Recent Progress in Heavy Ion Fusion and High Energy Density Physics

1
Recent Progress in Heavy Ion Fusion and High
Energy Density Physics

• B. Grant Logan
• On behalf of the Heavy Ion Fusion Science
• Virtual National Laboratory (HIFS-VNL)
• LBNL, LLNL, PPPL
• Presentation in two parts
• Heavy ion driven HEDP
• Heavy ion fusion potential
• Symposium on Recent Advances in Plasma Physics
• -- In Celebration of Ronald C. Davidson's 40
  Years of
• Plasma Physics Research and Graduate Education
• June 11, 2007

This work was performed under the auspices of
the U.S. Department of Energy by the University
of California, Lawrence Berkeley and Lawrence
Livermore National Laboratories under Contract
Numbers DE-AC02-05CH1123 and W-7405-Eng-48, and
by the Princeton Plasma Physics Laboratory under
Contract Number DE-AC02-76CH03073. HIFS-VNL A
collaboration between Lawrence Berkeley National
Laboratory, Lawrence Livermore National
Laboratory, and Princeton Plasma Physics
Laboratory, USA.
2
The HIFS-VNL pursues a unique approach to warm
dense matter physics driven by intense,
compressed ion beams
Maximum dE/dx and uniform heating at this peak
require short ( 1 ns) pulses to minimize hydro
motion. L. R. Grisham, Phys. Plasmas 11,

5727(2004). ?Te 0.5 eV in NDCX-I by FY09,
Te gt 1 eV in NDCX-II by FY10
Ion energy loss rate in targets dE/dx
30 mm 0.1x solid
z
3 mm
GSI 40-100 GeV heavy Ions? thick targets? Te 1
eV per kJ
Dense, strongly coupled plasmas _at_ 10-2 to 10-1 x
solid density are potentially interesting areas
to test EOS models (Numbers are disagreement in
EOS models where there is little or no data)
(Courtesy of Richard W. Lee, LLNL)
3
NDCX-I is being upgraded this year for first
mm-scale warm dense matter experiments in FY08,
initially below 5000 deg K.
NDCX-II, with 10X more beam intensity using ATA
parts, could be completed by FY10 with
incremental funding of 1.5 M
Building 58, LBNL
4
Highlights of the present heavy ion fusion
science program

• Compressed intense heavy ion beams in
  neutralizing background plasma in NDCX-I 200 ns
  down to 2 ns FWHM.
• Begun heavy-ion driven isochoric target heating
  experiments to 1 eV in joint experiments with
  GSI, Germany, to develop HEDP diagnostics.
• Unique diagnostic measurements of electron cloud
  effects on intense heavy-ion beam transport in
  both quadrupole and solenoid magnets.
• Computer simulation models that match the
  experimental results in both neutralized beam
  compression and e-cloud studies.
• ATA accelerator equipment sufficient for 3 to 6
  MeV NDCX-II next step for both warm dense matter
  and ion direct drive target physics experiments.
• In-house capability to run HYDRA code for NDCX
  target design support.

5
We are developing diagnostics and two-phase EOS
models in joint experiments with GSI for
isochoric heating expansion relevant to
indirect drive HIF target radiators, and to
droplet formation.
Final focus magnets
Visible ms camera frame showing hot target
debris droplets flying from a VNL gold target (
few mg mass) isochorically heated by a 100 ns,
10 J heavy ion beam to 1 eV in joint experiments
at GSI, Germany.
Measuring two-phase WDM EOS and expansion of
target materials _at_ 1 eV can benchmark/improve
models? science that is also relevant to
isochoric neutron heating effects in NIF high
yield shots.
6
NDCX WDM target chamber is designed and will be
installed later this year.
7
We have used the LLNL HYDRA code to show how
unique heavy ion direct drive hydrodynamics as
well as WDM can be studied on NDCX-II
r t0.4 ns
r t1 ns
r t3.5 ns
r t5 ns
r t7.5 ns
r t10 ns
T t0.4 ns
T t1 ns
T t3.5 ns
T t5 ns
T t7.5 ns
T t10 ns
Can modulated beams stabilize ion Rayleigh-Taylor
modes? (S. Kawata)
8
Heavy ion driven HEDP Conclusions

• Heavy Ion Fusion Science experiments on NDCX I
  are making outstanding progress in neutralized
  beam compression.
• Warm Dense Matter experiments are beginning
• -- Transient darkening experiments on HCX
• -- Metallic foam studies at GSI
• -- Target heating experiments (.2 - .5 eV) to
  begin this year on NDCX I
• -- 1 eV experiments on NDCX II by 2009 (assuming
  1.5 M
• funding increase)
• Hydrodynamics experiments for stability and ion
  physics deposition studies can be carried out
  on NDCX II and/or IB- HEDPX. Simulations being
  carried out.

9
Exploring application of new beam compression and
focusing advances for HEDP towards heavy ion
fusion.
(1) Neutralized beam compression and focusing
enables ablative direct drive with low range ions
at high beam-to-fuel-energy coupling efficiency gt
15 to 25 .

(2) High beam-to-fuel coupling efficiency enables
high rr gt 6 to10 g/cm2 T-lean fuel assemblies
that self-absorb most neutron energy at moderate
driver energies of 1 to 5 MJ.
(3) Self-breeding T-lean targets enable gt 90 of
the fusion yield captured into target shells for
low-cost direct plasma MHD conversion ?
ultimately low CoE lt coal or fission.
10
We are re-visiting T-lean targets from 10 years
agothis time in the context for heavy-ion
direct drive(From a recent MathCAD document
available upon request)
Heavy ion direct drive Target (spherical model
of proposed polar illumination)
Why direct drive? 1MJ energy stagnation fuel
assemblies needed for T-lean targets not
practical with low hohlraum or laser beam-to-fuel
energy coupling efficiencies!
11
Heavy ions with the right range can in principle
drive targets at the peak of rocket efficiency
like x-rays, but without the energy penalty of
conversion to x-rays, and with lower ionization
loss using H2 ablators.

• Pure hydrogen ablators for ion direct drive have
  only 13.6 eV ionization loss
• Beryllium ablators have 180 to 400 eV ionization
  (three to four electrons ionized)
• Laser coupling is reduced 2 x by electron
  transport form critical density to ablation front

Heavy ion beams can suffer more parasitic beam
losses on out-going ablation plasma than either
x-ray or laser photons -but overall coupling
efficiencies can still be several times higher
including this loss (up to 25 beam-to-fuel),
versus 3 for hohlraums (6 for close-coupled
hohlraums), and 10 for laser direct drive.
12
An IRE-scale new accelerator tool can explore
polar direct drive hydro physics with heavy ions
in parallel with NIF.
Concept 10 kJ direct drive implosion
experiments using two opposing linacs, each
with 10 pulses for variable picket fence pulse
shaping
Initial beam intensity profile Foam profile
shaper Final beam profile (shaped)
P2-shaped ablator
Three knobs to control P2 asymmetry with two
beams 1. Upstream GHz wobblers 2. Foam profile
shapers 3. Ablator shaping
Goal is implosion drive pressure on the Cryo D2
payload with lt 1 non-uniformity
13
High efficiency ion direct drive enables CFAR
plasma direct conversion at moderate yields
4
Est. 20 beam to fuel coupling eff.
Note key facts about the marriage of T-lean
targets (Max Tabak 1996) to CFAR MHD conversion
(1) Most T-lean target yield can be captured
for direct plasma MHD conversion, even down to
1MJscale DEMO drivers. (2) Plasma
conductivity is 104 times greater at 25,000 K
than at 2500 K? the extractable MHD conversion
power density su2, where u10km/s is the
plasma jet velocity, is gt30 times the power
density of steam turbine generators2. ?As a
consequence, the CFAR Balance of Plant cost can
be much lower, lt 80 M/ GWe!
(b)
14
Why add risk of advanced fusion energy conversion
if fusion has environmental advantages? Answer
fusion also has to be competitive in cost!
Consumers' willingness to pay more for
environmental advantages is limited!

• The greatest challenge coming from critics of
  fusion is
• competitive economics
• No one will ever buy
• a billion-dollar fusion heat source
• to replace a coal-fired boiler or fission
  reactor core

?But, what if direct conversion of fusion energy
could reduce billion-dollar balance of plant
costs 10X?
15
Summary of cost model for reference CFAR power
plant and DEMO updated for T-lean targets.
Based on ref 5 B. G. Logan, Lawrence
Livermore National Laboratory Report
UCRL-ID-110129 (July 1992)For modular solenoid
driver bldg cost, use last years study, ref6
B. G. Logan, "Small Modular Driver Study-url
www.osti.gov/servlets/purl/902800-eyJKrw/ )We
take the driver cost to be linear with driver
energy because of highmodularity.
16
Conclusions of a June 4, 2007 study Can we
afford ocean desalination to double fresh water
supply for twice as many people on a hot planet?

• 6 TWe of new electric power, half for 2500
  large-scale desalination plants and half for
  delivery worldwide, is required to provide a
  doubling of fresh water supply (10 km3/day) by
  desalination.
• A cost of electricity less than 0.03 /kWehr is
  required to meet the world affordability target
  price for water of 0.9 /m3 (based on lt 7
  GDP), by reverse osmosis desalination.
• Ocean desalination cannot be sustained with
  bio-fueled-engines for pumping? need massive
  nuclear fission then fusion electricity
  generation, at low CoE (2.3 GDP investment per
  0.01/kWehr).

17
Heavy ion fusion Conclusions

• The NIF ignition campaign using indirect-drive
  hohlraum as well as polar direct drive targets
  motivates exploring advanced targets for energy
  fusion energy.
• T-lean targets naturally convert neutron energy
  into plasma energy available for direct energy
  conversion.
• Fusion energy conversion into plasma with 10 x
  more energy/kg than possible with combustion can
  revolutionize MHD conversion efficiency and power
  density enough to replace steam cycles.
• Systems analysis suggests potential economics
  better than fission cost of electricity, and
  potential for hydrogen fuel production.
• The results of this preliminary study look very
  encouraging! As hydro code calculations at least
  roughly confirm the potential for high ion direct
  drive coupling, this work should be pursued
  further.

18

• BACKUP SLIDES
• for heavy-ion-driven
• HEDP

19
The neutralized drift compression experiment
(NDCX-I) continues to improve longitudinal
compression of intense neutralized ion beams
Shorter pulses (2.4 ns) obtained with new
Ferro-electric plasma source

Waveform were building may yield 250x
compression
Simulations predict higher compression with new
induction bunching module to be installed this
summer
V (kV)
60x compression measured, modeled
20
With eV-scale volumetric ion heating of foams and
solids a variety of physics is opened to
exploration

?These three process need both improved WDM
theory and well-characterized data, and so are
early candidates for experiments and modeling!
21
Key EOS parameters we are pursuing in the Warm
Dense Matter regime

22
Additional fundamental scientific opportunities
of WDM

23
Selected scientific questions that can be pursued
in NDCXI and II (R. More, J. Barnard, F.
Bieniosek)

• Quartz transient darkening emission and
  absorption experiment.
• ?What is the physical mechanism for changes in
  the optical properties of glass, as matter
  approaches the WDM regime?
• Measure target temperature, using a beam
  compressed both radially and longitudinally.
• ?How can we measure the thermodynamic properties
  of matter, heated by ion beams compressed in
  space and time?
• Thin target dE/dx, energy distribution, charge
  state, and scattering in a heated target.
• ?Can an ion beam (after it heats and exits a
  target) be used as a unique diagnostic tool for
  WDM exploration?
• Positive - negative halogen ion plasma experiment
  (kT gt 0.4 eV)
• ?Can unique states of matter be created with
  nearly equal quantities of positive and negative
  ions (and few electrons)?
• Two-phase liquid-vapor metal experiments (e.g. kT
  gt 0.5 - 1 eV for Sn)
• ?In the two-phase regime, what is the best way to
  make predictive simulations of the EOS and
  dynamics including the effects of droplets?

?See 2006 international workshop on
accelerator-driven warm dense matter
(http//hifweb.lbl.gov/public/AcceleratorWDM/Table
OfContents.html )
24
Improving NDCX-I for FY08-09 warm dense matter
experiments
New
New
New
New plasma configuration
New
25
Simulations (Adam Sefkow, PPPL) show smaller
NDCX-I focal spots will be possible with high
field focusing solenoid to be installed FY07
Plasma density gtgt beam density prescribed
26
With new improved bunching module to be installed
later this year, plus a higher field 15T focusing
magnet in FY09, NDCX-I is predicted to support
gt0.5 eV target conditions with 2 ns pulses
Actual achievable NDCX-I intensity for WDM
targets in FY09 will range between gt 0.15
J/cm2 (previous slide) and this simulation of
best possible case lt 4 J/cm2 .
27
Initial NDCX-I Target diagnostics

• Fast optical pyrometer
• Similar to GSI pyrometer, improved for faster
  response (1 ns) and greater sensitivity
• Temperature accuracy 5 for Tgt1000 K
• Position resolution about 400 micron
• Parts are being ordered to be assembled in FY07
• Fiber-coupled VISAR system now under test
• Martin Froescher Associates
• Sub-ns resolution
• 1 accuracy
• Hamamatsu visible streak camera with image
  intensifier
• Sub-ns resolution
• arrived Feb. 2007

28
Diagnostic development and testing VISAR for
NDCX-I
Nail gun
Light collection optics
Projectile
29
Formation of droplets during expansion of foil is
being investigated
Foil is first entirely liquid then enters two
phase regime.
Example of evolution of foil in r and T
DPC result
1 ns
0.8 ns
0.6 ns
0.4 ns
Temperature (eV)
gas
liquid
0.2 ns
2-phase
Vgas Vliquid
Density (g/cm3)
0 ns
Ref J. Armijo, master's internship report, ENS,
Paris, 2006.
Evolution of droplet radius, (Armijo et al, APS
DPP 2006, and in prep).
C. Debonnel and A. Zeballos are incorporating a
model for surface effects into hydrodynamics
code Tsunami
Logrf/r0
Loginitial radius r0 (cm)
30
Isochoric heating by ion beams can simulate
neutronic isochoric heating near NIF target (Dave
Eder, LLNL)
31
VNL porous target experiments at GSI have already
begun

• Replace target foil with porous material.
• Study effect of pore size on target behavior
  using existing diagnostics.
• Sample targets LLNL (Au, 50 nm), Mitsubishi
  (Cu, 50 micron).

32
Data analysis from GSI experiments is underway
(Bieniosek)

• Gold targets heated to about 6000 K (T-boil
  2435 K). Solid and porous gold targets show
  similar behavior (temp, 1.4 km/s expansion).
• Copper targets heated to about 3000 K (T-boil
  3200 K). Porous copper broke up into droplets.

Target
Beam
solid gold (note Bragg peak)
Porous gold
Porous copper before, during, after beam pulse
33
NDCX-II is the next step towards IB-HEDPX as well
as towards a heavy-ion-fusion direct drive
capability following NIF ignition
34
LLNL has donated 30 surplus ATA induction
modulesnow located at LBNL- sufficient for
NDCX-II
35
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36
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37
For a very modest investment of 1.5M, the
NDCX-II accelerator can be assembled and offer
high shot rates available for HEDLP science
users

• Precise control of beam energy deposition
• 5 uniformity over large sample sizes mm2
• Pulses long enough to achieve local thermodynamic
  equilibrium
• Maximum of NDCX experiments 100s of shots per
  day for user-available targets, 500 more/day
  for beam/diagnostic tune-up.
• Benign environment (no intense x-rays or neutrons
  that require shielding for people or diagnostics)
• NDCX-I-II would be dedicated to HEDLP users-not
  encumbered by other programmatic priorities
• Easily accessible site to visiting scientists and
  students

38
?Requires 1.5M incremental funding for hardware
to complete
39
S. Kawata (Utsunomiya U.) has proposed several
techniques to reduce RT growth in ion-beam-driven
direct drive
?These techniques can be explored on NDCX-II or
IB-HEDPX
40
Ion-driven hydrodynamic studies on cryogenic
hydrogen could be carried out on NDCX II or
IB-HEDPX scale facilities

• GSI first practiced ion-driven target
• hydrodynamics with cryogenic Xenon
• targets at beam intensities well below
• those required for full target ionization
• Direct drive hydrodynamics/RT physics can
  benefit from pump-probe double pulses

? Unique physics with ion drive using NDCX-II
41

• Backup slides for unique
• heavy ion fusion vision

42
Exploring a Unique Vision for Heavy Ion Fusion

• A quest for more efficient beam-to-fuel energy
  coupling
• via polar direct drive (25 overall), to enable
• ?Self-T-breeding, self-neutron-energy-absorbing,
  large rr,
• T-Lean targets _at_ moderate lt 4 MJ driver
  energies
• ?Efficient fusion energy coupling into plasma for
  direct MHD
• conversion with moderate yields lt 1 GJ
• ?Balance-of-plant costs 10X lower than steam
  cycles
• (e.g., lt 80 /kWe instead of 800 /kWe)
• ?CoE low enough (lt3 cts/kWehr) for affordable
  water and
• H2 fuel for 10 B people on a hot planet.
• ?Enough fissile fuel production for 38 LWR's per
  GWfusion
• if uranium gets too expensive meantime
  (Ralph Moir)
• ?This may take longer to develop, but an end goal
  worth the effort!

43
Exploring a Unique Vision for Heavy Ion
FusionThis presentation will summarize selected
highlights of available technical document LBNL
report Direct Drive T-Lean Targets MHD
Conversion May 18, 2007
This work is based on analytic and approximate
numerical MathCAD models, to guide beam
requirements for 1 and 2-D implosion
calculations being initiated by John Perkins
at LLNL
Some additional references 1 TABAK, M.
Nuclear Fusion 36, No 2 (1996) 2 ATZENI,
S., and CIAMPI, C., Nuclear Fusion 37, 1665
(1997) 3 LOGAN, B. G., Fusion Engineering
and Design 22, 151 (1993) 4 ATZEHI, S. and
MEYER-TER-VEHN, J., "The Physics of Inertial
Fusion" Clarendon press-Oxford, 2004
44
Interfacing with the nuclear fission renaissance
underway beat them (CoE) or join them (hybrid
fuel) is not a choice!

• Sequence of fission ? affordable fusion is
  compelled if fraction of GDP for energy is to be
  constrained for economic development.
• Uranium ore / fission breeder cost may become a
  fission fuel cost issue for the last decades of
  final transition from fission to fusion.
• ?A successful fusion strategy has to be (after
  fusion reliability is demonstrated in a fusion
  DEMO)
• First, join them be prepared to provide extra
  neutrons for fissile breeding ASAP in case
  fission fuel cost becomes an economic burden on
  society
• Then, beat them (succeed them) ultimate
  Cost-of-Electricity lower than fission (a) lower
  fuel cost, plus (b) lower cost direct conversion.

45
Driver model for costs obtained from previous
May1, 2006 systems analysis describing three
major thrusts for improving HIF (1) 1 MJ
targets with gains gt40(2) Modular HIF driver
development path(3)Liquid vortex chambers
?might satisfy Demo-small,-then grow large
desired development path objective for low unit
cost electricity hydrogen fuel production.
46
First ignition tests in NIF will be indirect
drive, but polar direct drive tests will soon
follow.
Meyerhofer (8-29-06) We expect ignition in
polar direct drive on NIF soon after first
ignition with indirect drive. Marshall, Craxton
(11-06-APS) -showed new Rochester results on
their 2-sided, polar direct drive experiments
measuring 80-90 of the yield with full 4Pi
drive.
May need Saturn ring at equator
47
The HIFS-VNL now has sufficient ATA parts on site
to build NDCX-II, enabling new double-pulse
direct-drive experiments
Thanks to LLNL Beam Research Program, we have
enough parts for 6 MeV of acceleration. Our main
cost item would be to replace solenoids to 1.5 to
2 T (6 m x 100K/m 600K)
TARGET CHAMBER
14 ATA-II INDUCTION CELLS
DIAGNOSTICS BOXES AND PUMPING
SHORT PULSE INJECTOR
SHOWN USING AVAILABLE ATA CELLS. Blumlein pulsed
power modules not shown.
?NDCX-II Validates CD-0 pre-requisite for
IBX-HEDPX
The Heavy Ion Fusion Science Virtual National
Laboratory
48
Double-pulse planar target interaction
experiments should reveal unique heavy-ion
direct-drive coupling physics
Payload and ablator D2 layers are doped with
different impurities to diagnose optical depth
modulations
Solid D2 payload
Ablator D2 layer gt than initial ion range
Time just before first pulse
First ns ion beam pulse dE/dx (beam enters from
the right)
RT bubbles spikes grow measurable amplitudes.
(1) Can upstream beam GHz RF modulation reduce
RT? (2) Do RT non-uniformities in ablation plasma
smooth out with time and distance (any ablative
stabilization)?
Time 10 ns later before second pulse arrives
(1) Rocket science what ion range/ablator
thickness maximizes hydro implosion efficiency
with later ion pulses interacting with ablation
layer mass? (2) How is RT growth affected (any
cloudy day effect?)
2nd higher energy ion pulse arrives, and stops
partly within ablation blow-off (in 1-D)
?Second ns ion beam pulse dE/dx
With laser direct drive, later pulse ablates at
fresh critical density layer further left
With laser direct drive, light transmits through
most coronal plasma? Absorption in inverse
bremsstrahlung layer lags behind dense shell
trajectory
49
Max Tabak, Stefano Atzeni, John Perkins and I
have been searching a decade for a self-T
breeding target with direct conversion potential
to make fusion truly unique
1
2
3
L. John Perkins Advanced LASNEX model Advanced
fuel IFE LLNL (1998) unpublished?
4
Mission-Impossible Quest? Yes, but very good
company!
We all got discouraged when we estimated that
large energy drivers gt 10 MJ might be required,
and associated large fusion yields ( many GJ)
. so we mostly stopped working on this the last
several years.. until Max and I vowed to go
back and dig deeper on this quest in a new series
of Skunkworks meetings!
50
The Tabak-based MathCAD model _at_ adiabat a1.5
compares well with the closest Atzeni/ Ciampi
T-lean run for marginal net T-sufficiency at
adiabat a1.5, both cases near 1 molar fraction
of tritium, and for 1 MJ fuel assembly energy
(our reference case for a CFAR power plant). The
Tabak-based model is based on isobaric DT hotspot
ignition, while the Atzeni/ Ciampi model is based
on isochoric fast ignition. We assume the Tabak
model would also be consistent with the new
Betti-Perkins variant of hot spot ignition with a
late shock but without needing a fast igniter
pulse (easier for ion beam drive), in case
implosions don't quite reach the 10 keV hot spot
DT temperatures postulated in the beginning of
Max's burn calculations.
51
Large ?r T-lean targets (?r 10 g/cm2 2X
neutron scattering m.f.p.) enable plasma MHD
conversion at moderate fusion yields lt 1 GJ

• Compact Fusion Advanced Rankine Cycle (CFAR)
  study 3 found efficient MHD conversion (gt 50)
  for dense (10 to 100 bar) plasmas containing
  alkali component (Li or K) with optimal Te of 1
  to 2 eV. (Below that optimum Te, plasma
  conductivity decreases strongly with ionization
  fraction, and above that Te, plasma radiation
  losses reduce conversion efficiency).
• Solid target shells of chosen working material
  previously had to be thick enough to stop 14 MeV
  DT neutrons ?fusion yields typically several 10's
  of GJ to vaporize and ionize shell masses of
  100's of kg into an average 1-2 eV Te.
• Ref 3 neglected the neutron deposition within
  the target ?r, (typically 10 to 20 for DT
  targets) ?required large target shell masses to
  capture 14 MeV neutron energy ?forced very large
  fusion yields (10's of GJ).
• ?Creating T-lean fuel assemblies with
  large ?r10 g/cm2 at higher beam-to-fuel coupling
  efficiencies ?reasonable driver energies and
  fusion yields possible.

Flibe target Shell for DT target Ref3
LiH target shell for T-lean target
..
52
In T-lean targets, D (d,n) T side reactions in
main D2 fuel layer makes many more neutrons per
MJ fusion yield than for DT
?Ralph Moir estimates up to 38 LWRs can be
supported by fissile fuel bred by one fusion
hybrid using T-lean targets!
53
Large T-lean column densities (rr 10 g/cm2)
stop a significant fraction of neutrons, so a
small target shell with lt 1 MJ fusion yield can
capture gt 90 of the yield into plasma useful
for MHD direct conversion.
54
Summary of T-lean target parameters, (Fuel
assemblies at stagnation, burn parameters,
neutron production, and energy conversion results
with the MathCAD model benchmarked on Max
Tabaks Case C isobaric ignition-burn
calculations with 1 molar T fractions (here
adiabat a 1.5, H2 ablator, Mo/Mf 5
).?Note net T production begins at Ef 0.2
MJ, which we choose to evaluate as a DEMO

55
A numerical implosion model specifies ablation of
30 layers of H2 ablator at rates corresponding to
the peak rocket efficiency required for Tabaks
model implosion velocity of 3.107 cm/s.
? Working backwards, the model then calculates
the incident ion beam requirements needed to
provide the required ablation rate.
56
The model includes parasitic beam loss on ablated
plasma.
The model tracks the column density of ablated
plasma rra accumulating during the pulse
and solves for the increasing ion range
required during the pulse to penetrate the
ablated plasma corona and still provide the
required rate of H2 ablation drive.
?Increasing ion range vs. time is synergistic
with velocity chirp for longitudinal beam
compression!
57
Implosion characteristics for the DEMO
case(Adiabat a 1.5,fuel energy Ef 0.2 MJ
Implosion velocity 3.5x107 cm/sH2 ablator,
Mo/Mf 5)
58
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59
Figures of merit for plasma MHD conversion
(1993 CFAR study 3). LiH is preferred shell
material for current work because of higher su2
and lower radiation loss at given Te and
pressure. With shorter 50 ms pulsed MHD flow
times in current work, lower radiation losses
allow lower average transient plasma pressures
lt 100 atm.
60
By coupling inertial fusion energy directly into
the working plasma fluid at gt 10 times the
specific energy possible with combustion, CFAR
plasma temperatures can be 10 times higher,
leading to power densities gt100 times that of
previous MHD, and gt 30 times that of
conventional steam turbine generators.
61
Development of liquid protected chambers can be
done with modest budgets using scaled,
hydrodynamically-equivalent water flows.
Vortexpotential high pulse rates?
(1) Short average flow paths and liquid resident
times
(2)Many inlets and outlets
(3) Turbulent mixing absorbs high surface heat
fluxes
Given fast (lt1 to 10 ms) plasma clearing of
cavity (1)(2)(3) very high potential
chamber thermal power densities
UCB experiments
62
Serendipity with special overcoated hohlraum
targets, the new magnetized vortex chamber is
ideal to confine target plasma well enough to
neutralize the beam on subsequent shots (even
after 20x decay)
Assume 1 m3 cavity volume, 2 m2 liquid cavity
surface, 40 MJ magnetic field energy damps
turbulence from 30-40 of fusion yield captured
into a special target coated with a thick Flibe
layer
Liquid Flibe
Dense vapor
Magnetized resistive plasma
Constant pressure (r) to liquid (after a few
bounces)
Density gradient
Temperature gradient