N. Kurita

The CSPAD megapixel x-ray camera at LCLS

The Linear Coherent Light Source (LCLS), a free electron laser operating from 250eV to10keV at 120Hz, is opening windows on new science in biology, chemistry, and solid state, atomic, and plasma physics1,2. The FEL provides coherent x-rays in femtosecond pulses of unprecedented intensity. This allows the study of materials on up to 3 orders of magnitude shorter time scales than previously possible. Many experiments at the LCLS require a detector that can image scattered x-rays on a per-shot basis with high efficiency and excellent spatial resolution over a large solid angle and both good S/N (for single-photon counting) and large dynamic range (required for the new coherent x-ray diffractive imaging technique3). The Cornell-SLAC Pixel Array Detector (CSPAD) has been developed to meet these requirements. SLAC has built, characterized, and installed three full camera systems at the CXI and XPP hutches at LCLS. This paper describes the camera system and its characterization and performance.

Bellows design for the PEP-II High Energy Ring arc chambers

An overview of the current bellows module design and performance parameters is presented. Performance requirements based on external chamber design constraints, and operational needs are discussed. Parameters include beam impedance of the RF shield, and electrical resistance of the shield gap joint. Also discussed is the analysis of the high-current thermal management, and structural and cyclic behavior of the bellows and RF shield. Experiments of the tribology and electrical resistance of the shield sliding joint are summarized, and their results presented. Existing and new design options are discussed in light of the analyses and experiments. The final design is presented as the optimal compromise between the varying parameters.

The vacuum system for the PEP II High Energy Ring straight sections

The six straight insertions of the PEP II High Energy Ring (HER) serve various functions: lattice tuning, beam injection and abort, providing space for RF cavities, longitudinal and transverse feedback, beam diagnostics and the interaction point. A stainless steel vacuum system has been designed; prototypes are currently being built. Cooling is required due to radiation coming from the last arc dipole and resistive losses in the vacuum chamber. Although the nominal beam current of the HER is 1 A the vacuum system is designed for 3 A to provide margin and an upgrade path.

Design of the button beam position monitor for PEP-II

We use MAFIA to analyze the PEP-II button-type beam position monitor (BPM). Employing proper termination of the BPM into a coaxial cable, the output signal at the BPM is determined. Thus the issues of signal sensitivity and power output can be addressed quantitatively, including all transient e ects and wake elds. Besides this rst quantitative analysis of a true BPM 3D structure, we nd that internal resonant modes are a major source of high value narrow-band impedances. The e ects of these resonances on coupled-bunch instabilities are discussed. An estimate of the power dissipation in the ceramic vacuum seal under high current operation is given. Presented at the Workshop on Collective E ects and Impedance for B-Factories, Tsukuba, Japan, June 12-17, 1995 Work supported by Department of Energy, contract DE-AC03-76SF00515.The beam position monitor (BPM) was designed to provide a robust UHV feedthru and a reliable electromagnetic sensor. Stringent resolution requirements at low beam currents, bunch parameters, along with mechanical and chamber requirements produced challenges in the electrical, thermal, and structural design of the BPMs. Numerical modeling and experimental analyses were used to optimize the design. The higher order modes (HOMs) and beam impedance were modeled using MAFIA. Measurements agreed with the calculated 1 /spl Omega/ transfer impedance at the 952 MHz signal processing frequency, and the first two HOMs found in MAFIA. Tests and analysis both showed the button signal power approaching 40 W. Temperature and stress distributions were analyzed using this power loading with ANSYS. An electronic grade CuNi was selected for the BPM to reliably weld into the copper chambers. Pin seal and compressive joints were considered for the insulator vacuum seals. Both glassy ceramic-to-metal and ceramic-to-metal seals were evaluated.

LCLS Ultrafast Science Instruments:Conceptual Design Report

The Stanford Linear Accelerator Center (SLAC), along with Argonne National Laboratory (ANL), Lawrence Livermore National Laboratory (LLNL), and the University of California at Los Angeles (UCLA), is constructing a Free-Electron Laser (FEL) facility, which will operate in the wavelength range 1.5 nm - 0.15 nm. This FEL, the Linac Coherent Light Source (LCLS), utilizes the SLAC linac and will produce sub-picosecond pulses of short wavelength X-rays with very high peak brightness and almost complete transverse coherence. The final one-third of the SLAC linac will be used as the source of electrons for the LCLS. The high energy electrons will be transported across the SLAC Research Yard, into a tunnel which will house a long undulator. In passing through the undulator, the electrons will be bunched by the force of their own synchrotron radiation and produce an intense, monochromatic, spatially coherent beam of X-rays. By varying the electron energy, the FEL X-ray wavelength will be tunable from 1.5 nm to 0.15 nm. The LCLS will include two experimental halls as well as X-ray optics and infrastructure necessary to create a facility that can be developed for research in a variety of disciplines such as atomic physics, materials science, plasma physics and biosciences. This Conceptual Design Report, the authors believe, confirms the feasibility of designing and constructing three X-ray instruments in order to exploit the unique scientific capability of this new LCLS facility. The technical objective of the LCLS Ultrafast Science Instruments (LUSI) project is to design, build, and install at the LCLS three hard X-ray instruments that will complement the initial instrument included in the LCLS construction. As the science programs advance and new technological challenges appear, instrumentation needs to be developed and ready to conquer these new opportunities. The LCLS instrument concepts have been developed in close consultation with the scientific community through a series of workshops team meetings and focused reviews. In particular, the LUSI project instruments have been identified as meeting the most urgent needs of the scientific community based on the advice of the LCLS Scientific Advisory Committee (SAC) in response to an open call for letters of intent (LOI) from the breadth of the scientific community.

Mechanical design of the HER synchrotron light monitor primary mirror for the PEP-II B-Factory

This paper describes the mechanical design of the primary mirror that images the visible portion of the synchrotron radiation (SR) extracted from the High Energy Ring (HER) of the PEP-II B-Factory. During off-axis operation, the water-cooled GlidCop mirror is subjected to a heat flux in excess of 2000 W/cm/sup 2/. When on-axis imaging occurs, the heat flux due to scattered SR, resistive wall losses and Higher-Order-Mode (HOM) heating is estimated at 1 W/cm/sup 2/. The imaging surface is plated with electroless nickel to improve its optical characteristics. The design requirements for the primary mirror are listed and discussed. Calculated mechanical distortions and stresses experienced by the mirror during on-axis and off-axis operation are presented.

Impedance study for the PEP-II B-factory

The paper summarizes results of the impedance studies of the components of the B-factory. The prime goal of this activity was to support the design of the vacuum chamber and, at the same time, to get reasonable model of the machine impedance, which can be used later for detail studies of collective effects.

Final design and manufacturing of the PEP-II High Energy Ring arc bellows module

An update on the arc bellows module for the PEP-II High Energy Ring is presented. Final design, manufacturing issues, material and coating selection, and tribological and RF testing are discussed. Performance and operational requirements are also reviewed. The RF shield design has been proven during assembly to allow for large manufacturing tolerances without reducing the mechanical spring force below required values. In addition, the RF shield maintains electrical contact even with large misalignments across the module.

Management evolution in the LSST project

The Large Synoptic Survey Telescope (LSST) project has evolved from just a few staff members in 2003 to about 100 in 2010; the affiliation of four founding institutions has grown to 32 universities, government laboratories, and industry. The public private collaboration aims to complete the estimated

A zero-length bellows for the PEP-II High-Energy Ring

450 M observatory in the 2017 timeframe. During the design phase of the project from 2003 to the present the management structure has been remarkably stable. At the same time, the funding levels, staffing levels and scientific community participation have grown dramatically. The LSSTC has introduced project controls and tools required to manage the LSSTs complex funding model, technical structure and distributed work force. Project controls have been configured to comply with the requirements of federal funding agencies. Some of these tools for risk management, configuration control and resource-loaded schedule have been effective and others have not. Technical tasks associated with building the LSST are distributed into three subsystems: Telescope & Site, Camera, and Data Management. Each sub-system has its own experienced Project Manager and System Scientist. Delegation of authority is enabling and effective; it encourages a strong sense of ownership within the project. At the project level, subsystem management follows the principle that there is one Board of Directors, Director, and Project Manager who have overall authority.