September 28, 2015 to October 2, 2015
Europe/Zurich timezone

Preparing the hardware of the CMS Electromagnetic Calorimeter control and safety systems for LHC Run 2

Sep 30, 2015, 5:01 PM
Hall of Civil Engineering (Lisbon)

Hall of Civil Engineering


IST (Instituto Superior Técnico ) Alameda Campus Av. Rovisco Pais, 1 1049-001 Lisboa Portugal
Poster Systems Poster


Oliver Holme (ETH Zurich (CH))


The Detector Control System (DCS) of the CMS Electromagnetic Calorimeter (ECAL) has undergone significant improvements during the first LHC Long Shutdown (LS1). Based on the experience acquired during the first period of physics data taking of the LHC, several hardware projects were carried out to improve data accuracy, to minimise the impact of failures and to extend remote control possibilities in order to accelerate recovery from problematic situations. This paper outlines the hardware of the CMS ECAL DCS and safety systems and explains in detail the requirements, design and commissioning of the new hardware projects.


The CMS ECAL DCS consists of the following dedicated hardware systems to monitor the environmental conditions in the detector volume:

  • Precision temperature monitoring based on ELMBs (Embedded Local
    Monitor Boards)
  • Humidity monitoring based on PIC microcontrollers

In addition, interfaces to other hardware systems are available to provide both monitoring and control of:

  • Low voltage power supplies based on CAEN and Wiener commercial
  • High voltage power supplies based on CAEN commercial
  • Safety systems based on Siemens PLCs

The upgrade projects to be described in this paper are the following:

  1. A new microcontroller based relative humidity readout system
    which overcomes issues imposed by long cable lengths, previously
    limiting the readout range to 60 - 80%. The new PIC microcontroller
    based hardware design extends this range to 10 - 80%. The MODBUS
    communication protocol was chosen to ease the integration with the
    existing control system software. Commercial RS485-to-Ethernet
    adapters are used to allow remote monitoring using MODBUS over TCP.

  2. A system for remotely rebooting commercial power supplies from
    CAEN. These power supplies occasionally need rebooting in order to
    exit a problematic situation. Previously this involved an
    intervention at the CMS experiment site, which could take around one
    hour if no expert was on site at the time. The power supplies can be
    rebooted via a digital signal to an input on the mainframe front
    panel. A custom hardware solution, based on the Arduino platform,
    was designed to generate the necessary digital signals to trigger
    the mainframe reboot. To facilitate the integration into the
    controls software, the MODBUS over TCP protocol was implemented in
    the microcontroller.

  3. An improved power distribution system was designed for the CMS
    ECAL precision temperature monitoring system. This upgrade was
    motivated by observations that a single readout board failure could
    degrade the whole monitoring system. To overcome this issue, a new
    power distribution with greater granularity and individually
    switched power lines was designed. In addition, the ability to
    switch individual power lines is advantageous for locating and
    isolating a fault.

These systems are fully tested, commissioned and integrated in the CMS ECAL DCS.

Primary author

Oliver Holme (ETH Zurich (CH))


Diogo Raphael Da Silva Di Calafiori (ETH Zurich (CH)) Dragoslav Jovanovic (Vinča Institute of Nuclear Sciences (RS)) Guenther Dissertori (ETH Zurich (CH)) Lubomir Djambazov (ETH Zurich (CH)) Peter Adzic (Vinča Institute of Nuclear Sciences (RS)) Predrag Cirkovic (Vinča Institute of Nuclear Sciences (RS)) Serguei Zelepukin (ETH Zurich (CH) and University of Wisconsin (US)) Werner Lustermann (ETH Zurich (CH))

Presentation materials