Grazing Incidence Pumping Research Articles

Study of the luminescence from polymeric membrane swollen in water with various content of deuterium; isotopic effects

The paper describes the experiments with the irradiation in the near UV range of a swollen surface of Nafion polymer membrane in the grazing-incidence pumping geometry. The pump radiation caused a photoluminescence from the Nafion interface in a certain spectral range. The photoluminescence signal proved to be an important parameter for describing the swelling of the polymer in water. It is shown that luminescence is generated due to the presence of sulfonic groups, anchored to the ends of the perfluorovinyl ether groups forming a tetrafluoroethylene (Teflon) base. The dynamics of Nafion swelling was studied depending on the content of deuterium in water. In the case where the polymer is swollen in water with different deuterium content, isotopic effects appeared to be largely manifested.

Experimental demonstration of a collinear triple pulse grazing-incidence pumping scheme for a transient collisional pumped x-ray laser

We present a nickel-like Molybdenum x-ray laser (XRL) based on the transient collisional excitation scheme. Extending the double grazing-incidence pumping scheme to a triple pulse scheme with a nanosecond pre-pulse and two consecutive 3 ps pulses the output power of the XRL can be ∼6 times increased compared to existing configurations, while using a relatively low total pump energy of 0.7 J. Additionally we show that this setup can be extended to a double stage, oscillator and amplifier stage, XRL.

Double-stage soft x-ray laser pumped by multiple pulses applied in grazing incidence

In this paper we report on results obtained with a compact double-stage molybdenum x-ray laser (XRL), operated with a total pump energy of 600 mJ. The two gain regions were pumped using the double-pulse grazing incidence pumping technique, which includes travelling wave excitation for both the seed- and the amplifier-target. In addition, the influence of an additional pre-pulse has been studied. Seeded XRL operation has been demonstrated in both schemes, resulting in XRL pulses with a divergence of 2 × 2 mrad. The peak brilliance of the amplified XRL of 4 × 1023 photons/s/mm2/mrad2 in 5 × 10−5 relative bandwidth was more than two orders of magnitude larger compared to the original seed pulses. The presented experimental concept provides an alternative approach to the currently more common use of high-order harmonic pulses as a seed source, well suited for applications like laser spectroscopy of highly-charged ions at a storage ring.

Q-switched laser-assisted grazing incidence pumping (QAGRIP) for efficient soft x-ray laser generation.

We have investigated a new scheme for laser plasma transient collisional soft x-ray lasers based on the use of an additional laser to produce the preplasma. Soft x-ray emission measurements made for different solid targets are presented and discussed. A significant enhancement of the SXRL emission as compared to double-pulse single-beam grazing incidence (DGRIP) using the same pump laser is reported for 13.9- and 32.6-nm SXRL wavelengths.

Implementing the plasma-lasing potential for tabletop nano-imaging

Implementing the plasma-lasing potential for tabletop nano-imaging on across a hot plasma medium drives short-wavelength lasing, promising for "turnkey" nano-imaging setups. A systematic study of the illumination characteristics, combined with design-adapted objectives, is presented. It is shown how the ultimate nano-scale feature is dictated by either the diffraction-limited or the wavefront-limited resolution, which imposed a combined study of both the source and the optics. For nano-imaging, the spatial homogeneity of the illumination (spot noise) was shown as critical. Plasma-lasing from a triple grazing-incidence pumping scheme compensated for the missing spot homogeneity in classical schemes. We demonstrate that a collimating mirror pre-conditions both the pointing stability and the divergence below half a mrad.

Pump energy reduction for a high gain Ag X-ray laser using one long and two short pump pulses

A pump scheme with one long and two short pump pulses is proposed, in a grazing incidence pumping x-ray laser (XRL) configuration. A 360 ps long pulse, prepares a plasma in a low charge state. Then, an initial short pulse ionizes the plasma to an optimal charge state, while the second short pulse induces strong collisional excitation in the gain region. With only 200 mJ of pump energy on target, a compact Ag XRL at 13.9 nm with a gain coefficient of 55 cm(-1) was achieved.

Preplasma conditions for collisional Mo soft x-ray lasers with the grazing incidence pumping scheme

By comparing soft x-ray spectra from experiments with numerical calculation results, the preformed plasma medium was characterized for Mo 18.9nm x-ray lasers with the grazing incidence pumping scheme. The effects of prepulse intensities and durations on the charge state distributions as well as other parameters of preformed plasmas were investigated for previously demonstrated soft x-ray lasers. Experiments with small total energy were conducted to check the understanding of reasons why Mo 18.9nm soft x-ray lasers were realized on laser facility platforms with parameters varying so much.

Optimization of a tabletop high-repetition-rate soft x-ray laser pumped in double-pulse single-beam grazing incidence

This Letter reports on the optimization of a tabletop nickel-like molybdenum transient collisionally excited soft x-ray laser (SXRL) at 18.9 nm performed by a double-pulse single-beam grazing incidence pumping (DGRIP). This scheme allows for the first time, to our knowledge, the full control of the pump laser parameters including the pre-pulse duration optimally generating the SXRL amplifier under a grazing incidence. The single-beam geometry of the collinear double-pulse propagation guarantees the ideal overlap of the pre-pulse and main pulse from shot to shot resulting in a more efficient and highly stable SXRL output. SXRL energies up to 2.2 microJ are obtained with a total pump energy less than 1 J for several hours at a 10 Hz repetition rate without realignment under once optimized double pumping pulse parameters including energy ratio, time delay, pre-pulse and main pulse durations, and line focus width.

Gain-saturated Ni-like antimony laser at 11.4nm in grazing-incidence pumping geometry

Abstract We report on gain-saturated operation of the 4d → 4p, J = 0–1, 11.4 nm soft-X-ray laser line in Ni-like antimony (Sb) at a pump energy of only 2.5 J. The driving laser used was a 1054 nm Nd:glass CPA laser system with a pulse duration of 7 ps (FWHM). The pump beam was focused with a tilted on-axis parabolic mirror in a grazing-incidence (GRIP) pumping configuration at an incidence angle of 45°. A fraction of 2.8% of the pump energy (∼70 mJ) was used for the prepulse, which was propagated along the same beam line as the main pulse and arrived at the target 4.4 ns before the main pulse.

Grazing incidence pumping of an 18.9 nm Ni-like Mo X-ray laser

Results of an experiment investigating the grazing-incidence pumping of a Ni-like Mo X-ray laser are presented. The X-ray laser was produced with a 600 mJ, 500 ps background pulse and a 250 mJ, 240 fs main pulse. X-ray laser output was measured using a flat-field spectrometer modified to record both the first- and second-order output of the molybdenum lasing emission. Time-resolved data was obtained using an Axis-Photonique PX1 X-ray streak camera coupled to the first order output of the flat-field spectrometer. It is shown that saturated X-ray laser output is produced with energy up to 150 nJ, and pulse duration of typically 1.7 ps for a range of grazing angles and delays between the background and main pulse. The experimental data is interpreted in terms of a model taking account of the expected ASE variation of X-ray laser output.

Demonstration of Mo Soft X-Ray Lasers with a Grazing Incidence Pumping Scheme in the XL-II Facility

A Ni-like Mo soft x-ray laser (SXRLs) operating at 18.9nm has been demonstrated by employing a grazing incidence pumping scheme with 120mJ in the 200ps pre-pulse and 140mJ in the 200fs main pulse. The SXRL gain is estimated to be 1.5–3cm−1 when a grazing incidence angle of 14° is applied. Numerical simulations are also performed to investigate the dynamics of the ion distribution. It is found that a high intensity at 2.4 × 1014 W/cm2 of the 200 fs main pulse could heat the pre-plasma rapidly to an appropriate temperature for population inversion, and could compensate for the shortage of the total pump energy to a certain extent.

High-repetition-rate chirped-pulse-amplification thin-disk laser system with joule-level pulse energy

We are reporting on the development of a diode-pumped chirped-pulse-amplification (CPA) laser system based on Yb:YAG thin-disk technology with a repetition rate of 100 Hz and output pulse energy in the joule range. The focus lies with the first results of the preamplifier--a regenerative amplifier (RA) and a multipass amplifier (MP). The system consists of a front end including the CPA stretcher followed by an amplifier chain based on Yb:YAG thin-disk amplifiers and the CPA compressor. It is developed in the frame of our x-ray laser (XRL) program and fulfills all requirements for pumping a plasma-based XRL in grazing incidence pumping geometry. Of course it can also be used for other interesting applications. With the RA pulse energies of more than 165 mJ can be realized. At a repetition rate of 100 Hz a stability of 0.8% (1sigma) over a period of more than 45 min has been measured. The optical-to-optical efficiency is 14%. The following MP amplifier can increase the pulse energy to more than 300 mJ. A nearly bandwidth-limited recompression to less than 2 ps could be demonstrated.

Saturated X-ray lasing in Ni-like Sn at 11.9 nm using the GRIP scheme

We report on gain-saturated operation of the 11.9 nm X-ray lasing line in Ni-like Sn using the grazing-incidence pumping scheme (GRIP). The experiments were done with 2-ps duration pump pulses and energies up to 5 J. Strong gain saturation with multi-microjoule output was measured for the Sn laser at a grazing angle of 30° and a pump pulse energy of 3 J. This was achieved with a 4.5%, 2-ps duration prepulse 2.4 ns ahead of the main pulse and also incident at grazing incidence. Increasing laser output was observed at GRIP angles up to 45°. At this angle, the minimum energy required for saturated lasing was determined as ∼2 J.

Characteristics of a Ni-like silver x-ray laser pumped by a single profiled laser pulse

We characterized a Ni-like silver soft x-ray laser realized as, what we believe is, a new variant of the grazing incidence pumping (GRIP) scheme. The x-ray laser was pumped by a single profiled laser pulse from a 10 Hz Ti:sapphire laser system. The Ni-like Ag x-ray laser was saturated with a gain coefficient of 76 cm−1 and an effective gain-length product of 28.2. The spatial characteristics of the new version of GRIP x-ray laser are presented including the far- and near-field beam profiles. Computational modeling of the lasing conditions was used to provide some qualitative explanations of the physical processes occurring in the x-ray laser. Additionally, we obtained some preliminary results on the injection seeding technique applied to the Ni-like Ag active medium using the 59th harmonic of the Ti:sapphire laser pulse as the seed. The single-pulse variant of the pumping scheme proved to be a stable and simple configuration of the table-top x-ray lasers also suitable for the injector-amplifier arrangement.

The lasing temporal characteristics of Ni-like Mo x-ray lasers at 18.9 nm driven by a grazing incidence pumping scheme

We numerically investigate the effects of the time delay between prepulse and main pulse on the lasing characteristics of the Ni-like Mo soft x-ray lasers (XRL) at 18.9 nm driven in a grazing incidence pumping (GRIP) geometry by using a modified 1D hydrodynamic code MED103 coupled with an atomic physics data package and a 2D Ray-tracing code. Typical XRL experiments with lasing action in a broad temporal window for the delay are simulated and analyzed. Investigations show a well-performed preplasma together with the proper main pulse is the key to achieve lasing over a broad range of time delay.

Characterization of a transient collisional Ni-like molybdenum soft-x-ray laser pumped in grazing incidence

We present experimental results from an extensive investigation of a Ni-like Mo x-ray laser pumped in the transient regime and GRIP configuration (GRazing Incidence Pumping). The pump laser is a 10 Hz, 1 J, Ti:sapphire laser system. The main diagnostic is a monochromatic near-field imaging system with a 1.7 micron spatial resolution that shows the soft-x-ray laser source size and position relative to the target surface. Changes of those characteristics are observed for different GRIP angles, varied between $15\ifmmode^\circ\else\textdegree\fi{}$ and $21\ifmmode^\circ\else\textdegree\fi{}$, while keeping all other parameters constant. Intense lasing is observed routinely at 18.9 nm with up to 3 microjoule output energy and stable operation is demonstrated at 10 Hz. We have investigated the role of several pumping parameters, in particular, the relative energy and delay between the long and short pulse. We show that this multiparameter scan leads to a well-defined optimal regime of operation and better understanding of the GRIP configuration. Finally, as the GRIP scheme requires careful tailoring of the plasma conditions to the specific soft-x-ray laser under investigation, we add a prepulse before the plasma producing long pulse to generate large-scale preplasmas. This increases the brightness of the soft-x-ray beam and leads to an almost Gaussian near-field spatial profile.

Demonstration of a saturated Ni-like Ag x-ray laser pumped by a single profiled laser pulse from a 10-Hz Ti:sapphire laser system

A variant of a grazing-incidence pumping (GRIP) scheme for Ni-like x-ray lasers using a single shaped pulse from a 10-Hz Ti:sapphire laser system has been demonstrated. Experimental and numerical results show that efficient excitation leading to the lasing process can be achieved by controlled shaping of the pump laser pulse. Such a pulse has been defined for a silver slab target. A gain coefficient as high as 76 cm{sup -1} was estimated. Results indicate that the nanosecond amplified spontaneous emission background of the leading edge of the driving pulse is decisive for an efficient pumping process in this version of GRIP.

Optimal main pulse angle for different preplasma conditions in transient collisionally pumped x-ray lasers

The effects of the incidence angle of the main pump (MP) pulse in non-normal pumping geometry and the influence of the MP duration are investigated experimentally and theoretically for a transient collisionally pumped (TCE) x-ray laser in Ni-like Zr at 45 degrees and 72 degrees incidence angle on the target. The way they transfer to the x-ray laser output depends on the preplasma conditions, most notably on the average ionization distribution at the arrival of the MP. Moreover, contrary to previous grazing incidence pumping results, it is found that the shortest attainable MP maximizes the output. Modeling of the experimental results is performed with EHYBRID code. The results are important for scaling high repetition-rate non-normal incidence pumped lasers to sub- 10nm wavelengths.

Optimizing the performance of nickel-like collisionally pumped x-ray lasers. II. Lasers for the wavelength range50–100Å

Soft x-ray lasers operating in the super- $100\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ regime and using grazing incidence pumping methods are now established as efficient sources of radiation in this waveband. The concepts underlying this approach are to separate the ionization and excitation phases of the laser, and to match the pumping density of the latter to the optimal for gain generation. It is therefore of considerable interest to examine whether these ideas can be successfully applied to sub-$100\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ lasers. Three problems arise: first the adverse scaling of ionization with temperature for high atomic number ions, second the strong thermal conduction at these temperatures leads to a large hot zone upstream of the absorption, and third the optimum pumping density is greater than the critical density of $1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ wavelength, solid state pump lasers. Using analytic models and simulation we identify a strategy to overcome these problems using a pre-pulse of a mixed harmonic and fundamental radiation of Nd-glass laser radiation followed by the main pumping pulse of the fundamental normally incident. Due to the large upstream thermal zone and the high ionization temperature, we find that the energy required in the pre-pulse is much ($\ensuremath{\sim}3$ times) larger than that in the main, and that the energy needed consequently scales rapidly with the atomic number and therefore decreasing x-ray wavelength. Systems generating output energies of a few tens of $\ensuremath{\mu}\mathrm{J}$ are examined at wavelengths between 50 and $70\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$.

Optimization toward a high-average-brightness soft-x-ray laser pumped at grazing incidence

We report the near-field imaging characterization of a 10 Hz Ni-like 18.9 nm molybdenum soft-x-ray laser pumped in a grazing incidence pumping (GRIP) geometry with a table-top laser driver. We investigate the effect of varying the GRIP angle on the spatial behavior of the soft-x-ray laser source. After multiparameter optimization, we were able to find conditions to generate routinely a high-repetition-rate soft-x-ray laser with an energy level of up to 3 microJ/pulse and to 6x10(17) photons/s/mm2/mrad2/(0.1% bandwidth) average brightness and 1x10(28) photons/s/mm2/mrad2/(0.1% bandwidth) peak brightness.