T. Pelaia

The EPICS based virtual accelerator-concept and implementation

A virtual accelerator (VA) concept and an implementation founded on TRACE3D and PARMILA codes are presented. This virtual accelerator is suitable for accelerators with a control system based on EPICS and consists of the EPICS portable channel access server (PCAS), the EPICS client providing communication between a simulation model and PCAS, and the simulation model itself. The virtual accelerators for the SNS linac and experience in using these VAs are discussed.

SNS global database use in application programming

A global relational database is being assembled to track accelerator components for the Spallation Neutron Source (SNS). As part of this activity, beamline element information is stored for use in high level application programs. A hierarchal accelerator framework is generated from the database and used for initialization of a Java based programming infrastructure. From within this framework input files for beam simulation codes can be generated using either live machine values or design values. The database also includes global coordinates for beamline element alignment, and magnet measurement data. An overview of the table schema and relationships to tables used in other parts of the project are discussed.

A modular on-line simulator for model reference control of charged particle beams

We have implemented a particle beam simulation engine based on modern software engineering principles with intent that it be a convenient model reference for high-level control applications. The simulator is an autonomous subsystem of the high-level application framework XAL currently under development for the Spallation Neutron Source (SNS). It supports multiple simulation techniques (i.e., single particle, multi-particle, envelope, etc.), automatically synchronizes with operating accelerator hardware, and also supports off-line design studies. Moreover, since it is implemented using modern techniques in the Java language, it is portable across operating platforms, is maintainable, and upgradeable.

Application programming structure and physics applications

The Spallation Neutron Source (SNS) is using a Java based hierarchal framework for application program development. The framework is designed to provide an accelerator physics programming interface to the accelerator, called XAL. Much of the underlying interface to the EPICS control system is hidden from the user. Use of this framework allows writing of general-purpose applications that can be applied to various parts of the accelerator. Also, since the accelerator structure is initiated from a database, introduction of new beamline devices or signal modifications are immediately available for all XAL applications. Direct scripting interfaces are available for both Jython and Matlab, for rapid prototyping uses. Initial applications such as orbit difference, orbit correction and a general purpose diagnostic tool have been developed and tested with the SNS front end. The overall framework is described, and example applications are shown.

Techniques for Measurement and Correction of the SNS Accumulator Ring Optics

The Spallation Neutron Source (SNS) Accumulator Ring will reach peak intensities of 1.5×1014protons/pulse through multi-turn charge-exchange injection. Accumulation of these unprecedented beam intensities must be accomplished while maintaining extremely low losses (less than 1 W/m). It is anticipated that the understanding and control of the ring optics will be important for achieving these low loss rates. We describe our plans for measuring and correcting the optical functions of the accumulator ring lattice.

The Spallation Neutron Source Beam Commissioning and Initial Operations

The Spallation Neutron Source (SNS) accelerator delivers a one mega-Watt beam to a mercury target to produce neutrons used for neutron scattering materials research. It delivers ~ 1 GeV protons in short (< 1 us) pulses at 60 Hz. At an average power of ~ one mega-Watt, it is the highest-powered pulsed proton accelerator. The accelerator includes the first use of superconducting RF acceleration for a pulsed protons at this energy. The storage ring used to create the short time structure has record peak particle per pulse intensity. Beam commissioning took place in a staged manner during the construction phase of SNS. After the construction, neutron production operations began within a few months, and one mega-Watt operation was achieved within three years. The methods used to commission the beam and the experiences during initial operation are discussed.

Status of various sns diagnostic systems

The spallation neutron source (SNS) accelerator systems are ramping up to deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. Enhancements or additions have been made to several instrument systems to support the ramp up in intensity, improve reliability, and/or add functionality. The beam current monitors now support increased rep rates, the Harp system now includes charge density calculations for the target, and a new system has been created to collect data for the beam accounting and present the data over the web and to the operator consoles. The majority of the SNS beam instruments are PC-based and their configuration files are now managed through the Oracle relational database. A new version for the wire scanner software was developed to add features to correlate the scan with beam loss, parking in the beam, and measuring the longitudinal beam current. This software is currently being tested. This paper also includes data from the selected instruments.