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The CERN PSB (Proton Synchrotron Booster) is currently undergoing a major upgrade with an increase in both injection and extraction energy. With the connection of the new LINAC 4, which replaces the now decommissioned LINAC 2, the energy of the beam to be transported to the PSB is increased from 50 MeV to 160 MeV. Simultaneously, the PSB will be upgraded to provide protons to the CERN PS (Proton Synchrotron) with an increase of energy from 1.4 GeV to 2 GeV. To cope with these increases, more than 40 magnets in the transfer lines to and from the PSB will be replaced with new magnets. This paper gives an overview of the challenges and chosen solutions concerned by these upgrades.

We report the results of several complementary radiation tests to qualify and calibrate a highly radiation sensitive Single-Mode (SM) Optical Fiber (OF) for distributed dosimetry application at CERN. The Radiation Induced Attenuation (RIA) is the physical phenomenon used to evaluate the Total Ionizing Dose (TID) received by the OF sensor. The radiation response tests comprise online RIA in the Near InfraRed (NIR) domain under 60Co γ-rays, X-rays and proton irradiations, as well as post mortem Optical Attenuation (OA) measurement to evaluate long term fading effects of the RIA. In this paper, we focus on the effect of successive irradiations, dose rate dependence and effects related to the change of the irradiation temperature up to 45 °C. On the basis of our investigation, we conclude that the studied OF is a suitable TID sensor and that it is well adapted for distributed OF radiation dose sensing. It is fully compatible with commercially available SM Optical Time Domain Reflectometers, with some noticeable advantages with respect to previously developed systems based on multimode OFs. Finally, the OF we investigated has been selected for the distributed monitoring of low radiation dose levels at CERN in the injector chain (Proton Synchrotron Booster, Proton Synchrotron, Super Proton Synchrotron) and parts of the Large Hadron Collider (LHC).

The CERN-MEDICIS (MEDical Isotopes Collected from ISolde) facility has delivered its first radioactive ion beam at CERN (Switzerland) in December 2017 to support the research and development in nuclear medicine using non-conventional radionuclides. Since then, fourteen institutes, including CERN, have joined the collaboration to drive the scientific program of this unique installation and evaluate the needs of the community to improve the research in imaging, diagnostics, radiation therapy and personalized medicine. The facility has been built as an extension of the ISOLDE (Isotope Separator On Line DEvice) facility at CERN. Handling of open radioisotope sources is made possible thanks to its Radiological Controlled Area and laboratory. Targets are being irradiated by the 1.4 GeV proton beam delivered by the CERN Proton Synchrotron Booster (PSB) on a station placed between the High Resolution Separator (HRS) ISOLDE target station and its beam dump. Irradiated target materials are also received from external institutes to undergo mass separation at CERN-MEDICIS. All targets are handled via a remote handling system and exploited on a dedicated isotope separator beamline. To allow for the release and collection of a specific radionuclide of medical interest, each target is heated to temperatures of up to 2,300°C. The created ions are extracted and accelerated to an energy up to 60 kV, and the beam steered through an off-line sector field magnet mass separator. This is followed by the extraction of the radionuclide of interest through mass separation and its subsequent implantation into a collection foil. In addition, the MELISSA (MEDICIS Laser Ion Source Setup At CERN) laser laboratory, in service since April 2019, helps to increase the separation efficiency and the selectivity. After collection, the implanted radionuclides are dispatched to the biomedical research centers, participating in the CERN-MEDICIS collaboration, for Research & Development in imaging or treatment. Since its commissioning, the CERN-MEDICIS facility has provided its partner institutes with non-conventional medical radionuclides such as Tb-149, Tb-152, Tb-155, Sm-153, Tm-165, Tm-167, Er-169, Yb-175, and Ac-225 with a high specific activity. This article provides a review of the achievements and milestones of CERN-MEDICIS since it has produced its first radioactive isotope in December 2017, with a special focus on its most recent operation in 2020. ispartof: FRONTIERS IN MEDICINE vol:8 ispartof: location:Switzerland status: published

In synchrotrons at the European Organization for Nuclear Research (CERN), magnetic measurement systems known as B-trains measure the magnetic field in the main bending magnets in real-time, and transmit this signal for the control of the synchrotron’s RF accelerating cavities, magnet power converter and beam monitoring systems. This work presents an assessment of the capabilities and performance of the new FIRESTORM (Field In REal-time STreaming from Online Reference Magnets) system as part of the first phase of commissioning. A short summary of the architecture of the measurement system is provided first, followed by the definition of an error model which can be used to characterize random and systematic errors separately. We present a procedure for the metrological calibration and qualification of the B-trains, including an experimental evaluation of the different error sources for the four new systems being commissioned in the Proton Synchrotron Booster (PSB), Low Energy Ion Ring (LEIR), Proton Synchrotron (PS) and the Extra Low ENergy Antiproton (ELENA) ring. In particular, we discuss a method to calibrate systematic gain and offset errors based on the RF cavity frequency offset needed to center the beam on its theoretical orbit.

The CERN Proton Synchrotron Booster (PSB) has been known to suffer from horizontal instabilities since its early operation. These instabilities appear at specific beam energies and range of working points. The source of the instability and the reason why the instabilities appear at specific energies remained unidentified. In routine operation, the instabilities have not been limiting the performance reach thanks to the horizontal feedback system. Recently, the interest in these instabilities has been sparked by the on-going LHC Injectors Upgrade (LIU) program, as well as, the Physics Beyond Colliders (PBC) study group. Their systematic characterization has been carried out through measurements. Macroparticle simulations and analytical modeling have been applied to explain the measurements and the dependence on the kinetic energy. Finally, the extraction kicker has been unambiguously identified as the source of the instability., CERN Yellow Reports: Conference Proceedings, Vol. 9 (2020): Proceedings of the ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators, Zermatt, Switzerland, 23–27 September 2019

A new beam dump has been designed, built, installed and operated to withstand the future proton beam extracted from the proton synchrotron booster (PSB) in the framework of the LHC Injector Upgrade (LIU) Project at CERN. The future proton beam consists of up to 1×1014 protons per pulse at 2 GeV and is foreseen after the machine upgrades planned for CERN’s Long Shutdown 2 (2019-2020). In order to be able to efficiently dissipate the heat deposited by the primary beam, the new dump was designed as a cylindrical block assembly, made out of a copper alloy and cooled by forced airflow. In order to determine the energy density distribution deposited by the beam in the dump, Monte Carlo simulations were performed using the fluka code, and thermomechanical analyses were carried out by importing the energy density into ANSYS®. In addition, computational fluid dynamics (CFD) simulations of the airflow were performed in order to accurately estimate the heat transfer convection coefficient on the surface of the dump. This paper describes the design process, highlights the constraints and challenges of integrating a new dump for increased beam power into the existing facility and provides data on the operation of the dump. A new beam dump has been designed, built, installed and operated to withstand the future proton beam extracted from the Proton Synchrotron Booster (PSB) in the framework of the LHC Injector Upgrade (LIU) Project at CERN, consisting of up to 1E14 protons per pulse at 2 GeV, foreseen after the machine upgrades planned for CERN's Long Shutdown 2 (2019-2020). In order to be able to efficiently dissipate the heat deposited by the primary beam, the new dump was designed as a cylindrical block assembly, made out of a copper alloy and cooled by forced airflow. In order to determine the energy density distribution deposited by the beam in the dump, Monte Carlo simulations were performed using the FLUKA code, and thermo-mechanical analyses were carried out by importing the energy density into ANSYS. In addition, Computational Fluid Dynamics (CFD) simulations of the airflow were performed in order to accurately estimate the heat transfer convection coefficient on the surface of the dump. This paper describes the design process, highlights the constraints and challenges of integrating a new dump for increased beam power into the existing facility and provides data on the operation of the dump.

The CERN large hadron collider (LHC) Injectors Upgrade seeks to reliably deliver the beams required for the High-Luminosity LHC (HL-LHC). As part of this, the proton synchrotron booster (PSB) will be upgraded from 1.4 to 2 GeV and will accelerate higher intensity beams. Along the transfer lines between the PSB and the proton synchrotron there are several dc-operated quadrupole magnets that are unable to produce the gradients required for the 2 GeV HL-LHC beams. To minimize power consumption, these will be replaced by laminated quadrupole magnets, operated in pulse to pulse modulation mode. The field homogeneity requirements imposed on these magnets is very tight, requiring a homogeneity of $5\times 10^{-4}$ on the integrated gradient. Such strict requirements presented several issues for the design, especially when considering the space constraints that naturally apply when upgrading a pre-existing accelerator. The design of these quadrupole magnets is summarized here.

Integrator drift is a problem strongly felt in different measurement fields, often detrimental even for short-term applications. An analytical method for modelling and feed-forward correcting drift in magnetic flux measurements was developed analytically and tested experimentally. A case study is reported on the proof of principle as a novel kind of quasi-DC field marker of the 5-ppm Nuclear Magnetic Resonance (NMR) transducer Metrolab PT2026, applied to the Extra Low ENergy Antiproton (ELENA) ring and the Proton Synchrotron Booster (PSB) at CERN. In some particle accelerators, such as in ELENA, the resulting feed-forward correction guarantees 1 μ T field stability over 120-s long magnetic cycle on a plateau of 50 mT, reducing by three orders of magnitude the field error caused by the integrator drift with respect to the state of the art.

At CERN the HL-LHC (High Luminosity Large Hadron Collider) and the LIU (LHC Injection Upgrade) projects call for an increase in beam parameters such as energy, intensity and brightness. To achieve this goal the whole accelerator complex will be upgraded. Systems, equipment and devices need to be redesigned and rebuilt accounting for the demanding new beam features. In this framework device impedance is a key parameter. It is essential to evaluate and to minimize the impedance of the component during its early design phase. This avoids beam instabilities and minimizes beam losses and induced heating. In this paper we outline general guidelines for a low-impedance design and we show how to implement them in a real case, taking as example the design of the new Proton Synchrotron Booster Absorber Scraper (PSBAS). This is a key component aimed to remove the beam halo at the beginning of the LHC accelerator chain., CERN Yellow Reports: Conference Proceedings, Vol 1 (2018): Proceedings of the ICFA Mini-Workshop "Impedances and Beam Instabilities in Particle Accelerators"

The LHC Injector Upgrade project aims at increasing the performance of the LHC injectors and includes the replacement of Linac2 by Linac4 as injector to the Proton Synchrotron Booster (PS B). In order to distribute the 160 MeV beam from Linac4 to the four rings of the PSB, a new distributor system has been built. The required five pulse generators have a pulse length ranging from 20 µs to 620 µs with a rise time of less than 2 µs and a maximum flattop ripple of ±1 %. Four generators distribute the beam to the four vertically stacked PSB rings whilst the fifth generator dumps the beam tail. The basic generator hardware consists of a Pulse Forming Network (PFN), two series connected IGBT switches, an optical trigger interface and a Fast Interlocks S ystem (FIS) for hardware protection. During the iterative development phase, solutions to fulfil the required performance relating to rise time, jitter, long-term stability and reliability have been implemented and will be presented. The different failure modes of the generator have been studied, identified and mitigated, mostly by means of the FIS. The FIS is integrated into a larger control system infrastructure via an Ethernet backbone and industrial bus (Profinet). The industrial bus manages all PLC controllers for slow supervision of ancillary systems and remote control systems from the operating room. The process of the final tuning and the reached performance are outlined. This paper presents the development phases of the generator, the hardware protection system, the final design choices and its performance.

160 MeV H$^−$ beam will be delivered from the new CERN linear accelerator (Linac4) to the Proton Synchrotron Booster (PSB), using a H$^−$ charge-exchange injection system. A $200 \mu \rm{g/cm}^2$ carbon stripping foil will convert H$^−$ into protons by stripping off the electrons. The H$^−$ charge-exchange injection principle will be used for the first time in the CERN accelerator complex and involves many challenges. In order to gain experience with the foil changing mechanism and the very fragile foils, in 2016, prior to the installation in the PSB, a stripping foil test stand has been installed in the Linac4 transfer line. In addition, parts of the future PSB injection equipment are also temporarily installed in the Linac4 transfer line for tests with a 160 MeV H$^−$ commissioning proton beam. This paper describes the foil changing mechanism and control system, summarizes the practical experience of gluing and handling these foils and reports on the first results with beam.

The 160 MeV H− beam from the Linac4 (L4) linear accelerator at CERN will be injected into the proton synchrotron booster (PSB) with a new H− charge-exchange injection system. It will include a stripping foil, to convert H− into protons by stripping off the electrons. To gain experience with these very fragile foils, prior to the installation in the PSB, and test different foil materials and thicknesses, lifetimes of the foils, the foil changing mechanism and interlocking functions, a stripping foil test stand will be installed in the L4 transfer line in 2015. This paper describes the mechanical design of the system and discusses the test possibilities and parameters.

International audience; In this paper, we report on the development and first deployment of a distributed optical fiber radiation sensor (DOFRS) for the online monitoring of radiation levels in the high-energy accelerator facilities of CERN. The DOFRS is composed of two basic parts: a set of suitably chosen radiation sensitive optical fibers (OFs), to be installed in the machine tunnel, and an optical time domain reflectometer (OTDR), to be installed in a radiation-free area. We carried out a calibration of the radiation response of a P-doped multimode OF under $^{60}$Co $\gamma$-rays and in the mixed-field radiation environment of the CHARM facility at CERN. By performing OTDR measurements, we are able to probe the radiation-induced attenuation in the OF along its length and calculate the deposited radiation dose with a spatial resolution of 1 m. In this paper, we describe the main features associated with DOFRS implementation in the proton synchrotron booster (PSB) at CERN. We also report the first results obtained from the monitoring of PSB radiation levels since its recommissioning in April 2017. The performances and advantages of the DOFRS system are discussed.

The CERN Proton Synchrotron booster (PSB) is one of the machines of the LHC injector chain which will be upgraded within the LHC Injectors Upgrade (LIU) project. The injection energy of the PSB will be increased to 160 MeV in order to mitigate direct space charge effects, considered to be the main performance limitation, aiming to double the brightness for the LHC beams. In order to better predict the gain to be expected, space charge simulations are being carried out. As a first step, benchmarking between simulations and measurements is needed. Efforts to establish a realistic modeling of field and alignment errors aim at extending the basic model of the machine toward a more realistic one. Simulations of beam dynamics with strong space charge and realistic errors are presented and analyzed in this paper.

20 págs.; 20 figs.; 2 tabs., The ISOLDE facility at CERN offers the largest selection of ISOL beams today. The overall aim of the HIE-ISOLDE project is to enlarge the physics domains achievable with these beams, in particular by raising the maximum energy of post-accelerated beams to more than 10MeV/u. An outline of the history of the project is followed by a succinct description of the superconducting linac chosen for acceleration and an overview of the parts of the project aiming to the improvement of the beam quality and intensity. Concrete examples are given of experiments that will be performed at HIE-ISOLDE c Società Italiana di Fisica, Fonds Wetenschappelijk Onderzoek, FWO, Big Science 1 (BE); Special thanks to CERN and the ISOLDE Collaboration, without their support this project will have not been realised.

As part of the LHC Injector Upgrade (LIU) project, the production of a high-intensity proton beam in the Proton Synchrotron Booster (PSB) at CERN will be achieved by injecting a beam of H− ions from the new linear accelerator LINAC4. During the injection process the two electrons of the H− ions are removed with a stripping foil across which the machine orbit is shifted to fill the machine aperture with beam. The process of filling the machine aperture is called ‘phase space painting’ and is accomplished with four individually-pulsed ferrite-cored kicker magnets. The magnets, two of 36μH inductance and two of 320μH inductance, will be excited by piecewise linearly decreasing currents with a maximum current of 400A for the 36μH magnets. The waveforms will comprise four different programmable slopes, changeable from pulse to pulse in the range of 8μs to 150μs. The four kicker waveforms must be well synchronized and deviate less than 0.5% from a reference waveform. Each pulse generator contains several stages of pre-charged capacitors that one after another are switched to the magnet to generate the current with the required slopes; additional stages are present to allow fine control of the slope linearity. The performance of the first operational prototype is presented and compared to theoretical calculations.

The ISOLDE facility [1–3] is one of the world-leading laboratories for the production and investigation of radioactive nuclei. ISOLDE belongs to CERN's accelerator complex situated on the border between Switzerland and France (Figure 1). The facility has been in operation since its start in 1967 and is presently receiving protons from the Proton Synchrotron Booster (PSB) of CERN. The success of ISOLDE is due to the continuous development of new radioactive ion beams and improvement of the experimental conditions. With the upcoming high energy and intensity upgrade HIE-ISOLDE the possibilities for experiments with exotic nuclei will be further boosted. This laboratory portrait gives an overview of the present facility that will focus on the status of radioactive ion beam production, the operation of ISOLDE, and the main experimental equipment rather than aiming at a comprehensive summary of physics results.

The Linac4, now being developed at CERN, will provide 160-MeV H - beams of high intensity N = 2 × 10 14 ions s - 1 . Before this beam can be injected into the CERN Proton Synchrotron Booster or future Superconducting Proton Linac for further acceleration, some sequences of 500-ps-long micro-bunches must be removed from it, using a beam chopper. These bunches, if left in the beam, would fall outside the longitudinal acceptance of the accelerators and make them radioactive. We developed a monitor to measure the time structure and spatial profile of this chopped beam, with respective resolutions Δ t ∼ 1 ns and Δ x ∼ 2 mm . Its large active area 40 mm × 40 mm and dynamic range also allows investigations of beam halos. The ion beam first struck a carbon foil, and secondary electrons emerging from the foil were accelerated by a series of parallel grid electrodes. These electrons struck a phosphor screen, and the resulting image of the scintillation light was guided to a thermoelectrically cooled, charge-coupled device camera. The time resolution was attained by applying high-voltage pulses of sub-nanosecond rise and fall times to the grids. The monitor has been tested with 700-ps-long UV laser pulses, and a 3-MeV proton beam. Its response over a wide range of beam intensities between N e ∼ 5 and 4 × 10 8 electrons emitted from the foil per pulse was studied. The monitor can also be used to measure the profiles of antiproton beams in the future facilities of Facility for Low-energy Antiproton Ion Research (FLAIR) or Extra Low Energy Antiproton Ring (ELENA).

High precision modeling of space-charge effects, together with accurate treatment of single-particle dynamics, is essential for designing future accelerators as well as optimizing the performance of existing machines. We describe Synergia, a high-fidelity parallel beam dynamics simulation package with fully three-dimensional space-charge capabilities and a higher order optics implementation. We describe the computational techniques, the advanced human interface, and the parallel performance obtained using large numbers of macroparticles. We also perform code benchmarks comparing to semi-analytic results and other codes. Finally, we present initial results on particle tune spread, beam halo creation, and emittance growth in the Fermilab Booster accelerator.

In addition to heavy ion collisions (RHIC Design Manual, Brookhaven National Laboratory), RHIC will also collide intense beams of polarized protons (I. Alekseev, et al., Design Manual Polarized Proton Collider at RHIC, Brookhaven National Laboratory, 1998 [2]), reaching transverse energies where the protons scatter as beams of polarized quarks and gluons. The study of high energy polarized protons beams has been a long term part of the program at BNL with the development of polarized beams in the Booster and AGS rings for fixed target experiments. We have extended this capability to the RHIC machine. In this paper we describe the design and methods for achieving collisions of both longitudinal and transverse polarized protons in RHIC at energies up to s =500 GeV .

The construction of a compact rapid cycling synchrotron has recently been studied at CERN to replace the first stage of its accelerator complex, the proton synchrotron booster. Although currently there are no plans to build this machine, fast cycled accelerator magnets are of general interest for numerous reasons. This has led to the design, manufacture, and testing of a scaled model dipole as detailed in this paper to show the capability of producing and characterizing a magnet design based on high-silicon content grain-oriented steel able to operate up to 1.3 T at 10 Hz.

Since its first operation in 1972 at an energy of 800 MeV, the CERN Proton Synchrotron Booster, which consists of four superimposed synchrotrons, has seen two upgrades: once to 1.0 GeV in 1988 and then to 1.4 GeV in 1999. During this time the main magnets of the machine have remained largely unchanged with small differences (1%) between the inner and outer gaps of the main bending magnet fields being compensated by trim power supplies. The future upgrade of the machine will demand to extract protons at an energy of 2.0 GeV and require almost double the original dipole field. At this field, due to saturation effects, the inner and outer gaps of the main dipole magnets will differ by up to 4%. This paper presents the design and implementation of a modification of the magnetic circuit strongly reducing these effects. We also discuss the results of experimental tests concerning the effects on field quality and eddy current transients, including the implications for the real-time magnetic field measurement system to control RF and power supplies.

Linac4 is the first element of the Large Hadron Collider Injectors Upgrade Project and will replace the existing Linac2 as linear injector of protons for the CERN accelerators. A new transfer line will link Linac4 to the Proton Synchrotron Booster. Approximately a hundred normal-conducting electro-magnets are required for beam steering and focusing along the linac and the transfer line. This text concentrates on the design of the Linac4 quadrupole magnets. The design and the first magnetic measurements of the inter-tank quadrupole electro-magnets are discussed. In addition, the design and optimization of the transfer line quadrupole magnets are highlighted. The compatibility of the magnetic requirements and the power converter constraints for the latter magnet type is assessed.

The LHC Injector Upgrade (LIU) project aims to prepare the CERN accelerator complex for reliably providing beam with the challenging characteristics required by the high luminosity LHC until at least 2030. Starting at the source a H- beam is accelerated by LINAC4 and then injected into the Proton Synchrotron Booster (PSB). During injection the two electrons of the H- ions are removed with a stripping foil. The protons produced in this way are then accelerated successively by the PSB, the PS and the SPS before being injected into the LHC. When the H-beam is injected into the PSB the machine orbit is shifted across the stripping foil to fill the machine aperture with beam. This shifting of orbit is called `painting' and is accomplished with four slow kicker magnets. The kickers must be well synchronized and with less than 0.5% of deviation from a reference waveform. These kicker magnets will operate with a maximum current of 400A and will have waveforms comprising four different programmable slopes, changeable from pulse to pulse in the range of 10μs to 100μs. Each kicker will be energized by a pulse generator which contains several stages of pre-charged capacitors that one after another are switched to the magnet to generate the current with the required slopes. Additional stages are present to allow fine control of the slope linearity.

The new linear accelerator (Linac4) under construction at CERN [1] is designed to provide a 160MeV negative hydrogen ions (H-) beam to the Proton Synchrotron Booster (PSB). Linac4 is intended to replace the ageing 50MeV Linac2 and aims to increase the LHC beam luminosity. Several H-sources are under development [2] in view of gradually increasing the H-intensity to 80 mA with a limited co-extracted electron beam of 1-1.5 A. Previous attempts to reach this H-beam intensity showed the necessity of replacing the source's high voltage DC power supplies with high voltage pulsed power converters, with the objective of mitigating destructive arc events inside the source between two RF pulses (beam extraction length of 700 μs with 2 Hz repetition rate).

The LHC Injector Upgrade (LIU) project aims to prepare the CERN accelerator complex for reliably providing beam with the challenging characteristics required by the high luminosity LHC until at least 2030. Starting at the source a H- beam is accelerated by LINAC4 and then injected into the Proton Synchrotron Booster (PSB). During injection the two electrons of the H- ions are removed with a stripping foil. The protons produced in this way are then accelerated successively by the PSB, the PS and the SPS before being injected into the LHC. When the H- beam is injected into the PSB the machine orbit is shifted across the stripping foil to fill the machine aperture with beam. This shifting of orbit is called `painting' and is accomplished with four slow kicker magnets. The kickers must be well synchronized and deviate less than 0.5% from a reference waveform. They will operate with a maximum current of 400A and will have waveforms comprising four different programmable slopes, changeable from pulse to pulse in the range of 10μs to 100μs. Each kicker will be energized by a pulse generator which contains several stages of pre-charged capacitors that one after another are switched to the magnet to generate the current with the required slopes. Additional stages are present to allow fine control of the slope linearity. The magnet current is measured and analyzed. Errors are corrected by adjusting the charging voltages and the switch timing. The precision of the waveform is maintained even if circuit parameters change slightly due to aging or component tolerances.

Linac4 is a 160 MeV linear accelerator which will inject negative hydrogen ions (H−) into CERN’s Proton Synchrotron Booster, a required upgrade to improve the beam brightness in the LHC injector chain. A volume production RF ion source, based on the design of the DESY RF source was implemented, but showed considerable electron dump ablation during operation at 45 keV beam energy. To reduce the electron beam power density in the dump, a magnetized Einzel lens is designed that reduces the beam energy to 10 keV before permanentmagnets dump the electrons on a tungsten surface. Presented in this paper are simulations of the design using IBSimu, the tunable range of parameters depending on the extracted H− and electron current, as well as details of the implementation, the choice of pulsed power converters and the electrode alignment system. In addition, simulations of proton extraction from this source will be shown.

As part of a collaboration with the SSC, CEA/Saclay has designed superconducting quadrupole magnet for the High Energy Booster ring. A number of prototypes are being built at Saclay, after which the production will be handed over to an American firm. This paper presents the mechanical, thermal and electromagnetic analyses which have been performed during the design of the magnet. >

Space-charge effects have been identified as the most serious intensity limitation in the CERN PS and PS Booster, on the way towards ultimate LHC performance and beyond. We here explore the application of several previously proposed space-charge compensation methods to the two LHC pre-injector rings, and the challenges which need to be overcome. The methods considered include the reduction of tune shift and resonance strengths via octupoles, pole-face windings, electron lenses, or neutralisation.

An increase of beam intensity and brightness is essential for future upgrades of existing CERN proton accelerator facilities. A first step can be an injection of H− ions from a new higher energy H− linear accelerator called Linac4 into the Proton Synchrotron Booster (PSB). A second step could be the complete replacement of the PSB by a high‐power linear accelerator, called SPL, injecting directly into the Proton Synchrotron (PS). Both injection scenarios require a high performance, high reliability negative hydrogen ion source. This paper will present the challenging source requirements and the two approaches to fulfill them.

The PS Booster delivers particles for most of the CERN experiments. The PS complex will become particle source for LHC in 2007. For this reason PS complex electronics is continuously upgraded to meet new requirements in performance and remote management. A new acquisition system has been developed to allow the measurement of the individual intensity of each bunch in a 1Hz bunch train. Such a system will be used for the measurement of beams at the injection, ejection and acceleration lines . The method is based on integrating of the analogue signal supplied by a Beam Current Transformer. The signal is sampled by two 12 bits ADCs with 20x oversampling. The output of ADC is then processed in FPGA, where the rest of the signal processing is performed. The measurement system was build as a standard VME module. Apart from that, on same board there were implemented current and charge calibrators.

It is speculated that the space charge effect cause beam emittance growth through the resonant envelope oscillation. Based on this theory, we propose an approach, called space charge stopband correction, to reduce such emittance growth by compensation of the half-integer stopband width of the resonant oscillation. It is illustrated with the Fermilab Booster model.

The bunch-by-bunch BPM signal array has to be reshaped into a turn-by-turn (TBT) matrix in order to make the TBT beam position information of a single bunch available for further data analysis, such as via the Fourier transform to obtain the synchrotron tune and betatron tune, etc. Since the RF frequency sweeps more than 10 MHz in the first 8 ms of a Booster cycle, the revolution time decreases more than 20%. The number of data points for each Booster turn (BT) should be varied in the same pace with the revolution time since the sampling rate of a digital oscilloscope is usually fixed. And this can be done by pre-determining the relationship between the RF frequency and the time in a cycle via the curve fit.

Turn-by-turn data from a single BPM includes information on the chromaticity in sidebands displaced above and below the betatron frequency by an amount of the synchrotron frequency. It may be necessary to induce small amplitude synchrotron oscillation by giving the beam a small kick. Power spectrum of the BPM data gives clear chromatic sidebands, and they can be applied to the chromaticity measurement in the Fermilab Booster.

The difference between the effective rf voltage and the accelerating voltage required to match the rate of change of the Booster magnetic field can be used to estimate the energy loss per beam turn. Although the effective rf voltage (RFSUM) and the synchronous phase can be experimentally measured and used to calculate the accelerating voltage, the calibration of the signals during the fast change of the Booster rf frequency is difficult and appears to introduce some offset to the beam energy loss estimation. An observed linear relationship between energy loss and beam intensity is used to evaluate the offset, which is then applied to the experimental data. This approach, rather than recalibrating the signals, is simple and suitable for minimizing the error in the data.

The space charge limit in circular program accelerators has been studied using a simulation program. Results from the simulation study indicate a different model for the space charge limit than the often-presented models which emphasize resonances due to magnetic field errors. In studies of three operating accelerators, which include the Alternating Gradient Synchrotron, the Proton Synchrotron Booster, and the Fermilab Booster, it was found that the computed intrinsic space charge limit was fairly close to the experimentally observed space charge limit. This result and studies of the effects of resonances due to magnetic field errors suggest that the intrinsic space charge limit provides an upper bound for the space charge limit which is not far from what is actually achieved by operating accelerators. The resonances present due to magnetic field errors, if strong enough, can prevent the accelerator from achieving the intrinsic space charge limit. However, the effects of these resonances were found to be appreciable only when the beam intensity gets close to the intrinsic space charge limit. Well below the intrinsic space charge limit, there is little beam growth due to magnetic field error driven resonances, and the space charge forces tend to stabilize these resonances. >

The beam position monitoring (BPM) system for the Brookhaven National Laboratory (BNL) booster consists of 48 main pick-up electrodes (PUEs) symmetrically distributed around the ring and two special PUEs for the transverse dampers. The BPM system utilizes an integrator that is AC coupled to the PUE. The operation of the design relies upon the use of direct digital synthesis. To eliminate the cumulative error in the signal from the PUE introduced by the AC coupling, a base line restorer (BLR) is used to reestablish a reference value between the bunches. Three signals phase locked to the beam are needed to insure that the triggers to the BLRs occur between bunches. The triggers for the main PUEs require a clock of 48 times the revolution frequency as well as the RF frequency to time their occurrence. The quadrature components of RF frequency are used in a phase shifter to produce the triggers for the damper PUEs. By making use of the direct digital synthesis technology, all three signals produced were locked to the beam by using only a single phase locked loop. >

Beam performance results for the injection phase of proton beam commissioning of the Alternating Gradient Synchrotron (AGS) booster synchrotron are presented. The beam from the 200 MeV LINAC is transported through a new beam line into the booster. This LINAC-to-booster (LTB) beam line includes a 126 degrees bend and brings the injected beam onto the Booster injection orbit through the backleg of a main-ring dipole magnet. Transfer of the beam from the LINAC to the booster, the spiralling beam, and closing of the orbit in the booster ring are discussed. Injection and transport through one sector of the ring were accomplished. >

The delivery of a beam with characteristics appropriate to the filling of the LHC (Large Hadron Collider) proton-proton collider requires that the CERN PS complex provide a beam whose transverse particle density exceeds, by a factor of three, the highest currently attained. The beam dynamics operations and the associated hardware modifications which would be required to achieve this goal are considered. The approach favored involves filling the Proton Synchrotron (PS) with two pulses from the Proton Synchrotron Booster (PSB) and requires and RF quadrupole (RFQ2) as a preinjector for the linac (LINAC2), an increase of the PSB extraction energy and additional RF systems, both in the PSB and PS. >

The KAON Factory will require over 2000 magnets to transport protons from the existing 500-MeV cyclotron through three storage rings and two synchrotrons and deliver them to the experiment area at 30 GeV. The magnet requirements are summarized and the results of measurements on prototypes for the 50-Hz booster magnets are compared with design values. The results of prototype work, some of the more difficult design aspects of other magnets, and the tolerances required to achieve production magnets uniform to +or-2 parts in 10/sup 4/ are discussed. >

The design concepts for ferrite-tuned accelerating cavities discussed differ from conventional solutions using thick ferrite toroids for frequency tuning. Instead, tuners consisting of an array of ferrite-loaded striplines are investigated. These promise more efficient cooling and higher operational reliability. Possible improvements in both voltage holding and average power handling are examined. A variety of options discussed permit substantial improvements on both voltage holding capabilities and tolerable RF power levels of ferrite-tuned cavities for rapid-cycling booster synchrotrons. Layout examples for the SSC-LEB RF system are presented (tuning range 47.5 to 59.6 MHz, repetition frequency 10 Hz). >

The fast-growing "Ring 4" instability occurring at intensities above 6.5/spl times/10/sup 12/ protons in the top one of the four rings of the CERN PS Booster (PSB) is finally explained by an asymmetry in the 40 vacuum pump manifolds common to all rings. Measurements (by wire method) and calculations show a sharp resonant peak (Q/spl sim/2000) at 1100 MHz and shunt impedances two times higher for the Ring 4 ports as compared to the other rings. This factor is sufficient to explain that the threshold of the instability falls below the maximum intensity only in Ring 4. A final, but labor-intensive and expensive, cure consists of inserting short-circuiting sleeves into all 160 beam ports. Results of beam and impedance measurements and the planned cure will be presented and discussed.

A beam-abort dump for the Fermilab Main Injector to handle 3E13 protons per pulse at 150 GeV has been designed. A 120 GeV beam line goes through the beam-dump off-set by 27 cm from its center. The design and the environmental safety aspects of the beam-dump are described here.

A self-consistent theory of periodic hole structures in coasting beams in synchrotrons and storage rings is presented, extending the theory on localized holes. The analysis reveals new intrinsic nonlinear modes which owe their existence to a deficiency of particles trapped in the self-sustained potential well, showing up as notches in the thermal range of the distribution function. It is therefore the full set of Vlasov-Poisson equations which is invoked; linearized treatments as well their nonlinear extensions fundamentally fail to cope with this strongly nonthermodynamic phenomenon. Qualitative agreement with the holes recently found at the CERN proton synchrotron booster is shown. © 2002 The American Physical Society.

Stationary, self-consistent, and localized longitudinal density perturbations on an unbunched charged-particle beam, which are solutions of the nonlinearized Vlasov-Poisson equation, have recently received some attention. In particular, we address the case that space charge is the dominant longitudinal impedance and the storage ring operates below transition energy so that the negative mass instability is not an explanation for persistent beam structure. Under the customary assumption of a bell-shaped steady-state distribution, about which the expansion is made, the usual wave theory of Keil and Schnell (1969) for perturbations on unbunched beams predicts that self-sustaining perturbations are possible only (below transition) if the impedance is inductive (or resistive) or if the bell shape is inverted. Space charge gives a capacitive impedance. Nevertheless, we report numerous experimental measurements made at the CERN Proton Synchrotron Booster that plainly show the longevity of holelike structures in coasting beams. We shall also report on computer simulations of boosterlike beams that provide compelling evidence that it is space-charge force which perpetuates the holes. We shall show that the localized solitonlike structures, i.e., holes, decouple from the steady-state distribution and that they are simple solutions of the nonlinearized time-independent Vlasov equation. We have derived conditions for stationarity of holes that satisfy the requirement of self-consistency; essentially, the relation between the momentum spread and depth of the holes is given by the Hamiltonian-with the constraint that the phase-space density be high enough to support the solitons. The stationarity conditions have scaling laws similar to the Keil-Schnell criteria except that the charge and momentum spread of the hole replaces that of the beam. (29 refs).

Recently, it was proposed to use negatively charged electron beams for compensation of beam-beam effects due to protons in the Tevatron collider. The authors show that a similar compensation is possible in space-charge dominated low energy proton beams. The idea has a potential of several-fold increase of the FNAL Booster beam brightness. Best results will be obtained using three electron lenses around the machine circumference, using co-moving electron beam with time structure and profile approximately matched to the proton beam. This technique, if feasible, will be more cost effective than the straightforward alternative of increasing the energy of the injection linac.

The CERN PS Booster (PSB) consists of 4 superposed rings supplied with protons from a 50 MeV Linac The CERN PS Booster (PSB) consists of 4 superposed rings supplied with protons from a 50 MeV Linac. The proton beam is then accelerated to 1 GeV and sent either to the 26 GeV Proton Synchrotron (PS) or to the ISOLDE facility. This is carried out in a multi-cycle mode every 1.2 s. For high-intensity beams, the working-point in the tune diagram needs to be changed considerably during acceleration from 50 MeV to 1 GeV and the repeated measurement of the tunes throughout the cycle is an important requirement. Up to now, tune values were obtained through calculations based on quadrupole currents. However, practical experience has shown the need for a direct tune measurement system. For this purpose, a classical kick technique is used. A fixed amplitude kick of duration equal to one revolution period excites coherent betatron oscillations. For fast treatment, a Digital Signal Processing (DSP) module in a VME-standard crate was selected. It carries out the Fast Fourier Transform (FFT) analyses of signals from position-sensitive pickups in both planes and evaluates the tunes. These measurements are carried out every 10 ms during the 450 ms acceleration ramp. The paper presents the novel features of this system, particularly the beam-offset signal suppression as well as the peak-search algorithm which yields the tune values.

Since the move of ISOLDE from CERN’s synchrocyclotron (SC) to the Proton Synchrotron Booster (PSB) in 1992 extensive work has been devoted to the development of new beams, i.e. the production of new isotopes, beams of higher intensity and the ionization of further elements. Most of these developments were driven by the particular needs of the physics community proposing new experiments. The main achievements were the adaption of liquid metal targets to the pulsed proton beam to prevent shockwaves and splashing inside the target container and systematic studies on the time structure of the release of the isotopes from the target. Furthermore the work on laser ion-sources already started at ISOLDE-2 was continued, the so-called RIST target was developed, and most recently first tests on the isotope production while increasing the proton energy from 1 GeV to 1.4 GeV were done. The latter topics are discussed in this paper.

This paper reviews 40 years of operation of the CERN Proton Synchrotron Booster, from the commissioning in the early 1970s until today's operation as injector for the Large Hadron Collider (LHC) and as one of the backbone accelerators for CERN's fixed-target physics program.

The design goal for the Fermilab Main Injector (FMI) is to accelerate a minimum of 6/spl times/10/sup 10/ protons per bunch through the transition. We present here the results from simulation studies of the transition crossing in the FMI using the particle tracking code ESME.