Modeling electromagnetic field excitation and rf power absorption in a large helicon plasma Konstantin P. Shamrai a, Shunjiro Shinohara b, * aInstitute for Nuclear Research, National Academy of Sciences, 03680 Kiev, Ukraine b Inter discipli nary Graduate School of Enginee ring Sciences, Kyushu University , Kasuga, Fukuoka 816-8580, Japan Available online 21 November 2005 Abstract Wave propag ati on and rf power abs orpti on are considere d in a lar ge hel ico n pla sma source excited by a fla t antenna alo ng the magne tic fiel d. V arious singl e-, four- and six-t urn antennas of diffe rent dimensio ns are examined compa rati vely . The simpl e physi cal model and computation code accounting for the most important features of the system are introduced. Profiles of the rf magnetic field and abs orbed power and the ant enna loa din g res ist ance are comput ed over a broad ran ge of par ame ter s. Comput ati on res ult s are interpreted considering propagation characteristics of the waves, such as the group velocity and characteristic angle, and are compared with measured data. D 2005 Elsevier B.V. All rights reserved. Keywords: Helicon plasma; Inductively coupled magnetized plasma; Rf field; Radiation resistance; Group velocity 1. Introduction Helicon sources can produce dense plasmas over a broad range of oper ati ng para met ers [1,2] and, the ref ore, are attr acti ve for vari ous appl icat ions incl uding thi n fil m depos itio n (e.g. , [2–5] and refer ences there in). These devic es are known in two different basic configurations. The first is a conventional helicon plasma with a shell antenna enveloping the dielectric discharge chamber and launching the rf poweracross the magnetic field [1,2]. The second is magnetically enhan ced induc tivel y coupl ed plasma (or inductivel y coupl ed magnetized plasma, ICMP) with a planar antenna located behind the dielectric window and launching the power along the magnetic field [6–9]. Latter devices provide a unique possibility for generating plasmas of densities above 10 12 cm À 3 in the lar ge cha mbe rs, e.g., 45- cm dia meter and 170-cm long [7,8], and 75-cm diameter and 486-cm long [9], with moderate power in the range of 100 W. So extensive the pl asmas are pro mis ing for bas ic res earch,such as mod eli ng ofspa ce relevant phe nomena , and for app licati ons , such as proc essing of larg e surfaces, decomposit ion of hazar dous materials and space propulsion. V ariou s model s have been devel oped for chara cteri z- ing the ICMPs. T ASK /WF code whi ch assumes a col d pl asma of fi xed pro fil e [10] is especi all y eff ect ive forcomput ati ons wit h compli cat ed, e.g., cus ped mag net ic fields [11,12]. Another model accounts for kinetic effects but neglects the plasma and magnetic field nonuniformity and the radial struct ur e of the rf fields [13]. The mos tcomple te model considers bot h electroma gnetic and discharge effects [14] ; h ow e ve r, it ne e ds so much comput ation time that nor mal ly compel s one to ign ore small -scal e rf electr ostat ic effec ts. We pr esent a si mple model that is convenient for quick computa tion of the rf fiel ds, power depos ition and a nt en na l oa di ng r es i stance in the large ICMPs. It assumes a col d pla sma wit h pre scr ibe d (ei the r rad ial ly or axiall y nonuni form) densit y pr of ile and ta kes the rad ial field str uct ure int o acc ount. Comput ati on res ult s for dif fer ent lar ge ICMPs exc ite d by var ious single - and mult i- tur n ant ennas are int er pre ted consi der ing wav e 0040-6090/$ - see front matterD 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2005.08.051 * Corresponding author. Tel.: +81 92 5837649; fax: +81 92 5718894. E-mail addresses: [email protected] (K.P. Shamrai), sinohara@ae es.kyushu-u.a c.jp (S. Shinohara). Thin Solid Films 506–507 (2006) 555 – 558 www.elsevier.com/locate/tsf
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Konstantin P. Shamrai and Shunjiro Shinohara- Modeling electromagnetic field excitation and rf power absorption in a large helicon plasma
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8/3/2019 Konstantin P. Shamrai and Shunjiro Shinohara- Modeling electromagnetic field excitation and rf power absorption in…
Modeling electromagnetic field excitation and rf power absorption
in a large helicon plasma
Konstantin P. Shamrai a , Shunjiro Shinohara b,*
a Institute for Nuclear Research, National Academy of Sciences, 03680 Kiev, Ukraine b Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
Available online 21 November 2005
Abstract
Wave propagation and rf power absorption are considered in a large helicon plasma source excited by a flat antenna along the
magnetic field. Various single-, four- and six-turn antennas of different dimensions are examined comparatively. The simple physical
model and computation code accounting for the most important features of the system are introduced. Profiles of the rf magnetic field
and absorbed power and the antenna loading resistance are computed over a broad range of parameters. Computation results are
interpreted considering propagation characteristics of the waves, such as the group velocity and characteristic angle, and are compared