Small Sensors at Low Temperature Revealing Cryogenic Turbulence University of Florida Physics Gary...
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Transcript of Small Sensors at Low Temperature Revealing Cryogenic Turbulence University of Florida Physics Gary...
Small Sensors at Low TemperatureRevealing Cryogenic Turbulence
University of Florida PhysicsGary Ihas-
Yihui Zhou Ridvan Adjimambetov Shu-chen LiuIsaac LuriaMario Padron
Miramare June 10, 2005
Andrew RinzlerJennifer Sippel-Oakley
Mark Sheplak-University of Florida EngineeringT. ChenVadim Mitin-V. Lashkarev Institute of Semiconductor Physics, NASU, Kiev, Ukraine Funding: Research Corporation
Thank you Mr. Organizer
In his lab circa 2004 (with research trainee)
Thank you Mr. Director
In his lab circa 2005
Thank you Mr. Helium Vorticity
50th Anniversary of First Direct Detection of Quantized Vorticity
Outline 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
Characteristics of turbulent flow
[H. Tennekes, 1983]
1. Irregularity — randomness
2. Diffusivity — rapid mixing and increased rates of momentum, heat and mass transfer
3. Large Reynolds numbers
4. Three-dimensional vorticity fluctuations
5. Dissipation — due to viscous loss; decaying rapidly without energy supply
6. Continuum — even smallest scales >>molecular length scale
e forceviscous forceinertial
ULR
Large Scale Turbulence
JPL
Intrepid Experimentalist
A Matter of Scale
Water Facility of Nikuradse
R=107
Oregon Cryogenic Facility
[H. Tennekes, 1983]
Grid TurbulenceGrid turbulence in a classical fluid [Frisch, 1995]
Eddy motion Larger length scaleSmaller length scale
(wavenumber, k > inverse of vortex line spacing, )1
(the mesh of grid the size of the channel)
Energy dissipation by viscosity (Re ~ 1)
Energy flow rate
Energy input
Dissipa-tion
1~ k
k
dt
dE
inertial regimeRe >> 1
Kolmogorov Spectrum
3/53/2)( kCkE
Two Fluid Model– Landau -1941
[J. Wilks, 1987]
Viscosity (P)
4He
(oscillating disc viscometer)
56 %
Fluid density
0 2.0 T
T (K)
n
s
=n +s
0.14g/cm3
Sn=SHe = n nnormal fluid
Ss =0s =0
irrotational
sSuper-fluid
Two fluids
entropyviscositydensityTwo Fluid model
0 s
Quantization of superfluid circulation:
scmnm
nhds / 1097.9 24
(postulated separately in 1955 by Onsager and Feynman)
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]
1. Circulation round any circular path of radius r concentric with the axis of rotation=2r2
2. Total circulation=r2n0h/m (n0: # of lines per unit area)
3. n0=2 m/h=2 /
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
s
2
Quantization of Superfluid Circulation
Cryogenic Towed Grid Apparatus
Dimensions in inches
Superconductingsolenoid
Niobiumcylinder
Grid Liquid Helium
Drive Simulation
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
Requirements for the thermometers
Two excellent candidates1. Neutron transmutation doped Germanium Bolometer-- [N. Wang, 1988]
sensitivity (rms energy fluctuation 6 eV at 25mK); T/T ~ 4.810-6
response time < 20 ms size: 1mm1mm0.25mm
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
1. Operating temperature: 10 - 100mK.
2. Sensitivity: T ~ 10-7K, or T/T ~ 10-5.
3. Short response time: t ~ 10-3 s.
4. Small mass & good thermal contact.
Conduction in a doped semiconductor
1 10 10010
100
1000
10000
100000
1000000
Electron Collisions
(R~T-1)
Phonon Collisions
(R~T-1/2}
Variable Range Hopping
(R~exp{T-1/4})
Coulomb Interaction
(R~exp{T-1/2})
Re
sist
an
ce ()
Temperature (K)
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
1 10 10010
1
102
103
104
Re
sis
tan
ce,
Oh
ms
Tem p erature, K
Advantages of Thin Film Technology
Semiconductor Chip Technology
Ge/GaAs thermistors 300 m square by 150 m thick. Mass of the thermistor = 7.2 10-5 gram.
Active layerInsulator
Thermistor R vs. T Development Work
10 100 10001
10
100
1000
#3
#2
#1
Th
erm
isto
r re
sist
ance
(K
oh
m)
Temperature (mK)
http://microsensor.com.ua/products.html
Pressure Transducer Requirementssampling on micron scale sensitivity: 0.1 Pascal fast: 1 msecfunction at low temperatures (20 – 100 mK) transduction: as simple as possible
MEMS Technology Pressure Sensors Piezo-resistive Capacitive Optical
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
Piezo-resistive Pressure Sensor SM5108
Manufactured by Silicon Microstructures, Inc.
Semiconductor resistors joined by aluminum conductors in bridge configuration
Resistors placed on diaphragmTwo strained parallel to ITwo strained perpendicular to I
Piezo-resistive Pressure Sensor SM5108
Drawbacks of Piezo-resistive Pressure Sensors-Results Relatively low sensitivity Large temperature dependence temperature
compensation necessary
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40
5
10
15
20
25
30
35
40
45
50
55 300 K 91.2 K - 94.6 K 64.4 K - 66.0 K 49.8 K - 51.0 K 40.4 K - 43.5 K 29.9 K - 30.4 K 22.9 K - 26.0 K 26.2 K
Voltage vs Pressure for Piezoresistive Transducer at varying temperatures
Vo
ltag
e (
mV
)
Pressure (Bar)
Capacitive Pressure Sensors Inherently nonlinear output of the sensor Distributed capacitance of read-out circuit
requires low T amplifierTypical design: parallel-plate capacitor integrated electronics for signal processing reference capacitors for temperature compensation
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
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.
Example Of An Optical Pressure Sensor
Simple Interferometer Sensor
Difficulty is readout
Production Process
Attach optical fiber
Nanotube/Film Technology•Small•Strong•Conducting•But not too conducting•Elastic•Stick to some surfaces
Can be used forThermometersHeatersStrain gaugesCapacitor platesFlow metersTurbulence detectors
Nanotube film AFM Image
1 micron
Helium liquid or gas flow
TinnedCopper
G10 (fiberglas)
4-terminal ResistanceMeasurement
Nanotube Film Flow Sensor Test
Nanotube film “rope” test jig
Nanotube film “rope” R vs. T
0.01 0.1 1 10 1001000
10000
100000R
(oh
ms)
T(Kelvin)
Flow past a Nanotube film
0.0 0.1 0.2 0.3 0.4870
872
874
876
878
880
882
884R
film ()
Flow (cubic feet/hour)V (mm/sec)
Nanofilm CapacitiveFlow/Pressure Fluctuation Sensor
AFM of Nanofilm
Flow
The Group minus Shu-chen Liu
Mario Yihui
GregRidvan