Abstract

Scintillator-based “optical” soft x-ray (OSXR) arrays have been investigated as a replacement for the conventional silicon (Si)-based diode arrays used for imaging, tomographic reconstruction, magnetohydrodynamics, transport, and turbulence studies in magnetically confined fusion plasma research. An experimental survey among several scintillator candidates was performed, measuring the relative and absolute conversion efficiencies of soft x rays to visible light. Further investigations took into account glass and fiber-optic faceplates (FOPs) as substrates, and a thin aluminum foil (150  nm) to reflect the visible light emitted by the scintillator back to the optical detector. Columnar (crystal growth) thallium-doped cesium iodide (CsI:Tl) deposited on an FOP, was found to be the best candidate for the previously mentioned plasma diagnostics. Its luminescence decay time of the order of 110  μs is thus suitable for the 10 μs time resolution required for the development of scintillator-based SXR plasma diagnostics. A prototype eight channel OSXR array using CsI:Tl was designed, built, and compared to an absolute extreme ultraviolet diode counterpart: its operation on the National Spherical Torus Experiment showed a lower level of induced noise relative to the Si-based diode arrays, especially during neutral beam injection heated plasma discharges. The OSXR concept can also be implemented in less harsh environments for basic spectroscopic laboratory plasma diagnostics.

© 2007 Optical Society of America

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References

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2005

C. Brecher, V. V. Nagarkar, V. Gaysinskiy, S. R. Miller, and A. Lempicki, Nucl. Instrum. Methods Phys. Res. A 537, 117-124 (2005).
[CrossRef]

2004

L. F. Delgado-Aparicio, D. Stutman, K. Tritz, M. Finkenthal, R. Kaita, L. Roquemore, D. Johnson, and R. Majeski, "'Optical' soft x-ray arrays for fluctuation diagnostics in magnetic fusion energy experiments," Rev. Sci. Instrum. 75, 4020-4022 (2004).
[CrossRef]

2003

V. A. Soukhanovskii, S. P. Regan, M. J. May, M. Finkenthal, and H. W. Moos, "Development of phosphor scintillator-based detectors for soft X-ray and VUV spectroscopy of magnetically confined fusion plasmas," Rev. Sci. Instrum. 74, 4331-4335 (2003).
[CrossRef]

V. Avdeichikov, R. Ghetti, P. Golubev, B. Jakobsson, and N. Colonna, "Energy calibration of CsI(Tl) scintillator in pulse-shape identification technique," Nucl. Instrum. Methods Phys. Res. A 501, 505-513 (2003).
[CrossRef]

2002

S. M. Gruner, M. W. Tate, and E. F. Eikenberry, "Charge-coupled device area x-ray detectors," Rev. Sci. Instrum. 73, 2815-2842 (2002).
[CrossRef]

1999

S. von Goeler, R. Kaita, M. Bitter, G. Fuchs, M. Poier, G. Bertschinger, H. R. Koslowski, K. Toi, S. Ohdachi, and A. Donne, "High speed tangential soft x-ray camera for the study of magnetohydrodynamics instabilities," Rev. Sci. Instrum. 70, 599-602 (1999).
[CrossRef]

1998

V. V. Nagarkar, S. Vasile, P. Gothoskar, J. S. Gordon, and T. K. Gupta, IEEE Trans. Nucl. Sci. 44, 492-496 (1998).
[CrossRef]

Y. Tanimura and T. Iida, "Effects of DD and DT neutron irradiation on some Si devices for fusion diagnostics," J. Nucl. Mater. 258-263, 1812-1816 (1998).
[CrossRef]

1997

D. Stutman, Y. S. Hwang, J. Menard, W. Choe, M. Ono, M. Finkenthal, M. J. May, S. P. Regan, V. Soukhanovskii, and H. W. Moos, "Multilayer mirror based line emission tomography for spherical Tokamaks," Rev. Sci. Instrum. 68, 1055-1058 (1997).
[CrossRef]

S. P. Regan, K. B. Fournier, M. J. May, V. Soukhanovskii, M. Finkenthal, and H. W. Moos, "How to beat the low resolution of multilayer mirror spectra," Rev. Sci. Instrum. 68, 1002-1008 (1997).
[CrossRef]

1996

F. Scholze, H. Rabus, and G. Ulm, "Measurement of the mean electron-hole pair creation energy in crystalline silicon for photons in the 50-1500 eV spectral range," Appl. Phys. Lett. 69, 2974-2976 (1996).
[CrossRef]

1995

K. W. Hill, H. Adler, M. Bitter, E. Fredrickson, S. von Goeler, H. Hsuan, A. Janos, D. Johnson, A. T. Ramsey, and G. Renda, "Analysis of nuclear-radiation-induced noise in spectroscopic and x-ray diagnostics during high power deuterium-tritium experiments on the tokamak fusion test reactor," Rev. Sci. Instrum. 66, 913-915 (1995).
[CrossRef]

1994

1992

1991

Z. Li, W. Chen, and H. W. Kraner, "Effects of fast neutron radiation on the electrical properties of silicon detectors," Nucl. Instrum. Methods Phys. Res. A 308, 585-595 (1991).
[CrossRef]

1986

B. X. Yang, J. Kirz, Y. H. Kao, and T. K. Sham, "Soft-X-ray spectroscopy with a scintillation detector," Nucl. Instrum. Methods Phys. Res. A 246, 523-526 (1986).
[CrossRef]

Appl. Opt.

Appl. Phys. Lett.

F. Scholze, H. Rabus, and G. Ulm, "Measurement of the mean electron-hole pair creation energy in crystalline silicon for photons in the 50-1500 eV spectral range," Appl. Phys. Lett. 69, 2974-2976 (1996).
[CrossRef]

IEEE Trans. Nucl. Sci.

V. V. Nagarkar, S. Vasile, P. Gothoskar, J. S. Gordon, and T. K. Gupta, IEEE Trans. Nucl. Sci. 44, 492-496 (1998).
[CrossRef]

J. Nucl. Mater.

Y. Tanimura and T. Iida, "Effects of DD and DT neutron irradiation on some Si devices for fusion diagnostics," J. Nucl. Mater. 258-263, 1812-1816 (1998).
[CrossRef]

J. Opt. Soc. Am. B

Nucl. Instrum. Methods Phys. Res. A

Z. Li, W. Chen, and H. W. Kraner, "Effects of fast neutron radiation on the electrical properties of silicon detectors," Nucl. Instrum. Methods Phys. Res. A 308, 585-595 (1991).
[CrossRef]

C. Brecher, V. V. Nagarkar, V. Gaysinskiy, S. R. Miller, and A. Lempicki, Nucl. Instrum. Methods Phys. Res. A 537, 117-124 (2005).
[CrossRef]

V. Avdeichikov, R. Ghetti, P. Golubev, B. Jakobsson, and N. Colonna, "Energy calibration of CsI(Tl) scintillator in pulse-shape identification technique," Nucl. Instrum. Methods Phys. Res. A 501, 505-513 (2003).
[CrossRef]

B. X. Yang, J. Kirz, Y. H. Kao, and T. K. Sham, "Soft-X-ray spectroscopy with a scintillation detector," Nucl. Instrum. Methods Phys. Res. A 246, 523-526 (1986).
[CrossRef]

Rev. Sci. Instrum.

L. F. Delgado-Aparicio, D. Stutman, K. Tritz, M. Finkenthal, R. Kaita, L. Roquemore, D. Johnson, and R. Majeski, "'Optical' soft x-ray arrays for fluctuation diagnostics in magnetic fusion energy experiments," Rev. Sci. Instrum. 75, 4020-4022 (2004).
[CrossRef]

V. A. Soukhanovskii, S. P. Regan, M. J. May, M. Finkenthal, and H. W. Moos, "Development of phosphor scintillator-based detectors for soft X-ray and VUV spectroscopy of magnetically confined fusion plasmas," Rev. Sci. Instrum. 74, 4331-4335 (2003).
[CrossRef]

S. von Goeler, R. Kaita, M. Bitter, G. Fuchs, M. Poier, G. Bertschinger, H. R. Koslowski, K. Toi, S. Ohdachi, and A. Donne, "High speed tangential soft x-ray camera for the study of magnetohydrodynamics instabilities," Rev. Sci. Instrum. 70, 599-602 (1999).
[CrossRef]

S. M. Gruner, M. W. Tate, and E. F. Eikenberry, "Charge-coupled device area x-ray detectors," Rev. Sci. Instrum. 73, 2815-2842 (2002).
[CrossRef]

K. W. Hill, H. Adler, M. Bitter, E. Fredrickson, S. von Goeler, H. Hsuan, A. Janos, D. Johnson, A. T. Ramsey, and G. Renda, "Analysis of nuclear-radiation-induced noise in spectroscopic and x-ray diagnostics during high power deuterium-tritium experiments on the tokamak fusion test reactor," Rev. Sci. Instrum. 66, 913-915 (1995).
[CrossRef]

D. Stutman, Y. S. Hwang, J. Menard, W. Choe, M. Ono, M. Finkenthal, M. J. May, S. P. Regan, V. Soukhanovskii, and H. W. Moos, "Multilayer mirror based line emission tomography for spherical Tokamaks," Rev. Sci. Instrum. 68, 1055-1058 (1997).
[CrossRef]

S. P. Regan, K. B. Fournier, M. J. May, V. Soukhanovskii, M. Finkenthal, and H. W. Moos, "How to beat the low resolution of multilayer mirror spectra," Rev. Sci. Instrum. 68, 1002-1008 (1997).
[CrossRef]

Other

See, for example, data sheets from manufacturers, such as www.rexon.com, www.bicron.com, www.appscintech.com, and www.rmdinc.com.

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Figures (9)

Fig. 1
Fig. 1

Experimental setup for the measurement of the relative conversion efficiencies.

Fig. 2
Fig. 2

Relative to P45 conversion efficiencies (CE) and reported [8] time response of the candidate scintillators (in parentheses).

Fig. 3
Fig. 3

Experimental setup for the measurement of the absolute conversion efficiencies.

Fig. 4
Fig. 4

(Color online) Absolute conversion efficiencies of (a) P45 versus P43 and (b) P45 versus amorphous CsI:Tl. The P45 average grain sizes are of the order of 4 and 6   μm with mass densities of 2 and 4   mg / cm 2 .

Fig. 5
Fig. 5

(Color online) Measured amorphous ( 5 mg / cm 2 on glass) CsI:Tl conversion efficiency at low SXR energies: 30 300   eV (NIST synchrotron).

Fig. 6
Fig. 6

(Color online) Absolute CE for CsI:Tl amorphous and columnar depositions on glass and FOPs.

Fig. 7
Fig. 7

(Color online) X-ray measurement of Sawtooth crash observed in CDX-U with diode and “optical” detectors.

Fig. 8
Fig. 8

Fast poloidally traveling ELM seen by the (a) OSXR and (b) diode arrays.

Fig. 9
Fig. 9

(Color online) (a) Time histories of plasma current ( I p ) and neutral beam injection (NBI). (b) to (d) and (e) to (g) are the raw signals and their high-frequency components before ( Δ t 1 ) and during ( Δ t 2 ) the plasma formation for both the diode and OSXR arrays, respectively.

Tables (1)

Tables Icon

Table 1 Candidate Scintillators and Their Known Characteristics a

Equations (79)

Equations on this page are rendered with MathJax. Learn more.

( 150   nm )
1 10   μs
( 0 .1 < E X < 10   keV )
( 200   kHz )
( 5 15   cm )
( E X > 10   keV )
( 20   μs )
2 6 mg / cm 2
5 30   μm
4 π
( Y 2 O 2 S : Tb )
K α
C - K α 277   eV
K α
14 × 10 10 photons / s
K α
2 %
5 mg / cm 2
CE = R Ω Q E X Q E vis ( I vis I X ) ,
Q E x ,vis
I x ,vis
( R Ω )
Q E X E X / 3.63
E X
( 3 7   nm )
S i O 2
[ Q E vis ( 2 , 2.75 , 3   eV ) 0.64 , 0.57 , 0.49 ]
[ ϕ g ( μm ) ]
[ D i ( mg / cm 2 ) ]
K α
C - K α
( 277   eV )
0.3   μm
( 20% 50% )
τ C s I : T l 1 10 μ s τ P 45 1 m s
30 400   eV
38   mm
k = 1
CE 277   eV
40 70 photons / keV
20 35 photons / keV
30   μm
20 35 p h o t o n s / k e V f o r 2 π s r
( 20 % )
0.15   μm
0.1   μm
30%
( τ CsI : Tl [ 0.6 , 10 ]   μs )
200   kHz
τ CsI : Tl
65   kHz
10 8 V / A
5   μs
E X 0.3   keV
2 3   μs
10 7 V / A
300   kHz
( Δ t )
50   μs
1 .0   keV
( 5   μs )
( 2 3   μs )
60   kHz
5   μs
( P N B 6   MW )
I p max 1.1   MA
( Δ t 1 )
( Δ t 2 )
Δ t 1
2.5   MeV
20 % 30 %
100   kHz
6   μm
4   mg / cm 2
5 mg / cm 2
30 300   eV
( I p )
( Δ t 1 )
( Δ t 2 )

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