Abstract

The development of a new time-resolved x-ray spectrometer is reported in which a free-standing x-ray transmission grating is coupled to a soft x-ray streak camera. The instrument measures continuous x-ray spectra with 20-psec temporal resolution and moderate spectral resolution (Δλ ≥ 1 Å) over a broad spectral range (0.1–5 keV) with high sensitivity and large information recording capacity. Its capabilities are well suited to investigation of laser-generated plasmas, and they nicely complement the characteristics of other time-resolved spectroscopic techniques presently in use. The transmission grating spectrometer has been used on a variety of laser-plasma experiments. We report the first measurements of the temporal variation of continuous low-energy x-ray spectra from laser-irradiated disk targets.

© 1983 Optical Society of America

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  1. V. W. Slivinsky, in Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 6; K. G. Tirsell, H. N. Kornblum, V. W. Slivinsky, LLNL report UCRL-81478 (1979), (unpublished).
  2. R. L. Kauffman, G. L. Stradling, E. L. Pierce, H. Medecki, Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 66; R. L. Kauffman, G. L. Stradling, D. T. Attwood, LLNL report UCRL-81373 (1978), unpublished.
  3. G. L. Stradling et al., in Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 292.
  4. M. H. Key et al., Phys. Rev. Lett. 44, 1667 (1980).
    [CrossRef]
  5. A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).
  6. N. M. Ceglio, A. M. Hawryluk, R. H. Price, Proc. Soc. Photo-opt. Instrum. Eng. 316High Resolution Soft X-ray Optics, (1981); Appl. Opt. 21, 3953 (1982).
    [PubMed]
  7. Equation (2) is accurate in practical laboratory applications in which the angle of incidence (relative to the grating normal) and the diffraction angle are both small. If these angles are not small, a more appropriate dispersion relation is mλ = d(sinθ0 + sinα), where θ0 and α are the diffraction and incidence angles both measured relative to the grating normal.
  8. X-ray streak camera technology was developed and has been used at LLNL since 1974; C. F. McConagny, L. W. Coleman, Appl. Phys. Lett. 25, 268 (1974); D. T. Attwood et al., Phys. Rev. Lett. 37, 499 (1976); Phys. Rev. Lett. 38, 282 (1977).
    [CrossRef]
  9. I. P. Csorba, RCA Rev. 32, 650 (1971); E. K. Zavoiskii, S. D. Fanchenko, Sov. Phys. Dokl. 1, 285 (1956).
  10. G. L. Stradling et al., Bull. Am. Phys. Soc. 23, 880 (1978); G. L. Stradling, M. S. Thesis, LLNL report UCRL-52568 (unpublished); G. L. Stradling, Ph.D. Thesis, U.C. Davis (1982).
  11. For laser-generated plasmas, viewed over the broad spectral range of this instrument, the size of the emitting region may be wavelength dependent. For example, the region of low-energy emission may be much larger than the region of high-energy emission. In such cases Δλ, which is source-size limited [Eq. (1)], will be wavelength dependent. This must be accounted for in Eq. (7) and the subsequent unfold procedures.
  12. Among the various contributions to the streak camera response function, that of greatest concern is the photocathode response in the spectral region of ~100 eV. We have used the results of B. L. Henke, J. P. Knauer, K. Premaratne, J. Appl. Phys. 52, 1509 (1981) but are concerned about cathode aging effects as reported by R. H. Day, P. Lee, E. B. Saloman, D. J. Nagel, J. Appl. Phys. 52, 6965 (1981). Such aging effects warrant further study and may bring into question the shape of the unfolded spectra of ~100–200 eV.
    [CrossRef]
  13. P. L. Hagelstein, Ph.D. Thesis, LLNL report UCRL-53100 (1981) (unpublished).
  14. The prompt response of higher-energy x-ray emissions observed here is consistent with earlier multichannel streak camera measurements of laser-irradiated disk targets: G. L. Stradling, R. L. Kauffman, LLNL report UCRL-50021-78 (1978), p. 6-2 (unpublished).
  15. The high-frequency structure on these plots may be attributed to noise, not physically meaningful spectroscopic processes within the plasma. The scale length of this structure is well below the spectral resolution of the instrument.
  16. In both the A-series and S-series experiments the measured width of the zeroth-order component is a summation over the contributions from the entire source spectrum (from the UV to high-energy x rays), not limited by the spectral range of the first-order diffraction. In this regard the measured zeroth-order width may be an overestimate of the spectral resolution Δλ at a particular wavelength (see Ref. 11). However, to the extent that the x-ray line emission dominates the zeroth-order component in the S-series experiments, the measured zeroth-order width may be a good estimate of the spectral resolution at those x-ray energies.
  17. Although the spectral range for first-order diffracted radiation is 2–30 Å in these experiments, the contributions to the zeroth order extend to much longer wavelengths (see Ref. 16).

1981 (3)

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

N. M. Ceglio, A. M. Hawryluk, R. H. Price, Proc. Soc. Photo-opt. Instrum. Eng. 316High Resolution Soft X-ray Optics, (1981); Appl. Opt. 21, 3953 (1982).
[PubMed]

Among the various contributions to the streak camera response function, that of greatest concern is the photocathode response in the spectral region of ~100 eV. We have used the results of B. L. Henke, J. P. Knauer, K. Premaratne, J. Appl. Phys. 52, 1509 (1981) but are concerned about cathode aging effects as reported by R. H. Day, P. Lee, E. B. Saloman, D. J. Nagel, J. Appl. Phys. 52, 6965 (1981). Such aging effects warrant further study and may bring into question the shape of the unfolded spectra of ~100–200 eV.
[CrossRef]

1980 (1)

M. H. Key et al., Phys. Rev. Lett. 44, 1667 (1980).
[CrossRef]

1978 (1)

G. L. Stradling et al., Bull. Am. Phys. Soc. 23, 880 (1978); G. L. Stradling, M. S. Thesis, LLNL report UCRL-52568 (unpublished); G. L. Stradling, Ph.D. Thesis, U.C. Davis (1982).

1974 (1)

X-ray streak camera technology was developed and has been used at LLNL since 1974; C. F. McConagny, L. W. Coleman, Appl. Phys. Lett. 25, 268 (1974); D. T. Attwood et al., Phys. Rev. Lett. 37, 499 (1976); Phys. Rev. Lett. 38, 282 (1977).
[CrossRef]

1971 (1)

I. P. Csorba, RCA Rev. 32, 650 (1971); E. K. Zavoiskii, S. D. Fanchenko, Sov. Phys. Dokl. 1, 285 (1956).

Ceglio, N. M.

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

N. M. Ceglio, A. M. Hawryluk, R. H. Price, Proc. Soc. Photo-opt. Instrum. Eng. 316High Resolution Soft X-ray Optics, (1981); Appl. Opt. 21, 3953 (1982).
[PubMed]

Coleman, L. W.

X-ray streak camera technology was developed and has been used at LLNL since 1974; C. F. McConagny, L. W. Coleman, Appl. Phys. Lett. 25, 268 (1974); D. T. Attwood et al., Phys. Rev. Lett. 37, 499 (1976); Phys. Rev. Lett. 38, 282 (1977).
[CrossRef]

Csorba, I. P.

I. P. Csorba, RCA Rev. 32, 650 (1971); E. K. Zavoiskii, S. D. Fanchenko, Sov. Phys. Dokl. 1, 285 (1956).

Hagelstein, P. L.

P. L. Hagelstein, Ph.D. Thesis, LLNL report UCRL-53100 (1981) (unpublished).

Hawryluk, A. M.

N. M. Ceglio, A. M. Hawryluk, R. H. Price, Proc. Soc. Photo-opt. Instrum. Eng. 316High Resolution Soft X-ray Optics, (1981); Appl. Opt. 21, 3953 (1982).
[PubMed]

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

Henke, B. L.

Among the various contributions to the streak camera response function, that of greatest concern is the photocathode response in the spectral region of ~100 eV. We have used the results of B. L. Henke, J. P. Knauer, K. Premaratne, J. Appl. Phys. 52, 1509 (1981) but are concerned about cathode aging effects as reported by R. H. Day, P. Lee, E. B. Saloman, D. J. Nagel, J. Appl. Phys. 52, 6965 (1981). Such aging effects warrant further study and may bring into question the shape of the unfolded spectra of ~100–200 eV.
[CrossRef]

Kauffman, R. L.

The prompt response of higher-energy x-ray emissions observed here is consistent with earlier multichannel streak camera measurements of laser-irradiated disk targets: G. L. Stradling, R. L. Kauffman, LLNL report UCRL-50021-78 (1978), p. 6-2 (unpublished).

R. L. Kauffman, G. L. Stradling, E. L. Pierce, H. Medecki, Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 66; R. L. Kauffman, G. L. Stradling, D. T. Attwood, LLNL report UCRL-81373 (1978), unpublished.

Key, M. H.

M. H. Key et al., Phys. Rev. Lett. 44, 1667 (1980).
[CrossRef]

Knauer, J. P.

Among the various contributions to the streak camera response function, that of greatest concern is the photocathode response in the spectral region of ~100 eV. We have used the results of B. L. Henke, J. P. Knauer, K. Premaratne, J. Appl. Phys. 52, 1509 (1981) but are concerned about cathode aging effects as reported by R. H. Day, P. Lee, E. B. Saloman, D. J. Nagel, J. Appl. Phys. 52, 6965 (1981). Such aging effects warrant further study and may bring into question the shape of the unfolded spectra of ~100–200 eV.
[CrossRef]

McConagny, C. F.

X-ray streak camera technology was developed and has been used at LLNL since 1974; C. F. McConagny, L. W. Coleman, Appl. Phys. Lett. 25, 268 (1974); D. T. Attwood et al., Phys. Rev. Lett. 37, 499 (1976); Phys. Rev. Lett. 38, 282 (1977).
[CrossRef]

Medecki, H.

R. L. Kauffman, G. L. Stradling, E. L. Pierce, H. Medecki, Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 66; R. L. Kauffman, G. L. Stradling, D. T. Attwood, LLNL report UCRL-81373 (1978), unpublished.

Melngailis, J.

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

Pierce, E. L.

R. L. Kauffman, G. L. Stradling, E. L. Pierce, H. Medecki, Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 66; R. L. Kauffman, G. L. Stradling, D. T. Attwood, LLNL report UCRL-81373 (1978), unpublished.

Premaratne, K.

Among the various contributions to the streak camera response function, that of greatest concern is the photocathode response in the spectral region of ~100 eV. We have used the results of B. L. Henke, J. P. Knauer, K. Premaratne, J. Appl. Phys. 52, 1509 (1981) but are concerned about cathode aging effects as reported by R. H. Day, P. Lee, E. B. Saloman, D. J. Nagel, J. Appl. Phys. 52, 6965 (1981). Such aging effects warrant further study and may bring into question the shape of the unfolded spectra of ~100–200 eV.
[CrossRef]

Price, R. H.

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

N. M. Ceglio, A. M. Hawryluk, R. H. Price, Proc. Soc. Photo-opt. Instrum. Eng. 316High Resolution Soft X-ray Optics, (1981); Appl. Opt. 21, 3953 (1982).
[PubMed]

Slivinsky, V. W.

V. W. Slivinsky, in Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 6; K. G. Tirsell, H. N. Kornblum, V. W. Slivinsky, LLNL report UCRL-81478 (1979), (unpublished).

Smith, H. I.

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

Stradling, G. L.

G. L. Stradling et al., Bull. Am. Phys. Soc. 23, 880 (1978); G. L. Stradling, M. S. Thesis, LLNL report UCRL-52568 (unpublished); G. L. Stradling, Ph.D. Thesis, U.C. Davis (1982).

R. L. Kauffman, G. L. Stradling, E. L. Pierce, H. Medecki, Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 66; R. L. Kauffman, G. L. Stradling, D. T. Attwood, LLNL report UCRL-81373 (1978), unpublished.

The prompt response of higher-energy x-ray emissions observed here is consistent with earlier multichannel streak camera measurements of laser-irradiated disk targets: G. L. Stradling, R. L. Kauffman, LLNL report UCRL-50021-78 (1978), p. 6-2 (unpublished).

G. L. Stradling et al., in Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 292.

Appl. Phys. Lett. (1)

X-ray streak camera technology was developed and has been used at LLNL since 1974; C. F. McConagny, L. W. Coleman, Appl. Phys. Lett. 25, 268 (1974); D. T. Attwood et al., Phys. Rev. Lett. 37, 499 (1976); Phys. Rev. Lett. 38, 282 (1977).
[CrossRef]

Bull. Am. Phys. Soc. (1)

G. L. Stradling et al., Bull. Am. Phys. Soc. 23, 880 (1978); G. L. Stradling, M. S. Thesis, LLNL report UCRL-52568 (unpublished); G. L. Stradling, Ph.D. Thesis, U.C. Davis (1982).

High Resolution Soft X-ray Optics (1)

N. M. Ceglio, A. M. Hawryluk, R. H. Price, Proc. Soc. Photo-opt. Instrum. Eng. 316High Resolution Soft X-ray Optics, (1981); Appl. Opt. 21, 3953 (1982).
[PubMed]

J. Appl. Phys. (1)

Among the various contributions to the streak camera response function, that of greatest concern is the photocathode response in the spectral region of ~100 eV. We have used the results of B. L. Henke, J. P. Knauer, K. Premaratne, J. Appl. Phys. 52, 1509 (1981) but are concerned about cathode aging effects as reported by R. H. Day, P. Lee, E. B. Saloman, D. J. Nagel, J. Appl. Phys. 52, 6965 (1981). Such aging effects warrant further study and may bring into question the shape of the unfolded spectra of ~100–200 eV.
[CrossRef]

J. Vac. Sci. Technol. (1)

A. M. Hawryluk, N. M. Ceglio, R. H. Price, J. Melngailis, H. I. Smith, J. Vac. Sci. Technol. (Nov.–Dec, 1981); A. M. Hawryluk, Ph.D. Thesis, MIT (1981).

Phys. Rev. Lett. (1)

M. H. Key et al., Phys. Rev. Lett. 44, 1667 (1980).
[CrossRef]

RCA Rev. (1)

I. P. Csorba, RCA Rev. 32, 650 (1971); E. K. Zavoiskii, S. D. Fanchenko, Sov. Phys. Dokl. 1, 285 (1956).

Other (10)

Equation (2) is accurate in practical laboratory applications in which the angle of incidence (relative to the grating normal) and the diffraction angle are both small. If these angles are not small, a more appropriate dispersion relation is mλ = d(sinθ0 + sinα), where θ0 and α are the diffraction and incidence angles both measured relative to the grating normal.

V. W. Slivinsky, in Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 6; K. G. Tirsell, H. N. Kornblum, V. W. Slivinsky, LLNL report UCRL-81478 (1979), (unpublished).

R. L. Kauffman, G. L. Stradling, E. L. Pierce, H. Medecki, Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 66; R. L. Kauffman, G. L. Stradling, D. T. Attwood, LLNL report UCRL-81373 (1978), unpublished.

G. L. Stradling et al., in Low Energy X-ray Diagnostics, D. T. Attwood, B. L. Henke, Eds. (AIP, New York, 1981), p. 292.

P. L. Hagelstein, Ph.D. Thesis, LLNL report UCRL-53100 (1981) (unpublished).

The prompt response of higher-energy x-ray emissions observed here is consistent with earlier multichannel streak camera measurements of laser-irradiated disk targets: G. L. Stradling, R. L. Kauffman, LLNL report UCRL-50021-78 (1978), p. 6-2 (unpublished).

The high-frequency structure on these plots may be attributed to noise, not physically meaningful spectroscopic processes within the plasma. The scale length of this structure is well below the spectral resolution of the instrument.

In both the A-series and S-series experiments the measured width of the zeroth-order component is a summation over the contributions from the entire source spectrum (from the UV to high-energy x rays), not limited by the spectral range of the first-order diffraction. In this regard the measured zeroth-order width may be an overestimate of the spectral resolution Δλ at a particular wavelength (see Ref. 11). However, to the extent that the x-ray line emission dominates the zeroth-order component in the S-series experiments, the measured zeroth-order width may be a good estimate of the spectral resolution at those x-ray energies.

Although the spectral range for first-order diffracted radiation is 2–30 Å in these experiments, the contributions to the zeroth order extend to much longer wavelengths (see Ref. 16).

For laser-generated plasmas, viewed over the broad spectral range of this instrument, the size of the emitting region may be wavelength dependent. For example, the region of low-energy emission may be much larger than the region of high-energy emission. In such cases Δλ, which is source-size limited [Eq. (1)], will be wavelength dependent. This must be accounted for in Eq. (7) and the subsequent unfold procedures.

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Figures (10)

Fig. 1
Fig. 1

Time-resolved x-ray spectrometer schematically represented viewing a laser-irradiated gold target. A free-standing x-ray transmission grating is coupled with a soft x-ray streak camera to provide time-resolved continuous x-ray spectra over a broad spectral range.

Fig. 2
Fig. 2

SEM micrographs of a free-standing gold transmission grating. The 3000-Å period gold bars (shown vertically on the left) are supported by a 6-μm period gold grid structure (shown vertically on the right).

Fig. 3
Fig. 3

Broad spectral range of the x-ray transmission grating using time-integrated x-ray spectra from laser-irradiated gold and titanium disk targets. The spectra were dispersed by a free-standing transmission grating and recorded on film. Note the heliumlike Ti K lines at 4.7 keV and the Ck absorption edge at 0.28 keV.

Fig. 4
Fig. 4

(a) Streak camera response function used to unfold the recorded x-ray spectra plotted vs x-ray energy (see Ref. 12). (b) Transmission grating diffraction efficiencies (calculated) for zeroth through third order are plotted for the diffraction grating used (t ≃ 0.5-μm gold; γ ≃ 1.22) (courtesy M. Schattenburg, MIT).

Fig. 5
Fig. 5

Complete data set for a gold disk target illuminated at 3 × 1014 W/cm2 with λ = 0.53-μm laser light. (a) The direct photographic record of x-ray wavelength vs time. (b) The time histories of emission of the total undiffracted radiation as well as spectral bands centered at 150 and 500 eV are compared. (c) Raw spectral data (intensity vs wavelength) at three different times. (d) Unfolded x-ray source spectra (units of keV/keV-psec-sr) at two different times plotted vs x-ray energy.

Fig. 6
Fig. 6

Gold disk target data at two different illumination intensities, 3 × 1013 and 3 × 1014 W/cm2, are compared. (a) Comparison of unfolded x-ray spectra at the peak of the pulse; (b) comparison of the temporal shape of the continuum emission at 150 eV.

Fig. 7
Fig. 7

Comparison of unfolded source spectra for a gold and a titanium disk target illuminated under identical conditions at 3 × 1014 W/cm2.

Fig. 8
Fig. 8

Direct photographic data records (wavelength vs time) for short-pulse (≃ 120-psec) illuminated thin metallic disk targets. (a) 350-Å Cr layer on CH illuminated at ≃2 × 1014 W/cm2; (b) 400-Å Ni layer on CH illuminated at 3 × 1014 W/cm2.

Fig. 9
Fig. 9

Comparison of the unfolded x-ray spectra from the chromium and nickel disk targets. Spectral resolution limitations preclude identification of the multiple lines contributing to the measured characteristic bands.

Fig. 10
Fig. 10

Comparison of the temporal duration of the characteristic band emission and the total undiffracted emission for the thin metal disk targets: (a) Cr layer on CH; (b) Ni layer on CH.

Tables (1)

Tables Icon

Table I Comparative Characteristics of Time-Resolved Instruments for the Spectroscopic Investigation of Laser-Generated Plasmas

Equations (12)

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Δ λ = d ( S + A ) L + d A D ,
sin θ = ( m λ ) / d m = 0,1 , ,
d y / d λ = ( m D ) / d ,
λ max = ( d / D ) Y ,
λ min = { d D δ ( spatial resolution limited ) , Δ λ ( spectral resolution limited ) ,
Δ λ R = λ max λ min .
I ( y 0 ) = Δ λ λ 0 1 ( D + L ) 2 m = 1,2 , , S ( m 0 ) η m ( m 0 ) α ( m 0 ) ,
η m = [ sin ( m π γ + 1 ) m π ] 2 ( 1 2 b cos Φ + b 2 ) ,
Γ a ( y 0 ) = I a ( y 0 ) I ( y 0 ) .
S b ( 0 ) = S a ( 0 ) Γ a ( y 0 ) ( D + L ) 2 α ( 0 ) η 1 ( 0 ) ( λ 0 Δ λ ) .
A = 100 μ m , Δ λ 2 4 Å ( measured ) , 11 L = 76.6 cm , d = 3000 Å , λ max 120 Å , D = 31 cm , d y / d λ 0.10 mm / Å , λ min 4 Å .
A = 100 μ m , Δ λ 1 1.5 Å ( measured ) , 11 L = 112 cm , d = 3000 Å , λ max 30 Å , D = 118 cm , d y / d λ 0.39 mm / Å , λ min 2 Å .

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