Senior Researcher / PhD

Graduated from Kharkov State University in 1972. Since 1985 he is with the Quantum fluids and Solids Department of ILTPE NAS Ukraine, defended a PhD Thesis in 1994.  
Scientific interests: thermodynamic and kinetic properties of liquid solutions of helium, the technics of ultralow temperatures.

Study of the kinetics of the phase separation in liquid 3He-4He superfluid mixtures and dynamics of the new phase growth. Construction of the rapid nucleation line and identification of nucleation mechanisms in superfluid mixtures.

Investigation and measurements of the kinetics growth coefficient of phase separated 3He-4He mixtures by propagation acoustic wave through interface between two phases. Establishing the two different growth mechanisms with crossover temperature 20 mK.  

Study of the mobility and instability of the plane phase separation line between two phases of the separated superfluid 3He-4He mixtures.Investigation of the different mechanisms of thermal conductivity in the superfluid 3He-4He mixtures.

Investigation of the superfluid turbulence in He II and superfluid mixtures.

He is an author and co-author of over 90 publications.

Research activity - Superfluidity of 4He and 3He-4He solutions\Quantum turbulence,Thermodynamic properties and kinetic processes

Recent publications:

Author and co-author of 90 papers. Among publication:

1. E.Ya.Rudavskii, V.K.Chagovets and G.A.Sheshin, Sov. J. Low Temp. Phys. 15(6),
  320(1989), Ferst-sound velocity in the impuriton system of superfluid 3He-4He solutions.

2. V.A.Mikheev,E.Ya.Rudavskii, V.K.chagovets and G.A.Sheshin, Sov. J. Low Temp. Phys.  
  17(4),233(1991), Phas separation in 3He-4He solution. Fast nucleation line.

3. I.N.Adamenko, A.I.Chervanev, K.E.Nemchenko, V.A.Mikheev,E.Ya.Rudavskii,  
  V.K.Chagovets and G.A.Sheshin, J. Low Temp. Phys., v.95, N5/6, 492(1994), Nucleation 
  and growth of the new phase in the supersaturated 3He-4He superfluid solutions.

4. J.Li, G.A.Sheshin, I.Roggatz and F.Pobell, , J. Low Temp. Phys., v.102, ½, 61(1996).
  Heat capacity of titanium hydride at millikelvin temperatures.

5. J.Nyeki, R.Ray, G.Sheshin, V.Maidanov, V.Mikheev, B.Cowan, and J.Saunders Low  
  Temp. Phys. 23(5-6), 379,(1997). Structure and superfluidity of 4He films on plated  
  graphite.

6. V.K.Chagovets, E.Ya.Rudavskii, G.A.Sheshin, and I.A.Usherov-Marshak, J.Low Temp.  
  Phys. 113,1005(1998), Attainable supersaturation of superfluid 3He-4He solutions and the 
  role of quantized vortices.

7. G.Sheshin, H.Abe, M.Nakazava,T.Satoh, J.Low Temp.Phys. 121,315-322 (2000) 
  Transmission of first sound wave at the interface of phase-separated 3He-4He mixtures.

8. E.Rudavskii,V.Chagovets, T.Kalko, I.Usherov-Marshak, G.Sheshin, J. of Molecular 
  Liquids, v.93, N1-3, p.61-63 (2001) Acoustic properties of supersaturated superfluid 3He-
  4He solution.

9. E.Rudavskii, V.Chagovets, T.Kalko, A.Zadorozhko, G.A.Sheshin, Physica B, 329-333, 
  170-171,(2003), Temperature and concentration gradients in superfluid 3He-4He mixtures 
  under steady-state conditions.

10..E.Rudavskii, V.Chagovets, T.Kalko, A.Zadorozhko, G.A.Sheshin, Physica B, 329-333, 
  176-177,(2003), The first sound velocity and attenuation of supersaturated superfluid 
  3He-4He solutions under elevated pressure.

11. E.Rudavskii, V.Chagovets, T.Kalko, A.Zadorozhko, G.A.Sheshin, J.Low Temp.Phys. 
  134, 463-470 (2004). Onset of convection in superfluid 3He - 4He mixture heated from 
  below.

12. E.Rudavskii, V.Chagovets, T.Kalko, K.Neoneta A.Zadorozhko, G.A.Sheshin,
  J.Low Temp.Phys. 138, N1/2, 301-308 (2005). Thermal Instability of Superfluid Phase-  
  Separated 3He - 4He Solution Heated From Below.

13. E.Ya.Rudavskii, V.K.Chagovets, T.V.Kalko, K.E.Nemchenko, A.A.Zadorozhko,  
  G.A.Sheshin, Journal of Molecular liquids, vol 120 ,p.185-188, (2005). Relaxation 
  Processes in Phonon - Impuriton System and Effective Thermal Conductivity of 
  Superfluid 3Не - 4Не Solutions.

14. N.Dubrovinskaia, G.Eska, H.Braun, G.Sheshin Journal of Applied Physics, 99, 033903, 
  (2006). Superconductivity in polycrystalline boron – doped diamond synthesized at 20  
  GPa and 2700 K.

15. G.A.Sheshin, S.Sokolov , Journal of Molecular Liquids, 127, 153, (2006) Thermal 
  instability of stratified superfluid mixtures 3He - 4He under heating from below.

16. E.Rudavskii, V.Chagovets, T.Kalko, K.Nemchenko, A.Zadorozhko, G.A.Sheshin, 
  J.Low Temp.Phys. 146, ¾, 403 – 416 (2007) Temperature and concentration relaxation in 
  separated superfluid 3He -4He solution.

17. E.Rudavskii, V.Chagovets, T.Kalko, A.Zadorozhko, G.A.Sheshin, J.Low Temp.Phys. 
  148, ¾, 151 – 155 (2007) Phase separation and nucleation in superfluid mixtures of 3He- 
  4He at presence of a heat flow.

18. E.Rudavskii, V.Chagovets, T.Kalko, A.Zadorozhko, G.A.Sheshin,J.Low Temp.Phys. 
  150, ¾, 420 – 425 (2008) Convective turbulence in superfluid solutions 3He– 4He.

19. E.Rudavskii, V.Chagovets, T.Kalko, A.Zadorozhko, G.A.Sheshin, L.Skrbek, 
  M.Blazhkova, ФНТ, т34,11, 1111 - 1121 (2008) Особенности перехода к 
  турбулентности в сверхтекучем 4Не при низких температурах.

2008

ФНТ, т34,11, 1111 - 1121 (2008)

Features of transition to turbulence in superfluid 4Не at low temperatures

G.A. Sheshin, A.A. Zadorozhko, E.Ya. Rudavskii, V.K. Chagovets, L. Skrbek, M. Blazkova

The experimental research of the kinetic and dissipative processes in He II by means of vibrating piezoquartz resonator (tuning fork) immersed into liquid helium has been carried out. The electric response of a tuning fork near to its resonant frequency was measured at various exciting voltage in the field of temperatures from 0,1 K up to 4,2 K. The measured values of half-width resonant curves have allowed to determine viscosity of normal components He II in wide area of temperatures. The maximum of effective viscosity is found out at temperature 0,5 K which is connected with transition from a hydrodynamic mode to a ballistic mode in the phonon gas of He II. It is established, that at small speeds of fluctuations of a tuning fork linear dependence of speed of fluctuation on exciting force that corresponds to laminar current of a liquid in a boundary layer near the vibrating surface is observed. Thus, the basic dissipative process is connected with viscosity of normal component. Thickness of a boundary layer near the surface of vibrating tuning fork is estimated. At the high speeds fluctuation of the tuning fork the breaks on dependence of the electric response on the exciting voltage, testifying about transition to nonlinear character of flow have been found out. At low temperatures this mode was accompanied by occurrence of flat sites on resonant curves near to a maximum. It is possible to explain such behavior by transition from laminar to turbulent flow of the liquid, that also it is accompanied by occurrence additional dissipation, connected with a birth of the quantized vortices. Critical speed of transition to the turbulent mode which temperature dependence will qualitatively be coordinated with the measurements received earlier with vibrating bodies of other form is determined.