It has been previously advocated that the presence of the daily and annual modulations of the axion flux on the Earth's surface may dramatically change the strategy of the axion searches. The arguments were based on the so-called Axion Quark Nugget (AQN) dark matter model which was originally put forward to explain the similarity of the dark and visible cosmological matter densities Omega dark Omega visible. In this framework, the population of galactic axions with mass 10-6 eV ma 10-3 eV and velocity hvai 10-3c will be accompanied by axions with typical velocities hvai 0.6c emitted by AQNs. Furthermore, in this framework, it has also been argued that the AQN-induced axion daily modulation (in contrast with the conventional weakly interactive massive particle paradigm) could be as large as (10-20)%, representing the main motivation for the present investigation. We argue that the daily modulations along with the broadband detection strategy can be very useful tools for the discovery of such relativistic axions. The data from the CAST-CAPP detector have been used following such arguments. Unfortunately, due to the dependence of the amplifier chain on temperature-dependent gain drifts and other factors, we could not conclusively show the presence or absence of a dark sector-originated daily modulation. However, this proof of principle analysis procedure can serve as a reference for future studies.

Hypothetical axions provide a compelling explanation for dark matter and could be emitted from the hot solar interior. The CERN Axion Solar Telescope has been searching for solar axions via their back conversion to x-ray photons in a 9-T 10-m long magnet directed toward the Sun. We report on an extended run with the International Axion Observatory pathfinder detector, doubling the previous exposure time. The detector was operated with a xenon-based gas mixture for part of the new run, providing technical insights for future configurations. No counts were detected in the 95% signal-encircling region during the new run, while 0.75 were expected. The new data improve the axion-photon coupling limit to 5.8×10^{-11}  GeV^{-1} at 95% CL (for m_{a}≲0.02  eV), the most restrictive experimental limit to date.

The High Luminosity Large Hadron Collider (HL-LHC) project will upgrade the LHC machine to allow operation with increased luminosity for the experiments. In order to achieve this goal, different operational parameters of the machine need to be pushed beyond the present design values, including the stored beam energy. One of the main challenges related to the achievement of the upgraded performance is the beam collimation system and its contribution to the overall machine impedance budget. In this perspective, new low impedance collimators have been designed, fabricated, and installed in the LHC. In this study, we will present their detailed electromagnetic (EM) characterization by means of radio frequency (RF) measurements and EM simulations.

A bstract We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μ eV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of g aγ ≳ 4 × 10 − 13 GeV − 1 over a mass range of 34 . 6738 μ eV < m a < 34 . 6771 μ eV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25 μ eV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavities.

Adnan presents a comprehensive analysis of the eddy current testing applied to coating resistivity measurements. He first give an introduction of the method and the procedure followed to characterize the Mo coated MoGr samples and blocks produced by CERN and two external companies, DTI and Politeknik, in view of the installation in the HL-LHC collimators. The method presents a good agreement when measuring on an Al sample. Adnan addresses as well the method reproducibility versus the instrument integration time. it is found that slower integration time is more prone to drift than a fast, but less accurate, one. Adnan analyzes the effect of the geometry on an available copper block of the impedance lab. He divides the surface into a matrix and applies the measurement method on each point: a region of bad conductivity is present and show on a 2D resistivity map. Adnan measures the CERN block with 4 and 8 loops coils. The coating behaviour is present and visible from the peak in resistive impedance: scaling by the maximum of the absolute impedance gives a resistivity close to the nominal value of 52 nOhm.m. The DTI small sample is as well showing the coating peak and resistivity is below nominal. The Politeknik manufactured sample does not show the coating behaviour and it is therefore assumed not to be compatible with requirements. Difficulties have been encountered when measuring thicker blocks, probably due to internal non homogeneity which is difficult to be disentangled. F.Carra wonders how the outcome of the measurement could be on the real 20mm thick blocks. F.Caspers comments that a thin 6um film on Cu/Al has the best contrast at 1 GHz. The eddy current testing is very critical on distance and contrast between bulk and layer resistivity. He questions on the use of the method itself and would propose to take a different approach going higher in frequency (resonant cavity). B.Salvant asks by when an answer needs to be provided. It is by the end of next week to give the green light to the firms. C.Zannini comments that at higher frequency also the roughness will play a role and caution is needed.

Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.

The LHC collimation system is a critical element for the safe operation of the LHC machine. The necessity of fast accurate positioning of the collimator's jaws, recently introduced the need to have button beam position monitors directly embedded in the jaws extremities of the LHC tertiary collimators and some secondary collimators. This addition led to a new design of these collimators including ferrites to damp higher order modes instead of rf fingers. In this work we will present the impedance bench measurements and simulations on a TCT (Transverse Tertiary Collimator) prototype including estimations for beam stability for the LHC.

The TOTEM experiment has been designed to measure the total proton-proton cross section and to study the elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots, movable beam pipe insertions, hosting silicon detectors. In the first period of LHC operation no relevant problems were detected with Roman Pots retracted or inserted during special runs. However, when operating the LHC with high intensity beams, impedance induced heating has been observed during the Roman Pots insertion. In order to be compatible with the higher LHC beam current foreseen after the LS1, a new version of the Roman Pot has been proposed and optimized with respect to the beam coupling impedance. In this work we present the bench impedance measurements carried out on the new Roman Pot prototype. Single and double wire measurements, as well as probe measurements, were performed in order to detect possible harmful resonant modes. The laboratory setup has been as well simulated with the help of CST Particle Studio in order to benchmark the measurement results. Measurements and simulations are in close agreement confirming the equipment compatibility with the LHC requirements for safe operation.

Following the recurrent beam induced RF issues that perturbed the CERN Large Hadron Collider (LHC) operation during Run 1, a series of actions were put in place to minimize the risk that similar issues would occur in Run 2: longitudinal impedance reduction campaigns and/or improvement of cooling for equipment that were problematic or at the limit during Run 1, stringent constraints enforced on new equipment that would be installed in the machine, tests to control the bunch length and longitudinal distribution, additional monitoring of temperature, new monitoring tools and warning chains. This contribution reports the outcome of these actions, both successes as well as shortcomings, and details the lessons learnt for the future runs. INTRODUCTION Beam induced RF heating was one of the major limitations to increasing the LHC luminosity in Run 1 [1]. Temperature increase in near-beam devices, due to electromagnetic fields generated by the proton beam interacting with the longitudinal beam coupling impedance of these devices, was indeed observed to cause severe damage, delays or dumps [2]. During the first long LHC shutdown in 2013-14 (LS1), many actions were taken by CERN equipment groups as well as experiments to solve existing problems and prevent new ones for modified or newly installed hardware [3]. These actions are summarized in the next section, followed by the resulting performance in 2015 with respect to beam induced RF heating and the expectations for 2016. ACTIONS TAKEN DURING LS1 The main actions focused on the equipment already damaged (BSRT synchrotron light monitor, TDI injection protection collimator), that have limited the machine performance (MKI injection kicker, Roman pots) or new hardware (Roman pots, tertiary and secondary collimators with ferrite). High Curie temperature ferrites are now systematically used. BSRT Synchrotron Light Monitor Following the severe heating damage that affected the BSRT mirror, ferrites and support before LS1, a new design that would minimize the shunt impedance of low frequency resonances below 1 GHz and avoid the use of ferrite was studied and installed during LS1 [4]. TDI Injection Protection Collimator Following abnormal deformation of the two TDI beam screens observed in 2011, as well as vacuum, and jaw deformation measurements during the 2011 and 2012 run that suggested significant heating, and mechanical issues at the end of the 2012 run [5], the two TDIs were refurbished in order to improve the stiffness of the beam screen (copper was replaced by stainless steel) and reduce beam induced heating (copper coating was planned to be applied on top of the titanium coated ceramic absorber). However, technical issues with the copper coating of those absorber blocks led to abandon the coating for the 2015 run. The jaws were therefore put back as they were before LS1 from that point of view. MKI Injection Kickers Following the observed increase of temperature that could threaten to go beyond the Curie temperature of the ferrite yoke of one MKI, a new design aimed at reducing the longitudinal impedance of the MKIs by better screening the ferrite from the beam, was implemented for the installed MKIs during LS1 [6, 7]. TCP.B6L7.B1 Skew Primary Collimator A skew primary collimator caused beam dumps in 2011 and 2012 due the steady increase of its jaws’ temperature during physics fills. Electromagnetic and thermal simulations were consistent with a non-conformity of the cooling and it was replaced during LS1. A nonconformity of the cooling circuit routing was confirmed after inspection during LS1 [8]. TOTEM Roman Pots / Beam Screen Regulation During most of Run 1, the beam screen of the standalone quadrupole magnet Q6R5 had no margin for increased cryogenic cooling. Correlation with vacuum and loss activity observed at a nearby TOTEM Roman MOPOR008 Proceedings of IPAC2016, Busan, Korea ISBN 978-3-95450-147-2 602 C op yr ig ht © 20 16 C C -B Y3. 0 an d by th e re sp ec tiv e au th or s 05 Beam Dynamics and Electromagnetic Fields D04 Beam Coupling Impedance Theory, Simulations, Measurements, Code Developments Pot indicated that this pot could be responsible for the beam screen regulation issues. It was indeed found out that the ferrites of this TOTEM pot had not been baked out and that some ferrites were damaged. During LS1 the valves for standalones were replaced to allow a higher cooling flux. Roman Pots to be used at high luminosities were equipped with RF shields to reduce the impedance, and new high Curie temperature ferrites were installed after proper bake-out. ATLAS-ALFA Roman Pot During Run 1, the ATLAS-ALFA detectors’ temperature entered the range that is expected to lead to detector damage. Ferrites were relocated far from the beam and closer to an active cooling circuit, while an additional electromagnetic shielding was installed to reduce the longitudinal impedance of the pots (see Fig. 1). Figure 1: ATLAS-ALFA Roman Pot before LS1 (left) and optimized from longitudinal impedance point of view after LS1 (right). Old and new ferrites are not shown. Courtesy Sune Jakobsen. It is important to note that other hardware that were affected by heating issues before LS1 were also removed (vacuum modules VMTSA and two beam tertiary collimators TCTVB). Heating Monitoring Tools Additional monitoring tools were implemented for the LHC Run 2 to detect abnormal beam induced heating [8]. These include additional temperature probes for target hardware (e.g. TDI, goniometer, BGI, BGV, ALICE beam pipe), systematic logging of temperature data into the logging databases, fixed displays on the operation consoles for efficient monitoring, vocal and text message warnings if the temperature reaches predefined levels. This strategy paid off as it allowed for instance to detect, analyse, diagnose and solve a non-conformity with the cooling circuit of a collimator at a very early stage, before it could become a limitation [9]. Issues with temperature probes were also diagnosed by careful monitoring of their evolution during beam intensity ramp-up: several probes measured unphysical values during beam presence (very abrupt temperature variations for large massive devices), and studies will be launched to assess the causes for the perturbations [8, 9]. EXPECTATIONS FOR 2015 The beam conditions after LS1 (up to 2748 bunches spaced by 25 ns with close to nominal bunch population of 1.15 10 protons per bunch (p/b) at 6.5 TeV and similar bunch length as 2012) were not expected to yield a significant increase of beam induced RF power loss for equipment with a broadband longitudinal impedance spectrum, but the impact on narrow band impedances excited by the 50 ns beam before LS1 was expected to be “double or quits” with the switch to 25 ns beam in 2015 [3]. RESULTS IN 2015 A summary of beam induced RF heating issues for 2015 is provided in Table 1. It can be seen that the effort provided by all teams involved paid off: all blocking issues, with the notable exception of the TDI, disappeared. The reduction in temperature increase was decisive for the new designs of the BSRT (for which almost no temperature increase could be observed in 2015), ATLAS-ALFA (for which the maximum temperature remained far from the danger zone, see Fig. 2). The new collimator design with embedded ferrites (TCTP, TCSP) have also shown no significant difference in 2015 with respect to the design without ferrite. No vacuum issue was observed near TOTEM Roman pots despite regular insertions to 3-4 mm from the beam during high luminosity physics fills [10]. Table 1: Summary of LHC Equipment Heating in Run 1, Prospects for 2015 before the run and what really happened LHC device Problem Run 1 Expected 2015 What happened in 2015

The International Axion Observatory (IAXO) is a proposed 4th-generation axion helioscope with the primary physics research goal to search for solar axions via their Primakoff conversion into photons of 1 – 10 keV energies in a strong magnetic field. IAXO will achieve a sensitivity to the axion-photon coupling gaγ down to a few ×10−12 GeV−1 for a wide range of axion masses up to ∼ 0.25 eV. This is an improvement over the currently best (3rd generation) axion helioscope, the CERN Axion Solar Telescope (CAST), of about 5 orders of magnitude in signal strength, corresponding to a factor ∼ 20 in the axion photon coupling. IAXO's sensitivity relies on the construction of a large superconducting 8-coil toroidal magnet of 20 m length optimized for axion research. Each of the eight 60 cm diameter magnet bores is equipped with x-ray optics focusing the signal photons into ∼ 0.2 cm2 spots that are imaged by very low background x-ray detectors. The magnet will be built into a structure with elevation and azimuth drives that will allow solar tracking for 12 hours each day. This contribution is a summary of our papers [1], [2], [3] and we refer to these for further details.

As the AD programme now faces a renewed lease of life following the start of the ELENA project, it is essential to ensure best possible reliability and performance for the next 20 years or so. The AD machine, which was started in 1999, is based on the Antiproton Collector (AC) ring of the Antiproton Accumulator Complex (AAC) which in turn was constructed in the mid-80:ies. Since most of the major AD components were retained from the AC, we now have a significant amount of 30-year old equipment to deal with.LEIR is in a similar situation having started life in the 80s, supplying antiproton beams at various energies for the PS physics programme. After having been transformed into a heavy ion accumulator in 2004 and subsequently used in operation, some consolidation needs have become apparent. LEIR is expected to keep delivering heavy ions to the North Area and to the LHC until 2035, and possibly light ions to a new biology research facility in the South Hall.A consolidation programme is underway for both machines and here we will discuss the main aspects of ongoing and planned activities from an operational point of view.

The IAXO (International Axion Experiment) is a fourth generation helioscope with a sensitivity, in terms of detectable signal counts, at least 104 better than CAST phase-I, resulting in sensitivity on g, one order of magnitude better. To achieve this performance TAXO will count on a 8-coil toroidal magnet with 60 cm diameter bores and equipped with X-ray focusing optics into 0.20 cm(2) spots coupled to ultra-low background Micromegas X-ray detectors. The magnet will be on a platform that will allow solar tracking for 12 hours per day. The next short term objectives are to prepare a Technical Design Report and to construct the first prototypes of the hardware main ingredients: demonstration coil, X-ray optics and low background detector while refining the physics case and studying the feasibility studies for Dark Matter axions.

Following the significant impedance related issues that occurred during the LHC Run 1, all involved equipment groups made an impressive effort to assess and reduce the impedance of their near-beam components. Concerning beam induced RF heating, many problems in Run 1 were linked to unexpected non-conformities. Mitigations were put in place but new non-conformities are likely to appear in Run 2, and this is why efficient monitoring and alarms are currently put in place. Besides, known limitations that led to increase the bunch ength from 1 ns to 1.25 ns were removed, which would open the possibility to try and reduce the target bunch length at top energy. Regardless of the target bunch length, many components will need careful follow up in 2015 (e.g. TDI, BSRT, Roman pots, MKI, BGV). Concerning the LHC impedance, announced hardware changes are expected to be transparent, but the new TCTP and TCSP collimators with BPMs and ferrites should be monitored closely, as well as the modified Roman pots, new TCL4 and especially new TCL6 collimators if they approach the beam with very low gaps at high beam intensity.

The impedance is a complex function of frequency, which represents, for the plane under consideration (longitudinal, horizontal or vertical), the force integrated over the length of an element, from a "source" to a "test" wave, normalized by their charges. In general, the impedance in a given plane is a non-linear function of the test and source transverse coordinates, but it is most of the time sufficient to consider only the first few linear terms. Impedances can influence the motion of trailing particles, in the longitudinal and in one or both transverse directions, leading to energy loss, beam instabilities, or producing undesirable secondary effects such as excessive heating of sensitive components at or near the chamber wall, called beam-induced RF heating. The LHC performance limitations linked to impedances encountered during the 2010-2012 run are reviewed and the currently expected situation during the HL-LHC era is discussed.

The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO will look for axions or axion-like particles (ALPs) originating in the Sun via the Primakoff conversion of the solar plasma photons. In terms of signal-to-noise ratio, IAXO will be about 4–5 orders of magnitude more sensitive than CAST, currently the most powerful axion helioscope, reaching sensitivity to axion-photon couplings down to a few × 10−12 GeV−1 and thus probing a large fraction of the currently unexplored axion and ALP parameter space. IAXO will also be sensitive to solar axions produced by mechanisms mediated by the axion-electron coupling gae with sensitivity — for the first time — to values of gae not previously excluded by astrophysics. With several other possible physics cases, IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade. In this paper we present the conceptual design of IAXO, which follows the layout of an enhanced axion helioscope, based on a purpose-built 20 m-long 8-coils toroidal superconducting magnet. All the eight 60cm-diameter magnet bores are equipped with focusing x-ray optics, able to focus the signal photons into ∼ 0.2 cm2 spots that are imaged by ultra-low-background Micromegas x-ray detectors. The magnet is built into a structure with elevation and azimuth drives that will allow for solar tracking for ∼ 12 h each day.

Bench measurements nowadays represent an important tool to estimate the coupling impedance of any particle accelerator device. The well-known technique based on the coaxial wire method allows to excite in the device under test a field similar to the one generated by an ultra-relativistic point charge. We discuss the basics of the coaxial wire method and review the formulae widely used to convert measured scattering parameters to longitudinal and transverse impedance data. We review, as well, bead-pull technique used in the design, construction and tuning of multi-cell accelerating structures. We discuss typical measurement examples of interest for the CERN Large Hadron Collider as well as other state of the art particle accelerator.

The spectrum of long bunches injected into the ring with RF switched o has been used in the SPS in the past to probe the longitudinal coupling impedance. After a large campaign of shielding of 800 inter-magnet vacuum ports in 1999 - 2001, the microwave instability threshold was significantly increased and the high-frequency spectrum of the beam became practically flat, apart from a prominent peak at around 1.4 GHz. As corresponding high-frequency impedance could potentially lead to microwave instability of high intensity bunches observed now at high energies in the SPS, a search of the source of this impedance was launched. Using a combination of impedance simulations and measurements, vacuum flanges that are present in a large quantity in the machine have been identified as a main source of impedance at this frequency. Particle simulations based on the SPS impedance model, which includes this previously unknown impedance, are able to reproduce the characteristics of the bunch spectrum and amplitude growth rates and hence, confirm that the impedance of the vacuum flanges is responsible for the observed spectral peak.