[Paper Review] The ATLAS Tile Calorimeter Test Beam Monitoring Program

P. Adragna, A. Dotti+1 more|ArXiv.org|May 29, 2004

Particle Detector Development and Performance2 references3 citations

TL;DR

This paper presents the ATLAS Tile Calorimeter Test Beam Monitoring Program (PMP), an online monitoring system built on ROOT and ATLAS Online Software services to ensure real-time data quality and setup validation during test beam operations. The system uses event sampling, data unpacking, and real-time histogramming to monitor both TileCal and beam detector data, enabling rapid diagnostics and visualization through a modular, GUI-driven interface with signal-slot-based dynamic updates.

ABSTRACT

During 2003 test beam session for ATLAS Tile Calorimeter a monitoring program has been developed to ease the setup of correct running condition and the assessment of data quality. The program has been built using the Online Software services provided by the ATLAS Online Software group. The first part of this note contains a brief overview of these services followed by the full description of Tile Calorimeter monitoring program architecture and features. Performances and future upgrades are discussed in the final part of this note.

Motivation & Objective

• To develop a real-time monitoring system for the ATLAS Tile Calorimeter during test beam operations to ensure correct running conditions and data quality.
• To integrate both Tile Calorimeter and beam detector (Cerenkov counters, scintillators, wire chambers) data into a unified monitoring framework.
• To leverage ATLAS Online Software services—particularly the Event Monitoring Service—for efficient data sampling and distribution.
• To enable fast debugging and immediate visualization of data through a GUI-driven, event-by-event analysis pipeline.
• To lay the foundation for future expansion to monitor multiple detectors in combined test beam runs.

Proposed method

• The program is implemented in C++ using the ROOT framework, with data input sourced either from disk files or online via the Event Monitoring Service.
• Raw ATLAS-format events are unpacked through a hierarchical class structure (RawAtlasEvent → RODFragment) to extract detector-specific data.
• Unpacked data are stored in a memory-resident ROOT Tree, allowing efficient analysis without retaining raw data buffers.
• Histograms are filled in real time and displayed via a GUI presenter that uses ROOT’s signal-slot mechanism for dynamic, responsive updates.
• The system employs a three-layer architecture: Data Source (file/online input), Unpacking and Decode (event interpretation), and Presenter (GUI and histogram display).
• The GUI supports real-time histogram rebinning, resetting, and standard ROOT interactions (e.g., rescaling, fitting) through signal-slot connections.

Experimental results

Research questions

• RQ1 How can real-time monitoring of ATLAS Tile Calorimeter test beam data be achieved with minimal latency and high reliability?
• RQ2 What architectural patterns enable efficient decoupling of data unpacking from visualization in a high-throughput detector monitoring system?
• RQ3 How can a unified monitoring interface handle data from multiple detector subsystems (e.g., TileCal and beam detectors) simultaneously?
• RQ4 What performance bottlenecks exist in a single-threaded, event-driven monitoring pipeline, and how can they be mitigated?
• RQ5 To what extent can the monitoring framework be extended to support combined test beam operations with multiple detectors?

Key findings

• The monitoring program achieved a mean CPU load of 41% and average physical memory usage of 18% on a Pentium III 1GHz system with 256 MB RAM, indicating efficient resource utilization.
• Memory usage increased sharply at ~550 seconds due to GUI presenter initialization, which helped identify and resolve memory leaks during development.
• The system successfully enabled real-time event display showing energy deposition in TileCal modules, with cell heights proportional to deposited energy and spatial coordinates in η and depth (A, BC, D).
• The program was successfully extended during the September 2003 combined test beam to include MDT and SCT detectors using standard decoding routines, producing correlated histograms of muon and pion events.
• The signal-slot mechanism in ROOT enabled responsive, real-time histogram updates and interactive controls (e.g., rebinning, resetting) without performance degradation.
• Future migration to a client-server model is planned to decouple computation from visualization, improving performance under CPU load and enabling multi-detector, multi-run monitoring.