preliminary results from titan divergence measurements l. d. van woerkom department of physics the...

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