• F. Méot
  CEA, Gif-sur-Yvette
• N. Monseu
  LPSC, Grenoble Cedex

Lattice design tools are being developed, and related beam and spin dynamics simulations are being performed, in the framework of the international collaboration regarding the super-B project. The present contribution reports on this work.

• D. Alesini, A. Battisti, O. Coiro, T. Demma, S. Guiducci, V. Lollo, C. Milardi, P. Raimondi, M. Serio, R.S. Sorchetti, M. Zobov
  INFN/LNF, Frascati (Roma)

Metallic clearing electrodes have been designed to absorb the photo-electrons in the DAΦNE positron ring. They have been inserted in the wigglers and dipoles vacuum chambers and have been connected to external high voltage generators. In the paper we present the design of the devices and the results of the electromagnetic simulations related to both the transfer and longitudinal beam coupling impedances. We also present the results of the RF measurements and the first results with the DAΦNE circulating positron beam.

• M.E. Biagini, D. Alesini, R. Boni, M. Boscolo, T. Demma, A. Drago, M. Esposito, S. Guiducci, F. Marcellini, G. Mazzitelli, M.A. Preger, P. Raimondi, C. Sanelli, M. Serio, A. Stecchi, A. Stella, S. Tomassini, M. Zobov
  INFN/LNF, Frascati (Roma)
• M.A. Baylac, J.-M. De Conto, Y. Gomez-Martinez, N. Monseu, D. Tourres
  LPSC, Grenoble
• K.J. Bertsche, A. Brachmann, Y. Cai, A. Chao, M.H. Donald, A.S. Fisher, D. Kharakh, A. Krasnykh, N. Li, D.B. MacFarlane, Y. Nosochkov, A. Novokhatski, M.T.F. Pivi, J. Seeman, M.K. Sullivan, A.W. Weidemann, J. Weisend, U. Wienands, W. Wittmer, A.C. de Lira
  SLAC, Menlo Park, California
• S. Bettoni
  CERN, Geneva
• B. Bolzon, L. Brunetti, A. Jeremie
  IN2P3-LAPP, Annecy-le-Vieux
• J. Bonis, G. Le Meur, B.M. Mercier, F. Poirier, C. Prevost, C. Rimbault, F. Touze, A. Variola
  LAL, Orsay
• F. Bosi
  INFN-Pisa, Pisa
• A. Chancé, F. Méot, O. Napoly
  CEA, Gif-sur-Yvette
• R. Chehab
  IN2P3 IPNL, Villeurbanne
• I. Koop, E.B. Levichev, S.A. Nikitin, P.A. Piminov, D.N. Shatilov, S.V. Sinyatkin
  BINP SB RAS, Novosibirsk
• S.M. Liuzzo, E. Paoloni
  University of Pisa and INFN, Pisa

The SuperB project is an international effort aiming at building in Italy a very high luminosity e⁺e^- (10³⁶ cm^-2 sec^-1) asymmetric collider at the B mesons cm energy. The accelerator design has been extensively studied and changed during the past year. The present design, - based on the new collision scheme, with large Piwinski angle and the use of 'crab' sextupoles, which has been successfully tested at the DAPHNE Phi-Factory at LNF Frascati, - provides larger flexibility, better dynamic aperture and in the Low Energy Ring spin manipulation sections, needed for having longitudinal polarization of the electron beam at the Interaction Point. The Interaction Region has been further optimized in terms of apertures and reduced backgrounds in the detector. The injector complex design has been also updated. A summary of the design status, including details on lattice and spin manipulation will be presented in this paper.

• Y. Nosochkov, W. Wittmer
  SLAC, Menlo Park, California
• M.E. Biagini, P. Raimondi
  INFN/LNF, Frascati (Roma)
• P.A. Piminov, S.V. Sinyatkin
  BINP SB RAS, Novosibirsk

The Super-B asymmetric e⁺e^- collider is designed for 10³⁶ cm^-2sec^-1 luminosity and beam energies of 6.7 and 4.18 GeV for e⁺ and e-, respectively. The machine will have the High and Low Energy Rings (HER and LER), and one Interaction Point (IP) with 60 mrad crossing angle. The INFN-LNF at Frascati is one of the proposed sites, and a lattice for short 1.3 km rings fitting to this site has been designed. The two rings are radially separated by 2 m except near the IP and in the dogleg on the opposite side of the rings. The injection sections and RF cavities are included. The lattice is optimized for a low emittance required for the desired high luminosity. Final Focus chromaticity correction is optimized for large transverse and energy acceptance. The "crab waist" sextupoles are included for suppression of betatron resonances induced at the IP collisions with large Piwinski angle. The LER spin rotator sections provide longitudinal polarization for the electron beam at IP. The lattice is flexible for tuning the design parameters and compatible with reusing the PEP-II magnets, RF cavities and other components. Design criteria and details on the lattice implementation are presented.

• C. Milardi, M.A. Preger, P. Raimondi, G. Sensolini, F. Sgamma
  INFN/LNF, Frascati (Roma)

An innovatory interaction region has been recently conceived and realized on the Frascati DAΦNE lepton collider. The concept of tight focusing and small crossing angle adopted until now to achieve high luminosity in multibunch collisions has evolved towards enhanced beam focusing at the interaction point with large horizontal crossing angle, thanks to a new compensation mechanism for the beam-beam resonances. The novel configuration has been tested with a small detector without solenoidal field yielding a remarkable improvement in term of peak as well as integrated luminosity. The high luminosity interaction region has now been modified to host a large detector with a strong solenoidal field integral which significantly perturbs the beam optics introducing new design challenges in terms of interaction region optics design, beam transverse coupling control and beam stay clear requirements.

• C. Milardi, D. Alesini, M.E. Biagini, C. Biscari, R. Boni, M. Boscolo, F. Bossi, B. Buonomo, A. Clozza, G.O. Delle Monache, T. Demma, E. Di Pasquale, G. Di Pirro, A. Drago, M. Esposito, A. Gallo, A. Ghigo, S. Guiducci, C. Ligi, F. Marcellini, G. Mazzitelli, L. Pellegrino, M.A. Preger, L. Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Zobov
  INFN/LNF, Frascati (Roma)
• S. Bettoni
  CERN, Geneva
• E.B. Levichev, S.A. Nikitin, P.A. Piminov, D.N. Shatilov
  BINP SB RAS, Novosibirsk

Recently the peak luminosity achieved on the DAΦNE collider has been improved by almost a factor 3 by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for physics research and a new run with the KLOE-2 detector has been scheduled to start by spring 2010. The KLOE-2 installation is a complex operation requiring a careful design effort and a several months long shutdown. The high luminosity interaction region has been deeply revised in order to take into account the effect on the beam caused by the solenoidal field of the experimental detector and to ensure background rejection. The shutdown has been also used to implement several other modifications aimed at improving beam dynamics: the wiggler poles have been displaced from the magnet axis in order to cancel high order terms in the field, the feedback systems have been equipped with stronger power supplies and more efficient kickers and electrodes have been inserted inside the wiggler and the dipole vacuum chambers, in the positron ring, to avoid the e-cloud formation. A low level RF feedback has been added to the cavity control in both rings.

• S.M. Liuzzo
  University of Pisa and INFN, Pisa
• M.E. Biagini, P. Raimondi
  INFN/LNF, Frascati (Roma)
• M.H. Donald
  SLAC, Menlo Park, California

SuperB is an international project for an asymmetric 2 rings collider at the B mesons cm energy to be built in the Rome area in Italy. The two rings will have very small beam sizes at the Interaction Point and very small emittances, similar to the Linear Collider Damping Rings ones. In particular, the ultra low vertical emittances, 7 pm in the LER and 4 pm in the HER, need a careful study of the misalignment errors effects on the machine performances. Studies on the closed orbit, vertical dispersion and coupling corrections have been carried out in order to specify the maximum allowed errors and to provide a procedure for emittance tuning. A new tool which combines MADX and Matlab routines has been developed, allowing for both corrections and tuning. Results of these studies are presented.

• M. Masuzawa, K. Egawa, T. Kawamoto, Y. Ohsawa, T. Sueno, N. Tokuda
  KEK, Ibaraki

A new set of magnets, skew sextupole magnets, were designed, manufactured, measured and installed during the winter shutdown of 2009. Twenty magnets were installed in the HER and eight magnets were installed in the LER. It was a challenging job for the magnet group to design, manufacture, measure the magnetic field and install them in the tunnel in just three months. Much effort to finish the installation in time and reduce the production cost was made at every step of the entire process. With these newly installed skew sextupole magnets, a significant luminosity boost was achieved. The production and installation of the skew sextupole magnets are described in this report.

• Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki, S. Takano
  KEK, Ibaraki

Eight superconducting accelerating cavities have been stably operated in the KEKB with sufficiently low trip rates. Two superconducting crab cavities were installed in 2007 and soon the crab crossing operation started. Recently the KEKB luminosity reached the world record of 2.1 x 10³⁴ cm^-1s^-1. Stable operations of the accelerating cavities contributed for the luminosity increase. For the future Super-KEKB, we are developing a high power coupler for an input power of 600 kW and a HOM damper for RF power absorption more than 30 kW. The Super-KEKB requires RF operations with the high beam loading and the low RF voltage than the present KEKB operation. To suppress klystron output powers the external Q value has to be reduced. A new operation was proposed for superconducting cavities. In order to keep high RF voltages in each cavity, some cavities reverse its synchronous beam phase while the total RF voltage is kept as low as the required one. Beam studies were successfully carried out with one cavity reversed its synchronous beam phase.

• K. Ohmi, T. Ieiri, Y. Ohnishi, Y. Seimiya, M. Tejima, M. Tobiyama, D.M. Zhou
  KEK, Ibaraki

Optics parameters at the interaction point, beta, x-y coupling, dispersion and their chromatic aberrations, seriously affect the beam-beam performance as is shown in experiments and simulations. The control of the optics parameters is essential to maintain the high luminosity in KEKB. They drift day by day, or before and after the beam abort. They were often monitored at intervals of the operation with taking the study time. They are recently measured during the physics run using a pilot bunch without collision. We show the measured the optics parameters and their variations and discuss the relation to the luminosity.

• K. Ohmi
  KEK, Ibaraki

Super B factories are designed with very low emittance and very low beta function at the interaction point. The two beams collide with a large crossing angle, thus the overlap area of the beams is limited at a small part of their length. Simulation of the beam-beam effects is hard because of the longitudinal slice of the beam is the order of 100. We discuss two methods for the simulation. One is a simplified method, which is mixture of the particle in cell and Gaussian approximation. The other is fully strong-strong simulation using the particle in cell. The shifted Green function is used to calculate the beam-beam force for less overlap of the beam distribution. Luminosity and its degradation due to IP optics errors in Super B factories are discussed.

• Y. Susaki, K. Ohmi
  KEK, Ibaraki

Single bunch instability caused by electron cloud can depend on emittance, because the electron oscillation period in positron bunch is large. The single bunch instability should appear as a head-tail motion with synchro-beta frequency. We discuss the single bunch instability in low emittance rings, CesrTA, Super B factories and ILC damping ring with focusing the threshold and synchro-beta oscillation.

• K. Ohmi, H. Koiso
  KEK, Ibaraki

Progress of Graphic Processor Unit (GPU) is marveled. The performance is 1TFlops per unit. Simulation of electron gun can be performed by particle-particle interactions, in which the calculation cost is NxN. Since the calculation of each interaction is very simple, GPU can demonstrate its ability. We show simulation results and discuss the possibilities to extend other simulations.

• D.M. Zhou, H. Koiso, A. Morita, K. Ohmi, Y. Ohnishi, Y. Seimiya
  KEK, Ibaraki

Using a weak-strong beam-beam code, in which the symplectic maps for the linear coupling and chromatic aberrations were implemented, the luminosity degradation caused by the linear and chromatic X-Y couplings at the interaction point (IP) were evaluated for the SuperKEKB project under design. The linear and chromatic X-Y couplings were estimated through modeling the machine errors using random seeds, based on a baseline design of the SuperKEKB rings. It was found that the linear and chromatic X-Y couplings can potentially degrade the luminosity performance.

• D.M. Zhou, T. Abe, H. Ikeda, M. Kikuchi, K. Ohmi, K. Oide, K. Shibata, M. Tobiyama
  KEK, Ibaraki
• G.V. Stupakov
  SLAC, Menlo Park, California

Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.

• M. Iwasaki, Y. Funakoshi, J. Haba, N. Iida, K. Kanazawa, H. Koiso, Y. Ohnishi, K. Shibata, S. Tanaka, T. Tsuboyama, S. Uno, Y. Ushiroda
  KEK, Ibaraki
• H. Aihara, C. Ng, S. Sugihara
  University of Tokyo, Tokyo
• H. Nakano, H. Yamamoto
  Tohoku University, Graduate School of Science, Sendai

SuperKEKB is the upgrade plan of the current B-factory experiment with the KEKB accelerator at KEK. Its luminosity is designed to be 8x10³⁵ /cm²/s (40 times higher than KEKB) and the integrated luminosity is expected to be 50 ab-1. In SuperKEKB, it is important to evaluate the beam induced BG and design the interaction region (IR) to assure the stable detector operation. To estimate the beam induced BG, we construct the beam-line simulation based on the GEANT4 simulation. In this paper, we report the BG evaluation and the IR design for SuperKEKB.

• Q. Qin, N. Huang, D. Ji, Y. Jiao, Y.D. Liu, Y.M. Peng, D. Wang, J.Q. Wang, N. Wang, X.H. Wang, Y. Wei, X.M. Wen, J. Xing, G. Xu, C.H. Yu, C. Zhang, Y. Zhang
  IHEP Beijing, Beijing
• Z. Duan
  IHEP Beiing, Beijing

As a tau-charm factory like collider, the upgrade project of the Beijing Electron Positron Collider (BEPCII), has reached its first design value of luminosity. During the commissioning of its luminosity, beam optics recovery, machine parameters measurement, detector solenoid compensation, and instability cure are main problems we met. Besides commissioning the machine, beams were delivered to the users from high energy physics and synchrotron radiation. This paper summarizes the accelerator physics issues in the BEPCII luminosity commissioning.

Supported by National Natural Sciences Foundation of China (10725525)

• Y. Alexahin, E. Gianfelice-Wendt, A.V. Netepenko
  Fermilab, Batavia

Muon collider is a promising candidate for the next energy frontier machine. However, in order to obtain peak luminosity in the 10³⁵/cm²/s range the collider lattice design must satisfy a number of stringent requirements, such as low beta at IP (beta*<1 cm), large momentum acceptance and dynamic aperture and small value of the momentum compaction factor. Here we present a particular solution for the interaction region optics whose distinctive feature is a three-sextupole local chromatic correction scheme. Together with a new flexible momentum compaction arc cell design this scheme allows to satisfy all the above-mentioned requirements and is relatively insensitive to the beam-beam effect.

• Y. Alexahin, E. Gianfelice-Wendt, V. Kashikhin, N.V. Mokhov, A.V. Zlobin
  Fermilab, Batavia
• V.Yu. Alexakhin
  JINR, Dubna, Moscow Region

Design of a muon collider interaction region (IR) presents a number of challenges arising from low beta* < 1 cm, correspondingly large beta-function values and beam sizes at IR magnets, as well as the necessity to protect superconducting magnets and collider detectors from muon decay products. As a consequence, the designs of the IR optics, magnets and machine-detector interface are strongly interlaced and iterative. A consistent solution for the 1.5 TeV c.o.m. muon collider IR is presented. It can provide an average luminosity of 10³⁴/cm²/s with an adequate protection of magnet and detector components.

• S.A. Kahn, G. Flanagan, R.P. Johnson
  Muons, Inc, Batavia

To achieve the high luminosity required for a muon collider strong quadrupole magnets will be needed for the final focus in the interaction region. These magnets will be located in regions with space constraints imposed both by the lattice and the collider detector. There are significant beam related backgrounds from muon decays and synchrotron radiation which create unwanted particles which can deposit significant energy in the magnets of the final focus region of the collider. This energy deposition results in the heating of the magnet which can cause it to quench. To mitigate the effects of heating from the energy deposition shielding will need to be included within the magnet forcing the aperture to be larger than desired and consequently reducing the gradient. We propose to use exotic high magnetization materials for pole tips to increase the quadrupole gradient.

• K.J. Bertsche, M.K. Sullivan
  SLAC, Menlo Park, California

We present an approach for compensating adverse effects of the detector solenoid in the SuperB Interaction Region (IR). We place compensating solenoids around the IR quadrupole magnets to reduce the magnetic fields nearly to zero. This allows more operational headroom for superconducting IR magnets and avoids saturation of ferric IR magnets. We place stronger compensating solenoids between IR magnets to reverse the magnetic field direction. This allows adjusting the total integrated solenoid field to zero, which eliminates coordinate plane rotation and reduces vertical beam displacements in the IR.

• M.K. Sullivan, R.C. Field, K. C. Moffeit, Y. Nosochkov, U. Wienands, W. Wittmer, M. Woods
  SLAC, Menlo Park, California

We present a conceptual design for a polarimeter based on Compton scattering of laser light on the electron beam for the Super-B accelerator proposed for Frascati, Italy. The accelerator design has polarized electrons in the low-energy ring (4.18 GeV). We want to measure the polarization of every bunch every few seconds using a laser with 119 Mhz repetition rate. The spin rotator section has a second point between the solenoids and interaction point where the polarization is nearly longitudinal with helicity opposite to that found at the interaction point. We plan to use this point to measure the polarization as the possible location near the interaction point has too much background from the collision. We show the area in the accelerator where the polarimeter would be installed and describe the laser as well as the detectors for the Compton scattered electrons and photons.

• A. Novokhatski, M.K. Sullivan
  SLAC, Menlo Park, California

We study the bunch field diffusion and energy dissipation in the beam pipe of the Super-B detector, which consists of two coaxial Be thin pipes (half a millimeter). Cooling water will run between these two pipes. Gold and nickel will be sputtered (several microns) onto the beryllium pipe. The Maxwell equations for the beam fields in these thin layers are solved numerically for the case of infinite pipes. We also calculate the amplitude of electromagnetic fields outside the beam pipe, which may be noticeable as the beam current can reach 4 A in each beam. Results of simulations are used for the design of this central part of the Super-B detector.

• M.K. Sullivan, K.J. Bertsche
  SLAC, Menlo Park, California
• S. Bettoni
  CERN, Geneva
• E. Paoloni
  University of Pisa and INFN, Pisa
• P. Raimondi
  INFN/LNF, Frascati (Roma)
• P. Vobly
  BINP SB RAS, Novosibirsk

A final focus magnet design that uses super-ferric magnets is introduced for the Super-B interaction region. The baseline design has air-core super-conducting quadrupoles. This idea instead uses super-conducting wire in an iron yoke. The iron is in the shape of a Panofsky quadrupole and this allows for two quadrupoles to be side-by-side with no intervening iron as long as the gradients of the two quads are equal. This feature allows us to move in as close as possible to the collision point and minimize the beta functions in the interaction region. The super-ferric design has advantages as well as drawbacks and we will discuss these in the paper.

• A. Novokhatski, M.K. Sullivan
  SLAC, Menlo Park, California

We discuss the feasibility of an application of an implicit finite-difference approximation to calculate the fields of a bunch moving with no restriction inside the vacuum chamber.

• U. Wienands, Y. Nosochkov, M.K. Sullivan, W. Wittmer
  SLAC, Menlo Park, California
• D.P. Barber
  Cockcroft Institute, Warrington, Cheshire
• M.E. Biagini, P. Raimondi
  INFN/LNF, Frascati (Roma)
• I. Koop, S.A. Nikitin, S.V. Sinyatkin
  BINP SB RAS, Novosibirsk

The availability of longitudinally polarized electrons is an important aspect of the design of the proposed SuperB project at LNF Frascati. Spin rotators are an integral part of the design of the Interaction Region (IR). We have chosen a solenoid-dipole design; at the 4.18 GeV nominal energy this is more compact that a design purely based on dipole magnets. Integration with the local chromaticity correction of the ultra-low beta* IR has been achieved. The spin rotators are symmetric about the Interaction Point, this design saves a significant amount of length as the dipoles become a part of the overall 360 deg. bend. The layout leaves limited opportunity to setup the optics for minimum depolarization; this is acceptable since beam life time in SuperB at high luminosity is only about 5 min and up-to 90% polarized electrons will be injected continuously. In this way an average beam polarization of about 70% is maintained. Simulations and analytic estimates with the DESY code SLICKTRACK and other codes indicate such operation is feasible from a spin-dynamics point of view. The paper will discuss the overall spin-rotator design as well as the spin dynamics in the ring.

• D. Greenwald, A. Caldwell
  MPI-P, München
• Y. Bao
  IHEP Beijing, Beijing

Simulations of frictional cooling for a muon collider front end scheme show that it is a viable technique for quickly producing colliding beams. The Frictional Cooling Demonstration experiment at the Max Planck Institute for Physics, Munich, aims to demonstrate the working principle of frictional cooling on protons using a 10-cm-long cooling cell. The experiment is nearing the final data taking stages. The status of the experiment is presented along with recent data. Simulation of the experiment setup is also presented.

• D. Greenwald, A. Caldwell
  MPI-P, München
• Y. Bao
  IHEP Beijing, Beijing

Muon colliders would open new frontiers of investigation in high energy particle physics, allowing precision measurements to be made at the TeV energy frontier. One of the greatest challenges to constructing a muon collider is the cooling of a beam of muons on a timescale comparable to the lifetime of the muon. Frictional cooling holds promise for use in a muon collider scheme. By balancing energy loss to a gas with energy gain from an electric field, a beam of muons is brought to an equilibrium energy in 100s of nanoseconds. A frictional cooling scheme for producing high-luminosity beams for a muon collider is presented.

• B.J. Holzer, S. Bettoni, O.S. Brüning, S. Russenschuck
  CERN, Geneva
• R. Appleby
  UMAN, Manchester
• J.B. Dainton, L.N.S. Thompson
  Cockcroft Institute, Warrington, Cheshire
• M. Klein
  The University of Liverpool, Liverpool
• A. Kling, B. Nagorny, U. Schneekloth
  DESY, Hamburg
• P. Kostka
  DESY Zeuthen, Zeuthen
• A. Polini
  INFN-Bologna, Bologna

The LHeC aims at colliding hadron-lepton beams with center of mass energies in the TeV scale. For this purpose the existing LHC storage ring is extended by a high energy electron accelerator in the energy range of 60 to 140 GeV. The electron beam will be accelerated and stored in a LEP like storage ring in the LHC tunnel. In this paper we present the layout of the interaction region which has to deliver at the same time well matched beam optics and an efficient separation of the electron and proton beams. In general the large momentum difference of the two colliding beams provides a very elegant way to solve this problem: A focusing scheme that leads to the required beam sizes of the electrons and protons is combined with an early but gentle beam separation to avoid parasitic beam encounters and still keep the synchrotron radiation level in the IR within reasonable limits. We present in this paper two versions of this concept: A high luminosity layout where the mini beta magnets are embedded into the detector design as well as an IR design that is optimised for maximum acceptance of the particle detector.

• Q. Wu, I. Ben-Zvi, X. Chang, J. Skarita
  BNL, Upton, Long Island, New York

The proposed electron ion collider, eRHIC, requires large average polarized electron current of 50mA, which is more than 20 times higher than the present experiment results of single polarization source, such as GaAs. To achieve the current requirement of eRHIC, we have designed the multi-cathode DC electron gun for injection. 24 GaAs cathodes will be prepared and emit electrons at the arranged pattern. Despite of ultra-high vacuum and precise timing, multi-cathode DC electron gun has high demand on the electric field symmetry, magnetic field shielding, and arcing prevention. In the paper, we present the 3D simulation results of the latest model for the multi-cathode DC electron gun. The results will give guidance to the actual design in the future.

• T. Baer, B. Araujo Meleiro, T.B. Bogey, J. Wenninger
  CERN, Geneva
• T. Baer
  DESY, Hamburg

The Super Proton Synchrotron (SPS) at CERN with a peak energy of 450GeV is at the top of the LHC preaccelerator-complex. Apart from the LHC, SPS is with Tevatron the accelerator with the largest stored beam energy of up to 2.5MJ. The SPS has a known vulnerability to fast equipment failures that led to an uncontrolled loss of a high intensity beam in 2008, which resulted in major damage of a main dipole. The beam loss was caused by a fast tune decrease towards an integer resonance. Simulations and distinct experimental studies provide clear understanding of the beam dynamics at different SPS tune resonances. Diverging closed orbit oscillations, dispersion explosion and increased beta-beating are the driving effects that lead to a complete beam loss in as little as 3 turns (70μs). Dedicated experiments of fast failures of the main power converters reveal that the current interlock systems are much too slow for an adequate machine protection. To counteract the vulnerability of the SPS, current research focuses on a new fast position interlock system which is planned to become operational in 2010.

• F. Zimmermann, S. Bettoni, O.S. Brüning, B.J. Holzer, S. Russenschuck, D. Schulte, R. Tomás
  CERN, Geneva
• H. Aksakal
  N.U, Nigde
• R. Appleby
  UMAN, Manchester
• S. Chattopadhyay, M. Korostelev
  Cockcroft Institute, Warrington, Cheshire
• A.K. Çiftçi, R. Çiftçi, K. Zengin
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• J.B. Dainton, M. Klein
  The University of Liverpool, Liverpool
• E. Eroglu, I. Tapan
  UU, Bursa
• P. Kostka
  DESY Zeuthen, Zeuthen
• V. Litvinenko
  BNL, Upton, Long Island, New York
• E. Paoloni
  University of Pisa and INFN, Pisa
• A. Polini
  INFN-Bologna, Bologna
• U. Schneekloth
  DESY, Hamburg
• M.K. Sullivan
  SLAC, Menlo Park, California

In a linac-ring electron-proton collider based on the LHC ("LR-LHeC"), the final focusing quadrupoles for the electron beam can be installed far from the collision point, as far away as the proton final triplet (e.g. 23 m) if not further, thanks to the small electron-beam emittance. The inner free space could either be fully donated to the particle-physics detector, or accommodate "slim" dipole magnets providing head-on collisions of electron and proton bunches. We present example layouts for either scenario considering electron beam energies of 60 and 140 GeV, and we discuss the optics for both proton and electron beams, the implied minimum beam-pipe dimensions, possible design parameters of the innermost proton and electron magnets, the corresponding detector acceptance, the synchrotron radiation power and its possible shielding or deflection, constraints from long-range beam-beam interactions as well as from the LHC proton-proton collision points and from the rest of the LHC ring, the passage of the second proton beam, and the minimum beta* for the colliding protons.

• G. Franchetti
  GSI, Darmstadt
• F. Zimmermann
  CERN, Geneva

The presence of an electron cloud in an accelerator generates a number of interesting phenomena. In addition to electron-driven beam instabilities, the electron "pinch" occurring during a beam-bunch passage gives rise to a highly nonlinear force experienced by individual beam particles. A simple 1-dimensional model for the effect of the electron pinch on the beam reveals a surprisingly rich dynamics. We present the model and discuss simulation results.

• F. Zimmermann, O.S. Brüning, E. Ciapala, F. Haug, J.A. Osborne, D. Schulte, Y. Sun, R. Tomás
  CERN, Geneva
• C. Adolphsen
  SLAC, Menlo Park, California
• R. Calaga, V. Litvinenko
  BNL, Upton, Long Island, New York
• S. Chattopadhyay
  Cockcroft Institute, Warrington, Cheshire
• J.B. Dainton, M. Klein
  The University of Liverpool, Liverpool
• A.L. Eide
  LPNHE, Paris

We consider three different scenarios for the recirculating electron linear accelerator (RLA) of a linac-ring type electron-proton collider based on the LHC (LHeC): i) a basic version consisting of a 60 GeV pulsed, 1.5 km long linac, ii) a higher luminosity configuration with a 60 GeV 4 km long cw energy-recovery linac (ERL), and iii) a high energy option using a 140 GeV pulsed linac of 4 km active length. This paper describes the footprint, optics of linac and return arcs, emittance growth from chromaticity and synchrotron radiation, a set of parameters, and the performance reach for the three scenarios.

• Y. Hao, P. He, A.K. Jain, V. Litvinenko, G.J. Mahler, W. Meng, J.E. Tuozzolo
  BNL, Upton, Long Island, New York

In this paper we present the design and prototype measurement of small gap (5mm to 10 mm aperture) dipole and quadrupole for the future high energy ERL (Energy Recovery Linac). The small gap magnets have the potential of largely reducing the cost of the future electron-ion collider project, eRHIC, which requires a 10GeV to 30 GeV ERL with up to 6 energy recovery passes (3.8 km each pass). We also studied the sensitivity of the energy recovery pass and the alignment error in this small magnets structure and countermeasure methods.

• Y. Hao, V. Litvinenko, V. Ptitsyn
  BNL, Upton, Long Island, New York

Beam-beam effects in eRHIC have a number of unique features, which distinguish them from both hadron and lepton colliders. Due to beam-beam interaction, both electron and hadron beams would suffer quality degradation or beam loss from without proper treatments. Those features need novel study and dedicate countermeasures. We study the beam dynamics and resulting luminosity of the characteristics, including mismatch, disruption and pinch effects on electron beam, in additional to their consequences on the opposing beam as a wake field and other incoherent effects of hadron beam. We also carry out countermeasures to prevent beam quality degrade and coherent instability.

• Y. Hao, J. Kewisch, V. Litvinenko, E. Pozdeyev, V. Ptitsyn, D. Trbojevic, N. Tsoupas
  BNL, Upton, Long Island, New York

In this paper, we analyzed the linac optics design requirement for a multi-pass energy recovery linac (ERL) with one or more linacs. A set of general formula of constrains for the 2-D transverse matrix is derived to ensure design optics acceptance matching throughout the entire accelerating and decelerating process. Meanwhile, the rest free parameters can be adjusted for fulfilling other requirements or optimization purpose. As an example, we design the linac optics for the future MeRHIC (Medium Energy eRHIC) project and the optimization for enlarging the BBU threshold.

• A.K. Çiftçi, R. Çiftçi
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• F. Zimmermann
  CERN, Geneva

In a linac-ring electron-proton collider based on the LHC, before and after the collision point the electron beam can be deflected with weak dipole magnets positioned in front of the superconducting final quadrupole triplets of the 7-TeV proton beam. Significant synchrotron radiation may be produced when the electron beam, of energy 60-140 GeV, passes through these dipole magnets. As an alternative or complement to shielding, parts of the synchrotron radiation could be extracted together with the electron beam. We propose using mirrors with shallow grazing angle to deflect the synchrotron radiation away from the proton magnets. Various LHeC options are considered. Limitations and challenges of this approach are discussed.

• H. K. Sayed
  CASA, newport news
• S.A. Bogacz, P. Chevtsov
  JLAB, Newport News, Virginia

A unique design feature of a polarized Medium Energy Electron-Ion Collider (MEIC) based on CEBAF is its 'Figure-8' storage rings for both electrons and ions, which significantly simplifies beam polarization maintenance and manipulation.  While electron (positron) polarization is maintained vertical in arcs of the ring, a stable longitudinal spin at four collision points is achieved through solenoid based spin rotators and horizontal orbit bends. The proposed MEIC lattice was developed in order to preserve a very high polarization (more than 70%) of the electron beams injected from the CEBAF machine. The otherwise coupled beam trajectory due to solenoids used in the spin rotators was decoupled by design. Aspin matching technique needs to be implemented in order to enhance quantum self-polarization and minimize depolarization effects.

• H. K. Sayed
  CASA, newport news
• S.A. Bogacz, Y. Roblin
  JLAB, Newport News, Virginia

The proposed electron collider lattice exhibits low β- functions at the Interaction Point (IP) (βx∗100mm − βy∗ 20 mm) and rather large equilibrium momentum spread of the collider ring (δp/p = 0.00158). Both features make the chromatic corrections of paramount importance. Here the chromatic effects of the final focus quadruples are cor- rected both locally and globally. Local correction features symmetric sextupole families around the IP, the betatron phase advances from the IP to the sextupoles are chosen to eliminate the second order chromatic aberration. Global interleaved families of sextupoles are placed in the figure-8 arc sections, and non-interleaved families at straight sec- tion making use of the freely propagated dispersion wave from the arcs. This strategy minimizes the required sex- tupole strength and eventually leads to larger dynamic aper- ture of the collider. The resulting spherical aberrations induced by the sextupoles are mitigated by design; the straight and arc sections optics features an inverse identity transformation between sextupoles in each pair.

• C. Montag, W. Fischer
  BNL, Upton, Long Island, New York

The luminosity of a ring-ring electron-ion collider is limited by the beam-beam effect on the electrons. Simulation studies have shown that for short ion bunches this limit can be significantly increased by head-on beam-beam compensation via an electron lens. However, due to the large beam-beam parameter experienced by the electrons, together with an ion bunch length comparable to the beta-function at the IP, electrons perform a sizeable fraction of a betatron oscillation period inside both the long ion bunches and the electron lens. Recent results of our simulation studies of this effect will be presented.

• C. Montag
  BNL, Upton, Long Island, New York
• A. Jankowiak
  IKP, Mainz
• A. Lehrach
  FZJ, Jülich

To facilitate studies of collisions between polarized electron and protons at √{s} = 14 GeV constructing an electron-nucleon collider at the FAIR facility has been proposed. This machine would collide the stored 15 GeV polarized proton beam in the HESR with a polarized 3.3 GeV electron beam circulating in an additional storage ring. We describe the interaction region design of this facility, which utilizes the PANDA detector.

• V. Ptitsyn, M. Blaskiewicz, W. Fischer, R.C. Lee, S.Y. Zhang
  BNL, Upton, Long Island, New York

A fast transition instability presents a limiting factor for ion beam intensity in RHIC. Several pieces of evidence show that electron clouds play an important role in establishing the threshold of this instability. In RHIC Runs 7 and 8 dedicated measurements of the instability, using different beam instrumentation tools (Button BPM, Wall Current Monitor, transition monitors) were done in order to observe the instability development over hundreds turns. The papers presents and discusses the results of those measurements in time and frequency domains.

• M. Kikuchi, T. Abe, K. Egawa, H. Fukuma, K. Furukawa, N. Iida, H. Ikeda, T. Kamitani, K. Kanazawa, K. Ohmi, K. Oide, K. Shibata, M. Tawada, M. Tobiyama, D.M. Zhou
  KEK, Ibaraki

Super-KEKB, an upgrade plan of the present KEKB collider, has recently changed its scheme from 'high current' option to 'nano-beam' scheme. In the latter the current is relatively low(4A/2.3A for LER/HER ring) compared to that of the high-current option(9.4A/4.1A), while the vertical beam size is squeezed to 60 nm at the interaction point to get the high luminosity. The emittance of the injected beam should be low and, since the Tousheck lifetime is very short(600 sec), the intensity of the positron beam is as high as 8 nC/pulse. For the electron beam a low-emittance high-intensity RF gun is adopted. For the positron beam a damping ring has been proposed. The design of the damping ring has been performed for the high-current option*. In this paper an updated design for the nano-beam scheme is presented.

* Nucl. Instr. Meth. A 556 (2006) 13-19

• D. Ji, Y. Jiao, Q. Qin, Y. Wei
  IHEP Beijing, Beijing

Optics correction is an important issue at BEPCII. Due to the errors in all kinds of components of a storage ring, the real optics of a storage ring is different from the design one. This paper introduces some developments of optics calibration at BEPCII storage ring. We use the method that fit the measured response matrix to the model response matrix to get the fudge factor of the quadrupole field and the sextupole field. On the other hand, in considering fringing fields of quadrupole magnet and interaction of quadrupole magnet iron core and sextupole magnet iron core, the model is calibrated.

• L. Arnaudon, P. Baudrenghien, O. Brunner, A.C. Butterworth
  CERN, Geneva

The LHC ACS RF system is composed of 16 superconducting cavities, eight per ring, housed in a total of four cryomodules each containing four cavities. Each cavity is powered by a 300 kW klystron. The ACS RF power control system is based on industrial Programmable Logic Controllers (PLCs), but with additional fast RF interlock protection systems. Operational performance and reliability are described. A full set of user interfaces, both for experts and operators has been developed, with user feedback and maintenance issues as key points. Operational experience with the full RF chain, including the low level system, the beam control, the synchronisation system and optical fibres distribution is presented. Last but not least overall performance and reliability based on experience with beam are reviewed and perspectives for future improvement outlined.

• F. Poirier, I. Chaikovska, O. Dadoun, P. Lepercq, R. Roux, A. Variola
  LAL, Orsay
• R. Boni, S. Guiducci, M.A. Preger, P. Raimondi
  INFN/LNF, Frascati (Roma)
• R. Chehab
  IN2P3 IPNL, Villeurbanne

Providing a high quality and sufficient high current positron beam for the ultra high luminosity B-factory SuperB is a major goal. In this paper a proposition for positrons production and capture scheme based on low energy electrons up to1 GeV is presented. For this technique, several types of flux concentrator used to capture the positrons are being studied. The following accelerating section bringing the positrons up to 280 MeV and the total yield for L-band and S-band type accelerators are given. Also the result of the benchmark between ASTRA and a LAL code based on Geant4 toolkit simulation is discussed.

• H. Fujimori, Z. Igarashi, Y. Irie, Y. Sato, M.J. Shirakata, I. Sugai, A. Takagi, Y. Takeda
  KEK, Ibaraki

The carbon stripping foil is the key element for the high-intensity proton accelerator. At KEK, the foil test system using the 650keV H^- Cockcroft-Walton accelerator is in operation, which can simulate the energy depositions to the foil with the same amount in the J-PARC. In order to quantatively observe the foil degradations (such as foil thinning, pin-hole production) during irradiation, online energy and particle analyzing system is under construction. This report outlines the design detail of the analyzing system including the detectors.

• A.V. Bondarenko, S.V. Miginsky, N. Vinokurov
  BINP SB RAS, Novosibirsk

A new beam extraction scheme from a synchrotron is put forward. The main difference from other schemes of extraction is the use of a magnetic shields instead of a septum. Magnetic shields are located in the central dipole magnets of a pulsed chicane. The magnetic shield is a multi-layer copper-iron tube. Numerical simulations and experimental results for the magnetic shield are presented. A good accordance between them has shown. The advantages of the new scheme are easy technical implementation and compactness. The area of application is extraction from a synchrotron. The proposed scheme will be used in a new synchrotron radiation source in Novosibirsk.

• J.A. Uythoven, E. Carlier, L. Ducimetière, B. Goddard, V. Kain, N. Magnin
  CERN, Geneva

The LHC beam dump system was commissioned with beam in 2009. This paper describes the operational experience with the kicker systems and the tests and measurements to qualify them for operation. The kicker performance was characterized with beam by measurements of the kicker waveforms using bunches extracted at different times along the kicker sweep. The kicker performance was also continuously monitored for each pulse with measurement and analysis of each kick pulse, allowing diagnostic of errors and of long-term drifts. The results are described and compared to the expectations.

• T. Kramer
  EBG MedAustron, Wr. Neustadt
• W. Bartmann, C. Bracco, B. Goddard, M. Meddahi
  CERN, Geneva

The LHC beam dump system has to safely dispose all beams in a wide energy range of 450 GeV to 7 TeV. A 3 μs abort gap in the beam structure for the switch-on of the extraction kicker field ideally allows a loss free extraction under normal operating conditions. However, a low number of asynchronous beam aborts is to be expected from reliability calculations and from the first year's operational experience with the beam dump kickers. For such cases, MAD-X simulations including all optics and alignment errors have been performed to determine loss patterns around the LHC as a function of the position of the main protection elements in interaction region six. Special attention was paid to the beam load on the tungsten collimators which protect the triplets in the LHC experimental insertions, and the tracking results compared with semi-analytical numerical estimates. The simulations are also compared to the results of beam commissioning of these protection devices.

• B. Goddard, V. Kain, M. Meddahi
  CERN, Geneva

The beam profile screens in the long SPS to LHC transfer lines were used to measure with high precision the emittance growth arising from scattering. The effective thickness of the scatterer could be varied by adding thick Al2O3 fluorescent screens, with the emittance measurement made using very thin Ti OTR screens. The technique allows the intrinsic variation in the emittance from the injector chain to be factored out of the measurement, and was applied to Pb⁸²⁺ and protons, both with 450 GeV rigidity. The results are presented and the possible applications to the accurate benchmarking of nuclear interaction codes discussed.

• V. Kain, K. Fuchsberger, B. Goddard, D. Karadeniz, M. Meddahi, J. Wenninger
  CERN, Geneva

The tilt mismatch between the LHC and its transfer lines arises from the use of combined horizontal and vertical bends. The mismatch gives rise to several subtle optical effects, including a coupling at injection into the LHC which depends on the phase of the oscillation amplitude at the injection point. This coupling was observed for the first time in 2008, and in 2009 dedicated measurements were made. The results are described and compared with the expectations, and the operational implications detailed.

• B. Goddard, V. Baggiolini, W. Bartmann, C. Bracco, L.N. Drosdal, E.B. Holzer, V. Kain, D. Khasbulatov, N. Magnin, M. Meddahi, A. Nordt, M. Sapinski
  CERN, Geneva
• M. Vogt
  DESY, Hamburg

The quality of the injection into the LHC is monitored by a dedicated software system which acquires and analyses the pulse waveforms from the injection kickers, and measures key beam parameters and compares them with the nominal ones. The beam losses at injection are monitored on many critical devices in the injection regions, together with the longitudinal filling pattern and maximum trajectory offset on the first 100 turns. The paper describes the injection quality check system and the results from LHC beam commissioning, in particular the beam losses measured during injection at the various aperture limits. The results are extrapolated to full intensity and the consequences are discussed.

• W. Bartmann, R.W. Assmann, C. Bracco, B. Dehning, B. Goddard, E.B. Holzer, V. Kain, M. Meddahi, A. Nordt, S. Redaelli, A. Rossi, M. Sapinski, D. Wollmann
  CERN, Geneva

The movable LHC injection protection devices in the SPS to LHC transfer lines and downstream of the injection kicker in the LHC were commissioned with low-intensity beam. The different beam-based alignment measurements used to determine the beam centre and size are described, together with the results of measurements of the transverse beam distribution at large amplitude. The system was set up with beam to its nominal settings and the protection level against various failures was determined by measuring the transmission and transverse distribution into the LHC as a function of oscillation amplitude. Beam losses levels for regular operation were also extrapolated. The results are compared with the expected device settings and protection level, and the implications for LHC operation discussed.

• B. Goddard, W. Bartmann, C. Bracco, V. Kain, M. Meddahi, V. Mertens, J.A. Uythoven
  CERN, Geneva

The commissioning of the beam transfer systems for LHC included detailed aperture measurements in the injection regions and for the beam dump systems. The measurements, mainly single pass, were made using systematic scans of different oscillation phases and amplitudes, and the results compared with the expectations from the physical aperture model of the LHC. In this paper the measurements and results are presented and compared with the specified apertures in these critical areas.

• M. Meddahi, S.D. Fartoukh, K. Fuchsberger, B. Goddard, W. Herr, V. Kain, V. Mertens, J. Wenninger
  CERN, Geneva
• D. Kaltchev
  TRIUMF, Vancouver

In 2008, the SPS-to-LHC transfer line operation allowed for the first time to perform beam measurements in the last part of the lines and into the LHC. Beam parameters were measured and compared with expectation. Discrepancies were observed in the dispersion matching into the LHC, and also in the vertical phase advance along the line. In 2009, extensive theoretical and simulation work was performed in order to understand the possible sources of these discrepancies. This allowed establishing an updated model of the beam line, taking into account the importance of the full magnetic model, the limited dipole corrector strengths and the precise alignment of beam elements. During 2009, beam time was allocated in order to perform further measurements, checking and refining the optical model of the transfer line and LHC injection region and validating the different assumptions. Results of the 2009 optics measurements and comparison with the beam specification and model are presented.

• A. Bertarelli, A. Dallocchio, L. Gentini, N. Mariani, R. Perret, M.A. Timmins
  CERN, Geneva

Phase II collimators will complement the existing system to improve the expected high RF impedance and limited efficiency of Phase I jaws. An international collaborative effort has been launched to identify novel advanced materials responding to the very challenging requirements of the new collimators. Complex numerical calculations simulating extreme conditions and experimental tests are in progress. In parallel, an innovative modular design concept of the jaw assembly is being developed to allow fitting in alternative materials, minimizing the thermally induced deformations, withstanding accidents and tolerate high radiation doses. Phase II jaw assembly is made up of a molybdenum back-stiffener ensuring high geometrical stability and a modular jaw split in threes sectors. Each sector is equipped with a high-efficiency independent cooling circuit. Beam position monitors (BPM) are embedded in the jaws to accelerate setup time and improve beam monitoring. An adjustment system will permit to fine-tune the jaw flatness just before commissioning the system. A full scale collimator prototype is being manufactured by CERN workshops to validate each feature of the new design.

• Y.I. Levinsen, R. Appleby, H. Burkhardt
  CERN, Geneva

We report on first observations and detailed simulations of beam gas rates in the LHC. For the simulations, a comprehensive tool has been set up to simulate in a few hours the expected beam gas losses when pressure maps, collimator settings, and/or beam optics changes. The simulation includes both elastic and inelastic scattering, with subsequent multiturn tracking of proton residues. This provides amongst others a more realistic collimator loss distributions from elastic interactions than what was previously available.

• Y.I. Levinsen, R. Appleby, H. Burkhardt, S.M. White
  CERN, Geneva

Background and loss rates vary when beams are brought into collisions in the LHC and when the beam separation is varied during luminosity scans. We report on the first observations in the early LHC operation. The observed effects are analyzed and compared with models and simulation.

• R. Losito
  CERN, Geneva

The UA9 experiment was installed in the CERN-SPS in March '09 in view of investigating crystal assisted collimation in coasting mode. Inside a vacuum vessel, two 2 mm long silicon crystals, bent by about 150 microradians are mounted on accurate goniometers, and a small 10mm long tungsten target is used to compare the effect of crystals with that of a standard scatterer. A moveable 60 cm long block of tungsten is located downstream at about 90 degrees phase advance to intercept the deflected beam. Scintillators, gas GEMs and beam loss monitors measure nuclear loss rates induced by the interaction of the halo beam in the crystal itself. A Roman pot is installed in the path of the deflected particles in between the crystal and the collimator, equipped with a Medipix detector to reconstruct the transverse spot of the impinging beam. Finally UA9 takes advantage of an LHC-collimator prototype installed close to the Roman pot to help in setting the beam conditions and to reveal in a destructive manner the deflected beam shape. This paper describes in details the hardware installed, and the procedures developed to set-up and detect the channeling conditions.

• D. Mirarchi, G. Cavoto
  INFN-Roma, Roma
• R. Losito, W. Scandale
  CERN, Geneva
• A.M. Taratin
  JINR, Dubna, Moscow Region

We present a detailed analysis of the beam loss data collected at the SPS during the 2009 machine developments devoted to test crystal collimation. Scintillator counters and Gas electron multiplier detectors were installed in special points to detect the effect of inelastic interaction of protons with the crystals in various orientation with respect to the beam. Clear correlations of the counting rates with the crystal positions and orientation were detected during the data-taking and were crucial to put the crystal in optimal channeling position. For one of the crystal the pattern of losses showed evidence of several planar and axial channeling conditions.

• G. Stancari, A.I. Drozhdin, G.F. Kuznetsov, V.D. Shiltsev, D.A. Still, A. Valishev, L.G. Vorobiev
  Fermilab, Batavia
• R.W. Assmann
  CERN, Geneva
• A.A. Kabantsev
  UCSD, La Jolla, California
• G. Stancari
  INFN-Ferrara, Ferrara

Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

• J.C. Smith, L. Keller, S.A. Lundgren, T.W. Markiewicz
  SLAC, Menlo Park, California

The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite secondary collimators with 30 high Z Phase II collimators. The Phase II collimators must be robust in various operating conditions and accident scenarios. This paper reports on the final construction and testing of the prototype collimator to be installed in the SPS (Super Proton Synchrotron) at CERN. Bench-top measurements have demonstrated the device is fully operational and has the mechanical and vacuum characteristics acceptable for installation in the SPS.

• J.C. Smith, L. Keller, S.A. Lundgren, T.W. Markiewicz, A. Young
  SLAC, Menlo Park, California

The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite secondary collimators with 30 high Z Phase II collimators. This paper reports on BPM and impedance considerations and measurements of the integrated BPMs in the prototype rotatable collimator to be installed in the Super Proton Synchrotron (SPS) at CERN. The BPMs are necessary to align the jaws with the beam. Without careful design the beam impedance can result in unacceptable heating of the chamber wall or beam instabilities. The impedance measurements involve utilizing both a single displaced wire and two wires excited in opposite phase to disentangle the driving and detuning transverse impedances. Trapped mode resonances and longitudinal impedance are to also be measured and compared with simulations. These measurements, when completed, will demonstrate the device is fully operational and has the impedance characteristics and BPM performance acceptable for installation in the SPS.

• L. Keller, T.W. Markiewicz, J.C. Smith
  SLAC, Menlo Park, California
• R.W. Assmann, C. Bracco
  CERN, Geneva
• Th. Weiler
  KIT, Karlsruhe

A current issue with the LHC collimation system is single-diffractive, off-energy protons from the primary collimators that pass completely through the secondary collimation system and are absorbed immediately downbeam in the cold magnets of the dispersion suppression section. Simulations suggest that the high impact rate could result in quenching of these magnets. We have studied replacing the 60 cm primary graphite collimators, which remove halo mainly by inelastic strong interactions, with 5.25 mm tungsten, which remove halo mainly by multiple coulomb scattering and thereby reduce the rate of single-diffractive interactions which cause losses in the dispersion suppressor.