A system to monitor possible displacements of the inner tracking system of ALICE

Bjørn S. Nilsen, David Truesdale, Jiro Fujita, Michael Cherney, Yury Gorbunov, Thomas J. Humanic, Jiri Kral, Benjamin Rizzo

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


In a large collider experiment, the precision of the measurements is often limited by the knowledge of the location of the different sub-detectors which make up such an experiment. In A Large Ion Collider Experiment (ALICE), two such critical sub-detectors are the time projection chamber and the inner tracking system. Here is described a system which can monitor the relative position of these two sub-detector systems with the needed accuracy and within the space available. This system utilizes off the shelf USB web-cameras, diode laser light sources, and spherical mirrors. Tests have shown that it can provide a resolution of 9.4 ± 0.3 μ m for displacements in the plane of the camera and about 78 ± 2 μ m perpendicular to it.

Original languageEnglish (US)
Pages (from-to)176-183
Number of pages8
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number2-3
StatePublished - Feb 11 2009

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Instrumentation


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