Abstract

The sphericity and wall-thickness uniformity requirements of direct-drive inertial-fusion targets are of the order of less than 1%. These shells display self-interference patterns (SIP’s) when irradiated with a spatially incoherent, narrow-bandwidth light source and viewed with a compound microscope. These patterns are distinct concentric fringes when the target is uniform, whereas faint, distorted, or discontinuous fringes indicate a nonuniform target. We determined the wall thickness to within ±0.5 µm by counting the number of fringes in the SIP, independent of the outside diameter. Thickness uniformity is verified to an accuracy better than 0.05 µm. The wall thickness of gas-filled targets can be determined to this accuracy without knowledge of the type of gas or its pressure. The SIP fringe technique is used to select polymer shells typically of 800- to 1000-µm diameter and 5- to 12-µm wall thickness. The fringe locations have been modeled by use of ray tracing and agree well with actual measurements of well-characterized shells. Details of the formation of the SIP fringes, a theoretical model, and the method used for quantitative measurement of the shell-wall thickness with the SIP are presented with validation examples.

© 1999 Optical Society of America

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References

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  1. G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
    [CrossRef]
  2. T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
    [CrossRef]
  3. R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
    [CrossRef]
  4. M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
    [CrossRef]
  5. Green Monochromatic Lamp, Edmund Scientific Company, 101 East Gloucester Pike, Barrington, N.J. 08007-1380.
  6. R. P. Cargille Laboratories, Inc., Cargille Scientific, Inc., 55 Commerce Road, Cedar Grove, N.J. 07009.

1997 (1)

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

1992 (1)

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

1990 (1)

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

1977 (1)

G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
[CrossRef]

Boehly, T. R.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Bosch, R. A.

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Brown, D. L.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Busch, Gar. E.

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Craxton, R. S.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Estabrook, K. G.

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Gram, R. Q.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Halpern, G. M.

G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
[CrossRef]

Harte, J. A.

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Immesoete, C.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Keck, R. L.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Kelly, J. H.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Kessler, T. J.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Kim, H.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Knauer, J. P.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Kollin, J. S.

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Kong, H.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Kumpan, S. A.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Leiner, D. C.

G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
[CrossRef]

Letzring, S. A.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Loucks, S. J.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Marshall, F. J.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

McCrory, R. L.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Moore, D. T.

G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
[CrossRef]

Morse, S. F. B.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Pien, G.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Prasad, M. K.

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Sampat, N.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Seka, W.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Soures, J. M.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Swales, S.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Varon, J.

G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
[CrossRef]

Verdon, C. P.

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Wittman, M. D.

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

J. Appl. Phys. (1)

G. M. Halpern, J. Varon, D. C. Leiner, D. T. Moore, “Laser fusion microballoon wall-thickness measurements: a comparative study,” J. Appl. Phys. 48, 1223–1228 (1977).
[CrossRef]

J. Vac. Sci. Technol. A (1)

R. Q. Gram, M. D. Wittman, C. Immesoete, H. Kim, R. S. Craxton, N. Sampat, S. Swales, G. Pien, J. M. Soures, H. Kong, “Uniform liquid-fuel layer produced in a cryogenic inertial fusion target by a time-dependent thermal gradient,” J. Vac. Sci. Technol. A 8, 3319–3323 (1990).
[CrossRef]

Opt. Commun. (1)

T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, C. P. Verdon, “Initial performance results of the OMEGA laser system,” Opt. Commun. 133, 495–506 (1997).
[CrossRef]

Phys. Fluids B (1)

M. K. Prasad, K. G. Estabrook, J. A. Harte, R. S. Craxton, R. A. Bosch, Gar. E. Busch, J. S. Kollin, “Holographic interferograms from laser fusion code simulations,” Phys. Fluids B 4, 1569–1575 (1992).
[CrossRef]

Other (2)

Green Monochromatic Lamp, Edmund Scientific Company, 101 East Gloucester Pike, Barrington, N.J. 08007-1380.

R. P. Cargille Laboratories, Inc., Cargille Scientific, Inc., 55 Commerce Road, Cedar Grove, N.J. 07009.

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Figures (8)

Fig. 1
Fig. 1

Compound-microscope image of a SIP produced by a symmetric target when the target is illuminated with narrow-bandwidth light. The CH capsule has an 850-µm diameter and a 7-µm thickness.

Fig. 2
Fig. 2

Ray paths through the target of (a) beam 1, (b) beam 2, and (c) beam 3. In each case the rays enter from the left, the emerging wave front is drawn on the right, and the emerging rays are backprojected (dashed lines) to their apparent origin in the object plane (z = 0). For a perfect target, wave fronts 2 and 3 are virtually identical, add coherently, and form the SIP through combination with wave front 1.

Fig. 3
Fig. 3

Optical path difference (OPD2 - OPD1) between beams 2 and 1 for a representative CH target with an 850-µm outer diameter, a 5-µm thickness, and a refractive index at 546 nm of 1.59. The abscissa is the apparent radius r a in the object plane (Fig. 2), which is almost identical to the incident radius r i . The filled circles correspond to integer values of optical path difference and thus give the radii of the centers of the bright fringes.

Fig. 4
Fig. 4

Universal curves governing the formation of the SIP. With plotting the OPD divided by the shell thickness t on the vertical axis and the normalized radius (r i /R shell) on the horizontal axis, the three quantities OPD1/t, OPD2/t, and (OPD2 - OPD1)/t are virtually independent of shell diameter and thickness. The curves shown here are for four shells with outer diameters ranging from 250 to 1500 µm and thicknesses ranging from 2 to 20 µm. The dashed curves correspond to a 250-µm diameter and a 20-µm thickness.

Fig. 5
Fig. 5

Calculated SIP’s for three perfectly symmetric CH targets, all with an outer diameter of 850 µm, but with thicknesses t ranging from 5 to 9 µm. The outer circles indicate the edge of the target, and the other circles are interference fringes. The SIP for t = 5 µm corresponds to Fig. 3 and that for t = 7 µm corresponds to Fig. 1. The target thickness in micrometers can be estimated by multiplication of the number of bright fringes by 0.88.

Fig. 6
Fig. 6

Calculated SIP’s for three CH targets with slightly different wall thicknesses. Thickness differences as small as 0.05 µm can be detected if attention is paid to the location of the inner fringes.

Fig. 7
Fig. 7

Calculated SIP’s formed by interference between beams 1 and 2 (light lines) and between beams 1 and 3 (heavy lines) for a CH target with a 1% thickness nonuniformity for three different orientations of the nonuniformity given by the unit vectors Δ. (The inner surface is spherical but shifted 0.05 µm in the direction of Δ.) (a) Two SIP’s are out of phase by a half-wave in the center, so no distinct interference pattern would be seen in practice; thus the existence of a distinct SIP indicates a target with better than 0.05-µm thickness uniformity.

Fig. 8
Fig. 8

Example of an interference pattern formed from a poor-quality shell. Two SIP’s are produced, as in Fig. 7, but they are not concentric.

Tables (1)

Tables Icon

Table 1 Comparison Between the Calculated and the Measured SIP Fringe Diameters for a Glass (n = 1.4648 ± 0.0003) Shella

Equations (13)

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OPD1=2tn-1,
OPD2=OPD3=4tn-2t,
OPD2 - OPD1=2tn.
tNλ/0.62=0.88N μm.
OPD2 - OPD3=OPD2 - OPD1 - OPD3 - OPD1=2tLn-2tRn=0.5λ,
tL-tR=0.086 μm,
A1=A0T12T22,  A2=A0T12T22R2,  A3=A0T12T22R2.
A2+A3=2A0T12T22R2.
A1±A2+A3=A0T12T221±2R2,
VImax-IminImax+Imin=1+2R22-1-2R221+2R22+1-2R22
=4R21+4R4,
A1±A2=A0T12T221±R2
V=2R21+R4.

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