em project squid

8/13/2019 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

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