Development and characterization of a low current capillary discharge for X-ray laser studies

Niimi, Gohta; Hayashi, Yasushi; Sakamoto, Nobuhiro; Nakajima, Mitsuo; Okino, Akitoshi; Watanabe, M.; Horioka, Kazuhiko; Hotta, Eiki

doi:10.1109/tps.2002.1024297

Cited by 49 publications

(30 citation statements)

References 16 publications

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“…The second end of the coil was either grounded, or connected to an external generator/power supply (protected by shortcutting spark gap) for active control of the pre-pulse current. To our knowledge this active control has been used by laboratories in Japan [16], [18] and in the beginning also in Italy [20]. Unfortunately, in our setup it turned out that the capacitance of the coil to the central electrode of the fast capacitor is so high, that even with the grounded second-coilend the pre-pulse current is >50A.…”

Section: Pre-pulse Generationmentioning

confidence: 96%

“…These attempts started to be successful only recently, when the role of pre-pulse had been at least partly understood [15]: with the help of onaxis X-ray imaging by quadro-pinhole camera and with the soft X-ray spectroscopy it was shown, that the pre-pulse current I p < 10 A is not sufficient for efficient pre-ionization, and that I p > 50 A is too high (probably it pre-heats plasma so much that efficient pinching is prevented). A more detail study of pre-pulse and its influence on the main discharge was based on side-on photographing of the pre-discharge and of the main discharge in Pyrex glass capillary by high-speed framing camera (exposition 10 ns) [16], [17], [18]. It was found that the pre-discharge with amplitude 15 A and an exponential decay ∼ 100μs was stable for first 40μs and then some striations started to develop [17].…”

Section: Introductionmentioning

confidence: 99%

“…In the main discharge without pre-discharge an onset of instability was observed at pinch time (20 ÷ 30 ns after the main current onset), and reproducibility of plasma was considerably poor. On the other hand, the main discharge initiated shortly after the pre-discharge current maximum (10 A) was pretty stable [16], [18]. Similarly, as soon as other laboratories introduced a suitable pre-pulse, either amplification [19], or the saturated amplification [20] was achieved.…”

Section: Introductionmentioning

confidence: 99%

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Role of pre-pulse in gas-filled-capillary soft X-ray source

et al. 2004

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The pre-pulse should ensure that the main current pulse starts (due to skin effect) in a thin cylindrical layer near the capillary wall. Then an axially symmetrical compression (due to pinch effect) takes place that compresses the plasma into a thin, dense, hot, straight plasma fibre, in which there are favourable conditions for amplification of spontaneous emission in soft X-ray region and for lasing. We describe both passive and active generation of the pre-pulse and its influence on the waveform of the capillary discharge current, pinching process, and axial soft X-ray radiation.

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Section: Pre-pulse Generationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Role of pre-pulse in gas-filled-capillary soft X-ray source

et al. 2004

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“…A population inversion between 2p 5 3p 1 S 0 and 2p 5 3s 1 P 1 (J = 0-1) in the Ne-like Ar ions was produced by the electron collisional excitation, and the gain coefficient at 46.9 nm (A line) was measured as 0.6 cm −1 . A saturated Ne-like Ar soft X-ray laser at 46.9 nm pumped by capillary discharge has produced millijoule-level laser pulses at a repetition rate of 4 Hz [2] and has led to many applications such as the diagnostics of dense plasma [3], lithography [4], nanoimaging [5], nanomachining [6] and material ablation [7].Other groups also had developed 46.9 nm laser pumped by capillary discharge [8][9][10][11][12][13][14][15][16]. Some groups studied the 46.9 nm laser with a low current, which is benefit to reduce the size and enhance the repetitive frequency of the laser.…”

mentioning

confidence: 99%

“…Other groups also had developed 46.9 nm laser pumped by capillary discharge [8][9][10][11][12][13][14][15][16]. Some groups studied the 46.9 nm laser with a low current, which is benefit to reduce the size and enhance the repetitive frequency of the laser.…”

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confidence: 99%

Characteristics of a multi-wavelength Ne-like Ar laser excited by capillary discharge

et al. 2016

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other applications. In 1994, J. J. Rocca et al. reported the first demonstration of large soft X-ray amplification in the plasma of a capillary discharge [1]. A population inversion between 2p 5 3p 1 S 0 and 2p 5 3s 1 P 1 (J = 0-1) in the Ne-like Ar ions was produced by the electron collisional excitation, and the gain coefficient at 46.9 nm (A line) was measured as 0.6 cm −1 . A saturated Ne-like Ar soft X-ray laser at 46.9 nm pumped by capillary discharge has produced millijoule-level laser pulses at a repetition rate of 4 Hz [2] and has led to many applications such as the diagnostics of dense plasma [3], lithography [4], nanoimaging [5], nanomachining [6] and material ablation [7].Other groups also had developed 46.9 nm laser pumped by capillary discharge [8][9][10][11][12][13][14][15][16]. Some groups studied the 46.9 nm laser with a low current, which is benefit to reduce the size and enhance the repetitive frequency of the laser. G. Niimi et al. firstly reported the observation of 46.9 nm laser output at a low discharge current of 9 kA [8]. G. Tomassetti et al. reported that 46.9 nm laser was realized with low amplitude 17-20 kA current pulses at pulse repetition rate up to 0.1 Hz [9]. The saturated laser at 46.9 nm was achieved by C. A. Tan et al. using the main current as low as 16 kA [13]. However, the other Ne-like Ar lasers were not observed by these groups.Except for J = 0-1 transition at 46.9 nm, EUV lasers can also be expected on some other 3p-3s transitions of Ne-like Ar in principle. The populations and gain coefficients of the 3p-3s transitions in Ne-like Ar were investigated by D. E. Kim et al. in theory [17]. It was found that large gains on the 3p 1 S 0 -3s 1 P 1 (J = 0-1), 3p 3 P 2 -3s 1 P 1 (J = 2-1) and 3p 3 D 2 -3s 3 P 1 (J = 2-1) transitions were formed for the electron density between 10 18 and 10 19 cm −3 . Due to the observation of intense laser on 3p 1 S 0 -3s 1 P 1 (J = 0-1) transition at 46.9 nm (A line), the two other lasers on 3p 3 P 2 -3s 1 P 1 (J = 2-1) transition at 69.8 nm (C line) and 3pAbstract We report the characteristics of 46.9, 69.8 and 72.6 nm lasers of Ne-like Ar in a plasma column pumped by capillary discharge. A main current of 12 kA with rise time of 40 ns was used to generate the plasma in a 35-cmlong capillary. The temporal and spatial characteristics of 46.9 and 69.8 nm laser pulses were measured. The time of lasing onset for the two lasers is about 35 ns. The pulse widths are about 1.3 ns for 46.9 nm laser and 1.2 ns for 69.8 nm laser. The FWHM beam divergences of the 46.9 and 69.8 nm lasers are approximately 0.5 and 0.4 mrad, respectively. The initial pressure ranges for 46.9, 69.8 and 72.6 nm lasers correspond to 13-24, 12.5-20 and 14-20 Pa, respectively. A gain coefficient of 0.58 cm −1 was measured and gain saturation behavior was observed at 46.9 nm, conditioning the initial pressure of 19 Pa. At the same discharge current, a 69.8 nm laser with gain coefficient of 0.41 cm −1 and a 72.6 nm laser with gain coefficient of 0.22 cm −1 were achieved by changing...

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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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Development and characterization of a low current capillary discharge for X-ray laser studies

Cited by 49 publications

References 16 publications

Role of pre-pulse in gas-filled-capillary soft X-ray source

Role of pre-pulse in gas-filled-capillary soft X-ray source

Characteristics of a multi-wavelength Ne-like Ar laser excited by capillary discharge

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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