Luminosity monitor
Luminosity monitor is destined for operative measurement of VEPP-4M
collider's luminosity by the process of single bremsstrahlung
Also working with the electron tagging system of the KEDR detector luminosity
monitor allows to identify events which are background ones for this system.
Luminosity monitor detects single bremsstrahlung event by registering the
photon emitted. Single bremsstrahlung photons are emitted at a narrow cone with
the angle 
along the colliding beams axis, so luminosity monitor
contists of two electromagnetic calorimeters, placed on both sides of the
interaction point at a distance greater than the size of the detector,
Fig.1.
Each electromagnetic calorimeter is a scintillation sandwich contisting of
4 identical blocks (Fig.2). A block is viewed by
4 photomultipliers (FEU-110)
and consists of 25 layers, each layer consists of a plate of plastic
scintillator 5mm thick and a lead plate 1mm thick. Each sandwich is viewed by
16 photomultipliers, total thickness of a sandwich is 19 radiation lengths.
The main background process for the process of single bremsstrahlung of the
colliding beams scattered of each other is the single bremsstrahlung of the
beams scattered by residual gas. Energy spectra of the photons emitted in the
primary and the background processes are almost the same, therefore the
background level is defined by direct measurement of the background process
with the beams separated.
Last modified on 23 April 2003