Coining Precision Sine Wave Pattern on Lead for High Energy Density TargetJack Nguyen, Pascale Di Nicola, Cynthia Dawn Walker Panas, Sergei O Kucheyev, Chockalingam Kumar
Lawrence Livermore National Laboratory, Livermore, CA 94550
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.
Coining Tool Technology
• Coining tool consists of two main components: The upper planar die and the lower die with a sine wave
pattern. Both dies are made of steel and coated with nitride.
Die Fabrication Process
Lower die
Lead and vanadium foils
Material Preparation & Measurement
• For Rayleigh-Taylor targets, the physics package includes bonded vanadium and lead (or lead antimony)
sandwiches with interfaces thinner than ~100 nm.
• The bonded sandwich needs be mechanically robustness for subsequent coining and machining.
• We use roll-bonding to make such V/Pb and V/PbSb sandwiches.
• Cold rolling was also used to reduce Pb and PbSb films to required thickness.
Lead and Lead Antimony
Coining Ripples on Sample Materials
• Coining is an efficient way to fabricate sine wave features on lead and lead
antimony samples.
• Pattern transfer requires optimization of the force-time profile.
• Only the central section on the dual sine wave pattern is cut out and used
in the target package.
Coined Lead & Lead Antimony Samples
Machined
ripples on die
The absolute height between the lowest and highest
points on die surface should be < 250 nm
White light interferometry image
from the center area
Planar surface die
Fast Fourier Transform Analysis shows fully formed ripples with
secondary axis < 5%
White light interferometry scanning
• Hard nitride steel causes a diamond turning tool to wear out quickly.
• Nitride is brittle and can be chipped easily during machining.
• Using brass instead of nitride steel significantly reduces the failure rate and machining time. However, brass
dies are softer and, hence, require careful handling.
The upper die is
machined to match
coining materials
Bonded
vanadium lead
sample after laser
cutting
Lead and vanadium foil
Power rolling mill
• Lead or lead antimony foil is first rolled to required thickness.
• Both vanadium and lead / lead antimony are chemically cleaned.
• Stacked lead and vanadium samples are sandwiched between a stainless steel envelop before feeding into
the power rolling mill.
• Bonded sandwiches are laser cut to ~8 mm diameter discs for coining.
• Thicknesses are precisely measured by a double sided interferometer.
45 um lead foil
40 um Vanadium foil
Stainless steel envelope
Load cell
Die with the sine
wave pattern
Spherical radius
(planar) die
Foil to be coined
Spherical radius die
Dual sine waves die
Imprint ripples on sample
Remove coined product
Bonded
vanadium and
lead sample
Precision sine
wave pattern on
coined sample
Fast Fourier Transform Analysis of coining die and Pb sample
Dual sine wave pattern is fully formed
and in specification.
Roll-bonding and coining processes have been developed to manufacture Pb and PbSb components for
high-energy density physics targets. There is an ongoing process development to improve the yield and to
reduce the process time.
The Target Fabrication team at LLNL has developed processes of roll-bonding and coining of dual sine wave ripples on tantalum, lead, and lead antimony foils for Rayleigh-Taylor targets. We discuss challenges encountered in bonding and coining of Pb alloys, including coining tool fabrication and optimization of roll-bonding and pattern transfer procedures.
Roll bonded product
Lead and vanadium foils
Scanning electron microscope shows
successful bonding between vanadium and
lead
Scanning electron microscope shows
successful bonding between vanadium and
lead antimony
Vanadium
Lead Lead antimony
Bonded vanadium and lead / lead antimony are coined at room temperature.
White light interferometry measures
ripple pattern in the region of interest
