Spherical 3-Axis Hall Probe Array Calibration and Implementation for The Big Red Ball*

A 3-axis Helmholtz coil capable of producing 100 G magnetic fields at frequencies ranging from DC to 1 kHz has been built to calibrate an array of 3-axis hall probes. Accurate magnetic field measurements are necessary for diagnosing plasma equilibria and the presence of any MHD instabilities. The array will consist of three single-axis Hall sensors mounted orthogonally, each of which has a frequency response of 100 kHz and a sensitivity of 28$\frac{mV}{G}$. These probes will be placed on the inner surface of the machine to create a spherical array of sensors. Such an array will provide the necessary data to constrain plasma equilibrium parameters, such as current density and plasma pressure from $\nabla{P} = J \times B$. Understanding the plasma equilibrium, and large-scale magnetic fields is critical to understanding the dynamics involved in many phenomena, like the dynamo. Details on the design, calibration, and implementation of the three-axis Helmholtz coil and Hall sensors will be presented.