Dynamics of converging laser-created plasmas in semicylindrical cavities studied using soft x-ray laser interferometry

Purvis, Michael; Grava, Jonathan; Filevich, Jorge; Marconi, M. C.; Dunn, James P.; Moon, Stephen J.; Shlyaptsev, Vyacheslav N.; Jankowska, E.; Rocca, J. J.

doi:10.1103/physreve.76.046402

Cited by 23 publications

(16 citation statements)

References 22 publications

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“…(2 ). Under these assumptions, the fringes will always bend in one direction when a plasma is probed, but from the anomalous results observed in many interferometer experiments [10][11][12][13][14][15] over the last four years it is clear that the traditional…”

Section: Analysis Of Interferometer Experimentsmentioning

confidence: 99%

“…Over the last four years interferometer experiments [10][11][12][13][14][15] of Al, Sn, Ag, and C plasmas have observed fringe lines bend in the opposite direction than was expected, indicating that the index of refraction was greater than one in parts of the plasma. Analysis of these experiments showed that the anomalous dispersion from the resonance lines and absorption edges of the bound electrons have a larger contribution to the index of refraction with the opposite sign as the free electrons [10][11][12][13][14][16][17][18] and their influence on the index of refraction extends far from the absorption edges and resonance lines.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the anomalous dispersion of doubly ionized carbon plasmas near 47nm

Nilsen

Castor

Iglesias

et al. 2008

High Energy Density Physics

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Over the last several years we have predicted and observed plasmas with an index of refraction greater than one in the soft X-ray regime. These plasmas are usually a few times ionized and have ranged from low-Z carbon plasmas to mid-Z tin plasmas. Our main calculational tool has been the average atom code. We have recently observed C 2+ plasmas with an index of refraction greater than one at a wavelength of 46.9 nm (26.44 eV). In this paper we compare the average atom method, AVATOMKG, against two more detailed methods, OPAL and CAK, for calculating the index of refraction for the carbon plasmas and discuss the different approximations used. We present experimental measurements of carbon plasmas that display this anomalous dispersion phenomenon. It is shown that the average atom calculation is a good approximation when the strongest lines dominate the dispersion. However, when weaker lines make a significant contribution, the more detailed calculations such as OPAL and CAK are essential. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential. With the advent of tunable X-ray lasers the frequency dependent interferometer measurements of the index of refraction may enable us to determine the absorption coefficients and line-shapes and make detailed comparisons against our atomic physics codes.

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Section: Analysis Of Interferometer Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Understanding the anomalous dispersion of doubly ionized carbon plasmas near 47nm

Nilsen

Castor

Iglesias

et al. 2008

High Energy Density Physics

Self Cite

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“…In contrast spectroscopic investigations of colliding laser plasma plumes have concentrated on short wavelength studies i.e. vacuum ultraviolet (VUV) 15 , extreme ultraviolet (EUV) and xray spectral ranges [16][17][18][19][20][21][22][23][24][25][26] . Attempts have also been made to simulate colliding laser plasma plumes for comparison with experimental results 21,[26][27][28] .…”

Section: Introductionmentioning

confidence: 99%

Charge resolved electrostatic diagnostic of colliding copper laser plasma plumes

Yeates¹,

Fallon²,

Kennedy³

et al. 2011

Physics of Plasmas

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“…This is based on collisional excitation pumping through a fast heating of the plasma. Such a soft X-ray laser has several applications in different areas of science and technology [16][17][18][19][20][21][22]. In fact, there exists a strong interest in extending the lasing wavelength toward shorter side.…”

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Effect of the rate of rise in discharge current on the output of a 46.9-nm soft X-ray laser based on capillary discharge

et al. 2016

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fast capillary discharge scheme, which has been demonstrated by several groups worldwide [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This is based on collisional excitation pumping through a fast heating of the plasma. Such a soft X-ray laser has several applications in different areas of science and technology [16][17][18][19][20][21][22]. In fact, there exists a strong interest in extending the lasing wavelength toward shorter side. It is worth mentioning here that directed EUV emission has also been reported from discharge plasma at shorter wavelengths ranging from 12 to 16 nm [23]. Efforts are presently going on in this direction in various laboratories worldwide to demonstrate X-ray lasing at a wavelength of 13.4 nm in nitrogen z-pinch plasma using a capillary discharge system [24][25][26][27]. Unlike the 46.9-nm X-ray laser, this is based on recombination pumping scheme which requires fast heating of the plasma followed by fast cooling of the hot plasma. Whether it is collisional excitation pumping scheme or recombination pumping scheme, both require faster pumping of the plasma to achieve population inversion, which can be done using a fast current pulse having high rate of rise (dI/dt) to excite the plasma.The generation of X-ray laser through the fast capillary discharge scheme is based on passing a fast rising electrical current through a pre-ionized gas column in a ceramic capillary. The magnetic field generated by the discharge current exerts strong magnetic force acting radially inwards on the plasma column. As a result, the plasma column gets pinched to a highly ionized hot and dense column, which may have sufficient population of required ionization state for lasing under suitable conditions. With argon gas filled inside the capillary, Ar 8+ ions are the lasing species and collectively form the gain medium for X-ray laser at 46.9 nm. Collisional electron excitation of these ions creates population inversion between 3p 1 S 0 and 3s 1 P 1 energy levels, which leads to soft X-ray lasing at 46.9 nm Abstract The rate of rise in discharge current (dI/dt) is an important parameter in an X-ray laser pumped by fast capillary discharge. The effect of this parameter on the energy of an argon plasma-based 46.9-nm soft X-ray laser pulse has been experimentally studied. It was found that an X-ray laser pulse with ~2 μJ energy, which can be obtained at a discharge current of ~40 kA with dI/dt value of ~7.1 × 10 11 A/s, can also be obtained at a much lower peak current of ~26 kA if the quarter period (T/4) of the discharge current is made shorter to achieve a comparable dI/dt value. For a fixed T/4, the laser energy could be enhanced from 2 to 4 μJ for an increase in the dI/dt value from 7.1 × 10 11 to 1.3 × 10 12 A/s by increasing the peak current from 26 to 44 kA. It was also observed that for a fixed dI/dt, mere increase in the discharge current does not increase the laser energy.

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Dynamics of converging laser-created plasmas in semicylindrical cavities studied using soft x-ray laser interferometry

Cited by 23 publications

References 22 publications

Understanding the anomalous dispersion of doubly ionized carbon plasmas near 47nm

Understanding the anomalous dispersion of doubly ionized carbon plasmas near 47nm

Charge resolved electrostatic diagnostic of colliding copper laser plasma plumes

Effect of the rate of rise in discharge current on the output of a 46.9-nm soft X-ray laser based on capillary discharge

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