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The ESRF EBS storage ring has since spring 2022 among its electron beam diagnostics two independent units of vertical Halo-monitors. The principle and the components of this unique diagnostic will be explained in details. It uses the available X-rays in a non-used Front-End, emitted from a 0.57 T standard dipole magnet in the EBS lattice. This instrument measures the so-called "far-away" Halo level, i.e. in a zone of roughly 1-3 mm away from the beam centre, which represents 200-600 times the electron’s vertical beam-size, supposedly Gaussian, of 5 um. It is measured, and expressed quantitively in picoAmp beam current, at 1 Hz rate. Both units are yielding very satisfying and well-correlated results that will be presented in details, and in relation with studies on the electron beam and the accelerator components like variation of current, filling-patterns, vertical emittance, quality of the vacuum, settings of the undulator gaps, collimators, scrapers etc. and also in direct correlation with measurements of our 128 beamloss detectors and beam lifetime.
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