resonance

Paper	Title	Other Keywords	Page
MOO3A03	First Vibrating Wire Monitor Measurements of a Hard X-ray Undulator Beam at the Advanced Photon Source	photon, radiation, vacuum, insertion	36
	G. Decker ANL, Argonne, Illinois S. G. Arutunian, M. R. Mailian YerPhI, Yerevan G. Rosenbaum UGA, Athens, Georgia
	The first hard x-ray flux measurements with a vibrating wire monitor (VWM) using the acoustic resonance frequencies of two vertically-offset horizontal stainless steel wires as temperature diagnostics were conducted at APS beamline 19-ID. Due to the high sensitivity of this technique, the studies were performed at extremely low power levels using radiation from a 3.3-cm-period permanent magnet hybrid undulator with a 5-mA electron beam at an energy of 7 GeV. The x-ray beam was filtered by transmission through 7 mm of beryllium placed in the photon beam path, assuring that only hard x-rays were detected. The particle beam was scanned through a range of 400 microradians using an asymmetric closed-orbit angle bump, producing two vertical photon beam profiles. The difference between processed wire signals provides a very sensitive measure of photon beam position. Details of the measurements will be given, along with a discussion of the limitations of the method and possible future research directions.
	Slides
TUO1A02	Feedbacks on Tune and Chromaticity	feedback, controls, coupling, 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
TUPC08	Quadrupole Transfer Function for Emittance Measurement	quadrupole, emittance, pick-up, kicker	162
	P. Cameron BNL, Upton, Long Island, New York M. Gasior CERN, Geneva A. Jansson, C.-Y. Tan Fermilab, Batavia, Illinois
	Historically the use of the quadrupole moment measurement has been impeded by the requirement for large dynamic range, as well as the sensitivity of the measurement to beam position. In this paper we investigate the use of the transfer function technique in combination with the sensitivity and 160dB revolution line rejection of the direct diode detection analog front end to open the possibility of a sensitive emittance diagnostic that may be implemented economically and without operational complication, quasi-parasitic to the operation of existing phase-locked loop tune measurement systems. Such a diagnostic would be particularly useful as an emittance monitor during acceleration ramp development in machines like RHIC and the LHC.
WEO2A02	Single Shot Longitudinal Bunch Profile Measurements by Temporally Resolved Electro-Optical Detection	electron, laser, diagnostics, linac	221
	P. J. Phillips, A. MacLeod UAD, Dundee G. Berden, A. F.G. van der Meer FOM Rijnhuizen, Nieuwegein W. A. Gillespie University of Dundee, Nethergate, Dundee, Scotland S. P. Jamison STFC/DL/ASTeC, Daresbury, Warrington, Cheshire E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen DESY, Hamburg
	For the high-gain operation of a SASE FEL, extremly short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment to probe the time structure of the electric field of single sub 200fs e-bunches. In this technique, the field-induced birefringence in an electro-optic crystal is encoded on a chirped ps laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single-shot cross correlation with a 30 fs laser pulse using a second-harmonic crystal (temporal decoding). In the temporal decoding measurements an electro-optic signal of 180 fs FWHM was observed, and is close to the limit due to the material properties of the particular electro-optic crystal used. The measured electro-optical signals are compared to bunch shapes simultaneously measured with a transversly deflecting cavity.
WEPB09	Mechanical Design of the Intensity Measurement Devices for the LHC	vacuum, impedance, alignment, shielding	253
	D. B. Belohrad, S. Longo, OP. Odier, S. Thoulet CERN, Geneva
	The intensity measurement for the LHC ring is provided by eight current transformers: 2 DC current transformers (DCCTs) and 2 fast transformers (FBCTs) per vacuum chamber. The measurement precision of 1uArms at averaging over 1s time interval for the DCCTs and ±109 charges in 25ns bunch measurements for the FBCTs is required. Such constraints call for low noise electronics and a compact magnetically shielded mechanical design. Due to ultra high vacuum requirements in the LHC the vacuum chambers are equipped with the non-evaporable getter (NEG) film. The NEG is activated by heating the vacuum chamber to 200°C and more. Such temperatures affect the structure of the magnetic materials, which form the base part of the intensity measurement devices, and degrade their performance. A cooling circuit is needed. Due to the mechanical constraints, the cooling circuit, as well as heating element must form an integral part of the design. The paper presents the solution of these problems and discusses the mechanical construction of the DCCTs and FBCTs currently being installed in the LHC.
WEPB21	Kicker Based Tune Measurement for DELTA	kicker, betatron, storage-ring, feedback	277
	P. Hartmann, J. Fürsch, T. Weis, K. Wille DELTA, Dortmund R. Wagner Bergische Universität Wuppertal, Wuppertal
	We have set up a tune measurement for the electron storage ring Delta based on broadband beam excitation with a kicker magnet and measurement of the relaxation betatron oscillations turn-by-turn. By averaging over several kicks the kick amplitude may be as low as 600 nrad in standard user runs at nominal current, leading to negligible beam distortion. Signal to noise ratios in excess of 10 are reliably achieved down to 200 uA beam current using a maximum kicker amplitude of 10 urad. A simple tune feedback algorithm compensates for tune shifts due to vacuum chamber movement and orbit movement in sextupoles.