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Some applications of AI (Artificial Intelligence) to the problems of accelerator physics

Description: Failure of orbit correction schemes to recognize betatron oscillation patterns obvious to any machine operator is a good problem with which to analyze the uses of Artificial Intelligence and the roles and relationships of operators, control systems and machines. Because such error modes are very common, their generalization could provide an efficient machine optimization and control strategy. A set of first-order, unitary transformations connecting canonical variables through measured results are defined which can either be compared to design for commissioning or to past results for 'golden orbit' operation. Because these relate directly to hardware variables, the method is simple, fast and direct. It has implications for machine design, controls, monitoring and feedback. Chronological analysis of such machine signatures can predict or provide a variety of information such as mean time to failure, failure modes and fast feedback or feedforward for optimizing figures of merit such as luminosity or current transmission. The use of theoretical and empirical scaling relations for such problems is discussed in terms of various figures of merit, the variables on which they depend as well as their functional dependences.
Date: September 1, 1986
Creator: Higo, T.; Shoaee, H. & Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Modeling large heterogeneous RF structures

Description: Large heterogeneous structures are difficult to model on a numerical grid because of the limitations on computing resources, so that alternate approaches such as equivalent circuits and mode-matching have been developed to treat this problem. This paper will describe the three methods and will analyze a structure representative of the SLAC and JLC detuned structures to compare the efficacy of each approach.
Date: November 1, 1996
Creator: Li, Zenghai; Ko, Kwok; Srinivas, V. & Higo, Toshiyasu
Partner: UNT Libraries Government Documents Department

Status of High Power Tests of Normal Conducting Single-Cell Structures

Description: We report the results of ongoing high power tests of single-cell standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the maximum gradient possibilities for normal-conducting rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures powered by SLACs XL-4 klystron. The mode launchers and structures were manufactured at SLAC and KEK and tested at the SLAC klystron test laboratory.
Date: November 4, 2011
Creator: Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Higashi, Y.; Higo, T. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

High Power Tests of Normal Conducting Single-Cell Structures

Description: We report the results of the first high power tests of single-cell traveling-wave and standing-wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the gradient potential of normal-conducting rf-powered particle beam accelerators. The test setup consists of reusable mode converters and short test structures and is powered by SLAC's XL-4 klystron. This setup was created for economical testing of different cell geometries, cell materials and preparation techniques with short turn-around time. The mode launchers and structures were manufactured at SLAC and KEK and tested in the SLAC Klystron Test Lab.
Date: November 7, 2007
Creator: Dolgashev, V.A.; Tantawi, S.G.; Nantista, C.D.; /SLAC; Higashi, Y.; Higo, T. et al.
Partner: UNT Libraries Government Documents Department

RF Breakdown in Normal Conducting Single-Cell Structures

Description: Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM{sub 01} mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. Simple 2D geometry of the test structures simplifies modeling of the breakdown currents and their thermal effects.
Date: February 22, 2006
Creator: Dolgashev, V.A.; Nantista, C.D.; Tantawi, S.G.; /SLAC; Higashi, Y.; Higo, T. et al.
Partner: UNT Libraries Government Documents Department

Measurement of wakefield suppression in a detuned x-band accelerator structure

Description: Research is underway at SLAC to develop accelerator structures for a next generation linear collider. A full-scale prototype X-band structure has been built in which the dipole mode frequencies were detuned to suppress the long-range transverse wakefield by about two orders of magnitude. To verify that the detuning works as expected, a facility to measure the long-range wakefield, called the Accelerator Structure SETup, or ASSET, was constructed in the SLAC Linear Collider (SLC). This paper presents the results from the measurement of the prototype X-band structure with this facility.
Date: August 1, 1994
Creator: Adolphsen, C.; Bane, K.; Higo, T.; Kubo, K.; Miller, R.; Ruth, R. et al.
Partner: UNT Libraries Government Documents Department

Bunch lengthening in the SLC damping ring

Description: In this paper we present the results of measurements of bunch length and bunch shape as a function of current in the SLC e/sup /minus//damping ring. After extraction, the SLC bunch is compressed by means of an RF compressor and a subsequent high dispersion section. By inserting a video screen at a point of large dispersion and by using the correlation between bunch length and energy spread induced by the compressor, we have measured not only the bunch length but also the longitudinal charge distribution of the bunch in the damping ring as a function of beam intensity. At 3 /times/ 10/sup 10/ particles per bunch with a peak ring RF voltage of 800 KV, the FWHM of the bunch length in the ring doubles over the nominal value. To measure the energy spread of the bunch in the damping ring, the optics of the extraction lines was modified to produce a large dispersion but small horizontal ..beta.. function at the video screen. At 3 /times/ 10/sup 10/ particles per bunch, the relative energy spread in the rings is increased by about 30%. Finally, these data are compared with calculations of bunch lengthening in the SLC damping rings. 8 refs., 6 figs.,
Date: May 1, 1988
Creator: Rivkin, L.; Bane, K.; Chen, P.; Gabella, W.; Higo, T.; Hofmann, A. et al.
Partner: UNT Libraries Government Documents Department

Beam Position Monitoring using the HOM-Signals from a Damped and Detuned Accelerating Structure

Description: The Next and Global Linear Collider (NLC/GLC) designs require precision alignment of the beam in the accelerator structures to reduce short range wakefields. The moderately damped and detuned structures themselves provide suitable higher order mode (HOM) signals to measure this alignment. The modes in the lowest dipole band, whose frequencies range from 14-16 GHz, provide the strongest signals. To determine the position resolution they provide, an NLC/GLC prototype structure that was installed in the ASSET facility of the SLAC Linac was instrumented to downmix and digitize these signals. The beam position within the structure was determined by simultaneously measuring the signals at three frequencies (14.3, 15, 15.7 GHz) corresponding to modes localized at the beginning, the middle and the end of the 60 cm long structure. A resolution of 1 micron was achieved even with 28 dB signal attenuation, which is better than the 5 micron resolution required for the NLC/GLC.
Date: May 17, 2005
Creator: Dobert, S; Adolphsen, C.; Jones, R.; Lewandowski, J.; Li, Z.; Pivi, M. et al.
Partner: UNT Libraries Government Documents Department

Relativistic klystron research for high gradient accelerators

Description: Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron--positron colliders, compact accelerators, and FEL sources. We have attained 200MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our first klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 7 figs.
Date: June 1, 1988
Creator: Allen, M.A.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fowkes, W.R.; Herrmannsfeldt, W.B. et al.
Partner: UNT Libraries Government Documents Department

Relativistic klystron research for linear colliders

Description: Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron-positron colliders, compact accelerators, and FEL sources. We have attained 200 MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our relativistic klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 9 figs., 1 tab.
Date: September 1, 1988
Creator: Allen, M.A.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fant, K.S.; Fowkes, W.R. et al.
Partner: UNT Libraries Government Documents Department

Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/M Range

Description: A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5 x 10{sup -7}/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.
Date: July 3, 2012
Creator: Wang, Juwen; /SLAC; Lewandowski, James; /SLAC; Van Pelt, John; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Optimization of the Low Loss SRF Cavity for the ILC

Description: The Low-Loss shape cavity design has been proposed as a possible alternative to the baseline TESLA cavity design for the ILC main linacs. The advantages of this design over the TESLA cavity are its lower cryogenic loss, and higher achievable gradient due to lower surface fields. High gradient prototypes for such designs have been tested at KEK (ICHIRO) and TJNAF (LL). However, issues related to HOM damping and multipacting still need to be addressed. Preliminary numerical studies of the prototype cavities have shown unacceptable damping factors for some higher-order dipole modes if the typical TESLA HOM couplers are directly adapted to the design. The resulting wakefield will dilute the beam emittance thus reducing the machine luminosity. Furthermore, high gradient tests on a 9-cell prototype at KEK have experienced multipacting barriers although a single LL cell had achieved a high gradient. From simulations, multipacting activities are found to occur in the end-groups of the cavity. In this paper, we will present the optimization results of the end-groups for the Low-Loss designs for effective HOM damping and alleviation of multipacting.
Date: January 18, 2008
Creator: Sekutowicz, J.S.; /DESY; Kneisel, P.; Lab, /Jefferson; Higo, T.; Morozumi, Y. et al.
Partner: UNT Libraries Government Documents Department

Results from the CLIC X-Band Structure Test Program at NLCTA

Description: As part of a SLAC-CERN-KEK collaboration on high gradient X-band structure research, several prototype structures for the CLIC linear collider study have been tested using two of the high power (300 MW) X-band rf stations in the NLCTA facility at SLAC. These structures differ in terms of their fabrication (brazed disks and clamped quadrants), gradient profile (amount by which the gradient increases along the structure, which optimizes efficiency and maximizes sustainable gradient) and HOM damping (use of slots or waveguides to rapidly dissipate dipole mode energy). The CLIC goal in the next few years is to demonstrate the feasibility of a CLIC-ready baseline design and to investigate alternatives that could increase efficiency. This paper summarizes the high gradient test results from NLCTA in support of this effort.
Date: July 6, 2009
Creator: Adolphsen, Chris; Bowden, Gordon; Dolgashev, Valery; Laurent, Lisa; Tantawi, Sami; Wang, Faya et al.
Partner: UNT Libraries Government Documents Department

Advances in X-Band TW Accelerator Structures Operating in the 100 MV/M Regime

Description: A CERN-SLAC-KEK collaboration on high gradient X-band accelerator structure development for CLIC has been ongoing for three years. The major outcome has been the demonstration of stable 100 MV/m gradient operation of a number of CLIC prototype structures. These structures were fabricated using the technology developed from 1994 to 2004 for the GLC/NLC linear collider initiative. One of the goals has been to refine the essential parameters and fabrication procedures needed to realize such a high gradient routinely. Another goal has been to develop structures with stronger dipole mode damping than those for GLC/NLC. The latter requires that the surface temperature rise during the pulse be higher, which may increase the breakdown rate. One structure with heavy damping has been RF processed and another is nearly finished. The breakdown rates of these structures were found to be higher by two orders of magnitude compared to those with equivalent acceleration mode parameters but without the damping features. This paper presents these results together with some of the earlier results from non-damped structures.
Date: July 5, 2012
Creator: Higo, Toshiyasu; /KEK, Tsukuba; Higashi, Yasuo; /KEK, Tsukuba; Matsumoto, Shuji; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department

Optimization of the X-Band Structure for the JLC/NLC

Description: In this paper, we present design considerations to address the high gradient, wakefields, and RF efficiency issues for the JLC/NLC structures. We will present the rationale for the choices of phase advance, structure length, structure aperture, and other design aspects in the optimization of the structure. We will study the impact of parameter choices for the JLC/NLC beam environment and discuss approaches being taken for an optimal JLC/NLC structure design.
Date: June 21, 2006
Creator: Li, Z.; Adolphsen, C.; Burke, D.L.; Dolgashev, V.; Jones, R.M.; Miller, R.H. et al.
Partner: UNT Libraries Government Documents Department

Fabrication of DDS-3, an 11.4 GHz damped-detuned structure

Description: A 1.8 m X-band Damped-Detuned Structure (DDS-3) has been fabricated and characterized as part of the structure development program towards a TeV-scale e + e - linear collider. In this joint venture, the copper cells were precision-fabricated by LLNL, diffusion-bonded into a monolithic structure by KEK, and the structure completed and tested by SLAC. The overall process constitutes a baseline for future high-volume structure manufacture.
Date: March 1, 1999
Creator: Adolphsen, C; Asano, K; Elmer, J; Funchasi, Y; Higashi, Y; Higo, T et al.
Partner: UNT Libraries Government Documents Department

Relativistic klystron research at SLAC and LLNL

Description: We are developing relativistic klystrons as a power source for high gradient accelerator applications such as large linear electron-positron colliders and compact accelerators. We have attained 200 MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here briefly on our experiments so far. 5 refs., 1 fig., 1 tab.
Date: June 1, 1988
Creator: Allen, M.A.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fowkes, W.R.; Herrmannsfeldt, W.B. et al.
Partner: UNT Libraries Government Documents Department