According to the invention, an apparatus to characterize leaks in a fluid storage container is disclosed. The method includes generating a Continuous Tone Image with all pixel values same as a first gray level, generating an initial Half Tone Image with all pixel values equal to minimum absorptance level and computing a change in pixel error for a first pixel. In one embodiment, a method of cleaning a processing chamber includes supplying a cleaning gas mixture into a processing chamber, applying a RF bias power of about 2 MHz or lower to a substrate support assembly disposed in the processing chamber to form a plasma in the cleaning gas mixture in the processing chamber, and removing deposition residuals from the processing chamber. The first attenuation path is preferably variable. Movement of the hydraulic piston engages the friction pads with the respective rotor sides to retard the wheel.