Poster Session 115 Ion Beam Time-of-Flight Mass-to-Charge Analyzer for Ion Implantation Facility 1 V.I. Gushenets, A.G. Nikolaev, L.G. Vintizenko, E.M. Oks, G.Yu. Yushkov, A. Oztarhan,* and I.G. Brown** High Current Electronics Institute, Russian Academy of Sciences, 4 Academichesky ave., Tomsk, 634055, Russia, Ph: +7 (3822) 491776, Fax: +7 (3822) 492410, E-mail: nik@opee.hcei.tsc.ru * Ege University, Bornova-Izmir, 35100 Turkey ** Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 1 The work was supported by: – U.S. Department of Energy, Initiatives of Proliferation Prevention, project IPP-LBNL-T2-196, under Contract No. DE-AC03-76SF00098; – Grant of the President of the Russian Federation, the Dr. Sci. Program MD-148.2203.02; – US Civilian Research and Development Foundation, under Grant No. ТО-016-02. Abstract – We describe the design, electronics, and test results of a time-of-flight ion beam mass-to- charge analyzer for ion implantation facility that is used for ion beam material modification. The method selects a short-time sample of the beam whose mass-to-charge composition is then sepa- rated according to ion velocity and detected by a remote Faraday cup. The analyzer is a detachable device that can be used for rapid analysis of mass- to-charge composition of ion beams accelerated by voltages of up to about 100 kV. 1. Introduction Ion beams in the energy range of about 5 to 100 keV are employed widely for fundamental studies and for a variety of technological applications for ion beam material modification [1–3]. Magnetic spectrometry [4] is often used for measuring the mass-to-charge (M/q) composition of such beams. The method is based on the deflection of ions in a transverse mag- netic field and has high resolution and reasonable sen- sitivity. In this analytical approach the beam is cou- pled to the magnetic spectrometer in toto and at all times – that is, the beam is not sampled but is continu- ously analyzed. Thus this method is rather elaborate, consumes significant energy, is not low cost, and the beam cannot be used for its primary purpose while the analysis is taking place. While for many situations these constraints are acceptable and magnetic M/Q analysis is the preferred approach, for other situations an alternative method may be more suitable. The time-of-flight (TOF) method for measuring the mass-to-charge composition of an ion beam is based on the different times required for ions of different M/Q values to drift over a fixed distance, and requires analysis of only a small time-sample of the ion beam that is deflected from its initial path [2, 3, 5, 6]. The time-of-flight spectrometer possesses a reasonably high resolving power, (M/Q)/∆(M/Q) > 10, and a rather high sensitivity, allowing analysis of ions from hydrogen to uranium. Analysis of all beam compo- nents is done at the same time. As for many ion beam techniques, there are constraints on the vacuum cham- ber pressure, which should be less than ~ 10 –4 Torr since scattering of the ion beam by residual gas atoms and the associated energy loss during the ion drift time should be minimal. Since this is precisely the operat- ing pressure regime that is typical of most ion sources and ion beam applications, this is usually not a burden [6]. The investigation of mass-to-charge composition of ion beams by the time-of-flight method has been used extensively in studies utilizing the MEVVA [7], TITAN [8, 9] and other [10] vacuum arc ion sources. Modification of this kind of time-of-flight spectrome- ter has allowed us to increase the resolution and de- crease the distortion of ion current signals [9]. Here we describe a modified, detachable time-of- flight mass spectrometer that can be installed easily for analysis of ion beam mass-to-charge composition, and present the results of M/q measurements of the ion beam generated by the MEVVA-V vacuum arc ion source at Izmir, Turkey. Detailed consideration is given to the design and operating principles of the analyzer, and to the electronic circuitry. 2. Design and Principle of Operation The overall layout of the time-of-flight analyzer is shown in Fig. 1. The analyzer system is housed in a stainless steel vessel 1, through which the ions drift, of length 1 m and diameter 25 cm. The spectrometer gate 2, is located at the beam entrance end of the vessel, and a Faraday cup 3, at the other end. The gate of the analyzer (Fig. 2) consists of five pairs of concentric metallic rings or plates (short sections of tubes – the rings have axial length) spaced 1 cm apart. For each pair of rings, the outer ring is grounded and the inner is connected to electronics that provides an ion-