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Saturday, 25 October 2014

Boulevard of Broken PEEMs

Where the City Sleeps and I'm the Only One, I Work Alone

To find out what our tiny space magnets are actually doing, we have to use high intensity beams of X-rays produced by a synchrotron (a type of particle accelerator) to create nanoscale magnetic and compositional maps of  our meteorite samples. The instrument we use is called a PEEM (photoemission electron microscope).  To make a compositional map of our sample we vary the energy of the X-rays; there's a specific energy at which electrons in iron metal get excited, and a different energy at which electrons in nickel metal get excited.  By exciting these electrons, we produce an image, which glows strongly in the places where each type of metal is.  To make a magnetic map of our sample we rotate the x-rays, depending on whether the x-rays are rotating clockwise or anticlockwise, different magnetisation directions get excited and glow brightly (this is a technique called x-ray magnetic circular dichroism, or XMCD).

A compositional map of our of our meteorite samples.  The green lines
are an overlay of the associated magnetic map.

Some magnetic maps from one of our samples.

I'm currently at an experiment working with Rich, James, Julia and Florian at BESSY II in Berlin.  We've got a week of 'Beam Time' as it's known in the trade to collect as much data as we possibly can in each daily twelve hour shift. Working beam times is pretty intense (and that's just the x-rays...) and there are both good and bad aspects.

Helmholtz Zentrum, Berlin

The good:

  • All you have to do is sit in the lab and take a selfie to make it look like you're doing REALLY SERIOUS SCIENCE
  • The techniques are absolutely incredible, and we have the most wonderful beamline scientist to work with whilst we're here
  • So far, the results have been really exciting
  • We get to use a cool technique no one else is using to look at meteorites
  • I get to pretend I'm a physicist

The bad:

  • The shifts are long, and every other week (like this week) you have to work from 7PM until 7AM.  Daylight is not a thing.
  • When everything goes wrong, whether it be user error or chance, it's never good
  • Being left in charge of the PEEM - I don't even want to think how much this set up costs to run, but the prospect of being responsible for it is terrifying

The ugly:

  • The microwave meal vending machine
  • Spending several consecutive nights with the same people in a small confined space, especially when it hits 4:30AM.

A day in the life

This has been a pretty typical day this week

14:00 - Wake up, open the curtains to catch a rare glimpse of sunlight 
14:30 - Go for a run to try and burn off the eight chocolate bars I ate during the shift last night
15:30 - Shower
15:45 - Walk to the synchrotron
16:00 - Chat about what we're going to do in the shift tonight, get the right samples loaded and into                 position and focussed
16:55 - Mad rush to get a coffee before everywhere shuts for the night
17:30 - Play sporcle quizzes and sit at the PEEM in case we get the X-rays early
18:30 - Get everything ready and set up in preparation for getting the X-rays

19:00 - We have the X-rays!  Do any final alignments and focussing and then get measuring
20:00 - Measuring
21:00 - Measuring
22:00 - Measuring
23:00 - Quick break for dinner (breakfast? lunch? who knows..)
00:00 - Curse that we were collecting data over midnight, screwing up where everything gets saved
00:30 - Coffee/Chocolate run
01:00 - Watch a collection of hilarious and weird Youtube videos
01:15 - More chocolate
02:00 - Everyone's flagging a bit - sleeping on chairs in the lab becomes acceptable
02:30 - Coffee and Chocolate - compulsory whole team break before we go completely insane
03:00 - Youtube or Sporcle or sleep
03:30 - Still so long left
04:00 - Everyone's had enough, lots of measuring in silence
05:00 - Measuring

06:00 - Start finishing everything up for the night
06:15 - Walk back to guest house in dark and cold, complaining about how dark and cold it is
06:30 - Finally into bed

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