Electron beam dump
experiment covers the region of low masses and very low couplings, down to [epsilon]~[10.sup.-7].
Illig states that there is a "beam dump
" to absorb x-rays on the other side of the container, and that the accelerator is pulsed, so that it is off most of the time, reducing the shielding needed.
The transmitted beam, which travels through the open sectors of the chopper wheel, is incident on the test detector and the reflected beam is incident onto a beam dump
. The chopper wheel, thus, acts as an attenuator for radiation going to the test detector.
The limits on U boson searches from beam dump
experiments come from reanalysis  of a compete set of experiments performed at SLAC and Fermilab during the '80s and '90s to search for light Axion-like particles [12-14].
The unscattered part of the laser beam passes through the second window and into a beam dump
. The scattered portion also passes through the second window, but misses the beam dump
and is picked up by a photodetector.