Diagnosis Of The Plasma In The EBIT And The Experimental Study Of The Sputtering Induced By The Impact Of Highly Charged Ion On Solid Surface

Highly Charged Ion (HCI) is an ion which has high Z value and is peeled offmost of bound electrons. The study of HCI is interested in astrophysics, quantumchromo dynamics, hyperfine atomic structure and measurement of atomic mass.The HCI is also respected to be a powerful tool for surface modification andsurface analysis. In addition, HCI is the favorite choice in medical application ofheavy-ion cancer therapy because HCI is easy to be accelerated.In this paper, the characteristics and sources of the HCI were introduced. Thestudies of the interaction of HCI with solid surface which had done by othersgroups and experimental, theoretical results were presented briefly. The operatingprinciples of the ECR source and EBIT (electron beam ion trap) were described.The experiment of sputtering induced by impact of HCIs on solid surface wasdescribed in detail. As well as, the chamber, preparation of the targets and targetholder were introduced. The EBIT system and X ray detector were presented. Theoperating principle of the Wien filter was roughly introduced and the testexperiment, control software and analyzing software were introduced in detail.It was studied that the parameters of the EBIT influenced on the intensity ofthe extracted ion beam and the stability of the EBIT. It was indicated the electrondensity was sensitive to the electron energy, which had influence not only on thedark current but also on the intensity of the extracted ion beam. The pressureinfluence on the specific ion beam is depended on the charge state of the ions. Forthe highly charged ions, the higher pressure was, the higher intensity of extractedion beam would be; for the lower charged ions, the case was opposite. When thedepth of the trap was 20V, the output of the ion beam was up to the maximum inleak mode. It was no clear how the extracted potential voltage affected on theoutput of the ion beam. The optimal value of the extraction voltage equals 4 ke V.It was measured the X ray spectra of the HCIs which were trapped in theEBIT as well as the extraction spectra of HCIs. The specific charged ions wereidentified by X ray form the dielectronic recombination process. The charge state distribution in the drift tube was obtained with opened and closed trap. Furtherthe evolution of the Kr^q+ (28q+ and Pb^q+ ions with different kinetic energies bombarded on the solid surfacesof Au, Ag, Nb, Cu, mica, W, silicon and glass and theangular distributions of sputtering were measured by a multi-channel plate. Therelation between sputtering yield and potential energy, kinetic energy wasintroduced. The experimental results showed that the sputtering yield wasincreased as the incident angle was grown for the impact of the HCIs on the metaland insulator surface and there was channeling effect during the HCIs bombardedon the silicon surface. The different trends were shown with impact of differentenergies Ar¹⁶⁺ and Pb³⁶⁺ on the solid surface. The sputtering yield increased as thekinetic energy of the projectile grown for the bombardment of Ar¹⁶⁺ ions withenergy from 96 keV to 320 keV. However in case of Pb³⁶⁺ with kinetic energyfrom 196 keV to 720 keV, the trend was not clear. The sputtering yield increasedwith the increasing of potential energy of the projectile during Ar^q+/Pb ^q+bombarded on the different surfaces. The cooperation sputtering model wasproposed to explain the results. The basic ideal of the model is the sputteringshould be separated into two portions. The one is kinetic sputtering yield, whichwas function of the incident angle. The kinetic sputtering yield is proportional tothe nuclear stopping power and inverse proportional to the bind energy of thesurface. Another was potential sputtering yield, which was proportional to theeffect charge state of the ion cubed. The experimental sputtering yield was fittedby an empirical formula of Y=Atan^Bθ+C. The formula is fitted well with themodel. The model was in good agreement with our results as well as the resultsfrom other groups.