Instrumentation of the very forward region of a linear collider detector

The very forward region of a detector at a linear e/sup +/e/sup -/ collider is a particularly challenging area for instrumentation. In the TESLA detector, two calorimeters, BeamCal (Beam Calorimeter) and LumiCal (Luminosity Calorimeter) are planned. The BeamCal is positioned just adjacent to the beampipe. It will be hit by beamstrahlung remnants giving a deposition of several tens of TeV per bunch crossing. The distribution of this energy will be measured to assist in tuning the beams. Single high-energy electrons will be identified and measured. High-energy electron identification is particularly important to veto backgrounds to new particle searches. Several technological options for BeamCal are discussed. Monte Carlo simulations are presented for a diamond/tungsten sandwich structure and compared to results obtained for a heavy element crystal calorimeter. First, tests of sensors are described. The LumiCal will measure larger polar angles than the BeamCal. It will provide a high-precision (O(10/sup -4/)) luminosity measurement from Bhabha scattering. Monte Carlo simulations to optimize the shape and the structure of the calorimeter are presented.