We can also ask how fast the plasma will respond to an external disturbance, which could be due to Note that the current density is often not constant, so a weighted summation (Equation [1]) is needed. The density of neutrals in the edge area of the plasma in the EAST ranges from 10 15 to 10 18 m −3, the electron temperature (T e) ranges from 1 to 10 eV, and the electron density (n e) is about 10 18 m −3. Xe + Plasma FIB (PFIB) has much higher maximum current, which allows high throughput milling for large volume characterization, while also eliminating Ga + contamination of the sample. Note that for circular, high aspect ratio plasmas, B T/qR ∼ I P/a2. Figure 1. The reduction of the plasma density is unexpected. High-density plasmas have been produced in a wide range of parameters (toroidal magnetic field: B T =5T–8T, plasma current: I P =0.36–0.7 … Ga + FIB delivers good results for sample preparation and nano-prototyping due to its small spot size and high current density. However, its reproduction by using magnetic measurements solely is recognized to yield an ill-posed problem. Precision plasma systems (high current density) are designed and engineered to produce the sharpest, highest quality cuts that are achievable with plasma. This was in contradiction with the lower electron current extracted from cesium seeded plasma. Going back to Eq. The Boltzmann relation Eq. It has been suggested that cesium is efficiently ionized in the discharge, which would result in a much higher plasma density for a given discharge power. Finally, suppose a medium (material) has an electric conductivity given by (which is measured in Siemens/meter, which is the oppose (inverse) of resistance per length). Plasma current density distribution is one of the most important controlled variables to determine plasma performance of energy confinement and stability in a tokamak. The torch and consumable designs are more complex, and additional pieces are included to further constrict and shape the arc. (1), we can evaluate the ion current density at the sheath boundary, where n. i = n. e. and v. i = v. B. Then the electric current density can be related to the Electric Field by Equation [3]: Operation is bounded by a low-density limit characterized by run-away fast electrons and a high-density limit proportional to the plasma current. A schematic of the operating space for tokamaks or RFPs. The current of the plasma plume is estimated by subtracting the ground line current from the power line current in the circuit. 2: Examples of plasma types in the density temperature plane 1.4 Plasma oscillations So far we have considered characteristics, such as density and temperature, of a plasma in equilibrium. The density of plasma plume n is estimated from the plasma plume current I and the drift velocity v as I = envS, where S is the cross section of plasma plume. the current density [23,24]. For these purposes, a diamagnetic loop with its compensation coil, and also an array of magnetic probes were designed, constructed, and installed on outer surface of the IR-T1 tokamak chamber, and then the poloidal beta and poloidal and radial magnetic fields … The theoretical analysis of plasma current density measurements has been extended to include non-cylindrically symmetric systems. This can be similar to a displacement current, but it is generally driven by bulk particle motion.. Side Note: The current density is not just due to the electron drift. A polarization current can be driven by something that causes a time-varying electric field, like a gradient drift which forces positive and negative charges to drift in opposite directions. A model has been developed to assist in the design of a high current hollow cathode arc that will serve as a test bed for developing ion beam probe measurements of plasma current density. Fig. The purposes of this paper are determination of the current density and safety factor profiles, J(r) and q(r), in IR-T1 tokamak. The plasma plume is estimated by subtracting the ground line current in circuit... Constrict and shape the arc current of the most important controlled variables determine! To further constrict and shape the arc this was in contradiction with the lower electron extracted. Electrons and a high-density limit proportional to the plasma current density is often not constant so! Is bounded by a low-density limit characterized by run-away fast electrons and a high-density limit proportional to the plume..., high aspect ratio plasmas, B T/qR ∼ I P/a2 an ill-posed problem and consumable designs more! 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