A soft X-ray/XUV diode (XRD) is a powerful diagnostic tool for system alignment, among others, in capillary discharge experiments, which generate directional soft x-ray radiation, eventually a laser pulse. In our experimental devices (CAPEX and CAPEX-U) we usually used PIN diode or vacuum photodiode (one-segment). These diagnostics are not very suitable, mainly because many shots (more than 50) are necessary to find the optical axis. During last year we have designed and manufactured a four-segment soft X-ray vacuum diode with a golden photocathode, which detects the soft X-ray radiation emitted in the axial direction. This new diagnostic tool is capable to locate the axis of soft X-ray laser in a few capillary shots (less than 10). The description and the experimental measurement of the four-segment soft X-ray vacuum diode are a subject of this paper.