1. Detector Safety System overview DSS is a PLC based system designed to protect ATLAS detector from damages. Front end (hardware) 2 redundant PLC ~700 input signals (sensors) ~400 actuators (actions) accommodated in 7 racks underground and on surface. ~700 alarms Alarm is a logical element, which links inputs signals with DSS actions. Back end (software) PVSS based application, provides human-machine interface 2 active workstations + 2 hot swap workstations DSS includes proprietary sensors temperature, pressure, water leak etc. and inputs from external systems gas systems, electricity, cooling, ATASL subsystems, smoke detection, SNIFFERS, gas detection All this equipment need to be maintained and tested. New detecting systems and sensors being added regularly, following detectors requirements. Alarm-action logic must be kept up-to-date with detectors.

2. LS1 DSS maintenance and consolidation Alarm-action matrix (DSS logic) has been reviewed together with detectors and modified to better satisfy ATLAS detectors safety requirements. Implementation is nearly finished (some cross checks and cleaning still to be done). Next step – comprehensive test of DSS matrix, will be done later on this year, when all detectors are closer to running conditions. Hardware maintenance and consolidation of DSS hardware is ongoing Local UPS and batteries replaced, DSUs powering scheme improved, adding redundancy to 230V power supply reduces risk of detector shutdown due to UPS failure Consolidation of various sensors temperature sensors, water detecting in racks and caverns, ventilation, etc. Implementation of new systems and sensors IBL CO2 cooling + water leak, leak detection in TileCal Sc garages, new racks interlock, temperature sensors etc. Test of DSS Alarm-action matrix Propagation of signals from external systems to DSS DSS sensors DSS actuators

3. Atlas safety systems External to DSS safety systems are linked to DSS providing input signals Atlas proprietary systems, maintained by ATALS Gate monitors – HW maintenance + PC and software upgrade Seismic sensors - HW maintenance + PC and software upgrade Water leak detection - in racks, UX15, USA15 caverns, to be implemented in US15 and SDX1 External safety systems, maintained by GS Gas detection Central has been upgraded recently New FG gas detection system under development by GS Smoke detection, environment and in racks Install sensors in new racks in USA15 and UX15 SNIFFERS (maintained by GS and ATLAS together) PLC firmware upgrade (GS) modules maintenance (ATLAS) pipes cleaning (ATLAS) Access systems software upgrade new access doors installed in sectors 11 and 15

4. Cabling activity A lot of new cables being installed at LS1 Currently team of 7 people are working on cable installation Cabling activity includes: Communicating with detectors Defining the cable routing Estimation/calculation of cable length Preparing labels and entering info to DB Organization of installation, cable trays Cabling team managing Cabling done, ongoing or planned for the systems: nSQP (new PIXEL services) IBL detector IBL CO2 cooling New evaporative cooling (thermo syphon) system New optical cables for MUON detector New MEDIPIX detectors BCAM Beam pipe services and motor movement Detector cooling DSS Various single cables

5. Other activities Response to issues raised during LS1 period, like new flexible chains in sector 11 to install LAr optical fiber bundles and new cables; Tilecal Cs garages drain lines and leak detection, etc. SLIMOS activity (4 shifters) RPE activity TC RPE team was particularly important at detector opening OPM and other activity support