope of ion straggle is much more less than that of ion range. However, the deposited energy of HIPIB irradiation is not continuous increasing with the enhancing of incidence ion energy, there is a critical value of deposited energy related to the property of target material itself. The deposited energy is increasing during the pulse and the increase velocity is dependent on the characteristic of HIPIB. The analysis of cross section Metallograph before and after HIPIB irradiation confirms the simulation results of energy deposition.