Sep 25 – 29, 2006
Valencia, Spain
Europe/Zurich timezone

: Distributed low voltage power supply system for front end electronics of the TRT detector in ATLAS experiment

Sep 27, 2006, 3:05 PM
Valencia, Spain

Valencia, Spain

IFIC – Instituto de Fisica Corpuscular Edificio Institutos de Investgación Apartado de Correos 22085 E-46071 València SPAIN


Zbigniew Hajduk (Institute of Nuclear Physics PAN - Cracow, Poland and CERN Geneva)


We present a low voltage power supply system which has to deliver to the front end electronics of the ATLAS TRT detector ca. 24 kW of electrical power over the distance of 40-50 m (which adds another 24 kW). The system has to operate in magnetic field and under radiation environment of the LHC experimental cavern. The system has ~ 3000 individual channels which are all monitored and controlled (voltage and current measurement). The hardware solutions are described as well as the system control software.


Modern, highly integrated front end electronics of the experimental physics profits
from the technological progress in the field of modern electronics. Higher the
functional density of custom designed chips, higher the power consumed. The space
constraints in design of the collider experiment detectors create severe problems
with the power delivery to the front end (to say nothing about evacuation of this
power when converted to heat).
Amount of heavy material – copper – in cables is another negative aspect of the
supplying harnesses for electronics (both economical and affecting the detector
The detectors and its electronics will have to withstand also the high radiation
level produced by proton-proton collisions at LHC. Peripheral system, those like
power supply have to be radiation tolerant as the minimum. The ATLAS configuration of
magnets adds another aggressive factor – magnetic field – which has to be tolerated
by the power supply systems. This concern all electronics located in the experimental
ATLAS TRT is a straw detector with > 400000 individual channels. Front end
electronics located on the detector surrounding the interaction point consumes power
of ~ 24 kW and another 24 kW is dissipated in cables and regulators.
System consists of three basic parts :
1. Control unit and AC-DC converters located in the control room delivering 380 V DC
to 2/. (distance ~70 m)
2. DC-DC converters located on the supporting structure within experimental cavern
serving as bulk power supplies delivering voltages in 2-8 V DC range. (distance ~ 40 m)
3. Control , monitoring and regulating boards located within the volume of ATLAS
setup, supplying individual loads located on the detector (distance ~ 12 m)
The parts 1 and 2 are commercially available units produced by WIENER. Control unit
and AC-DC converter are not resistant to either radiation nor magnetic field thus
stay in friendly environment of the control room.
Part 3 consists of custom designed boards where by means of the regulators is
realized distribution (or fan-out) function to individual loads. The components used
are special design radiation hard regulators and radiation tolerant industrial IC and
The regulators can be disabled/enabled allowing for switch off/on of every channel.
The output voltage can be adjusted in range of ~ 1.5 V to compensate for possible
changes in necessary voltage due to radiation aging of front end chips. This is done
with help of radiation hard DAC’ located in a custom design chips.
The control of the board is performed via ELMB (Embedded Local Monitoring Board)
which is interfaced to the industrial SCADA system PVSSII. Some additional piece of
software has been designed for performance optimization and ease of digital control
of the DAC’s.
64 channels ADC on the ELMB board allows for current and voltage measurement of the
individual channels. Whole software has been embedded into CERN FrameWork (extension
to PVSSII) to allow for use of CERN-specific functions.
Functionalities description and conclusions from running experience will be given.

Primary author

Zbigniew Hajduk (Institute of Nuclear Physics PAN - Cracow, Poland and CERN Geneva)

Presentation materials