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

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

2. Introduction (1) ALICE (A Large Ion Collider Experiment) is the heavy-ion experiment being prepared for the Large Hadron Collider (LHC) at CERN. ALICE consists of several particle detectors In the final setup the detectors will operate all together In the present development phase the detectors are operated in ‘standalone mode’ The ‘standalone mode’ will also be required during the operational phase to perform calibration procedures on individual detectors

3. Introduction (2) • Running an experiment implies a set of activities on the detectors.In ALICE these activities are grouped into four Activity Domains: • Detector Control System (DCS) • Data Acquisition (DAQ) • Trigger (TRG) • High Level Trigger (HLT) • Activity Domains require coordination and control performed by control systems called ‘online systems’ • Common features of the ‘online systems’: • Interact with all the detectors • Allow ‘partitioning’ • Are independent from other ‘online systems’ • Accept commands issued by an external operator • Roles of the ECS • Provide a unified view of the experiment • Permit independent concurrent activities on group of detectors • Coordinate the operations of the ‘online systems’

4. Requirements • Handling of experiment partitions • A partition is a collection of detectors operated together • A detector can belong to many partitions, but is active in only one • The ECS handles the access conflicts • Coordination of the Activity Domains • Every activity domain is controlled by its ‘online system’ • ‘online systems’ are independent • The ECS • Coordinates and synchronizes the activities in every partition • Interacts with all the ‘online systems’ • Coordination of calibration and configuration procedures • Detectors require calibration and configuration procedures • These procedures are detector dependent, not partition dependent • The ECS allows concurrent calibration and configuration procedures • Coordination of ALICE activities with LHC status • The ECS steers the running of ALICE according to the LHC status

5. Architecture (1) ECS DCS TRG DAQ HLT • The ECS is a layer of software on top of the ‘online systems’ controlling the Activity Domains • The integration of the four ‘online systems’ with the ECS is based on domain dependent interfaces

6. Architecture (2) • The ECS • Gets information from the ‘online systems’ • Sends coordinated commands to the ‘online systems’ • The ‘online systems’ • Execute the received commands • Can also be operated in ‘manual mode’ by experts • The interfaces between the ECS and the ‘online systems’ are based on Finite State Machines (FSMs) • The implementation of FSMs chosen in ALICE is the SMI++ package

7. ECS components • The major software components of the ECS are: • The Partition Control Agent (PCA)Control of several detectors • The Detector Control Agent (DCA)Control of one detector in standalone mode • The ECS database (ECSDB) • The PCA Human Interface (PCAHI) • The DCA Human Interface (DCAHI) • The ECS database Human Interface (ECSHI)

8. PCA and PCAHI PCA There is one PCA per partition It is based on FSMs Interacts with the ‘online systems’ through FSMs Controls the running of a partition as a whole Coordinates calibration and configuration procedures Provides information to operators watching the partition Accepts commands from one operator (partition master operator) PCAHI Many PCAHI can be associated to a PCA and provide information to operators Only one PCAHI can get the mastership over the PCA. The operator using it (Partition master operator) can send commands to the PCA It is based on Tcl/Tk PCAHI Master Operator PCAHI PCA

9. DCA and DCAHI DCA There is one DCA per detector It is based on FSMs Interacts with the ‘online systems’ through FSMs Controls the running of a detector in standalone mode Provides information to operators watching the detector Accepts commands from a PCA or an operator (detector master operator) DCAHI Many DCAHI can be associated to a DCA and show information to operators Only one DCAHI can get mastership over a DCA not controlled by a PCA. The operator using it (detector master operator) can send commands to the DCA It is based on Tcl/Tk PCAHI Master Operator DCAHI DCAHI Master Operator DCAHI PCA DCA DCA

10. ECS DB and ECSHI ECS DB For every partition it gives: List of assigned detectors Status (active/inactive) of every detector Status (running/not running) of its PCA Process ID of the PCAHI having the mastership over the PCA For every detector it gives: Status (running/not running) of its DCA The partition name (if the detector is active in a partition) Process ID of the DCAHI having the mastership over the DCA ECSHI Gives access to the ECS database Allows the definition of new partitions Gives an overall view of the experiment Shows detail about detectors and their usage ECSHI ECS DB

11. Interfaces (1) • The interfaces between the ECS and the ‘online systems’ have the following common features: • Are based on FSMs • Offer a simplified model of the activity domains • Hide the complexity of the real objects • Associate an access control mechanism to every object in the interface • The current interface definitions are the following: • DCS: one object per detector representing the detector from the hardware point of view • DAQ: objects representing RunControl processes • TRG: one object per detector representing the Local Trigger Unit (LTU) and one object for every partition (Trigger Partition Agent) • HLT: a single object representing the HLT as a whole

12. Interfaces (2) HLT DAQ ECSHI RC_a RC_b HLT RC_{a+b} ECS DB PCA_{a+b} DCA_a DCA_b DCAHI DCAHI PCAHI Master Operator TPA_{a+b} DCS_a DCS_b LTU_a LTU_b DCS TRG

13. DCA operations (1) The smallest entity that can be controlled by an operator is a detector in standalone mode An operator controlling a detector can: Issue all the commands accepted by its DCA The list of valid commands is different from one detector to another The list of commands will grow during the lifetime of the experiment The list of commands depends on the state of objects defined in the interfaces with the ‘online systems’

14. DCA operations (2) • Send manual commands to the ‘online systems’ controlling the Activity Domains • This possibility serves mainly for debugging purposes

15. DCA operations (3) • Reduce or extend control rights using the access control mechanism contained in the interfaces with the ‘online systems’ • The operator uses this possibility to avoid access conflicts when experts needs to use directly the ‘online systems’

16. PCA operations (1) • The largest entity that can be controlled by an operator is a partition • An operator controlling a partition can: • Run the partition as a whole

17. PCA operations (2) • Perform calibrations and tests on individual detectors when the partition is not running as a whole

18. PCA operations (3) • Exclude detectors from the partition or re-include them in the partition

19. PCA operations (4) • Send manual commands to the ‘online systems’ for debugging purposes

20. PCA operations (5) • Reduce or extend operator control rights using the access control mechanism contained in the interfaces with the ‘online systems’

21. Implementation status (1) • The implementation of the major components of the ECS is well advanced • A DCA prototype developed for the HMPID detector was successfully used during standalone detector tests in October 2003 and in July-August 2004 • It interacts with three ‘online systems’ (DCS, DAQ, and TRG) with DCS running on Windows PCs and with DAQ, TRG and ECS running on Linux PCs • A first version of the PCA exists and will be used for the combined tests of the Inner Tracking System (ITS) in October 2004 • The ITS is made of three detectors (SDD, SPD, and SSD) • The developed prototype interacts with DCS, DAQ, and TRG • The DCAHI and the PCAHI have been developed as well

22. Implementation status (2) • A first version of the ECS database has been designed and implemented using MySQL • An ECSHI exists and provides a basic set of functions

23. Summary and conclusions • The ALICE ECS provides: • A unified view of the experiment and a central point where all the different aspects of the experiment are initiated and controlled • The possibility to operate concurrently parts of the experiment (partitions) • The possibility to operate detectors in standalone mode • The experience acquired during beam tests proves that the adopted architecture satisfies the functional requirements and allows the parallel development of independent ‘online systems’ controlling the Activity Domains • The adopted technologies make the ECS extremely flexible • During the detector tests and commissioning phase the ECS will be continuously adapted to new requirements • During the operational phase of ALICE the ECS will continue its evolution to include more and more automatic procedures