The accurate adjustment of the filament current has a significant influence on the filament lifetime of an open microfocus X-ray tube. Over time, the thickness of the tungsten filament is declining which increases the resistance of the wire. The control software of the X-ray tube must adapt the filament current to these changes periodically.
Gulmay Ltd. has developed a new patented resonant filament supply (AC resonant filament, ACRF) for its UC product line that allows a much higher accuracy in controlling and monitoring the filament current.
The new closed loop output current regulation design leads to more stable filament current behaviour, with excellent linearity across the entire filament operating range. Significant reductions in mains or other low frequency noise associated with the auxiliary supply is achieved, while a novel primary current sense circuit allows for a very accurate output current monitor without the need for sensing at the filament itself, or within the HV assembly.
To validate the actual impact of the new filament supply, X-RAY WorX performed a dynamic load test using a microfocus tube of type XWT-225-THE Plus. The test included periodic operation at voltage of 160 kV and 48 W target power for ten minutes followed by a 4-minute period with X-ray switched off. Furthermore, an automatic filament adjustment was performed once per hour.
The first set of tests with the previous version of the filament supply yielded an average lifetime of 310 hours. The second set of tests with the ACRF resulted in an average lifetime of 541 hours. Filament lifetime has increased by more than 70% in our laboratory tests.
X-RAY WorX will introduce the ACRF filament supply for all product lines. For updates of existing high voltage generators contact your X-RAY WorX service department.
Operating from locations in the U.K., U.S.A., Germany, and China, Gulmay is a leading manufacturer of high voltage generators and controllers for industrial applications. With 40 years’ experience in the development of microfocus X-ray generators, Gulmay continues to develop innovative new products which bring significant benefits to our OEM partners globally.