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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Acceleration mechanisms of energetic ion debris in laser-driven tin plasma EUV sources

Laser-driven tin plasmas are driving new-generation nanolithography as sources of extreme ultraviolet (EUV) radiation centered at 13.5 nm. A major challenge facing industrial EUV source development is predicting energetic ion debris produced during the plasma expansion that may damage the sensitive EUV channeling multilayer optics. Gaining a detailed understanding of the plasma dynamics and ion acceleration mechanisms in these sources could provide critical insights for designing debris mitigation strategies in future high-power EUV sources. Here, we develop a fully kinetic model of tin-EUV sources using one-dimensional particle-in-cell simulations to study ion debris acceleration, which will be valuable for cross-validation of radiation-hydrodynamic simulations. An inverse-bremsstrahlung heating operator is used to model the interaction of a tin target with an Nd:YAG laser, and thermal conduction is included through a Monte Carlo Coulomb collision operator. While the large-scale evolution is in reasonable agreement with analogous hydrodynamic simulations, the significant timescale for collisional equilibration between electrons and ions allows for the development of prominent two-temperature features. A collimated flow of energetic ions is produced with a spectrum that is significantly enhanced at high energies compared to fluid simulations. The dominant acceleration mechanism is found to be a large-scale electric field supported mainly by the electron pressure gradient, which is enhanced in the kinetic simulations due to the increased electron temperature. We discuss the implications of these results for future modeling of tin-EUV sources and the development of debris mitigation schemes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Review of the 1st EUV Light Sources Code Comparison Workshop

We review the results of the 1 st Extreme Ultraviolet (EUV) Light Sources Code Comparison Workshop. The goal of this workshop was to provide a platform for specialists in EUV light source plasma modeling to benchmark and validate their numerical codes using well-defined case studies. Detailed consideration of a plethora of atomic collisional and radiative processes is required for modeling EUV light source plasmas. Eight institutions spanning four countries contributed data to the workshop. Two topics were addressed, namely (i) the atomic kinetics and radiative properties of tin plasmas under EUV-generating conditions and (ii) laser absorption in a fully ionized, one-dimensional hydrogen plasma. In this paper, we summarize the key findings of the workshop and outline plans for future iterations of the code comparison activity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Multiply-excited states and their contribution to opacity in CO 2 laser-driven tin-plasma conditions

A recent study (2020 Nat. Commun. 11 2334) has found that transitions between multiply-excited configurations in open 4d-subshell tin ions are the dominant contributors to intense EUV emission from dense, Nd:YAG-driven (laser wavelength λ = 1.064 μm) tin plasmas. In the present study, we employ the Los Alamos Atomic code to investigate the spectral contribution from these transitions under industrially-relevant, CO 2 laser-driven (λ = 10.6 μm) tin plasma conditions. First, we employ Busquet's ionisation temperature method to match the average charge state < Z > of a non-local-thermodynamic equilibrium (non-LTE) plasma with an LTE one. This is done by varying the temperature of the LTE calculations until a so-called ionisation temperature T Z is established. Importantly, this approach generates LTE-computed configuration populations in excellent agreement with the non-LTE populations. A corollary of this observation is that the non-LTE populations are well-described by Boltzmann-type exponential distributions having effective temperatures T eff ≈ T Z . In the second part of this work, we perform extensive level-resolved LTE opacity calculations at T Z . It is found that 66% of the opacity in the industrially-relevant 2% bandwidth centred at 13.5 nm arises from transitions between multiply-excited states. These results reinforce the need for the consideration of complex, multiply-excited states in modelling the radiative properties of laser-driven plasma sources of EUV light.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

Multi-diagnostic characterization of laser-produced tin plasmas for EUV lithography

We present a comprehensive characterization of laser-produced tin (Sn) plasmas relevant to extreme ultraviolet (EUV) lithography using a multi-diagnostic suite integrated into the new experimental platform, “SparkLight.” Tin plasmas are generated by irradiating a continuously moving tin-coated wire with laser pulses (1064 nm, 10 ns, up to 5.7 × 10 10 W/cm 2 ) and probed via coherent Thomson scattering, laser interferometry, and EUV emission spectroscopy. Thomson scattering measurements reveal electron temperatures and densities that decay with distance from the target. Densities derived from Thomson scattering are cross-validated against laser interferometry, showing excellent agreement. Correlating the results of these laser diagnostics with spatially resolved EUV spectroscopy suggests that the bulk of useful EUV emission originates within 150 μm of the target and is generated under suboptimal plasma conditions. This work demonstrates a practical integrated approach for plasma characterization in EUV source development.

Musikhin, S. [Princeton Plasma Physics Laboratory ↗
DOE OSTI2024

Temporal pre-pulse shaping in dual pulse laser produced plasma for the optimization of the EUV source in tin microdroplet system

Dual-laser beams interacting with small droplets of liquid tin are currently the most efficient systems for producing the 13.5 nm EUV photon radiation source required for the next generation microchips. Usually, EUV light is produced during the second main-pulse stage, while the pre-pulse (PP) is used for target preparation, i.e., droplet preheating, vaporization, and target deformation. However, the PP laser energy can be utilized more efficiently if the EUV producing plasma is being developed during the PP stage as well. In this work, we study the ways of optimization of the PP laser temporal shape to achieve conditions for maximum EUV output during the pre-pulse. The size of the deformed droplet is kept optimized for the following main laser pulse. Our simulations showed a significant increase in the EUV output at the pre-pulse stage when a ramping profile is used for the laser temporal shape. Using the ramped square pre-pulse produces 24% gain in the EUV output in comparison with the standard Gaussian temporal profile (i.e., regular Nd:YAG shape) for the same energy of the laser pulse.

36 MATERIALS SCIENCE↗
DOE OSTI2024

EUV FEL light source based on energy recovery linac with on-orbit laser plasma injection

We report on a week-long study of a conceptual design of EUV FEL light source based on an energy recovery linac with on-orbit laser plasma accelerator injection scheme. We carried out this study during USPAS Summer 2023 session of Unifying Physics of Accelerators, Lasers and Plasma applying the art of inventiveness TRIZ. An ultrashort Ti-sapphire laser accelerates electron beams from a gas target with mean energy of 20 MeV, which are then ramped up to 1 GeV in a five-turn scheme with a series of fixed field alternating magnets and two superconducting RF cavities (100 MeV per cavity per turn). The electron beam is then bypassed to an undulator line optimized to generate EUV light of 13.5 nm at kW level in a single pass.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Self-consistent integrated modeling of combined hybrid discharge-laser produced plasma devices for extreme ultraviolet metrology

Discharge- and laser-produced plasma (DLPP) devices are being used as light sources for extreme ultraviolet (EUV) generation. A key challenge for both, DPP and LPP, is achieving sufficient brightness to support the throughput requirements of nanometrology tools. To simulate the environment of a hybrid DLPP device and optimize the EUV output, we have developed an integrated HEIGHTS-DLPP computer simulation package. The package integrates simulation of two evolving plasmas (DPP and LPP) and includes modeling of a set of integrated self-consistent processes: external power source and plasma energy balance, plasma resistive magnetohydrodynamics, plasma heat conduction, detailed radiation transport (RT), and laser absorption and refraction. We simulated and optimized DLPP devices using Xe gas as a target material. We synchronized the external circuit parameters, chamber gas parameters, and laser beam temporal and spatial profiles to achieve maximum EUV output. The full 3D Monte Carlo scheme was integrated for detailed RT and EUV output calculations in Xe using more than 3600 spectral groups. The modeling results are in good agreement with Julich Forschungszentrum experimental data. Theoretical models, developed and integrated into the HEIGHTS package, showed wide capabilities and flexibility. In conclusion, the models and package can be used for optimization of the experimental parameters and settings, investigation of DLPP devices with complex design, analyzing the impact of integrated spatial effects and working timeline arrangement on the final EUV output, and EUV source size, shape, and angular distribution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Tin removal by an annular surface wave plasma antenna in an extreme ultraviolet lithography source

Tin contamination of the collector mirror surface remains one of the crucial issues of EUV (Extreme Ultraviolet) sources, directly impacting the availability of the tool. Hydrogen plasma-based tin removal processes employ hydrogen radicals and ions to interact with tin deposits to form gaseous tin hydride (SnH 4 ), which can be removed through pumping. An annular surface wave plasma (SWP) source developed at the University of Illinois—Urbana Champaign is integrated into the cone and perimeter of the collection mirror for in situ tin removal. The SWP is characterized by high ion and radical densities, low electron temperature, and local generation where etching is needed. This method has the potential to significantly reduce downtime and increase mirror lifetime. Radical probe measurements show hydrogen radical densities in the order of 10 19 m -3 , while Langmuir probe measurements show electron temperatures of up to 6 eV and plasma densities on the order of 10 17–18 m -3 . The generated ions are essential to the tin cleaning and have sufficiently low energy to cause no damage to the collector capping layer. Tin etch rates of up to 270 nm/min were observed in a variety of experimental conditions, including various powers, pressures, flowrates, and temperatures. In conclusion, the high etch rates demonstrated in this study exceed the expected contamination rate of the EUV source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1980

Point source contributions to the extreme ultraviolet background

The results of the Apollo-Soyuz extreme ultraviolet (EUV)/soft X-ray diffuse background survey are analyzed to assess the contribution of discrete-sources with blackbody or coronal plasma spectra. Blackbody emitters in the EUV must be less luminous and more numerous than hot white dwarfs in order to produce the bulk of the diffuse flux. Significant contributions to the EUV background appear likely only if sufficient numbers of white dwarfs possess low temperature coronae similar to the one suggested for Sirius B.

Stern, R.↗
NASA NTRS2013

Coordinated Observations of X-ray and High-resolution EUV Active Region Dynamics

The recently-launched High-resolution Coronal imager (Hi-C) sounding rocket provided the highest resolution images of coronal loops and other small-scale structures in the 193 Angstrom passband to date. With just 5 minutes of observations, the instrument recorded a variety of dynamic coronal events -- including even a small B-class flare. We will present our results comparing these extreme-ultraviolet (EUV) observations with X-ray imaging from Hinode/XRT as well as EUV AIA data to identify sources of hot plasma rooted in the photosphere and track their affect on the overall topology and dynamics of the active region.

Savage, Sabrina↗
NASA NTRS2013

Coordinated Observations of X-ray and High-Resolution EUV Active Region Dynamics

The recently-launched High-resolution Coronal imager (Hi-C) sounding rocket provided the highest resolution images of coronal loops and other small-scale structures in the 193 Angstrom passband to date. With just 5 minutes of observations, the instrument recorded a variety of dynamic coronal events -- including even a small B-class flare. We will present our results comparing these extreme-ultraviolet (EUV) observations with X-ray imaging from Hinode/XRT as well as EUV AIA data to identify sources of hot plasma rooted in the photosphere and track their affect on the overall topology and dynamics of the active region.

Savage, Sabrina↗
DOE OSTI2021

EUV and Hard X-ray Hartmann Wavefront Sensing for Optical Metrology, Alignment and Phase Imaging

For more than 15 years, Imagine Optic have developed Extreme Ultra Violet (EUV) and X-ray Hartmann wavefront sensors for metrology and imaging applications. These sensors are compatible with a wide range of X-ray sources: from synchrotrons, Free Electron Lasers, laser-driven betatron and plasma-based EUV lasers to High Harmonic Generation. In this paper, we first describe the principle of a Hartmann sensor and give some key parameters to design a high-performance sensor. We also present different applications from metrology (for manual or automatic alignment of optics), to soft X-ray source optimization and X-ray imaging.

20 metrology↗
DOE OSTI2023

EUV debris mitigation using magnetic nulls

Next generation EUV sources for photolithography use light produced by laser-produced plasmas (LPP) from ablated tin droplets. A major challenge for extending the lifetime of these devices is mitigating damage caused by deposition of tin debris on the sensitive collection mirror. Especially difficult to stop are high energy (up to 10 keV) highly charged tin ions created in the plasma. Existing solutions include the use of stopping gas, electric fields, and magnetic fields. One common configuration consists of a magnetic field perpendicular to the EUV emission direction, but such a system can result in ion populations that are trapped rather than removed. Here we investigate a previously unconsidered mitigation geometry consisting of a magnetic null by performing full-orbit integration of the ion trajectories in an EUV system with realistic dimensions and optimize the coil locations for the null configuration. The magnetic null prevents a fraction of ions from hitting the mirror comparable to that of the perpendicular field, but does not trap any ions due to the chaotic nature of ion trajectories that pass close to the null. This technology can potentially improve LPP-based EUV photolithography system efficiency and lifetime and may allow for a different, more efficient formulation of buffer gas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1982

The Venus ionosphere at grazing incidence of solar radiation - Transport of plasma to the night ionosphere

A quasi-two-dimensional model of the Venusian ionosphere is used to calculate the ion number densities and horizontal ion bulk velocities expected for a range of solar zenith angles near the terminator (80-100 deg). These results are compared with data from the Pioneer Venus Orbiter retarding potential analyzer. It is shown that antisunward horizontal plasma fluxes produced by solar EUV-induced pressure gradients are sufficient to maintain the nighttime ionosphere. While photoionization is the dominant source of ionospheric plasma for solar zenith angles less than 92 deg, plasma transport from the dayside is the dominant plasma source for solar zenith angles greater than 95 deg. It is also shown that the main nightside plasma peak at a height of 140 km is of the F2 type; its height and shape are therefore quite insensitive to the height of the ion source.

Whitten, R. C.↗
NASA NTRS2014

International Space Station Columbus Payload SoLACES Degradation Assessment

SOLAR is a European Space Agency (ESA) payload deployed on the International Space Station (ISS) and located on the Columbus Laboratory. It is located on the Columbus External Payload Facility in a zenith location. The objective of the SOLAR payload is to study the Sun. The SOLAR payload consists of three instruments that allow for measurement of virtually the entire electromagnetic spectrum (17 nm to 100 um). The three payload instruments are SOVIM (SOlar Variable and Irradiance Monitor), SOLSPEC (SOLar SPECctral Irradiance measurements), and SolACES (SOLar Auto‐Calibrating Extreme UV/UV Spectrophotometers). The SolACES payload includes a set of 4 spectrometers that measure the solar EUV flux from 17 nm to 220 nm. One of these 4 spectrometers failed early on (before deployment). EUV data is important in understanding the solar dynamo. Also, EUV flux is the source of most of the ionization that produces the ionosphere plasma. Plasma production is important in understanding the ionosphere environment. The ionosphere conditions affect many subjects including spacecraft charging, dynamo processes, instabilities, and communications. The 3 remaining spectrometers have collected valuable data during the historically low solar cycle 24. Some of this data will be presented. A significant trend in degradation of the remaining SolACES spectrometers was observed towards the end of CY2010 (GMT 310) through mid CY 2011 (GMT 132). The Principle Investigators of SolACES initiated a Mission Evaluation Room (MER) Chit to request an investigation of the degradation in CY 2011 (GMT 230). The Boeing Space Environments team was asked to respond to the ESA initiated MER Chit request to investigate the cause of the degradation. This paper will discuss the findings of that investigation.

Harman, William↗