Leak Detector Testing... Again Lab Book 2014_07

Leak Detector Testing... Again Lab Book 2014_07_27

Summary:
The leak detector stopped working correctly several weeks ago. It didn't exactly depart his mortal coil so much as just stop being useful. Sort of like a major league baseball catcher hunkered in a hockey goal. It looks sort of like it has the right equipment, but it obviously incapable of performing it's tasks in any sort of meaningful way. It boils down to this, the mechanical roughing pump is still pulling a vacuum that should enable the diffusion pump, responsible for doing the detailed vacuum work, to switch on, and yet the diffusion pump abjectly refuses.

If you're new to the experiment, the background of what's going on here in broad strokes can be found at the bottom of the post.

Lab Book 2014_07_25 Hamilton Carter

Leak Detector Work

Leak detector testing was resumed. The first test was to check the vacuum on the end of the vacuum hose coming from the roughing pump and normally attached to the diffusion pump, but now attached to a thermocouple gauge. The vacuum pulled down to 150 mTorr after several minutes.

The second test was to move the roughing pump path selector from the right hand path to the diffusion pat as shown in the figure above to the left hand path into the space evacuated for leak detection. To do this, the smaller knob is turned clockwise until the white dot on its face points along the left hand path Their was no vessel to be leak detected attahced on the left hand path. The path was merely attached to the thermocouple gauge. The vacuum pulled down to 30 mTorr in less than a minute. After two more minutes, the pressure was down to 27 mTorr. Checking the right hand path again after this, it was found that the vacuum pulled down to 50 mTorr. The hose connection to the thermocouple gauge may have been leaky.

Next, the hose form the roughing pump was reattached to the diffusion pump The pump was run for a minute or so on the right hand path attachd to the diffusion pump. There is no guage attached to that side to read the vacuum, so after the first minute, the path knob was changed to the left hand path. The thermococuple guage indicated a vacuum of < 10 mTorr immediately. After another minute, the vacuum was down to 4 mTorr. During this test, the built-in meter shown above read a pressure of .4 mBar.

The large valve knob that opens the diffusion pump to the left hand path was opened. No change in the vacuum was observed. In a later run, a brief change in vacuum to a pressure of 11 mTorr was observed but after 1.5 seconds, the pressure reduced again to its original value.

To make sure the valves were working correctly, the trap was opened as a coarse check of its vacuum pressure. There was an inrush of air consistent with the vessel holding a vacuum before being opened.

The indicator light for < 10^-2 on the panel of the leak detector was never lit. It’s beginning to appear that either the pressure gauge built into the leak detector is broken, or there is damage to the control circuits that light the indicator on the front panel. I don’t believe the bulb is out because the diffusion pump never heated up, even after being plugged back into power.

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. My experiment will look for H-rays emitted by both a Pb and a YBCO superconductor when it is quenched by a strong magnetic field.

This series of articles chronicles both the experimental lab work and the theory work that’s going into completing the experiment.

The lab book entries in this series detail the preparation and execution of this experiment… mostly. I also have a few theory projects involving special relativity and quantum field theory. Occasionally, they appear in these pages.

Call for Input

If you have any ideas, questions, or comments, they're very welcome!

References

1. Hirsch, J. E., “Pair production and ionizing radiation from superconductors”, http://arxiv.org/abs/cond-mat/0508529

The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1. While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero. This is typically explained in the following way. While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare. That doesn't stop us from looking for them though! Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2]. Cabrera was utilizing a loop type of magnetic monopole detector. Its operation is in...

Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

Now available as a Kindle ebook for 99 cents ! Get a spiffy ebook, and fund more physics The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems , there seem to be fewer explanations of the procedure for deriving the conversion, so here goes! What do we actually want? To convert the Cartesian nabla to the nabla for another coordinate system, say… cylindrical coordinates. What we’ll need: 1. The Cartesian Nabla: 2. A set of equations relating the Cartesian coordinates to cylindrical coordinates: 3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system: How to do it: Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables. The chain ...

More Cowbell! Record Production using Google Forms and Charts

First, the what : This article shows how to embed a new Google Form into any web page. To demonstrate ths, a chart and form that allow blog readers to control the recording levels of each instrument in Blue Oyster Cult's "(Don't Fear) The Reaper" is used. HTML code from the Google version of the form included on this page is shown and the parts that need to be modified are highlighted. Next, the why : Google recently released an e-mail form feature that allows users of Google Documents to create an e-mail a form that automatically places each user's input into an associated spreadsheet. As it turns out, with a little bit of work, the forms that are created by Google Docs can be embedded into any web page. Now, The Goods: Click on the instrument you want turned up, click the submit button and then refresh the page. Through the magic of Google Forms as soon as you click on submit and refresh this web page, the data chart will update immediately. Turn up the:...

Copasetic Flow

Search This Blog