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in creator/contributor: "Akre, R."

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Realization of an X-Band RF System for LCLS

A single X-band (11.424 GHz) accelerating structure is to be incorporated in the LINAC Coherent Light Source (LCLS) design to linearize the energy-time correlation (or gradient) across each bunch; features which originate in the preceding accelerating structures (L0 and L1) [1]. This harmonic RF system will operate near the negative RF crest to decelerate the beam, reducing these non-linear components of the correlation, providing a more efficient compression in the downstream bunch compressor … more

Date: June 15, 2005

Creator: McIntosh, P.; Akre, R.; Brooks, W.; Emma, P. & Rago, C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Operating experience with high beam currents and transient beam loading in the SLC damping rings

During the 1994 SLC run the nominal operating intensity in the damping rings was raised from 3.5 {times} 10{sup 10} to greater than 4 {times} 10{sup 10} particles per bunch (ppb). Stricter regulation of rf system parameters was required to maintain stability of the rf system and particle beam. Improvements were made in the feedback loops which control the cavity amplitude and loading angles. Compensation for beam loading was also required to prevent klystron saturation during repetition rate ch… more

Date: June 1, 1995

Creator: Minty, M. G.; Akre, R.; Krejcik, P. & Siemann, R. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Injection Related Background due to the Transverse Feedback

The background in the BaBar detector is especially high during injection, when most components are actually having reduced voltages. The situation is worse for the beam in High Energy Ring (HER) when the LER beam is present. It was found that the transverse feedback system plays an important role when stacking more charge on top of existing bunches. Lowering the feedback gain helped and it was realized later that the best scenario would be to gate off the feedback for only the one bunch, which … more

Date: March 18, 2008

Creator: Decker, F. J.; Akre, R.; Fisher, A.; Iverson, R. & Weaver, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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PEP-II Transverse Feedback Electronics Upgrade

The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system i… more

Date: March 13, 2006

Creator: Weber, J. M.; Chin, M. J.; Doolittle, L. R. & Akre, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Overview of the RF Systems for LCLS

The Linac Coherent Light Source (LCLS) at SLAC, when it becomes operational in 2009, will provide its user community with an X-ray source many orders of magnitude brighter than anything available in the world at that time [1]. The electron beam acceleration will be provided by existing and new RF systems capable of maintaining the amplitude and phase stability of each bunch to extremely tight tolerances. RF feedback control of the various RF systems will be fundamental in ensuring the beam arri… more

Date: June 15, 2005

Creator: McIntosh, P.; Akre, R.; Boyce, R.; Emma, P.; Hill, A. & Rago, C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A Solid-State Nanosecond Beam Kicker Modulator Based on the DSRD Switch

A fast solid-state beam kicker modulator is under development at the SLAC National Accelerator Laboratory. The program goal is to develop a modulator that will deliver 4 ns, {+-}5 kV pulses to the ATF2 damping ring beam extraction kicker. The kicker is a 50 {Omega}, bipolar strip line, 60 cm long, fed at the downstream end and terminated at the upstream end. The bunch spacing in the ring is 5.6 ns, bunches are removed from the back end of the train, and there is a gap of 103.6 ns before the nex… more

Date: August 19, 2011

Creator: Akre, R.; Benwell, A.; Burkhart, C.; Krasnykh, A.; Tang, T. & Kardo-Sysoev, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Design and Testing of Gproto Bunch-by-bunch Signal Processor

A prototype programmable bunch-by-bunch signal acquisition and processing channel with multiple applications in storage rings has been developed at SLAC. The processing channel supports up to 5120 bunches with bunch spacings as close as 1.9 ns. The prototype has been tested and operated in five storage rings: SPEAR-3, DAINE, PEP-II, KEKB, and ATF damping ring. The testing included such applications as transverse and longitudinal coupled-bunch instability control, bunch-by-bunch luminosity monit… more

Date: July 18, 2006

Creator: Teytelman, D.; Rivetta, C.; Van Winkle, D.; Akre, R.; Fox, J. & Krasnykh, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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PEP-II Transverse Feedback Electronics Upgrade

Date: May 9, 2005

Creator: Weber, J.; Chin, M.; Doolittle, L. & Akre, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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LCLS LLRF Upgrades to the SLAC Linac

The Linac Coherent Light Source (LCLS) at SLAC will be the brightest X-ray laser in the world when it comes on line. In order to achieve the brightness a 200fS length electron bunch is passed through an undulator. To create the 200fS, 3kA bunch, a 10pS electron bunch, created from a photo cathode in an RF gun, is run off crest on the RF to set up a position to energy correlation. The bunch is then compressed by chicanes. The stability of the RF system is critical in setting up the position to e… more

Date: October 4, 2007

Creator: Akre, R.; Dowell, D.; Emma, P.; Frisch, J.; Hong, B.; Kotturi, K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Effects of temperature variation on the SLC linac RF system

The rf system of the Stanford Linear Collider in California is subjected to daily temperature cycles of up to 15{degrees}C. This can result in phase variations of 15{degrees} at 3 GHz over the 3 km length of the main drive line system. Subsystems show local changes of the order of 3{degrees} over 100 meters. When operating with flat beams and normalized emittances of 0.3*10{sup {minus}5} m-rad in the vertical plane, changes as small as 0.5{degrees} perturb the wakefield tail compensation and ma… more

Date: June 1, 1995

Creator: Decker, F. J.; Akre, R.; Byrne, M.; Farkas, Z. D.; Jarvis, H.; Jobe, K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Recent Measurements And Plans for the SLAC Compton X-Ray Source

A compact source of monoenergetic X-rays, generated via Compton backscattering, has been developed in a collaboration between U.C Davis and SLAC. The source consists of a 5.5 cell X-band photoinjector, a 1.05 m long high gradient accelerator structure and an interaction chamber where a high power (TW), short pulse (sub-ps) infrared laser beam is brought into a nearly head-on collision with a high quality focused electron beam. Successful completion of this project will result in the capability … more

Date: February 14, 2006

Creator: Vlieks, A. E.; Akre, R.; Caryotakis, G.; DeStefano, C.; Frederick, W. J.; Heritage, J. P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-Current Effects in The PEP-II Storage Rings

High beam currents in PEP-II have been a challenge for vacuum system and ring components. For the {approx} 1 cm long bunches peak currents exceed 100 A and modest impedance can give rise to voltage spikes and discharges. During the last two runs, difficulties arose from rf seals at the 'flex flanges' in the HER. High temperatures were seen and the seals turned out to be severely damaged by discharges. In the LER, the horizontal stripline kickers of the bunch-by-bunch feedback system experiences… more

Date: June 19, 2009

Creator: Wienands, U.; Sullivan, M. K.; Akre, R.; Cheng, W.; Colocho, W.; DeBarger, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Commissioning the LCLS Injector

The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam was completed in August 2007, with the goal of a 1.2-micron emittance in a 1-nC bunch clearly demonstrated. The second phase of commissioning, including second bunch compressor and full lina… more

Date: November 28, 2007

Creator: Akre, R.; Dowell, D.; Emma, P.; Frisch, J.; Gilevich, S.; Hays, G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Tracking Down a Fast Instability in the PEP-II LER

During Run 5, the beam in the PEP-II Low Energy Ring (LER) became affected by a predominantly vertical instability with very fast growth rate of 10...60/ms and varying threshold. The coherent amplitude of the oscillation was limited to approx. 1 mm peak and would damp down over a few tens of turns, however, beam loss set in even as the amplitude signal damped, causing a beam abort. This led to the conclusion that the bunches were actually blowing up. The appearance of a 2{nu}{sub S} line in the… more

Date: May 18, 2007

Creator: Wienands, U.; Akre, R.; Curry, S.; DeBarger, S.; Decker, F. J.; Ecklund, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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RF Gun Photo cathode Research at SLAC

LCLS is presently operating with a third copper photocathode in the original rf gun, with a quantum efficiency (QE) of {approx}1 x 10{sup -4} and projected emittance {gamma}{var_epsilon}{sub x,y} = 0.45 {micro}m at 250 pC bunch charge. The spare LCLS gun is installed in the SLAC Accelerator Structure Test Area (ASTA), fully processed to high rf power. As part of a wider photocathode R and D program, a UV laser system and additional gun diagnostics are being installed at ASTA to measure QE, QE l… more

Date: May 16, 2012

Creator: Jongewaard, E.; Akre, R.; Brachmann, A.; Corbett, J.; Gilevich, S.; Grouev, K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Commissioning Results of the LCLS Injector

The Linac Coherent Light Source (LCLS) is a SASE xray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive-laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam has recently been completed. The second phase of construction, including second bunch compressor and full linac, is planned for 2008. In this paper, we report experimental results and experie… more

Date: November 16, 2007

Creator: Dowell, D. H.; Akre, R.; Ding, Y.; Emma, P.; Frisch, J.; Gilevich, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Initial Commissioning Experience With the LCLS Injector

The Linac Coherent Light Source (LCLS) is a SASE xray Free-Electron Laser (FEL) project presently under construction at SLAC [1]. The injector section, from drive-laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam is taking place during the spring and summer of 2007. The second phase of construction, including second bunch compressor and full linac, will begin later, in the fall of 2007. We report … more

Date: November 2, 2007

Creator: Akre, R.; Castro, J.; Ding, Y.; Dowell, D. H.; Emma, P.; Frisch, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Commissioning of the LCLS Linac and Bunch Compressors

The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project under construction at SLAC [1]. The injector section, from drive-laser and RF photocathode gun through the first bunch compressor, was commissioned in the spring and summer of 2007. The second phase of commissioning, including the second bunch compressor and various main linac modifications, was completed in January through August of 2008. We report here on experience gained during this second phase of mach… more

Date: August 20, 2008

Creator: Akre, R.; Brachmann, A.; Decker, F.-J.; Ding, Y.; Dowell, D.; Emma#, P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Observation of Coherent Optical Transition Radiation in the LCLS Linac

The beam diagnostics in the linac for the Linac Coherent Light Source (LCLS) X-ray FEL project at SLAC includes optical transition radiation (OTR) screens for measurements of transverse and longitudinal beam properties. We report on observations of coherent light emission from the OTR screens (COTR) at visible wavelengths from the uncompressed and compressed electron beam at various stages in the accelerator.

Date: September 18, 2008

Creator: Loosy, H.; Akre, R.; Brachmann, A.; Decker, F. J.; Ding, Y.; Dowell, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Operational Performance of LCLS Beam Instrumentation

The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been operational since April 2009 and finished its first successful user run last December. The various diagnostics for electron beam properties including beam position monitors, wire scanners, beam profile monitors, and bunch length diagnostics are presented as well as diagnostics for the X-ray beam. The low emittance and ultra-short electron beam required for X-ray FEL operation has implications on th… more

Date: June 15, 2010

Creator: Loos, Henrik; Akre, R.; Brachmann, A.; Coffee, R.; Decker, F. J.; Ding, Y. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Beam Measurements at LCLS

No Description Available.

Date: May 9, 2012

Creator: Frisch, J.; Akre, R.; Decker, F. J.; Ding, Y.; Dowell, D.; Emma, P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Commissioning of the LCLS LINAC

The Linac Coherent Light Source (LCLS) X-ray free electron laser project is currently under construction at the Stanford Linear Accelerator Center (SLAC). A new injector and upgrades to the existing accelerator were installed in two phases in 2006 and 2007. We report on the commissioning of the injector, the two new bunch compressors at 250MeV and 4.3 GeV, and transverse and longitudinal beam diagnostics up to the end of the existing linac at 13.6 GeV. The commissioning of the new transfer line… more

Date: June 11, 2010

Creator: Loos, H.; Akre, R.; Brachmann, A.; Decker, F. J.; Ding, Y.; Dowell, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Carrier-Density-Dependent Lattice Stability in InSb

No Description Available.

Date: May 11, 2007

Creator: Hillyard, P. B.; Gaffney, K. J.; Lindenberg, A. M.; Engemann, S.; Akre, R. A.; Arthur, J. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department