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A prototype ionization profile monitor for RHIC

Description: Transverse beam profiles in the Relativistic Heavy-Ion Collider (RHIC) will be measured with ionization profile monitors (IPM`s). Each IPM collects and measures the distribution of electrons in the beamline resulting from residual gas ionization during bunch passage. The electrons are swept transversely from the beamline and collected on strip anodes oriented parallel to the beam axis. At each bunch passage the charge pulses are amplified, integrated, and digitized for display as a profile histogram. A prototype detector was tested in the injection line during the RHIC Sextant Test. This paper describes the detector and gives results from the beam tests.
Date: July 1, 1997
Creator: Connolly, R.; Cameron, P. & Ryan, W.
Partner: UNT Libraries Government Documents Department

The LEDA beam-position measurement system

Description: This paper describes the beam-position measurement system being developed for the Low Energy Demonstration Accelerator (LEDA) and the Accelerator Production of Tritium (APT) projects at Los Alamos National Laboratory. The system consists of a beam-position monitor (BPM) probe, cabling, down-converter module, position/intensity module, on-line error-correction system, and the necessary control system interfaces. The modules are built on the VXI-interface standard and are capable of duplex data transfer with the control system. Some of the key, system parameters are: position-measurement bandwidth of at least 180 kHz, the ability to measure beam intensity, a beam-position measurement accuracy of less than 1.25 percent of the bore radius, a beam-current dynamic range of 46 dB, a total system dynamic range in excess of 75 dB, and built-in on-line digital-system-error correction.
Date: August 1, 1997
Creator: Rose, C.R.; Gilpatrick, J.D. & Stettler, M.W.
Partner: UNT Libraries Government Documents Department

Observation of the spread of the readings in the Linac toroids and BPMs

Description: The readback accuracy on the high-energy toroids is about 0.26 mA. This does not consider, completely, the relative offsets among the toroids, just the accuracy of one reading on one toroid. Similarly, if you remove the way in which the beam moves in the beam pipe and ignore the relative offsets of the BPMs themselves, then the absolute accuracy of the reading on a BPM is 35 microns.
Date: November 9, 2001
Creator: McCrory, Elliott S
Partner: UNT Libraries Government Documents Department


Description: Transferring high-speed digital signals to a Digital Signal Processor is limited by the IO bandwidth of the DSP. A digital receiver circuit is used to translate high frequency W signals to base-band. The translated output frequency is close to DC and the data rate can be reduced, by decimation, before transfer to the DSP. By translating both the longitudinal beam (bunch) and RF cavity pick-ups (bucket) to DC, a DSP can be used to measure their relative phase angle. The result can be used as an error signal in a beam control servo loop and any phase differences can be compensated.
Date: May 12, 2003
Partner: UNT Libraries Government Documents Department

Quadrupole Beam-Based Alignment in the RHIC Interaction Regions

Description: Continued beam-based alignment (BBA) efforts have provided significant benefit to both heavy ion and polarized proton operations at RHIC. Recent studies demonstrated previously unknown systematic beam position monitor (BPM) offset errors and produced accurate measurements of individual BPM offsets in the experiment interaction regions. Here we describe the algorithm used to collect and analyze data during the 2010 and early 2011 RHIC runs and the results of these measurements.
Date: March 1, 2011
Creator: Satogata, T.
Partner: UNT Libraries Government Documents Department

A laser-wire beam-energy and beam-profile monitor at the BNL linac

Description: In 2009 a beam-energy monitor was installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. This device measures the energies of electrons stripped from the 40mA H{sup -} beam by background gas. Electrons are stripped by the 2.0x10{sup -7}torr residual gas at a rate of {approx}1.5x10{sup -8}/cm. Since beam electrons have the same velocities as beam protons, the beam proton energy is deduced by multiplying the electron energy by m{sub p}/m{sub e}=1836. A 183.6MeV H{sup -} beam produces 100keV electrons. In 2010 we installed an optics plates containing a laser and scanning optics to add beam-profile measurement capability via photodetachment. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. This paper describes the upgrades to the detector and gives profile and energy measurements.
Date: March 28, 2011
Creator: Connolly, R.; Degen, C.; DeSanto, L.; Meng, W.; Michnoff, R.; Minty, M. et al.
Partner: UNT Libraries Government Documents Department

R_transport_matrices of the Fast Extraction Beam (FEB) of the AGS, and Beam Parameters at the Starting point of the AtR Line

Description: As part of the task to improve and further automate the 'AtR BPM Application' we provide the theoretically calculated R-transport-matrices for the following beam line sections, which are shown schematically in Figure 1: (a) the Fast Extraction Beam section (FEB) of the AGS synchrotron. The FEB section starts at the middle of the GlO-kicker and ends at the middle of the H1 0{_}septum. (b) the Drift Extraction Channel (DEC) section of the AGS synchrotron. The DEC section starts at the middle of the H10{_}septum, continues along the fringe field region of the H11,H12, and H13 AGS main magnets, and ends at the starting point of the AtR line. The knowledge of these R-transport-matrices are needed in order to calculate the beam parameters at the beginning of the AtR line, which in turn, are required to calculate the magnet settings of the U{_}line, that match the U{_}line into the W{_}line. Also by incorporating these R{_}matrices into the model of the AtR line, the G10 kicker and the H10 septum are included in the AtR model therefore one can investigate any 'jitter' of either the GlO{_}kicker or HlO{_}septum by looking at the trajectory of the beam in the AtR line.
Date: January 1, 2008
Creator: Tsoupas,N.; MacKay, W.W.; Satogata, T.; Glenn, W.; Ahrens, L.; Brown, K. et al.
Partner: UNT Libraries Government Documents Department

Accelerator Simulation and Operation Via. Identical Operational Interfaces

Description: The CEBAF accelerator contains approximately 2500 power supplies, 340 klystrons, and 800 beam monitors. The operation of such a complex machine requires a control system which can provide a high degree of automation with strong support by simulation and modeling programs.\nWe present the architecture and first results of a control system which allows one the use of identical operation procedures and interfaces for operation of the real accelerator and high-level accelerator simulation programs. The interfaces were developed using TACL (Thaumaturgic Automated Control Logic) control software, developed at CEBAF for accelerator control. This setup provides the capability to: (1) test and debug the various operation procedures before the completion of the accelerator, (2) execute machine simulations under realistic environmental conditions, and (3) preview and evaluate the effectiveness of operational procedures during run time. The optimized simulation program adds only two seconds to
Date: May 1, 1991
Creator: Barry, Andrea; Bowling, Bruce; Lahti, George; Sage, Joan; Tang, Johnny; Kewisch, Jorg et al.
Partner: UNT Libraries Government Documents Department

Proposal for the Alignment of the 'Loose End'

Description: The 'loose end' of the girder presents an alignment problem because there is no beam based alignment procedure available to position it. The positioning always depends on the fiducialization of the undulator. A direct way to position the 'loose end' to the next quadrupole is to measure their fiducials in relation to each other. By spanning a wire over a distance of several girders, each undulator and quadrupole can be measured by reading its distance to the wire with a portable wire sensor. The pitch of a girder can be determined by measuring height differences at different points on the girder. To measure the height differences a portable HLS is used. During the measurements of the portable system the permanent Wire Position Monitor and the permanent HLS are used to monitor the interim movements of the girder. After the initial alignment the position of the 'loose end' can be monitored with the permanent systems in relation to the quadrupoles.
Date: December 1, 2010
Creator: Gassner, Georg
Partner: UNT Libraries Government Documents Department

Checking the Beam Energy Calculation from the June 14, 2000 $\psi^\prime$ Scan

Description: The Conclusions/Recommendations of this paper are: (1) It is very important to keep the orbit close to the reference orbit. (2) It is likely that BPMs are not perfectly calibrated. (3) The orbit length calculation with Quad Steering ON is more sensitive to errors in the BPM readout than with Quad Steering OFF. However, unless we are at the {psi}{prime}, Quad Steering should be ON. (4) Question: Should we use the BPM corrections derived from this scan? Answer: I don't know. I would prefer not to. If we keep the orbit close to the reference, we don't need the corrections. For cases where the orbit differs appreciably from the reference orbit, we should do the energy calculation both ways. (Perhaps with Quad steering ON and OFF too). (5) We should use the reference orbit derived from this scan. However, if there is the time and the man power, it would be desireable to do a proper scan of the {psi}{prime}.
Date: June 14, 2000
Creator: Werkema, Steve
Partner: UNT Libraries Government Documents Department

Preliminary studies of a chromaticity tracker

Description: A chromaticity tracker based on a method by D. McGinnis is proposed. This method starts with the slow modulation of the accelerating RF which causes the beam to respond to it. This beam modulation can be detected transversely with a Schottky pickup which after phase demodulation, the chromaticity can be calculated from it. However, to perform phase demodulation, the carrier frequency which is the betatron tune needs to be identified. The identification of the carrier frequency falls naturally onto the phase locked loop tune tracker which when locked to the betatron tune outputs this value in real time.
Date: March 1, 2006
Creator: Tan, Cheng-Yang
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

Time resolved, 2-D hard X-ray imaging of relativistic electron-beam target interactions on ETA-II

Description: Advanced radiographic applications require a constant source size less than 1 mm. To study the time history of a relativistic electron beam as it interacts with a bremsstrahlung converter, one of the diagnostics they use is a multi-frame time-resolved hard x-ray camera. They are performing experiments on the ETA-II accelerator at Lawrence Livermore National Laboratory to investigate details of the electron beam/converter interactions. The camera they are using contains 6 time-resolved images, each image is a 5 ns frame. By starting each successive frame 10 ns after the previous frame, they create a 6-frame movie from the hard x-rays produced from the interaction of the 50-ns electron beam pulse.
Date: November 1998
Creator: Crist, C. E.; Sampayan, S.; Westenskow, G.; Caporaso, G.; Houck, T.; Weir, J. et al.
Partner: UNT Libraries Government Documents Department

3-D electromagnetic modeling of wakefields in accelerator components

Description: We discuss the use of 3-D finite-difference time-domain (FDTD) electromagnetic codes for modeling accelerator components. Computational modeling of cylindrically symmetric structures such as induction accelerator cells has been very successful in predicting the wake potential and wake impedances of these structures, but full 3-D modeling of complex structures has been limited due to substantial computer resources required for a full 3-D model. New massively parallel 3-D time domain electromagnetic codes now under development using conforming unstructured meshes allow a substantial increase in the geometric fidelity of the structures being modeled. Development of these new codes are discussed in context of applicability to accelerator problems. Various 3-D structures are tested with an existing cubical cell FDTD code and wake impedances compared with simple analytic models for the structures; results will be used as benchmarks for testing the new time time domain codes. Structures under consideration include a stripline beam position monitor as well as circular and elliptical apertures in circular waveguides. Excellent agreement for monopole and dipole impedances with models were found for these structures below the cutoff frequency of the beam line.
Date: September 18, 1996
Creator: Poole, B.R.; Caporaso, G.J.; Ng, Wang C.; Shang, C.C. & Steich, D.
Partner: UNT Libraries Government Documents Department

Beam position monitor

Description: An apparatus for determining the position of an x-ray beam relative to a desired beam axis where the apparatus is positioned along the beam path so that a thin metal foil target intersects the x-ray beam generating fluorescent radiation. A PIN diode array is positioned so that a portion of the fluorescent radiation is intercepted by the array resulting in a series of electrical signals from the PIN diodes making up the array. The signals are then analyzed and the position of the x-ray beam is determined relative to the desired beam path.
Date: September 21, 2000
Creator: Alkire, Randy W.; Rosenbaum, Gerold & Evans, Gwyndaf
Partner: UNT Libraries Government Documents Department


Description: This paper will discuss the present electronics design for the beam current monitor system to be used throughout the Spallation Neutron Source (SNS) under construction at Oak Ridge National Laboratory. The beam is composed of a micro-pulse structure due to the 402.5MHz RF, and is chopped into mini-pulses of 645ns duration with a 300ns gap, providing a macro-pulse of 1060 mini-pulses repeating at a 60Hz rate. Ring beam current will vary from about 15ma peak during studies, to about 50Amps peak (design to 100 amps). A digital approach to droop compensation has been implemented and initial test results presented.
Date: May 6, 2002
Partner: UNT Libraries Government Documents Department