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Report on the SLC control system

Description: The SLC control system is based on a VAX 11/780 Host computer with approximately 50 microprocessor clusters which provide distributed intelligence and control of all CAMAC interface modules. This paper will present an overview of the system including current status and a description of the software architecture and communication protocols. 8 refs.
Date: May 1, 1985
Creator: Phinney, N.
Partner: UNT Libraries Government Documents Department

Timing system control software in the SLC

Description: A new timing system that allows precision (approx.1 to 2 ns) control of the trigger times of klystrons, beam position monitors, and other devices on a pulse-to-pulse basis at up to 360 Hz is in operation in the first third of the SLAC linear accelerator. The control software is divided between a central host VAX and local Intel 8086-based microprocessor clusters. Facilities exist to set up and adjust the timing of devices or groups of devices independently for beam pulses having different destinations and purposes, which are run in an interlaced fashion during normal machine operation. Upgrading of the system is currently underway, using a new version of the Programmable Delay Unit CAMAC module to allow pipelining of timing information for three machine pulses. An overview of the current state of the system is presented in this paper, with an emphasis on software control.
Date: April 1, 1985
Creator: Thompson, K. & Phinney, N.
Partner: UNT Libraries Government Documents Department

The SLC control system - status and development

Description: The SLC control system is installed and operational in the full SLC through the Linac, Damping Rings, Positron Source, Arcs and Final Focus. The system now includes a host VAX 11/785, a development VAX 11/780, 4 VAX workstations, a distributed network of 70 microprocessors, and about 270 Camac crates with more than 4000 modules. The micros are used for control and monitoring of the hardware, for pulse-to-pulse feedback, and for consoles (COWs). High level model-driven host software provides a variety of tools for beam setup, optimization, diagnosis, and stabilization. This paper will summarize the current status and projects under development.
Date: March 1, 1987
Creator: Phinney, N. & Shoaee, H.
Partner: UNT Libraries Government Documents Department

Klystron control software in the SLC

Description: Triggering, control, and monitoring of 240 high-power klystrons will be supported by the SLC control system this summer. The control software is distributed among a VAX host computer, a local microprocessor cluster, and a dedicated intelligent CAMAC module. The functions performed by these three components and the algorithms used are discussed.
Date: May 1, 1985
Creator: Jobe, R.K.; Thompson, K. & Phinney, N.
Partner: UNT Libraries Government Documents Department

An automated focal point positioning and emittance measurement procedure for the interaction point of the SLC

Description: To achieve maximum luminosity at the SLC, both the electron and positron beams must reach their minimum transverse size within 1 mm of the longitudinal location where the two bunches collide. This paper describes an automated procedure for positioning the focal point of each beam at this collision plant. The technique is based on measurements of the beam size utilizing either secondary emission or bremsstrahlung signals from carbon fibers a few microns in diameter. We have achieved simultaneous and reproducible measurements of the angular speed (/approximately/200 /mu/rad) and the optimum beam spot size (/approximately/2 /mu/m), which when combined yield measurements of the beam emittance consistent with those obtained using conventional profile monitor techniques. 8 refs., 5 figs., 1 tab.
Date: August 1, 1989
Creator: Phinney, N.; Bambade, P.; Kozanecki, W. & Koska, W.
Partner: UNT Libraries Government Documents Department

Beam position monitor readout and control in the SLC linac

Description: A beam position monitoring system has been implemented in the first third of the SLC linac which provides a complete scan of the trajectory on a single beam pulse. The data is collected from the local micro-computers and viewed with an updating display at a console or passed on to application programs. The system must operate with interlaced beams so the scans are also interlaced, providing each user with the ability to select the beam, the update rate, and the attenuation level in the digitizing hardware. In addition each user calibrates the hardware for his beam. A description of the system architecture will be presented. 6 refs., 4 figs.
Date: April 1, 1985
Creator: Bogart, J.; Phinney, N.; Ross, M. & Yaffe, D.
Partner: UNT Libraries Government Documents Department

Error message recording and reporting in the SLC control system

Description: Error or information messages that are signaled by control software either in the VAX host computer or the local microprocessor clusters are handled by a dedicated VAX process (PARANOIA). Messages are recorded on disk for further analysis and displayed at the appropriate console. Another VAX process (ERRLOG) can be used to sort, list and histogram various categories of messages. The functions performed by these processes and the algorithms used are discussed.
Date: April 1, 1985
Creator: Spencer, N.; Bogart, J.; Phinney, N. & Thompson, K.
Partner: UNT Libraries Government Documents Department

Feedback systems in the SLC

Description: Two classes of computer-controlled feedback have been implemented to stabilize parameters in subsystems of the SLC: (1) ''slow'' (time scales approx. minutes) feedback, and (2) ''fast'', i.e., pulse-to-pulse, feedback. The slow loops run in a single FEEDBACK process in the SLC host VAX, which acquires signals and sets control parameters via communication with the database and the network of normal SLC microprocessors. Slow loops exist to stabilize beam energy and energy spread, beam position and angle, and timing of kicker magnets, and to compensate for changes in the phase length of the rf drive line. The fast loops run in dedicated microprocessors, and may sample and/or feedback on particular parameters as often as every pulse of the SLC beam. The first implementations of fast feedback are to control transverse beam blow-up and to stabilize the energy and energy spread of bunches going into the SLC arcs. The overall architecture of the feedback software and the operator interface for controlling loops are discussed.
Date: February 1, 1987
Creator: Thompson, K.A.; Jobe, R.K.; Johnson, R. & Phinney, N.
Partner: UNT Libraries Government Documents Department

Availability and Reliability Issues for ILC

Description: The International Linear Collider (ILC) will be the largest most complicated accelerator ever built. For this reason extensive work is being done early in the design phase to ensure that it will be reliable enough. This includes gathering failure mode data from existing accelerators and simulating the failures and repair times of the ILC. This simulation has been written in a general fashion using MATLAB and could be used for other accelerators. Results from the simulation tool have been used in making some of the major ILC design decisions and an unavailability budget has been developed.
Date: June 27, 2007
Creator: Himel, T.; Nelson, J.; Phinney, N.; /SLAC; Ross, M. & /Fermilab
Partner: UNT Libraries Government Documents Department

Beam-Beam deflection as a beam tuning tool at the SLAC Linear Collider

Description: To achieve maximum integrated luminosity at the SLAC Linear Collider, a method of noninvasive beam tuning is required. Traditional luminosity monitors based on Bhabha scattering are inadequate because of low instantaneous counting rates. Coherent deflections of one beam by the electromagnetic field of the other are sensitive not only to the relative steering of the two bunches but also to their spot sizes. A brief description of beam-beam deflection theory forms the basis for a discussion of this phenomenon as a tool for single-beam tuning and for luminosity optimization at the interaction point of the SLC. 13 refs., 5 figs.
Date: April 1, 1989
Creator: Koska, W.; Bambade, P.; Kozanecki, W.; Phinney, N. & Wagner, S.R.
Partner: UNT Libraries Government Documents Department

Maintaining micron-size beams in collision at the interaction point of the Stanford Linear Collider

Description: In order to maintain collisions between two micron-size beams at the interaction point of the SLC, we take advantage of the mutual electromagnetic deflection induced by one beam on the other as they cross with a nonzero relative impact parameter. We determine simultaneously the incoming and outgoing trajectory parameters of each beam on a pulse-by-pulse basis, using beam position monitors located near the IP. Comparing incoming and outgoing angles for a given beam yields the magnitude of the deflection the beam experienced during the collision from which the distance currently separating the two beams can be extracted. A simple proportional control is applied to calculate the change in upstream corrector settings to null out this distance. 3 refs., 6 figs.
Date: May 1, 1991
Creator: Rouse, F.; Gromme, T.; Kozanecki, W. & Phinney, N.
Partner: UNT Libraries Government Documents Department

Automated emittance measurements in the SLC

Description: The emittance of the SLC beam is determined from measurements of the beam width on a profile monitor as a quadrupole field is varied. An automated system has been developed to allow this to be done rapidly and accurately. The image on a fluorescent screen profile monitor (resolution about 20 ..mu..m) is read out through an electronic interface and digitized by a transient recorder. A high level software package has been developed to set up the hardware for the measurements, acquire data, fit the beam width, and calculate the emittance.
Date: March 1, 1987
Creator: Ross, M.C.; Phinney, N.; Quickfall, G.; Shoaee, H. & Sheppard, J.C.
Partner: UNT Libraries Government Documents Department

Correlation plot facility in the SLC control system

Description: The Correlation Plot facility is a powerful interactive tool for data acquisition and analysis throughout the SLC. A generalized interface allows the user to perform a wide variety of machine physics experiments without the need for specialized software. It has been used extensively during SLC commissioning and operation. The user may step one or two independent parameters such as magnet or feedback setpoints while measuring or calculating up to 160 others. Measured variables include all analog signals available to the control system as well as a variety of derived parameters such as beam size or emittance. Various fitting algorithms and display options are provided for data analysis. A software-callable interface is also provided. Applications based on this facility are used to phase klystrons, measure emittance and dispersion, minimize beam size at the interaction point and maintain beam collisions. 4 refs., 3 figs.
Date: May 1, 1991
Creator: Hendrickson, L.; Phinney, N. & Sanchez-Chopitea, L.
Partner: UNT Libraries Government Documents Department

Correlation Plot facility in the SLC control system

Description: The Correlation Plot facility is a powerful interactive tool for data acquisition and analysis throughout the SLC. This generalized interface allows the user to perform a range of operations or machine physics experiments without the need for any specialized analysis software. The user may step one or more independent parameters, such as magnet or feedback setpoints, while measuring or calculating up to 160 other parameters. Measured variables include all analog signals available to the control system, as well as calculated parameters such as beam size, luminosity, or emittance. Various fitting algorithms and display options are provided. A software-callable interface has been provided so that a host of applications can call this package for analysis and display. Such applications regularly phase klystrons, measure emittance and dispersion, minimize beam size, and maintain beam collisions at the interaction point. 4 refs., 5 figs.
Date: November 1, 1991
Creator: Hendrickson, L.; Phinney, N.; Sanchez-Chopitea, L. & Clark, S.
Partner: UNT Libraries Government Documents Department

Computer control of the energy output of a klystron in the SLC

Description: Hardware and software have been developed to permit computer control of the output of high power klystrons on a pulsed basis. Control of the klystron output is accomplished by varying the input drive via a pulsed rf attenuator. Careful power calibrations permit accurate calculation of the available energy, as seen by the beam, over the full range of the klystron output. The ability to control precisely the energy output allows for energy feed-forward as well as energy feedback applications. Motivation for this work has been the need to adjust the energy of beams launched into various regions of the SLC. Vernier klystrons play a crucial role in the energy delivered from the SLC injector, linac, and positron source. This paper discusses the hardware development, energy calculations, and software implementation. Operational results are presented.
Date: February 1, 1987
Creator: Jobe, R.K.; Browne, M.J.; Flores, M.; Phinney, N.; Schwarz, H.D. & Sheppard, J.C.
Partner: UNT Libraries Government Documents Department

Operational experience with optical matching in the SLC Final Focus System

Description: In the SLC Final Focus System, all components of transverse phase-space and the couplings between them must be controlled to minimize the beam size at the interaction point. After summarizing the experimental algorithm and the on-line tuning programs, we present a consistent set of measurements and describe our present understanding of the various contributions to this beam size. 17 refs., 9 figs.
Date: January 1, 1989
Creator: Bambade, P.; Burchat, P.; Burke, D.; Ford, W.; Hawkes, C.; Koska, W. et al.
Partner: UNT Libraries Government Documents Department

Implementation of nonintercepting energy spread monitors

Description: Stripline beam position monitors (BPMs), located in regions of large dispersion, are being used to monitor the relative energy spread of beams injected into the SLC damping rings. Several BPMs have been configured so that the quadrupole moment as well as the dipole moment (beam position) information is generated in hardware. The dipole moment is subtracted in quadrature from the quadrupole moment to produce a signal which is related to the beam width but which is independent of the beam position. Data reduction and averaging is accomplished in the control system microprocessors. Additional data handling occurs in the host computer. Beam width signals from the devices are used in conjunction with RF phase adjustments to minimize the energy spread of the beams. A computer controlled feedback loop has been developed to oversee the process of energy spread manipulation.
Date: September 1, 1986
Creator: Sheppard, J.C.; Bambade, P.S.; Clendenin, J.E.; Gromme, T.E.; Jobe, R.K.; Phinney, N. et al.
Partner: UNT Libraries Government Documents Department

Position, angle and energy stabilization for the SLC positron target and ARCs

Description: Slow feedback has been developed to control the position, angle, and energy of the three SLC bunches in the linac at the South Arc, North Arc, and positron target respectively. A set of computer controlled feedback loops calculate the parameters of each bunch from beam position monitor data in the appropriate extraction line. The angles and positions are corrected by orthogonal sets of steering dipoles. The energy is corrected by adjusting the phase of two upstream sectors of the linac. This paper discusses the data acquisition and algorithms.
Date: February 1, 1987
Creator: Jobe, R.K.; Thompson, K.A.; Almog, I.; Phinney, N.; Seeman, J.T.; Sheppard, J.C. et al.
Partner: UNT Libraries Government Documents Department

Beam-based monitoring of the SLC linac optics with a diagnostic pulse

Description: The beam optics in a linear accelerator may be changed significantly by variations in the energy and energy spread profile along the linac. In particular, diurnal temperature swings in the SLC klystron gallery perturb the phase and amplitude of the accelerating RF fields. If such changes are not correctly characterized, the resulting errors will cause phase advance differences in the beam optics. In addition RF phase errors also affect the amplitude growth of betatron oscillations. The authors present an automated, simple procedure to monitor the beam optics in the SLC linac routinely and non-invasively. The measured phase advance and oscillation amplitude is shown as a function of time and is compared to the nominal optics.
Date: July 1, 1997
Creator: Assmann, R.W.; Decker, F.J.; Hendrickson, L.J.; Phinney, N.; Siemann, R.H.; Underwood, K.K. et al.
Partner: UNT Libraries Government Documents Department

PHASEFIX: Correcting the tunes of the SLC Arcs

Description: The betatron phase advance in the SLC ARC beam transport line is sensitive to gradient errors in the magnetic lattice. The systematic errors in the phase advance, combined with the rolls required to follow the terrain, can lead to xy-coupling which significantly distorts the betatron phase-space. The technique used to measure and correct the tune of the Arcs is reported. 9 refs., 7 figs.
Date: April 1, 1989
Creator: Haiessinski, J.; Bambade, P.; Brown, K.L.; Burke, D.L.; Fieguth, T.H.; Hutton, A. et al.
Partner: UNT Libraries Government Documents Department

Transverse wakefield control and feedback in the SLC (SLAC Linear Collider) linear

Description: Transverse wakefields in the linac of the SLAC Linear Collider (SLC) have been observed to enlarge the effective emittance of beams which are not properly centered in the accelerating structure. A fast feedback system has been constructed to minimize the enlargement under changing conditions by controlling the beam launching parameters. Theoretical aspects of this transverse feedback system are reviewed as well as the design of the beam sensors, launch controllers, communication equipment and data processing micro-computer. A variety of beam observations have been made. They show that dispersion as well as wakefield effects are important. In the near future the fast transverse feedback system will be beam tested, and algorithms tailored to the noise environment of the SLC will be tried.
Date: January 1, 1987
Creator: Seeman, J.T.; Campisi, I.E.; Herrmannsfeldt, W.; Lee, M.; Petersen, A.; Phinney, N. et al.
Partner: UNT Libraries Government Documents Department

Fast energy and energy spectrum feedback in the SLC Linac

Description: The energies and energy spectra of the positron and electron beams emerging from the SLC Linac must be carefully maintained so that the beams can be transported through the Arcs to the Final Focus without phase space dilution and also to specify the collision energy. A fastback system has been designed and constructed to control these parameters. The energies and energy spectra are measured nondestructively using position monitors and synchrotron radiation width monitors. The controls consist of rf phases in the Damping Rings, SLED timing, and rf amplitude. Theoretical aspects of the feedback process, algorithms, and operational experience are discussed.
Date: January 1, 1987
Creator: Abrams, G.S.; Soderstrom, E.; Seeman, J.T.; Campisi, I.E.; Herrmannsfeldt, W.; Lee, M. et al.
Partner: UNT Libraries Government Documents Department

Three bunch energy stabilization for the SLC injector

Description: Slow feedback has been developed to control the energy and energy spread of the beams which are injected into the SLC damping rings. Within a single RF pulse, two bunches of electrons and one bunch of positrons are accelerated to an energy of 1.21 GeV in the injector of the SLC. The two electron bunches are deflected into the north damping ring while the positrons are targeted into the south ring. In order to fit into the acceptance of the rings, the composite energy deviation and energy spread of the beams must be less than 2% full width. Control of the beam energy characteristics is accomplished with a set of computer controlled feedback loops which monitor the parameters of the three bunches and make adjustments to the available RF energy, RF phasing, and RF timing. This paper presents an overview of the feedback algorithms and of the special hardware developments, and reports on the operational status of the processes.
Date: September 1, 1986
Creator: Sheppard, J.C.; Almog, I.; Bambade, P.S.; Clendenin, J.E.; Jobe, R.K.; Phinney, N. et al.
Partner: UNT Libraries Government Documents Department