The LCLS hard X-ray Free Electron Laser at SLAC reported first lasing in April 2009. Since then two successful user runs have been completed at the two soft X-ray stations. The first hard X-ray station has started commissioning in July 2010. Beam diagnostics play an essential role for tuning the machine and delivering the requested beam properties to the users. An overview of the LCLS photon diagnostics will be presented including some selected commissioning results. Plans for future improvements and upgrades will be briefly discussed.

The recently commissioned Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs (10 −15 s). With these beam characteristics this light source is capable of imaging the structure and dynamics of matter at atomic size and timescales. The facility is now operating at X-ray wavelengths from 22 to 1.2 Å and is presently delivering this high-brilliance beam to a growing array of scientific researchers. We describe the operation and performance of this new ‘fourth-generation light source’.

The DAQ/HLT system of the ATLAS experiment at CERN, Switzerland, is being commissioned for first collisions in 2009. Presently, the system is composed of an already very large farm of computers that accounts for about one-third of its final event processing capacity. Event selection is conducted in two steps after the hardware-based Level-1 Trigger: a Level-2 Trigger processes detector data based on regions of interest (RoI) and an Event Filter operates on the full event data assembled by the Event Building system. The detector read out is fully commissioned and can be operated at its full design capacity. This places the responsibility on the High-Level Triggers system to select only events of highest physics interest that will finally reach the offline reconstruction farms. This paper brings an overview of the current ATLAS DAQ/HLT implementation and performance based on studies originated from its operation with simulated, cosmic particles and first-beam data. Its built-in event processing parallelism is presented and discussed.

The linac coherent light source (LCLS) is a SASE X- ray free-electron laser (FEL) project presently under construction at SLAC [1]. The injector section, from drive-laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam is taking place during the spring and summer of 2007. The second phase of construction, including second bunch compressor and full linac, will begin later, in the fall of 2007. We report here on experience gained during the first phase of machine commissioning, including RF photocathode gun, linac booster section, S-band and X-band RF systems, first bunch compressor, and the various beam diagnostics.

During the past five years, there has been an concerted program at SLAC and KEK to develop accelerator structures that meet the high gradient (65 MV/m) performance requirements for the Next Linear Collider (NLC) and Global Linear Collider (GLC) initiatives. The design that resulted is a 60-cm-long, traveling-wave structure with low group velocity and 150 degree per cell phase advance. It has an average iris size that produces an acceptable short-range wakefield, and dipole mode damping and detuning that adequately suppresses the long-range wakefield. More than eight such structures have operated at a 60 Hz repetition rate over 1000 hours at 65 MV/m with 400 ns long pulses, and have reached breakdown rate levels below the limit for the linear collider. Moreover, the structures are robust in that the rates continue to decrease over time, and if the structures are briefly exposed to air, the rates recover to their low levels within a few days. This paper presents a summary of the results from this program, which effectively ended last August with the selection of ‘cold’ technology for an International Linear Collider (ILC).

The LCLS injector is required to provide a 1-nC, 10-ps bunch with a normalized rms transverse projected emittance of less than 1 micron. The LCLS beam is generated and accelerated in a 1.6-cell S-band RF gun at 120 MV/m up to 6 MeV. The gun is followed by two SLAC 3-m S-band accelerator structures to further accelerate the beam to 135 MeV which moves the beam out of the space-charge dominated regime. In the SLAC S-band structures, the RF power feed is through a single coupling-hole (single-feed coupler) which results in a field asymmetry. The time dependent multipole fields in the coupler induce a transverse kick along the bunch and cause the emittance to increase above the LCLS specification. To meet the stringent emittance requirements for the injector, the single-feed couplers will be replaced by a dual-feed racetrack design to minimize the multipole field effects. We will present detailed studies of the multipole fields in the SLAC linac RF coupler and the improvements with the dual-feed ractrack design using the parallel finite element S-parameter solver S3P.

The SLD Cherenkov Ring Imaging Detector uses a proportional wire detector for which a single channel hybrid has been developed. It consists of a preamplifer, gain selectable amplifier, load driver amplifier, power switching, and precision calibrator. For this hybrid, a bipolar, semicustom, integrated circuit has been designed which includes video operational amplifiers for two of the gain stages. This approach allows maximization of the detector volume, allows DC coupling, and enables gain selection. System tests show good noise performance, calibration precision, system linearity, and signal shape uniformity over the full dynamic range.

We have produced 400 ns rf pulses of greater than 500 MW at 11.424 GHz with an rf system designed to demonstrate technology capable of powering a TeV scale electron-positron linear collider (NLC). Power is produced by four 50 MW X-band klystrons run off a common 400 kV solid-state modulator. We present the layout of our system, which includes a dual-moded transmission waveguide system and a dual-moded resonant-line (SLED-II) pulse compression system. Dual-moding of the transmission lines allows power to be directed through a pulse compression path or a bypass path; dual-moding in the pulse compressor allows the delay lines to be about half as long as they otherwise would need to be. We describe the design and performance of various components, including hybrids, directional couplers, power dividers, tapers, mode converters, and loads. These components are mostly overmoded to allow for greater power handling. We also present data on the processing and operation of this system, which is setting high-power records in pulsed rf.

Summary form only. The performance of the Cherenkov Ring Imaging Detector (CRID) of the SLD experiment at the SLAC linear collider during the 1992 physics data run is discussed. The barrel CRID is complete and fully operational. Cherenkov rings have been observed from both the liquid and the gas radiators. The rings are associated with particle tracks measured in the central drift chamber and the radius of the ring together with the momentum measurement is used to identify particles. Work is in progress to improve the resolution by better determining the position of the drift boxes, the mirrors, and the central drift chamber relative to one other using data from cosmic rays and Z/sup 0/ chambers. >

An RF polarized electron gun utilizing the unique features of an integrated, plane-wave-transformer (PWT) photoelectron injector is being developed by DULY Research Inc. in collaboration with SLAC. Modifications to a DULY S-band device include: a re-design of the photocathode/RF backplane interface to accommodate a GaAs cathode; change in the design of the vacuum ports to provide 10/sup -11/ Torr operation; the inclusion of a load-lock photocathode replacement system to allow for reactivation and cesiation of the GaAs photocathode in a vacuum; and alteration of the magnet field coils to make room for the load-lock. The use of a stainless steel outer tank and cooling rods without copper plating may also provide better vacuum performance at the expense of diminished Q-factor. The effectiveness of both the standard cooling rods and synthetic diamond heat sinks for disk cooling is investigated for future linear collider applications operating at a rep rate of 180 Hz and a bunch charge of 2 nC.

During the PEP-II LER commissioning run in July 1998 the beam profile in the tune up dump profile monitor just before LER injection showed an anomalous parabolic shape. The sextupole component of the field of bend magnets B2 and B4 in the beginning of the south injection tunnel (SIT) was thought to be the cause of this. An off-line model of the B2/B4 bend magnet field was created using DIMAD. Results of particle tracking simulated in DIMAD were compared with on-line lattice diagnostic data and observations of the beam profile on the tune up dump screen

The Barrel GRID detector has been operating successfully at SLD for the past seven years. It is an important tool for SLD physics analyses. We report results based on long term operational experience of a number of important quantities such as the Cherenkov quality factor, N-0, of the device, fluid transparency, electron lifetime, single electron detection efficiency, anode wire ageing, TMAE purity, long term stability of the gas refraction index, liquid radiator transparency, Cherenkov angle resolution and the number of photoelectrons observed per ring.

Since 1992, the SLAC 3-km linac has operated exclusively with polarized electrons. The polarized electron source is highly reliable, remotely operated and monitored, and able to produce a variety of electron bunch profiles for high-energy physics experiments. The source and its operating characteristics are described. Some implications drawn from the operating experience are discussed.

Since 1992, the SLAC 3-km linac has operated exclusively with polarized electrons. The polarized electron source is highly reliable, remotely operated and monitored, and able to produce a variety of electron bunch profiles for high-energy physics experiments. The source and its operating characteristics are described. Some implications drawn from the operating experience are discussed. Invited presentation at the Seventh International Workshop on Polarized Gas Targets and Polarized Beams University of Illinois at Urbana-Champaign, IL August 18-22, 1997 ∗ Work supported by the U.S. Department of Energy contract DE-AC03-76SF00515.

Installation of the PEP-II electron and positron injection beamlines in the SLAC linac housing is now underway. Utilization of the existing high power, low emittance beams available at SLAC required that a great portion of the systems for pulsed extraction and transport of 9.0 GeV electrons and 3.1 GeV positrons for injection into the PEP-II rings will reside in the existing linac housing. Approximately 4.7 kilometers of these beamlines will be completed during the summer of 1995. All components, including orbit correctors and diagnostic instruments, required for extraction and transport of the electron beam will be in place and ready for commissioning as soon as this fall (1996). The positron transport line in the housing will also be complete except for the pulsed extraction system. These systems are described, along with the status of the construction and installation of the important subsystems such as magnets and power supplies, vacuum systems, instrumentation and controls. The plan for commissioning is discussed.

We describe the likelihood ratio method used for particle identification in the SLD CRID, which allows the use of the entire momentum range covered by the liquid and gas radiators, including the threshold regions. Its application to two preliminary physics analyses is also described.