Em Project Squid
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Transcript of Em Project Squid
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Superconducting Quantum
Interference Device(SQUID)Magnetometer
SMES 2206Electricity & MagnetismKetua Kumpulan: Yeow Jia Jun
Ahli Kumpulan: Tay Szi Yiing
Ong Yern Yee
Mohamad Zarin
Nama Pensyarah: Dr. Chiu Wee Siong
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SQUID
Magnetometer
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Schematic Diagram
10. Dewar Isolation cabinet
11. Dewar
12. Printer13. Magnetic power supply
14. Temp. controller
15. Console Cabinet
16. Power distribution unit
17. MPMS controller
18. Gas/Magnet control unit
19. Computer
20. Monitor
*MPMSMagnetic Property
Measurement System
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Whats inside the Dewar
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Superconductivity
It is a phenomenon of exactly zero electrical
resistance and exclude magnetic fields
exactly, occurring in certain materials when
cooled below a certain temperature known
as critical temperature, Tc.
A magnetlevitating above a
high-temperature superconductor,
cooled withliquid nitrogen.
Persistent electric current flows
on the surface of the
superconductor, acting to exclude
the magnetic field of the magnet
(Faraday's law of induction).
This current effectively forms anelectromagnet that repels the magnet.
Heike Kamerlingh Onnes
http://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/High-temperature_superconductorhttp://en.wikipedia.org/wiki/Liquid_nitrogenhttp://en.wikipedia.org/wiki/Faraday's_law_of_inductionhttp://en.wikipedia.org/wiki/Heike_Kamerlingh_Onneshttp://en.wikipedia.org/wiki/Heike_Kamerlingh_Onneshttp://en.wikipedia.org/wiki/Heike_Kamerlingh_Onneshttp://en.wikipedia.org/wiki/Heike_Kamerlingh_Onneshttp://en.wikipedia.org/wiki/Heike_Kamerlingh_Onneshttp://en.wikipedia.org/wiki/Faraday's_law_of_inductionhttp://en.wikipedia.org/wiki/Liquid_nitrogenhttp://en.wikipedia.org/wiki/Liquid_nitrogenhttp://en.wikipedia.org/wiki/Liquid_nitrogenhttp://en.wikipedia.org/wiki/High-temperature_superconductorhttp://en.wikipedia.org/wiki/High-temperature_superconductorhttp://en.wikipedia.org/wiki/High-temperature_superconductorhttp://en.wikipedia.org/wiki/High-temperature_superconductorhttp://en.wikipedia.org/wiki/Magnet -
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SQUID Magnetometer
There are 4 main components:1. Superconducting Magnet
2. Superconducting Detection Coil
3. SQUID
4. Superconducting Magnetic Shield
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Superconducting Magnet
A solenoid made of superconducting wire
Must be kept at liquid Helium temperature
Produce magnetic field in range of 518 Tesla
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Superconducting Detection Coil
Single piece ofsuperconducting wireconfigured as second-
order gradiometer This pick-up coil system
is placed in the uniform
magnetic field region ofthe sinusoidalsuperconducting magnet
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SQUID
A thin film that functions as extremelysensitive current-to-voltage converter.
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Superconducting Magnetic Shield
Shield the SQUID sensor from fluctuations of
the ambient magnetic field of where
magnetometer is located and from the large
magnetic field produced by the
superconducting magnet.
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Materials
Superconducting materials for SQUID
Traditionally, made of pure niobium or a lead alloy with 10% gold orindium.
Pure lead is unstable when its temperature repeatedly change.
To maintain superconductivity, the device is operated within a fewdegrees of absolute zero, cooled using liquid helium
Now, made of high-temperature superconductors, YBCO (YttriumBarium Copper Oxide)
To maintain superconductivity, the device is cooled using liquid
nitrogen, which is cheaper and easier to handled than liquid helium
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Electronic control box
(two 9 V batteries are
included)
Probe with
the SQUID
sensor
Liquid
nitrogen
dewar
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Liquid nitrogen
dewar
Probe with
the SQUID
sensor
Electronic
control box
(two 9 Vbatteries are
included)
Output device or
oscilloscope
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How to use SQUID magnatometer?
Step1 :set up the
apparatus.
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Step 2:
Add liquid nitrogen
-Fill the dewar about 3/4-full
with liquid nitrogen.
-Refill when necessary.
Nitrogen will decrease due
to evaporation.
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Attention
DIRECT SKIN EXPOSURE TO LIQUIDNITROGEN CAN CAUSE
SEVERE BURNS.
Wear eye protection and gloves.
Be careful when handling the
nitrogen liquid
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STEP 3: Cooling down the probe
-Lower the probe into
the dewar.
-Wait a few minutes so
that the probe achieve
stable temperature of
77K.
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STEP 4:
Connect the
probe and
theelectronic
control box
with the
cable
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How SQUID converts magnetic flux
into voltage?
1)A sample is put into the probe.2)The magnetic field of the sample
applies on the superconducting coil
inside the probe..
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3)According to Lenzs law, an current
is induced to oppose the change.
4)Induced current flow around theloop.
5)The supercurrent has its magnetic
field that cancel out the appliedmagnetic field from the sample.
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6)Supercurrent flow. There will bepotential difference in the loop.
7)Therefore ,the magneticproperties of the sample is
amplified into a measurable
voltage.
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Theory of the mechanism of SQUID
1. What is Josephson junction?
2. What is supercurrent? How it happen?
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Josephson junction
superconductorinsulatorsuperconductor
junction where an electric current (Cooper pairs)
flows through quantum tunnelling. Cooper pairingis a quantum effect. An electron
attracts positive (+ve) ions toward it, the +ve ions
attract other electrons, and cause them to pair
up. (not necessarily close together)
The energy of the pairing interaction is quite
weak (103eV), at low temperatures.
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Quantum tunnelling
refers to the quantum mechanicalphenomenon where a particle tunnels
through a barrier that it classically could not
pass through.
Related with Heisenberg uncertainty principle,
thewaveparticle duality
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Supercurrent Wrong concept: T, R .
normal conductor (copper) superconductor normalconductor, electric current = fluid of
individual electronsmoving & collidingwith
the ions in the lattice
Superconductor, consists of bound pairs of
electrons (Cooper pairs), not scattered by the
lattice & flow without energy dissipation
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Application Of SQUID
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A SQUID
(for superconducting quantum
interference device) is a very
sensitive magnetometer used tomeasure extremely
subtle magnetic fields, based on
superconducting loops
containing Josephson Junction.
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1. Magnetoencephalography (MEG)
uses measurements from an array of SQUIDs
to make inferences about neural activity
inside brains Because SQUIDs can operate at acquisition
rates much higher than the highest temporal
frequency of interest in the signals emitted by
the brain (kHz), MEG achieves good temporal
resolution.
2. Magnetic Property Measurement Systems
(MPMS)
These are turn-key systems, made by several
manufacturers, that measure the magnetic
properties of a material sample.
This is typically done over a temperature
range from that of 4 K to roughly 190 K,
though higher temperatures mean less
precision.
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3. Scanning SQUID microscope
uses a SQUID immersed in liquid helium as
the probe.
The use of SQUIDs in oil prospecting, mineral
exploration, earthquakeprediction and
geothermal energy surveying is becoming
more widespread as superconductor
technology develops.
they are also used as precision movement
sensors in a variety of scientific applications,
such as the detection of gravitational waves