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# Martin Holt <mvholt@uiuc.edu>
# requesting 5 days, at minimum=3 days
# beamline 33BM, "TDS analysis of low temperature phonon renormalization in superconducting Nb"
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# top:/home/www/beamtime-requests/req00251.txt
# UNICAT Member Beam Time Request  #251
# created Fri Mar 15 20:05:26 CST 2002
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beamline:
	33BM

collaboration:
	Yes

contact:
	mvholt@uiuc.edu

days:
	5

description:
	As part of the BCS picture of superconductivity in elemental Nb, below
	the transition temperature phonons of energy less than twice the gap
	energy are unable to break cooper pairs and so travel ballistically through
	the crystal.  As part of the spatial renormalization of these phonons,
	small kinks appear in the phonon dispersion curves following the onset 
	of superconductivity.  This should manifest itself in the TDS intensity 
	near the gamma point changing as a function of applied magnetic field at
	a constant temperature (T<9.2K).  
	The proposed experiment is to collect TDS intensity from
	superconducting Nb over a wide angular range both in no magnetic 
	field (H=0) and H>Hc.  Suitable analysis of the subtraction images
	should verify key aspects of BCS superconductivity in Nb.

equipment+required:
	He displex, roper CCD, diffractometer

experiment:
	TDS analysis of low temperature phonon renormalization in superconducting Nb

foreign+nationals:
	

hazards:
	closed cycle He displex

minimumdays:
	3

name:
	Martin Holt

nonmembers:
	

unacceptable+dates:
	August 4-10 May 4-6


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