Fast Recoil-ion Momentum Spectroscopy Of Violent Close Collisions Between Highly Charged Heavy Ions And Atoms

Violent close collision between highly charged heavy ions and atoms is a kind of collision in which the two nuclei are close enough that the K or L shell orbits of projectile and target penetrate each other.It is a deep inelastic collision process that the Q value of the system and the kinetic energy obtained by recoil ions are relatively large(even up to the order of ke V).However,the present experimental techniques,which are still limited to measure the energies and the angular distributions of the scattered or recoil ions,or their coincidence measurements,are hard to efficiently obtain more precise physical information.In this work,a new fast recoil ion momentum spectroscopy(FRIMS)technique is proposed for the violent close collision between highly charged heavy ions and atoms.A novel electric field layout is employed in order to eliminate the huge amount of interference events produced in distant collisions.The reconstruction resolution,which caused by the measurement error of recoil ion’s flight time and impact position,is analyzed to determine the geometric structure and layout of FRIMS.FRIMS-V1 was first developed.During the development,the main work includes the simulation and optimization of the spectrometer electric field,the development of Φ36 timing detector,the development of Φ106 2D position sensitive detector based on a cross-connectedpixels anode and the development of Φ 106 two-dimensional position sensitive detector based on double-layer strip array anode.Then,the incident beam collimation system of the spectrometer and the experimental terminal are improved according to the test results.After that,two tests were carried out in which high-energy recoil ions were observed.But,the random coincidence rate of scattered and recoil ions was significantly higher than the real count due to the background noises.The spectrometer was optimized in order to improve the vacuum and then reduce the background noise.At the same time,a Φ106 two-dimensional position sensitive detector based on metal strip anode is developed to reduce the coincidence time.At present,the improved device is being tested,and a new experiment will be carried out in the near future.Another part of this work is about Classical Trajectory Monte Carlo(CTMC)simulation works.In this section,a new method for generating the initial state of electron in hydrogen atom based on Microcanonical Distribution is proposed.The ionization and electron capture cross sections of the collision process between proton and hydrogen atom are calculated.The results are in good agreement with other CTMC calculations and experimental results.This method will be extended to multi-electron atoms in the future.In order to obtain the initial position and momentum distributions of electron as closer as the results of quantum mechanics,Wigner and Husimi phase space distributions are employed.The method of J.P.Dahl et al.and Monte Carlo sampling are utilized to obtain the distributions of electron.The time-dependent evolutions of the position and momentum distributions are also studied.