CERN Accelerating science

 Celebrating the first LHC collisions
 by Alexandra Welsch (UNILIV)

Scenes in the CERN Control Centre (CCC) as stable beams at an energy of 6.5 TeV mark the start of run2 physics at the LHC. Image credit: CERN

On Wednesday, 3rd June, 10.40 am, the LHC operators declared "stable beams" at 6.5 TeV, the signal for the LHC experiments that they can start taking data for the first time in 27 months, after an almost two year shutdown and an intense eight weeks of beam commissioning.  This marks the official start of Run 2 physics at the LHC and the start of a new adventure. 

The LHC was filled with 6 bunches each containing around 100 billion protons. This rate will be progressively increased as the run goes on to 2808 bunches per beam, allowing the LHC to produce up to 1 billion collisions per second.

Collisions seen within the ALICE, ATLAS, CMS and LHCb detectors 
Image credit: CERN

The world’s most powerful accelerator is now providing collisions at the record energy of 13 TeV, almost double the collision energy of its first run. This new energy frontier will allow researchers to probe new boundaries in our understanding of the fundamental structure of matter.

"For the LHC and its detectors to work, everything has to work. And that means I take my hat off to everyone." says CERN Director-General Rolf Heuer." What comes next will, without a doubt, change the way we see the Universe we live in.”



 Bending magnet for SESAME storage ring
by Attilio Milanese (CERN)

The first SESAME dipole on the magnetic measurement bench at ALBA
Image credit: CERN

The CESSAMag project has reached an important milestone with the first unit tests of the bending magnets. 

The bending units (dipoles) are the largest magnets of the SESAME storage ring – each dipole weighs 6.5 tons and is 2.5 m long. These massive components need precise mechanical construction – down to a few tens of microns – to meet the requirements on magnetic field quality and alignment. In addition, the design involves a superposition of dipolar and quadrupolar fields, and an excitation range going into a saturated nonlinear regime. All this made the characterization of the first magnet a critical milestone in the overall project.

CERN is responsible for the design, procurement and test of these 17 dipoles, within the CESSAMag project, largely funded by the EU. Within this framework, CERN has placed a contract with TESLA (UK) for manufacturing the magnets, and is collaborating with ALBA synchrotron (Spain) who provides in kind contribution for carrying out the magnetic measurements.

The test campaign on the first dipole last December fully confirmed the design: the measured magnetic field was in all cases very consistent with the simulations, and in particular the field in the aperture – where eventually the electron beam will circulate - was uniform down to 1∙10-4. This challenging target could only be met with both careful design and proper mechanical assembly by the manufacturer.

The production of the rest of the series is now progressing well in the UK, and 4 more magnets are already in Spain for measurements. In the meantime, the first dipole has been shipped to CERN, where it was used for a full integration check of a SESAME cell, including quadrupoles, sextupoles, the girder support structure and the vacuum chamber.



 The LHC is back in business
by Margarita Synanidi (CERN), Agnes Szeberenyi (CERN)

Reactions in the CERN control centre on the 5th of April
Image credit: CERN

After two years of crucial upgrade work, the world’s largest and most powerful atom smasher is back in operation. On the 5th April, at 10.41am, a proton beam was back in the 27-kilometer ring, followed at 12.27pm by a second beam rotating in the opposite direction. These beams circulated at their injection energy of 450 GeV. The Director General of CERN mentioned “the beam went smoothly through the whole machine. It’s fantastic to see it going so well after two years and such a major overhaul of the LHC”. On 9th April the operations team successfully circulated a beam at 6.5 TeV.

Start-up was delayed for two weeks after a piece of metal caused a short circuit in the safety system around one of the LHC’s superconducting magnets. Engineers cleared the debris on 30 March by vaporizing it with a discharge of current. A similar problem occurred before, at the start of the LHC’s first run, and it was also solved without causing major delays.

On Sunday the protons injected at a relatively low energy to begin with. They will keep working nonstop 24hours per day until they will establish the first stable collision, as explained by the LHC coordinator of operation, Jorg Wenninger.

Over the coming months, engineers hope to gradually increase the beams' energy to 13 trillion electronvolts (double speed what it was during first operating run). They scientists estimate that the particle collisions at an energy of 13 TeV could start as early as June. With that beam energy level raised, it is conceivable that the LHC will capture dark matter, marking a leap forward in our understanding of the universe.

Now starts a new phase of the study of physics, it remains to be seen what the results will be. 



 Laser-driven beamlines: a novel approach towards particle acceleration 
 by Livia Lapadatescu (CERN)

ELI-Beamlines Facility in the Czech Republic
Image credit: ELI

The CRISP project (Cluster of Research Infrastructures for Synergies in Physics), brought together a group of eleven Research Infrastructures with the goal of creating synergies and developing common solutions in four R&D fields: Accelerators, Instruments & Experiments, Detectors & Data Acquisition and IT & Data Management.

In the Accelerators field, one of the activities focused on studying novel compact particle sources including the design of radio-frequency X-band electron sources and of laser-induced secondary particle sources.

Conventional accelerators rely on the use of radio-frequency longitudinal electric fields, which limit the energy gain per unit length, therefore increasing the size of accelerator infrastructures in order to reach higher beam energies.

Laser-plasma accelerators have proven the possibility of producing beams of 1 GeV over 3 cm of acceleration length with unique properties such as ultra-short pulse duration and high peak currents. The uniqueness of laser-driven beamlines will represent an advantage for future accelerator infrastructures, allowing them to reduce their size and cost.  

The CRISP Lasers activity has analysed two kinds of laser-driven beamlines at high energy and at low energy, as well as diagnostic issue for the implementation stage, showing that:

  • Capturing and transporting laser generated electrons with high energy (~8 GeV) has proven to be a challenge since they require strong magnetic fields to handle the beam;
  • By reducing the energy down to 0.5 GeV, an optimized beam line can be produced with a normalized transverse emittance under control.

Moreover for the diagnostics of laser accelerated electron beams, experiments were conducted at the SPARC-LAB facility and constitute a basis for the implementation stage of laser-driven beamlines.

The study conducted by CRISP on laser-driven beamlines will have an impact on the implementation of the ELI-beamlines project (Extreme Light Infrastructure), by proposing solutions for the next generation of particle accelerators.



  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.



  Accelerators: Powering Cutting Edge Research
   by Charlotte Houghton (STFC)

Fig 1 left: Image on the inside cover. 3D model of Diamond Light Source. Image credit: Diamond Light Source
Fig 2 right: Accelerators brochure front cover. Image credit: STFC

What are the practical benefits of particle accelerators? Look out for a brand new brochure, due out this September, which will help accelerator scientists explain the benefits of their work to the general public. By using real-life examples and scenarios everybody can relate to, Accelerators: Powering Cutting Edge Research explores the many areas in which accelerator science has made a positive impact on modern life.

The brochure has been produced by the Science and Technology Facilities Council, the Cockcroft Institute and the Institute of Physics. It has been commissioned to raise public awareness of the benefits of particle accelerators in research, through case studies that answer questions such as:

  • How can we meet our energy needs without adding to greenhouse gas emissions?
  • How will border protection agencies, and the technology they use, continually evolve to face the ever growing threat of terrorist attacks?
  • How can we find new ways of preserving our cultural heritage?

Featuring particle accelerators from around the world, the brochure highlights how accelerators influence our everyday lives by covering topics such as:

  • Energy- solar cells, keeping the lights on at power stations and turning carbon monoxide into fuel.
  • Radiotherapy- treating cancer patients, improving diagnosis and radiotherapy efficiency, and developing new cancer treatments.
  • Medicine- treating HIV, detecting Parkinson’s disease and dealing with diabetes.
  • The environment- storing hydrogen, studying clouds and decontaminating Fukushima.
  • Industry- fuelling the economy, making life sweeter and making aircraft safer.
  • Security- detecting terrorist threats, solving mysterious deaths and fighting counterfeiters.
  • And finally, the natural world and heritage science- conserving our heritage, calculating landslide risks and analysing Roman remains.



  10 years of success for ISIS RFQ
by  Charlotte Houghton

Part of the small team who designed, built, tested, installed and commissioned the ISIS RFQ upgrade.
Image credit: RAL

Earlier this year ISIS, based as the Rutherford Appleton Laboratory in the UK, celebrated ten years of their radio frequency quadrupole accelerator (RFQ), which in 2004, replaced an ancient and unreliable Cockcroft-Walton electrostatic generator pre-injector on ISIS.

Originally part of Nimrod, the predecessor of ISIS, the Cockcroft-Walton set generated a DC voltage of 665,000V. In 2004 the whole system was replaced by three solenoid magnets and a radio frequency quadrupole accelerator; to decrease the machine’s downtime and improve the stability of the beam. Although the concept of RFQs had been around since the 1970s, and had been successfully deployed on high-energy machines in the US, Russia and at CERN, they hadn’t been tested on machines that would run at high duty factor, 24/7 for most of the year.

As there was a clear risk in changing to the RFQ, Alan Letchford, who was part of the ISIS upgrade team, travelled to Frankfurt to meet Professor Schempp. After Alan’s meeting with, at the time, the world’s 4-rod RFQ expert, he travelled back to ISIS to implement what he had learnt. The upgrade team, under Alan’s instruction, built the entire set-up as it would be installed and ran it for a year, comprehensively checking and testing the beam parameters against the design. In the ten years since its installation, it has been an almost invincible system. Apart from expected ancillary part failures the RFQ has accelerated nearly 10 billion beam pulses containing 4 x 1023 protons, and absorbed around 700 gigajoules of RF energy; bringing the reliability of the RFQ to almost 100%.



  ERC Grants Supporting Alternative Accelerator Technologies
by Victor Malka (CNRS-ENSTA-Ecole Polytechnique), Marie Emmanuelle Couprie (SOLEIL), Ralph Assmann (DESY) and Thomas Hind (CERN)

Diagram showing principle of compact Free Electron Laser based on Laser Wakefield Accelerator. 
Image credit: Victor Malka (CNRS-ENSTA-Ecole Polytechnique)

ERC grants are currently being used to support development of alternative accelerator technologies.

The X-Five project, funded by an ERC Grant, is aiming to produce compact, tuneable and ultra bright X ray beams. This is possible thanks to the tremendous progress on manipulating the collective electron motion in plasma mediums, which makes laser plasma accelerators a technology option for new approaches.  

X-ray Free Electron Lasers (XFEL) provide intense coherent femtosecond pulses for multidisciplinary investigations of matter. In parallel, electron beams generated from laser plasma acceleration offer a few femtosecond short bunches with high peak currents. The COXINEL ERC Advanced Grant aims to handle the present energy spread (~1 %) and divergence (mrad) of plasma-generated beams by a proper longitudinal and transverse manipulation in the beam transport to the undulator. It should then be possible to demonstrate FEL amplification, as a qualification of these novel beams.

The goal of the AXSIS grant is to trace and understand chemical and biological processes which take place in just quintillionths of a second, with full atomic detail. The project involves the establishing of a new facility, which will be based at DESY. The attosecond source will be based on a novel, laser-driven particle accelerator technology, which will emit X-ray radiation with much shorter pulses than is possible today. This technology can revolutionise the understanding of structure and function at the atomic level and unravel fundamental processes in chemistry and biology.

  10 years of success for ISIS RFQ
by Thomas Hind (CERN)

Fig1 left. MICE Spectrometer Solenoid Magnet being installed to the beam-line. Image credit: Stephen Kill (RAL)
Fig2 right. Detector systems which EuCARD-2 has been supporting access to. Image credit: Stephen Kill (RAL)

Applications are now being invited for access to the Ionisation Cooling Test Facility (ICTF) based at the Rutherford Appleton Laboratory, including the MICE experiment.

Financial support offered includes provisions for travel and subsistence expenses and access to the beam free of charge, and is designed to aid the presence of researchers at RAL in equipment delivery and data taking and analysis in support of muon cooling experiments, including the MICE experiment. It will also support external users of the beam for tests of particle physics detectors in a low-energy beam and proponents of new cooling experiments to undertake studies, installations and eventually data taking.

A typical experiment is expected to last for about 2 beam-weeks and require the presence of up to 6 external users.

The deadline for applications is the 11th of September 2014, with the applications panel meeting a week later, on the 18th of September.

Read more >> 

  Development of a Fast Ramped Superconducting Dipole Magnet
  by Hans Müller (GSI) and Pasquale Fabbricatore (INFN)

One curved dipole coil of the CRISP project after curing and impregnation of the coil ends.
Image credit: Pasquale Fabbricatore (INFN)

Fast ramped magnets are an essential component of heavy-ion synchrotrons. Future developments ask for higher rigidity of the beams leading to stronger magnetic fields of the magnets and therefore to superconductivity. A superconducting fast ramped dipole magnet is now being developed in frame of the CRISP project.

The magnet is based on the DISCORAP dipole built and tested by INFN as a prototype for the planned SIS300 synchrotron of FAIR in Darmstadt, Germany. The magnet has a main field of 4.5 T and the ramp rate is 1 T/s, which is orders of magnitude higher than any used currently. Its length is about 5 m and the inner diameter of the coil is 100 mm. The magnet is of so-called cos(theta) design, where the shape of the coil determines the field. This requires a high precision in the manufacturing of such a coil and the surrounding collar, which takes the magnetic forces. To increase the acceptance the magnet is wound curved making manufacturing difficult. Another challenge to be addressed is to minimize the AC-losses of the conductor due to ramping. For this, dedicated new superconductors with small NbTi filaments of only about 3 µm diameter had been developed. Another issue to be considered is fatigue, which requires high strength austenitic steel for the coil support.  The collared coil being built now is a first step towards a complete magnet and establishes technologies to be used for further developments in the field of fast ramped superconducting magnets.