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Picosecond optical shutter for particle detection

Description: Characteristics of an optical shutter utilizing Kerr effect induced by picosecond laser pulses in carbon disulfide are studied experimentally. The shutter has a gate time of 4.5 to 5 ps full width at half-maximum and a transmission of approximately 15 percent at a wavelength 0.53 $mu$m. Such an ultrafast shutter can be used as an optical signal gate in a sampling detection scheme that has picosecond time-resolution. The picosecond optical detection scheme is envisioned to have applications in experimental high-energy physics such as to time-resolve ultrashort Cherenkov or synchrotron radiation emitted by relativistic particles. Methods of synchronizing a laser-activated Kerr shutter with a particle accelerator or synchrotron are discussed. (auth)
Date: April 1, 1975
Creator: Fan, B.; Gee, C.M. & Shapiro, G.
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

A Prototype Wire Position Monitoring System

Description: The Wire Position Monitoring System (WPM) will track changes in the transverse position of LCLS Beam Position Monitors (BPMs) to 1{micro}m over several weeks. This position information will be used between applications of beam based alignment to correct for changes in component alignment. The WPM system has several requirements. The sensor range must be large enough so that precision sensor positioning is not required. The resolution needs to be small enough so that the signal can be used to monitor motion to 1{micro}m. The system must be stable enough so that system drift does not mimic motion of the component being monitored. The WPM sensor assembly consists of two parts, the magnetic sensor and an integrated lock-in amplifier. The magnetic sensor picks up a signal from the alternating current in a stretched wire. The voltage v induced in the sensor is proportional to the wire displacement from the center of the sensor. The integrated lock-in amplifier provides a DC output whose magnitude is proportional to the AC signal from the magnetic sensor. The DC output is either read on a digital voltmeter or digitized locally and communicated over a computer interface.
Date: December 7, 2010
Creator: Wang, Wei
Partner: UNT Libraries Government Documents Department

Small Aperture BPM to Quadrupole Assembly Tolerance Study

Description: The LCLS injector and linac systems utilize a series of quadrupole magnets with a beam position monitor (BPM) captured in the magnet pole tips. The BPM measures the electron beam position by comparing the electrical signal from 4 electrodes and interpolating beam position from these signals. The manufacturing tolerances of the magnet and BPM are critical in determining the mechanical precision of the electrodes relative to the nominal electron beam Z-axis. This study evaluates the statistical uncertainty of the electrodes center axis relative to the nominal electron beam axis.
Date: December 7, 2010
Creator: Fong, K. W.
Partner: UNT Libraries Government Documents Department

Debuncher Profile Monitor Evaluation

Description: The original microchannel plates have been damaged in the beam region. After an attempt to revive the plates by baking, the gain of the central 30mm is still reduced by approximately a factor of three. The plates appear to have been irreversibly damaged by being operated for an extended period of time at high gain with high debuncher beam currents. A new set of microchannel plates has been installed in the monitor. Because of a production error, the gap between the microchannel plate output and the anode wire plane was set at 15mm instead of 3mm. The high voltage divider allowed a maximum of 170 volts to be applied across this gap. Under the conditions at which the Monitor was being operated, the distribution of collected electrons from a single micro channel was spread over a large area. A collimated UV light source which had a FWHM of 3mm produced a profile with a FWHM of 22mm with an amplifier threshold supply voltage of 1.0 V and FWHM of 9mm with a threshold voltage of 5.0V. See Figure 1. When new microchannel plates were installed, the anode gap was reduced to 9.5mm, and the gap voltage was increased to 760V, the results shown in Figure 2 were obtained. The width of the distribution depends strongly on the plate gain and discriminator threshold. Analog readout with a SWIC scanner eliminates the dependence of width on plate gain. Figure 3 shows two scanner profiles with plate gains differing by a factor of 64. The anode wire plane allows a significant fraction of the charge to leak through into the low field region behind the plane and spread over several wires before being captured by the wires. This produces broad tails on the width distribution. Replacing the wire plane with strip electrodes etched ...
Date: January 13, 1986
Creator: Krider, J.
Partner: UNT Libraries Government Documents Department

First Measurements and Results With a Stretched Wire Test Setup

Description: The LINAC Coherent Light Source [LCLS] is a free electron laser, designed to produce high brilliant X-ray beams using Self Amplified Spontaneous Emission [SASE]. Due to the physics of SASE, the electron beam has to be held very precisely on the same trajectory as the X-ray light beam generated by the undulator magnets. To optimize the SASE output, trajectory deviations between both beams have to be minimized to a few micrometers along the entire undulator section and held stable over the time period between beam-based-alignment processes. Consequently, extremely high position stability of all magnets in the undulator section is required to operate the LCLS successfully. The knowledge of any magnet movement exceeding few micrometers during periods of several weeks is essential for efficient X-ray generation. A well known principle of monitoring transverse component positions along beam lines is the application of stretched wires, associated with suitable wire position sensors and electronics. The particular challenge at LCLS is the required wire system performance in conjunction with the length of the undulator section and the large number of monitors. Verification of system stability and resolution under real conditions is the primary goal of this test setup. A stretched wire test setup has been implemented to gain experience for the final design of a wire system, which will meet the position monitoring requirements in the LCLS undulator section. The report briefly introduces the system's architecture and describes first measurements and results.
Date: December 13, 2010
Creator: Peters, Franz
Partner: UNT Libraries Government Documents Department

A 10 um Resolution Secondary Emission Monitor for Fermilab's Targeting Station

Description: Improvement in focusing the proton beam onto the antiproton production target necessitates the development of a higher resolution beam profile monitor. Two designs for the construction of a multiwire profile mointor grid are presented. The first is a conventional strung and tensioned Ti wire design. The second is a photo etched Ti grid of wires bonded to a ceramic substrate. Both have a central wire spacing of 125 {mu}m. The completed beam profile monitors are designed to operate in a 120 GeV beam pulse of 5 x 10{sup 12} protons with a 1.5{mu}s duration and will be installed in late 1993.
Date: January 1, 1994
Creator: Hurh, P.; O'Day, S.; Dombrowski, R.; Page, T. & /Fermilab
Partner: UNT Libraries Government Documents Department

Time resolved detection with MOS radiation detectors with memory

Description: MOS radiation detectors with memory have been used to time resolve a portion of an alectron beam pulse from a 704 Febetron. These detectors have the three functions of detection, memory, and readout all integrated into a single device so that time resolved detection can be performed without the requirement of realtime diagnostics. Good agreement was obtained between the waveshapes of the time resolved signal of the MOS radiation detector with memory and a real time MOS radiation detector used as a reference monitor of the Febetron's pulse. The time resolution of the detector system was 6.6 nsec. No effort was made to calibrate the output of the MOS detectors with radiation dose. (auth)
Date: July 1, 1973
Creator: Balch, J. W.
Partner: UNT Libraries Government Documents Department

Commissioning a Vibrating Wire System for Quadrupole Fiducialization

Description: Quadrupoles will be placed between the undulator segments in LCLS to keep the electron beam focused as it passes through. The quadrupoles will be assembled with their respective undulator segments prior to being placed into the tunnel. Beam alignment will be used to center the quadrupoles, along with the corresponding undulators, on the beam. If there is any displacement between the undulator and the quadrupole axes in the assemblies, the beam will deviate from the undulator axis. If it deviates by more than 80{micro}m in vertical or 140{micro}m in horizontal directions, the undulator will not perform as required by LCLS. This error is divided between three sources: undulator axis fiducialization, quadrupole magnetic axis fiducialization, and assembly of the two parts. In particular, it was calculated that the quadrupole needs to be fiducialized to within 25{micro}m in both vertical and horizontal directions. A previous study suggested using a vibrating wire system for finding the magnetic axis of the quadrupoles. The study showed that the method has high sensitivity (up to 1{micro}m) and laid out guidelines for constructing such a system. There are 3 steps in fiducializing the quadrupole with the vibrating wire system. They are positioning the wire at the magnet center (step 1), finding the wire with position detectors (step 2), and finding the quadrupole tooling ball positions relative to the position detector tooling balls (step 3). A previous study investigated the error associated with each step by using a permanent quadrupole magnet on an optical mover system. The study reported an error of 11{micro}m for step 1 and a repeatability of 4{micro}m for step 2. However, the set up used a FARO arm to measure tooling balls and didn't allow to accurately check step 2 for errors; an uncertainty of 100{micro}m was reported. Therefore, even though the repeatability was ...
Date: December 3, 2010
Creator: Levashov, Michael Y
Partner: UNT Libraries Government Documents Department

Estimate of Undulator Magnet Damage Due to Beam Finder Wire Measurements

Description: Beam Finder Wire (BFW) devices will be installed at each break in the Undulator magnet line. These devices will scan small wires across the beam causing some electrons to lose energy through bremsstrahlung. The degraded electrons are subsequently detected downstream of a set of vertical dipole magnets after they pass through the vacuum chamber. This signal can then be used to accurately determine the beam position with respect to the BFW wire. The choice of the wire diameter, scan speed, and operating parameters, depends on the trade-off between the signal size and the radiation damage to the undulator magnets. In this note I estimate the rate of undulator magnet damage that results from scanning as a function of, wire size, scan speed, and average beam current. A separate analysis of the signal size was carried out by Wu. The damage estimate is primarily based on two sources: the first, Fasso, is used to estimate the amount of radiation generated and then absorbed by the magnets; the second, Alderman et. al., is used to estimate the amount of damage the magnet undergoes as a result of the absorbed radiation. Fasso performed a detailed calculation of the radiation, including neutron fluence, that results from a the electron beam passing through a 100 micron diamond foil inserted just in front of the undulator line. Fasso discussed the signficance of various types of radiation and stated that photoneutrons probably play a major role. The estimate in this paper assumes the neutron fluence is the only significant cause of radiation-induced demagnetization. The specific results I use from Fasso's paper are reproduced here in Figure 1, which shows the radial distribution of the integrated neutron fluence per day in the undulator magnets, and Figure 2, which shows the absorbed radiation dose all along the undulator line. ...
Date: December 3, 2010
Creator: Welch, J.
Partner: UNT Libraries Government Documents Department

Set Up and Test Results for a Vibrating Wire System for Quadrupole Fiducialization

Description: Quadrupoles will be placed between the undulator segments in LCLS to keep the electron beam focused as it passes through. The quadrupoles will be assembled with their respective undulator segments prior to being placed into the tunnel. Beam alignment will be used to center the quadrupoles, along with the corresponding undulators, on the beam. If there is any displacement between the undulator and the quadrupole axes in the assemblies, the beam will deviate from the undulator axis. If it deviates by more than 80{micro}m in vertical or 140{micro}m in horizontal directions, the undulator will not perform as required by LCLS. This error is divided between three sources: undulator axis fiducialization, quadrupole magnetic axis fiducialization, and assembly of the two parts. In particular, it was calculated that the quadrupole needs to be fiducialized to within 25{micro}m in both vertical and horizontal directions. A previous study suggested using a vibrating wire system for finding the magnetic axis of a quadrupole. The study showed that the method has high sensitivity (up to 1{micro}m) and laid out guidelines for constructing it. There are 3 steps in fiducializing the quadrupole with the vibrating wire system. They are positioning the wire at the magnet center (step 1), finding the wire with position detectors (step 2), and finding the quadrupole tooling ball positions relative to the position detector tooling balls (step 3). The following break up of error was suggested for the fiducialization steps: 10{micro}m for step 1 (finding the center), 20{micro}m for step 2 (finding the wire), and 10{micro}m for step 3 (tooling ball measurements). The purpose of this study is to investigate whether the vibrating wire system meets the requirements for LCLS. In particular, if it can reliably fiducialize a quadrupole magnetic center to within 25{micro}m in both vertical and horizontal directions. The behavior of ...
Date: December 1, 2010
Creator: Levashov, Michael Y.
Partner: UNT Libraries Government Documents Department

Set Up and Test Results for a Vibrating Wire System for Quadrupole Fiducialization

Description: Quadrupoles will be placed between the undulator segments in LCLS to keep the electron beam focused as it passes through. The quadrupoles will be assembled with their respective undulator segments prior to being placed into the tunnel. Beam alignment will be used to center the quadrupoles, along with the corresponding undulators, on the beam. If there is any displacement between the undulator and the quadrupole axes in the assemblies, the beam will deviate from the undulator axis. If it deviates by more than 80{micro}m in vertical or 140{micro}m in horizontal directions, the undulator will not perform as required by LCLS. This error is divided between three sources: undulator axis fiducialization, quadrupole magnetic axis fiducialization, and assembly of the two parts. In particular, it was calculated that the quadrupole needs to be fiducialized to within 25{micro}m in both vertical and horizontal directions. A previous study suggested using a vibrating wire system for finding the magnetic axis of a quadrupole. The study showed that the method has high sensitivity (up to 1{micro}m) and laid out guidelines for constructing it. There are 3 steps in fiducializing the quadrupole with the vibrating wire system. They are positioning the wire at the magnet center (step 1), finding the wire with position detectors (step 2), and finding the quadrupole tooling ball positions relative to the position detector tooling balls (step 3). The following break up of error was suggested for the fiducialization steps: 10{micro}m for step 1 (finding the center), 20{micro}m for step 2 (finding the wire), and 10{micro}m for step 3 (tooling ball measurements). The purpose of this study is to investigate whether the vibrating wire system meets the requirements for LCLS. In particular, if it can reliably fiducialize a quadrupole magnetic center to within 25{micro}m in both vertical and horizontal directions. The behavior of ...
Date: November 29, 2010
Partner: UNT Libraries Government Documents Department

Space-Charge Effects in a Gas Detector

Description: Discussion of space-charge effects in a photoluminescence cell that will be used as a nondisruptive total energy monitor at the LCLS facility is presented. Regimes where primary photoelectrons will be confined within the X-ray beam aperture are identified. Effects of the space-charge on the further evolution of the electron and ion populations are discussed. Parameters of the afterglow plasma are evaluated. Conditions under which the detector output will be proportional to the pulse energy are defined.
Date: December 3, 2010
Creator: Ryutov, D.D.
Partner: UNT Libraries Government Documents Department

Summary of QM02 Measurements

Description: This note summarizes both the beam-based and various laboratory measurements of quadrupole magnets, units 387 and 428, used for QM02 in the LCLS Injector. These were undertaken because of a consistent discrepancy between accelerator model predictions and beam observations which seemed to indicate a weak QM02. A report 'QM02 Strength Measurement', by Welch and Wu, describes the discrepancy and beam-based measurements on unit 387. Subsequently, unit 387 was replaced by unit 428, refinements were made to analysis of the beam-based measurements were made, and additional magnetic measurements were made on unit 387 in the lab. These new results are summarized in this note. The principle results are: (1) Laboratory measurements of integrated gradient for the same magnet, or for different magnets of the same type, are all within 1% of each other at gradients of interest. These cases cover three independent types of measurements, disassembly/reassembly of the units, and extended periods of time between measurements. (2) Standardization, or lack thereof, can cause integrated gradient errors of approximately 0.2 kG, which can amount to a few percent of the strength of the magnet depending on the setting. (3) Model-independent beam-based measurements indicate the magnets are actually weaker than expected by about 2 percent, but these measurements are subject to the uncertainty of the BPMS1 location. (4) The standardization cycle is effective. (5) The stainless steel BPM vacuum chamber inside the magnets has no significant effect on the beam. The discrepancy between the accelerator model predictions and the actual orbit response is not resolved, but the evidence points away from magnetic strength errors as the source. Differences between the model locations and effective locations of BPM's is a possible culprit. This idea is explored in Section 2. Table 1 summarizes the measurement activities that were performed on the units. The dates listed ...
Date: December 3, 2010
Creator: Fisher, Andrew
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

BPM Signal Level Calculation

Description: This note is a short summary of the calculation of the induced signal on a transmission line type BPM pickup plate.
Date: February 5, 2001
Creator: McGinnis, Dave
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