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LHC INTERACTION REGION QUADRUPOLE ERROR IMPACT STUDIES

Description: The performance of the Large Hadron Collider (LHC) at collision energy is limited by the field quality of the interaction region (IR) quadrupoles and dipoles. In this paper the authors study the impact of the expected field errors of these magnets on the dynamic aperture. The authors investigate different magnet arrangements and error strength. Based on the results they propose and evaluate a corrector layout to meet the required dynamic aperture performance in a companion paper.
Date: September 7, 1999
Creator: FISCHER,W.; PTITSIN,V. & WEI,J.
Partner: UNT Libraries Government Documents Department

LHC INTERACTION REGION CORRECTION SCHEME STUDIES

Description: In a companion paper the authors showed that the performance of the Large Hadron Collider (LHC) at collision energy is limited by the field quality of the interaction region quadrupoles and dipoles. In this situation, the dynamic aperture can be increased through local multipole correctors. Since the betatron phase advance is well defined for magnets that are located in regions of large beta functions, local corrections can be very effective and robust. They compare possible compensation schemes and propose a corrector layout to meet the required dynamic aperture performance.
Date: September 7, 1999
Creator: FISCHER,W.; PTITSIN,V. & WEI,J.
Partner: UNT Libraries Government Documents Department

LHC INTERACTION REGION CORRECTION IN HEAVY ION OPERATION

Description: In heavy ion operation the LHC interaction region at IP2 will have a low-{beta} optics for collisions. The dynamic aperture is therefore sensitive to magnetic field errors in the interaction region quadrupoles and dipoles. The authors investigate the effect of the magnetic field errors on the dynamic aperture and evaluate the effectiveness of local interaction region correctors. The dynamic aperture and the tune space are computed for different crossing angles.
Date: September 7, 1999
Creator: PTITSIN,V.; FISCHER,W. & WEI,J.
Partner: UNT Libraries Government Documents Department

PRINCIPLE OF INTERACTION REGION LOCAL CORRECTION

Description: For hadron storage rings like the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), the machine performance at collision is usually limited by the field quality of the interaction region (IR) magnets. A robust local correction for the IR region is valuable in improving the dynamic aperture with practically achievable magnet field quality. The authors present in this paper the action-angle kick minimization principle on which the local IR correction for both RHIC and the LHC are based.
Date: September 7, 1999
Creator: WEI,J.
Partner: UNT Libraries Government Documents Department

Time Evolution of Beam in the Recycler Ring

Description: We study the time evolution of the beam current in the Fermilab Recycler Ring due to abrupt physical processes (single coulomb scattering, nuclear scattering) that cause sudden loss of beam, and diffusive processes (multiple coulomb scattering, lattice dependence, etc.) which cause emittance growth. This emittance growth combined with finite aperture of the beam pipe will lead to eventual loss of most beam. We develop a fitting technique to the time evolution of beam current to estimate emittance growth. Finally we compare the directly measured growth with the fitted value.
Date: May 7, 2003
Creator: Krish Gounder, John Marriner and Shekhar Mishra
Partner: UNT Libraries Government Documents Department

The Physics of the Gas Attenuator for the Linac Coherent Light Source (LCLS)

Description: A systematic assessment of a variety of physics issues affecting the performance of the LCLS X-ray beam attenuator is presented. Detailed analysis of the gas flow in the gas attenuator and in the apertures is performed. A lot of attention is directed towards the gas ionization and heating by intense X-ray pulses. The role of these phenomena in possible deviations of the attenuation coefficient from its 'dialed in' value is evaluated and found small in most cases. Other sources of systematic and statistical errors are also discussed. The regimes where the errors may reach a few percent correspond to the lower X-ray energies (less than 2 keV) and highest beam intensities. Other effects discussed include chemical interaction of the gas with apertures, shock formation in the transonic flow in the apertures of the attenuator, generation of electromagnetic wakes in the gas, and head-to-tail variation of the attenuation caused by the ionization of gas or solid. Possible experimental tests of the consistency of the physics assumptions used in the concept of the gas attenuator are discussed. Interaction of X-rays with the solid attenuator (that will be used at higher X-ray energies, from 2.5 to 8 keV) is considered and thermo-mechanical effects caused by the beam heating are evaluated. Wave-front distortions induced by non-uniform heating of both the solid and the gas are found to be small. An overall conclusion drawn from the analysis presented is that the attenuator will be a reliable and highly versatile device, provided that some caution is exercised in its use for highest beam intensities at lowest X-ray energies.
Date: February 7, 2011
Creator: Ryutov, D.D.; Bionta, R.M.; Hau-Riege, S.P.; Kishiyama, K.I.; McMahon, D.; Roeben, M.D. et al.
Partner: UNT Libraries Government Documents Department

The Full Aperture Backscatter Station Measurement System on the National Ignition Facility

Description: A Full Aperture Backscatter Station (FABS) target diagnostic has been activated on the first four beams of the National Ignition Facility (NIF). Backscattered light from the target propagates back down the beam path into the FABS diagnostic system. FABS measures both stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) with a suite of measurement instruments. Digital cameras and spectrometers record spectrally resolved energy for both P and S polarized light. Streaked spectrometers measure the spectral and temporal behavior of the backscattered light. Calorimeters and fast photodetectors measure the integrated energy and temporal behavior of the light, respectively. This paper provides an overview of the FABS measurements system and detailed descriptions of the diagnostic instruments and the optical path.
Date: April 7, 2004
Creator: Bower, D; McCarville, T; Alvarez, S; Ault, L; Brown, M; Chrisp, M et al.
Partner: UNT Libraries Government Documents Department

Differential Synthetic Aperture Ladar

Description: We report a differential synthetic aperture ladar (DSAL) concept that relaxes platform and laser requirements compared to conventional SAL. Line-of-sight translation/vibration constraints are reduced by several orders of magnitude, while laser frequency stability is typically relaxed by an order of magnitude. The technique is most advantageous for shorter laser wavelengths, ultraviolet to mid-infrared. Analytical and modeling results, including the effect of speckle and atmospheric turbulence, are presented. Synthetic aperture ladars are of growing interest, and several theoretical and experimental papers have been published on the subject. Compared to RF synthetic aperture radar (SAR), platform/ladar motion and transmitter bandwidth constraints are especially demanding at optical wavelengths. For mid-IR and shorter wavelengths, deviations from a linear trajectory along the synthetic aperture length have to be submicron, or their magnitude must be measured to that precision for compensation. The laser coherence time has to be the synthetic aperture transit time, or transmitter phase has to be recorded and a correction applied on detection.
Date: February 7, 2005
Creator: Stappaerts, E A & Scharlemann, E
Partner: UNT Libraries Government Documents Department

LCLS Spontaneous Radiation with Reflection along the Beam Line in the Undulator Pipes

Description: Some commissioning and alignment procedures for XTOD may rely on the use of the spontaneous radiation. Therefore we have modeled the spontaneous radiation between the Undulator and the Near Experimental Hall to derive numerical values of the expected beam width and of the energy deposition. The values are then used to determine aperture sizes and detector sensitivities. We performed the calculations in three stages. The first was to generate an appropriate distribution of photons within the Undulator. The second was to simulate the emergence of the photons from the Undulator. The third was to propagate the photons (without any obstructing objects) to various points along the Z-axis up to the Near Experimental Hall entrance. We performed the simulations for low and high energies based on the spectral flux data supplied by Sven Reiche. These data sets were at 71 meters from the end of the Undulator for 4.5 and 14.08 GeV electrons.
Date: September 7, 2005
Creator: Fong, K W
Partner: UNT Libraries Government Documents Department

CMAD: A Self-consistent Parallel Code to Simulate the Electron Cloud Build-up and Instabilities

Description: We present the features of CMAD, a newly developed self-consistent code which simulates both the electron cloud build-up and related beam instabilities. By means of parallel (Message Passing Interface - MPI) computation, the code tracks the beam in an existing (MAD-type) lattice and continuously resolves the interaction between the beam and the cloud at each element location, with different cloud distributions at each magnet location. The goal of CMAD is to simulate single- and coupled-bunch instability, allowing tune shift, dynamic aperture and frequency map analysis and the determination of the secondary electron yield instability threshold. The code is in its phase of development and benchmarking with existing codes. Preliminary results on benchmarking are presented in this paper.
Date: November 7, 2007
Creator: Pivi, M. T. F.
Partner: UNT Libraries Government Documents Department

Advanced 0.3-NA EUV lithography capabilities at the ALS

Description: For volume nanoelectronics production using Extreme ultraviolet (EUV) lithography [1] to become a reality around the year 2011, advanced EUV research tools are required today. Microfield exposure tools have played a vital role in the early development of EUV lithography [2-4] concentrating on numerical apertures (NA) of 0.2 and smaller. Expected to enter production at the 32-nm node with NAs of 0.25, EUV can no longer rely on these early research tools to provide relevant learning. To overcome this problem, a new generation of microfield exposure tools, operating at an NA of 0.3 have been developed [5-8]. Like their predecessors, these tools trade off field size and speed for greatly reduced complexity. One of these tools is implemented at Lawrence Berkeley National Laboratory's Advanced Light Source synchrotron radiation facility. This tool gets around the problem of the intrinsically high coherence of the synchrotron source [9,10] by using an active illuminator scheme [11]. Here we describe recent printing results obtained from the Berkeley EUV exposure tool. Limited by the availability of ultra-high resolution chemically amplified resists, present resolution limits are approximately 32 nm for equal lines and spaces and 27 nm for semi-isolated lines.
Date: July 7, 2005
Creator: Naulleau, Patrick; Anderson, Erik; Dean, Kim; Denham, Paul; Goldberg, Kenneth A.; Hoef, Brian et al.
Partner: UNT Libraries Government Documents Department

Single shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution

Description: We have demonstrated near-wavelength resolution microscopy in the extreme ultraviolet. Images of 50 nm diameter nanotubes were obtained with a single {approx}1 ns duration pulse from a desk-top size 46.9 nm laser. We measured the modulation transfer function of the microscope for three different numerical aperture zone plate objectives, demonstrating that 54 nm half-period structures can be resolved. The combination of near-wavelength spatial resolution and high temporal resolution opens myriad opportunities in imaging, such as the ability to directly investigate dynamics of nanoscale structures.
Date: January 7, 2008
Creator: Jones, Juanita; Brewer, Courtney A.; Brizuela, Fernando; Wachulak, Przemyslaw; Martz, Dale H.; Chao, Weilun et al.
Partner: UNT Libraries Government Documents Department

A Review of Antiproton Source Studies, 1991

Description: The following is a list of studies which were performed in the Antiproton Source in 1991. They are listed in chronological order and this order does not reflect their relative importance. (1) Antiprotons were stacked to a record 120 mA stack to try and see if any fundamental limitations existed to stack size at this level. None were found. The production efficiency was measured as a function of stack size, as a benchmark for future improvements. The effects of ion clearing and beam shaking were studied. Beam shaking was found to be necessary at large stack sizes in order to maintain reasonable emittances, as expected. (2) The transverse emittance monitors in the Accumulator were recalibrated using the above large stack. There is still some suspicion that these monitors are not correctly calibrated. (3) The Debuncher transverse aperture was measured and significant efforts were made to improve it. The aperture is still not optimized for large {Delta}P/P. (4) A large amount of time was dedicated to developing the Accumulator magnet ramp tables for E760 decelerations. (5) The Accumulator {beta} functions were measured at several different energies and several different lattice points. These measurements were required for E760 beam energy measurements. (6) The ARF3 (H=2) Rf cavity was calibrated and this cavity was used to measure the lattice parameter {eta} at different energies. This was required for E760 to extract beam momentum width measurements from beam frequency measurements. (7) The radiation levels at the AP0 target hall were measured as part of the site-wide effort to eliminate possible radiation hazards. Significant radiation levels were measured, and remedial action was taken. (8) The Debuncher TBT orbit measurement system was recommissioned and properly documented (after several years of neglect). (9) Initial beam tests were made of a quadrupole pickup amplifier prototype. A quadrupole pickup ...
Date: February 7, 1992
Creator: Church, M.
Partner: UNT Libraries Government Documents Department

The dependence of the anisoplanatic Strehl of a compensated beam on the beacon distribution

Description: There are several applications for lasers where the effect of atmospheric turbulence is strong enough to require wavefront compensation, and the compensation can be made by an adaptive optics (AO) system which processes light returned from the target itself. The distribution of the target return light produces limitations to the performance of the AO system. The primary intent of this documentation is to present the new results of an analysis of the anisoplanatic effects arising from target return beacon geometries. It will also lay out the assumptions and steps in the analysis, so that the results can be validated or extended. The intent is to provide a self-consistent notation, simple physical interpretations of the mathematical formulations, and enough detail to reduce the investment of time required to become acquainted or reacquainted with the physics of laser propagation through turbulence, at a level needed to analyze anisoplanatic effects. A general formulation has been developed to calculate the anisoplanatic Strehl of a compensated beam for any beacon distribution and turbulence profile. Numerical calculations are also shown for several beacon geometries and turbulence profiles. The key result is that the spread of the beacon distribution has a much less deleterious effect than does the offset of the beacon centroid from the aimpoint.
Date: February 7, 1992
Creator: Stroud, P.
Partner: UNT Libraries Government Documents Department

The Dependence of the Anisoplanatic Strehl of a Compensated Beam on the Beacon Distribution. Final Report

Description: There are several applications for lasers where the effect of atmospheric turbulence is strong enough to require wavefront compensation, and the compensation can be made by an adaptive optics (AO) system which processes light returned from the target itself. The distribution of the target return light produces limitations to the performance of the AO system. The primary intent of this documentation is to present the new results of an analysis of the anisoplanatic effects arising from target return beacon geometries. It will also lay out the assumptions and steps in the analysis, so that the results can be validated or extended. The intent is to provide a self-consistent notation, simple physical interpretations of the mathematical formulations, and enough detail to reduce the investment of time required to become acquainted or reacquainted with the physics of laser propagation through turbulence, at a level needed to analyze anisoplanatic effects. A general formulation has been developed to calculate the anisoplanatic Strehl of a compensated beam for any beacon distribution and turbulence profile. Numerical calculations are also shown for several beacon geometries and turbulence profiles. The key result is that the spread of the beacon distribution has a much less deleterious effect than does the offset of the beacon centroid from the aimpoint.
Date: February 7, 1992
Creator: Stroud, P.
Partner: UNT Libraries Government Documents Department