Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
In recent years many changes have been made to the Advanced Photon Source (APS) linear accelerato... more In recent years many changes have been made to the Advanced Photon Source (APS) linear accelerator (linac) to support multiple tasks. The primary purpose of the linac is to provide beam to fill the APS storage ring, which is done using thermionic cathode rf guns. At the same time we provide support for research projects, including a new facility that will be used for future operator training and testing of injector components. With each task requiring a different lattice and timing configuration, while at the same time using common rf systems, the complexity of operations has increased significantly with even greater demands being made on reliability and performance. In addition, personnel safety and equipment protection concerns have become more complex. We approached these challenges by developing three new subsystems: a highly automated linac operation using APS's Procedure Execution Manager (PEM) software; a new interlock system based on programmable logic controllers; and an automated S-band rf switching system. In this paper, we discuss how these developments have improved the flexibility and reliability of the APS linac, and how we intend to conduct operator training and test new injector components while maintaining storage ring injections.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
The Advanced Photon Source uses two distinct control programs for orbit control and stability-a f... more The Advanced Photon Source uses two distinct control programs for orbit control and stability-a full-featured workstation-based program for orbit control (sddscontrollaw) and an EPICS-based system, the Real-Time Fast Feedback System (RTFS), to reduce orbit motion. The sddscontrollaw program has been ported to EPICS and moved from the UNIX environment to an EPICS IOC attached to the RTFS. This EPICS-based program uses the RTFS's reflective memory to gather beam position information and write corrector power supplies, thus avoiding variable network latencies. This allows the orbit control to run at a correction rate 50 times that of the workstation implementation, which virtually eliminates orbit motion caused by insertion device gap changes. Issues raised by the integration of orbit control into the real-time feedback system and performance improvements are discussed.
At the Advanced Photon Source (APS) most of the testing of minor operational software is done dur... more At the Advanced Photon Source (APS) most of the testing of minor operational software is done during accelerator studies time. For major software changes, such as the porting of the complex workstation-based orbit control software to an EPICS IOC, much of the testing was done "offline" on a test IOC. A configurable storage ring simulator was created in a workstation with corresponding control system records for correctors and orbit readbacks.
Use of SDDS, the Self-Describing Data Sets file protocol and toolkit, has been a great benefit to... more Use of SDDS, the Self-Describing Data Sets file protocol and toolkit, has been a great benefit to development of several accelerator simulation codes. However, the serial nature of SDDS was found to be a bottleneck for SDDScompliant simulation programs such as parallel elegant. A parallel version of SDDS would be expected to yield significant dividends for runs involving large numbers of simulation particles. In this paper, we present a parallel interface for reading and writing SDDS files. This interface is derived from serial SDDS with minimal changes, but defines semantics for parallel access and is tailored for high performance. The underlying parallel I/O is built on MPI-I/O. The performance of parallel SDDS and parallel HDF5 are studied and compared. Our tests indicate better scalability of parallel SDDS compared to HDF5. We see significant I/O performance improvement with this parallel SDDS interface. *
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
Self-Describing Data Sets (SDDS) and the corresponding SDDS tools have long been used at the Adva... more Self-Describing Data Sets (SDDS) and the corresponding SDDS tools have long been used at the Advanced Photon Source (APS) and other laboratories for data storage and analysis. Various programs in the toolkit have been added or improved recently. Support for the Mac OS X operating system has been added. Automated testing scripts are being used to reduce bugs prior to software upgrades. The Java version of the SDDS Toolkit has been used to integrate standard SDDS functions into MATLAB. The fitting of generic functions to SDDS data has been improved. Conversion of array data to column data has been added to allow analysis of array data with existing programs. The display of sddsplot movies by saving plots to files for rapid playback has been improved.
PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268), 2001
The program GENESIS has been widely used for the simulation of free-electron lasers (FELs). We ex... more The program GENESIS has been widely used for the simulation of free-electron lasers (FELs). We extended the capabilities of the program by making the code compliant with the Self-Describing Data Set file protocol, whose toolkit has been developed and used extensively at Argonne. We report the modifications made to GENESIS and demonstrate the benefits by presenting the results obtained by its application to two major FEL projects: Argonne's Low-Energy Undulator Test Line and the Linac Coherent Light Source at SLAC.
The BSP-100 beam position monitor (BPM) was com-missioned and installed at the Advanced Photon So... more The BSP-100 beam position monitor (BPM) was com-missioned and installed at the Advanced Photon Source (APS) in a fraction of the ring as an upgrade to the present turn-by-turn BPMs. Keeping the same rf front end of the present BPMs, the BSP-100 BPM adds a high-...
Temperature dependent Mossbauer effect, magnetization and transport measurements have been made f... more Temperature dependent Mossbauer effect, magnetization and transport measurements have been made for (LaMn_0.98 ^57Fe_0.02)_1-deltaO3 . Various techniques of synthesis (air, Ar, quenching, slow cooling) are used to tailor the cation defect concentration delta, and thus control the Mn^3+/ Mn^4+ ratio and carrier concentration. Mossbauer effect measurements show that Fe is near 3+ in all compounds. The crystal structure changes from
The magnetic transition temperature and the transport behavior of La_0.83 Sr_0.17 Mn_1-y ^57Fey O... more The magnetic transition temperature and the transport behavior of La_0.83 Sr_0.17 Mn_1-y ^57Fey O3 are systematically varied by substitution of Fe (y = 0, 0.01, 0.02, 0.05, 0.10) for Mn. Mossbauer effect measuresments show that Fe remains near 3+ for all concentrations and, therefore does not play a role in charge hopping, but does lead to an increase in the
The effect on magnetic and magnetoresistive behavior of substituting Fe magnetic impurities on th... more The effect on magnetic and magnetoresistive behavior of substituting Fe magnetic impurities on the Mn sublattice in La_1-xSr_xMn_1-y^57Fe_yO3 has been studied. Perovskites with x=0, 0.1, 0.2, 0.3 and y= 0.02, 0.05, 0.10 have been synthesized in air or Ar to control the cation defect concentration. Thermogravimetric measurements were used to obtain defect-free samples. The materials have been characterized by XRD, magnetic and magnetoresistance measurements. Local magnetic behavior is monitored by temperature dependent (15-320 K) Mossbauer Effect measurements. The mean field, the influence of spin- and charge-fluctuation and chemical disorder have been delineated. The Fe ion is /sim 3+ for all compositions. The effect of Fe antiferromagnetic superexchange coupling to the magnetic Mn sublattice on magnetic behavior, and the effect of magnetic order on quadrupolar coupling and Debye-Waller factor will be discussed.footnote Supported by DARPA ONR, the State of Illinois under HECA and US DOE-BES No. W-31-109-ENG-38
The electron accelerator simulation software elegant [1] is being parallelized in a multi-year ef... more The electron accelerator simulation software elegant [1] is being parallelized in a multi-year effort. Re-cent developments include parallelization of input/output (I/O), frequency map analysis, dynamic aperture search, and position-dependent momentum aperture determina-tion. Parallel frequency map, momentum aperture analy-sis, and dyanmic aperture search provide rapid turnaround for important determinants of storage ring performance. The development of parallel Self-Describing Data Sets file (SDDS) I/O based on MPI-IO made it possible for paral-lel elegant (Pelegant) to take advantage of parallel I/O. Compared with previous versions of Pelegant with serial I/O, the new version not only enhances the I/O throughput with good scalability but also provides a feasible way to run simulations with a very large number of particles (e.g., 1 billion particles) by eliminating the memory bottleneck on the master with serial I/O. Another benefit of using parallel I/O is reducing the communicati...
The Advanced Photon Source (APS) linear accelerator has two thermionic cathode rf guns and one ph... more The Advanced Photon Source (APS) linear accelerator has two thermionic cathode rf guns and one photocathode rf gun. The thermionic guns are used primarily for APS operations while the photocathode gun is used as a free-electron laser (FEL) driver. With each gun requiring a different lattice and timing configuration, the need to change quickly between guns puts great demands on the accelerator operators. Using the Procedure Execution Manager (PEM), a software environment for managing automated procedures, we have made start-up and switch-over of the linac systems both easier and more reliable. The PEM is a graphical user interface written in Tcl/Tk that permits the user to invoke "machine procedures" and control their execution. It allows construction of procedures in a hierarchical, parallel fashion, which makes for efficient execution and development. In this paper, we discuss the features and advantages of the PEM environment as well the specifics of our procedures for t...
The Advanced Photon Source (APS) linear accelerator (linac) utilizes two thermionic cathode rf gu... more The Advanced Photon Source (APS) linear accelerator (linac) utilizes two thermionic cathode rf guns and one photocathode rf gun. The thermionic guns are primarily for APS operations while the photocathode gun is used as a free-electron laser (FEL) driver. With each gun requiring a different lattice and timing configuration, the need to change quickly between guns and maintain the required equipment protection puts great demands on the Main Control Room (MCR) operators. This paper discusses how the APS staff has learned to deal with the frequent changes required by a newly upgraded equipment safety interlock system and how they have become familiar with the automated control system called [1, 2] Procedure Execution Manager (PEM). Our linac is controlled via the Experimental Physics and Industrial Control System (EPICS), but the lessons are applicable to any control system.
Large scale beam dynamics simulations can derive sig-nificant benefit from efficient implementati... more Large scale beam dynamics simulations can derive sig-nificant benefit from efficient implementation of general-purpose particle tracking on GPUs. We present the latest results of our work on accelerating Argonne National Lab's accelerator simulation code ELEGANT, using CUDA-enabled GPUs. We summarize the performance of beam-line elements ported to GPU, and discuss optimization techniques for some core collective effects kernels, in par-ticular our methods of avoiding costly thread contention. We also outline briefly our testing and code validation in-frastructure within ELEGANT as well as a new template meta-programming infrastructure for streamlining code de-velopment.
Efficient implementation of general purpose particle tracking on GPUs can result in significant p... more Efficient implementation of general purpose particle tracking on GPUs can result in significant performance benefits to large scale particle tracking and tracking-based accelerator optimization simulations. We present our work on accelerating Argonne National Lab's accelerator simulation code ELEGANT [1, 2] using CUDA-enabled GPUs [3]. In particular, we provide an overview of beam-line elements ported to GPUs and briefly discuss optimiza-tion techniques for efficient utilization of the device mem-ory space, with an emphasis on register usage. We also present a novel hardware-assisted technique for calculating a large histogram, and compare this to data-parallel imple-mentations. In addition, we provide an overview of recent work on a new build system for ELEGANT and integrat-ing GPU-accelerated elements with the existing codebase in a manner that allows 'silent' support of GPU accelera-tion. We conclude the paper with results of a realistic test simulation and comments o...
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
The Advanced Photon Source uses two distinct control programs for orbit control and stability-a f... more The Advanced Photon Source uses two distinct control programs for orbit control and stability-a full-featured workstation-based program for orbit control (sddscontrollaw) and an EPICS-based system, the Real-Time Fast Feedback System (RTFS), to reduce orbit motion. The sddscontrollaw program has been ported to EPICS and moved from the UNIX environment to an EPICS IOC attached to the RTFS. This EPICS-based program uses the RTFS's reflective memory to gather beam position information and write corrector power supplies, thus avoiding variable network latencies. This allows the orbit control to run at a correction rate 50 times that of the workstation implementation, which virtually eliminates orbit motion caused by insertion device gap changes. Issues raised by the integration of orbit control into the real-time feedback system and performance improvements are discussed.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
A circularly polarizing undulator capabable of switching the polarization very rapidly was instal... more A circularly polarizing undulator capabable of switching the polarization very rapidly was installed at the Advanced Photon Source. The net magnetic field perturbation is characterized in both planes by a transient orbit motion, which lasts about 30 ms, and a DC orbit shift. In addition, multipole magnetic moment errors are present. The correction system consists of small dipole and multipole correction magnets at the ends of the undulator, a multichannel arbitrary function generator (AFG) to program the corrector magnet current triggered on the polarization change event, low-level software to load and interpolate the AFG waveforms, and high-level software running on a workstation to determine the optimum AFG waveforms for the dipole correctors. We rely on the existing real-time feedback system to acquire the orbit transient and to automatically generate a close approximation of the required corrector wave forms. A choice of deterministic correction or trial-anderror manual adjustments of the wave forms is available in the high-level software.
The Advanced Photon Source (APS) is a 7-GeV hard x-ray synchrotron light source consisting of 40 ... more The Advanced Photon Source (APS) is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 77.2-cm-long section of spool pieces can be isolated by two gate valves and have an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50°C at 100 mA. A brief thermal analysis showed that the present observed temperature rise in the new chamber is mainly due to the resistive wall.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
In recent years many changes have been made to the Advanced Photon Source (APS) linear accelerato... more In recent years many changes have been made to the Advanced Photon Source (APS) linear accelerator (linac) to support multiple tasks. The primary purpose of the linac is to provide beam to fill the APS storage ring, which is done using thermionic cathode rf guns. At the same time we provide support for research projects, including a new facility that will be used for future operator training and testing of injector components. With each task requiring a different lattice and timing configuration, while at the same time using common rf systems, the complexity of operations has increased significantly with even greater demands being made on reliability and performance. In addition, personnel safety and equipment protection concerns have become more complex. We approached these challenges by developing three new subsystems: a highly automated linac operation using APS's Procedure Execution Manager (PEM) software; a new interlock system based on programmable logic controllers; and an automated S-band rf switching system. In this paper, we discuss how these developments have improved the flexibility and reliability of the APS linac, and how we intend to conduct operator training and test new injector components while maintaining storage ring injections.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
The Advanced Photon Source uses two distinct control programs for orbit control and stability-a f... more The Advanced Photon Source uses two distinct control programs for orbit control and stability-a full-featured workstation-based program for orbit control (sddscontrollaw) and an EPICS-based system, the Real-Time Fast Feedback System (RTFS), to reduce orbit motion. The sddscontrollaw program has been ported to EPICS and moved from the UNIX environment to an EPICS IOC attached to the RTFS. This EPICS-based program uses the RTFS's reflective memory to gather beam position information and write corrector power supplies, thus avoiding variable network latencies. This allows the orbit control to run at a correction rate 50 times that of the workstation implementation, which virtually eliminates orbit motion caused by insertion device gap changes. Issues raised by the integration of orbit control into the real-time feedback system and performance improvements are discussed.
At the Advanced Photon Source (APS) most of the testing of minor operational software is done dur... more At the Advanced Photon Source (APS) most of the testing of minor operational software is done during accelerator studies time. For major software changes, such as the porting of the complex workstation-based orbit control software to an EPICS IOC, much of the testing was done "offline" on a test IOC. A configurable storage ring simulator was created in a workstation with corresponding control system records for correctors and orbit readbacks.
Use of SDDS, the Self-Describing Data Sets file protocol and toolkit, has been a great benefit to... more Use of SDDS, the Self-Describing Data Sets file protocol and toolkit, has been a great benefit to development of several accelerator simulation codes. However, the serial nature of SDDS was found to be a bottleneck for SDDScompliant simulation programs such as parallel elegant. A parallel version of SDDS would be expected to yield significant dividends for runs involving large numbers of simulation particles. In this paper, we present a parallel interface for reading and writing SDDS files. This interface is derived from serial SDDS with minimal changes, but defines semantics for parallel access and is tailored for high performance. The underlying parallel I/O is built on MPI-I/O. The performance of parallel SDDS and parallel HDF5 are studied and compared. Our tests indicate better scalability of parallel SDDS compared to HDF5. We see significant I/O performance improvement with this parallel SDDS interface. *
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
Self-Describing Data Sets (SDDS) and the corresponding SDDS tools have long been used at the Adva... more Self-Describing Data Sets (SDDS) and the corresponding SDDS tools have long been used at the Advanced Photon Source (APS) and other laboratories for data storage and analysis. Various programs in the toolkit have been added or improved recently. Support for the Mac OS X operating system has been added. Automated testing scripts are being used to reduce bugs prior to software upgrades. The Java version of the SDDS Toolkit has been used to integrate standard SDDS functions into MATLAB. The fitting of generic functions to SDDS data has been improved. Conversion of array data to column data has been added to allow analysis of array data with existing programs. The display of sddsplot movies by saving plots to files for rapid playback has been improved.
PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268), 2001
The program GENESIS has been widely used for the simulation of free-electron lasers (FELs). We ex... more The program GENESIS has been widely used for the simulation of free-electron lasers (FELs). We extended the capabilities of the program by making the code compliant with the Self-Describing Data Set file protocol, whose toolkit has been developed and used extensively at Argonne. We report the modifications made to GENESIS and demonstrate the benefits by presenting the results obtained by its application to two major FEL projects: Argonne's Low-Energy Undulator Test Line and the Linac Coherent Light Source at SLAC.
The BSP-100 beam position monitor (BPM) was com-missioned and installed at the Advanced Photon So... more The BSP-100 beam position monitor (BPM) was com-missioned and installed at the Advanced Photon Source (APS) in a fraction of the ring as an upgrade to the present turn-by-turn BPMs. Keeping the same rf front end of the present BPMs, the BSP-100 BPM adds a high-...
Temperature dependent Mossbauer effect, magnetization and transport measurements have been made f... more Temperature dependent Mossbauer effect, magnetization and transport measurements have been made for (LaMn_0.98 ^57Fe_0.02)_1-deltaO3 . Various techniques of synthesis (air, Ar, quenching, slow cooling) are used to tailor the cation defect concentration delta, and thus control the Mn^3+/ Mn^4+ ratio and carrier concentration. Mossbauer effect measurements show that Fe is near 3+ in all compounds. The crystal structure changes from
The magnetic transition temperature and the transport behavior of La_0.83 Sr_0.17 Mn_1-y ^57Fey O... more The magnetic transition temperature and the transport behavior of La_0.83 Sr_0.17 Mn_1-y ^57Fey O3 are systematically varied by substitution of Fe (y = 0, 0.01, 0.02, 0.05, 0.10) for Mn. Mossbauer effect measuresments show that Fe remains near 3+ for all concentrations and, therefore does not play a role in charge hopping, but does lead to an increase in the
The effect on magnetic and magnetoresistive behavior of substituting Fe magnetic impurities on th... more The effect on magnetic and magnetoresistive behavior of substituting Fe magnetic impurities on the Mn sublattice in La_1-xSr_xMn_1-y^57Fe_yO3 has been studied. Perovskites with x=0, 0.1, 0.2, 0.3 and y= 0.02, 0.05, 0.10 have been synthesized in air or Ar to control the cation defect concentration. Thermogravimetric measurements were used to obtain defect-free samples. The materials have been characterized by XRD, magnetic and magnetoresistance measurements. Local magnetic behavior is monitored by temperature dependent (15-320 K) Mossbauer Effect measurements. The mean field, the influence of spin- and charge-fluctuation and chemical disorder have been delineated. The Fe ion is /sim 3+ for all compositions. The effect of Fe antiferromagnetic superexchange coupling to the magnetic Mn sublattice on magnetic behavior, and the effect of magnetic order on quadrupolar coupling and Debye-Waller factor will be discussed.footnote Supported by DARPA ONR, the State of Illinois under HECA and US DOE-BES No. W-31-109-ENG-38
The electron accelerator simulation software elegant [1] is being parallelized in a multi-year ef... more The electron accelerator simulation software elegant [1] is being parallelized in a multi-year effort. Re-cent developments include parallelization of input/output (I/O), frequency map analysis, dynamic aperture search, and position-dependent momentum aperture determina-tion. Parallel frequency map, momentum aperture analy-sis, and dyanmic aperture search provide rapid turnaround for important determinants of storage ring performance. The development of parallel Self-Describing Data Sets file (SDDS) I/O based on MPI-IO made it possible for paral-lel elegant (Pelegant) to take advantage of parallel I/O. Compared with previous versions of Pelegant with serial I/O, the new version not only enhances the I/O throughput with good scalability but also provides a feasible way to run simulations with a very large number of particles (e.g., 1 billion particles) by eliminating the memory bottleneck on the master with serial I/O. Another benefit of using parallel I/O is reducing the communicati...
The Advanced Photon Source (APS) linear accelerator has two thermionic cathode rf guns and one ph... more The Advanced Photon Source (APS) linear accelerator has two thermionic cathode rf guns and one photocathode rf gun. The thermionic guns are used primarily for APS operations while the photocathode gun is used as a free-electron laser (FEL) driver. With each gun requiring a different lattice and timing configuration, the need to change quickly between guns puts great demands on the accelerator operators. Using the Procedure Execution Manager (PEM), a software environment for managing automated procedures, we have made start-up and switch-over of the linac systems both easier and more reliable. The PEM is a graphical user interface written in Tcl/Tk that permits the user to invoke "machine procedures" and control their execution. It allows construction of procedures in a hierarchical, parallel fashion, which makes for efficient execution and development. In this paper, we discuss the features and advantages of the PEM environment as well the specifics of our procedures for t...
The Advanced Photon Source (APS) linear accelerator (linac) utilizes two thermionic cathode rf gu... more The Advanced Photon Source (APS) linear accelerator (linac) utilizes two thermionic cathode rf guns and one photocathode rf gun. The thermionic guns are primarily for APS operations while the photocathode gun is used as a free-electron laser (FEL) driver. With each gun requiring a different lattice and timing configuration, the need to change quickly between guns and maintain the required equipment protection puts great demands on the Main Control Room (MCR) operators. This paper discusses how the APS staff has learned to deal with the frequent changes required by a newly upgraded equipment safety interlock system and how they have become familiar with the automated control system called [1, 2] Procedure Execution Manager (PEM). Our linac is controlled via the Experimental Physics and Industrial Control System (EPICS), but the lessons are applicable to any control system.
Large scale beam dynamics simulations can derive sig-nificant benefit from efficient implementati... more Large scale beam dynamics simulations can derive sig-nificant benefit from efficient implementation of general-purpose particle tracking on GPUs. We present the latest results of our work on accelerating Argonne National Lab's accelerator simulation code ELEGANT, using CUDA-enabled GPUs. We summarize the performance of beam-line elements ported to GPU, and discuss optimization techniques for some core collective effects kernels, in par-ticular our methods of avoiding costly thread contention. We also outline briefly our testing and code validation in-frastructure within ELEGANT as well as a new template meta-programming infrastructure for streamlining code de-velopment.
Efficient implementation of general purpose particle tracking on GPUs can result in significant p... more Efficient implementation of general purpose particle tracking on GPUs can result in significant performance benefits to large scale particle tracking and tracking-based accelerator optimization simulations. We present our work on accelerating Argonne National Lab's accelerator simulation code ELEGANT [1, 2] using CUDA-enabled GPUs [3]. In particular, we provide an overview of beam-line elements ported to GPUs and briefly discuss optimiza-tion techniques for efficient utilization of the device mem-ory space, with an emphasis on register usage. We also present a novel hardware-assisted technique for calculating a large histogram, and compare this to data-parallel imple-mentations. In addition, we provide an overview of recent work on a new build system for ELEGANT and integrat-ing GPU-accelerated elements with the existing codebase in a manner that allows 'silent' support of GPU accelera-tion. We conclude the paper with results of a realistic test simulation and comments o...
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
The Advanced Photon Source uses two distinct control programs for orbit control and stability-a f... more The Advanced Photon Source uses two distinct control programs for orbit control and stability-a full-featured workstation-based program for orbit control (sddscontrollaw) and an EPICS-based system, the Real-Time Fast Feedback System (RTFS), to reduce orbit motion. The sddscontrollaw program has been ported to EPICS and moved from the UNIX environment to an EPICS IOC attached to the RTFS. This EPICS-based program uses the RTFS's reflective memory to gather beam position information and write corrector power supplies, thus avoiding variable network latencies. This allows the orbit control to run at a correction rate 50 times that of the workstation implementation, which virtually eliminates orbit motion caused by insertion device gap changes. Issues raised by the integration of orbit control into the real-time feedback system and performance improvements are discussed.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
A circularly polarizing undulator capabable of switching the polarization very rapidly was instal... more A circularly polarizing undulator capabable of switching the polarization very rapidly was installed at the Advanced Photon Source. The net magnetic field perturbation is characterized in both planes by a transient orbit motion, which lasts about 30 ms, and a DC orbit shift. In addition, multipole magnetic moment errors are present. The correction system consists of small dipole and multipole correction magnets at the ends of the undulator, a multichannel arbitrary function generator (AFG) to program the corrector magnet current triggered on the polarization change event, low-level software to load and interpolate the AFG waveforms, and high-level software running on a workstation to determine the optimum AFG waveforms for the dipole correctors. We rely on the existing real-time feedback system to acquire the orbit transient and to automatically generate a close approximation of the required corrector wave forms. A choice of deterministic correction or trial-anderror manual adjustments of the wave forms is available in the high-level software.
The Advanced Photon Source (APS) is a 7-GeV hard x-ray synchrotron light source consisting of 40 ... more The Advanced Photon Source (APS) is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 77.2-cm-long section of spool pieces can be isolated by two gate valves and have an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50°C at 100 mA. A brief thermal analysis showed that the present observed temperature rise in the new chamber is mainly due to the resistive wall.
Uploads
Papers by Robert Soliday