Copasetic Flow

A number of sources[2][3] today reported on the possible detection of dark matter particles or WIMPs from the CDMS II experiment.  This is pretty slick for a number of reasons.  First, one of the research teams on the CDMS II experiment is located right here at Texas A&M.  Second, the other dark matter experiment that's mentioned in the nature blog, LUX, also has a team of researchers working here at A&M.   I was sitting in a professor's office discussing using liquid helium as a scintillator for the h-ray experiment a few days ago and he mentioned their use of liquid xenon as a scintillator on LUX, and now this!  For those interested, liquid xenon makes a better scintillator than liquid helium for a few reasons.  The most interesting of these to me is that helium is small enough to penetrate into a photomultiplier tube and ruin it's vacuum over time.  Basically, it's very hard to keep helium from penetrating containers. What about...

I ran into the sources for today's post while searching for the answer to a great question posed by +Bruce Elliott  regarding yesterday's post [1] about flux pinning and stable superconductor levitation.  Bruce's question was: "...Of course, like any good post, it leads to more questions. So here's my next one: I would think that since the the induced currents resist any change to the magnetic field, that they would have an effect analogous to friction, i.e. any attempt to change the position of the conductor (or magnet) would be similar to moving an object through a very viscous fluid - hard to do, but once done, the object stays put in the new position. What we see in the NASA video, however, is that when the levitating magnet is poked, it oscillates slightly. This looks more like the motion of an object in a potential well, like a mass on a spring. This suggests that the superconductor "remembers" the equilibrium position (and the corresponding ma...

+Bruce Elliott  asked an excellent superconductor levitation question, so, no lab stuff, journal articles, or homework problems today, just superconductors.  A few days ago, I posted the following video of eddy current levitation to Google + with this explanation... Staying with the eddy current theme, what if you played the game a different way?  The video below shows a coil of wire driven by wall current, (60 Hz here in the USA).  The alternating current creates a rapidly changing magnetic field.  The eddy currents in the aluminum plate, (aluminum like copper is not magnetic), oppose the original magnetic field created by the coil and cause it to levitate.  The coil gets very, very hot in the process because of all the energy from the wall current being turned into heat by the electrical resistance of the coil, (video 1). http://youtu.be/5HnihTg1rso What the post and video are demonstrating is a combination of Faraday's Law of In...

After yesterday's attenuation calculations, I'm trying to find out if I can place the scintillator directly into the liquid helium Dewar to avoid the attenuation of flux due to the Dewar walls and solenoid windings.  I came across an interesting article that was a portion of Fernand Bedard's PhD dissertation in 1956.  It's interesting for lots of reasons.  First, Bedard was working with Hans Meissner.  Second the article mentions currents across insulating junctions with superconductors on either side in 1956, several years before Josephson would do his Nobel prize winning work on Josephson junctions.  Finally, Dr. Bedard wound up working for the NSA! Then, there's the pragmatic stuff.  It looks like they did place their NaI crystal in the Dewar.  The article also mentions that they were able to load 2 liters of liquid helium using only 5.5 liters.  They apparently lost only 3.5 liters to boil off!  The article also has an excelle...

I received detailed plans for the liquid helium Dewar that's going to be used in the h-ray experiment yesterday and spent some time calculating the amount of attenuation we can expect to the x-rays theoretically produced by our quenched Pb superconductor.  I'm making the assumption that most of the attenuation of x-ray flux will come from the aluminum walls and aluminum backed insulation, not from the plastic walls.  A cross-section of the walls is shown to the left, (picture 1).  The wall on the left of the cross-section is made of .125 inch thick aluminum.  The five sheets of insulation between the inner and outer walls are Mylar coated with .003 inch thick aluminum.The inner wall on the right hand side of the cross section is constructed of .1 inch of 'low thermal conductivity plastic'.  This gives me a grand total of 0.35 cm of aluminum between the source and the   detector.  The graph shown below...

More interesting ideas have come up in the last few days than I have time to pursue.  I'm capturing them here with a brief synopsis of each and a few pointers to documents so you can read more about it and I'll remember where to find it later. We attended the  +American Physical Society  TX Section meeting last weekend in at Tarleton State Univesrity in Stephenville, TX.  I say we because it was my wife, the PhD physicist in the family, my brother-in-law, a physics grad. student and me.  I great time was had by all. I got to see a second presentation of the  new approach to the Schrodinger equation presentation given by Dr.Schlich at Texas A&M last week.  This version was given by Dr. Scully of A&M[1][2].  During the talk, Dr. Scully   mentioned two things that caught my ear as I was preparing the slides from my talk, (apologies Dr. Scully.)  They were, the Bohmian potential and a paper where he mentioned they had s...

I'd hoped I was going to be able to make an authoritative swoop through the oft-mentioned, (here anyway), AJP article by Shubaya and Wulfman[1] wherein they explain how the accidental degeneracy in the hydrogen atom energy solutions can be visualized by looking at the accidental degeneracy in the corresponding two dimensional problem of orbits around a Coulomb potential.  Unfortunately, about half-way through, I realized I'm still not quite there.  Here's what I have so far.  I've cleared up exactly what the definition of the accidental degeneracy is.  There's a more complete grasp on the skeleton of Shubaya and Wulfman's argument here, as well as what 'projection to a +1 dimensional space' actually means. The Accidental Degeneracy  In the hydrogen atom there are two kinds of degeneracy with respect to energy.  The first kind is related to the quantum number m and is expected.  It has to do with...