1. The Control System for the ATLAS Pixel Detector
Kerstin Lantzsch,
CERN/Bergische Universität Wuppertal
Gentner Day,

2. The ATLAS Pixel Detector
evaporative Cooling System
88 Parallel Cooling Circuits/loops:
56 PCCs with 2 staves each
24 PCCs with 2 disk sectors each
8 PCCs for 272 optoboards
1744 detector modules
3 Barrel Layers
3 Disks per Endcap
272 Halfstaves/Disksectors
optical data transfer:
272 readout groups (Halfstaves/Disksectors)
80 million readout channels
length: 1.3 m,  34.4 cm, weight: ~4.4 kg
Kerstin Lantzsch, Gentner Day

3. Tasks of the Detector Control System
Control Integration of the Hardware into the DCS software and its control for the supply of the detector.
Monitoring and Archiving Supervising values which are relevant to the state of the detector, and archive them for later trouble shooting.
Operation Provide the tools for the operation of the detector by the shift crew.
Interlock Ensure the safety of the detector and personnel.
Kerstin Lantzsch, Gentner Day

4. Kerstin Lantzsch, Gentner Day 18.11.2009
Hardware
The DCS hardware supervises detector modules, the optoboards, the readout crates, and the environment. It consists of:
The power supply system
Monitoring units
The interlock system
Kerstin Lantzsch, Gentner Day

5. Kerstin Lantzsch, Gentner Day 18.11.2009
Software
PVSS II (by ETM, Eisenstadt, Austria) was selected by the LHC experiments' Joint Controls Project (JCOP) as a base for the individual control systems.
Pixel DCS is built of 3 software layers:
Frontend Integration Tools (FIT):
Establish communication to the hardware
Data structures follow hardware properties
System Integration Tool (SIT):
Mapping between hardware and detector
Initialises archiving of DCS data
Finite State Machine (FSM):
Overview and Operation of detector. Main shifter tool.
Protection routines
Tools are provided by JCOP framework and ATLAS DCS
Kerstin Lantzsch, Gentner Day

6. Kerstin Lantzsch, Gentner Day 18.11.2009
The FSM
„The FSM“ is a hierarchical structure of objects that behave like separate FSMs, they are described by states, transitions, and commands.
In the hierarchy, commands are propagated down to the children, states are propagated up.
A tool for creation of control systems on FSM basis is provided centrally: SMI++ (State Management Interface).
The FSM is a combination from smi++ and PVSS. While state and command propation are handled by smi processes, the generation of the device states and the execution of commands is pure PVSS.
While there are some central requirements, the items specific for subdetector operation must be implemented by the subdetectors.
ATLAS specific is the subdivision into state (operational mode) and status (health of the system)
Kerstin Lantzsch, Gentner Day

7. Kerstin Lantzsch, Gentner Day 18.11.2009
The Pixel FSM
The FSM tree for the Pixel detector is driven by its mechanical structure, and granularity of readout and services, while the states and commands are adapted for operational aspects specific to the pixel detector. This is driven by the readout group and its devices.
Additional layers of protection are in the form of software interlocks built into the FSM scripts, and perform automated actions to protect the detector, which can not be expected of the shifter.
Kerstin Lantzsch, Gentner Day

8. Kerstin Lantzsch, Gentner Day 18.11.2009
The Pixel FSM Tree
Subdetector
DAQ-Partition
Layer
Cooling
Readout / services
Device Units
Kerstin Lantzsch, Gentner Day

9. Kerstin Lantzsch, Gentner Day 18.11.2009
The Readout Group
The Readout group mainly consists of the 6/7 Detector Modules serviced by one Optoboard, as well as their common supply units.
The synchronization of commands is handled by a special Device Unit.
The Device Units are rather complex (e.g. Module state and status is depending on 6 parameters). The calculation of state and status is distributed over 17 processes („managers“) on 3 DCS-PCs.
These PVSS-based scripts are also responsible for software Interlocks in case of
high temperature,
critical current values,
problems in the cooling system.
Kerstin Lantzsch, Gentner Day

10. State Diagram of the Readout Group
The State of the readout group is determined by the state of the device units
Not all states can be reached by DCS actions. Most prominently READY can only be reached passively, after the DAQ sends the configuration to the modules.
Defined States allow for the independent operation of single components. The pixel specific states are well-proven to be adequate for operation.
Kerstin Lantzsch, Gentner Day

11. Kerstin Lantzsch, Gentner Day 18.11.2009
Detector Overview
Overview over all the Readout groups in one panel
Not all nodes must contribute to the parent‘s state (e.g. disabled due to hardware problems)
In STANDBY for „Beam“
Kerstin Lantzsch, Gentner Day

12. Kerstin Lantzsch, Gentner Day 18.11.2009
Summary and outlook
Work on the FSM had to cover the evolving requirements from moving from the 10% system test, to the final system in the pit which is the main interface for the operation of the detector.
In addition to providing software interlock, scripts are in place which handle the reaction to and interaction with external systems, mainly the cooling system, but also handling of beam related issues.
The handling of the DCS crates is integrated into the FSM, allowing for easier recovery in case of shutdowns.
Besides the work on the detector control system, I want to start looking into correlations between information from Pixel and the ATLAS Beam Conditions Monitor (BCM).
Kerstin Lantzsch, Gentner Day