EPAC 2004 - List of Keywords

A B C D E F G H I K L M N O P Q R S T U V W

interaction-region

Paper	Title	Other Keywords	Page
MOPLT004	Control of the LHC 400 MHz RF System (ACS)	klystron, controls, monitoring, diagnostics	533
	L. Arnaudon, M.D. Disdier, P.M. Maesen, M.P. Prax CERN, Geneva
	The LHC ACS RF system is composed of 16 superconducting cavities, eight per ring. Each ring has two cryomodules, each containing four cavities. Each cavity is powered by a 300 kW klystron. The klystrons are grouped in fours, the klystrons in each group sharing a common 58 kV power converter and HV equipment bunker. The ACS RF control system is based on modern industrial programmable controllers (PLCs). A new fast interlock and alarm system with inbuilt diagnostics has been developed. Extensive use of the FIPIO Fieldbus drastically decreases the cabling complexity and brings improved signal quality, increased reliability and easier maintenance. Features of the implementation, such as system layout, communication and the high level software interface are described. Operational facilities such as the automatic switch on procedure are described, as well as the necessary specialist tools and interfaces. A complete RF chain,including high voltage, cryomodule and klystron is presently being assembled in order to check, as far as possible, all aspects of RF system operation before LHC installation. The experience gained so far in this test chain with the new control system is presented

MOPLT045	Vacuum Induced Backgrounds in the New HERA Interaction Regions	proton, background, vacuum, radiation	647
	M. Seidel, M.G. Hoffmann DESY, Hamburg
	After the rebuild of the HERA interaction regions the experimental detectors were limited by beam induced backgrounds. Four types of background mechanisms were observed and identified - proton gas scattering, lepton gas scattering, synchrotron radiation and proton beam-halo losses. With some refined beam steering methods it was possible to tune the synchrotron radiation background to acceptable limits. The remaining most important effect was the scattering of the beam particles, mostly the protons, at the residual gas. In this contribution we describe our systematic attempts to investigate the complex behavior of the beam gas background and the measures taken to improve the situation. This includes dynamic pressure profile simulations and measurements, experimental determination of the background sensitivity profile along the beamline, the pressure development with current and time, and residual gas analysis. The background conditions were finally improved due to long term conditioning with beam, modifications of internal masks which were heated by higher order mode losses and moderate improvements of the pumping speed at strategic locations.

MOPLT078	The Coupling Compensation and Measurement in the Interaction Region of BEPCII	coupling, quadrupole, simulation, luminosity	728
	C.H. Yu, G. Xu IHEP Beijing, Beijing
	The detector solenoid field in the BEPCII interaction region will be compensated by 6 anti-solenoids, which are located nearby the interaction point. The coupling compensation scheme and the method to tune the x-y coupling at the interaction point will be introduced in detail.

MOPLT141	IR Upgrade Plans for the PEP-II B-Factory	luminosity, beam-beam-effects, dipole, permanent-magnet	869
	M.K. Sullivan, S. Ecklund, N. Kurita, A. Ringwall, J. Seeman, U. Wienands SLAC, Menlo Park, California M.E. Biagini INFN/LNF, Frascati (Roma)
	PEP-II, the SLAC, LBNL, LLNL B-factory has achieved a peak luminosity of over 7e33, more than twice the design luminosity, and plans to obtain a luminosity of over 1·10³⁴ in the next year. In order to push the luminosity performance of PEP-II to even higher levels an upgrade to the interaction region is being designed. In the present design, the interaction point is a head-on collision with two strong horizontal dipole magnets (B1) located between 20-70 cm from the IP that bring the beams together and separate the beams after the collision. The first parasitic crossing (PC) is at 63 cm from the IP in the present by2 bunch spacing. The B1 magnets supply all of the beam separation under the present design. Future improvements to PEP-II performance include lowering the beta y * values of both rings. This will increase the beta y value at the PCs which increases the beam-beam effect at these non-colliding crossings. Introducing a horizontal crossing angle at the IP quickly increases the beam separation at the PCs but recent beam-beam studies indicate a significant luminosity reduction occurs when a crossing angle is introduced at the IP. We will discuss these issues and describe the present interaction region upgrade design.

MOPLT144	Design for a 10³⁶ Super-B-factory at PEP-II	luminosity, factory, collider, injection	878
	J. Seeman, Y. Cai, F.-J. Decker, S. Ecklund, A.S. Fisher, J.D. Fox, S.A. Heifets, A. Novokhatski, M.K. Sullivan, D. Teytelman, U. Wienands SLAC, Menlo Park, California
	Design studies are underway to arrive at a complete parameter set for a very high luminosity e⁺e^- Super B-Factory (SBF) in the luminosity range approaching 10³⁶/cm²/s. The design is based on a collider in the PEP-II tunnel but with an upgraded RF system (higher frequency), magnets, vacuum system, and interaction region. The accelerator physics issues associated with this design are reviewed as well as the site and power constraints. Near term future studies will be discussed.

MOPLT179	Beam Scrubbing for RHIC Polarized Proton Opearation	electron, proton, injection, monitoring	947
	S.Y. Zhang, W. Fischer, H. Huang, T. Roser BNL, Upton, Long Island, New York
	One of the intensity limiting factor of RHIC polarized proton beam is the electron cloud induced pressure rise. During the 2003 polarized proton run, a beam scrubbing study was performed. Actual beam scrubbing time was much less than the planned 2 hours. However, a non-trivial beam scrubbing effect was observed not only in the locations with highest pressure rise, but also in most of the single beam straight sections. This not only confirmed that beam scrubbing is indeed a countermeasure to the electron cloud, but also showed the feasibility of applying beam scrubbing in RHIC proton beam operation to allow for higher beam intensities. In this article, the results will be reported.

TUXLH02	HERA Performance Upgrade: Achievements and Plans for the Future	proton, lepton, luminosity, resonance	93
	M.G. Minty DESY, Hamburg
	Having surpassed the design luminosity of 1.5 x 10³¹/cm²s already in 1997, an ambitious upgrade of the HERA proton-lepton collider was undertaken in 2000/2001 to provide both higher luminosity and longitudinally polarized lepton beams in the colliding beam experiments, H1 and ZEUS, and for the internal gas target experiment, HERMES. Routine operation following the upgrade has commenced. Initially experimental backgrounds limited the total beam currents so the number of colliding bunches was reduced while maintaining high single-bunch beam currents. With nominal, pre-upgrade, bunch currents the measured specific luminosity is 2.5 times higher than before, however about 15% smaller than design. Following modifications to alleviate the high backgrounds in 2003, HERA is now again operating with the design number of bunches and the total beam currents are being steadily increased. With only 40% of the total design current, peak luminosities of 2.5 x 10³¹/cm²s have been demonstrated with a longitudinal polarization of >40%. In this presentation the experiences from the upgrade commissioning will be reviewed. Plans for improvement and pronections for the future will be described.
	Video of talk
	Transparencies

TUPLT035	Online Calculation of the Beam Trajectory in the HERA Interaction Regions	quadrupole, alignment, proton, synchrotron	1222
	F. Brinker DESY, Hamburg
	During the HERA luminosity upgrade the new super conducting mini beta quadrupoles have been placed inside the experiments for final focussing and separation of the lepton and proton beams. The synchrotron radiation of up to 12 kW produced in these magnets passes through the detector and is absorbed behind the experiments. In order to avoid background events from synchrotron radiation it is a mandatory to adjust precisely the beam trajectory before and inside the detector. A procedure has been developed to calculate the trajectory in the interaction regions. With a beam-based alignment the offsets of the beam with respect to the quadrupoles is measured. From this measurement the offsets of the quadrupoles and of the beam position monitors are fitted. With the knowledge of these offsets the trajectory of the beam is calculated with high precision. The display of the trajectory is online available as an operational tool for beam steering and background optimization.

TUPLT153	Orbit Response Matrix Analysis Applied at PEP-II	lattice, coupling, sextupole, luminosity	1488
	C. Steier, A. Wolski LBNL/AFR, Berkeley, California S. Ecklund, J.A. Safranek, P. Tenenbaum, A. Terebilo, J.L. Turner, G. Yocky SLAC, Menlo Park, California
	Beam-based techniques to study lattice properties have proven to be a very powerful tool to optimize the performance of storage rings. The analysis of orbit response matrices has been used very successfully to measure and correct the gradient and skew gradient distribution in many accelerators. The first applications were mostly in synchrotron light sources, but the technique is also used increasingly at colliders. It allows determination of an accurately calibrated model of the coupled machine lattice, which then can be used to calculate the corrections necessary to improve coupling, dynamic aperture and ultimately luminosity. At PEP-II, the Matlab version of LOCO has been used to analyze coupled response matrices for both the LER and the HER. The large number of elements in PEP-II and the very complicated interaction region present unique challenges to the data analysis. The orbit response matrix analysis will be presented in detail, as well as results of lattice corrections based on the calibrated machine model.

TUPLT182	Measuring Local Gradient and Skew Quadrupole Errors in RHIC IRs	quadrupole, lattice, simulation, closed-orbit	1553
	J.F. Cardona UNAL, Bogota D.C S. Peggs, F.C. Pilat, V. Ptitsyn BNL, Upton, Long Island, New York
	The measurement of local linear errors at RHIC interaction regions using an "action and phase" analysis of difference orbits has already been presented []. This paper evaluates the accuracy of this technique using difference orbits that were taken when known gradient errors and skew quadrupole errors were intentionally introduced. It also presents action and phase analysis of simulated orbits when controlled errors are intentionally placed in a RHIC simulation model. J. Cardona, S. Peggs, T. Satogata, F. Pilat and V. Ptitsyn,"Determination of Linear and Non Linear Components in RHIC Interaction Regions from difference Orbit Measurements", EPAC 2002, Paris, 2002, p.311-313.

WEPKF073	2nd Generation LHC IR Quadrupoles Based on Nb3Sn Racetrack Coils	quadrupole, luminosity, target, alignment	1774
	V. Kashikhin, J. Strait, A.V. Zlobin Fermilab, Batavia, Illinois
	After the LHC operates for several years at nominal parameters, it will be necessary to upgrade it for higher luminosity. Replacing the baseline NbTi low-beta quadrupoles with a higher performance magnets based on advanced superconducting materials and magnet technologies is one of the most straightforward ways in this direction. Preliminary studies show that high-performance Nb3Sn strands to be available within the next few years allow increasing the quadrupole aperture up to 110 mm using a 4-layer shell-type coil and providing the same 200 T/m field gradient with 20% margin as the baseline magnets. It will allow reduction of b* by a factor of 3. An alternative approach to the quadrupole design is based on simple flat racetrack coils. This paper discusses the possibilities and limitations of large-aperture racetrack quadrupole designs and compares them to the shell-type magnets.

WEPKF074	Magnetic Field Measurements of the LHC Inner Triplet Quadrupoles Produced at Fermilab	quadrupole, alignment, injection, dipole	1777
	G. Velev, R. Bossert, R. Carcagno, J. DiMarco, S. Feher, H. Glass, V. Kashikhin, J.S. Kerby, M. Lamm, T. Nicol, L. Nobrega, D. Orris, T. Page, T. Peterson, R. Rabehl, P. Schlabach, J. Strait, C. Sylvester, M. Tartaglia, J. Tompkins, A.V. Zlobin Fermilab, Batavia, Illinois
	Production of 18 superconducting low-beta quadrupoles (MQXB) for the LHC is well advanced. These 5.5 m long magnets are designed to operate at 1.9 K with a peak field gradient of 215 T/m in the 70 mm apertures. Two MQXB cold masses with a dipole orbit corrector between them form a single cryogenic unit (LQXB) which is the Q2 optical element of the final focus triplets in the LHC interaction regions. A program of magnetic field quality and alignment measurements of the cold masses are performed at room temperature during magnet fabrication and LQXB assembly as well as at superfluid helium temperature. Results of these measurements are summarized in this paper.

WEPLT007	Installation of the LHC Experimental Insertions	quadrupole, shielding, insertion, luminosity	1828
	S. Bartolome-Jimenez, G. Trinquart CERN, Geneva
	The installation of the LHC experimental insertions, and particularly the installation of the low-beta quadrupoles, raises many technical challenges due to the stringent alignment specifications and to the difficulty of access in very confined areas. The compact layout with many lattice elements, vacuum components, beam control instrumentations and the presence of shielding does not allow for any improvisation in the installation procedure. This paper reviews all the constraints that need to be taken into account when installing the experimental insertions. It describes the chronological sequence of installation and discusses the technical solutions that have been retained.

WEPLT148	Dynamical Map for Combined Function Magnets with Solenoid, Dipole and Quadrupole Fields	dipole, quadrupole, lattice, closed-orbit	2185
	A. Wolski, M. Venturini LBNL, Berkeley, California
	The interaction regions of colliders invariably include strong solenoid fields. Where quadrupoles and dipoles are embedded in the solenoid, the beam dynamics in the combined fields can be complicated to model using the traditional approach of interleaving slices of different fields. The complexity increases if the design trajectory is offset from the magnetic axis; this is the case, for example, in PEP-II. In this paper, we present maps for combined solenoid, dipole and quadrupole fields that provide a much simpler alternative to the traditional approach, and show that the deviation of the design trajectory from the magnetic axis can be handled in a straightforward manner. We illustrate the techniques presented by reference to the PEP-II interaction region.

WEPLT177	Analysis of Electron Cloud at RHIC	electron, proton, injection, simulation	2239
	U. Iriso, M. Blaskiewicz, P. Cameron, K.A. Drees, W. Fischer, H.-C. Hseuh, R. Lee, S. Peggs, L. Smart, D. Trbojevic, S.Y. Zhang BNL, Upton, Long Island, New York G. Rumolo GSI, Darmstadt
	Pressure rises with high intense beams are becoming the main luminosity limitation at RHIC. Observations during the latest runs show beam induced electron multipacting as one of the causes for these pressure rises. Experimental studies are carried out at RHIC using devoted instrumentation to understand the mechanism leading to electron clouds. Possible cures using NEG coated beam pipes and solenoids are experimentally tested. In the following, we report the experimental electron cloud data and analyzed the results using computer simulation codes.

WEPLT182	Non-linear Modeling of the RHIC Interaction Regions	multipole, quadrupole, dipole, lattice	2245
	R. Tomas, W. Fischer, A.K. Jain, Y. Luo, F.C. Pilat BNL, Upton, Long Island, New York
	For RHIC's collision lattices the dominant sources of transverse non-linearities are located in the interaction regions. The field quality is available for most of the magnets in the interaction regions from the magnetic measurements, or from extrapolations of these measurements. We discuss the implementation of these measurements on the MADX models of the Blue and the Yellow rings and their impact on beam stability.

THOBLH02	Ultrafast Compton Scattering X-Ray Source Development at LLNL	electron, laser, photon, scattering	270
	F.V. Hartemann, S. Anderson, C.P.J. Barty, S.M. Betts, R. Booth, J. Brown, K. Crane, R.R. Cross, D.N. Fittinghoff, D. Gibson, E.P. Hartouni, J. Kuba, G.P. Le Sage, D.R. Slaughter, P.T. Springer, A. Tremaine, A.J. Wootton LLNL, Livermore, California J. Rosenzweig UCLA, Los Angeles, California
	The LLNL PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) facility is now operating between 30 and 80 keV, and produces > 5 x 10⁶ photons per shot at 10 Hz. This important milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as NIF diagnostics, time-resolved material studies, and advanced biomedical imaging. Initial x-rays were captured with a CCD using a CsI scintillator; the photon energy was measured at approximately 70 keV, and the observed spectral and angular distributions found to agree very well with three-dimensional codes. The electron beam was focused to 30 um rms, at 54 MeV, with 250 pC of charge, a relative energy spread of 0.2%, and a normalized emittance of 10 mm.mrad. Optimization of the x-ray dose is currently underway, with the goal of reaching 10⁷ photons per shot and a peak brightness approaching 10¹⁷ photons/mm2/mrad2/s/0.1%bandwidth. High-Z K-edge radiographs have been demonstrated, as well as diffraction using highly-ordered pyrolytic graphite crystals. Nonlinear scattering experiments, using a tightly focused laser spot will also be discussed, as well as plans to develop a source capable of reaching 1% conversion efficiency from the electron beam kinetic energy into x-rays, and ultrafast diffraction experiments.
	Video of talk
	Transparencies

THPLT042	Automated Orbit Control for the HERA ep Collider	electron, luminosity, proton, optics	2574
	S.W. Herb, P.K. Bartkiewicz, F. Brinker, J.M. Maass DESY, Hamburg
	Successful operation of the HERA electron-proton collider requires maintaining stable orbits during the typically 12 hour luminosity runs, as well as during the fill and acceleration procedures. The primary sources of orbit errors for the electron ring are the interaction region magnets, whose support structures are integrated with the experimental detectors and susceptible to thermal and magnetic effects. The orbit correction algorithms are designed to correct these effects locally, while operating with somewhat reduced sensitivity on error sources in the rest of the ring. We describe the correction system and our operating experience.

THPLT184	An Online Longitudinal Vertex and Bunch Spectrum Monitor for RHIC	pick-up, emittance, luminosity, monitoring	2882
	J. Van Zeijts, R. Lee BNL, Upton, Long Island, New York
	The longitudinal bunch profile acquisition system at RHIC was recently upgraded to allow online measurements of the bunch spectrum, and collision vertex location and shape. The system allows monitoring the evolution of these properties along the ramp, at transition and rebucketing, and at store conditions. We describe some of the hardware and software changes, and show an application of the system in optimizing the cogging of the colliding beams.