Roasting a Christmas Tree

Posted on October 30, 2014 by Gary Carruthers

Clink Street, London, 21st August 2014

Over time, quartz crystals change their frequency a little bit.  Not much, but enough for me to care about.  Contaminants introduced during manufacture fly off.  The resin that holds the quartz into place settles in.  An occasional shock such as dropping can suddenly bring about change, but in general it takes a year or so for a crystal to find its groove.

We need to accelerate the process so we have a crystal that has been properly run in before we try to characterize it.  To this end we have purchased a crystal aging system.  It ages them using the military standard process of one week at 105°C being equivalent to a year of normal aging. 

See photo.  Any resemblance to a conventional kitchen oven is entirely coincidental.  (Our aging system even has a timer and a little bell that goes 'ding' when it turns the heating off.  Sadly, it doesn't have a 7- or 14-week setting.  It would have been tremendously satisfying to hear it 'ding' after two weeks of quartz slow roast.)

We've just started running tests today.  The circuits need to be powered up so we can get data in and out of them during the test, using the Bluetooth connection.  Batteries, however, don't like 105°C , so we've had to create a string of circuit boards hanging from two power wires with an external power feed.  As an easy visual check to make sure the power connections are OK, we flash the LEDs.  They're in the oven now, flashing like a Christmas tree.

Great experimental physics, I know, but our office cleaner thinks I'm totally loopy.

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