DIPAC 2007 - List of Keywords (coupling)

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

coupling

Paper	Title	Other Keywords	Page
TUO1A02	Feedbacks on Tune and Chromaticity	feedback, controls, resonance, synchrotron	43
	R. J. Steinhagen CERN, Geneva
	Feedbacks on tune, coupling and chromaticity are becoming an integral part of safe and reliable accelerator operation. Tight tolerances on beam parameters typically constrain the allowed oscillation amplitudes to the micrometre range, leaving only a small margin for the transverse beam and momentum excitations required for tune and chromaticity measurements. This contribution presents an overview of these beam-based feedback systems, their architecture and design choices involved. It discusses performance limitations due to cross-constraints, non-linearities, the coupling between multiple nested loops, and the interdependence of beam parameters.
	Slides

TUPB16	Optimization of the Linear-cut Beam Position Monitors Based on Finite Element Methods	simulation, cryogenics, quadrupole, pick-up	96
	P. Kowina, W. Kaufmann, J. Schölles GSI, Darmstadt
	This contribution presents simulations of the Beam Position Monitors (BPMs) for the FAIR project that were performed using CST Studio Suite 2006B. The linear-cut BPMs based on a metal-coated ceramics were considered as the only solution that meets the required mechanical stability under cryogenic conditions. The essential BPM features like position sensitivity or linearity of position determination were compared for two geometries. In these geometries, in both cases based on elliptically shaped ceramic pipe, the vertical and horizontal electrode pairs were either mounted subsequently in series or were spirally shaped and combined alternatively within one unit. It is shown that optimization of BPM design increases position sensitivity by more than a factor of two. The frequency dependence of the position sensitivity and an offset of electrical center of BPM in respect to its geometrical center were analyzed in the bandwidth of 200 MHz. In a frequency range up to 100 MHz (i.e. typical for the BPM applications) calculated variations of the displacement sensitivity are smaller than 1%; the careful design of a guard ring configuration allows keeping the offset consistent with zero.

TUPC09	Design of the cavity BPM system for FERMI@elettra	dipole, linac, simulation, diagnostics	165
	P. Craievich, C. Bontoiu, M. Ferianis, G. Trovato ELETTRA, Basovizza, Trieste M. Poggi INFN/LNL, Legnaro, Padova V. V. Smaluk BINP SB RAS, Novosibirsk
	The cavity Beam Position Monitor (BPM) is a fundamental instrument for a seeded FEL, as FERMI@elettra. It allows the measurement of the bunch trajectory non-destructively, on a shot-by shot basis and with sub-micron resolution. The high resolution the cavity BPM is providing relies on the excitation of the dipole mode, originated when the bunch passes off axis in the cavity. Here we present the electromagnetic (EM) design and the cold test of the prototype BPM developed for the FERMI@elettra. The design adopted a C-band cavity with its dipole mode at fDIP=6.5GHz. The prototype is actually fitted with two cavities: one for the position measurement and one for the generation of the reference signal for the demodulator. Furthermore, the design of the prototype electronics for the acquisition and processing of the BPM signals is presented. The adopted scheme consists of a down converter from C-band to the intermediate frequency, followed by an IQ demodulator to generate the base-band signal, proportional to the transverse beam position. The performed simulation session is presented as well which we run before building the hardware for bench tests.

TUPC16	Ultimate Resolution of Soleil X-Ray Pinhole Camera	photon, radiation, synchrotron, synchrotron-radiation	180
	M.-A. Tordeux, L. Cassinari, O. V. Chubar, J.-C. Denard, D. Pédeau, B. Pottin SOLEIL, Gif-sur-Yvette
	During the commissioning of the SOLEIL Storage Ring, beam emittances have been measured with an X-ray pinhole camera system. The evolution of the system and its performances are presented here. As a result of the excellent alignment of the ring magnets, the vertical beam size is smaller than expected, that led us to an effort towards improving the initial resolution of the instrument. A high sensitivity CCD camera allows us to select the harder X-ray part of the radiation which is a key element for resolution improvement. Finally an evaluation of the ultimate pinhole resolution is made for SOLEIL.

TUPC23	Design of a Submicron Resolution Cavity BPM for the ILC Main Linac	dipole, linear-collider, vacuum, collider	192
	A. Lunin, G. Romanov, N. Solyak, M. Wendt Fermilab, Batavia, Illinois
	A high resolution Beam Position Monitor (BPM) is necessary for the beam-based alignment and feedback systems of the future international linear collider (ILC). We present the cavity BPM developed at Fermilab within ILC collaboration. This monitor will be operated at cryogenic temperature and rigidly attached to the quad magnet. The same cylindrical cavity is used to obtain the signals from both dipole and monopole modes excited by beam. Such a scheme makes the BPM more compact for placing it inside the magnet space and simplifying the signal processing. The dipole TM110 mode is utilized to measure pulse to pulse beam motion at a theoretical resolution of approximately 50 nm. In order to measure a single bunch trajectory within 300 ns timescale we use a resonant coupling to lower cavity Q-factor. The ceramic windows are brazed inside coupling slots for vacuum isolation and easy cavity cleaning. We will present a BPM detailed numerical study and analyze its tolerance requirements for submicron resolution.

WEPB12	Measurement of Bunch Lengthening Effects Using a Streak Camera with Reflective Optics	optics, impedance, vacuum, synchrotron	256
	T. Obina, T. Mitsuhashi KEK, Ibaraki
	For the precise measurement of the bunch length, the incident optics of a streak camera must be free from an optical path difference due to chromatic effects. We designed and installed a reflective optics for the streak camera, and measured the bunch length as a function of the beam current. In the KEK Photon Factory, almost one half of the vacuum components were replaced in 2005. We measured the bunch lengthening effects before and after the replacement. The threshold-current of the microwave instabilities showed the impedance of the storage ring was greatly improved. This paper describes the detail of measurement and the calculations of the impedance of vacuum components.

WEPB19	Digital Analysis of Beam Diagnostic Noise	diagnostics, proton, instrumentation, pick-up	271
	P.-A. Duperrex, G. G. Gamma, B. Keil, M. U. Müller PSI, Villigen
	Results will be presented of recently developed, VME-based electronic modules, a digital beam position monitor (dBPM) and a logarithmic current measurement electronics (VME-LogIV). The dBPM is based on digital receiver technology and processes the signals from 4 pick-up coils. Features of the dBPM are the direct frequency down-converting of the RF 2nd harmonic 10¹.26MHz) signals (no analogue LO), the remote control of the front end amplifier and the online measurement of individual channel overall gain using 10¹.31 MHz pilot signals. Various data rates for position measurements at up to 10 kHz are possible. The VME-LogIV can simultaneously measure up to 32 channels at an effective sampling frequency of 5 kHz for the multiple wire profile monitors, also called harps. Fluctuations up to a few kHz of the beam intensity and beam position can thus be analyzed in detail with both of these new systems. Fluctuations from different dBPMs can be compared using coherence spectra measurement. The origin of the VME-LogIV noise can be analyzed using power and coherence spectra, and compared to the noise of the ion source. The results of this analysis will be discussed.

WEPC02	Developments at Elettra of the Electronics for the Bunch-Arrival Monitor	controls, pick-up, monitoring, laser	310
	L. Pavlovič, T. Korošec, M. Vidmar Uni LJ, Ljubljana M. Ferianis, F. Rossi ELETTRA, Basovizza, Trieste K. E. Hacker, F. Löhl, H. Schlarb DESY, Hamburg
	Within the framework of the EUROFEL project, a task has been started in 2006 for a joint development of a Bunch Arrival Monitor (BAM), based on the original idea from DESY. ELETTRA is responsible for the development of the VME-controlled clock-delay board of the BAM system. A variable clock-delay circuit (a phase shifter) is required to adjust the acquisition sampling point of the pick-up-modulated optical pulses of the master-laser oscillator. Since the optical pulses have a repetition rate of 40.625MHz (54MHz in the future) and the acquisition sampling frequency is double of this value, the clock-delay module operates in the 80-120MHz frequency range. The clock timing jitter of the acquisition system greatly affects the measurements of the system: the output timing jitter from the clock-delay board should be less than 0.5ps-rms. Therefore, due to the very strict additive timing-jitter requirements, three phase shifter versions were designed, built and phase-noise evaluated. Low-pass-filter implementation achieved 563fs (at 283fs source jitter) of total-system timing jitter, integrated IQ multiplier 365fs (at 188fs of source) and passive IQ modulator 265fs (at 208fs of source).

WEPC08	Fiberoptics-Based Instrumentation for Storage Ring Beam Diagnostics	synchrotron, diagnostics, photon, synchrotron-radiation	325
	S. De Santis, J. M. Byrd LBNL, Berkeley, California Y. Yin Y. Y. Labs, Inc., Fremont, California
	We present the results of our experiments at the Advanced Light Source concerning the coupling of synchrotron radiation into optical fibers. Many beam diagnostic devices in today's synchrotron rings make use of the radiation emitted by the circulating particles. Such instruments are placed in close proximity of the accelerator, where in many instances they cannot be easily accessed for safety consideration, or at the end of a beamline, which, because of its cost, can only move the light port a few meters away from the ring. Our method, suitable for all those applications where the longitudinal properties of the beam are measured (i.e. bunch length, phase, etc.), allows placing the diagnostic instruments wherever is more convenient, up to several hundreds of meters away from the tunnel. This would make maintaining and replacing instruments, or switching between them, possible without any access to restricted areas. Additionally, one can use the vast array of optoelectronic devices, developed by the telecommunication industry, for signal analysis.

WEPC10	Tune, Coupling, and Chromaticity Measurement and Feedback During RHIC Run 7	feedback, injection, betatron, controls	331
	P. Cameron, J. Cupolo, W. C. Dawson, C. Degen, A. J. Della Penna, L. T. Hoff, Y. Luo, A. Marusic, R. Schroeder, C. Schultheiss, S. Tepikian BNL, Upton, Long Island, New York
	Tune feedback was first implemented in RHIC in 2002, as a specialist activity. The transition to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End[1]. Continuous measurement of all projections of the betatron eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration, resolving the problem of overall loop instabilites[2,3]. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum. Preliminary investigations of power line harmonics were presented earlier[4]. We report here on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to the LHC commissioning effort. [1] M. Gasior and R. Jones, DIPAC 2005, Lyon, p.312.[2] P. Cameron et. al., PRST-AB, Dec 2006. [3] R. Jones et. al., DIPAC 2005, Lyon, p.298.[4] P. Cameron et. al., DIPAC 2005, Lyon, p.33.

WEPC26	Transverse Bunch-by-Bunch Feedback for the VEPP-4M Electron-Positron Collider	feedback, kicker, betatron, impedance	367
	V. P. Cherepanov, E. N. Dementyev, E. B. Levichev, A. S. Medvedko, V. V. Smaluk, D. P. Sukhanov BINP SB RAS, Novosibirsk
	Transverse mode coupling instability (TMCI or fast head-tail) is the principal beam current limitation of the VEPP-4M electron-positron collider. For the high-energy physics experiments at the 5.5 GeV energy, the VEPP-4M bunch current should exceed much the TMCI threshold. To suppress transverse beam instabilities, a broadband bunch-by-bunch digital feedback system is developed. The feedback concept is described, the system layout and first beam measurements are presented.