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Showing posts from May, 2014

The Superconductor Hole-Electron Asymmetry of Hirsch

What follows is an explanation of a phrase that Hirsch uses in most of his papers, “hole-electron asymmetry of condensed matter”.  The explanation was adapted from one of Hirsch’s papers[1], that can be found on arxiv as well as Phys. Rev . B. Here’s a more complete derivation of the London penetration depth from the London Moment field equation mentioned below.[2] Hirsch frequently refers to the ‘hole-electron asymmetry of condensed matter’.  In the article entitled “Electron-hole asymmetry and superconductivity”, he provides a nice picture of exactly what he means by this phrase.  I adapted the explanation for a presentation I’ll give soon on the H-ray theory.  The slides follow.  A more complete and texty explanation can be found at the link above.  The text that follows below is the very rough draft of some of the vernacular for the presentation.  For those who are die-hard fans of watching people fumble with practice presentations, I've also posted the first run-through of th…

Special Update: Congress to vote on STEM funding for NASA and the NSF today

Congress to vote on STEM funding for NASA and the NSF todayThe House of Representatives is voting on science funding of both NASA and the National Science Foundation, (the guys that pay my paycheck), today.  If you like to read the bill, it can be found at::
http://docs.house.gov/meetings/SY/SY15/20140313/101907/BILLS-113HR4186ih-HR4186FrontiersinInnovationResearchScienceandTechnologyActof2014.pdf

If you'd like to contact your Congressperson to help out, +APS Physics  has setup a handy 'find your congressman' app at  http://www.congressweb.com/apspa
I called my representiative, Bill Flores and spoke with a very helpful and friendly staffer.  No fuss, no muss.
If you wonder what to say, the APS has ideas for you, read on for a sample email and phone call script:
Sample E-mail
Dear Representative X,
My name is [YOUR NAME], and I am a physicist from [City, State] and a constituent of [Rep. Congressperson]. I work at [Institution] in [City, State]. 
I am writing to ask that you s…

Lab Book 2014_05_27 Special Relativity, Proper Acceleration, and Magnet Prep

Meetings, Magnets, and Special Relativity Spent the morning attending a meeting and getting to do just a tiny little bit of special relativity research, regarding proper acceleration in the instantaneously moving rest frame.  The rest of the day was spent debugging, first the liquid nitrogen Dewar, and then the leak detector.  The leak detector is still not up to snuff.  Prep work was done for lifting the magnet that will supply the quenching field for the superconducting samples.

New to these posts?
The hole theory of superconductivity, a BCS compatible modle, predicts that when a superocnductor is brought back to its normal state quickly, it will emit x-rays.  We plan to experimentally verify this or set a new lower limit for its detection.  Scroll to the bottom for more complete information of what this physics experiment is about and what we hope to achieve.
Relativistic range work:
Reviewed and followed Brehme’s derivation of proper acceleration and its meaning.  Proper acceleratio…

LabBook 2014_05_26 Superconductor Quenching Magnet Chilling Supply and Leak Detector Testing

Superconductor Quenching Magnet Cooling Supply Work The magnet that will be used to quench the superconductor in our experiment is water cooled.  So is its power supply.  The water chiller that will provide the cooling was checked out and filled.  The plumbing to the supply was constructed and tested.  Two of the water lines required SwageLocks rather than Parker fittings to prevent leaks. The superconducting sample is to be placed in a liquid helium Dewar during the experiment.  Work is being done to check the status of a second Dewar that can be used as a backup to the first.  At present, the leak detector for this work is not functioning properly.  Some time was spent on debug of the system with no conclusive answers found.
New to the game?  Scroll to the end for background on what this is all about.

Leak Detector Debug
Looking into why the leak detector no longer pulls down to < 10^-2 Torr quickly, (at all?).  Cleaned the liquid nitrogen trap which did have a little bit of pump …

Lab Book 2014_05_24 Electrical and Cooling Work

Summary
Prep work for magnet power supply testing was done today.  A three phase switch box was wired along with an extension cord to reach from the switch box to the power supply.  The input side of the water chilling system was constructed complete with a flow meter.  Only the output side setup remains.

Background
Hirsch's theory of hole superconductivity proposes a new BCS-compatible model of Cooper pair formation when superconducting materials phase transition from their normal to their superconducting state[1].  One of the experimentally verifiable predictions of his theory is that when a superconductor rapidly transitions, (quenches), back to its normal state, it will emit x-rays, (colloquially referred to here as H-rays because it's Hirsch's theory).

A superconductor can be rapidly transitioned back to its normal state by placing it in a strong magnetic field.  The experiment being performed proposes to look for H-rays emitted by a Pb superconductor when it is quench…

Photomultiplier Tube History and the Bell Laboratories Record

In our experimental search for H-Rays, we're using a NaI crystal attached to a photomultiplier tube, (PMT),  to detect the predicted x-ray radiation.  While studying up on photomultiplier tubes[1] this week, I came across quite a few interesting historical points.  Among these are:
1.  PMTs were first invented for use in movie theatre projectors to provide the sound tracks.
2.  Equipotential lines were important for design, but computers for the necessary didn't exist yet.  The lines were mapped by stretching thin rubber sheets over wood block models of the electrodes and rolling small balls along the sheets to predict how electrons would move between dynodes in the actual tube.[2]  The picture, (picture 1), below shows one of the models being used


3  PMTs were used as radar jammers in world war II.  When fully illuminated,they produce a very natural white noise that can't be distinguished from natural radio static.  The noise was amplified and broadcast to swamp enemy rad…

Lab Book 2014_05_22 Logistics and the Water Chiller

Lab Book 2014_05_22     Hamilton Carter               
Summary Worked a little bit on experiment planning today.  Most of the rest of the day was spent in meetings.  What time was left was spent preparing the water circulation system for the magnet power supply and the magnet.
Water Chiller Specifications Capacity:  8 gpm at 60 psi maximum pressure
Reservoir volume:  1.67 gallons

Drained the pipes heading into the sink area. Working on replacing the after filter once I track down a filter wrench.  


The cooling water will eventually wind up in the magnet power supply shown below.  All the large black tubes carry cooling water.


Magnet Requirements Cooling:  2 GPM at 40 PSI Temperature Rise:  20 C average
Magnet Power Supply Requirements Cooling: 0.5 GPM at 40 PSID nominal Output: 50 A at 40 V DC
The above specification are to be copied to a central specifications and status page to make them easier to find and track.
Experiment Background Data Magnetic fields affect the perfromance of photo…

Lab Book 2014_05_21 Cleaning and Planning

Lab Book 2014_05_21     Hamilton Carter Summary
Reviewed the theory that’s being tested by the experiment.  Looked into digitizing the data with an Arduino and did more cleaning and organizing.

QVT 3001
Looked into how hard it would be to build an Arduino interface to get the detector data out of our QVT 3001.  The QVT 3001 assembles the hits detected by the NaI photomultiplier tube combination into an energy spectrum.

There is an interface that allows external reading and writing of data. The reading interface is summarized in the following two figures.

Since the QVT requires a 16 bit bus, I’m going to need a bigger Arduino.

Hirsch Theory Articles Reading through Dr. Hirsch’s theory articles again.  They seem to layout the following path: 1.  High temp suerpcodnctors may be explained by the theory of hole superconductivity. 2.  Hole superconductivity fits with BCS but predicts kinetic rather than potential energy lowering for the condentation energy. 3.  Hole superconductivity predicts …

Lab Book 2014_05_20 Dewars and Outlets

Lab Book 2014_05_20     Hamilton Carter Summary
The fiberglass Dewar vacuum held.  The vacuum inlet was plugged to prevent any possible leaks there, and it was stored.  A 480 V three phase outlet for the magnet power supply was located.
4:30 AM Liquid Nitrogen Trap Refilling
Refilled the liquid nitrogen trap that prevents oil vapor from the diffusion pump from migrating opposite the intended vacuum flow into the Dewar’s vacuum jacket.  The liquid nitrogen condenses the oil vapor in the bottom of the small container, (the trap), that it cools.

The trap took two and a half cups of liquid nitrogen to refill.  The vacuum and leak detector readings before and after the fill are shown below. There was no noticeable improvement in the vacuum and leak readings before and after the Dewar refill.  This makes sense because the Dewar still had liquid nitrogen and was performing its intended function.
Vacuum and leak readings throughout the day Time Vacuum Leak 4:40 4:46 11:09 12:40 15:44