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Beta-Layering with Oscillating Temperature by Drew A. Geller, John D. Sheliak,

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DOE DP ... 'The results suggest that lower amplitudes and/or ... (aerogel, HIPE) 5/16/06. Relocation to. TA-16 / Bldg 202. commences. 5/15/06. Rapid heating ... – PowerPoint PPT presentation

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Title: Beta-Layering with Oscillating Temperature by Drew A. Geller, John D. Sheliak,


1
Beta-Layering with Oscillating Temperature by
Drew A. Geller, John D. Sheliak, James K. Hoffer
LA-UR-06-1928
  • presented at the
  • High Average Power Laser Workshop
  • sponsored by
  • The Department of Energy Defense Programs
  • hosted by the
  • Oak Ridge National Laboratory
  • Oak Ridge, Tennessee, March 21-22, 2006

2
Last time The results suggest that lower
amplitudes and/or lower temperatures may provide
better surface enhancements. Experiments at 17 K
are now underway
3
More recent work exploring the phase space.
  • Experiments spanning the range 16-18.5 K.
  • Varied the amplitude of the oscillations
  • For high amplitudes, the smoothing effect should
    be apparent at the expense of bubble formation in
    the solid.
  • For low enough amplitudes, there should be little
    smoothing but also less 3He bubble formation.
  • Varied the period of oscillations, 2.5-5
    minutes/cycle.
  • Limited by response of cryostat, thermal
    penetration depth of layer.
  • Tried different time dependences square, square
    with exponential decay, quasi-sinusoidal.
  • Applied oscillations during or after
    equilibration of a fresh layer.

4
Smoothing at 17 K
5
Time evolution of roughness spectrum
6
Compare time evolution with foam experiments
Temperature oscillations 4mm dia. sapphire
sphylinder substrate No foam Total layer
thickness 400 microns
No oscillations 2mm dia. toroidal Pt
substrate Foam Total layer thickness 70 microns
7
Time constants for smoothing
8
All data
9
Averaged data
10
Summary
  • We have completed parametric studies of
    temperature oscillations over 16-18.5 K.
  • Higher amplitudes produce more smoothing at the
    surface but also create more bubbles in the
    solid.
  • We have only looked at a small range of periods.
  • We have not seen sensitivity to the shape of
    envelope of applied oscillations.
  • Time constant for smoothing of 45 minutes much
    faster than smoothing over foam.
  • Oscillations may be applied shortly after
    freezing.

11
HAPL Milestones Timeline FY-06
2/7/06 breathing experiments completed
9/30/06 Begin elastic modulus strength experimen
ts
8/31/06 Beta-Layering in alternate
foam materials (aerogel, HIPE)
5/16/06 Relocation to TA-16 / Bldg 202 commences

8/1/06 DT strength apparatus complete
February March April May
June July August
September October November
3/1/06 Effectiveness of sapphire inserts
9/30/06 XPCI apparatus preliminary design
5/15/06 Rapid heating of a foam-lined DT layer
8/04/06 Tritium loop preliminary study completed
8/15/06 Relocation completed
Note Specific dates are subject to change.
12
We are ready to field this improved cell
  • Insertion of windows at the ends of the coil
    will provide a clearer view through the layer and
    will confine the material at the ends.


Thickness of windows must be carefully chosen to
leave only small gaps at ends of the cell.
13
Bubble Formation Near The Solid Edge Adds False
Surface Roughness Noise
18 K, 600 micron solid DT layer
14
The Power Spectrum Was Split, with Each Segment
Fitted with a Power Function
15
The Lower Segment is Shifted Down to Line Up
with the Upper Segment Pwr Fit
16
An Earlier Image for this Equilibration Shows
Much Less Bubble Formation
17
Reduction of This Bubble Induced Noise Results
in Spectra That Are Consistent with Low Noise
Images Having Fewer Bubbles
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