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LLNL flash x-ray radiography machine (FXR) double-pulse upgrade diagnostics

Description: When the FXR machine was first tuned on the 1980`s, a minimal amount of diagnostics was available and consisted mostly of power monitors. During the recent accelerator upgrade, additional beam diagnostics were added. The sensor upgrades included beam bugs (resistive wall beam motion sensors) and high-frequency B-dot. Even with this suite of measurement tools, tuning was difficult. For the current Double- Pulse Upgrade, beam transport is a more complex problem--the beam characteristics must be measured better. Streak and framing cameras, which measure beam size and motions, are being added. Characterization of the beam along the entire accelerator is expected and other techniques will be evaluated also. Each sensor has limitations and only provides a piece of the puzzle. Besides providing more beam data, the set of diagnostics used should be broad enough so results can be cross validated. Results will also be compared to theoretical calculations and computer models, and successes and difficulties will be reported.
Date: June 26, 1997
Creator: Ong, M.; Avalee, C.; Richardson, R. & Zentler, J.
Partner: UNT Libraries Government Documents Department


Description: The production of high-brightness particle beams calls for the development of advanced beam diagnostics. High brightness beams, meaning beams with a high density in phase space, are important for many applications, such as short-wavelength Free-Electron Lasers and advanced accelerator systems. A diagnostic that provides detailed information on the density distribution of the electron bunch in multi-dimensional phase-space is an essential tool for obtaining small emittance at a high charge. This diagnostic system has been developed at Brookhaven National Laboratory. One component of the system is the measurement of a slice emittance which provides a measurement of transverse beam properties (such as emittance) as a function of the longitudinal position. Changing the laser pulse profile of a photocathode RF gun has been suggested as one way to achieve non-linear emittance compensation and improve the brightness and that can be diagnosed by the slice emittance system. The other element of the diagnostic is the tomographic reconstruction of the transverse phase. In our work we give special attention to the accuracy of the phase space reconstruction and present an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases. This high precision phase space tomography together with the ability to modify the radial charge distribution of the electron beam presents an opportunity to improve the emittance and apply non-linear radial emittance corrections. Combining the slice emittance and tomography diagnostics leads to an unprecedented visualization of phase space distributions in 5 dimensional phase-space and an opportunity to perform high-order emittance corrections. This should lead to great improvements in the beam brightness.
Date: November 24, 1998
Creator: BEN-ZVI,I.
Partner: UNT Libraries Government Documents Department

CEBAF beam loss accounting

Description: This paper describes the design and implementation of a beam loss accounting system for the CEBAF electron accelerator. This system samples the beam curent throughout the beam path and measures the beam current accurately. Personnel Safety and Machine Protection systems use this system to turn off the beam when hazardous beam losses occur.
Date: December 31, 1995
Creator: Ursic, R.; Mahoney, K.; Hovater, C.; Hutton, A. & Sinclair, C.
Partner: UNT Libraries Government Documents Department

A photon beam position monitor for SSRL beamline 9

Description: We present here the concept of a simple one dimensional photon beam position monitor for use with high power synchrotron radiation beams. It has micron resolution, reasonable linearity in an inexpensive design. Most important, is its insensitivity to diffusely scattered low energy radiation from components upstream of the monitor.
Date: October 1, 1995
Creator: Cerino, J.A.; Rabedeau, T. & Bowen, W.
Partner: UNT Libraries Government Documents Department

Measurement of sub-picosecond bunch profiles using coherent transition radiation

Description: A technique for measuring the longitudinal profile of sub-picosecond electron bunches based on autocorrelation of coherent transition radiation is reviewed. The technique uses sub-millimeter/far-infrared Michelson interferometry to obtain the autocorrelation of transition radiation emitted from a thin conducting foil placed in the beam path. The theory of coherent radiation from a charged particle beam passing through a thin conducting foil is presented for normal and oblique incidence. Michelson interferometric analysis of this radiation is shown to provide the autocorrelation of longitudinal bunch profile. The details of a noninvasive technique for measuring longitudinal bunch profile using coherent diffraction radiation are discussed.
Date: May 1, 1996
Creator: Barry, W.
Partner: UNT Libraries Government Documents Department

Laser diagnostic for high current H{sup {minus}} beams

Description: Laser photodetachment can be used on high current, high energy H{sup {minus}} beams to carry out a wide variety of beam diagnostic measurements parasitically during normal operation, without having to operate the facility at either reduced current or duty cycle. Suitable Q-switched laser systems are small, inexpensive, and can be mounted on or near the beamline. Most of the proposed laser-based diagnostics techniques have already been demonstrated.
Date: January 1, 1998
Creator: Shafer, R.E.
Partner: UNT Libraries Government Documents Department

A multi-wire beam profile monitor in the AGS

Description: A multi-wire beam profile monitor which can be used to directly monitor and control the optical matching between the Booster and AGS rings has been installed and tested in the AGS. Placement of a multi-wire monitor directly in the AGS provides profile measurements taken upon injection and the first two or more revolutions of the beam. The data from such measurements can be used to determine the optical properties of the beam transport line leading into the AGS.
Date: July 1, 1997
Creator: Huang, H.; Buxton, W.; Castillo, V. & Glenn, J.W.
Partner: UNT Libraries Government Documents Department

Conceptual design of a proton polarimeter for RHIC

Description: A two-arm pion polarimeter utilizing toroidal magnets is being considered for use with the polarized protons beam at RHIC. The system will enable measurements of beam polarization at all RHIC energies from injection to flattop. This is a necessary diagnostic tool for tuning the RHIC snake magnets and other polarization controlling elements. Toroidal magnets constrain the pion trajectories allowing the device to be compact so that it can fit within the limited space available. A viable magnet design has been completed and suitable target configuration and operating scenario have been identified.
Date: December 1, 1996
Creator: Alekseev, I.; Belikov, N. & Bunce, G.
Partner: UNT Libraries Government Documents Department

1 nA beam position monitoring system

Description: A system has been developed at Jefferson Lab for measuring transverse position of very low current beams delivered to the Experimental Hall B of the Continuous Electron Beam Accelerator Facility (CEBAF). At the heart of the system is a position sensitive cavity operating at 1497 MHz. The cavity utilizes a unique design which achieves a high sensitivity to beam position at a relatively low cavity Q. The cavity output RF signal is processed using a down-converter and a commercial lock-in amplifier operating at 100 kHz. The system interfaces with a VME based EPICS control system using the IEEE, 488 bus. The main features of the system are simple and robust design, and wide dynamic range capable of handling beam currents from 1 nA to 1000 nA with an expected resolution better than 100 {mu}m. This paper outlines the design of the system.
Date: June 1, 1997
Creator: Ursic, R.; Flood, R. & Piller, C.
Partner: UNT Libraries Government Documents Department

Beam control and laser characterization for NIF

Description: The demanding energy, power, pulse shape, focusability, pointing, and availability requirements placed on the 192 National Ignition Facility (NIF) beams lead to the need for an automatic operation capability that is well beyond that of previous inertial confinement fusion (ICF) lasers. Alignment, diagnostic, and wavefront correction subsystems are integrated in an approach that, by permitting maximal sharing of instrumentation between subsystems, meets performance requirements at a reasonable cost.
Date: June 10, 1998
Creator: Boege, S. J., LLNL
Partner: UNT Libraries Government Documents Department

Beam diagnostics challenges for future FELs

Description: Designs are being developed to produce diffraction-limited sources based on storage-ring free-electron lasers (FELs) for the VUV and soft x-ray regime and linac-driven FELs in the few {Angstrom} regime. The requirements on the beam quality in transverse emittance (rms, normalized) of 1-2 {pi} mm mrad, bunch length (1 ps to 100 fs), and peak current (1 to 5 kA) result in new demands on the diagnostics. The diagnostics challenges include spatial resolution (1-10 {mu}m), temporal resolution (<100 fs), and single-pulse position measurements ({approximately}1 {mu}m). Examples of recent submicropulse (slice) work are cited as well as concepts based on spontaneous emission radiation (SER). The nonintercepting aspects of some of these diagnostics should also be applicable to high-power FELs.
Date: April 1, 1997
Creator: Lumpkin, A.H.
Partner: UNT Libraries Government Documents Department

A new optical design for the BNL isotope production transport line

Description: The 200 MeV linac at BNL has recently been upgraded. As a result, 2.5 times more average beam current can be delivered to the Brookhaven Isotope Resource Center (BIRC), formerly called BLIP, a facility which produces radionuclides and radiopharmaceutical for the medical community, and also supports a research program seeking more effective diagnostic and therapeutic agents. The optics of the beam transport line to BIRC was redesigned to (a) reduce transverse fluctuations of the beam at the target due to any linac energy fluctuations, (b) produce a flat beam distribution at the target, in order to avoid melting certain target materials, and (c) handle the higher beam intensity while keeping radiation levels low. A profile monitor was also modified to monitor the flatness of the beam using the algebraic reconstruction technique (ART). The above improvements will be described, and results of the commissioning of the line during the 1996 running period will be discussed.
Date: October 1, 1996
Creator: Kponou, A.; Alessi, J.G.; Raparia, D.; Mapes, M. & Tsoupas, N.
Partner: UNT Libraries Government Documents Department

Emittance formula for slits and pepper-pot measurement

Description: In this note, a rigid formula for slits and pepper-pot emittance measurement is derived. The derivation is based on the one- dimensional slit measurement setup. A mathematical generalization of the slit emittance formula to the pepper-pot measurement is discussed.
Date: October 1, 1996
Creator: Zhang, M.
Partner: UNT Libraries Government Documents Department

Diagnostics for induction accelerators

Description: The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at LLNL from the early 1960`s to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400 ns pulses. The Advanced Test Accelerator (ATA) built at Livermore`s Site 300 produced 10,000 Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and LBNL. This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high current, short pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail.
Date: April 1, 1996
Creator: Fessenden, T.J.
Partner: UNT Libraries Government Documents Department

Experiments in non-perturbative electron beam characterization with the MIT microwiggler at the Accelerator Test Facility at BNL

Description: We report a new method through which the properties of an electron beam at linac energies may be studied using the spontaneous emission of a microwiggler. The setup is simple and the measurement efficient. A simple set of scaling laws is derived to describe broadening of spontaneous emission in a narrow bandwidth radiation cone. The relations suggest that one can obtain beam divergence from a cone at large angle in a single shot measurement. A systematic series of experiments was performed with the MIT Microwiggler at the Accelerator Test Facility at BNL which demonstrated the response of the cone to changes in the beam quality, Estimates of divergence can be obtained from the measurements of the radiation cone.
Date: November 1, 1996
Creator: Qiu, X.; Babzien, M.; Ben-Zvi, I. & Graves, W.
Partner: UNT Libraries Government Documents Department

Performance issues, downtime recovery and tuning in the Next Linear Collider (NLC)

Description: The Next Linear Collider (NLC) consists of several large subsystems, each of which must be operational and tuned in order to deliver luminosity. Considering specific examples, we study how the different subsystems respond to various perturbations such as ground motion, temperature changes, drifts of beam-position monitors etc., and we estimate the overall time requirements for tuning and downtime recovery of each subsystem. The succession of subsystem failures and recoveries as well as other performance degradations can be modeled as a Markov process, where each subsystem is characterized, e.g., by its failure rate and recovery time. Such a model allows the prediction of the overall NLC availability. Our mathematical description of a linear collider is benchmarked against the known performance of the Stanford Linear Collider (SLC).
Date: May 1, 1997
Creator: Zimmermann, F.; Adolphsen, C. & Assmann, R.
Partner: UNT Libraries Government Documents Department

Development and test results of the low-energy demonstration accelerator (LEDA) proton injector on a 1.25 MeV cw radio frequency quadrupole

Description: The low-energy demonstration accelerator (LEDA) 75-keV proton injector is being developed for tests of high-current (100-mA) cw linacs. The injector comprises a microwave proton source and a space-charge neutralized magnetic low-energy beam-transport system (LEBT). The LEDA injector has been configured to provide flexible 50-keV beam matching into a cw 1.25-MeV radio-frequency quadrupole (RFQ) brought from Chalk River Laboratories (CRL). The LEBT has two solenoid focus magnets separated by 117 cm. Between the solenoids are two steering magnets and diagnostic stations for measuring the beam current, profile, and position. The ion-source extraction system was modified to a 50-keV triode to test the injector/RFQ system. Beam-matching tests showed that injector-RFQ transmission is 90% for 50-mA RFQ current. At the RFQ design current of 75 mA the beam transmission decreased to 80--85%. Optimized injector tuning led to 100-mA beam accelerated through the RFQ.
Date: December 31, 1998
Creator: Sherman, J.; Bolme, G. & Hansborough, L.
Partner: UNT Libraries Government Documents Department

Techniques for intense-proton-beam profile measurements

Description: In a collaborative effort with industry and several national laboratories, the Accelerator Production of Tritium (APT) facility and the Spallation Neutron Source (SNS) linac are presently being designed and developed at Los Alamos National Laboratory (LANL). The APT facility is planned to accelerate a 100-mA H{sup +} cw beam to 1.7 GeV and the SNS linac is planned to accelerate a 1- to 4-mA-average, H{sup {minus}}, pulsed-beam to 1 GeV. With typical rms beam widths of 1- to 3-mm throughout much of these accelerators, the maximum average-power densities of these beams are expected to be approximately 30- and 1-MW-per-square millimeter, respectively. Such power densities are too large to use standard interceptive techniques typically used for acquisition of beam profile information. This paper summarizes the specific requirements for the beam profile measurements to be used in the APT, SNS, and the Low Energy Development Accelerator (LEDA)--a facility to verify the operation of the first 20-MeV section of APT. This paper also discusses the variety of profile measurement choices discussed at a recent high-average-current beam profile workshop held in Santa Fe, NM, and will present the present state of the design for the beam profile measurements planned for APT, SNS, and LEDA.
Date: December 31, 1998
Creator: Gilpatrick, J.D.
Partner: UNT Libraries Government Documents Department

Time-resolved imaging of electron and positron beams at APS

Description: Characterizations of stored electron beams and more recently positron beams circulating in the Advanced Photon Source (APS) 7-GeV storage ring have been done using optical synchrotron radiation (SR) and x-ray synchrotron radiation (XSR) imaging techniques. Results include the measurement of the bunch length and horizontal beam size versus single-bunch current for both electron and positron beams, observations of multibunch bunch length effects near 100 mA stored beam current, and initial diagnostics of a coupled-bunch instability with 15-minute period. Both the Hamamatsu C5680 dual-sweep streak camera using OSR and a pinhole camera using XSR from a bending magnet source point were utilized. Proposed enhancements to the beamline will also be presented.
Date: June 1, 1997
Creator: Lumpkin, A.H. & Yang, B.X.
Partner: UNT Libraries Government Documents Department

The SLAC NLC extraction & diagnostic line

Description: A prototype extraction line for the Next Linear Collider is discussed that has several important functions that include optimizing luminosity, characterizing beam properties at the Interaction Point and transporting beams from the IP to a dump. Beam characterization includes measurements of current, position, profile, energy, polarization and low-order correlations on a bunch-to-bunch basis for feedback and stabilization. Prototype optical and diagnostic layouts are described that provide such functions. The authors also consider possibilities for e, {mu} and {gamma} secondary beam lines and dump experiments as well as energy recovery and local reuse of an assumed 10MW in each 500 GeV beam.
Date: May 1, 1995
Creator: Spencer, J.; Irwin, J.; Walz, D. & Woods, M.
Partner: UNT Libraries Government Documents Department

Diagnostic beam pulses for monitoring the SLC linac

Description: The Stanford Linear Collider is a pulsed machine with a repetition rate of 120 Hz. By using fast devices such as kickers and triggers, individual pulses can be modified, measured and diagnosed, and then dumped to avoid any background in the experiment. For more than five years, a diagnostic pulse has been used to kick the beams onto off-axis screens at the end of the linac every 6 seconds. This provides a visual monitor of the beam size and loses about 0.14% of the rate or two minutes a day. The sensitivity of the linac optics to temperature and phase variations makes it desirable to monitor the phase advance between different locations in order to make local corrections. In principle, the feedback systems can measure the phase advance using the natural jitter of the beam. In practice, the phase jitter of the beam with respect to the rf may dominate the betatron jitter and distort the measurement. By using a large induced betatron oscillation, the two effects can be separated. To improve the monitoring of phase advance, a small kicker at the beginning of the linac is fired every few seconds and the orbit of this particular beam pulse measured and analyzed. The sensitivity, the measured variation and the correction scheme will be discussed.
Date: June 1, 1995
Creator: Decker, F.J.; Stanek, M.; Smith, H. & Tian, F.
Partner: UNT Libraries Government Documents Department

Disruption effects on the beam size measurement

Description: At the SLC Final Focus with higher currents and smaller beam sizes, the disruption parameter D{sub y} is close to one and so the pinch effect should produce a luminosity enhancement. Since a flat beam-beam function is fit to deflection scan data to measure the beam size, disruption can affect the measurement. Here the authors discuss the quantitative effects of disruption for typical SLC beam parameters. With 3.5 10{sup 10} particles per pulse, bunch length of 0.8 mm and beam sizes of 2.1 {mu}m horizontally and 0.55 {mu}m vertically, the measured vertical size can be as much as 25% bigger than the real one. Furthermore during the collision the spot size actually decrease, producing an enhancement factor H{sub D} of about 1.25. This would yield to a true luminosity which is 1.6 times that which is estimated from the beam-beam deflection fit.
Date: June 1, 1995
Creator: Raimondi, P.; Decker, F.J. & Chen, P.
Partner: UNT Libraries Government Documents Department