098(E13-2007-98) - E13-2007-98 V Batusov1 J Budagov1 J...

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ОБЪЕДИНЕННЫЙ ИНСТИТУТ ЯДЕРНЫХ ИССЛЕДОВАНИЙ Дубна E13-2007-98 Submitted to the journal «Particles and Nuclei, Letters» 2007 V. Batusov , J. Budagov , J. Khubua , C. Lasseur , M. Lyablin , N. Russakovich , A. Sissakian , N. Topilin ,* 11 1 2 1 1 1 2 JINR, Dubna, Russia CERN, Geneva, Switzerland * On leave from the Institute of High Energy Physics and Informatization, Tbilisi, Georgia ON A LASER BEAM FIDUCIAL LINE APPLICATION FOR METROLOGICAL PURPOSES
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INTRODUCTION When metrology measurements execution has to be achieved, the question of so-called «fiducial points» (FP) positioned on the object to be measured and on the mea- surement stations forming a surrounding or a linear net- work has to be raised. One assumes that the relative loca- tions of these FPs on object and stations have been well understood and foreseen so that the correct and comfort- able executing of the measurements, network and object under study, can be achieved. As a rule, the «long-term» FPs and the measurement stations have a fixed contact with the rock monolith — pillar embedded in soil — that can be equipped with a suitable mechanic tooling for po- sitioning precisely standard measurement units like theodolites, targets, prisms for measuring distances, etc. and in very accurate repetitive mode. As the experience shows, their relative long-term stability on about 100 m base is enough to perform, for a few years, measurements with a relative precision of~10 6 - [1–3]. In some cases it might be useful to foresee some pure mechanical or opti- cal verification devices of centering structure (clinome- ters, short leveling from deep rods, etc.) in order to verify that no accidental bumps have occurred. In the metrology measurement the «fiducial lines» (FL) are often used. They represent a set of FPs aligned along some line(s). For example, the measurements sta- tions are sockets embedded in the tunnel floor and are used to install the LHC elements of which the accuracy is about 1 mm within the main geometrical frame all along the accelerator. The final relative locations of the adja- cent machine elements — Q poles to Q poles, magnets to magnets — are cross-checked section by section with re- spect to the smoother line within the best accuracy (a few tenths of a millimeter) by using one unique stretched wire attached to the FPs of the controlled elements [4–7]. High-accuracy measure and devices, redundancy when- ever possible, cross-checks, errors tracing — specifically when controlling a unique straight section must be con- sidered at all stages of a given process. That is a so-called string metrology when the metrol- ogy task is to perform the measurements relative to some straight line [8–10]. The used device represents a me- chanical setup where two FPs are connected by a tensed string, the real measures being horizontal or planar radial offsets measurements on intermediate FPs onto the string. The immovability and the datum of the straight line are guaranteed by the extreme FPs and the accurate
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098(E13-2007-98) - E13-2007-98 V Batusov1 J Budagov1 J...

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