accelerating-news-arc.web.cern.ch - EuCARD

“TLEP” - Circular Higgs Factory and a Long-Term Perspective for High Energy Physics

Sabrina El Yacoubi — Fri, 28 Nov 2014 08:24:49 +0000

“TLEP” - Circular Higgs Factory and a Long-Term Perspective for High Energy Physics
by Frank Zimmermann (CERN)

A long term strategy for particle physics. The succession of TLEP & VHE-LHC could provide more than 50 years of e+e-, pp, AA, ep/A physics at highest conceivable energies. The sequence LEP3 & HE-LHC represents a less ambitious, but lower-energy alternative.s. Image credit: TLEP.

Following the first EuCARD “LEP3 Day” on 18 June 2012 (see article ‘Circulating ideas about a new Higgs factory’ inAccelerating News issue 3), which revealed a great interest in a circular-collider “Higgs factory”, EuCARD Work Package 4,AccNet, has been organizing several workshops discussing the key ingredients, the physics potential, experimental detector concepts, and synergies with other projects of such a facility.

Emphasis has shifted from LEP3, a machine installed in the 27-km LHC tunnel originally proposed, to TLEP, an electron-positron collider in a new 80 or 100-km long ring tunnel. Advantages are manifold: TLEP construction would be fully decoupled from LHC/HL-LHC operation. TLEP could achieve up to 5 times higher luminosity than LEP3, promising a precision for Higgs coupling measurements much better than any other planned or proposed machine. Such precision is needed to discover physics beyond the standard model at energies above 1 TeV. In addition, TLEP could possibly provide the infrastructure (tunnel, cryogenics, injector-ring magnets, detectors) for a future 100-TeV proton-proton collider in the same tunnel – the “Very High Energy LHC” or “VHE-LHC” –, paving a path towards extremely high hadron collision energies, while also allowing for highest-energy electron-proton collisions.

Presently a TLEP conceptual design study is being set up aiming at delivering a design report by 2014/2015.

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issue 5

Diagnostics based on Higher order mode port signals

Sabrina El Yacoubi — Fri, 28 Nov 2014 08:16:23 +0000

Diagnostics based on Higher order mode port signals
by Ursula van Rienen, Thomas Flisgen, Tomasz Galek (Universität Rostock)

"Parasitical" use of HOM couplers. Image credit: Universitat Rostock

Higher order mode (HOM) couplers are a crucial part of many superconducting cavities since unwanted modes, which are excited by the beam, need to be damped effectively. EuCARD WP10 task 5 is predominantly dealing with studies on diagnostics based on HOM port signals. This task is carried out jointly with the teams around Roger Jones (University of Manchester, speaker) and Nicoleta Baboi (DESY).

Monitoring the HOM port signals as a by-product of the HOM damping offers the possibility to determine the transversal offset, the total charge of the bunch, etc. with little additional hardware.

One major concern of the ongoing studies is to predict the theoretical accuracy of the diagnostic system in the context of uncertainties such as perturbations of the cavity from the design shape. The entire investigation is based on three pillars: First, experiments at the FLASH facility at DESY in Hamburg are undertaken with the focus on the third harmonic module ACC39. Second, numerical simulations are performed using existing commercial programs such as CST MICROWAVE STUDIO® and in-house codes. Third, new computational methods are developed and implemented. In this context, a method to determine wake fields in large structures by means of decomposition techniques is constructed. Moreover, a generalized perturbation theory is in development which determines a set of eigenmodes of the perturbed geometry based on a set of eigenmodes of the unperturbed shape. Overall, the research efforts are aiming for a sophisticated understanding of diagnostics based on HOM port signals. The long term goal is the equipment of current and future machines with diagnostics based on HOMs.

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issue 5

Targeting the Energy Frontier for next Accelerators

Sabrina El Yacoubi — Fri, 28 Nov 2014 08:09:00 +0000

Targeting the Energy Frontier for next Accelerators
by Frank Zimmermann (CERN)

Layout of SAPPHiRE g-g collider Higgs factory delivering 10k Higgs per year.

Recently two EuCARD-AccNet events explored options for the next accelerators at the energy frontier. The EuCARD “SAPPHiRE Day” on 19 February focused on the key components of a proposed g-g collider Higgs factory, based on a recirculating SC linac. The “Joint Snowmass-EuCARD/AccNet-HiLumiLHC meeting on Frontier Capabilities for Hadron Colliders 2013” on 21-22 February investigated the next generations of hadron colliders up to the 100 TeV scale. Both workshops attracted about 50 experts from around the world.

The proposed SAPPHIRE layout is a moderately expensive step towards a higher-energy linear collider, demonstrating the handling of 20-nm spot sizes while delivering first-rate physics results. The emphasis of the SAPPHiRE Day was on the laser system, optical cavity, interaction region design, and FEL approaches.

The joint workshop on frontier capabilities explored the parameters and 20-T magnets for a 33-TeV c.m. pp collider in the existing LHC tunnel and for a 100-TeV c.m. collider in a new 80-km tunnel. The workshop reviewed the high-field magnet development status and plans at CERN and LBNL.

High Temperature Superconductors in the LHC

Sabrina El Yacoubi — Thu, 27 Nov 2014 14:37:07 +0000

High Temperature Superconductors in the LHC
by Amalia Ballarino (CERN)

Maquette of High Temperature Superconducting Link of the type needed at LHC Point 7. Image credits: CERN

Superconducting links in accelerator systems enable powering of the cryo-magnets from remote power converters. The development carried out within Task 5 of the EuCARD Work Package7 aims at providing such technology for the remote powering of LHC magnets.

The use of High Temperature Superconductors (HTS) in Superconducting Links has the great benefit of enabling the development of a powering system where superconductors can be operated with a generous temperature margin. To enable the use of superconductors with tape geometry, a novel concept of cable optimized for DC electrical transmission (Twisted-Pair Cable) has been developed and demonstrated [1], [2]. A cabling machine enabling the controlled assembly of km-long Twisted Pair cables - made from superconductors with different mechanical characteristics - has been conceived, assembled and commissioned at CERN. A full-scale 5 m long prototype link has been made at CERN and successfully tested in nominal conditions at the University of Southampton [3]. A 20 m-long full scale link is being assembled at CERN, where it will be tested in nominal and transient conditions.

The main outcomes of this activity are: (1) the development of a novel concept of superconducting cable for electrical transmission that can be made from any of the HTS tape-conductors today available (BSCCO 2223, YBCO or MgB2); (2) the development of a new cabling machine for the controlled assembly of the cable; (3) the development of a full superconducting link system that could be used at LHC Point 7 for the powering of the superconducting magnets. The developed technology could be applied for feeding any superconducting system requiring currents in the 1 kA range at any temperature from liquid nitrogen to liquid helium.

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Development and Testing of Crab Cavities for High Intensity Colliders

Sabrina El Yacoubi — Thu, 27 Nov 2014 14:21:39 +0000

Development and Testing of Crab Cavities for High Intensity Colliders
by Peter McIntosh (STFC)

Fig 1: CLIC ‘Undamped’ Crab Cavity Fabricated.Image credit: Shakespeare Engineering Ltd (UK)

Fig 2: LHC 4-rod Crab Cavity Fabricated. Image credit: Niowave Inc (USA)

The development of innovative crab cavity solutions for high intensity particle colliders is part of both the FP7 EUCARD and HiLumi framework programmes.

The activity has been led by Lancaster University and STFC in the UK, in direct collaboration with CERN. For LHC, a compact Superconducting RF (SRF) solution at 400 MHz, capable of fitting into the confined space available at the LHC interaction regions is proposed. A compact TEM type deflecting structure has been manufactured at Niowave from bulk Niobium, which has been tested in SM18 at CERN, reaching a surface magnetic field of 33 mT (limited by a serious LHe leak). This represents the world's first high field test of a compact SRF deflector and the cavity is currently undergoing additional BCP processing in order to reach the LHC design gradient of 6 MV/m (Bpk~70 mT).

For CLIC, a high gradient 12 GHz, normal-conducting travelling-wave structure, with a high group-velocity to minimise the effects of beam loading, has been developed. Two ‘undamped’ structures have been fabricated, one in the UK by Shakespeare Engineering Ltd and the other at CERN. Systematic high gradient tests are planned at SLAC and CERN, to study breakdown differences between deflecting and accelerating structures. A third ‘damped’ cavity is currently being developed to allow verification of the operational performance. A high phase stability control system, which will keep the phase from a klystron stable over long distances, is also in development to meet the stringent CLIC phase stability tolerances.

Visions for the future of particle accelerators

Sabrina El Yacoubi — Thu, 27 Nov 2014 11:31:14 +0000

Visions for the future of particle accelerators
by Agnes Szeberenyi (CERN)

Poster of EuCARD'13 event at CERN was combined with a workshop on the Visions for the Future of Particle Accelerators. Image credit: EuCARD

The recently held EuCARD'13 event at CERN was combined with a workshop on the Visions for the Future of Particle Accelerators, which targeted to discuss the challenges for the next 50 years of research and development in accelerator physics.

The ambitions of accelerator-based sciences and applications far exceed the present accelerator possibilities. The natural time constant of accelerator technologies or projects is in the 20 to 30 years. Hence prospective studies require a vision over a 50 year period, to become liberated from today project considerations.

This 2-day workshop aimed at identifying the ultimate limits of concepts and technologies presently used or contemplated and at investigating possible future avenues requiring generic accelerator R&D. Two round tables on the role of EC projects and on the role of industry complemented the scientific perspectives.

Jean-Pierre Koutchouk, Maurizio Vretenar and Frank Zimmermann as the workshop organizers will report on the outcomes of the event in the next, Autumn Issue.

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Mechanical stabilisation of CLIC quadrupoles to the sub nanometre

Sabrina El Yacoubi — Thu, 27 Nov 2014 11:10:37 +0000

Mechanical stabilisation of CLIC quadrupoles to the sub nanometre
by Kurt Artoos (CERN)

A CLIC Main Beam Quad prototype on two stabilisation actuators.
Image credit: CERN

In order to reach the luminosity of 2.1034 cm-2m-1 in CLIC, the cross section of the colliding particle beams at the interaction point will be in the order of the nanometre. Quadrupole magnets are used as focusing elements to keep the beam size small along the full accelerator length and to focus the beams to the collision point

Mechanical vibrations transmitted to the quadrupoles will however create small dynamic displacements of the magnets, resulting in a gradual increase of the beam size along the accelerator and jitter of the beam at the interaction point.

Vibration stabilisation systems were developed and successfully tested both at CERN and at LAPP Annecy under EuCARD WP9 framework. The level of vibrations of the quadrupoles is decreased by the systems to values smaller than a nanometre. The calculated gain in luminosity obtained by this vibration reduction is significant. The magnets are placed on vibration isolating supports based on piezo-electrical actuators that will reduce the vibrations measured by seismometers placed on the ground and on the magnet. The same actuating support makes it also possible to make very precise adjustments to the magnet. A precision of a quarter of a nanometre was already demonstrated on a prototype.

During 2013, new full scale prototypes will be constructed in order to move from a laboratory set-up to an accelerator component, integrated with other technical systems. Improved vibrations sensors are being developed.

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Phase Control at CLIC

Sabrina El Yacoubi — Thu, 27 Nov 2014 10:34:52 +0000

Phase Control at CLIC
by Fabio Marcellini (INFN)

In a two-beam system, the RF power is provided by the drive beam to the main beam accelerating structure. Drive Beam timing errors must be avoided to maximize the acceleration gradient uniformity in the accelerating structures, and consequently to stabilize the Main Beam energy and optimize the collider luminosity. Image credit: CERN.

Extremely precise beam phase control is required for CLICtwo-beam acceleration technology as well as in Free Electron Lasers (FELs). The development of beam arrival time measurement systems has been carried out within Task 5 of the EuCARD Work Package 9, in collaboration with CERN, INFN/LNF and PSI.

In CLIC the Main Beam must be precisely synchronized with respect to the RF power produced by the Drive Beam. Timing errors would have an impact on the collider performance. The Drive Beam phase errors should be controlled, by means of a feed forward system, within 0.1Рat 12 GHz, corresponding to a timing stability below 23 fs, to avoid a luminosity reduction larger than 2%. A prototype of such a system is being installed in the CLIC Test Facility CTF3 and the performances of the beam phase arrival monitor have been already successfully tested.

FELs also require a tight synchronization of the beam with respect to photo injector lasers, RF and other systems. The beam phase measurement has been pursued at PSI with a different approach based on electro optical modulators. It has the advantage of very high band width, allowing the measurement of individual bunches arrival time with a potential resolution below 10 fs. The system was tested and the performance with beam validated at the PSI FEL test injector.

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Thin films for Superconducting RF

Sabrina El Yacoubi — Thu, 27 Nov 2014 10:28:12 +0000

Thin films for Superconducting RF
by Sergio Calatroni (CERN)

Pb-coated photocatode plug, and global view of the 1.5-cell 1.3 GHz cavity used for testing. Image credit: CERN

The activity led by CERN in close collaboration with several other laboratories (CI-Lancaster, CEA, CNRS-IPNO, DESY, SINS) within the EuCARD Work Package 10.4 aims to address diverse topics in the thin film technology applied to SRF.

The analysis of the relative merits of several state of the art thin film coating technologies and the establishment of a network of SRF thin film test facilities were the first goal of this activity. The second goal was the establishment of state of the art Nb/Cu deposition on QWR cavities by sputtering techniques, including also the novel HIPIMS technique which has been demonstrated first on elliptical cavities. The third goal was the successful demonstration of the compatibility of arc-coated Pb photocathodes with the stringent requirements needed for achieving high surface fields, when used in conjunction with state of the art Nb superconducting cavities.

The several positive results obtained in this task have led to the establishment of two new tasks in EuCARD-2, which are devoted to the further development of innovative thin films (multilayers, HIPIMS, new materials) and of photocathode manufacturing processes.

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Accelerator work at Swierk

Margarita Synanidi — Thu, 27 Nov 2014 10:01:38 +0000

Accelerator work at Swierk
by Kate Kahle (CERN) with Agnes Szeberenyi

Lillyput 3 is an industrial accelerator with photon energy 6 & 9 MV that is easily transportable for nondestructive inspection tests. (click image to enlarge) Image credit: NCBJ, HITEC division

The largest research institute in Poland, the National Centre for Nuclear Research (NCBJ) showcased an impressive variety of accelerator R&D and construction during the recently held EuCARD annual meeting in Warsaw.

Created in 2011, NCBJ merged the Soltan Institute for Nuclear Studies (IPJ) and the Institute of Atomic Energy POLATOM, and now has more than 1,000 employees. The institute is involved in several international projects and research infrastructures, constructing components such as proton buncher and –mode structres (PIMS) for the LHC Linac4, higher order mode (HoM) absorbers for European-XFEL, developing e^- accelerator for the GBAR experiment at CERN, integrating elements of neutral beam injection system (NBI) for the Wendesltein 7-X stellarator in Greifswald, etc.

It is home to the research reactor MARIA, specialising in neutron beam research, activation analysis and isotope production for medical use. In addition, NCBJ develops accelerators for industry, such as the non-destructive inspection techniques of Lillyput, and accelerators for medicine, such as COLINE linear accelerators used in radiotherapy for treating cancer.

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