BNL, Upton, Long Island, New York
A residual gas x-ray beam position monitor (RGXBPM) was developed for PETRA-III storage ring. This type of x-ray beam position monitors (XBMP) tend to overcome some deficiencies of the blade type XBPMs, which are currently employed at the third generation synchrotron facilities as "white" undulator beam XBPMs. While blade XBPMs provide micron-accuracy resolution, the signal depends on the undulator gap and is also affected by stray radiation from bending magnets and focusing optics. The residual gas XBPM detects position of the centre of gravity of the undulator radiation; it has no elements that are hit by the x-ray beam, and complies with the windowless concept of the PETRA-III beamlines. Residual gas beam profile monitors were first developed to provide beam profile measurements at charged particles accelerators. The spatial resolution of RGXBPM was substantially improved in order to comply with the requirements at the PETRA III storage ring. Due to limited space, a thorough electrostatic optimization of RGXBPM was needed to achieve required electrical field quality. Test results obtained at the ESRF and commissioning of the RGXBPMs at PETRA-III will be reported.
