Envelope Extraction in Origin

I'm doing "envelope extraction" analysis on my dHvA data. It took me some time to figure out which boxes to check or uncheck on the Origin FFT tool, so I thought I would just document that here, partially so that I remember how to do it myself.

While usually I would apply a window (e.g. "Hamming window") while doing FFT, here it's better to not use a window i.e. use the "Rectangular" window.

Forward FFT
Use "Rectangular Window"
Uncheck "Normalize Amplitude"
Check "Shift Results"

Apply filter

Backward FFT
Select real and imaginary columns
Use "Rectangular Window"
Uncheck "Normalize Amplitude"
Uncheck "Shift Results"

Plot 2*r
Results may be offset in x-direction.

Converting PDF images to EPS

I've had to convert PDF images to EPS quite often over the past few days, and I've developed a foolproof if intricate process to do this conversion. It is especially good for if you only want to convert a small section of a document (i.e. a figure), because if you want to convert the entire document, Ghostview/Ghostscript can do it for you in one step.

Here is my process:
1. Open document in Adobe Reader. Use the Snapshot Tool to select desired area.
2. Open Paint. Paste from clipboard. Save as jpg.
3. Use jpeg2ps to convert to EPS.
4. If necessary, use Ghostview/Ghostscript to resize bounding box. (Select "PS to EPS" under File menu)

If your jpg image is too large, part of it might get cut off in the jpeg2ps conversion. If this happens, resize your jpg image so that it's smaller.

If you know of an easier way to do this, I'd be interested to hear about it. Also please share other document/latex tips you might have.

Organizing PDFs

I'm trying out Zotero as a tool for organizing pdfs of journal articles. My journal articles are always hidden away in multiple folders on my computer and it's hard to find them when I need them. Zotero lets me access them from a central location, and I can tag and search them. If you are viewing certain websites, like Socrates or Physical Review, Zotero will import title/author information for you. It will also export Bibtex.

If you are using a Mac (I don't think any of us are), Papers is the new, awesome scientific paper organizer for Macs. I was searching for a PC version, and that's how I came across Zotero.

PPMS cryopump regeneration

We have been having a lot of trouble with the PPMS cryopump. The manual claims we should only need to regenerate the pump once every 500 uses, but we are needing to regenerate every ~30 uses. Ernest at QD says that, every time we regenerate in dewar, we should run the regeneration command 5 or 6 times, and every time we regenerate out of dewar, we should run it 4 times, then do an in dewar regneration after finishing the out of dewar regeneration. I've modified the regeneration sequences accordingly, and we should all remember to do an in dewar regeneration after finishing an out of dewar regeneration.

Digitizer

This is something I learned from Suchitra: You can use a digitizer such as Engauge Digitizer to read data points off of published graphs.

Corporate Express orders

During our last office supply order, I discovered a few things I thought I'd share

• We have a new catalog on the 4th floor. The old catalog has outdated page numbers.
• We are only allowed to order the following recycled printer paper: EXP8511RCY
• You should not use the old online form, but download a new version of the form from http://www-ssrl.slac.stanford.edu/staffresources/corpexform_nt.pdf, fill it out, and email it to Stephanie Carlson.
  

Heat resistant gloves

Covex gloves, that's what they are... Check out the amazing gloved-hand amidst leaping flames animation on the website http://www.polygenex.com/ :) The orange gloves used for the glass torch, that is - I couldn't find what kind they were all this while, and just managed to locate them.

The crystal growing tradition

Met Zach Fisk at a workshop - interesting, considering we've all descended from him. A couple of his off-the-cuff remarks were that fluxes he uses are sometimes binary: eg. to grow YbxCuyInz, he might use a Cu:In flux rather than just In as I would have guessed. Also, at one point I had considered using BeO crucibles instead of Al2O3 - I didn't actually end up doing this, but if one ever does, apparently BeO sucks up large quantities of water very quickly, and needs to be dried out before use each time. But apparently Zach Fisk's greatest asset is that he is very good at telling dinner party stories :)

Suchitra's famous!

Check out the NHMFL website: http://www.magnet.fsu.edu/
Or, in case they've removed it from the front page: http://www.magnet.fsu.edu/mediacenter/factsheets/mainattraction/index.aspx

Downstairs centrifuge rotor II

Here is an illustration to better explain what's going on with the centrifuge rotor capsule.

I took the capsules back to the machine shop today. The problem was that while the machine shop drawings show a slanted inside edge, there is no 'call-out' with numbers so it's easy to miss the slant. The machine shop will fix them for us; they will put in a 30 deg inside slant. I can pick them up Tuesday afternoon.

Chatted a bit with Carlheinz. His office is being remodeled and they are having walls put in to keep out the dust and noise. They've thrown out cabinets, papers, and books that have been there for as long as 40 years, making way for computers and the electronic age.

Diagnosing glovebox pump

Today Alan helped me use a pressure gauge to diagnose the glovebox pump. We concluded that our pump is very bad. Our pump only pumps down to 80 Torr whereas the KGB pump goes down to 20-30 mTorr. We didn't find any major leaks in the glovebox system itself.

Test details:
Our pump connected to gauge, with outlet filter: 100 Torr
Our pump connected to gauge w/o outlet filter: 80 Torr
--> we might need new outlet filter
KGB pump connected to gauge: 20-30 mTorr
KGB pump connected to gauge + glovebox: 20-30 mTorr
KGB pump connected to gauge + glovebox + mini-antechamber: 20-30 mTorr

Opening valve slowly (pressure not exceeding 100 Torr), it took about 4 minutes to pump down the mini-antechamber.

Tomorrow I will set up the KGP pump semi-permanently so that we can use it while we have our pump repaired.

Outstanding physics major

George Margulis has been awarded the David S. Levine award for outstanding junior physics major. According to the physics department website, this award recognizes "academic breadth and demonstrated abilities in experimental physics."

Congratulations George!

2007 Applied Physics Commencement

Hi.

Nancy and I enjoyed the commencement.

Here is the picture of us.

Downstairs centrifuge rotor

I'd been having some trouble spinning my growths using the new centrifuge downstairs. Somehow, when depositing my growth into the centrifuge capsule, it would often get stuck on the lip of the capsule and I would waste valuable seconds poking it to make it go in. This happened several times before I realized that the capsules had not been machined exactly to specifications. While the upstairs, original centrifuge capsules have slanted lips, the ones on the new capsules are completely horizontal - thus providing a ledge on which my growths can get stuck.

Since I realized this, I've been bringing one of the old capsules downstairs to do my spin. Eventually I'll go to the machine shop to see if the new capsules can be fixed.

SLAC website problems

I almost always have trouble accessing the SLAC internal websites that require passwords. I don't have much trouble with purchasing, but I can't figure out how to log on to any site that starts www-internal.slac.stanford.edu (useful for some travel docs). I think Corrina said that, since they re-vamped the computer system a few months ago, users from Stanford campus need to connect to these sites through a special webpage. Does anyone know anything about this?

Pump time for glasswork 2

I almost always pump for at least 5 minutes between flushes when I'm doing glasswork.

Crucibles

This is a really basic qn. for Oxide crystal growers... How do we decide when to use Al crucibles sealed in Quartz or Pt crucibles? Si obviously attacks quartz - but how about the the other oxides we've grown, why do we use Pt?

Automating Windows tasks

K.Yun recommends this utility for automating repetitive tasks in Windows:
http://www.autohotkey.com/
He uses it to import his SSRL data into Origin.

Angstrom symbol in Origin

Here's how to make the angstrom symbol in Origin: \(197)

Pump time for glasswork

When doing glasswork, how long do you wait for each pump of the pump/flush cycle? I used to wait almost no time at all, but now I'm thinking I should wait at least 5 minutes. This is because when using the mini-antechamber of the glovebox in 291, a 5 minute wait is necessary for each cycle or else oxygen will be let in.

Furnace E calibration

Last week I put identical ErTe3 growths in Furnace C and Furnace E, two in each furnace; both were spun at 515 C. The growths in Furnace C spun clean, whereas half of the contents of each Furnace E growth was encased in a tellurium lump.

RTe3 growers: Have you observed this tellurium lump phenomenon and have you thought about how to avoid it? My thought is that this occurs when the spin temperature is too low, and too close to the tellurium melting point.

My hypothesis is that Furnace E is calibrated so that 515 C is lower than it is in Furnace C. For this week's ErTe3 growths, I will spin Furnace E at 520 C and Furnace C at 515 C.

Any comments?