Operating principes
The calorimeter is used to perform a cross calibration of the cavity with a beam current around 1µA.
The main part of the calorimeter is a tungsten composite slug inserted on the beam axis for a well defined period Δt.
Energy deposited in the calorimeter : Ecal = Ebeam.Ibeam.Δt - Eloss where Ecal (Joules), Ebeam (MeV), Ibeam (µA), Δt (s)
The best accuracy on the measurement of the average beam current Ibeam involves that the energy lost in the calorimeter Eloss
must be small, i.e. the calorimeter must be designed in a way that
makes the energy lost by the slug by heat transfert and radiation must
be minimal.
The slug should be placed in vacuum, separated from the other components by low thermal conductivity materials (ceramics), and covered with gold to decrease the emissivity ; some of the other components wrapped with silver for the same reasons.
The calorimeter is designed for a beam energy 0.8 GeV < Ebeam < 11 GeV.
On the other hand, the Energy absorbed by the calorimeter is linked to
the change in temperature after a beam exposure (ΔT) and to the
specific heat of the slug (Cm) with the relation : ΔT.Cm = Ecal
As heat capacities are generally not know with a the precision required for this experiment, Cm must be measured (see the glossary and the calculation of the specific heat pages for more).
The calorimeter should be placed in the hall A as shown on the following pictures :
