Target and Chamber Technologies for DirectDrive LaserIFE

1
Target and Chamber Technologies for Direct-Drive
Laser-IFE

• Presented by A. René Raffray
• Scientific Investigators
• M. Tillack, R. Raffray, F. Najmabadi
• University of California, San Diego
• 1st RCM of the CRP on Pathways to Energy from
  Inertial Fusion - an Integrated Approach
• IAEA Headquarters
• Vienna
• November 5-9, 2006

2
Proposed Work Within Context of High Average
Power Laser (HAPL) Program
Multi-institution Activities led by NRL with
the Goal of Developing a New Energy Source IFE
Based on Lasers, Direct Drive Targets and Solid
Wall Chambers
System (including power cycle)
Target injection (engagement and surviva)
Blanket (make the most of MFE design and RD
info)
Dry wall chamber (armor must accommodate
ionphoton threat and provide required lifetime)
Final optics ( mirror steering)

• Modular, separable parts lowers cost of
  development AND improvements
• Conceptually simple spherical targets, passive
  chambers
• Builds on significant progress in US Inertial
  Confinement Fusion Program

3
Proposed Research(as part of HAPL Program)

• a) Target engagement. We will develop and
  demonstrate systems to track direct-drive targets
  in flight and to steer multiple driver beamlets
  onto the targets with the precision required for
  target ignition. Bench-top experiments will be
  performed in order to demonstrate the feasibility
  of these systems and to characterize their
  performance.
• b) Chamber design studies. We will develop
  chamber design concepts that integrate armor and
  structural material choices with a blanket
  concept providing attractive features of design
  simplicity, fabrication, maintainability, safety
  and performance (when coupled to a power cycle).
  Advanced concepts (including magnetic
  intervention) that could result in smaller less
  costly chambers, better armor survival and lower
  cost of electricity also will be investigated.
• c) Chamber armor thermomechanics. We will
  perform modeling and experiments on candidate
  chamber armor materials. The goal of this work
  is to develop solid armors capable of
  withstanding cyclic thermomechanical loading
  expected in direct-drive IFE chambers.

4
Target Engagement
5
Proposed Work Plan for a) Target Engagement
Year 1 Utilize lab-scale injection equipment to
support the development of target engagement
methods. Field and test individual elements,
including Poisson spot detection, Doppler fringe
counting, glint alignment, fast mirror steering
and real-time software integration. Year
2 Combine benchtop systems and extend
performance. Year 3 Perform integrated
demonstration of target engagement. Install all
engagement systems on a prototype injector using
full-speed electronics, full-power light sources
and full-aperture optics.
6
Target engagement research is performedin
collaboration with General Atomics
L. Carlson1, M. Tillack1, T. Lorentz1, J.
Spalding1 N. Alexander2, G. Flint2, D. Goodin2,
R. Petzoldt2 (1UCSD, 2General Atomics)

• Purpose To individually demonstrate successful
  table-top experiments of key elements, then
  integrate together.
• Final goal Provide a hit-on-the-fly target
  engagement demo meeting accuracy requirements.

• Power plant requirements
• 20 µm engagement accuracy in (x,y,z)
• 20 m standoff to final optic
• 5-10 Hz rep rate

7
Benchtop experiments simulate all of the key
elements of a power plant engagement system
R. Petzoldt, et al., "A Continuous, In-Chamber
Target Tracking and Engagement Approach for Laser
Fusion," 17th ANS Topical Meeting, to be
published in Fusion Science and Technology.
1
3
5
5

• Poisson spot, fringe counting, crossing sensors,
  verification
• Provide in-flight steering instructions
  diagnostic, backup.
• Glint coincidence sensor
• Aligns beamlets provides final steering
  instructions

4
2
8
1. Transverse target motion is tracked using
Poisson spot centroiding
2) Brightness/contrast adjustment 1 ms
1) Capture image 1 ms
3) Threshold pixels above a certain value 4 ms
4) Remove border objects 2 ms
6) X,Y centroid computed with lt 5 µm error (1?)
1 ms

• Goal is to know centroid position to 5 µm every
  5 ms
• Looks achievable

5) Particle filter 1 ms
9
2. Fringe counting provides continuous z-axis
tracking, with accuracy goal of 1 part in 106

• A Michelson interferometer is used, with noise
  mitigation, signal processing and modifications
  for plane/spherical wave mixing.

Fringe count repeatability over 5 ?m using a
4-mm steel sphere

• So far, operation is limited in range and
  standoff (power, noise, bandwidth, )
• May predict velocity (vs. full z-axis tracking)

10
3. Crossing sensors initiate fringe counting and
may be sufficiently accurate to supplant the
interferometer
Sphere dropping mechanism

• New real-time operating system reports on-the-fly
  placement repeatability of 45 µm (1?) at C3.
• gt Sufficiently precise to trigger glint laser

-75 -50 -25 0 25 50 75
11
4. To demonstrate successful engagement, we
developed a high-precision verification system
1 µm precision when the target is within the 4
beamlets
target eclipses verification beamlets
(Diffraction-limited beamlet waist 75 µm)
12
5. The glint system provides final position
update and closes the beam steering loop

• Stationary demo performed with 18 µm accuracy in
  8 ms
• Full demonstration in progress

7 ns
Optics In Motion FSM
1) Fast steering mirror keeps alignment beam
centered in the coincidence sensor. 2) Glint
return provides error between alignment beam
actual target position 1-2 ms before chamber
center. 3) Error signal provides final
correction to FSM.
3
2
1
13
Time sequence of tracking engagement demo -
START
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
Time sequence - END
24
Chamber Design Studies
25
Proposed Work Plan forc) Chamber Design Studies
Year 1 Perform initial scoping studies of
advanced chamber options (including blanket and
armor). Possible design scenarios range from
large chambers without a protective chamber gas
to smaller chambers with magnetic intervention.
Studies include concept development and
sufficient scoping design analysis to allow for a
reasonable assessment of each concept based on
key criteria including performance (when coupled
to a power cycle), lifetime, fabrication, safety
and maintenance. Year 2 Conclude scoping
studies and perform assessment and comparison of
different chamber options to converge on the most
attractive concept(s). Develop possible design
solutions for ion dumps in the case of magnetic
intervention. Year 3 Perform detailed design
analysis of preferred concept(s) including more
detailed study of chamber integration (blanket,
armor and ion dumps as required in the case of
magnetic intervention) and design interfaces
(ancillary coolant, power cycle and assembly
maintenance requirements).
26
Design and Analysis Based on 350 MJ-Class
Baseline Direct-Drive Target Spectra
Energy partition - Neutron 75 - Ions
24 - X-rays 1
27
Energy Deposition Profile in W, SiC and C Armor
for 350 MJ-Class Baseline Target Spectra Spectra
in a 10.75 m Chamber
Chamber wall
Target micro-explosion
X-rays Fast debris ions Neutrons
Lifetime is a key issue for armor - High T and
dT/dx - Ion implantation (in particular He)
28
Ion Power Deposition Profile in W Armor
Debris ions
Fast ions
Time of flight effect due to energy range of
ions
Calculation based on 0.1 ?s time increment
29
Temperature History and Gradient for W Armor in a
10.75 m Chamber Subject to the 350 MJ-Class
Baseline Target Threat Spectra
1-mm W on 3.5 mm FS at 580 C No chamber
gas Peak temperature 2400C
1 mm thick W armor
30
Armor Survival Constraints Impact the Overall IFE
Chamber Design and Operation
W temperature limit of 2400C assumed for
illustration purposes (1.2 J/cm2 roughening
threshold from RHEPP results) Limit to be
revisited as RD data become available
Desirable to avoid protective chamber gas
based on target survival and injection
considerations
Large chamber for W survival Other advanced
concepts for more compact chamber and armor
survival, e.g. - Magnetic intervention - Phase
change armor
Example chamber parameters for 0 gas
pressure - Yield 350 MJ R10.5 m Rep. rate
5 for 1750 MW fusion
31
Self-Cooled Li Blanket for Large Chamber

• Large chamber size led to the division of
  blanket modules in two (upper and lower
  halves).

The design is based on an annular geometry with
a first Li pass cooling the walls of the box and
a slow second pass flowing back through the large
inner channel.
32
Self-Cooled Li Blanket Coupled to Brayton Cycle
through a Heat Exchanger

• Example results for regular FS (Tmaxlt550C) and
  ODS FS (Tmaxlt700C)

33
Advanced Chamber Based on Magnetic Intervention
Concept Using Cusp Coils
Use of resistive wall (e,g SiC) in blanket to
dissipate magnetic energy (70 of ion energy can
be dissipated in the walls). Dump plates to
accommodate all ions but at much reduced energy
(30). Dump plates could be replaced more
frequently than blanket.
Chamber/blanket study underway - SiCf/SiC as
structural material - Pb-17Li and flibe as
breeder/coolant - Other?
34
It Could Be More Advantageous to Position Dump
Plate In Separate Smaller Chamber
Hybrid case Dry wall chamber to satisfy
target and laser requirements Sep
arate wetted wall chamber to accommodate
ions and provide long life Have to make
sure no unacceptable contamination of
main chamber
Could use W dry wall dump, but would
require large surface area and same problem
with thermomechanical response and He
implantation Could allow melting (W or low MP
material in W)
35
b) Chamber armor thermomechanics
36
Proposed Work Plan forb) Chamber armor
thermomechanics
Year 1 Perform armor thermomechanics simulations
experiments for a range of laser energy (peak
sample temperature) and a variety of shot rates
(10 to 105) for powder metallurgy tungsten
samples. Year 2 Perform armor thermomechanics
experiments on different candidate armor material
such as single-crystal tungsten. Year 3 Perform
armor thermomechanics experiments on candidate
armor material bonded to candidate first wall
material (e.g., tungsten bonded to ferritic
steels).
37
Chamber Armor Thermomechanics Experiments
Dragonfire Laser Facility

• F. Najmabadi, J. Pulsifer
• UC San Diego

• Objective
• Develop and field simulation experiments of the
  thermo-mechanical response of the first wall
  armor of an IFE chamber to target fusion yield.
• Description
• A laser generates on the test specimen similar
  surface temperature and temperature gradients
  found in an IFE chamber wall (e.g. YAG laser with
  a rep rate of 10 Hz).
• Surface temperature as well as mass ejecta from
  the specimen is measured in-situ and in real
  time.
• Material response of specimen is determined after
  laser exposure by a variety of microscopy
  techniques.

38
Facility Description
INSIDE VACUUM
OUTSIDE VACUUM
translator electronics
39
Optical thermometer measures surface temperature
while QCM measures mass ejecta
40
In-situ microscopy allows us to monitor
microstructure evolution during testing
Basler camera and K2 Infinity microscope 1280x1
024 resolution 25 fps STD
objective (higher mag available)
USAF resolution target - 64 line pairs/mm - 16
?m resolution
41
Some results with powder metallurgy tungsten
Sample behavior changes at 2,500K
42
Damage appears at 2,500K (not correlated with ?T)
12A, 100mJ, 773K, Max 2,200K (1,400K DT)
14A, 150mJ, RT, Max 2,500K (2,200K DT)
11A, 200mJ, 773K, Max 3,000K (2,200K DT)
15A, 150mJ, 773K, Max 2,700K (1,900K DT)
43
Effects of Shot Count and Temperature Rise
14A, 150mJ, RT, Max 2,500K (2,200K DT)
15A, 150mJ, 773, Max 2,700K (1,900K DT)
105 shots
103 shots
104 shots
44
Effects of Shot Count and Temperature Rise
14A, 150mJ, RT, Max 2,500K (2,200K DT)
11A, 200mJ, 773K, Max 3,000K (2,200K DT)
105 shots
103 shots
104 shots
45
Summary of Possible Collaborative Areas of
Interest

• Target engagement
• Chamber armor material development and testing
• Advanced chamber/blanket design study
• Power plant studies