• Z.A. Conway, M. Liepe
  CLASSE, Ithaca, New York

Funding: Work supported by NSF Grant PHY 0131508

This paper reports results of cold measurements characterizing the electro-mechanical properties of the Cornell ERL injector cryomodule, which houses five superconducting niobium elliptical 2-cell cavities developed for a high-current (100 mA) low-emittance electron beam. Each cavity is equipped with a blade tuner. The Cornell ERL blade tuner is a modified version of the INFN-Milano design, and incorporates 4 piezoelectric actuators and accelerometers enabling concurrent slow/fast cw RF frequency control and mechanical vibration measurements. Cavity microphonics and fast tuner electro-mechanical transfer functions for all of the cavities have been measured and show the feasibility of stable feedback control at microphonic noise frequencies below ~100 Hz.

• N. Simos, M. Fallier
  BNL, Upton, Long Island, New York

Vibration stability in third generation light sources such as the 3 GeV NSLS II under construction at BNL and which are aiming at high brightness and extremely small photon beam sizes is paramount. Movement of the magnetic elements of the accelerator lattice, and in particular when uncorrelated, will induce jitter in the beam and degrade the machine performance. The accelerator lattice response is coupled with the ring structure which in turn interacts with the site and the ground vibration field that characterizes it. Therefore, understanding this dynamic coupling between the accelerator ring structure and the site and the “filtering” effect of the interaction on both the amplitude and the spectral characteristics of the ground vibration is central towards establishing the response of the lattice. In this study, the site-ring dynamic interaction is evaluated based on the NSLS II design and site conditions using a state-of-the-art 3-D wave propagation and scattering analysis model. The study is augmented with an extensive array of measurements at the selected site as well as field studies at similar operating light source facilities.

• N. Simos, M. Fallier, T.F. Joos
  BNL, Upton, Long Island, New York

Cultural noise generated within or in the proximity of a light source facility aiming to achieve stability levels of just tens of nanometers in the electron beam and extremely small photon beams in special experimental lines could be a limiting factor towards achieving the performance goals. While operating systems within the facility are more readily identifiable as sources of vibration and cause of instabilities and they tend to be of deterministic nature so appropriate action can be taken to minimize their impact, moving-type loads such as traffic in the general vicinity or within the bounds of the accelerator facility are more of a stochastic nature and require a different approach in assessing its impact on the synchrotron facility. In this study the effect of such loads which poses both stochastic elements and a complex spectrum on the stability performance goals of the NSLS II synchrotron and its vibration-sensitive experimental lines is addressed prior to the construction of the facility. This is achieved through the synergy of a comprehensive numerical model and an array of recorded field data.

• N. Simos
  BNL, Upton, Long Island, New York

The extremely small photon beam dimensions of NSLS II impose challenging requirements on the e-beam orbital stability in the 6-D phase space. The electron beam orbit at the photon source locations must remain within a few hundred nanometer window for a wide frequency band. The beam orbit movement is coupled to the movement of the magnetic elements in the lattice which are itself coupled to the ring-building structure. While the vibration exciting the ring structure consists of deterministic and stochastic noise, it is the high frequency random, uncorrelated part that has the largest impact on the residual beam orbit movement as it is most difficult to control by fast orbit feedback. In this study, an analytical model is employed to quantify lattice displacement and beam orbit jitter for the expected conditions of NSLS II. The dynamic interaction of the ring supporting the lattice with the stationary ground vibration is addressed using a 3-D model of wave-structure interaction. Cross transfer functions linking ground vibration with the ring and magnetic lattice for various stochastic parameters are deduced leading to a multi-degree of freedom cross-spectral density of the lattice.

• B.N. Kosciuk, R. Alforque, B. Bacha, P. Cameron, F. Lincoln, I. Pinayev, V. Ravindranath, S. Sharma, O. Singh
  BNL, Upton, Long Island, New York

The NSLS-II Light Source being built at Brookhaven National Laboratory is expected to provide submicron stability of the electron orbit in the storage ring in order to utilize fully the very small emittances and electron beam sizes. This requires high stability supports for BPM pick-up electrodes, located near insertion device source. Description of the efforts for development of supports including carbon tubes and invar rods is presented.

• K. Artoos, O. Capatina, C.G.R.L. Collette, M. Guinchard, C. Hauviller, F. Lackner, J. Pfingstner, H. Schmickler, M.V. Sylte
  CERN, Geneva
• B. Bolzon, L. Brunetti, G. Deleglise, N. Geffroy, A. Jeremie
  IN2P3-LAPP, Annecy-le-Vieux
• P.A. Coe, D. Urner
  OXFORDphysics, Oxford, Oxon
• M. Fontaine
  CEA, Gif-sur-Yvette

To reach the design luminosity of CLIC, the movements of the quadrupoles should be limited to the nanometer level in order to limit the beam size and emittance growth. Below 1 Hz, the movements of the main beam quadrupoles will be corrected by a beam-based feedback. But above 1 Hz, the quadrupoles should be mechanically stabilized. A collaboration effort is ongoing between several institutes to study the feasibility of the “nano-stabilization” of the CLIC quadrupoles. The study described in this paper covers the characterization of independent measuring techniques including optical methods to detect nanometer sized displacements and analyze the vibrations. Actuators and feedback algorithms for sub-nanometer movements of magnets with a mass of more than 400 kg are being developed and tested. Input is given to the design of the quadrupole magnets, the supports and alignment system in order to limit the amplification of the vibration sources at resonant frequencies. A full scale mock-up integrating all these features is presently under design. Finally, a series of experiments in accelerator environments should demonstrate the feasibility of the nanometer stabilization.

• K. Artoos, O. Capatina, C.G.R.L. Collette, M. Guinchard, C. Hauviller, M.V. Sylte
  CERN, Geneva
• B. Bolzon, A. Jeremie
  IN2P3-LAPP, Annecy-le-Vieux

The demanding nanometer transverse beam sizes and emittances in future linear accelerators results in stringent alignment and nanometer vibration stability requirements. For more than two decades, ground vibration measurements were made by different teams for feasibility studies of linear accelerators. Recent measurements were performed in the LHC tunnel and at different CERN sites on the surface. The devices to measure nanometer sized vibrations, the analysis techniques and the results are critically discussed and compared with former measurement campaigns. The implications of the measured integrated R.M.S. displacements and coherence length for the CLIC stabilization system are mentioned.

• V.D. Shiltsev, J.T. Volk
  Fermilab, Batavia
• S.R. Singatulin
  BINP SB RAS, Novosibirsk

Understanding slow and fast ground motion is important for the successful operation and design for present and future colliders. Since 2000 there have been several studies of ground motion at Fermilab. Several different types of hydro static water levels have been used to study slow ground motion (less than 1 hertz) seismometers have been used for fast (greater than 1 hertz) motions. Data have been taken at the surface and at locations 100 meters below the surface. Data and results on slow ground motion will be discussed in particular the effects of natural and cultural sources of motion. We also present estimates on the ATL-diffusion coefficients at various locations.

• B. Bolzon, A. Jeremie
  IN2P3-LAPP, Annecy-le-Vieux
• P. Bambade
  KEK, Ibaraki
• Y. Renier
  LAL, Orsay
• A. Seryi
  SLAC, Menlo Park, California

Funding: Work supported by the Agence Nationale de la Recherche of the French Ministry of Research (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027).

CLIC is one of the current projects of linear colliders. Achieving a vertical beam size of 1 nm at the Interaction Point (IP) with several nanometers of fast ground motion imposes an active stabilization of final doublet magnets (FD) at a tenth of nm above 4Hz. ATF2 is a test facility for linear colliders whose first aim is to have a vertical beam size of 37nm. Relative motion tolerance between FD and the IP is of 7nm above 0.1Hz. Because ground motion is coherent between these two elements, they were fixed to the floor so that they move in a coherent way. Investigations are going on to have in 2011 a useful active stabilization for ATF2 in order to use it as a CLIC prototype. Parameters of a 2D ground motion generator were fitted on measurements to reproduce spatial and temporal spectra, so it can be used for ATF2 simulations. Thus, we evaluated the ideal response function that an active stabilization FD system would need to have to improve on the present ATF2 system. Because ground motion coherence is lost with upstream magnets, we simulated the integrated vibrations at the IP to evaluate the usefulness of their stabilization. These results were validated with measurements.

• B. Bolzon, N. Geffroy, A. Jeremie
  IN2P3-LAPP, Annecy-le-Vieux
• Y. Kamiya
  ICEPP, Tokyo
• T. Kume
  KEK, Ibaraki
• M. Oroku, T. Yamanaka
  University of Tokyo, Tokyo

Funding: Work supported by the Agence Nationale de la Recherche of the French Ministry of Research (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027).

Future linear collider projects like ILC and CLIC will have beam sizes of a few nm. Vibration sources like ground motion can hamper the beam collisions. Relative jitter tolerance between the final focus magnets and the Interaction point (IP) is a fraction of the beam size. The ATF2 project proposes a test facility with a projected beam of 37nm. To measure the beam size with only 2% of error, vertical relative jitter tolerance (above 0.1Hz) between the final doublet magnets (FD) and the IP (with a Shintake beam Size Monitor: BSM) is of the order of 7nm while ground motion is of about 150nm. Thanks to determined adequate instrumentations, investigations were done to design supports for FD. Since ground motion measurements showed that this one is coherent up to 4m, more than the distance between FD and BSM, we chose a stiff support for FD fixed to the ground on its entire surface. Thus, FD and BSM should move in a coherent way. Vibration measurements show that relative motion between FD and BSM is only of 4.8nm and that flowing water in FD does not add any significant jitter. The FD support has been consequently validated on site at ATF2 to be within the vibration specifications.