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Linear accelerator 4 (Linac4) is designed to accelerate negative hydrogen ions for injection into the Proton Synchrotron Booster (PSB). It will become the source of proton beams for the Large Hadron Collider (LHC) after the long shutdown in 2019–2020. Linac4 will accelerate H– ions, consisting of a hydrogen atom with an additional electron, to 160 MeV energy and then inject them into the PSB, which is part of the LHC injection chain. The new accelerator comprises an ion source and four types of accelerating structures. The particles are accelerated first to 3 MeV energy by a Radio-Frequency Quadrupole (RFQ), then to 50 MeV by three Drift Tube Linacs (DTL) tanks, then to 100 MeV by seven Cell-Coupled Drift Tube Linac (CCDTL) modules, and finally to 160 MeV by twelve Pi-Mode Structures (PIMS). A chopper line placed between the RFQ and the first DTL tank modulates the linac beam at the PSB injection frequency. Linac4 includes transfer and measurement lines up to the PSB injection, where the ions are stripped of their two electrons to leave only protons. Linac4 is 76 metres long and located 12 metres below ground. The first low-energy beams were produced in 2013 and after the commissioning of all accelerating structures the milestone energy of 160 MeV was reached in 2016. Linac4 will be connected to the PSB during the long shutdown of 2019–20, after which it will replace the 50 MeV Linac2 as source of protons for the LHC. The Linac4 is a key element in the project to increase the luminosity of the LHC during the next decade.

The presented document if the Letter of Intent for the Gamma Factory Proof-of-Principle Experiment.

This paper describes the first results of a feasibility study undertaken at CERN to determine whether a laser-produced plasma can be used as a source of intense highly charged heavy ion beams. A variety of important measurements have been made, and the results are encouraging. Furthermore, a beam of highly charged light ions produced by the laser ion source has been accelerated successfully in a radio frequency quadrupole (RFQ) structure

To deliver B3+ ions for medical research the compounds decaborane and m-carborane were tested using the metal ions from volatile compounds (MIVOC) method with the Supernanogan 14.5 GHz ECR ion source. Using decaborane the source delivered less than 10 A intensity of B3+ and after operation large deposits of material were found inside the source. Using m-carborane 50 A of B3+ were delivered without support gas. For m-carborane, helium and oxygen support gasses were also tested, and the effects of different source tuning parameters are discussed. The average consumption of m-carborane was 0:1 mg/Ah over all operation.

A comprehensive study of beam formation and beam transport has been initiated in order to improve the performance of the CERN heavy ion injector, Linac3. As part of this study, the ion beam extraction system of the CERN GTS-LHC 14.5 GHz Electron Cyclotron Resonance Ion Source (ECRIS) has been modelled with the ion optical code IBSimu. The simulations predict self-consistently the triangular and hollow beam structures which are often observed experimentally with ECRIS ion beams. The model is used to investigate the performance of the current extraction system and provides a basis for possible future improvements. In addition, the extraction simulation provides a more realistic representation of the initial beam properties for the beam transport simulations, which aim to identify the performance bottle necks along the Linac3 low energy beam transport. The results of beam extraction simulations with Pb and Ar ion beams from the GTS-LHC will be presented and compared with experimental observations.

In this chapter, the anatomy of an ion source is briefly described, as well as a few features of particle motion in electric and magnetic fields, and of particle dynamics and plasmas. Using this information, different types of ion sources are described, highlighting their main mode of operation., Comment: 18 pages, contribution to the CAS-CERN Accelerator School: Ion Sources, Senec, Slovakia, 29 May - 8 June 2012, edited by R. Bailey, CERN-2013-007

Ion sources produce beams for a large variety of different physical experiments, industrial processes and medical applications. In order to characterize the beam delivered by them, a list of requirements is necessary. In this chapter the list of principal requirements is specified and definitions for them are given., Comment: 8 pages, contribution to the CAS-CERN Accelerator School: Ion Sources, Senec, Slovakia, 29 May - 8 June 2012, edited by R. Bailey, CERN-2013-007

The potential for a superconducting proton linac (SPL) at CERN started to be seriously considered at the end of the 1990s. In the first conceptual design report (CDR), published in 2000 [1], most of the 352 MHz RF equipment from LEP was re-used in an 800 m long linac, and the proton beam energy was limited to 2.2 GeV. During the following years, the design was revisited and optimized to better match the needs of a high-power proton driver for neutrino physics. The result was a more compact (470 m long) accelerator capable of delivering 5 MW of beam power at 3.5 GeV, using state-of-the-art superconducting RF cavities at 704 MHz. It was described in a second CDR, published in 2006 [2]. Soon afterwards, when preparation for increasing the luminosity of the LHC by an order of magnitude beyond nominal became an important concern, a low-power SPL (LP-SPL) was studied as a key component in the renovation of the LHC injector complex. The combination of a 4 GeV LP-SPL injecting into a new 50 GeV synchrotron (PS2) was proposed to replace the ageing Linac2, PSB, and PS. In a later stage, if necessary for future physics programmes (neutrino production or generation of radioactive ion beams), the linac could be brought up to multimegawatt beam power by upgrading the cooling, the electrical infrastructure, and the power supplies. The construction of the low-energy front end of the LP-SPL started in 2008 as the Linac4 project [3], aimed at the replacement of Linac2, with the potential for being adapted later to the needs of a low-power or high-power SPL (HP-SPL). In parallel, the R&D on the superconducting linac continued, initially to refine the design of the LP-SPL and afterwards that of the HP-SPL. This report presents the design of the LP-SPL and the work accomplished in preparing a proposal for new LHC injectors with the support of the European Commission under the Framework Programmes 6 and 7 and in collaboration with multiple laboratories and institutions worldwide. The status of the R&D towards an HP-SPL is summarized.

In the light of different running scenarios potential source improvements will be discussed (e.g. one month every year versus two month every other year and impact of the different running options [e.g. an extended ion run] on the source). As the oven refills cause most of the down time the oven design and refilling strategies will be presented. A test stand for off-line developments will be taken into account. Also the implications on the necessary manpower for extended runs will be discussed.

Linac4 is a normal-conducting 160 MeV H- linear accelerator, presently under construction, that will replace the present 50 MeV Linac2 as injector of the CERN proton accelerator complex with the goal of increasing the LHC luminosity. The Linac4 front-end, composed of a 45 keV ion source, a Low Energy Beam Transport (LEBT), a 352.2 MHz Radio Frequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) housing a beam chopper, was commissioned at the 3 MeV test stand area during the first half of 2013. This report gives details of the installation and operational systems used, describes the commissioning phases and measurements performed and summarizes the results that were finally achieved and the lessons learnt in the process.

During an intensity optimisation routine of Linac3 on November 23rd, we discovered that a phase change of tank 2 has a beneficial effect for the LEIR extracted beam intensity, despite an unchanged beam intensity from Linac3 to LEIR.

Since 2010 the GTS-LHC source delivers lead ions for heavy ion physics at the LHC. Several modifications allowed the improvement the source reliability and the beam stability. The attempts to improve the beam intensity were less successful. The different modifications and actual performance figures will be presented in this paper. In addition to the heavy ion physics program of the LHC new ion species will be requested for different experiments in the future. The fixed target experiment NA61 requires primary argon and xenon beams. And a future biomedical facility asks for light ions in the range helium to neon. Approaches to prepare these beams and to modify the ion injector towards a light ion front end are presented.

Linac4 is a 160 MeV normal-conducting linear accelerator for negative Hydrogen ions (H−), which will replace the 50 MeV proton Linac (Linac2) as linear injector for the CERN accelerators. The low energy part, comprising a 45 keV Low Energy Beam Transport system (LEBT), a 3 MeV Radiofrequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) is being assembled in a dedicated test stand for pre-commissioning with a proton beam. During 2011 extensive measurements were done after the source and after the LEBT with the aim of preparing the RFQ commissioning and validating the simulation tools, indispensable for future source upgrades. The measurements have been thoroughly simulated with a multi-particle code, including 2D magnetic field maps, error studies, steering studies and the generation of beam distribution from measurements. Emittance, acceptance and transmission measurements will be presented and compared to the results of the simulations.

During the past decade, intense experimental studies on the heavy-ion induced molecular desorption were performed in several particle accelerator laboratories worldwide in order to understand and overcome large dynamic pressure rises caused by lost beam ions. Different target materials and various coatings were studied for desorption and mitigation techniques were applied to heavy-ion accelerators. For the upgrade of the CERN injector complex, a coating of the Super Proton Synchrotron (SPS) vacuum system with a thin film of amorphous carbon is under study to mitigate the electron cloud effect observed during SPS operation with the nominal proton beam for the Large Hadron Collider (LHC). Since the SPS is also part of the heavy-ion injector chain for LHC, dynamic vacuum studies of amorphous carbon films are important to determine their ion induced desorption yields. At the CERN Heavy Ion Accelerator (LINAC 3), carbon-coated accelerator-type stainless steel vacuum chambers were tested for desorption using 4.2 MeV/u Pb54+ ions. We describe the experimental setup and method, present the results for unbaked and baked films, and summarize surface characterizations such as secondary electron yield measurements, x-ray photoemission spectroscopy, and scanning electron microscopy studies. Finally, we present a high-energy scaling of lead-ion induced desorption yields from the MeV/u to GeV/u range.

During the past decade, intense experimental studies on the heavy-ion induced molecular desorption were performed in several particle accelerator laboratories worldwide in order to understand and overcome large dynamic pressure rises caused by lost beam ions. Different target materials and various coatings were studied for desorption and mitigation techniques were applied to heavy-ion accelerators. For the upgrade of the CERN injector complex, a coating of the Super Proton Synchrotron (SPS) vacuum system with a thin film of amorphous carbon is under study to mitigate the electron cloud effect observed during SPS operation with the nominal proton beam for the Large Hadron Collider (LHC). Since the SPS is also part of the heavy-ion injector chain for LHC, dynamic vacuum studies of amorphous carbon films are important to determine their ion induced desorption yields. At the CERN Heavy Ion Accelerator (LINAC 3), carbon-coated accelerator-type stainless steel vacuum chambers were tested for desorption using 4.2 MeV/u Pb^{54+} ions. We describe the experimental setup and method, present the results for unbaked and baked films, and summarize surface characterizations such as secondary electron yield measurements, x-ray photoemission spectroscopy, and scanning electron microscopy studies. Finally, we present a high-energy scaling of lead-ion induced desorption yields from the MeV/u to GeV/u range.

The H- source and the low energy beam transport(LEBT) line will determine to a large extend the performance of Linac-4, the new machine foreseen at CERN as injector into the PS Booster. For this reason a test stand is being set up, consisting of the source, the LEBT, the RFQ and the chopper line. Up to now only the source and LEBT are installed. First measurements have been performed using a Faraday Cup to measure the total source intensity, a slit and grid emittance meter for transverse emittance measurements as well as a spectrometer for energy spread measurements. Beam intensity, profile, transverse emittance and energy spread have been measured. The paper discusses measurements done on H- beams at 35 kV extraction voltage as well as proton beams at 45 keV.

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.

The new GTS-LHC ECR ion source was installed in 2005. An oxygen 4+ beam was delivered to LEIR both for injection line (June 2005) and for the ring commissioning (September to December 2005). During these runs, studies were made of the beam transport in the Linac and towards LEIR. Some of the most significant results concerning the Linac are presented in this report. From 2006 the ECR source and the Linac3 delivered a lead beam for the LEIR commissioning, leaving some questions open for the oxygen beam transport. This report serves as a summary of the status of the investigations on the oxygen beam.

The GTS-LHC ion source, designed and build by CEA Grenoble, was installed and commissioned at CERN in 2005. Since than the source has delivered oxygen and lead ion beams (O4+ and Pb27+ from the source, Pb54+ from the linac) for the commissioning of the Low Energy Ion Ring (LEIR). Results of this operation and attempts to improve the source performance and reliability, and the linac performance will be presented in this paper.

Future requirements on higher beam intensity and brightness will need an upgrade of the present CERN accelerator chain. Linac4 will be an essential part of the upgrade of the proton accelerator facility. The source for this H- linac will be based on a copy of the DESY RF driven H- source. New possible RFQ alternatives (with different injection energies) and a pressing linac schedule made it necessary to develop a flexible two-source-design.

Linac4 is an H- linear accelerator, intended to replace Linac2 as injector to the PS Booster (PSB). By delivering to the PSB a beam at 160 MeV energy, Linac4 will provide the conditions to double the brightness and intensity of the beam from the PSB, thus removing the first bottleneck towards higher brightness for the LHC and simplifying operation. Moreover, this new linac constitutes an essential component of any of the envisaged LHC upgrade scenarios and could open the way to future extensions of the CERN accelerator complex towards higher performance. This Technical Design Report presents a detailed technical overview of the Linac4 design as it stands at end 2006.

The CERN Low Energy Ion Ring (LEIR) commissioning started in the year 2005. O4+and Pb54+ion beams are transferred at 4.2 MeV/nucleon from Linac 3 to LEIR through a low energy transfer line, for which the constraints and the resulting optics design are presented. First trajectory and dispersion measurements agreed only poorly with the theoretical model. Iterations of a refined optics model and further measurements improved the agreement between experimental observations and expectations. In particular, the effect of quadrupole errors in the line dipole magnets is discussed.

A brief introduction to electron and ion sources for particle accelerators is given. Concentrating on the basic processes for the production of these particles, thermionic and photocathode production of electrons and the processes in Penning and electron cyclotron resonance ion sources are covered. Finally, negative ions are discussed.

LPSc-acc; An analysis of the revised physics needs and recent progress in the technology of supreconducting RF cavities have led to major changes in the specification and in the design for a Superconducting Proton Linac (SPL) at CERN. Compared with the first conceptual design report (CERN 2000-012) the beam energy is almost doubled (3.5 GeV instead of 2.2 GeV), while the length of the linac is reduced by 40% and the repetition rate is reduced to 50 Hz. The basic beam power is at a level of 4-5 MW and the approach chosen offers enough margins for upgrandes. With this high beam power, the SPL can bethe proton driver for an ISOL-type radioactive ion beam facility of the next generation (EURISOL), and for a neutrino facility based on superbeam + beta-beam or on muon decay in storage ring (neutrino factory). The SPL can also replace the Linac2 and PS Booster in the low-energy part ofthe CERN proton accelerator complex, improving significantly the beam performance in terms of brightness and intensity for the benefit of all users including the LHC and its luminosity upgrade. Decommissioned LEP klystrons and RF equipment are used to provide RF power at a frequency of 352.2 MHz in the low-energy part of the accelerator. Beyond 90 MeV, the RF frequency is doubled to take advantage of more compact normal-conducting accelerating structures up to an energy of 180 MeV. From there, state-of-the-art, high-gradient, bulk-niobium superconducting cavities accelerate the beam up to its final energy of 3.5 GeV. The overall design approach is presented, together with the progress that has been achieved since the publication of the first conceptual design report.

It has been observed on different machines that scintillating ceramic screens (like chromium doped alumina) are quickly damaged by low energy ion beams. These particles are completely stopped on the surface of the screens, inducing both a high local temperature increase and the electrical charging of the material. A study has been initiated to understand the limiting factors and the damage mechanisms. Several materials, ZrO2, BN and Al2O3, have been tested at CERN on LINAC3 with 4.2MeV/u lead ions. Alumina (Al2O3) is used as the reference material as it is extensively used in beam imaging systems. Boron nitride (BN) has better thermal properties than Alumina and Zirconium oxide (ZrO2). BN has in fact the advantage of increasing its electrical conductivity when heated. This contribution presents the results of the beam tests, including the post-mortem analysis of the screens and the outlook for further measurements. The strategy for the choice of the screens for the Low Energy Ion Ring (LEIR), currently under construction at CERN, is also explained.

This specification, drawn up by the instrumentation specification board 2, describes the requirements concerning orbit and trajectory measurements in the PS machine. The orbit measurement and the trajectory measurement are both indispensable in order to be able to guarantee the correct beam quality for beams like LHC, the future Grand Sasso beam, the nTOF beam and surely the combined operation of the nTOF beam and the East Area beam.

Future CERN programmes for LHC and ISOLDE require increasing the beam intensity and brightness from the PS Booster (PSB). This could be achieved by injection from a higher energy H- linac. A new injector will require a high performance, high reliability, negative hydrogen ion source. This paper will present the requirements for such a source together with the first results for a prototype microwave driven source. This work is supported by the European Commission under contract n° HPRI-CT-2001-50021

Future high intensity ion accelerators, including the Spallation Neutron Source (SNS), the European Spallation Source (ESS), the Superconducting Proton Linac (SPL) etc, will require high current and high duty factor sources for protons and negative hydrogen ions. In order to achieve these goals, a comparison of the Electron Cyclotron Resonance, radio-frequency and Penning ion sources, among others, will be made. For each of these source types, the present operational sources will be compared to the state-of-the-art research devices with special attention given to reliability and availability. Finally, the future research and development aims will be discussed.

Laser Ion Sources (LIS) are well suited to filling synchrotron rings with highly charged ions of almost any element in a single turn injection mode. We report the first measurements of the LIS output parameters for Pb27+ ions generated by the new 100 J/1 Hz Master Oscillator - Power Amplifier CO2-laser system. A new LIS has been designed, built and tested at CERN, as an ion source for ITEP-TWAC accelerator/accumulator facility, and as a possible future source for an upgrade of the Large Hadron Collider (LHC) injector chain. The use of the LIS based on 100 J/1 Hz CO2-laser together with the new ion LINAC, as injector for ITEP-TWAC project, is discussed..

A sizeable part of the LHC physics programme foresees lead-lead collisions with a design luminosity of 1027 cm-2 s-1. This will be achieved after an upgrade of the ion injector chain comprising Linac3, LEIR, PS and SPS machines [1,2]. Each LHC ring will be filled in 10 min by almost 600 bunches, each of 7×107 lead ions. Central to the scheme is the Low Energy Ion Ring (LEIR) [3,4], which transforms long pulses from Linac3 into high-brilliance bunches by means of multi-turn injection, electron cooling and accumulation. Major limitations along the chain, including space charge, intrabeam scattering, vacuum issues and emittance preservation are highlighted. The conversion from LEAR (Low Energy Antiproton Ring) to LEIR involves new magnets and power converters, high-current electron cooling, broadband RF cavities, and a UHV vacuum system with getter (NEG) coatings to achieve a few 10-12 mbar. Major hardware changes in Linac3 and the PS are also covered. An early ion scheme with fewer bunches (but each at nominal intensity) reduces the work required for early LHC ion operation in spring 2008.

In the framework of CERN Linac 3 restudy, the possibility of accelerating several charge states is studied. The validation of the simulation codes by measurements, the studies of the multi charge beam behaviour in each part of the CERN Linac 3 is described. The study ends with the "end to end" simulation results for single charge (nominal) and multi charge configuration of CERN Linac 3, thus determining the gain in intensity in the LEIR acceptance if one accelerates several charge states.

In the framework of Linac 3 restudy, emittance, and transmission measurements are taken at all stage of acceleration. The results of these measurements will help to increase the accuracy of beam dynamic simulations. Two methods of calculation of the emittance and Twiss parameters from beam profile measurements are used. Some aspects of the beam dynamic in the LEBT, MEBT and Filter of Linac 3 are highlighted.

The Neutrino Factory is a new concept for an accelerator that produces a high-intensity, high-energy beam of electron and muon neutrinos - the ultimate tool for neutrino oscillation studies and the only machine conceived up today that could help detect CP violation of leptons. The basic concept of the Neutrino Factory is the production of neutrinos from the decay of high-energy muons. Due to their short lifetime, these muons have to be accelerated very fast. Several new accelerator techniques, like a high-intenstiy proton linac, high-power targets, ionization cooling or recirculating muon linacs are required. This paper presents a snapshot of the accelerator design at CERN. Although some aspects of this European Neutrino Factory Scheme have been optimised for the CERN site, the basic principle is site-independent.

CERN's heavy ion pre-injector has been in service since 1994, providing lead ions for fixed target collisions at 177 GeV per nucleon in the SPS. In the LHC era, heavy ion collisions require an increase in the beam brightness, compared to the present injector system of Linac 3, Proton Synchrotron Booster and the Proton Synchrotron. Stacking and cooling ions in a Low Energy Ion Ring should find the largest part of this increase. However, further improvements can be envisaged by upgrading the pre-injector and source. The performance and limitations of the present source and Linac 3 will be discussed, and options for increasing the source brightness will be presented. These options consist of upgrades of the ECR Source to higher frequencies, or its replacement with a Laser Ion Source.

The CERN heavy ion community, and some other high energy physics experiments, are starting to demand other ions, both heavy and light, in addition to the traditional lead ions. Studies of the behaviour of the afterglow for different operation modes of the ECR4 at CERN have been continued to try to understand the differences between pulsed afterglow and continuous operation, and their effect on ion yield and beam reproducibility. The progress in adapting the source and ion beam characteristics to meet the new demands will be presented, as will new information on voltage holding problems in the extraction.

As the pre-injector of the LHC injector chain, the proton linac at CERN is required to provide a high-intensity (180mA) beam to the Proton Synchrotron Booster. The results of measurements at this intensity will be presented. Furthermore, the linac is now equipped with bunch shape monitors from INR, Moscow, which have allowed the comparison of the Alvarez tank RF settings with simulations., LINAC 2000, TUC14, 3 pages, 5 figures

Experimental and theoretical activities are underway at CERN with the aim of examining the feasibility of a very-high-flux neutrino source. In the present scheme, a high-power proton beam (some 4 MW) bombards a target where pions are produced. The pions are collected and decay to muons under controlled optical condition. The muons are cooled and accelerated to a final energy of 50 GeV before being injected into a decay ring where they decay under well-defined conditions of energy and emittance. We present the most challenging parts of the whole scenario, the muon capture, the ionisation-cooling and the first stage of the muon acceleration. Different schemes, their performance and the technical challenges are compared., LINAC 2000 CONFERENCE, paper ID No. THC17

The GEL LEBT provides high efficiency beam transport and matching to the RFQ acceptance in the 4-dimensional phase space. The rms emittance growth is relatively small even for 60 kV extraction voltage. The number of particles occupying the 4-D RFQ acceptance strongly depends from the beam emittance at the entrance of the GEL LEBT. In most realistic case with the input emittance equal to the measured one, which is 320 p×mm×mrad (4×rms emittance) the number of particles inside the 4-D space with the projection emittance of 200 p×mm×mrad is 38% at the entrance and 35% at the output of GEL LEBT, which means that LEBT does not practically destroy beam emittance. The experimental value of the yield to the double aperture is 35% and confirms the expected performance of the GEL LEBT.