Ultrasound uses high frequency sound waves to achieve this, typically in the region of 0.1 - 35 MHz. In Immersion testing the object is immersed in water, the water acts as the couplant between the source of ultrasound and the material. D & FD (Divertor and First Wall Technology Development Division) uses two Ultrasonic Testing Facilities. Omniscan MX (Manufactured by Olympus) is used as Contact Ultrasonic Testing and this system combines with automated immersion system in which the ultrasonic probe is manipulated by a motion controller. Immersion testing offers the following advantages compared with the contact method: -
" Water coupling eliminates the variability associated with contact coupling.
" High frequencies, up to 35 MHz can be used.
" High resolution Scan up to 0.1mm step for C-scan imaging.
" Scanning Area 900mm x 700mm x 700mm.
" 300mm Dia. Turntable Rotating Chuck
" A 6-axis manipulator for maneuvering the probe head.
" Horizontal IRIS to inspect PFC Monoblock assembly
The system shown in Figures has high frequency capability (25MHz), enabling extremely fine focusing. The pulser/receiver operate under the control of Tomoview software. This collects the entire waveform and enables the data to be presented in a variety of views (plan, cross-section, etc.). The probe manipulator has 2 degrees of freedom. Horizontal IRIS (Internal Rotary Inspection System) has been developed and which is being used to inspect a PFC Mock-up assembly of length 500mm to detect bonding defects. The tank can accommodate components that are up to 0.7m x 0.9m.
The system is equipped with a dedicated ultrasonic data analysis system (Tomoview), together with integral scanner controllers designed by Trotix Ltd. (IIT-Chennai).
A-Scan, B-scan and C-Scan outputs showing Artificial Defects in PFC