ATLAS logo

Rasnik (copyright) is a wide range, high precision alignment monitoring system, developed at NIKHEF.

The basic idea is to create an image of a coded mask on a CMOS sensor by means of a lens. The mask is lit by infrared LEDs. A diffuser is used to minimize effects of imperfections of the light source. In this set up the relative position in X and Y direction is measured along the line mask, optical center of the lens and the CMOS sensor. Also (relative) rotation of the mask or the sensor can be measured. By calculating the actual image spot size and comparing this with the mask spot size, the position of the lens along the Z-axis can be calculated. Also the relative rotation around the X, Y and Z-axis of the mask in respect to the CMOS sensor can be calculated.
The standard video signal from the CMOS sensor is digitized by means of a frame grabber.
The system has a measurement range of several cm's with an absolute accuracy of less than 1 micron.

RasNik system

Note: The USA15Mux is also called TopMux


The history of Rasnik systems, click a picture to continue for details
In the test set-up for Clic, Rasnik and Rasdif systems are used. Rasnik uses the conventional coded mask and a central lens. Rasdif uses a laser and a diffraction plate in the middle. The systems share the sensor, which is read-out via USB. The light sources are switched under USB control.
RasClic lnk
and RasGap

Sensiflex is the commercial offspring of the Rasnik system. Instead of using the dedicated Atlas structure, commercial USB and Ethernet sensors are used. Sensiflex has a collaboration agreement with Nikhef.
RasGap uses the Sensiflex hardware. It monitors the dilatation joint between the old and new part of the Nikhef building.
sensiflex logo/link
RasNik system
Up to eight RasCams can be connected (RJ45) to the Rasmux. There are 8 drivers for RasLeds, each having two output connectors (RJ11). Dimensions: 80 * 225 * ~45 mm. Control goes through the COM-port. Several stages of multiplexers are used to create a system of almost 6000 channels. From here you find the most complete description of the system.
ATLAS prototype system Up to eight RasCams can be connected (RJ45) and 12 RasLeds (RJ11). Control from LPT port via MasterBrico. RasMux proto
Before ATLAS The so-called demo kit. A scalable system, up to 32 channels (obsolete). Used to select different video channels and for testing various components.
obsolete mux
L3 alignment
The alignment system for L3 used four-quadrant diodes. It was used to monitor the sag within the individual detectors of app. 6 m long and the relative positions of three layers of muon detectors. The system shown here monitored the position of the end-caps with respect to the barrel detector. The lightpath wend through a 60 cm thick steel door which was part of the magnetic bending system.

No online

or you can go to :

You can mail suggestions for this page to: Henk Groenstege.

updated: february 2012