Status and Plans for OMEGA Shot Experimental a Yield

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					                Status and Plans for OMEGA




          Shot 33687                     Shot 33220
   Experimental (a ~ 4)    YOC    Experimental (a ~ 40)   YOC
   Yield (1n): 4.6 ´ 109   23%    Yield (1n): 1.78 ´ 1011 ~115%
   TCC offset: 36 mm                          40 mm


R. L. McCrory                       Forum on the Future of Fusion
Director                                Fusion Power Associates
University of Rochester                          Washington, DC
Laboratory for Laser Energetics            19–21 November 2003
Collaborators


 T. C. Sangster, M. Alexander, R. S. Craxton, J. A. Delettrez, L. M. Elasky,
  R. Epstein, A. Frank, V. Yu. Glebov, D. R. Harding, S. Jin, J. P. Knauer,
    R. L. Keck, S. J. Loucks, L. D. Lund, P. W. McKenty, R. L. McCrory,
        F. J. Marshall, D. D. Meyerhofer, S. F. B. Morse, S.P. Regan,
               P. B. Radha, S. Roberts,W. Seka, S. Skupsky,
                V. A. Smalyuk, J. M. Soures, and M. Wozniak
                       Laboratory for Laser Energetics
                          University of Rochester


            J. Frenje, C. K. Li, R. D. Petrasso, and F. H. Séguin
                     Plasma Science and Fusion Center
                    Massachusetts Institute of Technology


      N. Izimui, J. A. Koch, R. A. Lerche, M. J. Moran, T. W. Phillips,
                  G. W. Schmid, C. Sorce, and A. Warwick
                   Lawrence Livermore National Laboratory
 Summary
LLE is making significant progress in direct-drive
inertial confinement fusion research


     • Adiabat-shaping techniques will allow
         – lower-adiabat (higher-compression) implosions on OMEGA and
         – higher-gain target designs for the NIF.
     • Cryogenic target experiments are showing promise.
         – Ice-surface roughnesses are approaching 1 mm rms,
           ignition specifications.
         – The first wetted-foam target has produced the highest
           cryogenic D2 neutron yield.
         – 2-D simulations are in good agreement with experimental
           observations.
     • OMEGA EP (two ps beams, 2.6 kJ each) will extend LLE’s research,
       including integrated fast-ignition experiments.



E12724
The NIF base-line direct-drive ignition target is
a thick DT-ice layer enclosed by a thin CH shell

         • Target designs are characterized by the isentrope parameter a:
                                  Electron pressure
                        a =
                             Fermi-degenerate pressure


     1.69 mm                           CH
                      DT ice                Laser energy    1.5 MJ
                                            Pulse shape     a=3
         1.35 mm
                                            Gain            45
                      DT gas                Yield           2.5 ´ 1019
                                            rRpeak          1.3 g/cm2
                                            <Ti>n           30 keV
                                            Hot-spot CR     28
                                            Peak IFAR       60

E11250
The OMEGA cryogenic implosion campaign is a staged
program leading to verification of scaled-ignition
performance with DT fuel by the end of FY05


          • The program is driven by three main objectives:

               – Validation of target performance for the lowest
                 effective adiabat

               – Minimization and absolute characterization
                 of DT cryogenic-layer roughness

               – Use of cryogenic DT targets in OMEGA implosion
                 experiments



                       Most of the experimental work
                       will be accomplished with D2.


TC6458a
Smoother ice layers allow OMEGA cryogenic implosion
campaigns to examine ignition-scaled targets at lower adiabats

          NIF: 1.5 MJ
                          ~ 3 mm CH                 103
                                                                   Pfuel
            DT ice        1.69 mm                              a=
                                                    102           PFermi    NIF




                                       Power (TW)
                        1.35 mm
            DT gas                                  101

                                                                    OMEGA
                                                    100

                                                    10–1
                                                           0    2     4    6      8   10
    OMEGA: 30 kJ
                           ~ 5 mm CH                                Time (ns)
           D2 ice       0.46 mm
                     0.36 mm                               Energy ~ radius3;
             D2                                            power ~ radius2;
             gas
                                                             time ~ radius

E11251f
The OMEGA cryogenic implosion campaign
is examining scaled-ignition target designs
employing two ablator concepts


                                                   3 mm CH

                    3 mm CH                             CH (DT)4      132
                                                           DT
                                                                     281
                              DT       340                 DT
                                                          vapor
                              DT
                             vapor               1784              1368
                     1693
                                     1350

          Gain = 45                    Gain = 67
          Absorption = 60%             Absorption = 90%

                         “All-DT”                  “Wetted-foam”



TC5787k
Cryogenic target implosions require significant
engineering and development


• Cryogenic implosions have been carried out on OMEGA for ~3 years.

• Significant obstacles have been overcome
         – cryogenic target transport
         – target survival
         – target layer survival

• The final issue has been to minimize target vibration at shot time.




                                        Fielding cryogenic targets is very
                                        difficult and requires a lot of time
                                        and effort.



I1420a
Recent D2-ice layers with IR heating are approaching
the NIF 1-mm rms requirement

                Surrogate target
                                                                     Average spectra for 23
                                                                     different angular views
                                                                     of the same cryo target
                                                          100




                                   Power spectrum (mm2)
                                                          10–1                Ice layer
                                                                              1.7-mm rms
                                                          10–2

                                                          10–3
                                                                       Outer shell
                                                          10–4         0.35-mm rms

                                                          10–5
                                                                 1             10          100
                                                                               l

              930-mm-diam OMEGA cryo target with
E12272d
             100-mm-D2-ice layer and 3.5-mm-CH shell
Accurate three-dimensional reconstructions
for simulations require many sampling traces
                                                                           Topographical
                                                                           reconstruction
                                                                                     +zW
                              (Courtesy of R. Stephens)


                             100
                                                                                              Y view
of an isolated feature (%)




                                                                            X view
                                                  Complete
  Detection probability




                                                  coverage                                   +xW




                                                                                                        sphericity/thickness (mm)
                                                  100 traces
                                                                                                   4




                                                                                                            Deviations from
                                       Standard 9-                                                 2
                              10       trace pattern
                                                                                                   0
                                                                                                   –2
                                                                                                   –4
                                                                                                   –6

                                                                      • Surface position is mapped
                               0
                                   1         10        100     1000     onto sphere.

                                            Mode number               • Data are smoothed.
                                                                      • Information for low-order modes
E12255b
                                                                        is provided.
A high-adiabat drive pulse has been used to understand
the effect of ice roughness on target performance

                                                              102
                               5 mm                                       Inner surface




                                             Spectrum (mm2)
                              100 mm                                      7.6 mm rms
                                                              100

                                                                     Outer surface
                           345 mm                             10–2   0.29 mm rms                      a ~ 25,
                                                                                                     27% YOC
                                                                                                      33413
                                                              10–4
                                                                  100         101             102
                                                                            Mode l
             25
                                                              102
             20
                                             Spectrum (mm2)

                                                                        Inner surface
Power (TW)




                                                                        3.9 mm rms
             15                                               100
                                                                                     Outer surface
             10                                                                      0.83 mm rms
                                                              10–2                                    a ~ 25,
              5                                                                                      36% YOC
                                                                                                      33599
              0                                               10–4
               0.0   0.5      1.0      1.5                       100          101             102

E12725
                     Time (ns)                                              Mode l
There is good agreement between high-adiabat implosion
performance and 2-D hydrocode simulations (DRACO)


          Shot 33413                                    a ~ 25
                             1.0
                                                  28900 (14 mm)
                             0.8
                                                   DRACO
                                                   (no offset)
                             0.6         20-mm


                       YOC
                                         offset

                             0.4
                                       40-mm          33599 (22 mm)
                                       offset
                                                                  33413 (42 mm)
                             0.2       33688 (40 mm)
                                                         33603 (29 mm)

                             0.0
                                   0       2     4    6   8    10            12
           300 mm                          rms ice roughness (mm)
                                             modes l = 1 to 16

TC6108b
Research at GA has produced a variety of dry foams
for ICF implosion experiments on OMEGA

                                  OMEGA target
                                                  4 mm (CH)
                                                 62 mm (CH4 D2)
            R/F foam                            65 mm (D2 ice)
          shells in liquid
                                               305 mm (D2 gas)
                                                              25
                                                              20




                                                 Power (TW)
                                                              15
                                                              10
                                                               5
                                                               0
                                                                0.0   0.5   1.0   1.5
                                                                      Time (ns)
                        An increasing fraction of experiments
                        at LLE will use wetted-dry-foam shells.
TC6464a
The first OMEGA cryogenic wetted-foam-target implosion
produced a surprisingly high cryogenic neutron yield

                                                 GMXI

                                                                              Experiment:
                                                                              Y1n = 1.74 ´ 1011
                                                                                    (114%)
                                                                              Y2n = 3.5 ´ 108
                                                                                    (30%)
                                                                              Tion = 5.2 keV
                                           1.0
                 Neutron rate (´ 1021/s)



                                                                  PTD
                                           0.8
                                                                              LILAC
                                                                      LILAC
                                           0.6                                Y1n = 1.5 ´ 1011
                                           0.4                                Y2n = 1.2 ´ 109
                                                                              Tion = 2.7 keV
                                           0.2

                                           0.0
                                              0.0   0.5     1.0       1.5   2.0
TC6460a                                                   Time (ns)
     2-D DRACO demonstrates good agreement in predicting
     target performance for shot 33600 (a ~ 4)
                                                                                    100
                          DRACO 2-D density   Density                                            2-D DRACO azimuthal            MIT




                                                           Areal density (mg/cm2)
                 150      near peak burn,     (g/cm3)                                            lineout of the total rR
                          shot 33600              8.03                               75
                          a ~ 4, 17 kJ
                                                  2.65                                      Range of measured
  R (mm)




                                                                                               rR’s (4 LOS)
                                                                                     50
                  75                              1.19


                                                                                    25


                   0                                                                 0
                  –100        –50        0     50        100                          0            60        120             180
                                     Z (mm)                                                       Azimuth (degrees)
                 101
                               Inner 3.9 mm rms                                                      Expt         1-D          2-D
                 100
Spectrum (mm2)




                 10–1                                                                     Y1n     4.30 ´ 109 2.68 ´ 1010 5.85 ´ 109
                 10–2                                                                     Y2n     4.43 ´ 107   1.40 ´ 109   5.97 ´ 107
                 10–3                                      a~4                            <rR>        52           63          55
                 10–4                                    16% YOC                          Tion       2.7          1.6          1.4
                 10–5                                     33600
                    100              101          102
     TC6465                         Mode l
A stability analysis* of the a = 4 design defines the ignition-
scaling performance window for cryogenic implosions

• The NIF gain* and OMEGA yield can be related by
               s 2 = 0.06 s2       2
                           l<10 + sl>10 ,
    where the sl’s are the rms amplitudes at the end of the acceleration phase.

                      1.2                                                                 103
                                                                                                 a=1




                                                                            Target gain
                                                                                          102
                      1.0                     NIF (a = 3)                                          2
   Normalized yield




                                                                                                   3
                                                                                          101
                      0.8                                                                          4
                                                                                      100
                      0.6                                                               1.0    1.4   1.8
                               OMEGA                                                Incident laser energy (MJ)
                      0.4       (a = 4)
                                                   33687
                      0.2                  33600            28969
                      0.0
                         0.0        0.5     1.0       1.5             2.0                       2.5    3.0
                      1-THz, 2-D SSD with PS,        s (mm)
                      1-mm-rms ice roughness,
                      840-Å outer-surface roughness,
                      1% rms power imbalance
                                                                    * P. McKenty et al., Phys. Plasma 8, 2315 (2001).
E12008g
 Scaling gain with s allows the formation of a global
 nonuniformity budget for the direct-drive point design

                                                               Sum-in-quadrature
         2
                      Current NIF                         40
                     specifications




                                                  Gain
                                                          20

                                                           0
                                                               0    1      2
s (mm)




         1                                                          s (mm)

                                                                  Imprint
                                                         Applied SSD bandwidth
                                                         (2 color cycle ´ 1 THz)
                                                         On-target power
                                                         imbalance (´ 2% rms)
         0                                               Inner-surface
         0.0   0.5        1.0         1.5   2.0          roughness (´ 2-mm rms)
                       Multiplier                        Outer-surface
TC5577a
                                                         roughness (´ 80 nm)
 Adiabat shaping reduces ablative Rayleigh–Taylor growth1

                      For DT foils:2 gRT = 0.94 kg - 2.6 kVa , where Va ~ a3/5.

      Pfuel
  a=                                       • t=0       Picket creates a strong shock.
     PFermi
                                           • t = tp    Rarefaction wave (RW) is
                                                       launched at t = tp.
                            a=2                                   Pressure
             20                                         Initial
                                                        shock                                   Laser
                                                                   Adiabat af
Power (TW)




             15

             10                            • t = tRW RW meets the shock.
              5                            • t > tRW Shock strength decreases in time.
                                                                         af
              0
                  0     1         2    3
                                                       Decaying
                       Time (ns)                       shock

                                                                       as
                                              1 V. N. Goncharov et al., Phys. Plasmas 10, 1906 (2003).
                                                        2 R. Betti et al., Phys. Plasmas 5, 1446 (1998).
 TC6372a
Picket results have led to examining lower-adiabat,
NIF and OMEGA-scaled ignition designs

                                    5 mm                  Imprint simulations
                                   80 mm        ORCHID: l = 2–200, DPP + PS, 1-THz SSD
                                                        300
                                                                           No picket
                                345 mm                                                       s > 10 mm
                                                        200




                                               R (mm)
                                                              290                             r (g/cc)
                                                                                                  4.20
                                                        100
                                                              250
                                                                60         100
             20                                           0
                      a=2                               300
             15                                                                   Picket
Power (TW)




                                                        200
                                               R (mm)
             10                                               290
                                                                                                  0.10
              5                                         100                                  s = 1.12 mm
                                                              250
                                                                60         100
              0                                           0
                  0         1      2       3                  0      100         200   300
                            Time (ns)                                 Z (mm)
                  Significant effort will be devoted to picket implosions in FY04.
TC6341a
Direct-drive target stability is dramatically
improved when adiabat shaping is applied


         2
                                                         40
                         Current NIF
                        specification
             With
s (mm)




                                                  Gain
         1   picket
                                                         20




         0                                                0
          0.0     0.5       1.0       1.5   2.0               0   1        2
                         Multiplier                               s (mm)

                The benefit of pickets has been confirmed in NRL
                              and LLNL simulations.
  TC6339b
Polar-direct-drive simulations for the NIF are starting
to show the onset of hot-spot formation

                               Standard pointing    23.5°         30°              Repointing        23.5°     30°
                                with x-ray-drive                    50°             for PDD
                                 configuration   23.5°                                            23.5°              50°
                                                 30°                                              40°
                                                 50°
                                                                                                  75°




                                                                                       Max rR ~ 1 g/cm2
                               1.4
    Intensity (´ 1015 W/cm2)




                                                                             100                                      99
                               1.2
                               1.0                                                                                    85




                                                                                                                           Density (g/cm3)
                               0.8            Q = 90°
                                                                    r (mm)

                                                                                                                      71
                                                                                       4 keV
                               0.6                                            50                                      57
                                                                                           6
                               0.4                       0°                                                           43
                               0.2                                                     8
                                                                                                                      0
                               0.0                                             0
                                     0   2      4        6    8                    0            50           100
I1423a                                       Time (ns)                                         z (mm)
 OMEGA EP
The OMEGA EP beams will be located
next to the existing OMEGA facility
                                                 OMEGA
                                             target chamber
                          OMEGA laser bay



                                                                     OMEGA EP
                                                                     target
                                                                     chamber

                                     Compression
                                        chamber                      Main
                                                         Beam        amplifiers
 Short-pulse         Short-pulse   Short-pulse            1, 2
 performance           beam 1        beam 2

 Short pulse (IR)    1 to 100 ps   35 to 100 ps
                                                                     Booster
 IR energy                                                           amplifiers
 on-target (kJ)          2.6           2.6

 Intensity (W/cm2)    6 ´ 1020      ~ 4 ´ 1018          OMEGA EP
                                                         laser bay
G5546h
OMEGA EP will be an important new tool
in LLE’s experimental arsenal

• Significant progress has been made                • Devlopment of radiographic
  toward “hot-spot” ignition.                         diagnostic capability for HEDP
                                                      and the NIF
         Capsule
                                                                        Short
                                                                        pulse
                            Diagnostic capability
                            within existing OMEGA
                            target chamber
         Laser                                                                      X rays
         beams


• Validation of “fast ignition”                     • Ultrahigh-intensity research
  with scaled cryogenic capsules                      capabilities
                    Hole
                   boring   Ignition                                             e+e–
                                                                         B
                                                          Intense                  e–
                                                            laser


                                                                                 e+e–
                                                                    Electron acceleration
                                                                    + B-field generation
G5819b
OMEGA EP will perform integrated
cryogenic fast ignition experiments

                       300 g/cc,
                                                                 1000-MJ yield
                                                                                      • HEPW designs underway
                                                                                        at LLE, LLNL, and SNL.




                                                           NIF
                       92 kJ, 4 ´ 1019

               100           Fast ignition
                                                              Direct
 Target gain




                                                              drive
                                           NIF point
                                           designs                 100-MJ yield
                     200 g/cc,
                10   200 kJ, 2.5 ´ 1019                    v = 3 ´ 107                    Ignitor
                             150 g/cc,
                             330 kJ,
                                                                     Indirect
                             1.8 ´ 1019                              drive
                                v = 4 ´ 107                        10-MJ yield
                 1
                  0.1                            1.0                             10             OMEGA EP
                                         Driver energy (MJ)
                               Hole boring             Ignition
                Light pressure
                bores hole in                     10 kJ,
                coronal plasma.                   10 ps

      1-MeV electrons
        heat DT fuel
         to 10 keV,                                                                   60-beam
          300 g/cc                                                                    OMEGA
I1425a                                                                                          Under construction
An OMEGA direct-drive cryogenic target
is designed to give a density > 300 g/cm3



                                                       CH
                                                                          5.8 mm
                                                       DT
             101                                                          90 mm
Power (TW)




                                                      3 atm
                                           500 mm      DT

             100




               0   1       2       3   4
                       Time (ns)           Nearly identical to capsules
                                           being imploded now.

TC6195a
   The areal density achieved with an OMEGA cryogenic
   target is close to ignition conditions


                                                                                                             Ion temperature is well below
                                                                                                                 ignition requirements
                                                          0.6                                               6                              600
                          500                                                                                       Near stagnation
Maximum density (g/cm3)




                                                          0.5                                               5                             500




                                                                                    Ion temperature (keV)




                                                                                                                                                 Mass density (g/cm3)
                          400




                                                                 Total rR (g/cm2)
                                                          0.4                                               4                             400
                          300
                                                          0.3                                               3                             300
                          200                             0.2                                               2                             200

                          100                             0.1                                               1                             100

                           0                               0.0                                              0                             0
                           3.6   3.7   3.8   3.9   4.0   4.1                                                    0   10     20     30    40
                                       Time (ns)                                                                     Distance (mm)


                                        A 1-MeV electron has a range of about 0.4 g/cm2.
   TC6196a
 The fast-ignitor beam creates a burst of neutrons
 that can be used for diagnostic development

                                        r = 500 g/cm3                          400-J pulse
                                        10-mm radius                          10-mm radius


                                             1 kJ                           250 g/cm3
                        1026            Y = 2.4 ´ 1015                    Y = 4.6 ´ 1015
Production rate (1/s)




                                                             400 J
                                                         Y = 1.2 ´ 1015
                        1025      No fast electrons                             No fast      500 g/cm3
                                    Y = 4 ´ 1014                               electrons   Y = 1.2 ´ 1015




                        1024
                          3.900    3.925     3.950 3.975 4.000 3.90 3.92 3.94 3.96 3.98 4.00
                                           Time (ns)                     Time (ns)

 TC6200a
 Summary/Conclusions
LLE is making significant progress in direct-drive
inertial confinement fusion research


     • Adiabat-shaping techniques will allow
         – lower-adiabat (higher-compression) implosions on OMEGA and
         – higher-gain target designs for the NIF.
     • Cryogenic target experiments are showing promise.
         – Ice-surface roughnesses are approaching 1 mm rms,
           ignition specifications.
         – The first wetted-foam target has produced the highest
           cryogenic D2 neutron yield.
         – 2-D simulations are in good agreement with experimental
           observations.
     • OMEGA EP (two ps beams, 2.6 kJ each) will extend LLE’s research,
       including integrated fast-ignition experiments.



E12724

				
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