[1] Balt State Tech Univ, Fac Rocket & Space Engn, St Petersburg 190005, Russia
[2] St Petersburg State Univ, Fac Math & Mech, St Petersburg 198504, Russia
[3] Russian Fed Nucl Ctr, Russian Res Inst Expt Phys, Sarov 607188, Russia
[4] Kingston Univ, Fac Sci Engn & Comp, London SW15 3DW, England