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Bendable Crystals – Blessings in Disguise

by Kathy Chambers on Tue, November 03, 2015

Sometimes difficulties turn out to be blessings in disguise – especially in research.  An excellent example is the story of how crystals that were too bent for their intended purpose inspired the use of deliberately bent crystals to resolve properties of X-ray pulses. 

Image credit: Matt Beardsley, SLAC National Accelerator LaboratoryImage credit: Matt Beardsley, SLAC National Accelerator Laboratory

Researchers at the Stanford Linear Accelerator Center (SLAC) reported that custom ultra-thin silicon crystals were ordered for an instrument in an effort to split X-ray pulses from SLAC’s Linac Coherent Light Source (LCLS).  Researchers needed near perfect crystals to obtain precise measurements on a pulse-by-pulse basis to correctly obtain the best results.  It was discovered that one batch of silicon crystal samples they received unfortunately had wrinkles, apparently bent during their processing.  Measuring the curvature led these researchers to an important breakthrough. When they sent LCLS pulses through a bent crystal, they were able to divert a small part of the light and break it into its component wavelengths for color analysis while the bulk of the light went downstream for experiments.

After much testing, the research team designed new versions of thin crystals and designed a delicate fixture to bend them.  The crystals were incorporated into a high-resolution spectrometer system for monitoring the X-ray laser’s characteristics for every pulse.  The spectrometer then played a critical role in a newly developed technique called “self-seeding” which became a permanent option for accelerator scientists.  This technique produced more refined, higher intensity pulses that could probe deep into complex materials and help answer questions about exotic substances.  This work was the focus of a SLAC 2012 feature story and is described in the Applied Physics Letters paper, “A single-shot transmissive spectrometer for hard x-ray free electron lasers.”

Bent crystals are being used today as crucial working components by DOE researchers and their international collaborators to analyze x-rays to determine the conditions of the x-rays’ emitters, and to manipulate beams of subatomic particles.  Read more about research being done with bent crystals in DOE’s SciTech Connect.  OSTI’s Dr. William Watson also provides a layman’s look at bent crystals used in DOE research in his latest white paper “In the OSTI Collections: Bent Crystals.”  Additionally, the October 2015 DOE Science Showcase highlights bent crystals.

Page last updated on 2017-03-16 08:26

About the Author

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Kathy Chambers
Technical Writer, Information International Associates, Inc.