Laboratori Nazionali del Sud

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Research

ESS

The Proton injector for the European Spallation Source LINAC

figure1 ess r The European Spallation Source (ESS) is a European Research Infrastructure Consortium (ERIC) established with the mission to build a leading multi-disciplinary neutron research facility.
The international collaboration started the design in 2012 while the construction started in 2014 in Lund, in the southern part of Sweden. In 2023 the worlds most powerful linac accelerator and neutron source ever built today will be available for users. The ESS goal is enabling scientific breakthroughs in research related to materials, energy, health and the environment, and addressing some of the most important societal challenges of our time.

The INFN-Laboratori Nazionali del Sud (LNS) has contributed to the realization of the ESS LINAC with the design and construction of the proton source, named PS-ESS, and of the Low Energy Beam Transport (LEBT).

 

The core of the Proton Source

figure2 ess rThe core of the PS-ESS source is a flexible magnetic system consists of three coils that can generate a wide range of magnetic field profiles. The microwave power is provided by a 2 kW magnetron operating at 2.45 GHz. An automating tuning unit and a custom made matching transformer was designed to ensure the maximum power transfer to the plasma. A compact tetrode extraction system was optimized for 75 kV operation, minimization of sparks risk and easy maintenance.
A custom control system was designed to minimize the human survey for stable beam production and the study of different source configurations.

 

The Low Energy Beam Transport (LEBT)

figure3 ess rThe LEBT was designed to minimize the emittance growth, enable a complete beam characterization and change of beam size and time duration. Two identical solenoids with integrated magnetic steerers take care of beam matching and alignment with the following part of the accelerator. Six-blade diaphragm can change the size and precisely control the amount of transferred beam current. An electrostatic chopper was designed to speed up the rise and fall time of the beam pulse, taking care also of space-charge compensation and beam power dissipation problems. In a total LEBT length of 2 meters two emittance measurement unit, a faraday cup, a non-invasive beam profile measurement and a doppler shift measurement unit are also integrated. The LEBT ends with a collimator able to sustain up to 10 kW beam power during chopping operation, act as vacuum breaker between the LEBT (10-5 mBar) and the RFQ (10-7 mBar), and able to measure the amount and position of the transmitted beam.

 

The commissioning and the journey to Sweden

figure4 ess rThe reached performance during the commissioning of the source was above the request of the ESS project. The source can produce stable beam pulses ranging from 35 to 120 mA. At the end of the LEBT we can produce the requested amount of proton beam pulse (70 mA most used value in ESS accelerator) with rise and fall time of a five hundred nanoseconds, intra-pulse stability better than ±2% and pulse to pulse stability better than ±3.5%.
After the successful commissioning at INFN-LNS, in early November 2017, the Ion Source and LEBT were disassembled, packaged and transferred to Lund. An appropriate transfer was designed, and no damage occurred during 8 days and 2.925 km journey. The unpacking and reassembly were carried out by the LNS-staff in collaboration with ESS agents in only 14 working days.

figure5 ess r

 

 

 

ess inauguration

November 15th, 2018: Source inauguration by the President of the Italian Republic S. Mattarella and the Sweden Royal Family

figure7 ess r

The PS-ESS source and LEBT during the assembly in the ESS accelerator tunnel in LUND



Bibliography

[2018] L. Celona et al., Ion Source and Low Energy Beam Transport Line Final Commissioning Step and Transfer from INFN to ESS, in Proceedings of the 9th International Particle Accelerator Conference, Vancouver, Canada, 29 April4 May 2018, pp. 17121714
[2018] A. Caruso et al., Experimental performance of the chopper for the ESS LINAC, 2018 J. Phys.: Conf. Ser. 1067 042015
[2017] L. Neri, et al., High level control system code with automatic parametric characterization capabilities, Proc. ICALEPS 2017 Barcelona (Spain) paper THPHA035.
[2017] L. Neri et al., Beam Commissioning of the High Intensity Proton Source Developed at INFN-LNS for the European Spallation Source, in Proceedings of the 8th International Particle Accelerator Conference, Copenhagen, Denmark, 1419 May 2017, pp. 25302532
[2016] L. Celona et al., The proton source for the (PS-ESS): installation and commissioning at INFN-LNS, in Proceedings of ECRIS2016, Busan, Korea
[2016] G. Gallo et al., Innovative mechanical solution for the design of the high intensity proton injector for the European Spallation Source, in Proceedings of ECRIS2016, Busan, Korea
[2014] L. Celona et al., The proton injector for the European Spallation Source, in Proceedings of LINAC2014, Geneva, Switzerland
[2012] L. Neri et al., The ESS low energy beam transport line design, Proc. LINAC2012 Tel-Aviv (Israel) paper THPB028 pp 912914.
[2012] L. Celona et al., Design issues of the proton source for the ESS facility, Proc. LINAC2012 Tel-Aviv (Israel) paper THPB076 pp 10081010.
[2011] L. Celona et al., High intensity proton source and LEBT for the European spallation source, AIP Conference Proceedings 2011, 020019 (2018)

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