The Small Negative Ion Facility (SNIF) at CCFE has been undergoing continuous development and enhancement to both improve operational reliability and increase diagnostic capability. SNIF uses a CW 13.56MHz, 5kW RF driven volume source with a 30kV triode accelerator. Improvement and characterisation work includes: • Installation of a new “L” type RF matching unit, used to calculate the load on the RF generator. • Use of the electron suppressing biased insert as a Langmuir probe under different beam extraction conditions. • Measurement of the hydrogen Fulcher molecular spectrum, used to calculate gas temperature in the source. • Beam optimisation through parameter scans, using copper target plate and visible cameras, with results compared with AXCEL-INP to provide beam current estimate. • Modelling of the beam power density profile on the target plate using ANSYS to estimate beam power and provide another estimate of beam current. This work is described, and has allowed an estimation of the extracted beam current of approximately 6mA (4mA/cm2) at 3.5kW RF power and a source pressure of 0.6Pa.