GSI, Darmstadt
IAP, Frankfurt am Main
The antiproton program at FAIR requires a dedicated proton linac to be used as injector for the SIS 100 synchroton. This 325 MHz linac will accelerate up to 70 mA proton beam to the injection energy of 70 MeV. This linac will be the first machine based on CH-DTL's, the novel cavity developt by Frankfurt University and GSI. This new cavity is characterized by the lack of internal focusing elements which allows the construction of very compact cavities resulting in a higher shunt impedance when compared to conventional RF structure. The proton linac is based on 6 coupled CH-DTL followed by three standard CH's for a total length of around 25 meters. A complete description of the beam dynamics together with the general status of the project is presented and discussed,
MEPhI, Moscow
The undulator linear accelerator using electrostatic undulator (UNDULAC-E) or RF undulator (UNDULAC-RF) are suggested as an initial part of high intensity ion linac *, **. In UNDULAC ion beam is accelerated by the combined field of two non-synchronous space harmonics. The space charge force is main factor limiting beam intensity. There exist two ways to increase ion beam intensity: (i) to enlarge the beam cross section and (ii) to use the space charge neutralization. The high intensity ribbon ion beam can be accelerated in UNDULAC ***. Accelerating force value in UNDULAC is proportional to squared particle charge and oppositely charged ions with the identical charge-to-mass ratio can be accelerated simultaneously within the same bunch and the beam space charge neutralization can be realized. These two methods of beam intensity increasing will discussed in this paper.
* E.S. Masunov, Sov. Phys. Tech. Phys., 1990, 35 (8), p. 962
** Masunov E.S., Polozov S.M. Tech. Phys.50, No. 7, 2005, p. 112
*** E.S. Masunov, S.M. Polozov. NIM A, 558 (2006), p. 184
MEPhI, Moscow
The accurate treatment of own beam space charge influence is the main problem for all beam dynamics codes. Traditionally only the Coulomb field is taking into account for low energy beams and the radiation part is accounting for high energy beams. But now the current of accelerating beam enlarges and some radiation effects should be discussed for low energy beam also. The beam loading is more important of them. This effect should be studied now not only in electron linacs but for proton also. The BAMDULAC code is designing in MEPhI since 1999 for beam dynamics study *. The especial version BEAMDULAC-BL was designed for 3D beam dynamics study with accurate treatment both the Coulomb field and beam loading. The methods of beam loading treatment and the results of code testing are presented in this report. Some examples of beam dynamics study in linacs are discussed.
* E.S. Masunov, S.M. Polozov. NIM A, 558 (2006), p. 184
ORNL, Oak Ridge, Tennessee
Experience using laser-wire beam profile measurement to perform transverse beam matching in the SNS superconducting linac is discussed. As the SNS beam power is ramped up to 1 MW, transverse matching should become more critical to control beam loss and residual activation. In our experiments, however, beam loss in the SC linac is not very sensitive to the matching condition. In addition, we have encountered some difficulties in performing a satisfactory transverse beam matching with the envelope model currently available in our XAL software framework. Offline data analysis from multi-particle tracking simulation shows that the accuracy of the current matching algorithm may not be sufficient to the SC linac.
GSI, Darmstadt
The DYNAMION code was implemented to perform beam dynamics simulations for the different possible transport lines for a proton beam with an energy of 10 MeV, coming from a high intensity laser ion source. It was intended to check the chromaticity and space charge effects taking into account high order aberrations. The investigations were done for a solenoidal and alternatively for a quadrupole channel applying different beam parameters (as input energy spread, transverse divergency, current) as well as different layouts of the transport line. The beam evolution along the transport, the emittance growth and the beam transmission were analyzed and compared. Finally the influence of an RF buncher, required to match the proton beam to the following accelerating structure, was investigated.
IF-UFRGS, Porto Alegre
A theoretical framework that allows to accurately calculate the distribution functions and the emittance growth of an initially mismatched charged-particle beam after it relaxes to equilibrium is presented. The theory can be used to obtain the fraction of particles which will evaporate from the beam to form the halo. It is applied both to highly space charge dominated beams*, as well as to beams with finite initial emittance** with general initial distributions***. Results based on an approximation of the theory that allows simpler analytic expressions for the final stationary state are also presented. The calculated emittance growth and final beam distribution are found to be in good agreement with N-particle beam simulations.
* Nunes, Pakter, Rizzato, Phys. Plasmas 14, 023104 (2007).
** Levin, Pakter, Teles, Phys. Rev. Lett. 100, 040604 (2008).
*** Teles, Pakter, Levin, Appl. Phys. Lett. 95, 173501 (2009).
MEPhI, Moscow
It was done the studies on high intensity ion beam dynamics in axisymmetric RF linacs both analytically, in terms of the so-called smooth approximation, and numerically in [*,**] rather carefully. For all that, effects of beam self-space-charge field were not taken into consideration under analytical investigations of the focusing by means of non-synchronous harmonics up to date. These effects are said to affect a focusing parameters choice deeply. A “beam-wave” Hamiltonian is derived under assumption that a bunch has an ellipsoidal form. Analytical results specify that given in [**] and it is verified numerically.
* E.S. Masunov, N.E. Vinogradov. Phys. Rev. ST-AB, 2001, Vol. 4, No. 7, 070101.
** V.S. Dyubkov, E.S. Masunov. IJMP A, 2009, Vol. 24, No. 5, p. 843.
ESS, Lund
The European Spallation Source, ESS, will use a linear accelerator delivering high current long pulses with an average beam power of 5 MW to the target station at 2.5 GeV in the nominal design. The possibilities to upgrade to a higher power LINAC at fixed energy are considered. This paper will present a full review of the LINAC design and the beam dynamics studies.
CERN, Geneva
ESS, Lund
SPL is a superconducting H- LINAC under study at CERN. The SPL is designed to accelerate the 160 MeV beam of LINAC4 to 4-5 GeV, and is composed of two families of 704.4 MHz elliptical cavities with geometrical betas of 0.65 and 1.0 respectively. Two families of cryo-modules are considered: the low-beta cryo-module houses 6 low-beta cavities and 4 quadrupoles, whereas the high-beta one houses 8 cavities and 2 quadrupoles. The regular focusing structure of the machine is interrupted at the transition between low beta and high beta structure and at 1.4 and 2.5 GeV for extracting medium energy beam. The accelerator is designed for max. 60 mA peak current (40 mA average) and max. 4% duty cycle, implying a very accurate control of beam losses. In particular the choice of the diagnostics and correction system, the maximum quadrupole gradient to avoid Lorentz stripping and the effect of the RF power delivery system on the beam quality are discussed in this paper.
CEA, Gif-sur-Yvette
INFN/LNL, Legnaro (PD)
CIEMAT, Madrid
The IFMIF project (International Fusion Materials Irradiation Facility) is one of the three parts of the Fusion Broader Approach signed by Japan and Europe, aiming at studying materials which must resist to very intense neutron radiations in future fusion reactors. One major system of this project is its two accelerators producing the neutron flux by accelerating Deuteron particles up to 40 MeV against a Lithium target. In a first phase called EVEDA (Engineering Validation and Engineering Design Activity), a full scale prototype accelerating particles up to 9 MeV is being studied and constructed in Europe, to be installed in Japan. Two unprecedented performances are required: the very high power and very high intensity of 2x5 MW and 2x125 mA CW. That leads to numerous unprecedented challenges: harmful losses even for those as low as 10-6 of the beam, non-linear dynamics induced by very strong space charge forces, difficulties for equipment and diagnostic implementations in the high compact sctructure, need of specific tuning strategies in this context. These issues are highlighted in this article, and the ways they are addressed are detailed.
Fermilab, Batavia
Project-X is a proposed multi-MW proton facility at Fermilab. Based on a new superconducting H- linear accelerator, it would provide the foundation for a flexible long term intensity frontier physics research program. Two machine configurations have been developed. The first one involves a single 8 GeV, pulsed linac (9 mA peak, 1 ms @ 5 Hz pulses) followed by accumulation and acceleration to 60-120 GeV in the existing Main Injector synchrotron. The second -and currently favoured one- replaces the single pulsed linac by a 3 GeV (10 mA peak, 1 mA average @ 325 MHz), continuous wave linac followed, up to 8 GeV, by either a rapid cycling synchrotron or a second (pulsed) linac. We present here an overview of beam optics for the 3 GeV CW linac. Constraints related to cryostat configuration, field limits in cavities, particle loss mechanisms, and the need for warm instrumentation sections are discussed. Alignment, field amplitude and phase tolerances are also addressed.
NSCL, East Lansing, Michigan
FRIB, East Lansing, Michigan
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the “construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society.” A superconducting, heavy-ion, driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. An overview of the beam dynamics will be presented.
CERN, Geneva
Linac4 is a 160 MeV H- ions accelerator, which will replace the 50 MeV proton Linac (Linac2) as injector for the CERN complex from 2015. The higher output energy together with charge-exchange injection will allow increasing beam intensity in the following machines. Linac4 is about 100m long, normal-conducting, and will be housed in a tunnel, 12m below ground, on the CERN Meyrin site. The low energy front-end, consisting of a 45 KeV source, a 3-m long RFQ and a 3 MeV chopper line, will be commissioned starting next year in a temporary location. It will then be moved to the tunnel at the end of 2012 and the commissioning in situ will be done progressively with the installation of the accelerating structures. The preparation of 4 commissioning stages (12, 50 100, and 160 MeV) is of key importance to meet the goals of beam performance and reliability. An extensive campaign of simulation is in progress to define the necessary measurements and the required diagnostics accuracy for a successful set-up of the transverse and longitudinal parameters of the machine. This paper presents the results of the simulations and the measurement strategy.
Soreq NRC, Yavne
The SARAF accelerator is designed to accelerate both deuteron and proton beams up to 40 MeV 2mA. Phase I of SARAF consists of a 4-rod RFQ (1.5 MeV/u) and a prototype superconducting module (PSM) housing 6 half-wave resonators (HWR) and 3 superconducting solenoids (4-5 MeV). Beam dynamics TRACK simulation for a proton and a deuteron beam, tailored to the present available field amplitude at each cavity were used to evaluate and tune the linac. The simulation is a key factor to reach a stable high intensity CW beam. The ions energy spectra were measured using the Rutherford scattering technique. This technique is used to tune the cavities to the desired amplitude and phase. The measured energy gain and the energy spread at the RFQ exit and along the PSM were in good agreement with the beam dynamics simulations. Following field flatness modification at the last section of the 4-rod RFQ the transmission curve through the RFQ and the PSM as function of the electrode voltage is similar to the simulations. A HWR was used as a buncher and the measured beam energy spread as function of the bunching voltage was used to qualitatively estimate the longitudinal emittance.
KEK, Ibaraki
JAEA/J-PARC, Tokai-mura
We report the present status of the beam commissioning for J-PARC linac and our effort to understand the experimental results obtained in the course of the commissioning with the help of particle simulations.
ORNL, Oak Ridge, Tennessee
The overview of the Spallation Neutron Source (SNS) linac lattice, diagnostics, and beam dynamic is presented. The models and model based tuning procedures of the warm and superconducting parts of the SNS linac are discussed. There are significant discrepancies between predicted by simulations and measured losses in the superconducting part of the linac. The possible reasons for these losses and their relation to the beam dynamics are discussed.
GSI, Darmstadt
ITEP, Moscow
IAP, Frankfurt am Main
With the advanced multi-particle code DYNAMION it is possible to calculate beam dynamics in linear accelerators and transport lines under space charge conditions with high accuracy. Special features as data from the real topology of RFQ electrodes, drift tubes, quadrupole lenses, misalignment and fabrication errors and consideration of field measurements lead to reliable results of the beam dynamics simulations. Recently the DYNAMION code is applied to the upgrade and optimization of the UNILAC as an injector for the Facility for Antiproton and Ion Research at Darmstadt (FAIR). An operation of the FAIR requres for the increase of the beam- intensity and -brilliance coming from the UNILAC (up to factor 5). End-to-end simulations for the whole linac (from ion source output to the synchrotron entrance) allow for the study and optimization of the overall machine performance as well as for calculation of the expected impact of different upgrade measures, proposed to improve beam brilliance. The results of the beam dynamics simulations by means of the DYNAMION code are compared with the recent measurements, obtained after upgrade of the High Current Injector (GSI-UNILAC-HSI) in 2009.
CEA, Gif-sur-Yvette
We review the beam dynamics basis of non-equipartitioned beams, discuss the consequences of different types of couplings on the beam stability, especially the space charge. Several multiparticle simulations and experiments are shown to illustrate these instability issues.
INFN/LNL, Legnaro (PD)
New projects like IFMIF or the new generation of Spallation Neutron Source require high power beams with high availability and reliability. To achieve these results one needs low beam losses and a good control beam dynamics. This paper focuses on the important characteristics and critical beam dynamics design issues for the high intensity linacs. In particular the techniques used for the loss control at the design stage, with the emphasis on the physical phenomena like emittance growth and halo. The reliability issue will be addressed with practical examples from the low energy and high current IFMIF-EVEDA project and comparing this case with higher energy projects.
IF-UFRGS, Porto Alegre
UFPel, Pelotas
In this paper, the dynamics of inhomogeneous high-intensity charged particles beams is investigated. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation*. A theory is presented which allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles. The halo size and emittance growth are estimated using a core-particle type analysis where the inhomogeneous core density evolution is determined based on an average Lagrangian approach**. The role of envelope mismatches in the wave breaking process is also studied. The analysis reveals that the wave breaking time is very susceptible to the mismatch; judiciously chosen mismatches can largely extend beam lifetimes***.
*Anderson, Rosenzweig, PRST AB 3, 094201 (2000); Rizzato, Pakter, Levin, Phys Plas 14, 110701 (2007).
**Nunes, Pakter, etal, Phys Plas 16, 033107 (2009).
***Souza, etal , APL 96, 141503 (2010).
IPN, Orsay
GANIL, Caen
IN2P3 IPNL, Villeurbanne
CEA, Gif-sur-Yvette
The SPIRAL2 facility at GANIL-Caen is now in its construction phase, with a project group including the participation of many French laboratories (CNRS, CEA) and international partners. The SPIRAL2 facility will be able to produce various accelerated beams at high intensities: 40 MeV Deuterons, 33 MeV Protons with intensity until 5mA and heavy ions with A/Q=3 up to 14.5MeV/u until 1mA current. We will present the final status of the high energy beam transport lines of the new facility. Various studies were performed on HEBT and beam-dump concerning beam dynamics, safety and thermo-mechanicals aspects. New experimental areas using stable beams and the cave dedicated to radioactive ion production will be presented according the scientific program.
ESS Bilbao, Bilbao
University of Warwick, Coventry
Bilbao, Faculty of Science and Technology, Bilbao
Fermilab, Batavia
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ESS-Bilbao, Zamudio
Imperial College of Science and Technology, Department of Physics, London
Elytt Energy, Madrid
STFC/RAL, Chilton, Didcot, Oxon
The Proposed Multi-specimen Low Energy Transport System (LEBT) consists of a series of solenoids with tunable magnetic fields, used to match the characteristics of the beam to those imposed by the RFQ input specification. The design of the LEBT involves selecting the number of solenoids to use and their fixed positions, so that the set of fields that provides the desired matching can be found for any given conditions (different currents, input emittances, etc). In this work we present the first simulations carried out to design the Bilbao Accelerator LEBT, which were peformed using several codes (Track, GPT, Trace2D). The best configuration is discussed and evaluated in terms of the degree of matching to the RFQ input requirements.