Laboratori Nazionali del Sud

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PS-ESS – Proton Source for the European Spallation Source

The ESS accelerator is deemed to operate at different level of beam power and high reliability; this request has been the main driver for the design of the proton source.

The average macro-pulse current of 62.5 mA (on target) will permit to obtain the maximum beam power of 5 MW at 2 GeV.

The proton source is a compact Microwave Discharge Ion Source (MDIS) similar to the TRIPS and VIS sources already developed at INFN-LNS Catania, and to the SILHI source of CEA Saclay. The beam from the ion source is transported through a Low Energy Beam Transport (LEBT) section to the Radio Frequency Quadrupole (RFQ) and to the next component of the Linear Accelerator.

LNS has a coordinating role for the design and construction of the Normal Conducting Linac, including the proton source and LEBT which is the direct contribution, the Radiofrequency quadrupole (RFQ) developed by CEA, the Medium-Energy Beamline (MEBT) developed by ESS-Bilbao and the Drift Tube Linac as contribution of INFN-LNL. The experience gained by INFN on R&D activities for high-power proton accelerators (HPPA) developed at LNS, LNL and LASA since the '90s, was valuable for such coordination.

The ESS injector design has taken advantage of recent theoretical updates together with the new plasma diagnostics tools developed at INFN-LNS. A maximum proton beam of 74 mA is the goal of the PS-ESS source with a beam stability better than ±3.5% as for pulse to pulse variation and ±2% averaged over a period of 50 μs. The pulse duration is 2.86 ms with 14 Hz repetition rate. A reliability better than 95% is requested for the whole accelerator, thus meaning that the PS-ESS source reliability is expected to be greater than 99%. Emittance is expected to be about 0.25 π-mm-mrad. In June 2016 the plasma was successfully generated and the beam characterization is under way.


Render-view of the MDIS-type (Microwave Discharge Ion Source) proton injector for the European Spallation Source.


Left – Installation (at LNS) of the ESS proton injector, showing source assembly “on board” of the high-voltage platform. Right – light emitted by the PS-ESS beam due to interaction with the residual gas in the low energy beam transport line.


Front view of the ESS injector showing the light emitted by the hydrogen plasma contained inside the copper-made plasma chamber. The light is visible through the 6 mm extraction hole.


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