The alignment of the Arcs for the Stanford Linear Collider at SLAC has posed problems in accelerator survey and alignment not encountered before. These problems come less from the tight tolerances of 0.1 mm, although reaching such a tight statistically defined accuracy in a controlled manner is difficult enough, but from the absence of a common reference plane for the Arcs. Traditional circular accelerators, including HERA and LEP, have been designed in one plane referenced to local gravity. For the SLC Arcs no such single plane exists. Methods and concepts developed to solve these and other problems, connected with the unique design of SLC, range from the first use of satellites for accelerator alignment, use of electronic laser theodolites for placement of components, computer control of the manual adjustment process, complete automation of the data flow incorporating the most advanced concepts of geodesy, strict separation of survey and alignment, to linear principal component analysis for the final statistical smoothing of the mechanical components.

At the Stanford Linear Accelerator Center (SLAC) a new project is underway to build an electron-positron collider, the Stanford Linear Collider (SLC). This paper gives an overview of the alignment procedure for this project, followed by a detailed description of the first step in the alignment. In this part of the procedure pedestals are set in pitch and yaw and brought into +-3 mm of their final three-dimensional position by use of two intersecting laser beams. The fixturing and instrumentation are described, together with the software and data-flow which are used. Finally, the results obtained with this method are discussed, and conclusions are drawn on its effectiveness.

GEONET is a database system developed at the Stanford Linear Accelerator Center for the alignment of the Stanford Linear Collider. It features an automated data flow, ranging from data collection using HP110 handheld computers to processing, storing and retrieving data and finally to adjusted coordinates. This paper gives a brief introduction to the SLC project and the applied survey methods. It emphasizes the hardware and software implementation of GEONET using a network of IBM PC/XT's.

Geodetic measurements even of a defined project produce a vast amount of heterogeneous data. The analysis of these data used to be time-and-manpower consuming and only focused on subsets of the data. This paper demonstrates how an integrated database system will provide an immediate standardized and easy access to the entire information support data management, and, consequently, streamline the analysis. 17 refs., 12 figs., 6 tabs.

The Stanford Linear Accelerator Center (SLAC) is in the process of building a new particle collider, the Stanford Linear Collider (SLC). The tunnel which houses the SLC is about 3 km long and contains approximately 1000 magnets. Besides a very precise absolute positioning of these magnets, the alignment of adjacent magnet ends is of particular importance to the success of the whole project. Because of this and the limited time frame, a survey method which was not only reliable and self-checking but also fast had to be developed. Therefore, the concept of MAS (Magnet Alignment System) was developed. This system utilizes the on-line data collection and the rigorous least-squares bundle adjustment of the KERN ECDS-PC system to fulfill these requirements. The ECDS software is embedded in a project tailored software system with modules which take care of: fixture and magnet calibration corrections, the calculation of ideal coordinates and their comparison to measured coordinates, the translation of detected misalignments into the coordinate system of the mechanical adjustments and the control of the adjustments with on-line electronic dial-gauges. This paper gives a brief introduction to the SLC project and some of the survey problems which are unique to this machine. The basicmore » ideas of the KERN ECDS-PC system are explained and a discussion of the practical aspects, such as targeting and set-ups, are given. MAS and its modules are explained in detail.« less

Any measurement task requires a fixed reference base (the datum) from which measurements can be made and calculated. The linac was the datum to which all SLC components were aligned; although this reference existed as a physical object, the actual establishment of the datum and its transferral to datums that were more useful for the SLC installation challenged the technology and computational ability of the survey group. Once established, the maintenance of datums is not to be taken for granted, as demonstrated by the 1989 earthquake which destroyed all SLAC's survey datums. 7 refs., 6 figs.

At SLAC (Stanford Linear Accelerator Center) a fully automated vertical comparator for the calibration of digital levels and invar staffs was developed by the Metrology Department in cooperation with the Institute of Engineering Geodesy and Measurement Systems at the Graz University of Technology. This vertical comparator is the first in the US. With the vertical comparator it is possible to perform System Calibration and CCD Camera Measurements of rods. System Calibration uses the height readings of the digital level at different positions of the rod and compares them with the reference readings obtained by the interferometer. In the case of CCD Camera Measurements, the position of the edges in the image is determined and again compared with the interferometer readings. This document gives an overview over the current set-up of the SLAC vertical comparator and experimental results of critical applications like measurements at the end sections of the rod, at critical sighting distances, with unfocused measurements and under artificial illumination with the digital levels in use at SLAC.

Physics experiments at the SLAC National Accelerator Laboratory (SLAC) usually require high accuracy positioning, e. g. 100 {micro}m over a distance of 150 m or 25 {micro}m in a 10 x 10 x 3 meter volume. Laser tracker measurement systems have become one of the most important tools for achieving these accuracies when mapping components. The accuracy of these measurements is related to the manufacturing tolerances of various individual components, the resolutions of measurement systems, the overall precision of the assembly, and how well imperfections can be modeled. As with theodolites and total stations, one can remove the effects of most assembly and calibration errors by measuring targets in both direct and reverse positions and computing the mean to obtain the result. However, this approach does not compensate for errors originating from the encoder system. In order to improve and gain a better understanding of laser tracker angle measurement tolerances we extended our laboratory's capabilities with the addition of a horizontal angle calibration test stand. This setup is based on the use of a high precision rotary table providing an angular accuracy of better than 0.2 arcsec. Presently, our setup permits only tests of the horizontal angle measurement system. Amore » test stand for vertical angle calibration is under construction. Distance measurements (LECOCQ & FUSS, 2000) are compared to an interferometer bench for distances of up to 32 m. Together both tests provide a better understanding of the instrument and how it should be operated. The observations also provide a reasonable estimate of covariance information of the measurements according to their actual performance for network adjustments.« less

Physics experiments at SLAC require high accuracy positioning, e. g. 100 {micro}m over a distance of 150 m or 25 {micro}m in a 10 x 10 x 3 meter volume. Laser Tracker measurement systems have become one of the most important tools for achieving these accuracies when mapping components. In order to improve and get a better understanding of laser tracker measurement tolerances we extended our laboratory with a rotary calibration table (Kugler GmbH) providing an accuracy of better than 0.2 arcsec. This paper gives an overview of the calibration table and its evaluation. Results of tests on two of our Laser Trackers utilizing the new rotary table as well as the SLAC interferometer bench are presented.

At SLAC (Stanford Linear Accelerator Center) a fully automated vertical comparator for the calibration of digital levels and invar staffs was developed by the Metrology Department in cooperation with the Institute of Engineering Geodesy and Measurement Systems at the Graz University of Technology. This vertical comparator is the first in the US. With the vertical comparator it is possible to perform system calibration and CCD camera measurements of rods. System calibration uses the height readings of the digital level at different positions of the rod and compares them with the reference readings obtained by the interferometer. In the case of CCD camera measurements, the positions of the edges in the image is determined and again compared with the interferometer readings. This document gives an overview of the current set-up of the SLAC vertical comparator and experimental results of critical applications including measurements at the end sections of the rod, at critical sighting distances, with unfocused optics and under illumination with the digital levels in use at SLAC.

Digital levels replaced spirit levels in most fields of precise height measurements because of the automation of the height readings. Three manufacturers offer digital levels with a single reading resolution of 10 p,m, and for all of them systematic effects are known. In Europe several facilities for system calibration of digital levels using vertical comparators were established within the last decade. However, there still was no system calibration facility in North America. In order to guarantee the accuracy required for the alignment of experiments at the Stanford Linear Accelerator Center (SLAG) a calibration facility for the system calibration of digital levels was built. In this paper the setup of the SLAG vertical comparator is described in detail and its standard uncertainty is derived. In order to perform traditional rod calibration of conventional line-scaled rods, a CCD camera was integrated into the SLAG comparator. The CCD camera setup is also briefly described. To demonstrate the capabilities of the comparator, results of system and rod calibration are shown.

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC.

At SLAC digital levels are used for precise leveling, both for setting out and monitoring. A very high precision of 30 {micro}m is required, which can only be achieved by regularly calibrating the leveling equipment. The calibration facility is also used for detailed investigations to refine the SLAC leveling procedure. In this paper the setup of the SLAC vertical comparator is described. In order to also perform traditional staff calibration a CCD camera was integrated into the SLAC comparator. Finally an overview of further investigations of our leveling equipment is presented.

To reach design luminosity, the International Linear Collider (ILC) must be able to create and reliably maintain nanometer size beams. The ATF damping ring is the unique facility where ILC emittances are possible. In this paper we present and evaluate the proposal to create a final focus facility at the ATF which, using compact final focus optics and an ILC-like bunch train, would be capable of achieving 37 nm beam size. Such a facility would enable the development of beam diagnostics and tuning methods, as well as the training of young accelerator physicists.

The Stanford Linear Accelerator Center is evaluating the feasibility of placing a free electron laser (FEL) at the end of the linear accelerator. The proposal is to inject electrons two thirds of the way down the linac, accelerate the electrons for the last one third of the linac, and then send the electrons into the FEL. This project is known as the LCLS (Linac Coherent Light Source). To test the feasibility of the LCLS, a smaller experiment VISA (Visual to Infrared SASE (Self Amplified Stimulated Emission) Amplifier) is being performed at Brookhaven National Laboratory. VISA consists of four wiggler segments, each 0.99 m long. The four segments are required to be aligned to the beam axis with an rms error less than 50 {micro}m [1]. This very demanding alignment is carried out in two steps [2]. First the segments are fiducialized using a pulsed wire system. Then the wiggler segments are placed along a reference laser beam which coincides with the electron beam axis. In the wiggler segment fiducialization, a wire is stretched through a wiggler segment and a current pulse is sent down the wire. The deflection of the wire is monitored. The deflection gives information about the electronmore » beam trajectory. The wire is moved until its x position, the coordinate without wire sag, is on the ideal beam trajectory. (The y position is obtained by rotating the wiggler 90{sup o}.) Once the wire is on the ideal beam trajectory, the wire's location is measured relative to tooling balls on the wiggler segment. To locate the wire, a device was constructed which measures the wire position relative to tooling balls on the device. The device is called the wire finder. It will be discussed in this paper. To place the magnets along the reference laser beam, the position of the laser beam must be determined. A device which can locate the laser beam relative to tooling balls was constructed and is also discussed in this paper. This device is called the laser finder. With a total alignment error budget less than 50 {micro}m, both the fiducialization and magnet placement must be performed with errors much smaller than 50 {micro}m. It is desired to keep the errors from the wire finder and laser finder at the few {micro}m level.« less

Particular care had to be taken in the design and implementation of the geodetic control systems for the Superconducting Super Collider (SSC) due to stringent accuracy requirements, the demanding tunnelling schedule, long duration and large size of the construction effort of the project. The surveying requirements and the design and implementation of the surface and under- ground control scheme for the precise location of facilities which include approximately 120 km of bored tunnel are discussed. The methodology used for the densification of the surface control networks, the technique used for the transfer of horizontal and vertical control into the underground facilities, and the control traverse scheme employed in the tunnels is described.

These tests have shown that fast and accurate alignment of accelerator components is possible using the non-metric Kodak DCS 460m digital camera shortly after being calibrated. The two software packages provided comparable solutions. Short term repeatability was achieved. The effect of orientation changes, camera jarring and the lack of long term repeatability, all point toward an internal displacement of the CCD chip.

Supporting physics experiments is the ultimate goal for any group at SLAC in either a direct or indirect fashion. Metrology does both through hands-on measurements of existing or future accelerator components and supporting hardware. Specifically, the Alignment Engineering Group does this through surveying and mapping while Magnetic Measurements does it through actual electo-mechanical measurements of magnets, and Quality Insurance through probes, images and other quality control techniques. All these activities involve continuous monitoring and updating of various accelerator alignment technologies through study, practical experience, or various conferences offered throughout the world.