RasClic: A long-baseline 3-point alignment system for Linear Accelerators H. Manaud Durand, J-P....

A long-baseline 3-point alignment system for Linear Ac H. Manaud Durand, J-P. Quesnel, T. Touzé CERN TS-SU, Geneva, Switzerland Harry van der Graaf, Henk Groenstege, Elmar Reinhold, Geert Hanraads Nikhef, Amsterdam, The Netherlands Mark Beker, Marc Kea, Hidde Westra Nikhef/Delft University of Technology, The Netherlands Rogier van der Geer Nikhef/University of Leiden, The Netherlands Taylan Tozgorto University of Amsterdam, The Netherlands contact: [email protected] RasClic is a new optical alignment system for large objects like linear accelerators, based on the RASNIK alignment system*. The system is a 3-point straightness monitor consisting of a monochromatic light source, a diffraction plate and a pixel image sensor. By monitoring the position of a diffraction pattern on the image sensor, a measure for the relative positions of the three components is obtained. It has been shown that such a system can meet the required alignment tolerances for use as an alignment system for the Compact Linear Collider (CLIC). * [1] H. Dekker, H. van der Graaf, H. Groenstege, F. Linde, S. Sman, R. Steensma, B. Jongkind, A. Smeulders: The RASNIK/CCD 3-Dimensional Alignment System Proceedings of the 3rd International Workshop on Accelerator Alignment, (IWAA 1993), 28 Sept - 1 Oct 1993, Annecy, France f x s x ,y s y F Ï‰ x , Ï‰ y e i Ï‰ x s x Ï‰ y s y Linearity tests were performed by varying a force on the diffraction plate holder of up to 50 N in the vertical direction. These tests show an excellent position resolution and linearity. Noise behavior of an ideal RasClic compared to the STS-1 and STS-2 seismographs used by the Royal Dutch Institute for Meteorology (KNMI) [13]. The NHNM and NLNM envelopes are the New High- and New Low Noise Models, respectively. These are models for the background noise in seismic measurements due to actual movements in the Earth's crust, during periods of high and low seismic Laser fiber-optic coupling system, eliminating drift in laser beam position RasClic as a Seismograph The results of the noise- and sensitivity studies show that RasClic could be used as a low-frequency seismograph to monitor the 'earth hum'. There is evidence that the 1/f noise is to a large part due to temperature fluctuations; a system of T sensors is set up to eliminate this noise contribution. Further work needs to be done on the laser + beam expander diffraction plate pixel image sensor The RasClic vacuum tube in the TT1 tunnel at CERN. Recently the length increased from 91 to 140 m. Diffraction plate: transparant ring with inner/outer diameter of 80/100 mm Typical diffraction pattern seen by pixel image sensor (Allied Vision Technologies Pike F100B, 500 x 500 pixels, pitch 7.4 μm.) A position resolution of 20 nm is reached λ The main practical limitation for increased sensitivity at low frequency by extending RasClic to an ideal 20 km is the need for a long vacuum tube. The relatively cheap laser, diffraction plate and pixel sensor can work in principle at any distance, provided they are well coupled to the earth's crust individually. An interesting application of RasClic is as an instrument to monitor the slow deformation of the earth's crust across a fault line. Noise spectrum

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Transcript of RasClic: A long-baseline 3-point alignment system for Linear Accelerators H. Manaud Durand, J-P....

RasClic: A long-baseline 3-point alignment system for Linear AcceleratorsH. Manaud Durand, J-P. Quesnel, T. Touzé

CERN TS-SU, Geneva, Switzerland

Harry van der Graaf, Henk Groenstege, Elmar Reinhold, Geert Hanraads Nikhef, Amsterdam, The Netherlands

Mark Beker, Marc Kea, Hidde WestraNikhef/Delft University of Technology, The Netherlands

Rogier van der GeerNikhef/University of Leiden, The Netherlands

Taylan TozgortoUniversity of Amsterdam, The Netherlands

contact: [email protected]

RasClic is a new optical alignment system for large objects like linear accelerators, based on the RASNIK alignment system*. The system is a 3-point straightness monitor consisting of a monochromatic light source, a diffraction plate and a pixel image sensor. By monitoring the position of a diffraction pattern on the image sensor, a measure for the relative positions of the three components is obtained. It has been shown that such a system can meet the required alignment tolerances for use as an alignment system for the Compact Linear Collider (CLIC).

* [1] H. Dekker, H. van der Graaf, H. Groenstege, F. Linde, S. Sman, R. Steensma, B. Jongkind, A. Smeulders: The RASNIK/CCD 3-Dimensional Alignment System Proceedings of the 3rd International Workshop on Accelerator Alignment, (IWAA 1993), 28 Sept - 1 Oct 1993, Annecy, France

f x sx, y s

yF Ï‰

x, Ï‰

yei Ï‰

xsxÏ‰

ysy

Linearity tests were performed by varying a force on the diffraction plate holder of up to 50 N in the vertical direction. These tests show an excellent position resolution and linearity.

Noise behavior of an ideal RasClic compared to the STS-1 and STS-2 seismographs used by the Royal Dutch Institute for Meteorology (KNMI) [13]. The NHNM and NLNM envelopes are theNew High- and New Low Noise Models, respectively. These are models for the background noise in seismic measurements due to actual movements in the Earth's crust, during periods of high and low seismic activity, respectively.

Laser fiber-optic coupling system, eliminating drift in laser beam position

RasClic as a SeismographThe results of the noise- and sensitivity studies show that RasClic could be used as a low-frequency seismographto monitor the 'earth hum'.There is evidence that the 1/f noise is to a large part due to temperature fluctuations; a system of T sensors is set up to eliminate this noise contribution. Further work needs to be done on the resolution.

laser +beam expander

diffractionplate

pixel imagesensor

The RasClic vacuum tube in the TT1 tunnel at CERN. Recently the length increased from 91 to 140 m.

Diffraction plate: transparant ring with inner/outer diameter of 80/100 mm

Typical diffraction pattern seen by pixel image sensor (Allied Vision TechnologiesPike F100B,500 x 500 pixels,pitch 7.4 μm.)A position resolution of 20 nm is reached

The main practical limitation for increased sensitivity at low frequency by extending RasClic to an ideal 20 km is the need for a long vacuum tube.The relatively cheap laser, diffraction plate and pixel sensor can work in principle at any distance, provided they are well coupled to the earth's crust individually.An interesting application of RasClic is as an instrument to monitor the slow deformation of the earth's crust across a fault line.

Noise spectrum