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Diffstat (limited to 'supcon.tex')
| -rw-r--r-- | supcon.tex | 10 |
1 files changed, 5 insertions, 5 deletions
@@ -3,7 +3,7 @@ \chapter{Superconductivity} - \textbf{Experiment objectives}: study behavior of a high temperature superconducting material + \textbf{Experiment objectives}: study the behavior of a high temperature superconducting material Yttrium-Barium-Copper-Oxide (YBCO, YBa$_2$Cu$_3$O$_7$) in magnetic field, measure the critical temperature for a phase transition in a superconductor. @@ -16,7 +16,7 @@ quantum mechanics. Basically, when atoms form a solid, the atomic levels of the electrons combine to form bands. That is, over a finite range of energies there are states available to electrons. Since only one electron can occupy a given state, as described by the {\bf Pauli Exclusion Principle}, electrons will fill these states up -to some maximum: the Fermi Energy: $E_f$. A solid is a metal if it has an +to some maximum: the Fermi Energy, $E_f$. A solid is a metal if it has an energy band that is not full. The electrons are then free to move about, making a metal a good conductor of electricity. If the solid has a band that is completely full, with an energy gap to the next band, that solid will not @@ -38,7 +38,7 @@ dissipation. at 35 K. Several groups later discovered materials that would superconduct at temperatures up to 125 K. These materials are called high temperature superconductors (HTS). Their discovery - was a breakthrough, because this means that these + was a breakthrough, because it meant that these superconductors will work in liquid nitrogen (at 77 K), which is relatively cheap and abundant. @@ -130,7 +130,7 @@ temperature falls below critical. resistances. Connect a voltmeter (with 0.01 mV resolution) to the yellow wires. Connect a current source through an ammeter to the {\bf black} wires. Place a current of about 0.2 Amps (200 mA) - through black leads. Note: {\bf DO NOT EXCEED 0.5 AMP!!!!} + through the black leads. Note: {\bf DO NOT EXCEED 0.5 AMP!!!!} %On the % Elinco power supplies, you hardly have to turn the knobs at % all! @@ -140,7 +140,7 @@ At room temperature, you should be reading a non-zero \begin{enumerate} \item With the voltage, current and thermocouple leads attached, carefully place the disk in the container. Pour liquid nitrogen into the - container. Wait until temperature reaches 77 K. + container. Wait until the temperature reaches 77 K. \item With tweezers, take the disk out of nitrogen and place it outside of the container. {\bf Start quickly recording the current, voltage and thermocouple readings as the disk warms up.} When superconducting, the disk should have |