Andrei Seryi

Present status and first results of the final focus beam line at the KEK Accelerator Test Facility

ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U. S. scientists. The present status and first results are described.

Proposal to Modify the Polarimeter Chicane in the ILC 14 mrad Extraction Line

A proposal is presented in this paper to modify the extraction line polarimeter chicane to allow the Compton backscattered electrons to be deflected further from the beam line, and to provide optics for the downstream GAMCAL detector.

Long term stability study at FNAL and SLAC using BINP developed hydrostatic level system

Long term ground stability is essential for achieving the performance goals of the Next Linear Collider. To characterize ground motion on relevant time scales, measurements have been performed at three geologically different locations using a hydrostatic level system developed specifically for these studies. Comparative results from the different sites are presented in this paper.

Hydrostatic level system for slow ground motion studies at Fermilab and SLAC

A series of new ground motion studies using an upgraded hydrostatic level system are planned at Fermilab and SLAC in collaboration with BINP. To better characterize both the spatial and temporal characteristics of slow ground motion, these studies will use large number of probes and will also be performed in several geologically different locations. The hydrostatic level system used in ongoing measurements near Fermilab [1] suffers from uncertainty of temperature fluctuation effects. This paper presents improvements to be incorporated into the upgraded hydrostatic level system, present status, and the plan for experimental studies.

Comparison of the TESLA, NLC and CLIC beam-collimation system performance

This report describes studies performed in the framework of the Collimation Task Force organized to support the work of the second International Linear Collider Technical Review Committee. The post-linac beam-collimation systems in the TESLA, JLC/NLC and CLIC linear-collider designs are compared using the same computer code under the same assumptions. Their performance is quantified in terms of beam-halo and synchrotron-radiation collimation efficiency. The performance of the current designs varies across projects, and does not always meet the original design goals. But these comparisons suggest that achieving the required performance in a future linear collider is feasible.

Effects of dynamic misalignments and feedback performance on luminosity stability in linear colliders

The performance of high energy linear colliders depends critically on the stability with which they can maintain the collisions of nanometer-size beams. Ground motion and vibration, among other effects, will produce dynamic misalignments which can offset the beams at the collision point. A system of train-to-train and intra-train beam-beam feedbacks, possibly combined with additional beam-independent active systems, is planned to compensate for these effects. Extensive simulation studies of ground motion and luminosity stabilization have been performed as part of the work of the International Linear Collider Technical Review Committee. This paper presents a comparison of the expected performance for TESLA, JLC/NLC and CLIC under various assumptions about feedbacks and the level of ground motion.

Simulation Studies of the NLC with Improved Ground Motion Models

The performance of various systems of the Next Linear Collider (NLC) have been studied in terms of ground motion using recently developed models. In particular, the performance of the beam delivery system is discussed. Plans to evaluate the operation of the main linac beam-based alignment and feedback systems are also outlined.

A recipe for linear collider final focus system design

The design of final focus systems for linear colliders is challenging because of the large demagnifications needed to produce nanometer-sized beams at the interaction point. Simple first- and second-order matrix matching have proven insufficient for this task, and minimization of third- and higher-order aberrations is essential. An appropriate strategy is required for the latter to be successful. A recipe for final focus design, and a set of computational tools used to implement this approach, are described herein. An example of the use of this procedure is given.

Ground motion and vibration issues for accelerators

Ground motion and vibration can be a limiting factor in the performance of future colliders, in particular linear colliders and large hadron colliders. Investigations of ground motion have been carried out around the world for several decades. In this review, after brief discussion of ground motion requirements for NLC, TESLA and VLHC, the results of recent investigations of ground motion are presented as well as stabilization techniques developed for the NLC.

Ground Motion Model of the SLAC Site

The authors present a ground motion model for the SLAC site. This model is based on recent ground motion studies performed at SLAC as well as on historical data. The model includes wave-like, diffusive and systematic types of motion. An attempt is made to relate measurable secondary properties of the ground motion with more basic characteristics such as the layered geological structure of the surrounding earth, depth of the tunnel, etc. This model is an essential step in evaluating sites for a future linear collider.