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The Beams and Hydrodynamics team is dedicated to conceiving, designing,
and fielding state of the art physics experiments oriented towards increasing
our understanding of weapons physics. Our team is composed of four highly skilled technicians, five
professional staff, and two contractors who collaborate with organizations throughout the Laboratory
on a variety of experiments such as: advanced radiography experiments at the
Integrated Test Stand, laser based experiments, and hydrodynamic experiments at Trident, x-ray imaging at
Pegasus, advanced imaging detector development, anomalous energy
loss and advanced accelerator experiments at the High Brightness Sub-picosecond
Accelerator, and other basic physics experiments.
 Team Leader: David
M. Oró
Nevada Test Site
P-22 is deeply involved in protecting and archiving the volatile
test data it took during more than three decades of underground
nuclear testing at the Nevada Test Site (NTS). Our goal is to bring
the groupÕs data to a stable and readily accessible state. These data
will be used to benchmark all future calculational tools. The
archiving activities constitute a significant effort in P-22 and
involve individuals responsible for the original execution of
underground nuclear tests as well as trainees. Many of the
numerical algorithms developed for analyzing the information
from underground tests have been ported to modern computer
platforms as part of our effort to preserve this valuable and unique
data.
In addition, P-22 continues to participate in experiments
performed underground at NTS, both to maintain our readiness to
support a resumption of nuclear testing should the need arise, and
to study the physics of weapons performance and materials (Fig. 3).
These experiments increase our understanding of weapons science
by allowing improvements in code calculations and in estimates of
the severity of problems and changes occurring in the nuclear
stockpile as it ages.
At present, we are supporting the Los Alamos Dynamic
Experimentation (DX) Division on experiments to measure the
properties of material ejected from shocked plutonium. These
experimental efforts are discussed in detail in a research highlight
in Chapter 2. By performing these experiments underground at
NTS, the plutonium is handled and contained in a manner similar
to that used for underground nuclear tests, maintaining the
readiness training necessary to support the potential for future
nuclear tests.
Additional information on this project is available by clicking HERE (PDF-390Kb).
P-22 Contacts: David M. Oró,
Lynn Veeser , David Clark and
David Holtkamp
High-Energy-Density Physics at Pegasus
The Pegasus Pulsed-Power Facility which fired its last shot in 1999, provided a unique capability for delivering strong, converging, shock-driven or adiabatically driven compressions with excellent diagnostics. Pegasus allowed physicists to gather important data on material behavior at high-energy-densities, which are necessary for weapons physics and basic science.
Our studies of the hydrodynamic flow of materials under extreme conditions are crucial to developing and testing weapons models. Our experiments focussed on instabilities at the interface between two materials of different densities.
Our studies of the properties of materials under extreme conditions included topics such as material failure through spall and ejecta, plastic deformations, strain and strain-rate effects, and interfacial friction. One significant series, carried out in collaboration with Livermore, focussed on spallation of shocked aluminum targets and the growth of instabilities.
We explored the electronic properties of materials in the presence of strong magnetic fields, and we collaborated with Russian scientists to study liner stability. In preparation for the future Atlas facility, we also conducted experiments on mechanical joints that can carry high current-densities.
Additional information on this project is available by clicking HERE.
Contact: David M. Oró
Instabilities in Taylor-Sedov Blast Waves
The stability of Taylor-Sedov blast waves in low-density gases was investigated. Theoretical
results have shown that the stability of propagation in uniform gases depends on the adiabatic
index of the gas. This was verified with a LASNEX simulation. Both stable and unstable propagation
was observed in experiments at the Trident laser facility. The experimental verification
of the adiabatic index criterion for stability is not yet completed.
Additional information on this project is available by clicking HERE (PDF-390Kb).
P-22 Contacts: David M. Oró
Other Contacts: Robert D. Fulton
, G. T. Schappert and Randy Johnson
Bremsstrahlung Target Plasma Expansion Experiments
A critical issue for high resolution radiography is the integrity of
the bremsstrahlung converter during the electron beam pulse and, for
multiple pulse radiography, the spatial extent of the plasma plume for
subsequent pulses. Energy loss calculations indicate that the bremsstrahlung
converter on DARHT will be heated to ten's of eV by the electron beam.
Expansion velocities of several cm/microsecond are possible which may lead
to various instabilities in the propagation of the electron beam thereby
resulting in degradation of the spot size. For multiple pulse radiography,
in order to avoid transiting the plasma plume, subsequent pulses will have
to be moved transversely on the converter. How far they must be moved is as
yet unknown.
Initial experiments are underway on the Integrated Test Stand to
measure expansion velocities and compare these measurements to 2-D
hydrodynamic calculations. A streak camera and optical back lighter are used
to determine the temporal evolution of axial expansion velocities. At
present, experimentally measured expansion velocities are a factor of 3
higher than calculations would indicate. Efforts to resolve this discrepancy
are underway and are critical to ensure confidence in calculations and
predictions for conditions which will be reached at DARHT.
Two slides describing this project in more detail
are available by clicking HERE (PDF-118Kb).
Contact: David M. Oró
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