Small Sensors at Low Temperature Revealing Cryogenic Turbulence

1. Small Sensors at Low TemperatureRevealing Cryogenic Turbulence • Andrew Rinzler • Jennifer Sippel-Oakley University of Florida Physics Gary Ihas- Yihui Zhou Ridvan Adjimambetov Shu-chen Liu Isaac Luria Mario Padron Mark Sheplak-University of Florida Engineering T. Chen Vadim Mitin-V. Lashkarev Institute of Semiconductor Physics, NASU, Kiev, Ukraine Funding: Research Corporation Miramare June 10, 2005

2. Thank you Mr. Organizer In his lab circa 2004 (with research trainee)

3. Thank you Mr. Director In his lab circa 2005

4. Thank you Mr. Helium Vorticity 50th Anniversary of First Direct Detection of Quantized Vorticity

5. Low Temperature Motivation-Small apparatus size & Quantum turbulence decay studies • Measurement Techniques • Thermal-Electrical Resistance • Semiconductor technology • Results • Mechanical • Piezo-resistive • Piezo-electric • Capacitive • Optical • Results • Nanotube films • Thermal • Mechanical • Results Outline

6. Characteristics of turbulent flow • Irregularity — randomness • Diffusivity — rapid mixing and increased rates of momentum, heat and mass transfer • Large Reynolds numbers • Three-dimensional vorticity fluctuations • Dissipation — due to viscous loss; decaying rapidly without energy supply • Continuum — even smallest scales >>molecular length scale UL inertial force = = R n viscous force e [H. Tennekes, 1983]

7. Large Scale Turbulence JPL

8. Intrepid Experimentalist

9. A Matter of Scale R=107 Oregon Cryogenic Facility Water Facility of Nikuradse

10. Grid turbulence in a classical fluid[Frisch, 1995] Eddy motion Smaller length scale Larger length scale (wavenumber, k > inverse of vortex line spacing, ) (the mesh of grid  the size of the channel) Grid Turbulence Energy flow rate Energy input Dissipa-tion k Energy dissipation by viscosity (Re ~ 1) inertial regime Re >> 1 Kolmogorov Spectrum [H. Tennekes, 1983]

11. (oscillating disc viscometer) Two Fluid model density viscosity entropy Two fluids Super-fluid s s =0 irrotational Ss =0 normal fluid n = n Sn=SHe Viscosity (P) [J. Wilks, 1987] 4He Fluid density =n +s  0.14g/cm3  s 56 %  n T (K) 0 2.0 T Two Fluid Model– Landau -1941

12. Quantization of superfluid circulation: (postulated separately in 1955 by Onsager and Feynman) All superfluid vortex lines align along the rotation axis with ordered array of areal density= length of quantized vortex line per unit volume=  2000 lines/cm2 The angular velocity  is (a) 0.30 /s, (b) 0.30 /s, (c) 0.40 /s, (d) 0.37 /s, (e) 0.45 /s, (f) 0.47 /s, (g) 0.47 /s, (h) 0.45 /s, (i) 0.86 /s, (j) 0.55 /s, (k) 0.58 /s, (l) 0.59 /s. [Yarmchuk, 1979] Quantization of Superfluid Circulation 1. Circulation round any circular path of radius r concentric with the axis of rotation=2r2  2. Total circulation=r2n0h/m (n0: # of lines per unit area) 3. n0=2  m/h=2 /

13. Cryogenic Towed Grid Apparatus Niobium cylinder Superconducting solenoid Grid Liquid Helium Dimensions in inches

14. Drive Simulation

15. Techniques To Study Quantum Turbulence • Observation of rise in temperature of helium as turbulence decays • Localized correlated pressure measurements to detect vortex motion and density • Flow

16. Operating temperature: 10 - 100mK. • Sensitivity: T ~ 10-7K, or T/T ~ 10-5. • Short response time: t ~ 10-3 s. • Small mass & good thermal contact. Requirements for the thermometers Two excellent candidates 1. Neutron transmutation doped Germanium Bolometer--[N. Wang, 1988] sensitivity (rms energy fluctuation 6 eV at 25mK); T/T ~ 4.810-6 response time < 20 ms size: 1mm1mm0.25mm 2. Miniature Ge Film Resistance Thermistors-- [V.F. Mitin, et al.]sensitivity =50/K- 100/K in the temperature range 50mK- 10mK response time< 0.1s size: 650 m

17. Conduction in a doped semiconductor

18. Mass Production/Consistency • Each wafer will generate sensors with very similar properties • Resistance measurements made on a single batch over the range 10K – 150K • A single fixed point measurement at 4.2K will approximate the sensors properties if the entire curve for any one sensor from the batch is known Advantages of Thin Film Technology

19. Activelayer Insulator Semiconductor Chip Technology Ge/GaAs thermistors 300 m square by 150 m thick. Mass of the thermistor = 7.2  10-5 gram.

20. http://microsensor.com.ua/products.html Thermistor R vs. T Development Work

21. sampling on micron scale • sensitivity: 0.1 Pascal • fast: 1 msec • function at low temperatures (20 – 100 mK) • transduction: as simple as possible Pressure Transducer Requirements MEMS Technology Pressure Sensors • Piezo-resistive • Capacitive • Optical

22. Design Of Piezo-resistive Pressure Sensors • Typical design: 4 piezo-resistors in Wheatstone bridge on a diaphragm • diaphragm deflects from applied pressure causing the deformation of the piezo-resistors mounted on the surface Wheatstone bridge

23. Piezo-resistive Pressure Sensor SM5108 • Semiconductor resistors joined by aluminum conductors in bridge configuration • Resistors placed on diaphragm • Two strained parallel to I • Two strained perpendicular to I Manufactured by Silicon Microstructures, Inc.

24. Piezo-resistive Pressure Sensor SM5108

25. Drawbacks of Piezo-resistive Pressure Sensors-Results • Relatively low sensitivity • Large temperature dependence temperature compensation necessary

26. Capacitive Pressure Sensors • Inherently nonlinear output of the sensor • Distributed capacitance of read-out circuit requires low T amplifier Typical design: • parallel-plate capacitor • integrated electronics for signal processing • reference capacitors for temperature compensation

27. Advantages And Disadvantages Of Capacitive Pressure Sensors Over Piezo-resistive Sensors • Advantages: • Higher sensitivity • Long-term stability • Smaller temperature dependence • Disadvantages: • Non-linear output • More complicated manufacturing due to the integration of the compensation circuit and signal processing electronics to the sensor chip • Relatively high price

28. Optical Pressure Sensors Optical techniques typically employ a microsensor structure that deforms under pressure resulting in change in optical signal. Diaphragm-based sensors, for example, incorporate optical waveguides on the top surface.

29. Example Of An Optical Pressure Sensor

30. Simple Interferometer Sensor Production Process Attach optical fiber Difficulty is readout

31. Nanotube/Film Technology • Small • Strong • Conducting • But not too conducting • Elastic • Stick to some surfaces Can be used for Thermometers Heaters Strain gauges Capacitor plates Flow meters Turbulence detectors

32. Nanotube film AFM Image 1 micron

33. Helium liquid or gas flow Tinned Copper 4-terminal Resistance Measurement G10 (fiberglas) Nanotube Film Flow Sensor Test

34. Nanotube film “rope” test jig

35. Nanotube film “rope” R vs. T

36. Flow past a Nanotube film

37. Nanofilm CapacitiveFlow/Pressure Fluctuation Sensor AFM of Nanofilm Flow

38. The Group minus Shu-chen Liu Greg Ridvan Mario Yihui