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# arev:/usr/local/unicat/unireq/beamreq/req00160.txt
# UNICAT Member Beam Time Request  #160

# created Mon Mar 05 16:33:58 CST 2001
#

collaboration:
	Yes

contact:
	ikr@uiuc.edu

days:
	6

description:
	We plan to continue our investigation of Coherent X-ray Diffraction
	of Au nanocrystals.  Our results to date, based on three runs at
	33-ID, are i) the successful measurement of three dimensional
	diffraction patterns ii) the successful inversion of these data in
	2D to produce images of the shapes of the nanocrystals.  We already
	submitted a paper on this latter exciting result.  Eventually these
	experiments will migrate to sector 34 once the monochromator is
	completed, but we anticipate one more run at 33-ID, which may be
	the last.  The immediate goals of this experiment will be:
	
	i) Attempt to measure CXD from Au nanocrystals in situ at high
	temperature.  The shape of crystals determined by CXD at high
	temperature probably approximates the equilibrium crystal shape,
	which can therefore be determined.  The ECS is predicted to evolve
	dramatically with temperature, following the relative energy
	changes of the various facets; when a facet roughens, it should
	disappear altogether from the ECS.  We have developed an oven for
	the in-situ heating and are continuing to test it.
	
	ii) Attempt to study the effects of changing the longitudinal
	coherence length on the contrast seen in CXD.  Our simulations
	indicate that imperfect coherence, which affects the contrast of
	the fringes seen, results in "hotspot" artifacts in the
	reconstructed images.  This needs to be investigated
	systematically.

equipment+required:
	Huber diffractometer
	Channel cut (or equivalent) beam "conditioner" to narrow bandwidth

experiment:
	Coherence effects on CXD from nanocrystals

foreign+nationals:
	

hazards:
	15 volts will be used to power the sample heater.  The wires
	have been protected by cages.

name:
	Ian Robinson

new+request:
	on

nonmembers:
	

station:
	33ID-D

unacceptable+dates:
	April 17-19 
	April 26 to May 2
	May 17-19
	June 27 to July 4
	plus a couple of other days I did not write down: please check!



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