accelerating-news-arc.web.cern.ch - issue 12

Recent progress of the HiLumi project

Margarita Synanidi — Mon, 01 Dec 2014 14:37:51 +0000

Key highlights towards the High Luminosity LHC era
by Agnes Szeberenyi (CERN)

LHC/ HL-LHC Plan (last update 24.09.2014)
Image credit: HiLumi

More than 110 experts from all over the world gathered in Tsukuba, Japan for the 4th Joint HiLumi LHC/ LARP Annual Meeting between 17 and 21 November 2014, hosted by the High Energy Accelerator Research Organization (KEK).

The event started off with the plenary sessions where management of the collaboration (Dr. Frederick Bordry for CERN, Prof. Yasuhiro Okada for KEK, Dr. Steve Gourlay for USA) gave invited talks. The first plenary session closed with the High Luminosity LHC status updated by Prof Lucio Rossi, HL-LHC Project Leader. Prof Rossi also officially announced the new HL LHC timeline to the collaborators.

One of the highlights of the plenaries was the status update on the Preliminary Design Report, by Dr. Isabel Bejar, as the main deliverable of the project, which will be published soon as a CERN Yellow Report. 3 days focused on the work package parallel sessions, reviewing the progress in design and R&D not only for the EU funded but also non-EU funded work packages.

Key highlights from the Accelerator Physics and Performance activity (WP2) included a refined optics and layout of the high luminosity insertions, an updated impedance model of the LHC and Hl-LHC, and the need of low impedance collimators was confirmed. One of the main results of the IR Magnets activity (WP3) in the past 18 months was a baseline for the layout of the new interaction region. Engineering design and prototyping of most of the magnets has been started, and first tests of near-to-final equipment are expected next year. The Crab Cavities activity (WP4) in this period delivered and tested all 3 prototype crab cavities (4-rod, RFD and DQW) out of which the international design review carried out in in May in BNL made the downselection to proceed with design of the RFD and DQW. A key milestone, to freeze the cavity designs and interfaces, was also met. Highlights from the wrap up talk of the IR Collimation activity (WP5) include the first lay-out for the IR collimation as well as a solid baselines for the collimation upgrade in the dispersion suppressors of around IR7 and IR2. In addition, simulations have continued for advanced collimation layouts in the matching sections of IR1 and IR5, improving significantly the cleaning of physics debris products downstream around the high-luminosity experiments. The Cold Powering activity (WP6) highlights included the world record current of 20kA at 24K in an electrical transmission line consisting of two 20-metre long MgB2 superconducting cables. Other achievements were a conceptual study and preliminary design of a novel concept of cold powering system (cryostat and current leads) connected to the Superconducting Link, definition of cryogenic requirements and flow schemes. The meeting covered also many progress in the other (non-FP7) WPs, especially for machine protection, cryogenics, vacuum, beam instrumentation, etc. A delicate arbitration among the needs of CC test in SPS-LSS4 (Coldex experiment) and the needs of continuing study and tests for e-cloud mitigation by vacuum people was carried out.

The final FP7 HiLumi LHC / LARP Collaboration Meeting will be held between 26-30 October 2015 at CERN. As a contribution to the UNESCO International Year of Light, special events celebrating this occasion will be organized by HL LHC throughout the year. Stay tuned for the latest updates in the CERN Bulletin and CERN website.

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issue 12

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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Modelling the future FCC tunnel

Margarita Synanidi — Tue, 25 Nov 2014 14:48:39 +0000

Modelling the future FCC tunnel
by Johannes Gutleber

The BIM tool dashboard: a user-friendly digital environment with 3D datasets and decision aid tools. Image credit: CERN and ARUP

Arup, a world leader in infrastructure planning and design, has been appointed by CERN to develop an efficient and cost effective planning and decision aid tool for the FCC tunnel engineering and geotechnical studies.

The first phase of the conceptual design study includes the feasibility assessment of an 80 km to 100 km long underground infrastructure for the collider. To support this study, Arup has been working closely with CERN and project partners Géotechnique Appliquée Dériaz S.A. and Amberg Engineering AG. A key element of this stage was the development of a dynamic Web-based BIM (Building Information Modelling) application. This application integrates numerous existing geological data sources, incorporating the geological, tunnelling and particle collider system constraints in a user-friendly digital environment. “To make the decisions, and make sure it interfaces with the existing tunnels, we decided to capture all the data in a 3D environment. We can change the physical parameters of the project in real time – looking at the geology, the size of the ring, the depth of the shafts, and the slope.”, says Matt Sykes, ARUP project director.

The BIM application builds upon an open source web-based geographical information system called ESRI. This approach allows integrating publicly available data on the geography and geology of the region, hydrology information and more data if needed.

The web application can be controlled via a dashboard (see Figure 1) that enables scientists to visualize the effects of parameter changes in real time. The use of an open-source platform ensures that extensions and improvements can be realized easily over a long study and design duration. Participants located all over the world can extract a spreadsheet, amend it and upload the revised version. At later stages, further datasets will be overlaid on top of the existing data, and the current, 2D visualisations would be extended to 3D.

“Several layouts for this new machine are under consideration, with the tunnel circumference ranging from 80 to 100 km. This tool being developed by Arup, will be crucial in the decision making process, to help decide which layout is most feasible”, says John Osborne, Civil Engineer at CERN.

This kind of dynamic tool, integrating numerous different data sets into a single, interactive application can help cutting costs and study times. It can also improve the quality and clarity of decision-basis information of numerous underground civil engineering projects which go beyond the particle accelerator community. Public transport and road projects, which need to consider diverse and ever-changing constraints ranging from technical over cost to environmental, legal and societal are primary candidates for this technology, bringing instantaneous decision aid to the desktop of the project key stakeholders.

Stay tuned for updates on the Future Circular Collider study. Register for the FCC week, the first Annual Meeting of the FCC study to be held between 23-27 March 2015.

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Universities and Laboratories for a common goal

Margarita Synanidi — Tue, 25 Nov 2014 13:48:07 +0000

Universities and Laboratories for a common goal
by Giuliano Franchetti (GSI) and Frank Zimmermann (CERN)

Some of the ULA2014 participants in front of the Institute of Applied Physics, Goethe-University Frankfurt am Main. Image credit: Fips Schneider, IAP, U. Frankfurt

“Universities meet Laboratories” (ULA2014) workshop was a pioneering attempt to bring together representatives of the academic world and of laboratories to resolve differences and discuss synergies for working toward a common goal. Amongst many, this included topics like research evaluation and how to make accelerator science an attractive career choice. The event was attended by over 40 key players from all over Europe.

The workshop revealed a unanimous consensus among the participants from universities across Europe that the field of accelerator physics and technology appears to be often disadvantaged by an inadequate standing in the academic environment.

A very critical observation and issue is that students across European universities do not choose accelerator physics as a study topic and most importantly, many of them are not even aware of accelerator physics as a possible career path. For that reason greater efforts should be made for attracting students in the first stage of their studies. Another issue that was raised is that joint PhD supervision has become a difficult process because the needs of the laboratories do not always match the university research interest.

In terms of research assessments the workshop has evidenced a distinct difference of the research evaluation at universities and laboratories. This difference does not only prevent some laboratory staff from competing for job posts at universities, but it also renders collaboration with laboratories less attractive for the university staff. One reason is that laboratories traditionally disseminate their work in conference proceedings (if at all), while the universities consider only the publications in peer-reviewed journals. Moreover, given the strict metric evaluation the universities apply like the h-factor that disregards other relevant scientific outputs, it occurs that accelerator physics journals are suffering from a low impact factor, which is becoming a discriminating element in the research evaluation.

The workshop has also highlighted the positive impact of three major European and American accelerator schools – CERN Accelerator School (CAS), Joint Universities Accelerator School (JUAS), and US Particle Accelerator School (USPAS) – as well as accelerator training at universities, with Germany leading the way. In Japan the combination of the Graduate University for Advanced Studies (SOKENDAI) and the Inter-University Research Institute Corporation has proven effective. A report on the TIARA survey results showed that many ongoing activities require more training in accelerators. In most of the European countries the elevation of the discipline to the same as level as other more established branches of physics is being pursued by self-organization of the community (e.g. KfB in Germany, CONECTA in Spain), and with the support of the EPS-AG. In general a deeper discussion of these subjects is required. Although, good experience with joint research, and including green field academic accelerator studies, has been reported from the UK.

Many ways to attract more students to the accelerator science were discussed. In particular, Philip Bambade, Accelerator Department Head at LAL Orsay, proposed and highlighted several promising approaches.

A key to attractiveness can be the multi/inter-disciplinary character of accelerator science. Another factor can be that compared to fields like HEP or even nuclear physics, accelerator scientists can be both theorists and experimentalists at the same time.

With the evolution towards smaller, very sophisticated, accelerators, another possible path is a closer connection between the accelerator scientists and the users, through approaches integrating these two communities.

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First Energy Efficient RF Sources Workshop

Margarita Synanidi — Tue, 25 Nov 2014 13:29:01 +0000

First Energy Efficient RF Sources Workshop
by Erk Jensen (CERN), Charlotte Houghton (STFC)

Attendees of the EnEfficient RF Workshop at the Cockcroft Institute, June 2014.
Image credit: Cockcroft Institute

The first Energy Efficient RF Sources workshop, supported by EuCARD-2, took place in June 2014 at the Cockcroft institute in the UK. Over 40 delegates and 18 speakers were part of the two day workshop which discussed state-of-the-art RF sources.

In the early days of particle accelerators, RF experts concentrated their design work on cavities and amplifiers with large acceleration in mind. Later, when the beam currents in accelerators increased, the focus of their ingenuity shifted towards coping with beam loading, better beam stability and increasing beam power. With demands for ever increasing beam energy and power, the overall energy consumption has now clearly become a major concern; large future particle accelerators must remain economically and ecologically sustainable and acceptable, so the overall power conversion efficiency has taken centre stage. Optimization of this efficiency could reduce both power consumption and wasted energy, both relevant for the society at large. At this Daresbury workshop, these concerns were discussed among international experts, and many novel and interesting solutions to make better RF systems were proposed.

Workshop highlights included, pioneering ideas proposed to substantially increase the power conversion efficiency of high power klystrons. Klystrons are Multi-Megawatt RF power amplifiers at the heart of many particle accelerators. While present-day klystrons are limited to efficiencies below 70%, the proposed improvements may push efficiencies to 90%. Much attention was also devoted to high power solid-state amplifiers. These amplifiers are still limited to much smaller power limits than vacuum electronic devices, but the trend over the last decade is very promising; and it is predicted they will become important in the future. Inductive output tubes (IOT’s), combine the advantages of grid tubes, this allows them to run without DC current, i.e. at lower power consumption. With the advantages of high frequency klystrons, IOT’s do not yet reach the power levels needed in accelerators, but promise better efficiency. This has encouraged recent results and plans for further research.

The two-day workshop, which is part of the EnEfficient EuCARD-2 work package, addressed the above interesting and promising topics and more. The workshop included a tour of the Versatile Electron Linear Accelerator (VELA), located at the Daresbury Laboratory.

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New approach for characterization of radio frequency properties

Margarita Synanidi — Tue, 25 Nov 2014 12:37:14 +0000

New approach to characterize RF properties in complex structures
by Margarita Synanidi (CERN) with Thomas Flisgen, Johann Heller, and Ursula van Rienen (Uni Rostock)

Magnitude of the electric field of a higher order multi-cavity eigenmode in a chain of eight superconducting 3.9 GHz cavities (zoom at the bottom), which are connected via beam-pipes and bellows (zoom at the top). Image credit: UniRostock

The computation of RF properties of large and complex accelerating structures is a challenging and important task for the design and operation of particle accelerators. A new method, developed under EuCARD-2 WP12 allows for the characterization of radio frequency properties such as field distributions, quality factors or impedance/scattering parameters of large and complex structures.

Until now direct approaches that determine these properties required expensive supercomputers due to the vast number of degrees of freedom arising from the direct discretization of the complex structure. Moreover, results delivered by direct methods could be unsatisfying due to round-off errors or numerical instabilities arising from ill-conditioned system matrices. The computational demand of the direct computations of the full chain can be avoided by decomposing the structure into single elements. In a next step, the individual segments are described by means of reduced order state-space models, which are combined to a reduced order model of the entire structure. The approach is referred to as state-space concatenations (SSC) and enables the computation of radio frequencies properties of complex structures by using standard workstation computers, rather than supercomputers.

The novelty of this approach is the description of the individual segments by means of state-space models. The state-space models provide a rigorous description of the radio frequency properties of the segments, in particular, they enable to reconstruct field distributions. Computations or radio frequency properties are not only relevant for cavities, but are also performed in other studies, e.g. in case of modelling bunch compressors. The SSC approach is not restricted to a special topology or particle accelerator applications and can be used to other similar calculations as well to avoid the usage of expensive cluster computers.

The next step incorporates the generation of detailed computer models of chains of four and eight third harmonic cavities, which are accommodated in FLASH or the XFEL. Previous studies have shown that the consideration of the entire chain is required rather than restricting to individual cavities. It is planned to generate a modal compendium (list of eigenmodes and their properties) for these structures based on the detailed computer models.

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issue 12

Accelerator quality HTS dipole magnet demonstrator design

Margarita Synanidi — Tue, 25 Nov 2014 10:54:57 +0000

Accelerator quality HTS dipole magnet demonstrator design
by Agnes Szeberenyi (CERN), Glyn Kirby (CERN)

Figure 1: Aligned block development HTS magnets, (bottom right) Feather-M0 quench detection development coil, (top left) Feather-M2 the EuCARD-2 five Tesla standalone approaching accelerator field quality insert magnet. Image credit: CERN

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 Future Magnets activity is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. A new coil layout concept, named aligned block was developed which can result in 2.3 times less conductor that leads to more cost efficiency than with the conventional Cosine Theta design using the same conductor.

The collaboration between CEA-CERN-KIT-TUT-INFN-LNBL aims to develop a High Temperature Superconductor (HTS) accelerator quality magnet demonstrator, capable of producing a 5 T central magnetic field in standalone configuration. Both REBCO and BSCCO conductors are being considered. The BSCCO design is part of the US-BSCCO programme based on Canted Cosine-Theta (CCT) geometry. The European collaboration is focusing on REBCO coated conductors, based on aligned block and cosine-theta.

At CERN scientists are developing the align block concept, named Feather-M0/2 (FeaTHeR - Five Tesla HTS Research, see Figure 1). Feather-M0 is used to develop coil winding and quench detection, while Feather-M2 will produce 5 Tesla standalone and between 17 and 20 Tesla, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The main objective with the aligned block design is to maintain a close alignment of the magnetic field with the cable throughout the entire coil assembly. This layout makes optimal use of the anisotropy of the REBCO coated conductor (Figure 2). The design, although in its initial phase, addresses most issues related to the use of Roebel cable for a dipole cable. In a second step it is foreseen to approach a 17 T central field when inserted in a 13T high field magnet. Model coils are under construction, cables and magnet designs are progressing. Models will test dynamic field quality and confirm if it is possible to detect and protect the REBCO high current density present in the aligned Roebel cable design.

Figure 2:In the layouts the magnetic field angle is highest at the edges of the cable causing a large variation of the critical current over its width. Image credit: CERN

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issue 12

Powering strategy of SESAME magnets

Margarita Synanidi — Tue, 25 Nov 2014 10:05:59 +0000

Powering strategy of SESAME magnets
by Livia Lapadatescu, Agnes Szeberenyi with Miguel Cerqueira Bastos (CERN)

The power converter team with the first of 10 pallets that arrived at CERN with all the quadrupole power supplies (focusing and defocusing) and with the focusing sextupole power supplies. Credits: CERN and SESAME

The magnet system with its power supplies are a major component of the SESAME light source main storage ring. The main objective of the power supplies activity under the collaboration between CERN, European Commission and SESAME is to define the powering strategy and deliver the power converters and corresponding control elements to SESAME. This includes specifications, procurement and testing of all power and control components.

In the last three months, the Magnet Power Supplies activity of the CESSAMag project has seen some major milestones achieved. After reviewing the typical powering requirements of modern light sources and understanding the main differences with respect to high-energy particle accelerators, the CERN and SESAME team devised a powering strategy focused on providing flexibility and performance whilst minimizing machine downtime and facilitating maintenance procedures. This strategy was approved by both CERN and SESAME Technical Committees. It relies on the use of an existing, “proven in use”, control system to run commercial power supplies, which in the case of the quadrupoles are off-the-shelf products. With this strategy SESAME has full control over the performance of the current loop and benefits from the standardization of the control electronics. The use of commercial power supplies, easily and quickly replaceable, also improves maintenance and spare management.

The interface and DAC board, developed by the power converter team. Credits: CERN and SESAME

The control solution described above led to the decision of using the latest power supply controller from the Paul Scherrer Institute (PSI). The CESSAMag team is the first to integrate the new generation of the PSI controller in the powering system of another light source.

The powering of the magnets in the SESAME main storage ring will be done in series for the dipole and sextupole magnets and individually for the other magnet types. The individual powering of quadrupoles was not originally foreseen and it was adopted to achieve increased flexibility, following discussions with experts from other light sources. The 8 magnet types (dipole, focusing quadrupole, defocusing quadrupole, focusing sextupole, defocusing sextupole, V-correctors, H-correctors, skew quads) require 6 different types of power supplies.

All the power supplies for the quadrupole and corrector magnets as well as the PSI electronics for the control system and the gateways have been delivered to CERN. Testing of all these elements will now start at CERN and they will be delivered and integrated into the SESAME system mid-2015.

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