摘要:

Time‐resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free‐electron Laser (FEL) facility 40‐MeV linac. Two key timescales for rf‐linac driven FELs are the micropulse (10 ps) and the macropulse (5 &mgr;s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head‐to‐tail transverse kick effects are reported as a function of charge.

ISSN:0094-243X    

DOI:10.1063/1.44357

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Plans, prototypes, and initial test results for the charged‐particle beam (e−,e+) diagnostic systems on the injector rings, their transport lines, and the storage ring for the Advanced Photon Source (APS) are presented. The APS will be a synchrotron radiation user facility with one of the world’s brightest x‐ray sources in the 10‐keV to 100‐keV regime. Its 200‐MeV electron linac, 450‐MeV positron linac, positron accumulator ring, 7‐GeV booster synchrotron, 7‐GeV storage ring, and undulator test lines will also demand the development and demonstration of key particle‐beam characterization techniques over a wide range of parameter space. Some of these parameter values overlap or approach those projected for fourth generation light sources (linac‐driven FELs and high brightness storage rings) as described at a recent workshop. Initial results from the diagnostics prototypes on the linac test stand operating at 45‐MeV include current monitor data, beam loss monitor data, and video digitization using VME architecture.

ISSN:0094-243X    

DOI:10.1063/1.44358

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

With a fast‐gated camera, synchrotron light was used for studying the transverse beam distributions and damping times in the Stanford Linear Collider (SLC) damping rings. By digitizing the image in the camera signal, the turn‐by‐turn time evolution of the transverse beam distribution was monitored and analyzed. The projections of the digitized image were fit with Gaussian functions to determine the moments of the distribution. Practical applications include the determination of injection matching parameters and the transverse damping times. In this report we describe a synchrotron light monitor and present experimental data obtained in the SLC damping rings.

ISSN:0094-243X    

DOI:10.1063/1.44333

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Heavy Ion Fusion requires moderate currents, 1‐10A, for a duration of about 1 &mgr;s. For accurate beam transport, the center of charge must be located to within ±100 &mgr;m. Beam position and intensity may be excited at frequencies approaching 10 MHz, and the monitoring system must have adequate bandwidth to respond at these frequencies.We have modified the Rogowski technique by using distributed reactance multiturn magnetic loops so that it is suitable for measuring current position as well as amplitude. Four identical stripline coils are wound one per quadrant around a non magnetic core. The sensitivity is similar to that of a lumped coil system, with the added advantage of increased bandwidth. The voltages induced on the four separate coils are compared and suitable signal conditioning is performed to recover beam position and intensity information.

ISSN:0094-243X    

DOI:10.1063/1.44334

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A broad‐band theory of the circular button pickup is presented. Expressions for the longitudinal and transverse transfer impedance of a pair of such pickups are derived in the frequency domain. The broad‐band expressions are shown to reduce to the standard electrostatic transfer functions for wavelengths large compared to the button diameter. The theory is shown to be in reasonable agreement with measurements performed on standard LEP button electrodes. In particular, the theory explains a resonance in the response of the LEP buttons which made them unsuitable, in standard form, for their intended application as pickups in the LBL Advanced Light Source feedback system. The buttons were modified to suppress the resonance and subsequently incorporated into the feedback system.

ISSN:0094-243X    

DOI:10.1063/1.44335

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

To measure a longitudinal charge distribution in an ion linac beam it is preferable to apply bunch shape monitors using a low energy secondary emission electrons. Monitors of this type and their development are discussed. Different varieties of rf deflectors for a transverse modulation of secondary electrons are considered. Preliminary parameters of a bunch shape monitor for the SSC linac are presented. A detector to measure both longitudinal and transverse distributions of a two component ion beam is described.

ISSN:0094-243X    

DOI:10.1063/1.44336

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The preliminary design of the beam loss monitor for the ANL Advanced Photon Source is based on the use of an air dielectric coaxial cable as a long ionization chamber. Each coacial cable section uses a high sensitivity DC current‐to‐voltage converter with both linear and integrating ranges. Pulse timing circuits determine the positions of individual losses by measuring the time at which the resulting voltage pulses arrive at the beginning of the coaxial ionization chamber. A possible timing ambiguity can be removed by correlating the particle bunch timing with the resulting voltage pulse timing. Measurements have shown that pulse rise times less than 15 nanoseconds can be obtained, so that determining loss locations to better than 7 feet may be possible. Best performance may be obtained when 500 VDC is applied to a 50‐ohm, 7/8‐inch air dielectric coaxial cable filled with approximately 8 psig of a 95% argon, 5% carbon dioxide gas mixture. Cable lengths will be between 100 and 300 feet long, depending on the part of the accelerator being monitored.

ISSN:0094-243X    

DOI:10.1063/1.44338

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

It is desired to design a position and angle jitter control system for pulsed linear accelerators that will increase the accuracy of correction over that achieved by currently used standard feedback jitter control systems. Interpulse or pulse‐to‐pulse correction is performed using the average value of each macropulse. The configuration of such a system resembles that of a standard feedback correction system with the addition of an adaptive controller that dynamically adjusts the gain‐phase contour of the feedback electronics. The adaptive controller makes changes to the analog feedback system between macropulses. A simulation of such a system using real measured jitter data from the Stanford Linear Collider was shown to decrease the average rms jitter by over two and a half times. The system also increased and stabilized the correction at high frequencies; a typical problem with standard feedback systems.

ISSN:0094-243X    

DOI:10.1063/1.44339

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A bunch length instability, nicknamed the ‘‘sawtooth’’, because of its transient behavior, has been observed at high current running in the Stanford Linear Collider (SLC) electron damping ring. The incompatibility of this instability with successful SLC running prompted its study using a high bandwidth real‐time spectrum analyzer, the Tektronix 3052 digital signal processor (DSP) system. This device has been used to study energy ramping in storage rings but this is the first time it has been used to study transient instability phenomena. It is a particularly valuable tool for use in understanding non‐linear, multiple frequency phenomena. The frequency range of this device has been extended through the use of radio freqeuncy (RF) down converters. This paper describes the measurement setup and presents some of the results.

ISSN:0094-243X    

DOI:10.1063/1.44340

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Accelerators with superconducting magnets have special requirements for beam current measurement. Two different systems to measure beam current in the HERA proton ring are presented: a.) A Parametric Current Transformer (d.c to 100 kHz) measures the total circulating beam current in the ring and provides the absolute calibration. b.) The Bunch Current Monitor is a specialized system for low values of beam current. It features an Integrating Current Transformer as a beam sensor and signal processing with a new combination of charge amplifier and dual gated integrator to restore the d.c. baseline reference. The large dynamic range and high resolution permit fast beam lifetime measurements at low values of beam current.

ISSN:0094-243X    

DOI:10.1063/1.44341

出版商:AIP    

年代:1992

数据来源: AIP