[en] PACMAN, a study on Particle Accelerator Components’ Metrology and Alignment to the Nanometre scale, is an Innovative Doctoral Programme, funded by the European Commission, hosted by CERN, providing a high quality training to 10 Early Stage Researchers (ESR) working towards a PhD. It is a multi-disciplinary project covering diverse fields such as beam instrumentation, magnetic measurements, metrology, high accuracy alignment and high precision mechanics. The objective of the PACMAN project is to propose new methods allowing the determination of the reference axis of accelerator components w.r.t. external alignment targets (fiducialisation process). A test bench, using components of the Compact LInear Collider (CLIC) study, will demonstrate the feasibility of the solutions developed and that a micrometric accuracy of their fiducialisation process can be reached. The results of this study, which has started in September 2013, are detailed. They concern the methods developed using a stretched wire to determine: the magnetic axis of small aperture magnets, the electrical centre of a 15 GHz Radio Frequency-Beam Position Monitor (RF-BPM) and the electro-magnetic axis of an accelerating cavity. They integrate also the solutions carried out to measure the position of the wire w.r.t. the external alignment targets. Other systems developed in the frame of the project are also taken into account: a nanopositioning system to validate the nanometric resolution of the BPM and a dedicated seismic sensor to characterize the environment during the measurements. (author)

[en] Crab crossing is essential for high-luminosity colliders. The high-luminosity Large Hadron Collider (HL-LHC) will equip one of its interaction points (IP1) with double-quarter wave (DQW) crab cavities. A DQW cavity is a new generation of deflecting rf cavities that stands out for its compactness and broad frequency separation between fundamental and first high-order modes. The deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may be required. A proof-of-principle (POP) DQW cavity was limited by quench at 4.6 MV. This paper describes a new, highly optimized cavity, designated the DQW SPS series, which satisfies dimensional, cryogenic, manufacturing, and impedance requirements for beam tests at the Super Proton Synchrotron (SPS) and operation in the LHC. Two prototypes of this DQW SPS series were fabricated by U.S. industry and cold tested after following a conventional superconducting radio-frequency surface treatment. Both units outperformed the POP cavity, reaching a deflecting voltage of 5.3–5.9 MV. This voltage—the highest reached by a DQW cavity—is well beyond the nominal voltage of 3.4 MV and may even operate at the ultimate voltage of 5.0 MV with a sufficient margin. This paper covers fabrication, surface preparation, and cryogenicmore » rf test results and implications.

[en] To reach a sufficient luminosity, the transverse beam sizes and emittances in future linear particle accelerators should be reduced to the nanometer level. Mechanical stabilisation of the quadrupole magnets is of the utmost importance for this. The piezo actuators used for this purpose can also be used to make fast incremental orientation adjustments with a nanometer resolution. The main requirements for the CLIC stabilisation electronics is a robust, low noise, low delay, high accuracy and resolution, low band and radiation resistant feedback control loop. Due to the high number of controllers (about 4000) a cost optimization should also be made. Different architectures are evaluated for a magnet stabilisation prototype, including the sensors type and configuration, partition between software and hardware for control algorithms, and optimization of the ADC/DAC converters. The controllers will be distributed along the 50 km long accelerator and a communication bus should allow external control. Furthermore, one might allow for an adaptive method to increase the S/N ratio of vibration measurements by combining seismometer measurements of adjacent magnets. Finally a list of open topics, the current limitations and the plans to overcome them will be presented.

[en] To reach the required luminosity at the CLIC interaction point, about 2000 quadrupoles along each linear collider are needed to obtain a vertical beam size of 1 nm at the interaction point. Active mechanical stabilization is required to limit the vibrations of the magnetic axis to the nanometer level in a frequency range from 1 to 100 Hz. The approach of a stiff actuator support was chosen to isolate from ground motion and technical vibrations acting directly on the quadrupoles. The actuators can also reposition the quadrupoles between beam pulses with nanometer resolution. A first conceptual design of the active stabilization and nano positioning based on the stiff support and seismometers was validated in models and experimentally demonstrated on test benches. Lessons learnt from the test benches and information from integrated luminosity simulations using measured stabilization transfer functions lead to improvements of the actuating support, the sensors used and the system controller. The controller electronics were customized to improve performance and to reduce cost, size and power consumption. The outcome of this study has been implemented in the design of the first prototype of a stabilized CLIC quadrupole magnet. (authors)

[en] In order to achieve the required levels of luminosity in the CLIC linear collider, mechanical stabilization of quadrupoles to the nanometre level is required. The paper describes a design of hybrid electronics combining an analogue controller and digital communication with the main machine controller. The choice of local analogue control ensures the required low latency while still keeping sufficiently low noise level. Furthermore, it reduces the power consumption, rack space and cost. Sensitivity to radiation single events upsets is reduced compared to a digital controller. The digital part is required for fine tuning and real time monitoring via digitization of critical parameters.

[en] This paper presents a new active isolation strategy and system which is dedicated to extended payloads, and compatible with the particle accelerator environment. In comparison to the current isolation systems used in this environment, the system proposed does not contain any coil or elastomer, and the supporting frame is dedicated to isolating long payloads from seismic motion. The concept proposed has been tested numerically on 3 and 6 degrees of freedom (DOF) models, and validated experimentally on a 1-DOF scaled test set-up. An attenuation of 40 dB at 1 Hz has been reached with the stage built. The complete description of performance and a noise budgeting are included in this paper. (paper)

[en] This paper presents an experimental validation of a control strategy capable of both stabilizing and positioning the heavy electromagnets of future particle colliders. The originality of the approach is to use the same active mounts to perform both tasks, with a nanometer precision. In a previous paper, the concept has been studied numerically, and validated on a scaled single degree of freedom (d.o.f.) test bench. In this paper, it is extended to a two d.o.f. test bench, constituted of a heavy mass mounted on two active legs. Firstly, the model is described and the performances are discussed numerically. Secondly, experimental results are presented, and found to correlate well with the model, and comply with the requirements. Finally, the experimental results are combined with a simplified model of the beam-based feedback to evaluate the jitter of the beam. It is found that, at the scale of a single quadrupole, the mechanical stabilization of the quadrupoles reduces the vertical beam jitter by a factor 10.

[en] The future Compact LInear particle Collider (CLIC) under study at CERN will require to stabilize heavy electromagnets, and also to provide them some positioning capabilities. Firstly, this paper presents the concept adopted to address both requirements. Secondly, the control strategy adopted for the stabilization is studied numerically, showing that the quadrupole can be stabilized in both lateral and vertical direction. Finally, the strategy is validated experimentally on a single degree of freedom scaled test bench.

[en] This document gathers the abstracts of the papers presented at the workshop. This workshop was dedicated to the status of the technical support of the LHC (large hadron collider) in CERN. The different issues concern: -) the installation of the equipment in the LHC tunnel (super-conducting magnets, cold boxes, PS magnets...), -) underground logistics, -) the installation of experimental areas, -) the new CERN control center, and -) special technologies. (A.C.)

[en] The LHC high luminosity project envisages the use of the crabbing technique for increasing and levelling the LHC luminosity. Double Quarter Wave (DQW) resonators are compact cavities especially designed to meet the technical and performance requirements for LHC beam crabbing. Two DQW crab cavities are under fabrication and will be tested with beam in the Super Proton Synchrotron (SPS) at CERN by 2017. This paper describes the design and prototyping of the DQW crab cavities for the SPS test.