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Leica Laser Tracker erfüllen höchste Ansprüche in der Forschung

Rationalisierung hoch-technischer Anforderungen
Die neue Photonen-Lichtquelle (Advanced Photon Source, APS) hört sich an, als käme sie aus einer Star-Trek-Episode. Tatsächlich ist die APS eine Forschungsanstalt der dritten Generation für die Synchrotron-Strahlung und spielt eine wichtige Rolle in der Welt der aufsehenerregenden Grundlagenforschung. Es gibt nur drei derartige Lichtquellen in der Welt. Die APS befindet sich im Argonne Nationalen Laboratorium, das die Universität in Chicago im Auftrag des Amerikanischen Energieministeriums betreibt.
Autor: Belinda Jones

Using high-brilliance x-ray beams from the APS, members of the international synchrotron-radiation research community carry out basic and applied research in the fields of materials science, biology, physics, chemistry, environmental, geophysical, planetary science and innovative x-ray instrumentation. During the year more than 2’500 users will carry out research at the APS, where interdisciplinary teams of scientists and engineers can work together. That annual number of users is expected to grow to more than 4,000 with the implementation of all 70 beamlines.

APS researchers are either members of Collaborative Access Teams (CATs) or independent investigators (IIs), individuals not affiliated with a CAT. CATs comprise large numbers of scientists with common research objectives. These teams are responsible for the design, construction, funding and operation of beamlines designed to take radiation from the APS storage ring and tailor it to meet specific experiment needs. CATs must also allocate 25% of their x-ray beam time to IIs.

APS Installation Called for Unprecedented Precision

At Argonne, the Accelerator Systems Division (ASD) maintains the APS accelerators that are essential for the production of x-rays. Horst Friedsam, the ASD Survey and Alignment Group Leader, recalls the APS was one of the first accelerators that utilized laser tracker technology extensively during its construction and installation of components. Mr. Friedsam has a Masters degree in Geodesy from Bonn University, Germany and has been involved with the alignment of various accelerators for the past 20 years.
“We used one of the first commercially available Smart 310 trackers from Leica Geosystems for positioning accelerator components,” states Mr. Friedsam. “Only through the use of laser trackers were we able to stay on track with a severely compressed installation schedule. We were interested in the laser tracker systems because of their accuracy, speed, and real-time alignment capability. But, the feature that saved us the most time was the tracker’s ability to perform real-time online alignment of components. We had to hold exceedingly high tolerances. The software had most of the needed features built-in for this process and that made for easy operation of the tracker systems. Today, laser trackers are the backbone for most of our tasks.”

Leica laser trackers are mobile, state-of-the-art industrial measurement systems used for inspection, analysis, and component alignment for a variety of applications in manufacturing and engineering. The trackers are very portable, and the Leica sensor head (less than 70 lbs.) makes it easy to move from sector to sector in the APS setting. Besides positioning APS accelerator components, these systems are used for mapping as-built conditions and fiducialization of beam elements.

Mr. Friedsam estimates the efficiency for aligning accelerator components has increased by almost 50% compared to the commonly used processes prior to the introduction of the laser tracker technology. “This technology has introduced a high degree of automation that in turn has the added benefit of reducing the amount of human mistakes during the measurement process. Nevertheless, we still employ the multiple measurement sets in order to gain redundancy for error detection,” remarked Mr. Friedsam.

High Demand, High Precision, Quality Inspections

At Argonne, the APS is always in high demand, and therefore must be in top working order. Mr. Friedsam states that there is very little downtime, and when it comes around, his team must get busy. Since the installation of the APS, Argonne has upgraded to the Leica LTD500 laser tracker and its patented Absolute Distance Meter for point-and-shoot measuring of components. Argonne’s ASD now owns three laser trackers and puts them all to full usage.

The APS has three one-month downtime periods distributed throughout the year. The ASD Survey and Alignment team visits the various accelerator areas to check for settlements, and if necessary, to make adjustments. There are 40 sectors in the APS, but not all sectors have beamlines implemented as of yet. This year, the ASD team is working on two specific tasks. They are extracting the current position of the beam guiding elements, and implementing a new lattice layout in the storage ring. The first task involves the extensive use of the laser tracker’s auto-inspect mode in conjunction with up to 40 open-air corner cubes used to outfit all visible targets in the vicinity of a particular tracker station. The second task makes use of the real-time alignment capability of the LTD500. The measured and ideal component position is compared and the differences in the three coordinate directions displayed in real time while adjustments are applied.

Argonne Pioneers Wireless APS Inspections

“With the development of the LTD500 and the built-in absolute distance measurement capability, we adopted a new measurement routine that allows us to measure pre-existing control points in the auto-inspect mode, said Mr. Friedsam. “However, we discovered that the small cross section of the accelerator enclosure interfered with the size of the Leica transportation and supply cart. We began looking for a simpler solution that would reduce the size of the necessary equipment for operating the tracker.”
“Recently, new wireless laptops have come of age. We began to toy with the idea of a laptop equipped with a wireless LAN board to control the laser tracker. We mounted the controller to the tracker base thus creating two independent devices. This scenario has additional benefits. The large cables connecting the LTD500 to the cart-mounted tracker controller are now reduced in length, and do not have to be removed for transporting the laser tracker,” concluded Mr. Friedsam.

This new innovation also called for an appropriate wireless interface on the tracker controller side. The ASD team decided to mount a wireless port that converts the controller signals, which are normally transmitted by cable, to an RF signal that can be received by the laptop. “All of these items were commercially available,” said Mr. Friedsam. “We purchased these components and assembled the system for a test run to prove the viability of the idea. After overcoming a few operating system and driver issues, we were able to make this concept work. So far, basic inspection work has been performed with the modified system.”
The ASD team will continue testing the wireless systems to eliminate any unforeseen problems. Most laptops now provide access to multiple accessory cards, so Mr. Friedsam thinks it will be possible to operate multiple laser trackers from just one laptop in the future.

Argonne’s policy is not to endorse any product, service or company. Leica Geosystems is very appreciative for the remarks by the ASD team, and their statements reflect solely on the technology presented by the LTD500, in their individual experience.


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