Study On Negative Ions Collisions With Atoms Molecules And Nondestructive Detection Of Cylindrical Nuclear Materials

This dissertation includes two parts: the single-electron and double-electron detachment of negative ions in collision with helium and nitrogen; nondestructive detection of cylindrical nuclear materials.The collisions between negative ions and target atoms or molecules are not only a very important phenomenon, but also a powerful tool in study of negative ions properties. The experimental results could be very useful for the electron correlation theory, and be necessary for flame chemistry, ionosphere physics, astrophysics and plasma physics, especially very valuable in the study of high power laser and generation of strong neutral atomic beams.The single electron detachment(SED) experimental system has been setup by GW Li and XM Zhang, which include a cesium sputtering negative ion source , isotope separator with a 90° analyzing magnet, drift tube with some slits , colliding chamber, detector, and logically controlled multi-channel analyzer . By using growth-rate method in which the neutral atoms and total particles passing through the gas chamber were detected by the same detector in alternative time, we measured the SED cross sections of C^-, Si^-, Ge^-, O^-,S^-,F^- and Cl^- collision with helium, Cr^- ,Ti^- and Cu^- incident on nitrogen from 5keV to 30 keV. We modified our SED experimental system to measure the double-electron-detachment(DED) cross sections of negative ions incident on atoms. Weconfirmed our results of H- incident on helium by comparing with JS Allen's, and then measured DED cross sections of C^-, Si^-, Ge^-, O^-,S^-,F ^- and Cl^- collision with helium in 5keV 15keV. The data of SED cross sections of Ge^-, Cl^-,S^- with helium in 5keV 30keV and DED cross sections of C^-, Si^-, Ge^- , O^- ,S^-,F^- and Cl^- with helium in 5keV 15keV are complemented and we observed the maximum cross sections of C^-, Si^-, O^- and F^- collision with helium in our energy range from 5keV to 30keV. Our measurement errors were relatively small, because the detecting efficiency for the anions is the same as for neutral atoms in SED measurement and the detecting efficiency for ions is the same as for anions in DED measurement.The other work in the dissertation is nondestructive detection of cylindrical nuclear materials. We acquired the gamma-ray self absorption coefficient of the cylindrical nuclear material ²³⁵U. The geometry information of the ²³⁵U cylinder can be obtained after multi-position measurement of gamma characteristic spectroscopy intensity. This study could be applied to the fissile material safeguard, such as nuclear monitoring and verifying.