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LINAC4 reaches target energy of 160 MeV

Panagiotis Charitos — Mon, 06 Mar 2017 12:46:26 +0000

LINAC4 reaches target energy of 160 MeV
by Jennifer Toes & Maurizio Vretenar (CERN)

Installation of the CCDTL structures of LINAC4, built and assembled in Russia (Image: CERN CDS)

CERN’s new linear accelerator (LINAC4) reached its final energy goal of 160 MeV in October 2016. The new LINAC4 will double the brightness of the beam in the PS Booster (PSB), by injecting H- beams at a higher energy than the present 50 MeV of LINAC2. This is the first step for the increase of the LHC luminosity that will be possible after completion of the LIU (LHC Injectors Upgrade) and HL-LHC (High-Luminosity LHC) projects.

Approved in 2007, LINAC4 is the realization of nearly 10 years of work. The project has involved almost all CERN Departments and services, and included substantial in-kind contributions from Russia, Poland, Spain, Italy and India.

This ultimate achievement comes after reaching 107 MeV energy in July 2016. The commissioning with beam took place in stages of increasing energy; from 3MeV in October 2013, to 12 MeV in August 2014, 50 MeV in November 2015, 100 MeV in July 2016, before ultimately bringing it up to the final goal of 160 MeV in October with the commissioning of 11 new accelerating cavities.

After optimizing the beam parameters and testing with the new high-energy beam the H- stripping equipment for the PSB, LINAC4 will begin a yearlong testing period in spring 2017. This phase will help to improve the accelerator’s reliability in preparation for taking over from LINAC2 as the first element of the LHC injection chain.

The final phase will include connecting the linac to the PSB; requiring extensive modifications to both the beam lines and to the PSB itself. This will take place during the second Long Shutdown (LS2) of the CERN accelerator complex in 2019-20.

“This achievement is a great success for all the people that contributed to the project, at CERN and outside,” said Maurizio Vretenar, LINAC4 Project Leader.

He continued: “All accelerating sections and components of the new linac performed remarkably well from the very beginning, showing the quality of the design, of the realisation and of the installation.”

Although CERN was responsible for the construction of the LINAC4, the R&D phase which preceded it was performed in close collaboration with six other laboratories as part of the first Integrating Activity project for accelerators; CARE (Coordinated Accelerator Research in Europe), which operated from 2004 to 2008.

“The collaborative environment and the support provided by this European project allowed us to go through the critical R&D phase refining the project at the level where it can be approved for construction, and helped strengthen the collaborations that evolved into our crucial in-kind contributions,” said Vretenar.

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issue 19

LINAC4 ready to go up in energy

Panagiotis Charitos — Thu, 24 Mar 2016 16:41:35 +0000

LINAC4 ready to go up in energy
By Jennifer Toes (CERN)

The DTL section of the LINAC4 (Image: CERN)

The LINAC4 linear accelerator has recently achieved beam commissioning of 50MeV and is now almost ready for the next step of increasing the beam energy even further up to 100MeV. This project is part of the LHC Injectors Upgrade (LIU) required for the needs of the High Luminosity LHC (HL-LHC).

LINAC4 aims to replace the ageing LINAC2 linear accelerator, going from the present 50 MeV proton beam injection into the Proton Synchrotron Booster (PSB), the first ring in the CERN accelerator chain, to a modern H- ion beam injection at 160 MeV, more the three times the Linac2 energy.

“CERN is one of the few laboratories in the world that has not yet implemented H- injection” said Alessandra Lombardi, who is responsible for the beam commissioning of the LINAC4. Injecting H- at a higher energy results in a smaller emittance in the PSB.

Following the successful commissioning of the three newly designed Drift Tube Linac (DTL) tanks in November 2015, the team began its preparations for the installation of two key accelerating sectors: the Cell Coupled Drift Tube Linac (CCDTL) and PI-Mode Structures (PIMS).

Built in Russia by a collaboration of CERN with two Russian laboratories, VNIITF in Snezinsk and BINP in Novossibirsk, the CCDTL is the next structure to be conditioned and commissioned with beam in the LINAC4.

“The CERN CCDTL is composed of 7 modules of 3 tanklets each and it brings the energy of the beam from 50 to 100MeV” said Lombardi.

The main advantage of CCDTLs over standard DTLs is that their quadrupoles are external and therefore more accessible. The accessibility of these magnets makes the construction and alignment process much more straight forward.

The PIMS was constructed as part of a CERN-Poland (NCBJ Swierk) collaboration with contributions from FZ Jülich (Germany). The PIMS was assembled and tuned at CERN will bring up the beam energy from 100MeV to its final goal of 160MeV. It is composed of 12 modules for a total length of about 25m.

Currently, the installation and conditioning of all CCDTL tanks and of the first PIMS is being carried out before beam commissioning begins on April 11^th 2016. The commissioning of the remaining PIMS tanks expected to follow in October will allow reaching the final beam energy.

Scheduled to become operational by 2020, the LINAC4 is a crucial step towards the increase in the LHC luminosity that will allow CERN to remain at the pinnacle of high energy physics research.

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issue 16

Novel permanent magnet quadrupoles for LINAC4

Margarita Synanidi — Wed, 26 Nov 2014 14:55:07 +0000

Novel permanent magnet quadrupoles for LINAC4
by Alessandra Lombardi (CERN)

PMQ for tank2 , provided by Elytt, 60 mm in diameter and 80 mm in length. Image credit: CERN

The Drift Tube Linac (DTL) of LINAC4 is to be equipped with Permanent Magnet Quadrupoles (PMQ). The DTL is a 352MHz Radio Frequency Structure composed of 3 tanks that accelerates the beam from 3 MeV to 50MeV. In LINAC2 Electromagnetic Quadrupoles are used presently. Amongst the main reasons to use PMQs in LINAC 4 were compactness, cost efficiency considerations and simplification of the operation.

Permanent magnets have been chosen as the best practical way to provide the required high gradient within the small volume available inside the high-frequency accelerating structure. The PMQs are electron-beam welded inside the copper drift tubes and alignment is provided by the outer cylindrical surface and radial pins. Additional advantages include simple fixed-optics operation and cost savings as power supplies and cables are not needed. This choice relied on the correctness of the beam dynamics calculations as the focusing inside the Drift Tube Linac cannot be changed once the quadrupoles are produced.

The procurement of the 113 PMQs started in 2009. It was split amongst two companies: ASTER(USA) and Elytt (Spain) to avoid single-source and especially with the aim of bringing the PMQs technology to European firms. The quadrupoless of tank1, which were needed first, were ordered from ASTER; whereas the one of tank2-3, needed later in time were ordered from Elytt. At the same time a small quantity of quadrupoles was made in house with the purpose of demonstrating the PMQ technology internally, the goal of which was fully achieved. CERN has acted as a catalyser to bring the PMQs technology to Europe in a continuous collaborative spirit with the selected companies. As a result of this success, it was decided to equip the inter-tanks of the next accelerating structure (a Cell Coupled Drift Tube LINAC (CCDTL), up to 100MeV) with PMQs as well.

PMQ for tank1 , provided by ASTER, 60 mm in diameter and 45 mm in length. Image credit: CERN

All the quadrupoles have been received and accepted after magnetic measurements at CERN by November 2012. In August 2014 the first beam accelerated through the tank1 to 12 MeV showed excellent success with no losses along the structure thanks-also- to the perfect focusing of the PMQs.

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