Speaker
Ewald Effinger
(CERN)
Description
The beam loss monitoring (BLM) system is one of the most important elements for the
protection of the Large Hadron Collider (LHC). It aims to protect the
superconducting magnets from quenches and the machine components from damages,
caused by beam losses. The losses are measured with ionization chambers and
secondary emission monitors at likely loss locations. About 4000 monitors will be
placed along the LHC mounted at the outside of the cryostats. The detectors produce
a current proportional to the impacting secondary particle flux.
The acquisition cards are placed near the detectors and are exposed to particle
irradiation. During the design process of the acquisition cards several irradiation
tests have been carried out to verify the radiation tolerance of the chosen
components.
The large variations of the quench levels with the beam energy and the particle
loss duration, require the acquisition and digitalisation of the detector currents
over eight orders of magnitude. The high dynamic range is covered by a current to
frequency converter (CFC), which measures currents between 10 pA and 1 mA. An
additional ADC measures the output voltage of the CFC to improve the data
acquisition cards resolution.
The signals of eight detectors are digitalised on one acquisition card. The data,
together with card status information, are transferred to the processing card via
two optical links.
Author
Ewald Effinger
(CERN)
