Departmental Seminar

Particle physics keeps old bridges, tunnels and buildings from collapsing!

Dr Joris van Heijningen
OzGrav - University of Western Australia

The Rasnik alignment system [1] was developed initially in 1983 for the monitoring of the alignment of the muon chambers of the L3 Muon Spectrometer at CERN. Since then, the development continued since new electro-optical components became available and new ideas surfaced. This talk will give an overview of the technical developments and achievements. Roughly 10000 systems have been installed in the ATLAS and LHCb experiments at CERN. Outside science, several civic structures, such as (snowed over) large span roofs and aged bridges or tunnels, are monitored.

Rasnik systems are 3-point optical displacement monitors (Rasnik is an acronym for Red Alignment System Nikhef) and their performance ranges from below nanometers to several micrometers depending on the design and requirements of the systems. A typical Rasnik image has enough information to reach sub-nanometer precision, according to the Cramér-Rao limit [2]. Recent developments are towards even more precise resolution of tens or hundreds of picometers and the implementation of Rasnik in seismic sensors. Lastly, I will describe with another precision sensor that will be used in particle colliders or future gravitational wave detectors is a cryogenic superconducting accelerometer proposed by the speaker [3].

[1] M. Beker et al, “The Rasnik 3-point optical alignment system”, JINST 14 P08010 (2019) 

[2] J.V. van Heijningen, “Precision improvement in optical alignment systems for linear colliders”, M.Sc. thesis, Nikhef and Delft University of Technology, The Netherlands (2012) 

[3] J.V. van Heijningen, “A fifty-fold improvement of thermal noise limited inertial sensitivity by going cryogenic" (2019), manuscript under review – target: Phys. Rev. D

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