Copasetic Flow

If you're new to the experiment, scroll to the bottom for background that will catch you up with what's going on. Liquid Nitrogen Fill The liquid nitrogen Dewar has been filled.  It’s initial and final weights were 146 and 170 pounds, respectively.  I’m guessing I must have read the initial weight incorrectly, but we may be paying too much for ’45 liters’ of nitrogen which might be closer to 13. liters/pound 0.5606 start 146 finish 170 net 24 Total Liters 13.4544 I’m doing the same measurement as yesterday with the sample immersed in liquid nitrogen.  There seems to be no change.  I have however invented a reasonably good vibration detector for the vacuum pump across the room, see video here . I’m going to try a new configuration of the two coils next.  Pancake coils will be constructed with one placed on each of the opposi...

If you're new to the experiment and need background, scroll down. I’m trying out the concept for the qualitative quench detector with a YBCO sample.   The prototype coils were wrapped directly on the YBCO sample.   The coils are constructed with manget wire.  The insulation on the ends of each coil was scraped off using a razor blade.  The brown material is just dense poster-board stock that provides a mounting frame for the coils. Without cooling the sample, (so that it remained in its normal state), an oscillating current was driven through the primary coil and read through the secondary.  The results were the same as might be expected with air core coils since the superconducting sample is not diamagnetic or ferromagnetic.  Tomorrow the same experiment will be run again with the sample in its superconducting state.  I expect to see a different x-y plot due to the superconducting samples expulsion of magnetic fields in i...

Lab Book 2014_12_30 Today I worked on getting a qualitative susceptometer up and running.  By qualitative I mean that we won't be attempting to analyze the returned data to accurately determine any characteristics of the superconducting materials that are to be studied, only the state of the materials, and the existence, or not of a hysteresis curve for the material. The why of it all I’m experimenting with a quick and dirty susceptometer that can be used with the hray experiment to determine when we’ve quenched the superconductor.  Today’s work is using a ferromagnetic core, not a superconductor.  The responses are similar and I don’t have to worry about cooling a superconductor. Experimental Setup Something old and something new I’m pressing a General Radio 1311-A audio oscillator and a Tektronix TDS 210 into service together. The general radio signal generator is being used to drive the coil surrounding the iron core.  The...

If you thought the history of physics was all about researching old papers and didn't involve lab work, a team at UC Berkeley begs to differ.  They recently published a paper describing their use of  passive radiation detection to identify what appears to be the first sample of plutonium large enough to be weighed.   The sample was made by Glenn Seaborg and his collaborators using large cyclotrons to bombard uranium with neutrons to transmute it into plutonium.  You can find the article at: http://arxiv.org/abs/1412.7590        

There's sooo much going on today.  I'm back in the lab again, but I'm also studying for the last little bit of my EM II class.   Here are the EM notes for today.  Hopefully, I'll get a lab book up again in the morning. Looking at the Leinard-Wiechert Potentials.   We'll have a particel mofin along hte path $\vec{r} = \vec{r_o}\left(t\right)$.  There is a quite lengthy explanation of IRFs, but I'll skip that for now and keep careful track of whether or not this comes back to bite me in the butt.  We define $\vec{R}\left(t^\prime\right) = \vec{r} - \vec{r_0}\left(t\right)$ which is the vector from the point charge at time $t^\prime$ to the observatin poitn $\left(\vec{r}, t\right)$.  This gives us a retarded time, $t^\prime$ determined by $t - t^\prime = R\left(t^\prime\right)$, where $R\left(t^\prime\right) = |\vec{R}\left(t^\prime\right)|$.  This makes far more sense if you translate one of the ever present ever invisible $1$s to a c to ge...

Just a few notes on how to proceed on the penultimate homework of the semester. We're to show that the solutions for the 30/60/90 triangular waveguide given in the last homework set will also work for a waveguide that's formed from an equilateral traingle.  The three corners of the equilateral traingle are located at $\left(x,y\right) = \left(0, 0\right)$, $\left(x,y\right) = \left(a, a/\sqrt{3}\right)$, and $\left(x,y\right) = \left(a, -a/\sqrt{3}\right)$. This falls out immediately from last week's homeowrk.  Because the sine function is peiodic in $\pi$ over the domain from $\left(-\infty, \infty\right)$, the solution given last week in terms of sines will still evaluate to zero on the wall that falls at negative $y$. coordites.  The positive $x$ coordinates of the functions will evaluate to 0 on the wall in the same manner they did before???  There's an issue here.  It's products of the $x$ and $y$ sinusoids that all sum to zero.  These will need t...

I was back in the lab this morning.  I’m working on getting the four point measurement to work on the YBCO sample.  In the grand scheme of things, this is low priority, but it’s important to know that we can successfully make these measurements here before we have a large bucket of liquid helium evaporating with a sample inside.  Here’s what the four point probe measurement looked like: There are still no conclusive results.  With any luck this is a consequence of me not being able to interpret the results more than a bad experimental setup.  The table below details the four point probe readings in ohms as the superconductor cools Table of four point readings Time Resistance kohm Comments 0 -0.35444 Negative reading is probably from swapped sense wires. 16 -0.36735 Immediately after nitrogen pour 59 -0.34466 Near minimum 101 ...