Using Whistlers Waves from LAPD as a Plasma Diagnostic

The presence of whistler waves emanating from the main discharge of the LArge Plasma Device (LAPD) at UCLA has been confirmed in recent (unpublished) work by Prof. Frederick Skiff. This work also describes the remote detection of signals resembling these whistlers which propagate beyond the cylindrical plasma's radial boundary. A diagnostic based on the cold plasma dispersion relationship for whistler waves may offer the potential to remotely estimate the magnetic field strength, the electron cyclotron frequency, the plasma density, and plasma temperature. This experiment seeks to indirectly measure plasma properties by detecting electromagnetic waves that emanate from the plasma. Initial observations using a collection of two 6 mm diameter B-probes separated by 1 cm along the chamber centerline running helium in the LAPD at 1000 G show strong, broadband cross spectral power density from 700 MHz – 2.5 GHz, below the electron cyclotron frequency. The power spectral density collected by a double ridge horn antenna outside the LAPD device looking radially through a nylon viewport contains similar spectral content as that which is detected by either B probe. Ongoing work intends to utilize the COMSOL RF module to study the propagation of the whistler waves from within the plasma to the boundary to develop a new passive, remote diagnostic of the LAPD plasma.