92 Matching Results

Search Results

Advanced search parameters have been applied.

Emittance measurements using Vernier Scans during Run 09 (pp at 250 GeV)

Description: Emittance measurements using the vernier scan technique give reliable results for 250 GeV protons even though the transverse beam profiles have non-Gaussian tails. Those non-Gaussian tails were observed for the first time this run at the 250 GeV beam energy. The vernier scan measurements are in excellent agreement with the emittances derived from collision rates and show practically no fill to fill scatter if compared to the latter. The results are consistent with a {beta}* of 0.7 m and round beams. The IPM measurements show a discrepancy of up to 80% compared with the vernier scan data and a fill to fill scatter of up to 30%. If an uncertainty in the beta-function at the location of the IPM is the root cause, this uncertainty seems to be quite large. In any case, such an uncertainty could not explain the fill to fill variations of up to 30% which indicate yet another underlying reason that could explain fill to fill variations (candidates could be beam intensity issues with the IPM, beam position at the IPM, varying background etc.).
Date: November 1, 2010
Creator: Drees, A.
Partner: UNT Libraries Government Documents Department

A new luminescence beam profile monitor for intense proton and heavy ion beams

Description: A new luminescence beam profile monitor is realized in the polarized hydrogen gas jet target at the Relativistic Heavy Ion Collider (RHIC) facility. In addition to the spin polarization of the proton beam being routinely measured by the hydrogen gas jet, the luminescence produced by beam-hydrogen excitation leads to a strong Balmer series lines emission. A selected hydrogen Balmer line is spectrally filtered and imaged to produce the transverse RHIC proton beam shape with unprecedented details on the RHIC beam profile. Alternatively, when the passage of the high energy RHIC gold ion beam excited only the residual gas molecules in the beam path, sufficient ion beam induced luminescence is produced and the transverse gold ion beam profile is obtained. The measured transverse beam sizes and the calculated emittances provide an independent confirmation of the RHIC beam characteristics and to verify the emittance conservation along the RHIC accelerator. This optical beam diagnostic technique by making use of the beam induced fluorescence from injected or residual gas offers a truly noninvasive particle beam characterization, and provides a visual observation of proton and heavy ion beams. Combined with a longitudinal bunch measurement system, a 3-dimensional spatial particle beam profile can be reconstructed tomographically.
Date: October 1, 2008
Creator: Tsang,T.; Bellavia, S.; Connolly, R.; Gassner, D.; Makdisi, Y.; Russo, T. et al.
Partner: UNT Libraries Government Documents Department

Modification of Particle Distributions By MHD Instabilities I

Description: The modification of particle distributions by low amplitude magnetohydrodynamic modes is an important topic for magnetically confined plasmas. Low amplitude modes are known to be capable of producing significant modification of injected neutral beam profiles, and the same can be expected in burning plasmas for the alpha particle distributions. Flattening of a distribution due to phase mixing in an island or due to portions of phase space becoming stochastic is a process extremely rapid on the time scale of an experiment but still very long compared to the time scale of guiding center simulations. Thus it is very valuable to be able to locate significant resonances and to predict the final particle distribution produced by a given spectrum of magnetohydrodynamic modes. In this paper we introduce a new method of determining domains of phase space in which good surfaces do not exist and use this method for quickly determining the final state of the particle distribution without carrying out the full time evolution leading to it.
Date: December 23, 2010
Creator: White, R. B.
Partner: UNT Libraries Government Documents Department

Modification of Particle Distributions by MHD Instabilities II

Description: The modification of particle distributions by low amplitude magnetohydrodynamic modes is an important topic for magnetically confined plasmas. Low amplitude modes are known to be capable of producing significant modification of injected neutral beam profiles, and the same can be expected in burning plasmas for the alpha particle distributions. Flattening of a distribution in an island due to phase mixing and portions of phase space becoming stochastic lead to modification of the particle distribution, a process extremely rapid in the time scale of an experiment but still very long compared to the time scale of guiding center simulations. Large amplitude modes can cause profile avalanche and particle loss. Thus it is very valuable to be able to predict the temporal evolution of a particle distribution produced by a given spectrum of magnetohydrodynamic modes. In this paper we further develop and investigate the use of a new method of determining domains of phase space in which good KAM surfaces do not exist and use this method to examine a well documented case of profile modification by instabilities.
Date: March 2, 2011
Creator: White, Roscoe B.
Partner: UNT Libraries Government Documents Department

DML and Foil Measurements of ETA Beam Radius

Description: Simultaneous measurements of the ETA beam radius have been made with a quartz foil and a diamagnetic loop (DML). While the measurements agreed at some settings they diverged at others. While the DML measures the rms radius of the total beam, the foil measures mainly the core and the divergence can be explained by the presence of a low density halo. Evidence of such a halo from other measurements is presented.
Date: May 11, 2005
Creator: Nexsen, W & Weir, J
Partner: UNT Libraries Government Documents Department

A Design Report for the Optical Transition Radiation Imager for the LCLS Undulator

Description: The Linac Coherent Light Source (LCLS), a free-electron x-ray laser, is under design and construction. Its high-intensity electron beam, 3400 A in peak current and 46 TW in peak power, is concentrated in a small area (37 micrometer in rms radius) inside its undulator. Ten optical transition radiation (OTR) imagers are planned between the undulator segments for characterizing the transverse profiles of the electron beam. In this note, we report on the optical and mechanical design of the OTR imager. Through a unique optical arrangement, using a near-normal-incidence screen and a multi-layer coated mirror, this imager will achieve a fine resolution (12 micrometer or better) over the entire field of view (8 mm x 5 mm), with a high efficiency for single-shot imaging. A digital camera will be used to read out the beam images in a programmable region (5 mm x 0.5 mm) at the full beam repetition rate (120 Hz), or over the entire field at a lower rate (10 Hz). Its built-in programmable amplifier will be used as an electronic intensity control.
Date: December 13, 2010
Creator: Yang, Bingxin
Partner: UNT Libraries Government Documents Department

Start-to-end Transport Design and Multi-particle Tracking for the ILC Electron Source

Description: A train of 2-ns micro bunches of longitudinally polarized electrons are generated in a 120-kV DC-gun based injector in the ILC electron source; a bunching system with extremely high bunching efficiency to compress the micro-bunch down to 20 ps FWHM is designed. Complete optics to transport the electron bunch to the entrance of the 5-GeV damping ring injection line is developed. Start-to-end multi-particle tracking through the beamline is performed including the bunching system, pre-acceleration, chicane, 5-GeV superconducting booster linac, spin rotators and energy compressor. It shows that 94% of the electrons from the DC-gun are captured within the damping ring 6-D acceptance--A{sub x} + A{sub y} {le} 0.09 m and {Delta}E x {Delta}z {le} ({+-} 25 MeV) x ({+-} 3.46 cm)--at the entrance of the damping ring injection line. The field and alignment errors and orbit correction are analyzed.
Date: February 2, 2007
Creator: Zhou, F.; Batygin, Y.; Brachman, A.; Clendenin, J.; Miller, R.H.; Sheppard, J.C. et al.
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


Description: This technical report evaluates and develops options for reducing the amount of steel in the emplacement drift invert. Concepts developed in the ''Invert Configuration and Drip Shield Interface'' were evaluated to determine material properties required for the proposed invert concepts. Project requirements documents prescribe the use of a carbon steel frame for the invert with a granular material of crushed tuff as ballast. The ''Invert Configuration and Drip Shield Interface'' developed three concepts: (1) All-Ballast Invert; (2) Modified Steel Invert with Ballast; and (3) Steel Tie with Ballast Invert. Analysis of the steel frame members, runway beams, and guide beams, for the modified steel invert with ballast, decreased the quantity of steel in the emplacement drift invert, however a substantial steel support frame for the gantry and waste package/pallet assembly is still required. Use of one of the other two concepts appears to be an alternative to the steel frame and each of the concepts uses considerably less steel materials. Analysis of the steel tie with ballast invert shows that the bearing pressure on the ballast under the single steel tie, C 9 x 20, loaded with the waste package/pallet assembly, drip shield, and backfill exceeds the upper bound of the allowable bearing capacity for tuff used in this study. The single tie, C 10 x 20, will also fail for the same loading condition except for the tie length of 4.2 meters and longer. Analysis also shows that with two ties, C 9 or 10 x 20's, the average ballast pressure is less than the allowable bearing capacity. Distributing the waste package/pallet, drip shield, and backfill loads to two steel ties reduces the contact bearing pressure. Modifying the emplacement pallet end beams to a greater width, reducing the tie spacing, and increasing the width of the ties would ensure ...
Date: September 29, 2000
Creator: Tang, M. E. Taylor and D. H.
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


Description: In FY 1998, following the 50th Anniversary Year of Brookhaven National Laboratory, Brookhaven Science Associates became the new Managers of BNL. The new start is an appropriate time to take stock of past achievements and to renew or confirm future goals. During the 1998 NSLS Annual Users Meeting (described in Part 3 of this Activity Report), the DOE Laboratory Operations Board, Chaired by the Under Secretary for Energy, Ernest Moniz met at BNL. By chance all the NSLS Chairmen except Martin Blume (acting NSLS Chair 84-85) were present as recorded in the picture. Under their leadership the NSLS has improved dramatically: (1) The VUV Ring current has increased from 100 mA in October 1982 to nearly 1 A today. For the following few years 10 Ahrs of current were delivered most weeks - NSLS now exceeds that every day. (2) When the first experiments were performed on the X-ray ring during FY1985 the electron energy was 2 GeV and the current up to 100 mA - the X-Ray Ring now runs routinely at 2.5 GeV and at 2.8 GeV with up to 350 mA of current, with a very much longer beam half-life and improved reliability. (3) Starting in FY 1984 the proposal for the Phase II upgrade, mainly for a building extension and a suite of insertion devices and their associated beamlines, was pursued - the promises were delivered in full so that for some years now the NSLS has been running with two undulators in the VUV Ring and three wigglers and an undulator in the X-Ray Ring. In addition two novel insertion devices have been commissioned in the X13 straight. (4) At the start of FY 1998 the NSLS welcomed its 7000th user - attracted by the opportunity for pursuing research with high quality beams, guaranteed not ...
Date: May 1, 1999
Creator: ROTHMAN,E.
Partner: UNT Libraries Government Documents Department

Particle Distribution Modification by Low Amplitude Modes

Description: Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.
Date: August 28, 2009
Creator: R.B. White, N. Gorelenkov, W.W. Heidbrink, and M.A. Van Zeeland
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

Fields and forces for rectangular beams in an AGS

Description: The direct space-charge fields and forces that are present in a proton beam which has a rectangular cross section and a uniform charge density are considered. The horizontal and vertical betatron tune shifts, corresponding to these forces, which occur within such a beam are calculated. In addition, a direct extension of this rectangular model produces analytical expressions for the tune changes characteristic of a beam profile which has symmetrical or unsymmetrical linear variations of charge density at the horizontal edges of the beam. (auth)
Date: June 26, 1975
Creator: Herrera, J.C.
Partner: UNT Libraries Government Documents Department

Target design optimization for an electron accelerator driven subcritical facility with circular and square beam profiles.

Description: A subcritical facility driven by an electron accelerator is planned at the Kharkov Institute of Physics and Technology (KIPT) in Ukraine for medical isotope production, materials research, training, and education. The conceptual design of the facility is being pursued through collaborations between ANL and KIPT. As part of the design effort, the high-fidelity analyses of various target options are performed with formulations to reflect the realistic configuration and the three dimensional geometry of each design. This report summarizes the results of target design optimization studies for electron beams with two different beam profiles. The target design optimization is performed via the sequential neutronic, thermal-hydraulic, and structural analyses for a comprehensive assessment of each configuration. First, a target CAD model is developed with proper emphasis on manufacturability to provide a basis for separate but consistent models for subsequent neutronic, thermal-hydraulic, and structural analyses. The optimizations are pursued for maximizing the neutron yield, streamlining the flow field to avoid hotspots, and minimizing the thermal stresses to increase the durability. In addition to general geometric modifications, the inlet/outlet channel configurations, target plate partitioning schemes, flow manipulations and rates, electron beam diameter/width options, and cladding material choices are included in the design optimizations. The electron beam interactions with the target assembly and the neutronic response of the subcritical facility are evaluated using the MCNPX code. the results for the electron beam energy deposition, neutron generation, and utilization in the subcritical pile are then used to characterize the axisymmetric heat generation profiles in the target assembly with explicit simulations of the beam tube, the coolant, the clad, and the target materials. Both tungsten and uranium are considered as target materials. Neutron spectra from tungsten and uranium are very similar allowing the use of either material in the subcritical assembly without changing its characteristics. However, the ...
Date: October 30, 2008
Creator: Gohar, M. Y. A; Sofu, T.; Zhong, Z.; Belch, H.; Naberezhnev, D. & Division, Nuclear Engineering
Partner: UNT Libraries Government Documents Department

Notes on Beam Profile Monitor

Description: No abstract prepared.
Date: August 7, 1981
Creator: Joutras, D. & Reinhardt, M.
Partner: UNT Libraries Government Documents Department

Expected Performance of the LHC Synchrotron-Light Telescope (BSRT) and Abort-Gap Monitor (BSRA)

Description: This Report presents calculations of the synchrotron light from proton and lead-ion beams in the LHC at all energies from 0.45 to 7 TeV. It computes the emission from three sources: the uniform-field region of the D3 dipole, the dipole's edge field, and the short undulator just upstream. Light emitted at or near visible wavelengths is assessed for making optical measurements of transverse beam profiles and for monitoring the emptiness of the abort gap in the fill pattern. There is sufficient light for both applications, although both species pass through energy ranges in the ramp with small photon counts. Effects limiting image resolution are examined, including geometric optics, depth of field, and diffraction. The Report also considers recent suggestions that the undulator, intended to supplement the dipole for low energies, should not be ramped off at high energies and perhaps should not be used at all. We conclude that the undulator is essential at low energy for both species, but that it is possible to leave the undulator on at the cost of some blurring at intermediate energies.
Date: June 7, 2010
Creator: Fisher, Alan; /SLAC & ,
Partner: UNT Libraries Government Documents Department

Phasing of Debuncher Stochastic Cooling Transverse Systems

Description: With the higher frequency of the cooling systems in the Debuncher, a modified method of making transfer functions has been developed for transverse systems. (Measuring of the momentum systems is unchanged.) Speed in making the measurements is critical, as the beam tends to decelerate due to vacuum lifetime. In the 4-8 GHz band, the harmonics in the Debuncher are 6,700 to 13,400 times the revolution frequency. Every Hertz change in revolution frequency is multiplied by this harmonic number and becomes a frequency measurement error, which is an appreciable percent of the momentum width of the beam. It was originally thought that a momentum cooling system would be phased first so that the beam could be kept from drifting in revolution frequency. As it turned out, the momentum cooling was so effective (even with the gain turned down) that the momentum width normalized to fo became less than one Hertz on the Schottky pickup. A beam this narrow requires very precise measurement of tune and revolution frequency. It was difficult to get repeatable results. For initial measuring of the transverse arrays, relative phase and delay is all that is required, so the measurement settings outlined below will suffice. Once all input and output arrays are phased, a more precise measurement of all pickups to all kickers can be done with more points and both upper and lower side bands, as in figure 1. Settings on the network analyzer were adjusted for maximum measurement speed. Data is not analyzed until a complete set of measurements is taken. Start and stop frequencies should be chosen to be just slightly wider than the band being measured. For transverse systems, select betatron USB for the measurement type. This will make the measurement two times faster. Select 101 for the number of points, sweep time of ...
Date: March 9, 2000
Creator: Pasquinelli, Ralph
Partner: UNT Libraries Government Documents Department

Transverse Beam Profile Measurement Using Scrape Scans

Description: A scraper scan - sending a scraper through a particle beam while measuring the intensity as a function of scraper position - is a common method of determining the profile of the beam. At first glance, this seems to be a rather simple procedure. Nevertheless, some care is required in the acquisition of the data and in the analysis if one is going to achieve an accurate result.
Date: September 13, 2001
Creator: Werkema, Steven J.
Partner: UNT Libraries Government Documents Department

Quasi-3D space charge simulation

Description: The longitudinal space charge effect is simulated by binning the longitudinal beam profile in order to calculate the force on the bins using the binned particle distribution via FFT, and applying momentum kick based upon this space charge force to macro-particles. Usually, the longitudinal space charge kick is calculated once per turn since the longitudinal profile doesn't change much in a single turn. Besides, the longitudinal profile is used as a weighting factor for the transverse space charge force. The transverse space charge effect is simulated by projecting the 3-D beam to a 2-D Gaussian distribution in order to use the complex error function to compute the transverse space charge force, and applying this space charge force to macro-particles. One transverse space charge calculation per scale length of the beam shape variation requires at least ten transverse space charge force calculations per betatron oscillation.
Date: April 1, 2007
Creator: Yang, Xi
Partner: UNT Libraries Government Documents Department