The LUCID II detector 
The LUCID II detectors surrounds the beampipe on both sides of the interaction point at a distance of 17 m.
The LUCID system consists of three different detectors. The first one consists of 12 + 12 Hamamatsu R760
photomulipliers located in four groups around the beampipe. The center of the photomultipliers is at a distance
of 125 mm from the beamline. Charged particles going through the radiation hard quartz window of the photomultipliers
can produce Cherenkov light that is detected by the photomultipliers.
The second detector consists of 4 + 4 modified R760 photomultipliers that have a thin ring shaped layer
of aluminium deposited between the quartz window and the photocathode. The center hole of this ring has
a diameter of 7 mm which can be compared to the 10 mm diameter of the photocathode and the layer thus
reduces the acceptance of these photomultipliers with a factor of 2.
The third detector consists of 4 + 4 four meter long bundles of optical quartz fibers that run along the beampipe.
Exach bundle consists of 37 optical fibers each with a 0.8 mm quartz core. Charged particles passing through the fibers will produce Cherenkov light that is recorded by photomultipliers situated 1.2 m away from the beamline.
The detector is used to measure luminosity, either by counting pulses above a threshold or by counting the
charge of the pulses by using new integrating electronics. The stability of the detector respons is monitored by
three different calibration systems. The first uses light from LEDs that is monitored by PIN diodes.
The second uses light from a laser system and the third uses Cherenkov light produced by weak Bi-207 sources.
The Bi-207 sources give out monoenergetic electrons from internal conversion that have an energy above the cherenkov threshold in quartz.
Assembly and installation of LUCID:
Photos ,
Video .
The detector is used to measure luminosity, either by counting pulses above a threshold or by counting the charge of the pulses by using new integrating electronics. The stability of the detector respons is monitored by three different calibration systems. The first uses light from LEDs that is monitored by PIN diodes. The second uses light from a laser system and the third uses Cherenkov light produced by weak Bi-207 sources. The Bi-207 sources give out monoenergetic electrons from internal conversion that have an energy above the cherenkov threshold in quartz.
