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The proposed SPS Wideband Transverse Feedback sys- tem requires a wide-band pick-up system to be able to de- tect intra-bunch motion within the SPS proton bunches, captured and accelerated in a 200 MHz bucket. We present the electro-magnetic design of transverse beam position pick-up options optimised for installation in the SPS and evaluate their performance reach with respect to direct time domain sampling of the intra-bunch motion. The analy- sis also discusses the achieved subsystem responses of the associated cabling with new low dispersion smooth wall coaxial cables, wide-band generation of intensity and posi- tion signals by means of 180 degree RF hybrids as well as passive techniques to electronically suppress the beam off- set signal, needed to optimise the dynamic range and posi- tion resolution of the planned digital intra-bunch feedback system.

We present experimental measurements taken from CERN SPS machine development studies with a wideband intra-bunch feedback channel prototype. The demonstration system is a digital processing system with recently installed wideband kicker and amplifier components. This new hardware extends the bandwidth up to 1GHz and allows driving and controlling multiple vertical transverse modes in the bunch. The studies are focused on both driving the bunch with spectrally controlled signals to identify a reduced model of the bunch dynamics and testing model-based feedback controllers to stabilize the bunch dynamics. The measurements are structured to validate reduced MIMO models and macro-particle simulation codes, including the dynamics and limits of the feedback channel. Noise effects and uncertainties in the model are evaluated via SPS measurements to quantify the limits of control techniques applied to stabilize the intrabunch dynamics. The design of controllers for Q26 and Q20 optics are illustrated and future control developments are described.

Measurements of the bunch peak amplitude using the longitudinal wideband wall-current monitor are a vital tool used in the Large Hadron Collider (LHC) beam observation system. These peak-detected measurements can be used to diagnose bunch shape oscillations, for example coherent quadrupole oscillations, that occur at injection and during beam manipulations. Peak-detected Schottky diagnostics can also be used to obtain the synchrotron frequency distribution and other parameters from a bunched beam under stable conditions. For the LHC a beam-synchronous gated peak detector has been developed to allow individual bunches to be monitored without the influence of other bunches circulating in the machine. The requirement for the observation of both low intensity pilot bunches and high intensity bunches for physics requires a detector front-end with a high bandwidth and a large dynamic range while the usage for Schottky measurements requires low noise electronics. This paper will present the design of this detector system as well as initial results obtained during the 2012- 2013 LHC run.

The LHC Beam Quality Monitor is a system that measures individual bunch lengths and positions, similarly to the twin system SPS Beam Quality Monitor, from which it was derived. The pattern verification that the system provides is vital during the injection process to verify the correctness of the injected pattern, while the bunch length measurement is fed back to control the longitudinal emittance blow up performed during the energy ramp and provides a general indication of the health of the RF system. The algorithms used, the hardware implementation and the system integration in the LHC control infrastructure are presented in this paper, along with possible improvements.

Heat load on beam screens, collimators and injector kickers can limit the maximum beam intensity in the LHC. Longer bunches reduce this effect and can give other benefits (e.g. for e-cloud). However, an increase in particle losses could also be expected. The goal of this MD was to determine a correlation between losses and bunch length on the LHC flat top. We injected 8 bunches per ring with nominal emittance (0.5 eVs) and nominal intensity (1.15x10^11 pp) and accelerated them to 3.5 TeV, where a controlled longitudinal emittance blow-up was applied, giving a spread in bunch lengths (measured by BQM) in the range 1.15-1.65 ns. Then, bunches were observed for one hour at flat top and correlation between losses and bunch length is presented. At the end of the study, voltage was reduced to further increase bunch lengths. Phase measurements were also acquired in parallel and described here.

Loss of Landau damping leading to a single bunch longitudinal instability has been observed in the LHC during the ramp and on the 3.5 TeV flat top for small injected longitudinal emittances. The first measurements are in reasonable agreement with the threshold calculated for the expected longitudinal reactive impedance budget of the LHC as well as with the threshold dependence on beam energy. The cure is a controlled longitudinal emittance blow-up during the ramp which for a constant threshold through the cycle should provide an emittance proportional to the square root of energy.

The goal of this MD was to study a single bunch longitudinal instability observed during the acceleration ramp in the LHC in 2010 for bunches with nominal intensity and small injected longitudinal emittance. During this MD there were two fills, the first without acceleration and the second with acceleration. In the first each ring was filled with 8 high intensity bunches with small longitudinal emittance. During the second 8 high intensity bunches were injected into each ring with longitudinal emittances varying from 0.9 eVs to 0.3 eVs. Two longitudinal instability modes (dipole and quadrupole) were observed in different parts of the cycle with both beams. Measurements of phase and bunch length oscillations, as well as data extracted from bunch profile acquisitions during the cycle, are presented in this Note together with an analysis of the growth rate dependence on bunch emittances and intensity.

Hardware commissioning of the LHC RF system was successfully completed in time for first beams in LHC in September 2008. All cavities ware conditioned to nominal field, power systems tested and all Low level synchronization systems, cavity controllers and beam control electronics were tested and calibrated. Beam was successfully captured in ring 2, cavities phased, and a number of initial measurements made. These results are presented and tests and preparation for colliding beams in 2009 are outlined.

Hardware commissioning of the LHC RF Systems, the ACS Superconducting RF systems, ADT Transverse Dampers and APWL Wideband Longitudinal Monitors, started in late 2007 and was completed in time for the first LHC beams in 2008. The RF inter-machine synchroni-sation systems were in place and operational for the LHC synchronization tests in August 2008. The very first beams through IP4 were observed on the RF monitors and beam 2 was captured on 11th September. Measurements with beam on the damper systems were also pos-sible, preparing the way for closing the damper loop with beam. Major milestones during commissioning the ACS and ADT systems and results obtained during first capture tests are presented. Preparatory work for acceleration and multi-bunch operation is described as are the beam tests foreseen for 2009.

The commissioning of CERN's ion injector complex [1] to allow 1.1 PeV collisions of ions in LHC is well under way. After the Low Energy Ion Ring (LEIR) in 2005 [2] and the Proton Synchrotron (PS) in 2006 [3], the Super Proton Synchrotron (SPS) has now been commissioned with the 'Early' ion beam, which should give a luminosity of $5×10^{25}cm^{-2}s^{-1}$ in the LHC. This paper summarizes the operation in 2007 of all the machines involved in the ion injection chain.

During the machine development session of 2007-10-03, the energy matching between PS and SPS was completed for the 208Pb82+ beam. The I-LHC RF low level, including the phase loop and the synchronisation loop, was commissioned to capture a single bunch of 208Pb82+. After commissioning, the beam was used for several non RF related machine developments.

Without specific counter measures, the LHC type beam in the SPS suffers from longitudinal coupled bunch instabilities. To get rid of them, the SPS impedance has been decreased in the last years and the operation of a high frequency Landau damping system has been established. In case of the absence of this Landau damping system one may alternatively introduce an RF amplitude modulation to stabilize the beam. We present results obtained by this method in the SPS and considerations for a potential increase of the longitudinal stability of the LHC.

The SPS master timing generator is foreseen to be replaced in 2004 by a central timing generator called CBCM, which will control the whole accelerator complex. At this occasion a working group has been created to review the actual SPS timing events and how it could fit in with the new MTG. It has been decided that a rationalization and simplification of the events was necessary in order that the events are manageable by the CBCM. At the end of the 2003 run, the cleaned-up events have been tested with the SPS MTG. Then the CBCM has been plugged to generate the same events. The tests and their results are described in this document.

The first dedicated MD session in 2003 was mainly used to reestablish the situation achieved at the end of last year when stable LHC beam with nominal parameters was obtained on the flat top. To stabilise the beam the 800~MHz RF system was used during the cycle in bunch shortening mode together with controlled emittance blow-up. This year emittance blow-up during the ramp was performed using excitation at the synchrotron frequency via the phase loop of the 200~MHz RF system. No beam loss was observed with this method. Some part of MD time was devoted to studies of localised (affecting only a few bunches) dipole instability seen on phase discriminator of the longitudinal damper on the flat bottom and during the ramp. This instability was not noticed last year.

In 2003 we have to provide Indium beam for the SPS fixed target experiments for the first time. There are essentially two possibilities to accelerate In ions in the PS, one without crossing transition before extraction and one with crossing transition. These two possibilities are evaluated and a strategy for the start-up is suggested.

After acceleration to 450 GeV/c in the SPS, the proton beams for the LHC must be rephased in order to be injected into the correct place in the collider. If the position before rephasing is random, th e beam must be rotated by up to 1/14th of an SPS turn. This procedure will take about 330 ms on the flat top. Besides lengthening the cycle, the beam may deteriorate if instabilities develop during th is long process. We present a beam control system that reduces the rotation angle needed and which has been successfully tested in the SPS.

The old SPS RF control system designed in 1972 has been replaced completely, i.e. both hardware and software. The new system has to control both RF equipment conceived during the last 23 years and future (modern) equipment. Using information analysis methods, we derived a model of an RF command and designed a data base accordingly (ORACLE®). Information from this data base is used for command generation and processing and also for archiving settings. The advantage is purely generic software, i.e. the same computer code is used for switching on an RF amplifier, as for setting a frequency synthesizer. New equipment is added very simply by entering new records in the data base. Additional features include a reservation scheme whereby a user can take private control of any piece of equipment, a reporting facility notifying the user of the simultaneous control activity by other users on RF equipment, and a capability scheme assigning a level of expertise to each user restricting action on the equipment.

The LHC RF system commissioning with beam and physics operation for 2010 and 2011 are presented. It became clear in early 2010 that RF noise was not a lifetime limiting factor: the crossing of the much feared 50 Hz line for the synchrotron frequency did not affect the beam. The broadband LHC RF noise is reduced to a level that makes its contribution to beam diffusion in physics well below that of Intra Beam Scattering. Capture losses are also under control, at well below 0.5%. Longitudinal emittance blow-up, needed for ramping of the nominal intensity single bunch, was rapidly commissioned. In 2011, 3.5 TeV/beam physics has been conducted with 1380 bunches at 50 ns spacing, corresponding to 55% of the nominal current. The intensity per bunch (1.3 1011 p) is significantly above the nominal 1.15 1011. By August 2011 the LHC has accumulated more than 2 fb-1 integrated luminosity, well in excess of the 1 fb-1 target for 2011.

The first LHC Pb ion run took place at 1.38 A TeV/c per beam in autumn 2010. After a short period of runningin, the injector chain was able to fill the collider with up to 137 bunches per ring, with an intensity of 108 Pb82+ ions/bunch, about 50% higher than the design value. This yielded a luminosity of 3×1025 Hz/cm2, allowing the experiments to accumulate just under 10 b-1 each during the four week run. We review the performance of the individual links of the injector chain, and address the main issues limiting the LHC luminosity, in view of reaching 1026 Hz/cm2 in 2011, and substantially beyond when the LHC energy increases after the long shutdown in 2013-14.