摘要:

The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and x‐ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4 kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and x‐ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back to the global orbit data to the local feedback systems. The effect of the eddy current induced in the relatively thick (1/2 in.) vacuum chamber by the ac corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the x‐ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will also be presented.

ISSN:0094-243X    

DOI:10.1063/1.46962

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We have developed several analytic and experimental techniques to measure the divergence and emittance of charged particle beams, which employ optical transition radiation (OTR) produced from thin intercepting foils. OTR’s directionality, promptness, linearity, polarization, and the sensitivity of its angular distribution to energy and divergence, can be all exploited to diagnose the spatial distribution, energy, and emittance of a charged particle beam. We describe the techniques we have developed to separately determine thexandyemittances of a beam at anxorywaist using OTR from a single foil or a two foil OTR interferometer. These methods have proven to be especially valuable for diagnosing low emittance electron beams produced by FEL accelerators, which range in energy from 17 to 110 Mev. However, we have shown that there is no inherent theoretical limit to the utility of these methods for much higher energy lepton or hadron beams. The advantages of OTR methods over those commonly used to diagnose beam properties are described.

ISSN:0094-243X    

DOI:10.1063/1.46965

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The Advanced Light Source (ALS), a third‐generation synchrotron light source, has been recently commissioned. Beam diagnostics were very important to the success of the operation. Each diagnostic system is described in this paper along with detailed discussion of its performance. Some of the systems have been in operation for two years. Others, in the storage ring, have not yet been fully commissioned. Those systems were, however, working well enough to provide the essential information needed to store beam. The devices described in this paper include wall current monitors, a beam charge monitor, a 50 ohm Faraday cup, dc current transformers, broad‐band striplines, fluorescent screens, beam collimators and scrapers, and beam position monitors. Also, the means by which waveforms are digitized and displayed in the control room is discussed.

ISSN:0094-243X    

DOI:10.1063/1.46987

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Study of signal to noise and dynamic range of systems is a very important part of engineering. The topic of signal to noise has been covered extensively in the literature, but not necessarily from a practical standpoint. Discussion of dynamic range issues is virtually missing from most fundamental texts. I would like this paper to show some of the practical ways of looking at designing a system. For completeness the fundamental equations will be included, but the emphasis will be on real system implementation. The paper will draw extensively from actual system designs at Fermilab.

ISSN:0094-243X    

DOI:10.1063/1.46988

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Beam diagnostics at high‐intensity facilities feature their own special set of problems and characteristics, issues peculiar to high‐intensity storage rings include beam loss, beam halos, extraction efficiency, beam in the gap, clearing electrodes, and beam‐profile measurement. The Los Alamos Proton Storage Ring (PSR) is a nice example of a high‐intensity storage ring. I will discuss in some detail three diagnostic systems currently in use at the PSR: the beam‐loss‐monitor system, the electron‐clearing system, and the beam‐in‐the‐gap monitor. Much of our discussion is inspired by the problems we have encountered and the useful things we have learned while commissioning and developing the PSR. Another inspiration is our work on the next‐generation neutron‐spallation source, also known as the National Center for Neutron Research (NCNR).

ISSN:0094-243X    

DOI:10.1063/1.46989

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

This tutorial describes the generation of electrical signals in gas detectors. Ionization of the gas by the passage of charged particles generates these signals. Starting with the Bethe‐Bloch equation, the treatment is a general introduction to the production of ion‐pairs in gas devices. I continue with the characterization of the ionization as an electrical signal, and calculate the signal current in a simple example. Another example demonstrates the effect of space charge on the design of a detector. The AGS Booster ionization profile monitor is a model for this calculation.

ISSN:0094-243X    

DOI:10.1063/1.46990

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The Superconducting Super Collider (SSC), Linac Beam Position Monitor System is designed to measure beam position and phase. Forty‐three monitors will be installed in the Linac and Transfer Line. The position measurement provides information on the transverse beam position in the beam pipe with respect to a mechanical reference. The phase measurement provides information on the difference between the longitudinal phase of the beam and the radio frequency reference signal (rf reference), to be used for phase scanning and time of flight measurement. The system design and the prototypes are complete, and the series is under fabrication. The signals to be processed are extracted from four striplines, down‐converted to a convenient intermediate frequency and fed into position and phase electronics. The position electronics is realized with the log‐ratio technique, and the phase electronics uses a new digital technique that overcomes most of the problems of existing systems. Both position and phase analog electronics are mounted on identical VXI motherboards, containing analog‐to‐digital converters (ADC’s) and digital circuitry.

ISSN:0094-243X    

DOI:10.1063/1.46978

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A new 30 m beamline (BL1C) is being assembled to connect the new High Intensity Polarized Ion Source (HIPIOS) to the IUCF cyclotrons. This line is being instrumented for complete automatic optimization of all transverse and longitudinal ion optical elements by providing a unique feedback signal for each controllable device. Transversely, steerers and 4‐quadrant electrostatic pickups are located approximately 90° apart in betatron phase advance along the beamline. Each pickup is instrumented with a single‐board, 4‐layer op‐amp circuit (BPM system) which measures the beam intensity, horizontal (H) and vertical (V) position, and H and V 10 Hz position modulation. The transverse beam ellipse parameters are first automatically determined at the entrance to the beamline by measuring the beam size using a wire scanner as a function of the strength of a quadrupole. The computer then programs the amplitude and phase of four 10 Hz modulators which vary the current in 4 steerers to move the beam centroid around this (reduced area) ellipse in 4‐dimensional phase space. The BPM system then outputs voltages proportional to the beam intensity, centroid location, and envelope. Computer algorithms will then set the steerers and quadrupoles to correct the beam position, dispersion, and envelope. Longitudinally, hardware feedback loops, with a bandwidth adjustable from 10 Hz to 30 kHz, will phase‐lock the beam to the two bunching systems; another hardware system will automatically vary the buncher amplitudes to compensate for the significant and varying space charge defocusing as the beam current fluctuates. The bunchers’ quiescent phases and amplitudes will be optimized using software ‘‘synchronous detectors.’’

ISSN:0094-243X    

DOI:10.1063/1.46979

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

It is desired to design a predictive feedforward transverse jitter control system to control both angle and position jitter in pulsed linear accelerators. Such a system will increase the accuracy and bandwidth of correction over that of currently available feedback correction systems. Intrapulse correction is performed. An offline process actually ‘‘learns’’ the properties of the jitter, and uses these properties to apply correction to the beam. The correction weights calculated offline are downloaded to a real‐time analog correction system between macropulses. Jitter data were taken at the Los Alamos National Laboratory (LANL) Ground Test Accelerator (GTA) telescope experiment at Argonne National Laboratory (ANL). The experiment consisted of the LANL telescope connected to the ANL ZGS proton source and linac. A simulation of the correction system using this data was shown to decrease the average rms jitter by a factor of two over that of a comparable standard feedback correction system. The system also improved the correction bandwidth.

ISSN:0094-243X    

DOI:10.1063/1.46980

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The progress of the design of the 204 detectors required for the Fermilab Main Injector (FMI), Beam Position Monitor (BPM), system is described. To conserve space, the detectors will be located inside the quadrupole magnets. The output from four striplines shorted at one end will be combined to form either horizontal or vertical detectors. Commercially available software was used to select the geometry of the striplines for desired characteristic impedance, linearity, and output power. Prototype measurements are shown to agree with simulation and mechanical issues are discussed.

ISSN:0094-243X    

DOI:10.1063/1.46981

出版商:AIP    

年代:1994

数据来源: AIP