Magnetic compensation of gravity. Lionel Quettier

Transcription

1 Magnetic compensation of gravity Lionel Quettier

2 Levitation vs gravity compensation Levitation: Suspension of an object as a whole. Gravity may be uncompensated inside. Gravity compensation: Gravity is compensated inside, at the molecular level. H 2 liquid H 2 gaz Vessel with a goldfish is levitated on a superconductor palette (Ph. Ball, Nature, 1990) Two-phase H 2 inside a Ø 3mm plastic sphere at gravity compensation (D. Chatain and V. Nikolayev, Cryogenics, 2002) 2

3 How to obtain microgravity conditions? Drop tower ~4-9 s of µ-g Parabolic flights (A300 Zero-G) 25 s of µ-g Sounding rocket (Maxus) 13 min of µ-g Space missions (ISS) months of µ-g Disadvantages Too expensive and long waiting period for ISS Too short µ-g for drop tower, sounding rockets and parabolic flights Possible alternative: magnetic compensation of gravity 3

4 Magnetic compensation of gravity - Main milestones Basic studies 1845 (M. Faraday) Discovery of diamagnetism 1939 (W. Braunbek) Necessity of a diamagnetic substance for the levitation stability Theory of levitation; Levitation of diamagnetic bismuth 1947 (V. Arkadiev) Superconductor levitation (first use of superconductors) First gravity compensation experiments with a fluid (O 2 ) in 1960s Studies of boiling heat transfer in microgravity (space rocket fuel) Resistive solenoids Lyon et al., Berkeley, USA, 1965 Kirichenko et al., Kharkov, USSR (now Ukraine),1968 4

5 Magnetic compensation of gravity - Main milestones Modern studies: use of superconductive solenoids ( E. Beaugnon, R. Tournier, Grenoble (France); levitation of water Courtesy E. Beaugnon 1997 A. Geim et al. Nijmegen (The Netherlands) Levitation of a frog 5

6 Back to the basis Magnetic force acting on diamagnetic and paramagnetic materials: 1 m F grad m V B 2 0 magnetic permeability of the vacuum B magnetic flux density magnetic susceptibility m > 0 for a paramagnetic material < 0 for a diamagnetic material V volume g is the terrestrial acceleration 0 2 Compensation condition: G = 0 g G = 0 g -2 m m with G grad( B 2 ) 6

7 Required grad(b²) for exact compensation at one point Substance G= grad(b²) (T 2 /m) O 2 (90K) +8 H Deuterium H 2 O He N Oxygen is a paramagnetic material, its susceptibility depends on the temperature. 7

8 Maxwell s equations and magnetic force field Maxwell s equations: curl(b)=0 and div(b)=0 in a magnetically empty region of space (no electric current or any piece of magnetic material) It is impossible to generate a purely constant magnetic force field inside a given volume Magnetic sources can only create a quasi-unifom magnetic force field Residual forces are described by a relative inhomogeneity vector Theorem: B G R 2 r z Axisymetrical configuration with B 0 Magnetic field in the useful area R Radius of the useful area r z, components of the inhomogeneity vector 8

9 How to obtain magnetic compensation of gravity? Let s consider a single solenoid magnet Gravity compensation for diamagnetic materials Magnetic field on the central axis (arbitrary units) Gravity compensation for paramagnetic materials Vertical component of grad(b²) on the central axis (arbitrary units) 9

10 Consequences of the relation between B,G,V and ε Axisymetrical configuration (solenoids) G(T²/m) homogeneity volume (cm ) B(T) water % 1 20,8 5% 1 9,3 1% 2 23,4 5% 2 10,5 helium % 1 25,2 5% 1 11,3 1% 2 28,3 5% 2 12,7 hydrogen % 1 12,5 5% 1 5,6 1% % 2 6,3 oxygen 11 1% 1 1,3 5% 1 0,6 1% 1 Liter 4,1 5% 1 Liter 1,8 3 B G R 2 r z High magnetic fields only achievable using superconducting magnets! 10

11 Applications in physical sciences Studies of shape of bubbles and drops H 2 O drop oscillations (vibration and/or rotation): Grenoble (France), Brown (USA), Nottingham (UK) H 2 O drop shape depending on gravity: Hiroshima (Japan) He drop coalescence: Grenoble (France), Brown (USA) Rapid effective gravity changes in O 2 : Grenoble (France) O 2 drops behavior, Durham (UK) Boiling in O 2 and H 2 ; bubble behavior, heat transfer, boiling crisis: Berkeley (USA), Grenoble (France) Heat transfers on He: Saclay (France) Studies of gravity compensation with diamagnetic solids Granular matter: Nottingham (UK), Florida (USA) Gyroscope: Nijmegen (NL) 11

12 Applications in life sciences Structural biology Growth of fine protein crystals: Tsukuba, Tohoku (Japan), Nijmegen (NL) Genetics Expression of transcription factors after exposure of cell cultures to gravity compensation: Nottingham (UK) Magnetic forces and cell buoyancy: Florida, Brown (USA), Nottingham (UK) Effects on living matter: Nottingham (UK) Modifications of Drosophila Behavior on yeast (more generally, on cell cultures) on mammalian phagocytes 12

13 A few more detailed examples 13

14 Example 1: Study of fluids Superconducting magnets can be used to assist satellite launcher design Flight experiments are using highly flammable fluids like hydrogen and oxygen whose study is extremely important as they are the fuel components for space propulsion engines. Earth ground experiments of LH 2 and LO 2 under microgravity can be performed using superconducting magnets 14

15 Example 1: Study of fluids Pool boiling of oxygen: evolution of the bubbles size as a function of the gravity level (Courtesy D. Chatain) 8mm 1m 2T - NbTi solenoid - Ø300mm G. Pichavant et al., Microgravity Science and Technology, vol 21, pp ,

16 Example 2: Protein crystal growth Crystal growth is an exothermic process Gravity is a motor of convection: low gravity means low convection, which allows obtaining very pure proteins. Very interesting for understanding proteins structure (X rays analysis) Sedimentation and growth of E. Coli bacteria Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability, Journal of The Royal Society Interface, (2010) 16

17 q c (W/m 2 ) Example 3: He pool boiling under microgravity Helium is a diamagnetic material (G=-4150 T 2 /m) used to cool down superconducting magnets Could magnetic forces affect the cooling performances? q c 1/ 4 1/ 2 hlv v g l v K K= Critical Heat Flux vs gravity level g/g e CEA Saclay Experimental cell Studies performed in a 17 T Nb 3 Sn solenoid ( maximum G of only T 2 /m) Measured values in agreement with Zuber s law that predicts CHF=f(g 1/4 ) L. Quettier, B. Baudouy, A magnet system design for reduced gravity environment, Cryogenics, Vol 50 (2010) 17

18 Design of a dedicated superconducting magnet All the current experiments performed are using existing superconducting solenoids: Small V Small G Poor Why not optimizing a levitation magnet? Large V High G Better 18

19 Design of a dedicated superconducting magnet Example of a set of NbTi coils for LO 2 levitation (2 1%) Coils arrangement Magnetic field map Overall facility C. Lorin et al. Design of a Large Oxygen Magnetic Levitation Facility Microgravity Sci. Technol, DOI /s ,

20 From micro-gravity to hypergravity For the previous magnetic design For a single solenoid Microgravity (~ 0 g) Hypergravity (up to 2 g) Microgravity zone for diamagnetic materials Hypergravity for diamagnetic materials Modification of the current polarity on some coils (J=-60 A/mm² / J=+60A /mm²) Modification of the experimental area location Two in one function with the same superconducting magnet! 20

21 Magnetic compensation and magnetic field Microgravity is compensated using high magnetic fields One must discriminate the influence of magnetic field from the influence of reduced gravity B=0, G=0 B=18.9 T, G=0 B=14.4 T, G=-2350 T²/m Transgenic arabidopsis plants as monitors of low gravity and magnetic field effects. Stalcup, et al., Proceedings of Physical Phenomena in High Magnetic Fields, Singapore : World Scientific, pp , But, this also open new perspectives, only easily achievable with earth ground experiments. 21

22 Conclusions Magnetic compensation of gravity is a well established technique. Large community of users, various applications. Due to the required high magnetic fields, superconducting magnets must be used; however: Technique much cheaper than experiments performed in space Long term experiments are possible Variable levels of compensation/homogeneity can be obtained with the same magnet (modification of the operating current or of the experiment location) Dynamic studies (time variable gravity) are possible (by ramping up/down the current inside the magnet, by inducing a fast discharge of the magnet ) Current experiments are based on existing superconducting solenoids. Dedicated levitation magnets must be developed and built for achieving a better compensation and larger useful volumes to open new fields of research! 22

23 Thank you for your attention Thanks to E. Beaugnon, D. Chatain, C. Lorin and V. Nikolayev for their contribution in this talk. 23