• M. Xiao, D.E. Johnson, L.G. Vorobiev
  Fermilab, Batavia

A simplified Recycler lattice was created to fine tune injection straight, ring tune, and phase trombone. In this paper, we will present detailed modifications for further optimization of Recycler lattice which require the investigation of tune footprint and dynamic aperture based on higher order momentum components of the magnetic fields, together with the space charge effects.

• Y. Zhang, Y.S. Derbenev, G.A. Krafft, B.C. Yunn
  JLAB, Newport News, Virginia

The conceptual design of a polarized ring-ring electron-ion collider based on the CEBAF recirculated electron SRF linac relies on high repetition rate and high averaged current ion beams with very short bunch length and very small transverse emittance for reaching ultra high collider luminosity, up to middle of 10³⁴ s^-1cm^-2. Nevertheless, making of such ion beams is a significant challenge, depending on various accelerator R&D including ion source, SRF linac, staged electron cooling and crab crossing at interaction points. In this paper, we will present some new ideas and concepts towards to realization of high collider luminosities, as well as preliminary conceptual design of various components of an ion complex that is capable to create such ion beams.

• G.H. Rees, D.J. Kelliher
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon

High power driver rings are examined, using new FFAG designs, based on cells of five, scaling symmetrical pumplet magnets. Apertures are minimized by using large, betatron phase shifts per cell, typically μh ~ 280° and μv ~ 130°. Key aspects are the lengths of the long straight sections, particularly IF Hˉ charge exchange injection is required. Rings are considered for ISIS upgrades and Neutrino Factory proton and muon drivers. both with and without insertions.

• N. Hayashi, H. Harada, S. Hatakeyama, H. Hotchi
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• J. Takano, T. Toyama
  J-PARC, KEK & JAEA, Ibaraki-ken
• M. Tejima
  KEK, Ibaraki

The Beam Based Alignment (BBA) of the BPM is inevitable for precise and absolute beam position measurements. Even though careful fabrication and installation of the BPM detector, it has to be calibrated by using the beam. Usually, it requires that the individual quadrupole magnet is able to be controlled. However, it is not always that case. In addition, scanning over the all BPM is time consuming procedure. The BBA method under coupled QM environment would help to reduce time for calibration. It presents general formula and experiences at J-PARC RCS and parts of results are compared with the ordinal method at J-PARC MR.

• A.V. Fedotov
  BNL, Upton, Long Island, New York
• A.O. Sidorin, A.V. Smirnov
  JINR, Dubna, Moscow Region

Standard models of the intra-beam scattering (IBS) are based on the growth of the rms beam parameters for a Gaussian beam distribution. However, in many situations distribution can significantly deviate from Gaussian which requires accurate treatment of IBS. Our original interest in this problem was motivated for the need to have accurate description of beam evolution due to IBS while distribution is strongly affected by external electron cooling force [1]. A variety of models with various degrees of approximation were implemented in BETACOOL in the past to address this topic [2]. A more complete treatment based on the friction coefficient and full 3-D diffusion tensor was introduced in BETACOOL at the end of 2007 under the name “local IBS” [3]. Such a model allowed us calculation of IBS for arbitrary beam distributions. Numerical benchmarking of this local IBS model and its comparison with other models was reported before. Here, after briefly describing the model and its limitations, we present its comparison with available experimental data.

[1] A. Fedotov et al., Proc. of PAC05 (Knoxville, TN), p. 4263.
[2] http://betacool.jinr.ru; A. Sidorin et al., NIM A 558, p. 325 (2006).
[3] BNL BETACOOL development report, December 2007.

• H. Bartosik, Y. Papaphilippou
  CERN, Geneva

PS2 is a design study of a conventional magnet synchrotron considered to replace the existing PS at CERN. In this paper, studies on different aspect of single particle dynamics in the nominal PS2 Negative Momentum Compaction lattice are described. The global tuning flexibility of the ring and the geometric acceptance is demonstrated by a systematic scan of quadrupole settings. Frequency map analysis and dynamic aperture plots for two different chromaticity correction schemes are presented. The impact of magnet misalignments on the dynamic aperture is studied for one of them. A first study of the beam dynamics with magnetic multipole errors using frequency maps and the corresponding analytical tune-spread footprints is reported. It is thus demonstrated that multipole errors determine to a large extend the beam dynamics in PS2.

• S. Paret, O. Boine-Frankenheim
  GSI, Darmstadt

For the FAIR project, the intensity of heavy-ion beams in SIS-18 has to be increased by an order of magnitude. In order to achieve the design intensities, the efficiency of the multiturn injection from the UNILAC has to be optimized for high beam currents. This is especially important for the operation with intermediate charge state heavy-ions, where beam loss during injection will lead to pressure bumps and to a reduced lifetime of the beam. The multiturn injection into SIS-18 is studied by virtue of particle tracking simulations using an extended version of the computer code PATRIC. The impact of space charge and other intensity effects on the efficiency of the injection process is analyzed.

• D. Raparia, J.G. Alessi, B. Briscoe, J.M. Fite, O. Gould, V. Lo Destro, M. Okamura, J. Ritter, A. Zelenski
  BNL, Upton, Long Island, New York

The most important parameter for the high intensity linacs are the losses. The losses are about limited to 1W/m for the hand on maintenance requirements. This limit translates about 1 nA at 1 GeV and 100 nA at 10 MeV. Therefore less attention are paid to physics design low energy area, especially for the longitudinal plane which is responsible for the implanting non-linearity in the particle distribution which are often responsible for the losses at high energies. We will present upgrade for BNL 200 MeV linac in the low energy and medium energy transport system. We were able to reduce the transverse emittance by more than factor of two and losses in the entire linac complex by order of magnitude.

• S.L. Sheehy
  JAI, Oxford

The EMMA (Electron Model for Many Applications) accelerator is the world’s first non-scaling FFAG constructed at the Daresbury Laboratory, UK. Commissioning activities have recently been undertaken and beam dynamics results relevant to hadron non-scaling FFAGs are presented. The impact of these results on the future design of non-scaling FFAGs for high intensity hadron beam applications is discussed.

• T. Argyropoulos, T. Bohl, T.P.R. Linnecar, E.N. Shaposhnikova, J. Tuckmantel
  CERN, Geneva

Controlled longitudinal emittance blow-up together with a fourth harmonic RF system are two techniques that are being used in the SPS in order to stabilize the beam before injecting into the LHC. The emittance blow-up has been achieved by introducing a band-limited phase noise during acceleration. Measured variations of the final emittance along the batch can be explained by the modification of the synchrotron frequency distribution due to the effect of beam loading in a double harmonic RF system.

• P. Puppel, P.J. Spiller
  GSI, Darmstadt
• U. Ratzinger
  IAP, Frankfurt am Main

The StrahlSim code was developed to simulate dynamic vacuum effects and charge exchange beam loss in heavy ion accelerators. The code accounts for the charge exchange cross sections at the actual beam energy, the loss positions of charge exchanged ions, and the pressure rise caused by desorption due to the impact of these ions onto the vacuum chamber. Recent progress was made by implementing time dependent longitudinal pressure profiles in StrahlSim. This allows to simulate localized pressure bumps during a cycle and therefore to estimate the lifetime of NEG-coated surfaces depending on their positions in the ring, and the corresponding influence on the beam performance over the saturation process. The new code was applied to SIS18 considering two scenarios. One calculation has been carried out for the currently available U²⁸⁺ intensities of 2·10¹⁰ extracted particles per cycle, and the other calculation for the proposed FAIR booster operation with 1.5·10¹¹ extracted particles per cycle. Results for both scenarios will be presented in this work.

• S.J. Brooks
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon

Fixed-field strong focussing accelerators (FFAGs), in which the beam orbit moves with increasing momentum into higher field regions, have been widely studied. Less well-known is that the central orbit does not need to move outwards with energy: it can move in any direction including the vertically-moving orbit discussed in this paper. This allows for a magnet design with a smaller magnetised volume for a larger total energy range. A vertical analogue to the scaling FFAG is defined and its dynamic aperture studied for the case of an energy booster to the 800MeV ISIS synchrotron at RAL with various possible lattices.

• V. Kornilov, O. Boine-Frankenheim
  GSI, Darmstadt

Transverse bunch offsets typically occur after bunch-to-bucket transfer between synchrotrons. Decoherence of the oscillations can cause emittance growth and beam loss, which should be avoided in high-intensity synchrotrons, like the projected SIS-100 synchrotron of the FAIR project. In this contribution we investigate how space charge and impedances modify the bunch decoherence and associated diagnostics methods as turn-by-turn chromaticity measurements. Results of machine experiments at the SIS18 synchrotron are compared with particle tracking simulations.

• S. Sorge
  GSI, Darmstadt

The SIS-100 heavy ion synchrotron will play a key role within the future FAIR project underway at GSI. Although it is optimized for fast extraction, also slow extraction will be used. Slow extraction is based on the excitation of a third order resonance leading to the formation of a stable triangular phase space area. During the extraction process, particles leave this area along separatrices, where they pass the blade of the electro-static septum under a certain angle. Even in a low current regime the spread in the particle momenta leads to a spread in this angle which causes particle loss, in particular, at the blade of the electro-static septum. As a consequence the septum blade as well as the subsequent magnets will be irradiated. At high beam intensities space charge or electron clouds cause an additional tune spread which could increase the particle loss. In our study we model the extraction process and estimate the losses for high beam intensities.

• V.B. Reva, V.V. Parkhomchuk
  BINP SB RAS, Novosibirsk
• X.D. Yang
  IMP, Lanzhou

Electron cooling is used for damping both transverse and longitudinal oscillation of heavy particle. This effect is widely used in the existing and be designing storage rings. This article describes the last experiments with electron cooling carried out on the coolers (LEIR, EC-300, EC-35) produced by BINP. The ultimate sizes of the ion beam are discussed. The accumulated experience may be used for the project of electron cooler on 2 MeV (COSY) for obtaining high intensity proton beam with internal target. Using electron beam enables to have physics experiment with high quality of the ion beams at despite of the target interaction. The combination of the electron cooler with carbon storage ring can be used for cancer therapy because it enables to storage high number of the ion and to realize the original extraction scheme such as recombination or pellet extraction

• G. Clemente, W.A. Barth, L. Groening, S.G. Yaramyshev
  GSI, Darmstadt
• R. M. Brodhage, U. Ratzinger, R. Tiede
  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,

• S.M. Polozov, E.S. Masunov, A.V. Voronkov
  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

• S.M. Polozov, T.V. Bondarenko, E.S. Masunov, V.I. Rashchikov, A.V. Voronkov
  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

• Y. Zhang, S.M. Cousineau, Y. Liu
  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.

• A. Orzhekhovskaya, W.A. Barth, I. Hofmann, S.G. Yaramyshev
  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.

• R. Pakter, Y. Levin, T.N. Teles
  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).

• V.S. Dyubkov, S.M. Polozov
  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.

• L. Celona, G. Ciavola, S. Gammino
  INFN/LNS, Catania
• D. Mascali
  CSFNSM, Catania

The properties of ECRIS plasmas have been largely studied, however the design of new generation sources, able to provide high intensity beams of multiply charged ions, requires a more accurate investigation of both electron and ion dynamics. ECRIS have a broad electron energy distribution function (EEDF), not ideal for the safe operation of the sources, especially when superconducting magnets are used. X-rays measurements reveal a large amount of MeV electrons, that locally heat the cryostat and make the aging of the insulator faster. Conditions for the suppression of high energy particles must be understood in order to fully exploit the ECRIS ability to produce high brightness beams, and the plasma heating modelling permits a better insight. In addition, our approach takes into account the resonant nature of the plasma chamber, that has been confirmed by simulations and experiments: slight variations of frequency change the pattern of the electromagnetic field over the resonance surface, thus affecting the EEDF. A model has been developed to link the electron and ion dynamics, explaining how the beam properties are influenced by slight variations of the pumping frequency.

• D. Fernandez-Cañoto, I. Bustinduy, D. de Cos
  ESS Bilbao, Bilbao
• F.J. Bermejo
  Bilbao, Faculty of Science and Technology, Bilbao
• J. Feuchtwanger, J.L. Munoz
  ESS-Bilbao, Zamudio

The goal of extracting high proton currents from the ECR source of the Bilbao Accelerator has required comprehensive and interactive studies by using systematic beam dynamics simulations to derive acceptable geometric parameters for the projected electrode extraction system. Two tetrode designs were mainly analyzed; the first is based on a Pierce geometry; and the second on a spherically convergent extraction system. Both designs consist of a plasma electrode at 75kV, and then, a puller system formed by a grounded electrode separated from the plasma chamber to a certain extraction-gap distance, an electron repeller electrode fed at -3kV, and finally a grounded electrode. Geometric parameters such as the distances between electrodes, the different electrode apertures, the plasma electrode angle related to the Pierce layout, and also, the plasma and extraction electrode radial shapes related to the spherical extractor design were optimized for a 70mA proton beam.

• B. Goddard, M.J. Barnes, W. Bartmann
  CERN, Geneva

A new 450 GeV/c extraction kicker concept has been investigated for the SPS, based on open C-type kickers and a fast-bumper system. The beam is moved into the kicker gap only a few ms before extraction. The concept is illustrated in detail with the LSS4 extraction in the SPS – very similar parameters and considerations apply to the other fast extraction system in LSS6. A similar concept could also be conceived for injection but is more difficult due to the larger beam size. The technical issues are presented and the potential impact on the machine impedance is discussed.

• V.P. Nagaslaev, J.F. Amundson, J.A. Johnstone, L. Michelotti, C.S. Park, S.J. Werkema
  Fermilab, Batavia
• M.J. Syphers
  MSU, East Lansing, Michigan

The current design of beam preparation for a proposed mu->e conversion experiment at Fermilab is based on slow resonant extraction of protons from the Debuncher. The Debuncher ring will have to operate with beam intensities of 2-3 x 10**{12} particles, approximately four orders of magnitude larger than its current value. The most challenging requirements on the beam quality are the spill uniformity and low losses in the presence of large space charge and momentum spread. We present results from simulations of third integer resonance extraction assisted by RF knock-out (RFKO), a technique developed for medical accelerators. Tune spreads up to 0.05 have been considered.

• S.M. Cousineau, J.A. Holmes, M.A. Plum
  ORNL, Oak Ridge, Tennessee
• W. Lu
  ORNL RAD, Oak Ridge, Tennessee

We use the ORBIT particle tracking code to simulate the propagation of 545 keV electrons stripped from 1 GeV H^- ions during injection into the Spallation Neutron Source accumulator ring. The electrons propagate in the field of the injection magnet and are subject to scattering at the bottom surface when they are not caught by the electron catcher in the design fashion. The scattered electrons have the potential to intercept and damage local hardware. We model the non-caught electrons and compare our simulated results with experimental observations.

• O. Heid, T.J.S. Hughes
  Siemens AG, Healthcare Technology and Concepts, Erlangen

An RF accelerator driver concept is introduced, which integrates a distributed solid-state RF power source with the RF resonator. The resulting structure plays a double role as RF combiner and particle accelerating structure [1]. The key enabling technologies are Silicon Carbide RF transistors and a power combiner concept which includes insulating parallel cavities to ensure consistent RF current injection. An experimental direct drive λ/4 cavity with a power rating of 500kW at 150MHz has been constructed. The Direct Drive RF power source consists of 64 RF modules constructed from Silicon Carbide vJFETs, radial power combiner and isolation cavity. The initial results from the integration of the direct drive RF source are presented. These results demonstrate experimentally for the first time the validity of the direct drive concept and the key characteristics of such a drive.

[1] O. Heid, T Hughes. "Compact Solid State Direct Drive RF LINAC" presented at IPAC 2010, Kyoto, Japan.

• D.E. Johnson, A.I. Drozhdin, I.L. Rakhno, L.G. Vorobiev
  Fermilab, Batavia
• T.V. Gorlov
  ORNL, Oak Ridge, Tennessee
• D. Raparia
  BNL, Upton, Long Island, New York

One of the initial motivations for replacing the aging Fermilab Proton Source was to support the 120 GeV Neutrino program at the 2 MW level while supporting a broad 8 GeV Physics program. Over the years the design parameters of the new Proton Source have evolved from the 2005 Proton Driver configuration of a 2MW 8 GeV pulsed H^- linac injecting directly into the Main Injector or Recycler ; to a 2MW 2 GeV CW linac supporting a 2 GeV Experimental Program while injecting into a new 2-8 GeV Rapid Cycling Synchrotron which would then supply protons to the Main Injector. The current design parameters of the project include a 3 GeV CW linac accelerating up to 1 mA (average) H^- and a 3 GeV Experimental Area with the connection to the Main Injector Complex as an upgrade. Whether the upgrade path includes a new 6(or 8)GeV CW or pulsed linac, or 3 to 8 GeV RCS and the ultimate linac current remains to be determined. The basic issues of injection insertion design, foil and laser stripping options, foil survivability and loss issues will be discussed in context of the present options. Both analytical estimates and simulation results will be discussed.

• T. Yokoi
  OXFORDphysics, Oxford, Oxon
• K.J. Peach, H. Witte
  JAI, Egham, Surrey

PAMELA (Particle Accelerator for MEdicaL Application) is a design study of particle therapy facility using FFAG. PAMELA lattice realizes stable betatron tune with relatively small orbit excursion for a field accelerator with the help of newly developed combined function magnet. In addition, it can flexibly change the operating point, The feature puts PAMELA in a unique position among fixed field accelerators. The challenge of the beam extraction in PAMELA is the variability of extraction energy. Though the feature is desirable tto improve the beam quality for treatment, it was hard to realize for a fixed field accelerator due to orbit excursion introduced by the fixed field nature. The small orbit excursion of PAMELA provides a possibility to realize it. To tackle the problem, PAMELA employed vertical extraction with large gap kicker magnet, which is one of the major R&D items of the project. . In the presentation, the extraction scheme, status of hardware development and other approach of extraction PAMELA lattice will be presented.

• D. Wollmann, R.W. Assmann, R. Bruce, S. Redaelli, A. Rossi
  CERN, Geneva

The LHC has two dedicated cleaning insertions: IR3 for momentum cleaning and IR7 for betatron cleaning. During the first months of beam experience the presently installed Phase-I system performed as predicted earlier in detailed studies with tracking simulations. As the current system is not sufficient to allow LHC operation with nominal or ultimate intensity at 7TeV/c, simulations with an upgraded system are ongoing to overcome these limitations. In this contribution a collimation scheme with combined momentum and betatron cleaning in IR3 with additional collimators in the IR3 dispersion suppressor is presented. The predicted improvements compared to the Phase-I system and the limitations of this scheme are discussed.

• C. Bracco, R.W. Assmann, W. Bartmann, C. Boucly, R. Bruce, E. Carlier, B. Dehning, B. Goddard, E.B. Holzer, M. Meddahi, A. Nordt, S. Redaelli, A. Rossi, M. Sapinski, J.A. Uythoven, D. Wollmann
  CERN, Geneva

A single-sided mobile diluter (TCDQ) and a horizontal secondary collimator(TCSG) are installed in the extraction region of the LHC to protect the downstream elements from damage in case of asynchronous beam dump. These collimators have to be precisely setup to shield the arc aperture at 450 GeV, the triplet apertures and the tungsten tertiary collimators (TCT) at the low-beta collision points. During the LHC beam commissioning, several machine protection tests were carried out to validate collimator setup and hierarchy at different beam energies and intensities. The outcomes of these measurements are presented in this paper together with the results of particle tracking simulations for asynchronous beam dump. These studies allowed to quantify the leakage expected from dump protection collimators to the downstream elements, and to validate the system performance towards higher beam intensity.

• B. Goddard, R.W. Assmann, W. Bartmann, C. Bracco, E. Carlier, V. Kain, M. Meddahi, A. Nordt, S. Redaelli, J.A. Uythoven, J. Wenninger
  CERN, Geneva

The LHC transfer lines, injection and beam dump systems are equipped with a series of active and passive protection systems. These are designed to prevent as many failures as possible, for example through surveillance and interlocking, or to absorb any beam which is mis-kicked or mis-steered on passive absorbers. The commissioning, validation tests and performance of the different systems are described, and the implications for the protection of the LHC against different failures during beam transfer are discussed.

• X. Zhang, G.F. Kuznetsov, G.W. Saewert, V.D. Shiltsev, G. Stancari, A. Valishev
  Fermilab, Batavia
• V. Kamerdzhiev
  FZJ, Jülich

The long term performance of Tevatron Electron Lenses (TEL1 and TEL2) are summarized. Both of them are operated reliably. Besides their main function as DC beam cleaner, TEL2 is also a test bed for beam-beam compensation, space charge compensator and soft collimator. And its operation as collimator will be tested after the installation of the new electron gun with hollow cathode in planed summer shutdown peroid.

• V. Kain, W. Bartmann, C. Bracco, B. Goddard, W. Höfle, D. Karadeniz, M. Meddahi, D. Valuch, J. Wenninger
  CERN, Geneva

The very demanding LHC beam parameters put very strict requirements on the beam quality along the SPS-to-LHC transfer. In particular, the budget for the emittance increase is very tight. During the LHC commissioning, the emittances have been measured in the SPS, the two SPS-to-LHC transfer lines and in the LHC. Preliminary results show the importance of a very well controlled beam steering in the transfer lines together with the need of a robust trajectory correction strategy in order to guarantee long-term reproducibility. Another source of emittance comes from the tilt mis¬match be¬tween the LHC and its trans¬fer lines which generates cou¬pling at in¬jec-tion into the LHC and in turn will contribute to emittance increase. Preliminary results are also discussed.

• H. Damerau, S. Hancock, M. Schokker
  CERN, Geneva

As one of the pre-injectors for the Large Hadron Collider, the CERN Proton Synchrotron must reliably deliver a wide range of beam parameters. The large variety of bunch spacings from 25 to 150 ns at extraction requires the acceleration of small, high-density bunches as well as highly intense ones. Above a threshold bunch density, longitudinal coupled-bunch instabilities are observed after transition crossing and the main accelerating cavities have been identified as part of the impedance driving them. Transient beam loading causes asymmetries of the various bunch splittings used to establish the required bunch spacing, compromising beam quality at the head of the bunch train delivered. Recent measurements and longitudinal limitations of beams for the LHC are presented, together with possible cures and options for future hardware improvements.

• M. Sapinski, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, C. Kurfuerst, A. Priebe, C. Zamantzas
  CERN, Geneva

To prevent from beam-induced quenches of the superconducting magnets a system of about 4000 beam loss detectors is installed on the magnets cryostats. These detectors, being ionization chambers, measure the particle shower starting inside the magnet. Examples of simulations linking the heat deposited in the superconducting coils with signals in the ionization chambers are presented. A comparison of the simulations to the data is done. Limits of the present system are discussed.

• S. Redaelli, M. Lamont, G.J. Müller, R.J. Steinhagen, J. Wenninger
  CERN, Geneva
• X. Buffat
  EPFL, Lausanne

The energy ramp and the betatron squeeze at the CERN Large Hadron Collider (LHC) are particularly critical operational phases that involve the manipulation of beams well above the safe limit for damage of accelerator components. In particular, the squeeze is carried out at top energy with reduced quench limit of superconducting magnets and reduced aperture in the triplet quadrupoles. In 2010, the commissioning of the ramp from 450 GeV to 3.5 TeV and the squeeze to 2 m in all the LHC experiments has been achieved and smoothly became operational. In this paper, the operational challenges associated to these phases are discussed, the commissioning experience with single- and multi-bunch operation is reviewed and the performance during standard operation is presented.

• C. Wang, A. Adelmann, Y. Ineichen
  PSI, Villigen

Dark current and multipacting phenomena, have been observed in accelerator structures, and are usually harmful to the equipment and the beam quality. These effects need to be suppressed to guarantee stable operation. Large scale simulations can be used to understand the origin and develop cures of these phenomena. We extend OPAL, a parallel framework for charged particle optics in accelerator structures and beam lines with the necessary physics to simulate multipacting phenomena. We add a Fowler-Nordheim field emission model and secondary emission model, as well as 3D boundary geometry handling capabilities to OPAL. These capabilities allows us to evaluate dark current and multipacting in high-gradient linac structures and in RF cavities of high intensity Cyclotrons. The electric field in present accelerator structures is high enough, such that space charge effects in the Fowler-Nordheim model can not be neglect. First a Child-Langmuir model is added to phenomenologically model space charge limited field emission. In a second step a space charge solver capable of handling complicated boundary geometries will be implemented to make our field emission model more self-consistent.

• A.P. Shishlo
  ORNL, Oak Ridge, Tennessee

The review of the simulations tools used for the Spallation Neutron Source (SNS) linac tuning and beam dynamics studies is presented. The usage and comparison of the different approaches like single-particle, envelope, particle-in-cell and codes for particular tasks is discussed. The used codes include Parmila, Impact, Track, XAL online model, and a linac model based on the pyORBIT ring code. The future code development for SNS linac is suggested.

• M.V. Maltseva
  TENZOR, Dubna, Moscow region
• A.A. Maltsev
  JINR, Dubna, Moscow Region

A diagnostic instrument in which a combination of a plastic scintillator and a solid-state photomultiplier is used as a nuclear radiation detector, is described. The detector is designed to record x-ray, gamma-ray, and neutron radiation in high-intensity proton beams accelerators.

• D. Reggiani, M. Seidel
  PSI, Villigen
• C.K. Allen
  ORNL, Oak Ridge, Tennessee

Operation and upgrade of very intense proton beam accelerators like the PSI facility and the SNS spallation source at ORNL is typically constrained by potentially large machine activation. Besides the standard beam diagnostics, beam tomography techniques provide a reconstruction of the beam transverse phase space distribution, giving insights to potential loss sources like irregular tails or halos. Unlike more conventional measurement approaches (pepper pot, slits) beam tomography is a non destructive method that can be performed at high energies and, virtually, at any beam location. Results from the application of the Maximum Entropy Tomography (MENT) algorithm to different beam sections at PSI and SNS will be shown. In these reconstructions the effect of nonlinear forces is made visible in a way not otherwise available through wire scanners alone. These measurements represent a first step towards the design of a beam tomography implementation that can be smoothly employed as a reliable diagnostic tool.

• T.G. Xu, S. Fu, L.X. Han, T. Huang, W. Kang, F. Li, P. Li, H.C. Liu, H.F. Ouyang, J. Peng, Y.F. Ruan, J.L. Sun, J.M. Tian, A.X. Wang, B. Wang, S. Xiao, Y.S. Zhu
  IHEP Beijing, Beijing
• C. Chen, M.H. Xu
  Institute of High Energy Physics, Beijing

A high intensity RFQ has been built with an energy of 3.5 MeV and an average current of 3 mA. Based on this RFQ, we plan on performing a number of experimental tests on beam loss control. A series of beam diagnostic devices such as BPM, BLM, WS have thus been developed. Our work can also be easily applied to the CSNS project.

• R. Singh, P. Forck, P. Kowina, P. Moritz, U. Rauch
  GSI, Darmstadt
• T. Weiland
  TEMF, TU Darmstadt, Darmstadt

To achieve a high current operation close to space charge limit, a precise tune measurement during a full accelerating cycle is required. A tune measurement system was recently commissioned at GSI SIS-18, which allows calculation of tune using digital position data. It consists of three distinct parts; an exciter which provides band limited white noise to excite coherent betatron oscillations in the beam. The fast ADCs digitize the BPM signals at 125MSa/s and the post processing electronics integrate the data bunch by bunch to acquire one position value per bunch. Subsequently base band tune is determined by frequency transformation of the position data. Using this system, the charge effects were studied by correlating the current levels to tune spread/shift in the GSI synchrotron SIS-18. The experiment was conducted at injection energy of 11.6 Mev/nucleon using U⁷³⁺.

• M. Sapinski, B. Dehning, A. Guerrero, T. Kroyer, M. Meyer
  CERN, Geneva

Carbon fibers are commonly used as moving targets in the beam wire scanners. The heating of the fiber due to energy loss of the particles traveling through is simulated with Geant4. Heating induced by the beam electromagnetic field is estimated with ANSYS. The heat transfer and sublimation processes are modeled. Due to the model nonlinearity a numerical approach based on discretization of the wire movement is used to solve it for particular beams. Radiation damage to the fiber is estimated with SRIM. The model is tested with available SPS and LEP data and a dedicated damage test on SPS beam is performed followed by post-mortem analysis of the wire remnants. Prediction for the LHC beams is made.

• R. Dölling
  PSI, Villigen

The longitudinal-horizontal 2-dimensional (2D) density distribution of a bunched 2.2 mA beam of ~72 MeV protons has been measured at the last turns of the Injector 2 cyclotron, in the middle of the transfer line to and at the first turns of the Ring cyclotron. Protons scattered by a thin carbon-fibre target are stopped in a scintillator-photomultiplier detector. The longitudinal bunch shape is given by the distribution of arrival times measured with respect to the 50 MHz reference signal from the acceleration cavities. More probes are foreseen at 72 and 590 MeV which will use additional fibres to also determine the longitudinal-vertical and two longitudinal-diagonal 2D density distributions. These measurements together with more detailed beam transport calculations will support the matching of beam core and halo and the quest for a reduction of beam losses. The achievable dynamic range in the given environment of the cyclotrons and the connecting beam line is discussed.

• A. Nordt, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, D.K. Kramer, E. Lebbos, M. Sapinski, M. Stockner, C. Zamantzas
  CERN, Geneva

The LHC beam loss monitoring system is a safety critical system and ~ 4000 monitors are installed around the ring in order to prevent the superconducting magnets from quenches and protect the machine components from damage. Two different types of beam loss monitors are used: an ionization chamber (IC) and a secondary emission monitor (SEM). The response functions and expected signals have been simulated using Geant4 as well as FLUKA and have been validated and verified with measurements. The Geant4 model of the beam loss monitors has been tested with protons, gammas, neutrons, muon and mixed field beams for steady state and instantaneous losses. Results from the simulations compared to measurement results will be presented. The expected signals for several events (e.g. direct beam impact on collimators, over-injection, high intensity injection) have been checked against real data being taken during the LHC runtime in 2009 and 2010. The very good performance of the system and the agreement with previous simulations will be shown and discussed.

• A. Strinning, S.R.A. Adam, P. Baumann, V. Gandel, D.C. Kiselev, Y. Lee
  PSI, Villigen

In March 2010 one of the most exposed collimators of the 590 MeV proton beam line at PSI, was visu-ally inspected after 20 years of operation without failure. It is made out of OFHC copper and cooled by water tubes. At currents of 2.2 mA, the temperature inside the collimator is ~ 350 C. From the total beam charge of 120 Ah, ~15 % are absorbed. The main motivation for the inspection was to investigate the present condition of the collimator after the long exposure in a high intensity proton beam. According to MARS15 the inner parts have seen 35 DPA. For the inspection, the collimator was removed remotely from the beam line by a shielded exchange flask and transferred to the hot cell. In order to enter the collimator opening and examine the inner structure without any contact or damage, a special tool was built, using the principle of a periscope. By moving and rotation the tool with the power manipulator, sharp pictures of the inner surface were taken with a high resolution reflex camera, operated remotely. Because of the high radiation (> 50 Sv/h in 0.2 m) camera and electronics were shielded. After the inspection, the collimator was built in to the beam line again.

• V. Chetvertkova, E. Mustafin
  GSI, Darmstadt
• V. Chetvertkova, U. Ratzinger, I. Strašík
  IAP, Frankfurt am Main
• L.N. Latysheva, N. Sobolevskiy
  RAS/INR, Moscow

The research into the activation of materials used for accelerator components is held in GSI as a part of studies of FAIR relevant materials. In the frame of these studies the project "Verification of Monte Carlo transport codes: FLUKA, MARS and SHIELD" was started. Series of irradiations were already done. This work presents the results of irradiation of aluminum target with uranium beam. Experimentally achieved depth profiles of residual activity and stopping range of primary ions are compared with Monte Carlo simulations. Correspondences and discrepancies of different codes with experiment are discussed.

• J. Tang, J.F. Chen, Y. Zou
  IHEP Beijing, Beijing

Momentum collimation in a high intensity RCS is a very important issue. Based on the two-stage collimation principle, a combined momentum collimation method is proposed and studied here. The method makes use of the combination of secondary collimators in both the longitudinal and transverse planes. The primary collimator is placed at a high-dispersion location of an arc, and the transverse and longitudinal secondary collimators are in a dispersion-free long straight section and in an arc, respectively. The particles with a positive momentum deviation will be scattered by a carbon scraper and then cleaned by the transverse collimators, whereas the particles with a negative momentum deviation will be scattered by a Tantalum scraper and cleaned by the longitudinal secondary collimators. This is due that a carbon foil produces relatively more scattering than a Tantalum foil if the energy loss is kept the same. The relevant requirements on the lattice design are also discussed, especially for compact rings. The multi-particle simulations using both TURTLE and ORBIT codes are presented to show the physical images of the collimation method, with the input of the CSNS RCS ring.

• J. Blanco, R. Schmidt
  CERN, Geneva
• N.A. Tahir
  GSI, Darmstadt

The Large Hadron Collider and the next future linear accelerators deal with extraordinary high beam energies (in the order of hundreds of mega-Joules for LHC) and with increasingly smaller beam sizes. It is important to understand the damage potential of such high energy beams to accelerator equipment and surroundings. Simulations have shown that the impact of the full LHC beam into copper can penetrate up to 35m as opposed to 140cm that is the typical penetration length for 7TeV protons. It becomes evident that when working with high energy densities, it is no longer possible to neglect the hydro-dynamic. A hybrid approach combining FLUKA and BIG-2 is proposed to treat HED problems. This approach can improve current simulations. It is foreseen to experimentally irradiate different materials with different beam intensities in the SPS-HiRadMat facility at CERN. First, these experiments will validate the simulation results by reproducing the density depletion along the beam path. Finally, the information obtained with these tests will be very useful in the understanding of the consequences of beam-matter interaction. Results could be applied to the LHC Beam Dump system,collimation…

* N.A.Tahir, R.Schmidt et al., Nucl. Instrum. Methods Phys. Res., A 606 (2009)
** N.A.Tahir, R.Schmidt, New J. Phys.10 (2008) 073028
*** N.A.Tahir, R.Schmidt et al., J. Appl. Phys.97 (2005) 083532

• W. Scandale, R. Losito
  CERN, Geneva
• A.M. Taratin
  JINR, Dubna, Moscow Region

The probability of inelastic nuclear interaction in crystals well aligned to the incoming beam is considerably smaller than for its amorphous orientation. Tests performed with 400 GeV/c protons of the CERN SPS and a short bent silicon crystal confirm this behavior: channeled protons interact with crystal nuclei at a rate more that 20 times smaller than protons with randomly oriented trajectories. On the other hand, the quasi parallel beam halo in a collider has a large probability of being channeled in a bent silicon crystals. Tests performed with 120 GeV stored protons in the SPS show that the inelastic nuclear losses decrease by more than five times when the silicon crystal is well oriented respect to the beam envelope. These observations suggest that bent silicon crystals used as a primary collimator in a hadron collider, such as the LHC, will produce a considerably reduced flux of nuclear losses respect to an amorphous material.