#
# top.uni.aps.anl.gov:/home/www/beamtime-requests/req00219.txt
# UNICAT Member Beam Time Request  #219

# created Tue Nov 27 16:44:57 CST 2001
#
beamline:
	33ID

collaboration:
	No

collaborator+Hawoong:
	on

contact:
	ikr@uiuc.edu

days:
	6

description:
	This application predates our first attempt at crrying out this experiment which is scheduled to start Dec 1.
	We therefore have no results to report, but there will be news by the time of scheduling.
	By March, 34_ID should be able to do the coherent diffraction part of this expt, but not the UHV part.  We would therefore like to anticipate a second run on 33-ID-D.
	The experiment is to look at the shapes of Pb crystals after dewetting from their substrate.  Pb will be evaporated onto a cold SiO_2 substrate (wafer) to a thickness of a few hundred AA.  Upon annealing this will crystallize into approximately spherical crystals around 0.5 microns in diameter.
	One crystal from the random distribution of orientations will be selected by scanning roller-blade slits in front of the sample.  The 111 diffraction peak will be imaged with a CCD detector on an extension of the 33-ID-D diffractometer arm.
	Upon heating, surface melting (SM) is supposed to take place, starting a few degrees below the melting point of 327degC.
	When layers melt they will disappear from the crystal diffraction which will therefore appear to come from a smaller crystal.
	The size of the crystal can therefore be tracked wrt temperature and compared with SM predictions.

equipment+required:
	UHV diffractometer
	Pb evaporator

experiment:
	Surface melting of Lead nanocrystals

foreign+nationals:
	

hazards:
	Long (2m) detector arm will need counterbalancing with lead bricks.  We have the training.
	The arm may hit the roof unless prevented with limit switches.

minimumdays:
	4

name:
	Ian Robinson

nonmembers:
	

unacceptable+dates:
	March 18-22 (March meeting)
	March 2-10 (?)
	April 25-28


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