Session JP15: Poster Session: Fundamental Plasmas: Plasma Sources (2:00pm - 5:00pm)

Suppression of ions acceleration in laser produced plasmas for EUV lithography and soft x-ray sources.

Development of efficient and bright photon sources emitting in narrow band of EUV or soft x-ray range is of current interests for semiconductor industries as well as for biomedical and nanotechnology applications. Laser produced plasmas (LPP) is currently most feasible way to create compact photon sources. Beside the requirements of high efficiency and power of these sources, prevention and mitigation of damage to collecting optics from energetic plasma ions is critical for device lifetime. We studied the mechanisms affecting ions acceleration in LPP using 3D comprehensive models integrated in HEIGHTS computer package. Our simulation indicated that increasing the pulse width of 2 micrometer laser system interacting with small Sn droplets leads to improvement of EUV source efficiency and significant reduction in the energies of generated ions. Tuning laser pulse duration and temporal laser intensity predicted 3-4 times reduction in ion kinetic energies while the source efficiency continued to improve and saturated at 40 ns (FWHM) laser pulse duration. These results are explained based on the fundamentals of laser interaction with targets and with the evolving plasma. Comparison of ion energies, charges, and fluxes to experimental data are presented.   

High power electron beam for plasma heating

A high power electron beam for plasma heating has been developed at TAE Technologies. The electron beam is designed to achieve up to 200 A electron current at 30 kV accelerating voltage with pulse duration up to 6 ms. Electrons are extracted from a plasma emitter and accelerated by multi-aperture accelerating grids. The beam is transported to the injection port through a grounded drift tube. The plasma emitter of electrons is immersed in an external axial magnetic field to provide conditions for axial injection through the magnetic plug into the confinement volume of the C2W. The combination of high beam current, relatively low accelerating voltage, and long pulse duration result in extremely high beam perveance with additional measures taken to mitigate the space charge effects that otherwise dominate the behavior of the beam in the drift space. One way to reduce unwanted space-charge effects is to produce an annular-shaped hollow beam. Another way to neutralize space charge of the beam is to control gas conditions inside the drift space such that the beam ionizes residual ambient gas, and the ions are captured into the potential well created by the electron beam. In this poster, is reported the design and the physics of the electron beam. Are shared the estimations of beam transport into the plasma. Are discussed some preliminary considerations regarding the beam-plasma interactions.   

Design and Characterization of a Centimeter-Scale Coaxial Plasma Railgun

A small coaxial plasma railgun has been designed to produce jets of argon-helium plasma with electron density $\approx10^{16}$~$\mathrm{cm}^{-3}$, temperature $\approx$1--2~eV, and velocity $\approx$10--20~km/s. These parameters closely match those of jets produced by an existing linear plasma-armature railgun used to study the underlying physics of shocks in multi-ion-species plasmas. The coaxial design is anticipated to improve control of the species mixture in the jets produced by the railgun. The railgun is sized to fit within a KF-40 full nipple such that the railgun can be simply mounted and removed from the vacuum chamber. All components are modular and serviceability is assured by eschewing the use of adhesives. This new railgun consists of two tubular, tungsten-copper, coaxial electrodes with a glass-ceramic breech insulator. Gas is injected using a gas puff valve to prefill the railgun. The railgun is operated at a maximum current of 90~kA and a maximum voltage of 11~kV using an LC pulse forming network. Low current operation limits jet velocity, but extends component lifetimes.   

Updates on Plasma Diagnostics Development on the Helicon Plasma Experiment (HPX)

The small Helicon Plasma Experiment (HPX) at the Coast Guard Academy Plasma Lab (CGAPL), continues to progress toward utilizing the reputed high densities (1013 cm-3 and higher) at low pressure (.01 T) of helicons, for eventual high temperature and density diagnostic development in future laboratory investigations. HPX has installed an Impedans Langmuir probe and constructed an RF-shielded triple probe experimental diagnostic to compare the plasma's density, temperature, and behavior during experiments. Our 2.5 J YAG laser Thomson Scattering system operates at its first and second harmonic, 532 and 1064 nm respectively. It utilizes a high-performance volume-phase-holographic (VPH) grating spectrometer and a charge coupled device (CCD) camera with a range of 380-1090 nm with a resolution of 1024x1024 for second harmonic (532 nm) photon emissions. At 1064 nm, a new polychromator has been procured from General Atomics optimized for TS measurements of 5 eV \textless Te \textless 2000 eV over a 109-degree scattering angle. Progress on the construction of the RF coupling system, Helicon Mode development, and observations from the Thomson Scattering, particle, and electromagnetic scattering diagnostics will be reported.