[en] Spatial variations of plasma parameters were measured in a large, inductively coupled plasma (ICP) chamber (diameter: 610 mm) by using a fast scanning probe (FSP), which could scan a length of 100 cm at a speed of 0.8 m/sec. The plasma parameters were measured by using single, triple, and emissive probes installed at the tip of FSP. A new modified diffusion model was introduced to analyze the spatial variations of the normalized density since the variable mobility model cannot explain the current measured data. Inclusion of ion thermal motion gives more reasonable results than the variable mobility model