preliminary results from titan divergence measurements l. d. van woerkom department of physics the...
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Preliminary Results from TitanDivergence Measurements
• L. D. Van Woerkom• Department of Physics• The Ohio State University
FSC Special MeetingLLNL4-6 August 2010
Collaborators
Funding
• Office of Fusion Energy Science (OFES) – Advanced Concept Exploration Program
• Fusion Science Center (FSC)
• This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
FSC
Outline
• Defining electron beam divergence• Titan Experiments– August 2009– May 2010– July 2010
• Conclusions
Rear view buried layer Ka imaging
CCD
LaserKa fluor
Bragg
crystal Ka (10 mm res.)
2000 4000 60000831_01_xray
Cone angle 40o
Min diameter 75 mm
• Initial e- beam size ~75 mm>>~10 mm
laser spot (in agreement with transverse view
penetration)
• Beam spreads with 40° full angle
30-100J/5 ps
mic
ron
s
microns
R. Stephens et al, PRE 69 066414 (2004)
0
50
100
150
200
250
300
0 100 200 300 400 500 600
Kα crystal(south)
Ka detector
Titan experiment layout
B01 series,15 Al/25 Cu/25 Al/25 Al/1mm CH
From top right to bottom left: B02-1, no background subtraction; B02-2, couldn’t tell where signal started and background end; B02-3, no background subtraction; B02-4, no
background subtraction
Buried Cones -- New
15° half angle C
Cu
Al
As deep as we can image. 200 um?
Targets:• Electrical Discharge Machine )EDM(• start w/ solid uniform Al foil, EDM cone holes, glue C get lost
2009 targets varied depths2010 targets const. depths
• Surrounding Al eliminates interface fields
• Carbon provides get lost layer
First Results Aug 2009
Kα spot size and Kα yield for buried cones
May 2010, Mingsheng Wei
July 2010 Titan results
Summary of KB Microscope Results July 2010
H Friesen. July 28, 2010
Everything
Aug 2009
Stephens 2004
May 2010 – 30 mm tip
May 2010 – 60 mm tip
=62 Q )full(
Jul 2010 – KB
Source Size
• Use Cu K-alpha imager looking at front• Measure spot size for a variety of conditions• From Jan 2008
Our main target was Al/Cu/Al
10 µm Al
25 µm Cu
1000 µm Al
Irradiated side
Titan Kα spot diameter as a function of Pulselength
104 J
18 J
98 J
Titan Kα spot diameter as a function of Laser energy
@ 0.7 ps
Titan Kα spot diameter as a function of Pre-pulse
Titan Kα spot diameter as a function of daily shot #
Conclusions
• Alignment very difficult • Lots of scatter due to misalignment• Good alignment shows no real difference from flats• Full angle ~ 60-80 degrees
• Good News?– Effects of cone structure not dominant– Can use flats for source studies