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Fast ion chambers for SLC

Description: Beam diagnostic ion chambers are used throughout the SLC to perform a variety of tasks including locating beam losses along the beam direction, determining localized losses from individual bunches in a multibunch beam, and detecting scattered particles from beam profile wire scanners where backgrounds are too high to use photomultiplier tubes. Construction and instrumentation of very fast ion chambers with pulse duration of less than 60ns are detailed. Long ion chambers referred to as PLIC (Panofsky`s Long Ion Chamber) are the primary diagnostic used to locate losses in all the SLC transport lines. Accurately locating beam loss with the use of fiducial cables and coaxial switches will be discussed.
Date: July 1, 1993
Creator: McCormick, D.
Partner: UNT Libraries Government Documents Department

Control of coaxial cable propagation delay for a beam phase monitor

Description: The average position of the beam near the crest of the accelerating voltage in the Stanford Linear Collider linac must be kept stable total fraction of an S-band wavelength or about 0.5ps. Temperature stabilized S-band RF distribution cables and phase monitors have been installed along the 3km linac to minimize the effects of the up to 40 degree F daily temperature excursions in the support building environment. In this paper, we present test results of the equipment designed to determine the stability of the RF distribution system by comparing it directly tot the beam. In particular, efforts to stabilize the propagation delay of the system`s coaxial cables will be described.
Date: July 1, 1993
Creator: McCormick, D. & Ross, M.
Partner: UNT Libraries Government Documents Department

Occupational Radiation Exposure at Commercial Nuclear Power Reactors and Other Facilities 2010, Prepared for the Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, May 2012

Description: This report summarizes the occupational exposure data that are maintained in the U.S. Nuclear Regulatory Commission’s (NRC) Radiation Exposure Information and Reporting System (REIRS). The bulk of the information contained in the report was compiled from the 2010 annual reports submitted by five of the seven categories of NRC licensees subject to the reporting requirements of 10 CFR 20.2206. Because there are no geologic repositories for high-level waste currently licensed and no NRC-licensed low-level waste disposal facilities currently in operation, only five categories will be considered in this report. The annual reports submitted by these licensees consist of radiation exposure records for each monitored individual. These records are analyzed for trends and presented in this report in terms of collective dose and the distribution of dose among the monitored individuals. Annual reports for 2010 were received from a total of 190 NRC licensees. The summation of reports submitted by the 190 licensees indicated that 192,424 individuals were monitored, 81,961 of whom received a measurable dose. When adjusted for transient workers who worked at more than one licensee during the year, there were actually 142,471 monitored individuals and 62,782 who received a measurable dose. The collective dose incurred by these individuals was 10,617 person-rem, which represents a 12% decrease from the 2009 value. This decrease was primarily due to the decrease in collective dose at commercial nuclear power reactors, as well as a decrease in the collective dose for most of the other categories of NRC licensees. The number of individuals receiving a measurable dose also decreased, resulting in an average measurable dose of 0.13 rem for 2010. The average measurable dose is defined as the total effective dose equivalent (TEDE) divided by the number of individuals receiving a measurable dose. In calendar year 2010, the average annual collective dose per ...
Date: July 7, 2012
Creator: McCormick, D. E. Lewis D. A. Hagemeyer Y. U.
Partner: UNT Libraries Government Documents Department

Experience with wire scanners at SLC

Description: Fifty wire scanners are in use at SLC for phase space and beam optics monitoring. A large number of failures of the 50 {mu}m wire used in the scanners have occurred. Studies of these show strong electro-magnetic fields produced by the beam to be the probable cause. The problem has been cured with the adoption of a ceramic mounting scheme. Other improvements including very high dynamic range scans and scans of non-gaussian beams are described.
Date: December 1, 1992
Creator: Ross, M. C.; Bong, E.; Hendrickson, L.; McCormick, D. & Zolotorev, M.
Partner: UNT Libraries Government Documents Department

Length monitor for 1 mm SLC bunches

Description: A non-intercepting RF bunch length monitor for {sigma}{sub z} = 0.5 to 2.0 mm long electron and positron bunches in the Stanford Linear Collider (SLC) has been built with a design similar to a previous device for longer bunches. For this device, fields from the beam pass through a ceramic gap, enter receiving cavities, are the measured with power detectors, and finally are recorded by the SLC control computer. The designs of the receiving cavities (25 and 36 GHz) are described as well as the choice of the RF power distribution and measuring systems. Beam measurements have been taken as a function of bunch compressor RF voltage, bunch intensity, and beam position. Long term bunch length measurements were recorded during SLC colliding beam operation indicating that the bunch length is constant to about 3%. Thus, 1 mm length monitors operating at 25 and 36 GHz have successfully monitored long term bunch length changes at the few percent level in the SLC.
Date: June 1, 1993
Creator: Babenko, E.; Jobe, R. K.; McCormick, D. & Seeman, J. T.
Partner: UNT Libraries Government Documents Department

Thermal stabilization of low level RF distribution systems at SLAC

Description: Analysis of SLC accelerator operator activity, in particular control system knob turns, indicated poor thermal stability performance of the low level RF distribution system in the SLC injector and positron production complex. Daily drifts of up to 15 S-band delay, about 30 times the tolerance, were observed. In this paper we describe the tool used to track down and quantify operator knob turn activity, the low level RF distribution stabilization systems, and some fixes used to correct the problem. In order to identify poorly performing components, a beam timing or phase monitor diagonstic has been developed. Initial results from it will be presented.
Date: July 1, 1993
Creator: McCormick, D.; Ross, M.; Himel, T. & Spencer, N.
Partner: UNT Libraries Government Documents Department

Beam dispersion measurements with wire scanners in the SLC final focus systems

Description: A method is described to make a direct measurement of the horizontal and vertical momentum dispersion of the electron and positron beams as they pass through the chromatic correction sections (CCS) of the SLC final focus systems. The method is advantageous since it cleanly separates betatron components of the beam size from dispersive components, can be measured during standard colliding beams machine conditions in a minute or two, and directly measures the energy-position correlation within the beam.
Date: May 1, 1993
Creator: Emma, P.; McCormick, D. & Ross, M. C.
Partner: UNT Libraries Government Documents Department

Positron jitter and wakefield effects in the SLC injector linac

Description: The positron beam in the SLC injector linac is a high current (7*10{sup 10} particles/bunch), large universe emittance ({gamma}{var_epsilon} = .01 m-rad) and long bunch length ({approximately}4 mm) beam. A large 5% positron intensity jitter was observed and correlated with the accelerating phase of the RF cavities in the positron source linac. For high transmission, the positron jitter must be reduced and strong wakefield effects cannot be ignored. A code was written to study causes of the positron jitter and wakefields in the SLC injector linac. The tracking results show that when the bunch lengths are 1.5, 2.1, 3.0, 4.0 mm, the injection apertures (leading to 30% loss) are 1.8, 1,6, 1.2, 1.0 sigma of transverse size at the beginning of the sector respectively. For the long bunches, the nominal 20% of beam size transverse pulse to pulse jitter causes an additional 3% loss. Also the bunch energy spread is more sensitive to the accelerating phase of the RF cavities.
Date: June 1, 1994
Creator: Tian, F.; McCormick, D. & Ross, M.
Partner: UNT Libraries Government Documents Department

Measuring micron size beams in the SLC final focus

Description: A pair of high resolution wire scanners have been built and installed in the SLC final focus. The final focus optics uses a set of de-magnifying telescopes, and an ideal location for a beam size monitor is at one of the magnified image points of the interaction point. The image point chosen for these scanners is in the middle of a large bend magnet. The design beam spots here are about 2 microns in the vertical and 20 microns in the horizontal plane. The scanners presented a number of design challenges. In this paper we discuss the mechanical design of the scanner, and fabrication techniques of its ceramic wire support card which holds many 4 and 7 um carbon wires. Accurate motion of the wire during a scan is critical. In this paper we describe tests of stepper motors, gear combinations, and radiation hardened encoders needed to produce the required motion with a step resolution of 80 nanometers. Also presented here are the results of scattered radiation detector placement studies carried out to optimize the signal from the 4 micron wires. Finally, we present measurements from the scanner.
Date: October 1, 1994
Creator: McCormick, D.; Ross, M. & DeBarger, S.
Partner: UNT Libraries Government Documents Department

Observation and Characterization of Coherent Optical Radiation and Microbunching Instability in the SLAC Next Linear Collider Test Accelerator

Description: The NLC Test Accelerator (NLCTA) at SLAC is currently configured for a proof-of-principle echo-enabled harmonic generation (EEHG) experiment using an 120 MeV beam. During commissioning, unexpected coherent optical undulator radiation (CUR) and coherent optical transition radiation (COTR) was observed when beam is accelerated off-crest and compressed after the chicanes. The CUR and COTR is likely due to a microbunching instability where the initial small ripples in cathode drive laser is compressed and amplified. In this paper we present the observation and characterization of the CUR, COTR and microbunching instability at NLCTA.
Date: June 2, 2011
Creator: Weathersby, S.; Dunning, M.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J. et al.
Partner: UNT Libraries Government Documents Department

Wire scanners for beam size and emittance measurements at the SLC

Description: The SLC wire scanner beam profile monitors provide accurate beam size and emittance measurements for each bunch in the three bunch SLC beam. The beam size measurement error for typical 50GeV SLC linac beams (100{mu}m {sigma}({sub x,y})) is better than 5{mu}m. Beam profile measurements can be performed throughout much of the SLC with no interruption to normal machine operation and no adverse impact on interaction region detector backgrounds. The linac input and output emittance is determined using sets of four scanners spaced by {approximately}45{degrees} betatron phase advance. Each scanner contains three wires, x, y and u (45{degrees}), from which an estimate of the x-y coupling can be obtained. Advanced high level control software allows the use of wire scanner data in feedback and beam optimization procedures. Non-invasive scans are performed almost continually and the results are logged so that long term trends in emittance can be examined. In this paper we describe the design, construction, performance and uses of SLC wire scanners. 7 refs., 3 figs., 1 tab.
Date: May 1, 1991
Creator: Ross, M.C.; Seeman, J.T.; Bong, E.; Hendrickson, L.; McCormick, D. & Sanchez-Chopitea, L.
Partner: UNT Libraries Government Documents Department

Observation of Femtosecond Bunch Length Using a Transverse Deflecting Structure

Description: The design of the VUV-FEL at DESY demands bunch lengths in the order of 50 fs and below. For the diagnostic of such very short bunches a transverse deflecting RF structure (LOLA) has been installed which streaks the beam according to the longitudinal distribution. Tests in the VUV-FEL yielded a rich substructure of the bunches. The most pronounced peak in the has a rms length of approximately 50 fs during FEL operation and below 20 fs FWHM at maximum compression. Depending on the transverse focusing a resolution well below 50 fs was achieved.
Date: December 14, 2005
Creator: Huning, M.; Bolzmann, A.; Schlarb, H.; /DESY; Frisch, J.; McCormick, D. et al.
Partner: UNT Libraries Government Documents Department

Optimization of Beam Injection Into the First Accelerating Module at TTF With Cavity Dipole Mode Signals

Description: The TESLA Test Facility (TTF) is a user facility for intense VUV-FEL light. The facility is densely equipped with diagnostics, essential in obtaining the necessary beam parameters, in particular the low emittance. However there is no dedicated component for alignment of the beam in the accelerating modules, each containing eight superconducting cavities. Large beam offsets can lead to an increase of the beam emittance. The centering of the beam in these modules is therefore important, mostly at the low energy end. A misalignment of the first TTF module with respect to the gun axis has already been observed using cavity dipole modes. This paper presents the experimental results of the optimization of the beam injection into the first module, based on the monitoring of dipole modes through the couplers installed for wakefield damping. For this we use a spectrum analyzer together with a multiplexer. By scanning the beam position and tilt with two pairs of steerers, we can find the trajectory which minimizes the dipole modes amplitude. The impact of the beam steering in the module on the beam is discussed. A time domain setup is also being presented.
Date: April 10, 2006
Creator: Baboi, N.; Kreps, G.; Schlarb, H.; Wendt, M.; Frisch, J.; McCormick, D. et al.
Partner: UNT Libraries Government Documents Department

Changes in gene expression following EMF exposure

Description: Experiments were designed to examine the effects of electromagnetic field (EMF) exposure on specific gene expression, an effect that can be deleterious, beneficial, or neutral, depending on the long-term consequences; however, the proof of a reproducible, quantitative biological effect (such as change in gene expression) will lead to latter experiments aimed at determining the relative contribution of these changes to cellular consequences. Past work by ourselves and by others has shown that measures of gene expression are extremely sensitive indicators of the cellular and biological effects of ionizing radiation, with transcriptional changes being detected by exposure of cells to doses of {gamma}-rays as low as 0.01 cGy that have no pronounced cellular consequences. On the basis of this work, the authors hypothesized that measures of gene expression will be equally sensitive to EMF effects on cells.
Date: October 1, 1997
Creator: Woloschak, G.E.; Paunesku, T.; Chang-Liu, C.M.; Loberg, L.; Gauger, J. & McCormick, D.
Partner: UNT Libraries Government Documents Department

Using a Fast-Gated Camera for Measurements of Transverse Beam Distributions and Damping Times

Description: 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.
Date: November 1, 1992
Creator: Minty, M.; Brown, R.; Decker, F. J.; Emma, P.; Krejcik, P.; Limberg, T. et al.
Partner: UNT Libraries Government Documents Department

Evidence of High Harmonics from Echo-Enabled Harmonic Generation for Seeding X-ray Free Electron Lasers

Description: Echo-enabled harmonic generation free electron lasers hold great promise for the generation of fully coherent radiation in x-ray wavelengths. Here we report the first evidence of high harmonics from the echo-enabled harmonic generation technique in the realistic scenario where the laser energy modulation is comparable to the beam slice energy spread. In this experiment, coherent radiation at the seventh harmonic of the second seed laser is generated when the energy modulation amplitude is about 2-3 times the slice energy spread. The experiment confirms the underlying physics of echo-enabled harmonic generation and may have a strong impact on emerging seeded x-ray free electron lasers that are capable of generating laserlike x rays which will advance many areas of science.
Date: February 15, 2012
Creator: Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K. et al.
Partner: UNT Libraries Government Documents Department

Using higher order modes in superconducting accelerating cavities for beam monitoring

Description: Dipole modes have been shown to be successful diagnostics for the beam position in superconducting accelerating cavities at the Free Electron Laser in Hamburg (FLASH) facility at DESY. By help of downmixing electronics the signals from the two higher order mode (HOM) couplers mounted on each cavity are monitored. The calibration, based on sigular value decomposition, is more complicated than in standard position monitors. Position like signals based on this calibration are currently being in the process of being included in the control system. A second setup based on digitizing the spectrum from the HOM couplers has been used for monitoring monopole modes. The beam phase with respect to the RF has been thus monitored. The position calibration measurements and phase monitoring made at the FLASH are presented.
Date: January 1, 2006
Creator: Molloy, S.; Baboi, N.; Eddy, N.; Frisch, J.; Hendrickson, L.; Hensler, O. et al.
Partner: UNT Libraries Government Documents Department

Investigations of the Wideband Spectrum of Higher Order Modes Measured on TESLA-style Cavities at the FLASH Linac

Description: Higher Order Modes (HOMs) excited by the passage of the beam through an accelerating cavity depend on the properties of both the cavity and the beam. It is possible, therefore, to draw conclusions on the inner geometry of the cavities based on observations of the properties of the HOM spectrum. A data acquisition system based on two 20 GS/s, 6 GHz scopes has been set up at the FLASH facility, DESY, in order to measure a significant fraction of the HOM spectrum predicted to be generated by the TESLA cavities used for the acceleration of its beam. The HOMs from a particular cavity at FLASH were measured under a range of known beam conditions. The dipole modes have been identified in the data. 3D simulations of different manufacturing errors have been made, and it has been shown that these simulations can predict the measured modes.
Date: June 27, 2007
Creator: Molloy, S.; Adolphsen, C.; Bane, K.; Frisch, J.; Li, Z.; May, J. et al.
Partner: UNT Libraries Government Documents Department

High resolution upgrade of the ATF damping ring BPM system

Description: A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring has been accomplished in its first stage, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R&D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and digital downconversion techniques, digital signal processing, and also tests a new automatic gain error correction schema. The technical concept and realization, as well as preliminary results of beam studies are presented.
Date: May 1, 2008
Creator: Terunuma, N.; Urakawa, J.; /KEK, Tsukuba; Frisch, J.; May, J.; McCormick, D. et al.
Partner: UNT Libraries Government Documents Department