D. Lawrence

The GlueX central drift chamber: Design and performance

Tests and studies concerning the design and performance of the GlueX Central Drift Chamber (CDC) are presented. A full-scale prototype was built to test and steer the mechanical and electronic design. Small scale prototypes were constructed to test for sagging and to do timing and resolution studies of the detector. These studies were used to choose the gas mixture and to program a Monte Carlo simulation that can predict the detector response in an external magnetic field. Particle identification and charge division possibilities were also investigated.

A measurement of the energy and timing resolution of the GlueX Forward Calorimeter using an electron beam

The performance of the GlueX Forward Calorimeter was studied using a small version of the detector and a variable energy electron beam derived from the Hall B tagger at Jefferson Lab. For electron energies from 110 MeV to 260 MeV, which are near the lower-limits of the design sensitivity, the fractional energy resolution was measured to range from 20% to 14%, which meets the design goals. The use of custom 250 MHz flash ADCs for readout allowed precise measurements of signal arrival times. The detector achieved timing resolutions of 0.38 ns for a single 100 mV pulse, which will allow timing discrimination of photon beam bunches and out-of-time background during the operation of the GlueX detector.

Multi-threaded Event Reconstruction with JANA

The C++ reconstruction framework JANA has been written to support the next generation of Nuclear Physics experiments at Jefferson Lab in anticipation of the 12GeV upgrade. The JANA framework was designed to allow multi-threaded event processing with a minimal impact on developers of reconstruction software. As we enter the multi-core (and soon many-core) era, thread-enabled code will become essential to utilizing the full processor power available without invoking the logistical overhead of managing many individual processes. Event-based reconstruction lends itself naturally to multi-threaded processing. Emphasis will be placed on the multi-threading features of the framework. Test results of the scaling of event processing rates with number of threads are presented.

Jefferson Lab Data Acquisition Run Control System

A general overview of the Jefferson Lab data acquisition run control system is presented. This run control system is designed to operate the configuration, control, and monitoring of all Jefferson Lab experiments. It controls data-taking activities by coordinating the operation of DAQ sub-systems, online software components and third-party software such as external slow control systems. The main, unique feature which sets this system apart from conventional systems is its incorporation of intelligent agent concepts. Intelligent agents are autonomous programs which interact with each other through certain protocols on a peer-to-peer level. In this case, the protocols and standards used come from the domain-independent Foundation for Intelligent Physical Agents (FIPA), and the implementation used is the Java Agent Development Framework (JADE). A lightweight, XML/RDF-based language was developed to standardize the description of the run control system for configuration purposes.

cMsg - a publish/subscribe package for real-time and online control systems

cMsg is a messaging system designed for use in realtime data acquisition and online controls systems, and includes support for C/C++ and Java clients. It is highly customizable and extensible, and includes a full-featured asynchronous publish/subscribe component as well as a synchronous peer-to-peer component. We first describe the publish/subscribe and peer-to-peer messaging paradigms, discuss their use in real-time and online systems, and describe the power and flexibility of the publish/subscribe paradigm. Next we describe the philosophy of the cMsg implementation and present some details and benchmarks. Finally, since the core of cMsg is written in pure Java, we discuss the suitability of Java for use in real-time and online systems

Measuring the charged pion polarizability in the γγ → π^{+} π^{-} reaction

This proposal presents our plan to make a precision measurement of the charged pion polarizability απ − βπ through measurements of γγ → π+π− cross sections using the GlueX detector in Hall D. The accuracy of the proposed measurement is estimated at 10%, with an absolute error in α−β of ±0.6× 10−4fm3. The charged pion polarizability ranks among the most important tests of low-energy QCD presently unresolved by experiment. A measurement of the pion polarizability tests fundamental symmetries in the intrinsic even-parity sector of QCD.

The ET system - high speed event transfer and distribution via shared memory and networks

The event transfer (ET) system manages and distributes high volume data as it is being produced in real time. After data creation and insertion into the system, other processes can retrieve the data based on selection criteria, possibly modify the data, then return the data to the system. A chain of processes can thus process the data sequentially. The ET system has fast, local operation based on shared memory and POSIX threads and mutexes. Event transfer may also occur transparently over the network to remote users. The ET system has been in use for several years and is easy to use as well as extremely robust. It is implemented in C on Solaris and Linux platforms with a client library for vxWorks and has been ported to Java (the Java version does not use shared memory).

EVIO — A lightweight object-oriented I/O package

The EVIO package implements I/O between disk and an in-memory hierarchical object tree. Tree nodes are either container nodes, holding other nodes, or leaf nodes, containing any amount of data of a single type (int64_t,..., int8_t, float, double, and string). Trees can easily be constructed using factory methods and stream operators; queried using STL-like algorithms, function object, etc; or modified using tree or node methods. The tree logically maps to XML, and utilities exist to transform between binary and ASCII XML formats. The binary representation is compact, I/O is simple and efficient, and endian conversions are handled automatically. EVIO will be used by the next generation of experiments at Jefferson Lab1.

cMsg — A publish/subscribe interprocess communication package and framework

Asynchronous publish/subscribe messaging is a simple but powerful interprocess communication technique that is widely used in industry. It is less widely used in the academic/research world, partly because commercial implementations are fairly expensive. cMsg is both a full-featured publish/subscribe package and a framework within which one can deploy multiply underlying communication packages. The underlying packages need not implement asynchronous publish/subscribe messaging. This framework feature allows one to unify all communications under a single, flexible API, and allows for integration of legacy communication packages. Performance is excellent, making cMsg suitable for use in controls applications as well as in high-speed data transfer applications. cMsg will be used extensively by the next generation of experiments at JLab.