Sub-Micron Glue Bond

National Ignition Facility • Lawrence Livermore National Laboratory • Operated by the US Department of Energy

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Glue layer thicknesses have a large effect on laser based Material Science Experiments

In experiments on the National Ignition Facility researchers use temporally-shaped laser pulses to

recreate pressures within planetary cores. Under these conditions material properties are measured

(density, sound speed, crystal structure). Different sample layers are bonded together with glue. The

glue thickness directly impacts the uncertainty within the measurement.

Technique for minimizing glue layer Metrology – Glue thickness determination to 0.1 mm

Carol Davis, Jon Eggert, Dayne Fratanduono, Raymond Smith, Lawrence Livermore National Laboratory

Photos from a NIF target

Fe step targetCu ablator

1 mm VISAR

field-of-view

VISAR cone Hohlraum

~4 mm glue layer modifies the

structure of the measured shock

wave

Structure is absent for glue

layers < 1 mm in thickness

VISAR

Data

MICRON GLUE BOND METHOD• Place part Cu onto the center of Gel Pak, using vacuum chuck (see

part a)

• Apply epoxy with cat whisker, or small hair part (see part a)

• Spread epoxy with clean room foam swab (see part b)

• Place part Fe on top of the epoxy (see part c)

• Align and press with clean room foam swab

• Place Teflon film over the top of the parts

• Place Gel Pak on top of the 1st glass slide (see below)

• Place 2nd glass slide on top of the Gel Pak (see below)

• Set weight 500g-1kg on top of the glass slide in the center

• Leave on until epoxy has cured

• Completed planar Ablator assembly (see part d)

GENERAL INFORMATION

• Measurements can be taken with an HEIDENHAIN

with accuracy to 0.5+-um

• Measurement for the NIF Ablators is taken using the

Double Sided Interferometer accuracy to 0.1um

• Targets for LCLS, MEC, JLF, OMGEA, and NIF have been assembled

using this method

• Technique can be used to make 20 Planar Ablator type targets

at a time

• Thousands' of Planar Ablator targets have been assembled

using this process

• The thickness of the material ranges from 3um to 1mm

• The parts dimensions’ averages 2x2mm -3x3mm

• Many types of materials are used Qtz, Diamond, MgO Forsterite,

LiF, Al foil, Au foil, Cu foil, Fe foil, Pt foil and Pb foil, just to

name a few

Fe step

~80-120 µm thick

1st Glass Slide

2nd Glass slide

Epoxy bead

~40 µm thick Cu

~25 µm thick Teflon

Applied Weight

Gel Pack

(a)

(b)

(c)

(d)

Fe

CuGlue Bond

Cu

Fe

Epoxy

We use double-sided white light interferometer to measure each layer thickness of the target

individually and after the glue layer has been applied. This enables the final glue layer thickness to

be measured to sub-micron accuracies.

Fe layer 1

Cu layer 2

Sub-micron

glue bond

Lower white light

interferometer

Upper white light

interferometer

Example of double sided Interferometer Data

Photograph of target

Measured Thickness =

Upper Interferometer –

Lower Interferometer

Fe step thicknesses are

determined from a

histogram analysis

Fe Layer 1 is 80-120 mm

thick

Cu Layer 2 is 40 mm thick

Schematic of NIF target design

40 mm Cu

Ufs(t)

83.13/96.54/

106.28/115.73 mm Fe

Au

Ho

hlra

um

11

mm

6 mm

In our shots on NiF exploring the properties

of planetary interiors 80-120 mm thick Fe

step targets are glued onto a 40 mm Cu foil

0.2

mm