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Progress in the interaction region magnets of HL-LHC

Panagiotis Charitos — Mon, 06 Mar 2017 14:06:40 +0000

Progress in the interaction region magnets of HL-LHC
by Ezio Todesco (CERN)

During the past months, significant advancements have been done in the development of the interaction region magnets for HL-LHC.

In KEK, Japan, the short model of the separation dipole D1, that showed insufficient quench performance after the first test, has been disassembled. Significant movements of the coils (up to few mm) were observed in the heads, and a clear evidence of a lack of prestress in the straight part was found. The new assembly took place during winter, and a prestress increase in the straight part of about 35 MPa has been achieved. The magnet was tested in February, reaching nominal current after 2 quenches and ultimate after 5 quenches (see Figure 1). “The magnet performance is now in line with the project requirements – says T. Nakamoto, in charge of the D1 project – we will have a warm-up and cool-down to prove the magnet memory in the next weeks”. The short model design is being updated in some features of the iron yoke, and to account for an unexpected contribution to field quality from the coil heads in the strong regime of saturation. A second model will be built in the second part of 2017, and tested in 2018.

Figure 1: Training of MBXFS1 in KEK: quenches (markers), nominal and ultimate current (solid lines) and short sample limit (dotted line). (Credit: HL-LHC WP3 collaboration)

In the US, the first 4-m-long coil has been tested in a mirror configuration, reaching 85% of short sample limit (see Figure 2). “This is the new world record for coil length in Nb₃Sn accelerator magnets – says G. Ambrosio, in charge of the US contribution for the triplet - and paves the way to the assembly and test of the first 4-m-long quadrupole, to be done in the second part of the year”. At the same time at CERN the first 7.15-m-long dummy coils are being produced to validate the assembly procedures (see Figure 3).

Figure 2: Training of mirror 4-m-long coil in BNL: quenches (markers), 70% and 80% of short sample (solid lines) and short sample limit (dotted line). (Credit: HL-LHC WP3 collaboration)

Figure 3: Winding of the first 7.15-m-long dummy coil of the triplet quadrupole at building 180 (CERN)

Furthermore, in CIEMAT, Madrid, the prototype for the nested orbit correctors is entering the construction phase. The concept of double collaring has been validated on a mechanical model with the final design of the collars and a dummy coil made of aluminum (see Figure 4). This is an important step of the validation of the mechanical concept of this magnet, where a mechanical lock between the horizontal and vertical dipoles is required to control the large torque. In particular, the second collaring of the outer dipole on the inner one is critical. “Both collaring operations were in line with our expectations, and we managed to insert pins without any criticality – said F. Toral from CIEMAT, in charge of the Spanish contribution for the orbit correctors – we saw some asymmetries that need more investigations, but given the complexity of the design, this is a very encouraging first step towards construction”.

Figure 4: Double collaring of the nested corrector in CIEMAT

Finally, in LASA, Milano the activity on the high order corrector prototypes is at full speed. After the successful test of the sextupole, the first decapole coil in a single coil configuration has been tested successfully. The coil reached twice the ultimate current with negligible training, thus proving the assembly procedures and tooling concepts. LASA is working in parallel on two magnets: besides the first decapole coil, eigth octupole coils have been completed and will be assembled in the first prototype, and tested in April.

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issue 20

CESSAMag delivering impact

Livia Lapadatescu — Wed, 01 Mar 2017 07:43:30 +0000

CESSAMag delivering impact
by Livia Lapadatescu (CERN)

The main objective of the FP7-CESSAMag (CERN-EC Support for SESAME Magnets) project was to support the construction of the SESAME light source in the Middle-East. With financial contribution from the EC, CERN’s main objective was to deliver the magnetic system and its powering scheme for the SESAME main accelerator ring, as well as to support the training of SESAME staff. Completed at the end of 2016, the project fulfilled or exceeded all its objectives.

Scientific and technical impact of CESSAMag

Section of the SESAME Main Accelerator Ring (Image credit: CERN)

Building upon SESAME studies, CESSAMag finalized the requirements and design and produced the engineering and technical drawings of the SESAME magnets and powering scheme. The first main result of CESSAMag is the production of design reports on the combined function bending magnets, on the quadrupole magnets (long and short), on the sextupole magnets with their auxiliary corrector windings and on the powering scheme. These design and engineering study reports were used as background for the technical specifications needed for tendering and can serve as reference for the construction of similar light sources.

During the tendering process, CERN made a special effort to place orders not only with experienced European companies, but also with companies based in some of the SESAME Members (Cyprus, Israel, Pakistan, Turkey), without former experience in accelerator components (except for Israel), but demonstrating potential and motivation. This was achieved through effective knowledge transfer from CERN and generated potential commercial impact in the companies trained.

All magnets successfully passed the acceptance tests at either ALBA-CELLS or CERN and their measured field quality and reproducibility from magnet to magnet are excellent, making them a reference for similar synchrotrons. Therefore, a key result of CESSAMag is the string of magnets forming the SESAME storage ring, composed of:

16 combined function bending magnets (dipole + quadrupole)
64 quadrupoles of two types: 32 long focusing and 32 short defocusing quadrupoles
64 sextupole/correctors

CESSAMag also contributed to the production of an improved magnet powering scheme: rather than procuring power supplies adapted to each kind of magnet, another approach was proposed by CERN, based on light source standards (PSI), which allows individual powering of quadrupoles and simplified maintenance by plug-and-play modules by standardizing interfaces. With this strategy, SESAME benefits from a powering strategy more powerful, flexible and robust than initially foreseen.

Following the decision to procure some components from companies based in the SESAME Members and thanks to the in-kind contribution of Pakistan, offering the assembly of 50% of the sextupoles, CESSAMag managed to deliver a more powerful and complete magnetic system and reduce the financial share that SESAME was due to contribute to the project.

Finally, CESSAMag contributed to the magnet integration and commissioning, with the goal of making SESAME fully in control of the equipment delivered by CERN.

The first beam was circulated in the SESAME main accelerator ring on 11 January 2017 and it was stored and accumulated up to 20mA in mid-February. The next step is ramping the beam and completing the RF stations and final acceleration assessment expected before the end of summer. The inauguration ceremony of the SESAME light source will take place in mid-May with the foreseen presence of high-ranking officials from SESAME Members and Observers. The first user experiments are foreseen to start in Q3.

Political and social impact of CESSAMag

A significant aspect showcasing the socio-economic impact of CESSAMag is the knowledge transfer to companies from SESAME Members and training of SESAME staff. The duration of training to staff, engineers and companies from SESAME Members amounts to about 90 person-months and the CERN personnel effort in training and knowledge transfer amounts to 16 person-months.

In the context of CESSAMag, international collaborations and agreements were established between CERN and SESAME and CERN and ALBA-CELLS; implementation agreements were formed with PAEK (Pakistan), TAEK (Turkey) and ILSF (Iran) and an informal collaboration with IAEA, which provided financial support for training and experts’ visits between CERN and SESAME. These collaborations and agreements illustrate the international and science diplomacy dimensions of the project.

Furthermore, the European Union acknowledged the science diplomacy impact of CESSAMag and made further steps in support of SESAME. Since 2015, the EU is an Observer in the SESAME Council and the EC decided to further support the training of SESAME users and staff in the framework of the OPEN SESAME (Opening Synchrotron Light for Experimental Science and Applications in the Middle East) H2020 “Policy and international cooperation measures for research infrastructures” project.

*****

This article is based on the Project Final Report.

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Triplet magnets program progressing on both sides of the Atlantic

Panagiotis Charitos — Tue, 06 Dec 2016 11:19:36 +0000

Triplet magnets program progressing on both sides of the Atlantic
by G. Ambrosio, P. Ferracin, E. Todesco (CERN)

The Nb3Sn 150 mm aperture quadrupoles MQXF, to be installed in the inner triplets around ATLAS and CMS in 2024-5, are entering a critical phase; the first two 1.5-m-long models have been manufactured and tested since the beginning of this year.

This magnet development program, carried out as a joint effort between CERN and US LARP foresees the construction and testing of five 1.5-m-long models to validate the design and fine tune the assembly features during 2014-17.

These magnets rely on the Al shell and bladder&key structure, allowing easy and fast disassembly, and a precise tuning of the coil prestress. Mechanics is a critical part in the design of these large aperture quadrupoles, featuring an 11.4 T peak field in the coils (50% larger than the peak field in the LHC dipoles operating at 6.5 TeV).

The first model, MQXFS1, was assembled in the U.S. with two CERN coils and two LARP coils, and was confirmed to fulfil performance requirements in April 2016 (see Figure 1). The performance requirements included a) reaching the ultimate current (8% higher than the nominal current of 16.4 kA), and b) reaching nominal current after a thermal cycle with at most one quench.

Figure 1: Training of MQXFS1: quenches (markers), nominal and ultime current (solid lines) and short sample limit (dotted line). (Credit: HL-LHC WP3 collaboration)

The memory after thermal cycle has outperformed expectations by exceeding ultimate current in the first quench after the thermal cycle. However, training has been slower than expected, reaching nominal current after nine quenches. After this first cycle of testing, the transverse pre-stress in the magnet was increased by 30%, to ensure a better support to the coils.

In October 2016, the second assembly was tested at FNAL, reaching 18.8 kA; which is 15% more than the nominal current, and close to 90% of the maximum theoretical performance of the magnet. Some detraining has been observed sporadically, reducing the magnet performance but keeping it always well above the nominal current.

At 4.2 K the magnets shows the ability to reach the same current, thus demonstrating the existence of a considerable margin in temperature, meaning the magnet should tolerate local heating).

The second model, MQXFS3, (MQXFS2 has been postponed to 2017) has been tested at CERN in October 2016, using a novel test station (HFM) planned to be used for the Fresca II dipole.

The magnet reached nominal current with nine quenches, as MQXFS1, but reached a current only 4% above nominal after 20 quenches. A significantly larger detraining than in MQXFS1 was observed, pushing the magnet performance well below nominal (15.0 kA).

Nonetheless, the maximal performance of 17.2 kA has been recovered after ramp rate tests. In addition, 4.2 K test, shows the same performance reached at 2.1 K and also demonstrates the existence of a considerable temperature margin.

Training of MQXFS3: quenches (markers), nominal and ultimate current (solid lines) and short sample limit (dotted line). (Credit: HL-LHC WP3 collaboration)

Work is now focussed on understanding the relationship between the quenches and the mechanical structure. As quenches are mainly located in the coil heads the longitudinal preload will be increased. Further testing after the thermal cycle is expected for the end of the year and . three additional models are foreseen in 2017.

The program will run in parallel with the development of the long coils (4.2 m in US and 7.15 m in CERN) required for the full size magnets.

“The short model program is a fundamental tool to master the design and construction of superconducting magnets, and it is even more important for a novel technology as Nb3Sn” says L. Bottura, leader of the CERN Magnet, Superconductors and Cryostat group. “If needed, we will prolong the short model program to improve our understanding and to reduce the risks in the construction of the prototypes and of the series.”

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QUACO companies ready for announcement

Jennifer Toes — Fri, 16 Sep 2016 10:55:07 +0000

QUACO companies ready for announcement
by Isabel Bejar Alonso (CERN) & Panos Charitos (CERN)

The QUACO project logo (Image: CERN)

The four companies that will participate in phase 1 of the QUACO project are expected to be announced on the 29th September 2016. QUACO is a Pre Commercial Procurement (PCP) Project (Grant Agreement 689359) with scope to procure two pilot 3.8 m quadrupole magnets with two 90 mm apertures, an integrated gradient of 440 T with 120 T/m in the transverse plane, and which will have an operational temperature of 1.9 K. The magnets will be installed in the matching sections.

PCP is the European Union’s Horizon 2020 COFUND instrument for purchasing R&D services for the development of innovative products, services or processes. One of the biggest advantages of PCP is that it allows all involved parties, both public buyers and private suppliers, to share opportunities as well as risk. As such, public purchasers are able to acquire innovative solutions to satisfy challenging needs. In addition, the project supports the R&D of enterprises, with particular benefits for small and medium enterprises (SMEs) which are encouraged to grow their competitive capital.

Leading companies in the field of magnet production attended the first QUACO meeting to provide an impression of present needs and share feedback with CERN experts (Image: CERN)

The QUACO project draws together four research infrastructures with similar technical requirements in magnet development. By pooling efforts on technological requirements and using their experience from prior procurements, the partners in QUACO act as a single buyer group with sufficient momentum for potential suppliers to consider the phased development of the requested magnets.

The four QUACO partners are:

Commissariat à l’Energie Atomique et aux Energies alternatives (CEA), France,
European Organization for Nuclear Research (CERN), Switzerland,
Centro De Investigaciones Energeticas, Medioambientales Y Tecnologicas (CIEMAT), Spain,
Narodowe Centrum Badan Jadrowych (NCBJ), Poland

CERN acts as the lead procurer coordinating and leading the joint procurement in the name and on behalf of the aforementioned organisations.

The project began on 1 March 2016 and will come to an end in February 2020. It is divided into three phases: solution design, prototyping and pilot deployments, with intermediate evaluations after each phase that will progressively select the best competing solutions.

The QUACO Open Market Consultation was held at CERN on 30 March 2016. Leading companies in the field of magnet production attended the meeting to provide an impression of present needs and share feedback with CERN experts. The meeting covered a range of topics, from technical aspects, such as the current status of the Q4 magnet, its technical scope and requirements; to more legal and administrative matters, such as the legal and contractual framework in which the procurement will be executed. Moreover, CERN engineers demonstrated several examples of tools and fabrication methods that might be used in the frame the project. The project tooling requirements were explained, and the market availability and areas for development were identified.

Pre-commercial procurement is a unique and novel procurement method in the field of accelerator components, and QUACO aims to demonstrate its full potential for success in this field.

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Successful completion of the HQ program, testbed for the LHC IR quadrupoles

Alessia Barachetti — Thu, 19 Nov 2015 13:14:10 +0000

Successful completion of the HQ program, a testbed for the LHC IR quadrupoles
By Giorgio Ambrosio (FNAL), Guram Chlachidze (FNAL), P. Ferracin (CERN) and GianLuca Sabbi (LBNL)

LARP High Field quadrupole (HQ) magnet cross section.

The US LHC Accelerator Research Program (LARP) scientists, in collaboration with CERN, have completed tests on the latest series of the 120 mm aperture Nb₃Sn High-field Quadrupoles (HQ03). The HQ03 serves as a testbed for the development of the new HL-LHC IR quadrupoles (MQXF), for which a short model is currently undergoing tests.

Two test cycles were carried out on LARP’s latest series of the 120 mm aperture Nb₃Sn High-field Quadrupoles (HQ03) that serve as a basis for the MQXF. This third series applies optimized design solutions and improves the coil-to-coil uniformity. Quench training was performed entirely at 1.9 K with a room-temperature cycle between two test cycles. The magnet demonstrated excellent performance: in both test cycles, it surpassed the nominal operating gradient, corresponding to 80% of the conductor (short sample) limit, without quenches. The highest current reached at 1.9 K was 16.1 kA, achieving 90% of the short sample limit (SSL). At 4.5 K the model achieved 98% SSL. Magnetic shims placed inside the iron yoke have also proved effective to correct magnetic field errors.

As we reported in our June 2015 issue, a first 150 mm aperture MQXF coil manufactured in the US was tested at FNAL in a mirror configuration. The coil reached 90% of the short sample limit after 20 quenches. This was the first successful test proving the design of the MQXF coil. Following the mirror test, the first MQXF short model has been assembled in LBNL and is undergoing testing at Fermilab.

Assembly of MQXFSM1 Mirror magnet. Credits: Reidar Hahn (FNAL)

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16.2 T peak field reached in RMC racetrack test magnet

Alessia Barachetti — Thu, 19 Nov 2015 10:48:07 +0000

16.2 T peak field reached in RMC racetrack test magnet

by Luca Bottura, Juan Carlos Perez, Paolo Ferracin, Gijs de Rijk (CERN)

The RMC_03 racetrack test magnet. Credits: CERN

This September, experts from the CERN Magnet Group in the Technology Department celebrated the achievement of a 16.2T peak field in the Racetrack Model Coil (RMC). This is twice the nominal field of the LHC dipole and the highest field ever reached with this configuration. The result, which pushes forward existing boundaries for high-energy accelerators, is the product of a successful cooperation between several R&D programmes within the physics community.

Tested in the CERN SM18 vertical test station at a temperature of 1.9 K, the RMC, which consists of two racetrack coils, trained up to a maximum current of 18.5 kA, within less than 5% of the projected critical current of the cable. Based on the calculation of the field, this current corresponds to peak fields of 16 T on the 33-turns Powder-In-Tube (PIT) coil and 16.2 T on the 35-turns Rod Restack Process (RRP) coil. Three major ingredients made this achievement possible. First, such high fields are only possible thanks to the use of Nb₃Sn, a intermetallic and brittle compound which withstands a much higher magnetic field intensity compared to the previously-used Nb-Ti alloy. Secondly, RMC uses new technologies that allow the coil to resist increasingly high electromagnetic forces. An example of this is the “bladder-and-keys” structure developed at LBNL (USA). The third and perhaps most important ingredient was the close relationship with European and overseas R&D programmes, which joined efforts and synergies to push through existing technology barriers.

The RMC result feeds in a larger objective shared by most high-energy accelerator projects: reaching high magnetic fields to permit higher beam energies – in the case of dipoles - or to squeeze the beam in the experiments, which is the case for high-gradient quadrupoles. RMC-type tests are now a part of the technology programme that supports the EU-funded EuroCirCol design study, which, in turn, is part of the Future Circular Collider study. This aims to be a conceptual design study for a post-LHC research infrastructure focuses on an energy frontier 100 TeV circular hadron collider. The test setup and measurement provide evidence for the feasibility of a 16 T dipoles based on low-temperature Nb₃Sn superconductors. For this reason, the personnel in charge of setting up the testbed, working with industry and performing the test, are also working for the FCC 16 T magnet R&D programme.

RMC tests are a major step for many other R&D projects. In fact, they serve as technology support for the new High Luminosity LHC Interaction Region quadrupole QXF and for the 11 T dispersion suppressor dipoles. Finally, RMC is using wires and cables of the same class as those being used to build FRESCA2, a 13 T dipole magnet with a 100 mm aperture that will be used to upgrade the CERN cable test facility (FRESCA). FRESCA2 coils are currently under construction and will be ready for testing by summer 2016.

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First hardware for HL-LHC interaction region magnets

Livia Lapadatescu — Mon, 22 Jun 2015 08:24:51 +0000

First hardware for HL-LHC interaction region magnets
by Ezio Todesco (CERN)

The coil of the sextupole corrector
Courtesy of G. Volpini and LASA laboratories

The mirror QXF entering the FNAL test station
Courtesy of G. Chlachidze and US-LARP

The Interaction Region (IR) of the HL-LHC project will be made of nine different types of new magnet, relying on three different technologies (Nb3Sn and Nb-Ti with Rutherford cable, and superferric magnets with Nb-Ti coils).

These magnets are in the design and prototype phase, developed by five international collaborations: US-LARP, CIEMAT (Spain), CEA Saclay (France), INFN-Milano LASA laboratories and INFN-Genova (Italy), and KEK (Japan). The HL-LHC design study is now approaching completion: the conceptual design is nearly finished, engineering is in progress and the first hardware that will be used in the prototypes is being manufactured and tested. This is a very exciting phase as the project shifts from paper to hardware.

In April 2015, the winding and impregnation of the first coil of the superferric sextupole corrector (see image above-left) was completed. As a stand-alone coil it was successfully tested in INFN-LASA laboratories. This collaboration has won the race towards the first test of a component of the HL-LHC interaction region magnets. The coil had a first quench at 80% of short sample limit, and reached 91% after 3 quenches, at 2.5 K. In these correctors, the operational current is set at 60% of short sample limit.

In May 2015, the first short coil of the Nb3Sn quadrupoles, manufactured by the LARP collaboration, was tested in a mirror configuration at FNAL, US. The coil had a first quench at 70% of short sample limit, a second one at 76%, and reached 90% after 20 quenches. The triplet will operate at 75% - this value has been recently reduced from the original 80% value to add some margin, following the advice of the review committee held in December 2014 and chaired by Dr. A. Yamamoto (KEK).

Since the beginning of the year, coil winding tests are going on both in KEK, for the 5.6 T Nb-Ti separation dipole (D1), and in Saclay, for the 115 T/m gradient Nb-Ti quadrupole. In KEK, an iteration of the design of the iron yoke has been performed to guarantee a better alignment of the dipole field during assembly. In CEA, first tests have confirmed the correct geometry of the end spacers and of the coil components.

The next step is the test of the Nb3Sn quadrupole short model in autumn 2015, made up of two CERN coils (just shipped to the US) and two LARP coils. At the end of the year a test of the first corrector sextupole is foreseen in LASA, and a test of the first short model of the separation dipole will be carried out in KEK, Japan.

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Bending magnet for SESAME storage ring

Livia Lapadatescu — Tue, 14 Apr 2015 09:27:03 +0000

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.

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A first layout for the High Luminosity Upgrade

Sabrina El Yacoubi — Thu, 27 Nov 2014 14:26:50 +0000

A first layout for the High Luminosity Upgrade
by Ezio Todesco, Stephane Fartoukh (CERN)

The tentative layout for the insertion: sequence of magnets versus distance to the interaction point in ATLAS or CMS (0 m is the centre of the experiment). The flags indicate a possible origin of the in-kind contribution.
Image credit: HiLumi LHC

A first baseline for the layout of the High Luminosity inner triplet and associated magnets has recently been defined. This is the second major milestone, after the choice of a 150 mm aperture for the quadrupoles in July 2012.

A layout is the selection of the sequence of magnets, their strength, their length, and the associated technology: therefore, it requires inputs both from the optics and from the magnet teams. Its definition is a delicate equilibrium between the search for maximum performance and the need of minimizing complexity and associated risks. Nb3Sn technology had been already selected for the triplet quadrupoles – these magnets are planned to be built with a CERN-US collaboration, heavily relying on the work carried out by LARP in the past 10 years.

After the triplet, a separation dipole of 5.5 T, in Nb-Ti, is being studied by the Japanese team in KEK. The layout is complemented by the challenging orbit correctors, also based on Nb-Ti technology, with nested coils both providing horizontal and vertical field of up to 2 T. A package of higher order correctors relying on superferric technology is also available, in order to correct for the inevitable field imperfections of the inner triplet at the 10-4 level. The triplet corrector package is based on the design developed in Spain by CIEMAT.

As a result, the energy deposition team can start simulations to have a precise estimate of the radiation damage and heat loads coming from the collision debris. It is a heavy shower and magnets will need thick shielding to avoid falling in pieces before reaching the project ambitious goal of 3000 fb-1. The layout has been presented at CERN and will be extensively discussed at theHiLumi/LARP collaboration meeting, 8-10 April 2013, Napa Valley.

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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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