The ISOLDE Scientific Infrastructure at CERN offers a unique range of post-accelerated radioactive beams. The scientific program can be improved with the "Isolde Superconducting Recoil Separator" (ISRS), an innovative spectrometer able to deliver unprecedented (A, Z) resolution. In this paper we present an overview of the physics and ongoing technical developments.

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years.

With over 128Km of vacuum chambers, reaching pressures as low as in interstellar space, CERN is home to the largest vacuum system in the world. Its underlying architecture comprises approximately 15 000 pieces of control equipment, supervised and controlled by 7 Supervisory Control And Data Acquisition (SCADA) servers, and over 300 Programmable Logic Controllers (PLCs). Their configuration files are automatically generated from a set of ORACLE databases (vacDB) using a Java application (vacDB-Editor). The maintenance management of such an amount of equipment requires the usage of an Enterprise Asset Management system (EAM), where the life cycle of every equipment is tracked from reception through decommissioning. The equipment displayed in the vacuum SCADA is automatically integrated in its user interfaces (UIs) based on data available on vacDB. On the other hand, the equipment available in Infor-EAM for maintenance management activities (creation of work-orders, stock management, location tracking) resides in its own database. This leaves room for mismatches between what users see on the SCADA and in Infor-EAM. Although manual imports of equipment lists from vacDB to Infor-EAM are possible, the process is time consuming, error prone, and only guarantees the correctness of data while no equipment is added, deleted or modified in vacDB. Aiming to solve this issue, a web-based application called vacDM was developed to ensure continuous consistency between vacDB, Infor-EAM and CERN’s dictionary database for equipment descriptions, the naming-DB. Following the implementation of vacDM, the vacuum SCADA was updated to allow the generation of Infor-EAM work orders.

CERN’s Compact linear collider (CLIC) will require two crab cavities to align the beams to provide an effective head-on collision with a 20 mdeg crossing angle at the interaction point. An X-band RF system has been chosen for the crab cavities. Three prototype cavities have been developed in order to test their high power performance. The first cavity has been made by UK industry, while the second cavity has been made using the same process as the CLIC main linac in order understand potential differences in RF breakdown behaviour between deflecting and accelerating cavities. The third cavity incorporates wake-fielddamping waveguides on each cell which will eventually contain RF absorbers. This paper details the design, manufacture and preparation of these cavities for testing and a report on their status.

The future collider CLIC is based on a two -beam acceleration scheme, where the drive beam provides to the main beam the RF power through the Power Extraction and Transfer Structures (PETS). The technical feasibility of some components is currently being proved at the CLIC Experimental Area (CLEX). Two double- length CLIC PETS will be installed in CLEX to validate their performance with beam. The first prototype was produced and validated in 2012. This paper is focused on the engineering design, fabrication and validation of the second prototype. Taking into account the results of the first prototype, some modifications have been included in the design to ease fabrication and assembly. The fabrication techniques are very similar to the ones used for the first prototype. Mechanical measurements on single parts and different assembly stages will be reported. Finally, several tests such as vacuum tightness and RF measurements with low power have been realized to validate the device. These results are compared with the first prototype ones.

The CLIC study has progressively tested prototype accelerating structures which incorporate an ever increasing number of features which are needed for a final version ready to be installed in a linear collider. The most recent high power test made in the CERN X-band test stand, Xbox-1, is of a CERN-built prototype which includes damping features but also compact input and output power couplers, which maximize the overall length to active gradient ratio of the structure. The structure’s high-gradient performance, 105 MV/m at 250 ns pulse length and low breakdown rate, matches previously tested structures validating both CERN fabrication and the compact coupler design.

CLIC (compact linear collider) is a future e+e− collider based on normal-conducting technology, currently under study at CERN. Its design is based on a novel two-beam acceleration scheme. The main beam gets RF power extracted from a drive beam through power extraction and transfer structures (PETS). The technical feasibility of CLIC is currently being proved by its Third Test Facility (CTF3) which includes the CLIC experimental area (CLEX). Two Double Length CLIC PETS will be installed in CLEX to validate their performance with beam. This paper is focused on the engineering design, fabrication and validation of this PETS first prototype. The design consists of eight identical bars, separated by radial slots in which damping material is located to absorb transverse wakefields, and two compact couplers placed at both ends of the bars to extract the generated power. The PETS bars are housed inside a vacuum tank designed to make the PETS as compact as possible. Several joint techniques such as vacuum brazing, electron beam and arc welding were used to complete the assembly. Finally, several tests such as dimensional control and leak testing were carried out to validate design and fabrication methods. In addition, RF measurements at low power were made to study frequency tuning.

The CLIC two-beam module prototypes are intended to prove the design of all technical systems under the different operation modes. Two validation programs are currently under way and they foresee the construction of four prototype modules for mechanical tests without beam and three prototype modules for tests with RF and beam. The program without beam will show the capability of the technical solutions proposed to fulfil the stringent requirements on radio-frequency, supporting, prealignment, stabilization, vacuum and cooling systems. The engineering design was performed with the use of CAD/CAE software. Dedicated mock-ups of RF structures, with all mechanical interfaces and chosen technical solutions, are used for the tests and therefore reliable results are expected. The components were fabricated by applying different technologies and methods for manufacturing and joining. The first full-size prototype module was assembled in 2012. This paper is focused on the production process including the comparison of several technical solutions adopted during the realization. The module assembly procedure and quality control measurements are also recalled.

Five types of CLIC prototype TW accelerator structures were high-gradient tested at KEK, up to 100 MV/m level. The ramping speed of each processing and the resultant breakdown rate were compared among them. From this comparison, it was found that the ramping speed of the structures with opening ports for HOM damping with magnetic coupling became slow and the resultant breakdown rate became high. This indicates the role of the magnetic field on vacuum breakdowns in copper structure at the region around 100 MV/m. In this paper, we review such processing characteristics and the final high gradient performance of the recent structures. One of the structures showed frequent breakdowns in two particular regions of the structure, indicating a mechanism reflecting not only the geometry or material characteristics but the local features acquired after completion or even during the running.

The final luminosity target of the Compact LInear Collider (CLIC) imposes a micron-level stability requirement on the two-meter repetitive two-beam modules constituting the main linacs. Twobeam prototype modules are being assembled to extensively study their thermo-mechanical behaviour under different operation modes. The power dissipation occurring in the modules will be reproduced and the efficiency of the corresponding cooling systems validated. At the same time, the real environmental conditions present in the CLIC tunnel will be studied. Air conditioning and ventilation systems have been installed in the dedicated laboratory. The air temperature will be changed from 20 to 40°C, while the air flow rate will be varied up to 0.8 m/s. During all experimental tests, the alignment of the RF structures will be monitored to investigate the influence of power dissipation and air temperature on the overall thermo-mechanical behaviour. \nThis test program will allow for better understanding the behaviour of the CLIC modules and the results will be propagated back both to the numerical modelling and the engineering design. Presented at: 4th International Particle Accelerator Conference, Shanghai, China, 12 17 May 2013 Geneva, Switzerland Date 12/05/2013 CLIC – Note – 1001

A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5 x 10{sup -7}/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.

A new klystron based X-band rf power source operating at 11.994 GHz has been installed and started to be commissioned at CERN in collaboration with CEA Saclay and SLAC for CLIC accelerating structure tests. The system comprises a solid state high voltage modulator, an XL5 klystron developed by SLAC, a cavity based SLED type pulse compressor, the necessary low level rf system including rf diagnostics and interlocks and the surrounding vacuum, cooling and controls infrastructure. The system is designed to produce up to 50 MW rf pulses of 1500 ns pulse width and 50 Hz repetition rate. After pulse compression, up to 100 MW of rf power at 250 ns pulse width will be available in the structure test bunker. This paper describes in more detail this setup and the process of commissioning which is necessary to arrive at the design performance.

The very high accelerating gradient of the Compact LInear Collider (CLIC) design requires radio frequency (RF) structures, which operate in a performance range well beyond that found in any existing accelerator. Specifically, power generating structures (PETS), waveguide components and accelerating structures (AS) are being developed, and they have to work with an unprecedented combination of frequency (12 GHz), peak power (100 MW), pulse length (about 300 ns) and accelerating gradient (100 MV/m). Each accelerating structure contains about 30 copper disks, which form the accelerating cavity. The requirements of different technical systems, such as vacuum, cooling and alignment, have to be considered during the engineering design of a fully featured AS. This paper describes the engineering design method and fabrication of the fully featured AS for the CLIC study at CERN.

Micron-level stability of the Compact LInear Collider (CLIC) two-beam modules, two-meter repetitive units constituting the main linacs, is one of the most important requirements to achieve the final luminosity target. High power dissipation during normal operation modes of modules will result in misalignments in and between different elements of the linacs, thus affecting the final resulting luminosity. In this paper, updated finite element models of CLIC two-beam modules are presented and the structural behaviour of them is studied in more detail than in the earlier simulations. In particular, the models have been refined by improving the modelling of actuators and bellows as well as studying the most updated versions of CLIC modules. Based on the main operation modes of the CLIC collider, the results of thermal and structural analysis of two-beam modules are presented. These numerical results will be validated by experimental tests to be performed in 2012 with full-scale CLIC prototype modules. They will allow for better understanding the thermo-mechanical behaviour and they will be propagated back to numerical modelling.

The micron-precision RF structures are mounted and aligned on specially developed supporting girders, which provide stability and re-positioning. The supporting girders have stiffness and damping specifications imposed by stringent beam physics and RF requirements. In addition, several constraints, such as allocated space and weight limitation have to be taken into consideration. This paper describes different support concepts following various fabrication techniques and materials. Extensive qualification measurements have been performed on the first prototype units, and the main results are also reported.

A Damped Detuned Structure (DDS), known as CLIC_DDS_A [1], has been designed for the Compact Linear Collider (CLIC) study, and is presently under fabrication. The wakefield in the DDS structures is suppressed using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. The broad principles of the design are similar to that used in the NLC/GLC [2]. CLIC_DDS_A is conceived to be tested for its capacity to sustain high gradients at CERN. We report on engineering design and fabrication details of the structure. This design takes into account practical mechanical engineering issues and is the result of several optimizations since the earlier CLIC_DDS concept.

The CLEX building in the CTF3 facility is the place where essential experiments are performed to validate the Two-Beam Acceleration scheme upon which the CLIC project relies. The Drive Beam enters the CLEX hall after being recombined in the Delay loop and the Combiner Ring in intense beam trains of 24 A - 120 MeV lasting 140 ns and bunched at 12 GHz, although other beam parameters are also accessible. This beam is then decelerated in dedicated structures installed in the Test Beam Line (TBL) and in the Two-Beam Test Stand (TBTS) aimed at delivering bursts of 12 GHz RF power. In the TBTS this power is used to generate a high accelerating gradient of 100 MV/m in specially designed accelerating structures. To assess the performances of these structures a probe beam is used, produced by a second Linac. We report here various experiments conducted in the TBTS making use of the versatility of the probe beam and of dedicated diagnostics.