CERN’s Linac4 cesiated surface H$^{-}$ source

Linac4 cesiated surface H$^{-}$ sources are routinely operated for the commissioning of the CERN’s Linac4 and on an ion source test stand. Stable current of 40-50 mA are achieved but the transmission through the LEBT of 80% was below expectations and triggered additional beam simulation and characterization. The H$^{-}$ beam profile is not Gaussian and emittance measurements are larger than simulation. The status of ongoing development work is described; 36 mA H$^{-}$ and 20 mA D$^{-}$ beams were produced with a 5.5 mm aperture cesiated surface ion source. The emittances measured at the test stand are presented. During a preliminary test, the Linac4 proton source delivered a total beam intensity of 70 mA (p, H2$^{+}$, H3$^{+}$).