Particle Physics Division

The MEBT

Situated between the existing RFQ and future cryomodules, the roles of the MEBT (Medium Energy Beam Transport) are extremely varied, which explains the diversity of the equipment that makes it up. Thus it must be able to:

• Guide and adapt the beam coming from the RFQ to the superconducting accelerative structures,
• Measure beam characteristics: current, position, phase, energy, transverse and temporal profiles, emittances,
• Clean the beam if necessary: adjustable slits, bunch selector,
• Minimize the residual gas flow to the superconducting part.

It therefore welcomes in particular:

• 3 RF cavities, bunching the beam,
• 8 magnetic quadrupoles, guiding and focusing the beam,
• 4 BPMs (Beam Position Monitor), measuring the position and phase of the beam,
• 2 diagnostic boxes, containing beam profile and emittance measurement diagnostics,
• 3 boxes for cleaning slits,
• A vacuum system including 5 turbo molecular pumps and 2 primary pumps, 4 valves on the beam axis,
• Water, nitrogen and compressed air distribution systems,
• Control cabinets for all the elements of the line.

The assembly is 5 meters long and weighs about 3.5 tons.

Integration & testing

From the beginning of the line design, we decided to carry out the integration in Saclay as well as a partial test of the vacuum, cooling, mechanical positioning and control (on the METS: MEBT Test Stand). The objective was to reduce as much as possible the hazards in Soreq and to limit the interventions on site by transporting the already assembled line. This choice imposed from the design stage a mechanical design capable of withstanding such transport.

It should also be noted that the RF cavities of the rebuncher type, the result of a Ganil design, were the subject of particular attention. Thus, a dedicated test bench, the RBTS (Rebuncher Test Stand), allowed RF power testing of the 3 cavities before their final integration on the MEBT.

Thus during a very short period, from November 2019 to August 2020, including a moment of lock down, within the METS, IRFU's teams performed outstanding feats, carrying out all the mechanical integration of the various MEBT components, alignment, cabling between the empty cabinet and the line components, pumping, testing the quadrupole power cabinet  and the vacuum system including the main automatic procedures, as well as lifting and rolling tests. All of these operations allowed the successful validation of the design of the MEBT in Saclay.

Packed in the last week of July and delivered in the first week of August, the MEBT is now installed at its final position in Soreq and is to be progressively commissioned with the assistance of the remote IRFU teams for the time being.