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Showing posts from March, 2013

Notes on Superconducting Intermediate Sates, and Shubnikov De Haas Oscillations

This is just a series of rather scattered notes on things that I need to keep in mind for the h-ray experiment as well as things that are going on in class this week and how they're not that disconnected.

Shubnikov, who I've mentioned before[1], (picture 1), in reference to the intermediate state of superconductors, came up in quantum mechanics class this week.  The topic of discussion was Shubnikov-DeHaas oscillations.  These are oscillations of the resistance of a material with respect to the strength of the magnetic filed it is exposed to.  It occurred to me the the graphs of the oscillating resistance[2], (picture 2 below), looked a bit like magnetron operation because at low magnetic fields nothing much happened due to the field being too low to bend the electrons into a complete orbit.


A little more searching and reading revealed I wasn't necessarily the only person who ever thought so.  I came across an article about the intermediate state of superconducting tin …

Adding A JavaScript Controlled Google Plus Interactive Post Button

While learning all about adding a Google+ sign-in button, I noticed a new Google+ sevice, the interactive post.  An interactive post is the same as a normal Google+ post with the addition of a button that performs some 'action' on the target web site.  For an example Google+ interactive post, look here[4].  The Copasetic Flow web sites don't lend themselves to most social networking APIs, there's nothing to buy here yet, and there's no music or movies, but it occurred to me that there is somethinng to watch, the APRS tours[1].  Finally, I have an excuse to play with a social networking API!

The mechanisms for using Google+ interactive posts are fairly well described by Google on their docuementation page[2], so I won't walk you back through that.  Where I ran into a few simple problems, (two to be exact), was with trying to influence the post contents using JavaScript.

First, when trying to write to a button on the fly[3] using gapi.interactivepost.render(), I…

Notation and Cryostat Design

I took the first look at the cryostat that is probably going to use for the hole theory of superconductivity experiment.  A cryostat is a vessel for holding a coolant or cooling system, (in our case, liquid helium), and the equipment/samples for an experiment.  Because helium transitions from a liquid to a gas at just over four degrees Kelvin, the cryostat has two walls separated by a vacuum space to insulate the liquid helium inside from the room level temperatures outside, just like a thermos.

Before I get to much further into the details of the cryostat, I'd like to coin a phrase.  As those of you who already read the proposal for the experiment[1] know, Dr. Hirsch of UCSD has proposed a new model for superconductivity[2], and one of the predictions made by that model is that superconductors will emit Bremsstrahlung radiation[3] when they are quenched back into their normal non-superconducting state.  It's getting to be a bit much to type Bremsstrahlung all the time, or th…

Magnet Design and Sample Size

I've been looking lately at using an already constructed superconducting magnet instead of building my own for the upcoming experiment, (an Experimental Search for the Bremsstrahlung Radiation Predicted by the Hole Theory of Superconductivity)[1].  The issue at hand is that the bore isn't large enough to accept the originally planned 3.8 cm radius spherical Pb sample.  I took a look this morning at what reducing the sample size would do to the energy of the predicted radiation in electron volts as well as what the dependency of the radiation flux would be with respect to sample size.  The two formula for the energy and the flux (pictures 1 and 2) are:



See the aforementioned proposal as well as reference 2 for more details.

Plotting each of these versus R, the radius of the sample gave the following plots, (pictures 3 and 4).  If the radius is reduced all the way down to 2 cm, the fall off in energy isn't unacceptable.  It still lands in the ballpark of 160 keV which should…

Adding Google+ Sign-In to a Web Site

I just added Google+ sign in to the Copasetic Flows ham radio license exam practice site[2].  Unlike friend connect from Google which ultimately disappeared, it was pretty easy!  I used the instructions at Google Plus Daily[1].  The instructions there outline in a very  nice and very complete way how to get sign-in up and working using only JavaScript.  They also demonstrate how to access user information using JavaScript.  The insructions worked very well for me with a few notable exceptions that I'm cataloging here before I forget:

1.  In step 2, adding a sign-in button, I had to add a span around the button html with an id of 'signinButton' to get the button to properly disappear upon login.

2.  The last line of the disconnect code had to be commented out since revokeButton didn't exist in my html.

3.  The profile information code didn't quite work for me.  It's not that it's necessarily bad code so much as it employed bits of Javascript that I'm no…

The Week in Preview, March 25th 2013

A quick review of what I'll be looking at over the course of the upcoming week.  This is as much to get my own thoughts in order as anything else.

Quantum Mechanics: I'll be working on still more uncertainty and harmonic oscillator problems in QM this week.  What a surprise right :)  Specifically, this week, I'll be calculating matrix elements for both position and momentum squared using both the Hermite polynomial recursion operators and the ladder operators.  These are covered in chapters 5 and 10 in Merzbacher.  I was playing around with one of the recursion relations (picture 1)


 for Hermitian polynomials earlier in the year and wound up with the following kind of interesting table.  You can see the n level of the wave function moved out of the way by the successive application of the recursion formula which amounts to the successive application of the x operator, or a sum of the raising and lowering operators (picture 2).

I know a lot of students, (including me), that …

The Appearance of Dilated Time

I've written a bit lately on the appearance of objects moving at relativistic speeds[6].  There are some very intersting non-intuitive results.  For example, a Lorentz contracted sphere will still look, (visually), like a sphere, not an ellipsoid, (see Penrose, Teller, and Boas)[1][2][3].  It turns out there's an analogous phenomenon in realtion to time dilation.

Yesterday over at my ChipDesignMag column[4] I mentioned Brian Greene's explanation of time dilation from his book "Fabric of the Cosmos"[5].  In that description he mentions that if Lisa, who didn't change her velocity  looked at Bart's watch as he sped away, she would see his watch moving more slowly because of time dilation.  Well, sort of.  It is true that Bart would be moving more slowly through time, but if Lisa could look at Bart's watch, that's not necessarily what she would see.  In this month's Physics Teacher, Frank Wang[7] of LaGuardia Community College points out that if …

The Magnetron Part II: Did I Mention Yagis?

For that matter, did I mention magnets?  Magnetrons need magnets!  The magnetic field causes the electrons emitted by the hot cathode in the center of the tube to travel in circular orbits on their way out to the circular can shaped anode.  The ,(generally), iron-cored magnet required is the reason your microwave oven is as heavy as it is.  Which brings us back to Yagi.  There's a picture of the magnet he used in his microwave transmission research below. The magnet is the bulky looking cylindrical shaped object in the back.

The next reference I foudn in the MIT Radiation Labs microwave magnetron handbook was to Yagi[1].  For the ham radio foks, yes, that Yagi!  The Yagi of Yagi-Uda beam antennas.  The handbook mentioned that whhile the cyclotron magnetrons of the type discussed yesterday were  enerally 'feeble in their output abilities, some people like Yagi had put them to fruitful use.

For the non-ham radio initiated, a Yagi Uda antenna is a type of radio antenna developed …

The Magnetron's Heritage and Progeny

I'm still catching up from the midterm yesterday.  Consequently, today's post is just a few brief scattered history of physics/engineering notes inspired by a ham radio license exam question.  The extra class ham radio exam asks: "What is a magnetron oscillator?"  The simple answer is "A UHF or microwave oscillator consisting of a diode vacuum tube with a specially shaped anode, surrounded by an external magnet"... But wait, there's way more!

The first reference I found to the magnetron was in relation to radar systems in volume six of the MIT Radiation Laboratories Series "Microwave Magnetrons".  The series of books accumulates all the knowledge gained at MIT during the war time development of radar.  This is the same MIT Radiation labs where David Tressel Griggs was piloting radar test flights in  the plane he purchased with the insurance settlement from his car crash with Agnew Hunter Bahnson, (it's a bit of a long story[2]).  The refer…

Lorentz Contraction, Accidental Degeneracy, and Coherent States

This is just a quick note since once again I have midterms.  I found what may be my favorite issue of the American Journal of Physics ever!  Here are short summaries of the three awesome articles from the July 1965 issue.

Lorentz Contractions
I've been doing a lot of reading on time dilation and Lorentz contractions lately.  Penrose[1], Terrell, and Boas all wrote articles in the later '50s/early '60s about the fact that a sphere moving at relativistic speeds won't look contracted.  It's outline will still be that of a sphere.  In 1965, Scott and Viner[2] followed up on this work with an article that provided, (to my thinking), a far easier way of visualizing what's going on than the other three.  They showed what a piece of graph paper and a set of boxes would look like when observed moving near the speed of light.  For an open access version of the math behind the article see this excellent web page on Terrell rotations[3].  The short version of the story runs…

Wilkinson Power Divider

And now for a little applied physics!  The Wilkinson power divider shown to the left schematically (picture 1), is a cool little circuit that evenly divides a microwave signal at a specified design frequency and supplies it to two or more circuits downstream from itself.  In addition to evenly dividing the applied power from the source, the Wilkinson divider also protects each of the circuits it supplies from any reflected signals from the other supplied circuits.  The circuit design was first published in 1960 by Ernest Wilkinson[1].

A simplified diagram of the circuit is shown below.  It divides the input from the source down two conductors that are each cut to be exactly as long as one quarter of the wavelength of the microwave signal supplied by the source.  The power is automatically divided due to one of the properties that physicists love: symmetry.  Faced with no difference in the two paths it's presented with, the input microwave signal splits and half of its power trave…

Separated at Birth? Quantum Mechanics and Electrical Engineering Systems Analysis

I've been working on a history project peripherally for months, I'm just recording a few notes here as I still haven't gotten to the bottom of it.  Because I haven't arrived at the answer to my research yet, the following will ramble on a bit, but I wanted to capture my notes so far.  You see, my old electrical engineering courses keep creeping into my quantum classes and vice versa.  It's not that it's just the same math, it's also the same notation.  The ultimate answer to all of this may be that both subjects pulled their notation from pure mathematics.

The latest inspiration for really looking into this came up as I was studying for my quantum midterm yesterday. I came across the following integral in Merzbacher that I felt certain I'd seen before (picture 1).  Merzbacher certainly felt it should be familiar since not a bit of explanation was given for its execution.


When I got home, I pulled out my EE systems engineering book, "Discrete Time a…

Ideas for Physics Outreach and Maps

Google is offering grants for between 10 and 20 thousand dollars for outreach work utilizing geographic mapping web applications[1].  The deadline for proposals is April 18th[2].  So, here's the question.  As physicists, is there any kind of outreach that we could do utilizing any or all of the Google map frameworks[3]?

Could we work with the +American Physical Society and/or the +Society of Physics Students to map historical events in physics around the world?  Perhaps an app similar to AT&Ts Air Graffiti[4] that would automatically display events in physics history on your smartphone when you neared a location would be cool.  Maybe it would be useful to index all the papers in PROLA by university so when you visited a school, you would automatically be served a list of papers published there.  A searchable map of outreach activities as well as physics colloquiums, workshops, and meetings would be handy.

Geographically enabled citizen scientist crowdsourcing data collection…

Arctan sin Taylor but Pretty

The Hodograph and Mamikon's Theorem

Just a quick note today on a fun article[1] and a new word, (hodograph), I found in the American Mathematical Monthly journal from the +Mathematical Association of America .  The article uses Mamikon's theorem to prove Kepler's second law.  Mamikon's theorem states that the area swept out by the velocity, (tangent), vector to a parameterized position position curve is the same as the area swept out by the same set of velocity vectors if you laid them out with a their tails all placed at a common center.  The curve swept out by all the velocity vectors with their tails placed at the same point is called the hodograph and was defined by W. R. Hamilton.  The hodograph in this scenario defines the acceleration curve for the particle!  Haimlton's article defining the hodograph can be found freely available at http://www.jstor.org/stable/20489607. [2]





References:
(2013). Visual Angular Momentum: Mamikon Meets Kepler, The American Mathematical Monthly, 120 (1) 71-73. DOI:

Intermediate State of Superconductors

I've been following a literature search for the last few days that's led to a very interesting point.  Superconducting tin has different quench points, (via magnetic field), depending on the orientation of the direction of current flow in the sample and the direction of the applied external magnetic field[1].  My next job will be to determine if Pb has the same qualities, and if so what that means for the experiment.

Pb was chosen as the sample for our experiment because of the relatively low magnetic field strengths at which it can be quenched.  It was mentioned by Hirsch in one of his articles predicting Bremsstrahlung radiation from quenched superconductors that the super conductor should be quenched 'quickly'.  It's unclear at the moment what effect this squirmy quality of supercurrents vs. magnetic field orientation will have.

Flow of the Literature Search:
And now, just a few notes on how I arrived at the Shubnikov article.  Hirsch who originated the theory t…