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Development of a short-pulse, 2.5 MW transmitter operating at 120 MHz for high-magnetic field fusion plasmas is described and experimentally characterized. The transmitter discussed here can be comprised alternatively of a tetrode-based Driver, or a Solid-State-Amplifier (SSA), either of which then excites a tetrode-based Final Power Amplifier (FPA). The FPA is a modified 80 MHz, fixed frequency FMIT (Fusion Materials Irradiation Test) amplifier. Analyses and experimental modifications made to match and operate the transmitter at high power at 120 MHz are described. The final output cavity design was significantly reduced in size for the shorter wavelength and validated through high power operation with the actual tetrode. The experimental schematic, setup, and results of the Driver and FPA output power, gain, bandwidth, efficiency, and frequency range are discussed. Differences between the Driver and SSA exciting the FPA are identified. Future work is also considered. [ABSTRACT FROM AUTHOR]

Ion Cyclotron Range of Frequency (ICRF) heating systems are anticipated to be a primary auxiliary heating source in next step fusion tokamak experiments. For high field devices, multi-megawatt ICRF sources above 100 MHz will be required since the ion resonance frequency scales with magnetic field. In this project, we seek to develop a 2 MW, 120 MHz RF source that incorporates a single solid-state amplifier stage (SSA) with a final power amplifier (FPA) utilizing the 4CM2500KG tetrode since it previously achieved 1.7 MW for 5.4 s at 131 MHz [1]. The plan is to modify a fixed 80 MHz Fusion Material Irradiation Test (FMIT) [2] system which is a three-stage amplifier with a 10 kW solid-state initial power stage (IPA) and two consecutive tetrode-based amplifier stages. Based upon C-Mod experience, a single SSA driver offered increased modularity, decreased operational cost, and higher reliability. From the output power perspective, the most restrictive limitation is the FPA tube screen power dissipation thus we sought a plate impedance between 50-70 Ω to minimize the screen current. With an input impedance of 2.7-4 Ω, a full surrogate dummy tube was manufactured to allow exploration of the existing cavity matching range and guide modifications. As expected, the cavities required significant reduction. Using short pulses (<1 ms) and a modified 4CW100000E based driver tetrode, the 120 MHz FMIT has achieved 1.7 MW with reasonable screen current, 4 A, into a matched load. Based on previous reported results, the tube is not near its operating limits [1]. The primary limitation has been the driver and further optimization of the tube-based driver or integration of the SSA offer paths to higher performance. For the SSA, the required performance is dependent upon the gain of the FPA and tolerance to reflected power from the FPA. Based on reported FPA tube operations, a gain factor of 12-14 is expected corresponding to required drive power of 140 - 165 kW to achieve 2 MW output from FPA. We selected a SSA from Cryoelectra that combines ten 20 kW modules for 175 kW output power with VSWR of <1.33. If greater drive power or reflected power tolerance is required, an additional 40 kW can be added without significant design modification. Since the market for tube-based transmitters has been drastically reduced, one of the critical challenges is to secure the tube supply chain. The most critical elements are the pyrolytic screen and control grids. We embarked on a grid deposition, machining and laser cutting development with a goal to create 3 sets of grids for the 4CM2500KG. We obtained acceptable control grids after a few attempts; however, the screen grids required additional adjustments to obtain reliable screen grids. The latest simulations, design and system performance will be presented. Work supported by the MIT Energy Initiative. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is gypsum generated during phosphoric acid production. PG is stocked in large stacks or accumulated in lakes; it contains heavy metals and naturally occurring radioactive elements. The metal contamination may affect the functionality, sustainability and biodiversity of ecosystems. In this work, PG samples were analyzed by Plasma Spectrometry. Total metal content and in the extractable fraction of chemical elements were determined. For K, Ni, Zn, Cr, Cd, Ba, Pb and U, the results obtained are lower than those obtained in a Idaho plant are including and also lower than those found in the soil, indicating this PG sample analyzed probably will not cause any additional metal neither natural radiation contamination. [ABSTRACT FROM AUTHOR]

A new, non-radiographic diagnostic has been developed that appears to provide information on multiple spall and damage layers in metals. The velocities of multiple layers (up to 5 in copper) can be determined using this method, with additional information possible on damaged material between layers at densities less than the bulk metal value. Metals that are melted on release (tin) also seem to exhibit a distinctive signature that is quite different from conventional multi-layer spall. Experimental results on these metals and proton radiographs confirming these results are also presented. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We address the possibility in factorization proofs that low-energy collinear gluons can couple to soft gluons. [ABSTRACT FROM AUTHOR]