The ALICE Experiment Control System F. Carena / CERN-PH

1. The ALICE Experiment Control SystemF. Carena / CERN-PH

2. Introduction • ALICE (A Large Ion Collider Experiment) is the heavy-ion experiment being prepared for the Large Hadron Collider (LHC) at CERN

3. Introduction • ALICE consists of many particle detectors that can be operated: • All together to collect experimental data • As standalone, independent objects • In the present test and commissioning phase • In the future, final setup for calibration and test purposes • Running the experiment implies performing a set of activities on the detectors. These activities belong to different domains: • Detector Control System (DCS) • Data Acquisition (DAQ) • Trigger system (TRG) • High Level Trigger (HLT) • Every domain of activities requires some form of control • In ALICE independent ‘online systems’ have been developed to control the different domains

4. Introduction • The existing, independent ‘online systems’ • Operate with all the detectors • Allow partitioning (partitioning is the capability to concurrently operate groups of ALICE detectors) • The Experiment Control System (ECS) must coordinate the operations controlled by the ‘online systems’ for every detector in every partition • The ECS is a layer of software on top of the existing ‘online systems’. It gets status information from the ‘online systems’ and sends commands to them through interfaces based on Finite State Machines (FSM) • Access control mechanisms in the interfaces manage the ECS rights • ‘online systems’ under the ECS control • ‘online systems’ operated as independent systems

5. Partitions • A partition is a group of detectors identified by a name and defined by: • A list of ’assigned’ detectors. It contains the names of the detectors that can beactive in the partition • A list of ‘excluded’ detectors. It contains the names of the detectors that are assigned to the partition but are not active (active in another partition, operated in standalone mode, or because of explicit operator request) • Two types of operations are possible within a partition: • Global operations involving all the active detectors • Individual detector operations involving one single detector • Individual detector operations can be concurrently performed within a partition (e.g. parallel calibration procedures of different detectors) • Global and individual detector operation are mutually exclusive

6. Partitions DCS_1 DCS_2 DAQ_RC DCS_3 TPA • The handling of global operations in a partition requires the coordination of • the DCS for all the active detectors • the DAQ Run Control that steers the data acquisition for the partition • the Trigger Partition Agent (TPA) that connects the partition to the Central Trigger Processor (CTP)

7. Partitions DCS DAQ_RC LTU • The handling of an individual detector operation in a partition requires the coordination of • the DCS for one detector • the DAQ Run Control that steers the data acquisition for the detector • the Local Trigger Unit (LTU) associated to the detector

8. Standalone detectors DCS DAQ_RC LTU • A standalone detectors is a detector operated • out of all the defined partitions • totally disconnected from the Central Trigger Processor (CTP) • The handling of a standalone detector requires the coordination of • the DCS for the detector • the DAQ Run Control that steers the data acquisition for the detector • the Local Trigger Unit (LTU) associated to the detector

9. Components PCAHI Master Operator PCAHI PCA • The main components of the ECS are the Partition Control Agent (PCA), the Detector Control Agent (DCA), the PCA Human Interface (PCAHI), and the DCA Human Interface (DCAHI) • There is one PCA per partitions. • Handles global operations in the partition • Delegates individual detector operations to the DCAs • Handles the structure of the partition (inclusion/exclusion of detectors) • Accepts commands from one PCAHI at a time

10. Components PCAHI Master Operator DCAHI DCAHI Master Operator DCAHI PCA DCA DCA • There is one DCA per detector • When the detector is in standalone mode • Handles standalone operations • Accepts commands from a DCAHI at atime • When the detector is active in a partition • Handles individual detector operations within the partition • Accepts commands from the PCA only

11. DCA Human Interface

12. PCA Human Interface

13. Architecture • Example of architecture with 3 detectors (SDD, SPD, and SSD) • The SDD detector is operated in standalone mode • SPD and SSD are active in a partition called ITS

14. Interfaces • The components of the ECS get status information from the ‘online systems and send commands to them through interfaces based on Finite State Machines (FSM) • The FSM package used for these interfaces is SMI++ • http://www.cern.ch/smi • The interfaces also contain access control mechanisms that allow to control the rights granted to the ECS. The ‘online systems’ can be under the control of the ECS or be operated as independent systems: in this case the ECS get status information but does not send commands

15. ECS/DCS interface

16. ECS/TRG interface

17. ECS/DAQ, ECS/HLT interfaces • The interface between the ECS and the DAQ is made of SMI objects representing Run Control processes • An RC process per detector. Every RC process steers the data acquisition for a given detector and for that detector only • An RC process per partition to steer the data acquisition for the whole partition with data produced by all the active detectors • The ECS gets status information through a single SMI object representing the HLT‘online system’ as a whole.

18. ITS combined test • In October 2004 the ECS has been used to control the combined test of the ALICE Inner Tracking System consisting of • 3 detectors • Silicon Drift Detector (SDD) • Silicon Pixel Detector (SPD) • Silicon Strip Detector (SSD) • Trigger System • 3 LTUs • Special version of the TPA • DAQ System • 4 independent data acquisitions • Dummy DCS system for the 3 detectors

19. ITS test setup SDD SPD SSD L D C L D C L D C Fast Ethernet CONTROL G D C SDD-LTU SPD-LTU SSD-LTU TPA D D L D D L D D L DAQ runControl processes ECS processes (PCA+DCAs) Local disks

20. Results • All the possible modes of operation were successfully tested • 3 detectors in standalone mode • Any combination of 2 detectors running together and the 3rd one in standalone mode • 3 detectors running together • Switching from a mode of operation to another was • Fast (a few seconds) • Totally transparent for the DAQ and the TRG ‘online systems’

21. Conclusion • The ECS has been intensively developed during the last 18 months • The architecture and the interfaces have been implemented and successfully tested during the ITS combined test beam • Some developments are still needed • Several detectors have not yet implemented a DCS based on FSM and therefore the DCS states are not yet included in the ECS • Some detectors have not yet developed their calibration procedures • Some information like the definition of the Trigger classes is not available yet (temporary definition used for the time being) • The above issues will be included as soon as available. The ECS architecture has been proved to be solid and flexible enough to include all the future extensions.