CERN’s Linac4 cesiated surface H− source

Abstract

Abstract.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 + ).

Deviation of H− beam extraction simulation model

“…The CERNs Linac4 radiofrequency ion source is a state-of-the-art cesiated ion source for production of 45 keV H − ions with an intended purpose of being the future main injector for CERNs accelerator chain. The source aims to produce 50 mA, 600 μs pulses of H − with normalized rms emittance of 0.25 mm mrad or less [10]. The ion source extraction and electron dumping has gone through several revisions during the development [11,12].…”

Experimental benchmark of the NINJA code for application to the Linac4 H−ion source plasma

“…However, diagnostic access to plasma parameters especially in the region close to the extraction aperture is challenging, as the design of ion sources applied at accelerators is very compact. Furthermore, some diagnostic methods like Langmuir probes have problems withstanding the strong heat loads occurring on very short time scales [13]. Optical emission spectroscopy (OES) can ideally be applied at ion sources as only a small window to the plasma chamber is required but the evaluations only yield line-of-sight integrated results.…”

Ion beam intensity and phase space measurement techniques for ion sources

“…In the development work of CERN's Linac4 H − ion source, for example, such a slit-grid scanner is used to provide a 3.75 mrad divergence resolution and a span of ±86 mrad in one beam pulse by using a 47 wire grid with a 0.75 mm spacing, 200 mm away from the slit. 35,39 The resolution can be doubled by moving the grid by half the wire spacing between two pulses and thus spending double the time for the scan. The scan speed gained with a grid system compared to a single wire or slit is very significant as the Linac4 ion source is operated only with a 1 Hz repetition rate.…”