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CPMI is a big proponent of lithium as the most promising fusion PFC with both Dr. Ruzic and Dr. Andruczyk having extensive experience and current projects working with lithium or its alloys. 

•Material Attacked by Lithium Corrosion Experiment (MALiCE).

•Extended static molten lithium exposure.

•6 individual canisters.

•Canisters held at 1 to 5 PSI of Ar during exposure.

•Spinning Lithium Attacked Potential Substrates (SLAPS).

•Extended dynamic molten lithium exposure.

•8 samples in 1 experimental session.

•Corrosion tests conducted under high vacuum.

The Solid/Liquid Divertor Experiment (SLiDE) chamber is used to expose divertor concepts to fusion relevant heat fluxes to test their viability.

•Solid/Liquid Divertor Experiment (SLiDE) chamber to test divertor concepts under representative heat fluxes.

•SLiDE generates a E-beam or a ECR plasma.

•Focuses on liquid metal divertor concepts.

•Loop allows liquid metal flow for extended periods without substantial contamination build-up. 

•Lithium engineering and de-risking is additional goal for Li loop construction and operation.

•Modular Li loop allows components to be added or removed as needed for testing, cleaning or any planned upgrades/modifications.

Extreme ultraviolet (EUV) light at the desired wavelength, 13.5 nm, is created through very high energy releases of photons due to the de-excitation of heavily ionized tin, Sn¹⁴⁺. This degree of ionization is only possible in a strong plasma, which in industry is created by irradiating tin droplets with a high-power laser. A large problem associated with this type of EUV source is tin debris buildup on the mirror, leading to reduced EUV intensity over time as the mirror gets dirtier. Previously, work has been done at the Center for Plasma-Material Interactions (CPMI) to use a hydrogen plasma to etch the tin off the surface of the mirror, effectively cleaning it in-situ. Although effective for cleaning, debris can still damage the mirror due to high energies. A small scale EUV source has been created, allowing for less intensive experimentation on tin debris within the chamber. This source is called MK-III and is shown on the right. The laser is pulsed at various powers, creating varying intensities of EUV as plotted below. After laser pulses, the tin target is irradiated, creating EUV light and creating tin debris within the chamber. Hydrogen gas is flowed in the chamber at 100 sccm at various pressures, finding better debris removal at lower pressures as shown in the SEM images.

Radicals are very important for many of the processes that occur during the production of computer chips and other processes involving plasmas. However, the direct measurement of radical density is difficult due to their reactivity and tendency to recombine with themselves. Instead, by catalyzing the recombination process and measuring the heat released, one can infer the density of radicals present in a system at equilibrium. For probes not at equilibrium, the temperature time derivatives become important, treating the probes as 0D objects with heating and cooling terms. F-radical measurement is especially difficult due to catalyst fouling and low F-F recombination coefficients. Etching-based probes use the high etch rates of fluorine to improve measurement signal. Since thin coatings etch too quickly, pellets containing thermocouples that measure dT/dt can be used instead, allowing for the calculation of density. Al and W pellet probes were placed in SF₆ and NF₃ plasmas, comparing measurements of F radical density to spectroscopy. Comparing probes made of al, the aluminum probe is only heated by the plasma, whereas the tungsten turns red hot due to the creation of WF_6, showing material sensitivity.

• Elastomer O-rings are commonly used as vacuum seals, O-ring degradation and particulate generation has been observed in some plasmas systems
• Mechanistic understanding of O-ring degradation from plasma exposure could enable new, resilient elastomer development
• Degradation tests conducted in semiconductor industry relevant gases and chamber layout
• Etching species diagnostic experiments
• Prototype radical probes designed and tested to measure F radicals in SF6 and NF3 plasmas

•Time and Energy resolved Mass Spectroscopy, allows for differentiation between metal and gas ions
• Ion Energy Distribution Functions (IEDF)
• Time resolved measurement of ion energy during a HiPIMS pulse showing energy increase during the kick
• Electron Energy Distribution Functions (EEDF)
• Shows the evolution of the electron energy as well as plasma density during the discharge

Pulsed deposition technique
• Up to 100’s of kW peak power for the same average power as direct current magnetron sputtering (DCMS)
• High peak power means electron density can be 2 orders of magnitude higher for HiPIMS than DCMS
• Higher electron density leads to higher ionization fraction which improves film density, hardness, and conformality
• Positive voltage pulse (kick ) following the main pulse enables control over the ion energy

• CCPs are simple, low impurity plasmas commonly used for processing. EEDF influences the rate of reactions and collisions, impacting species generation and processing parameters
• EEDF varies over the course of one RF cycle (74 ns period in 13.56 MHz supply)
• ns resolution time resolved Langmuir probe used to measure electron density and EEDF throughout the RF cycle.

This work uses a time-resolved Langmuir probe to measure the electron energy distribution function (EEDF) in a capacitively-coupled parallel-plate (CCP) plasma reactor. The EEDF completely determines the plasma chemistry in a low-temperature plasma, and that is why it is so important to obtain. By seeing how the EEDF changes throughout an RF cycle, both as a function of time and position, one then knows the extent by which altering the RF waveform can affect the energy of the electrons. Often industry mixes RF frequencies to alter the plasma — particularly the ion energy distribution at the substrate. Here we add a second frequency in a systematic manner and examine the changes in the instantaneous EEDF. We also examine the turn on and turn off times of the RF generator itself. Specialized circuits were designed for this work to ensure high frequency fidelity so digitization at 1.5 GHz is possible and accurate. A set of experiments were conducted to show how only altering circuit parameters affect the results, and steps were taken to eliminate those effects. Spatial variations of the resulting EEDFs were investigated, especially near the edge of the CCP reactor, to see which aspects change the most with radius.