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316,577 Matching Results

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(open access)

Experimental study of crossing angle collision

The non-linear coupling due to the beam-beam interaction with crossing angle has been studied. The major effect of a small ({approximately}12mrad) crossing angle is to excite 5Q{sub x}{plus_minus}Q{sub s}=integer coupling resonance family on large amplitude particles, which results in bad lifetime. On the CESR, a small crossing angle ({approximately}2.4mr) was created at the IP and a reasonable beam-beam tune-shift was achieved. The decay rate of the beam is measured as a function of horizontal tune with and without crossing angle. The theoretical analysis, simulation and experimental measurements have a good agreement. The resonance strength as a function of crossing angle is also measured.

Date: May 1, 1993

Creator: Chen, T.; Rice, D.; Rubin, D.; Sagan, D. & Tigner, M.

Object Type: Article

System: The UNT Digital Library

(open access)

Resonance crossing in a proton synchrotron application to ISABELLE

None

Date: October 31, 1974

Creator: Chasman, R.; Garren, A.; Gluckstern, R. L. & Mills, F. E.

Object Type: Article

System: The UNT Digital Library

(open access)

Comparing Near-Death Experiences and Shared Death Experiences: An Illuminating Contrast

Article comparing records of persons who reported near-death experiences (i.e., experienced by a person close to death) with shared death experiences (i.e., experienced by someone other than the person close to death). It discusses similarities and differences in features and aftereffects based on these reports.

Date: Summer 2022

Creator: Shared Crossing Research Initiative

Object Type: Article

System: The UNT Digital Library

(open access)

Caution -- Beam Crossing Ahead

There are times when a laser beam needs to cross between tables or even go from one room to another. This presents an interesting traffic-flow and safety challenge to both the laser safety officer and laser user. Fortunately it is a challenge that has several solutions But the simplest solution may not be the best one. For example, the simplest way to get a beam from one optical table to another is just to put a sturdy tube around it. That's a permanent solution, and it completely contains the laser beam. While this is laser safe, there can be egress issues if it blocks a walkway. One comment this author often hears is, 'We can just duck under the tube.' The fire marshal, as well as the laser safety officer, might have issues with this. Especially in the case of a darkened lab, a blocked walkway can present a hazard of its own. One good solution is to transport the beam from Point A to Point B through a fiberoptic cable, when that is possible. One should easily be able to run the fiber up and over any walkway or down through a conduit on the floor. An important concern …

Date: April 2, 2008

Creator: Barat, Kenneth L.

Object Type: Article

System: The UNT Digital Library

(open access)

Energy scaling, crab crossing and the pair problem

Making reasonable assumptions, the luminosities of linear colliders are calculated for center-of-mass energies of 10 GeV, 100 GeV and 1 TeV. A calculation is also mode for a 1/2 TeV collider that could be upgraded to 1 TeV later. The improvements possible using ''crab-like'' crossing are also given. 4 refs., 4 figs., 3 tabs.

Date: December 1, 1988

Creator: Palmer, Robert B.

Object Type: Article

System: The UNT Digital Library

(open access)

Luminosity Optimization With Offset, Crossing Angle, and Distortion

In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In this paper, we study the luminosity loss and then the optimization required to partially cancel the luminosity loss both analytically and with direct simulation.

Date: June 15, 2005

Creator: Wu, Juhao & Raubenheimer, T. O.

Object Type: Article

System: The UNT Digital Library

(open access)

Parasitic crossing at an asymmetric B factory, APIARY

Effects of parasitic crossings ( near miss'' collisions of two counter-rotating beams at unwanted positions near the IP) are studied in terms of computer simulations for an asymmetric B Factory, APIARY- 6.3d. Beams are separated horizontally at the first parasitic crossing points by about 7.6 times the horizontal rms size of the low energy beam (the larger in size of the two beams), {sigma}{sub 0x,+}. Simulations, including both the beam collision at the IP and parasitic crossings, have been performed for different separation distances, d. It is found that the ratio d/{sigma}{sub 0x,+} is a good scaling parameter of beam blowup behavior. The results show that beam blowup due to the parasitic crossings is diminished for d {ge} 7{sigma}{sub 0x,+}, in agreement with the bunch separation experiment at CESR. Thus, the nominal separation 7.6 {sigma}{sub 0x,+} turns out to be acceptable, but with only a small margin. Some methods to mitigate the effects of the parasitic crossings are discussed. 3 refs. , 5 figs., 2 tabs.

Date: May 1, 1991

Creator: Chin, Y. H.

Object Type: Article

System: The UNT Digital Library

(open access)

Bill Viola: "The Crossing"

Catalog for the exhibition, "Bill Viola: 'The Crossing,'" November 12, 1998–February 1, 1999,held at the Dallas Museum of Art. Includes: essay and image.

Date: 1998

Creator: Dallas Museum of Art

Object Type: Pamphlet

System: The Portal to Texas History

(open access)

Detection of illegal border crossing, a pattern recognition approach

This report describes a new algorithm developed for the Immigration and Naturalization Service (INS) in support of the INSENS project for classifying vehicles and pedestrians using seismic data. This algorithm is less sensitive to nuisance alarms due to environmental events than the previous algorithm. Furthermore, the algorithm is simple enough that it scan be; implemented in the 8-bit microprocessor used in the INSENS system.

Date: September 29, 1993

Creator: Hernandez, J. E.; Frerking, C. J. & Myers, D. W.

Object Type: Article

System: The UNT Digital Library

(open access)

CROSSING OF AN INCOHERENT INTEGRAL RESONANCE IN THE ELECTRON RING ACCELERATOR

In one mode of operation of an electron ring accelerator (ERA), at the end of compression rings are slowly moved through the radial integral betatron resonance Q{sub r} = 1. Although the coherent radial oscillation frequency of the ring as a whole remains below unit, the oscillation frequencies of individual electron are (incoherently) caused to pass through the resonance because of the additional focusing from ions trapped in the ring. In this paper the effect of field errors on ring major and minor radii is evaluated--theoretically--for the cases in which the spread in the square of the electron oscillation frequency ({Delta}{sup 2}) is (a) much larger and (b) much smaller than the contribution to the square of the oscillation frequency from the ions ({Lambda}{sup 2}). It is shown that for the ERA, where case (b) applies, the increase in ring minor dimensions, for given field errors and rate of resonance crossing, is less than in case (a) by a factor of ({Delta}/{Lambda}){sup 2}. Numerical examples show that the degradation of ring quality in case (b) should, with suitable attention to the design and construction of the ERA apparatus, be acceptably small.

Date: January 26, 1970

Creator: Pellegrini, Claudio & Sessler, Andrew M.

Object Type: Report

System: The UNT Digital Library

(open access)

ILC Extraction Line for 14 mrad Crossing Angle

The earlier studies of the ILC extraction line for 20 mrad and 2 mrad crossing angle options [1]-[5] showed that the 20 mrad design has an advantage of a simpler beamline and lower extraction beam loss because of the independent incoming and extraction optics. However, the large 20 mrad crossing angle requires the use of a crab cavity correction, increases synchrotron radiation emittance growth in the solenoid, and increases photon backscattering from the forward calorimeter of the detector. To reduce these effects, an attempt has been made to minimize the crossing angle while keeping the extraction and incoming lines separate. A new quadrupole scheme near the interaction point has been proposed which allows a reduction of the crossing angle to 14 mrad [6]. The optics design and results of tracking and background simulations for the 14 mrad extraction line are presented.

Date: December 8, 2005

Creator: Nosochkov, Y.; Markiewicz, T.; Maruyama, T.; Seryi, A. & Parker, B.

Object Type: Article

System: The UNT Digital Library

(open access)

The 2mrad horizontal crossing angle IR layout for a TeV ILC

The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.

Date: July 27, 2005

Creator: Appleby, R.; Angal-Kalinin, D.; /Daresbury; Bambade, P.; Mouton, B.; /Orsay, LAL et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Unified Model of Dynamic Forced Barrier Crossing in Single Molecules

Thermally activated barrier crossing in the presence of an increasing load can reveal kinetic rate constants and energy barrier parameters when repeated over a range of loading rates. Here we derive a model of the mean escape force for all relevant loading rates--the complete force spectrum. Two well-known approximations emerge as limiting cases; one of which confirms predictions that single-barrier spectra should converge to a phenomenological description in the slow loading limit.

Date: June 21, 2007

Creator: Friddle, R W

Object Type: Article

System: The UNT Digital Library

(open access)

Design of Ilc Extraction Line for 20 Mrad Crossing Angle

One of the two ILC Interaction Regions will have a large horizontal crossing angle which would allow to extract the spent beams in a separate beam line. In this paper, the extraction line design for 20 mrad crossing angle is presented. This beam line transports the primary e{sup +}/e{sup -} and beamstrahlung photon beams from the IP to a common dump, and includes diagnostic section for energy and polarization measurements. The optics is designed for a large energy acceptance to minimize losses in the low energy tail of the disrupted beam. The extraction optics, diagnostic instrumentation and particle tracking simulations are described.

Date: May 16, 2005

Creator: Nosochkov, Y.; Moffeit, K.; Seryi, A.; Woods, M.; Arnold, R.; Oliver, W. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

The 2mrad Crossing Angle Interaction Region and Extraction Line

A complete optics design for the 2mrad crossing angle interaction region and extraction line was presented at Snowmass 2005. Since this time, the design task force has been working on developing and improving the performance of the extraction line. The work has focused on optimizing the final doublet parameters and on reducing the power losses resulting from the disrupted beam transport. In this paper, the most recent status of the 2mrad layout and the corresponding performance are presented.

Date: July 12, 2006

Creator: Appleby, R.; U., Manchester; Angal-Kalinin, D.; Tech, /Cockcroft Inst. Accel. Sci.; Dadoun, O.; Bambade, P. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Optics of the ILC Extraction Line for 2mrad Crossing Angle

The ILC extraction line for 2 mrad crossing angle is under development by the SLAC-BNL-UK-France task force collaboration. This report describes the progress in the 2 mrad optics design which includes the changes to the final focus doublet, the complete optics for the extraction diagnostics, and the changes to the sextupole and collimation systems. The results of disrupted beam tracking simulations are presented.

Date: January 5, 2006

Creator: Nosochkov, Y.; Moffeit, K.; Seryi, A.; Spencer, C.; Woods, M.; Angal-Kalinin, D. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Presidential Permits for Border Crossing Energy Facilities

This report discusses the executive orders regarding the construction, operation, and maintenance of facilities that cross the U.S.-Mexico or U.S.- Canada border, including the source of the executive branch authority to issue the orders, the standards set forth in the orders, and the projects approved pursuant to the orders.

Date: October 29, 2013

Creator: Vann, Adam & Parfomak, Paul W.

Object Type: Report

System: The UNT Digital Library

(open access)

Keck Observations of the 2002-2003 Jovian Ring Plane Crossing

We present new observations of Jupiter's ring system at a wavelength of 2.2 {micro}m obtained with the 10-m W. M. Keck telescopes on three nights during a ring plane crossing: UT 19 December 2002, and 22 and 26 January 2003. We used conventional imaging, plus adaptive optics on the last night. Here we present detailed radial profiles of the main ring, halo and gossamer rings, and interpret the data together with information extracted from radio observations of Jupiter's synchrotron radiation. The main ring is confined to a 800-km-wide annulus between 128,200 and 129,000 km, with a {approx} 5000 km extension on the inside. The normal optical depth is 8 x 10{sup -6}, 15% of which is provided by bodies with radii a {approx}> 5 cm. These bodies are as red as Metis. Half the optical depth, {tau} {approx} 4 x 10{sup -6}, is attributed to micron-sized dust, and the remaining {tau} {approx} 3 x 10{sup -6} to grains tens to hundreds of {micro}m in size. The inward extension consists of micron-sized (a {approx}< 10 {micro}m) dust, which probably migrates inward under Poynting-Robertson drag. The inner limit of this extension falls near the 3:2 Lorentz resonance (at orbital radius r = …

Date: November 29, 2007

Creator: de Pater, I.; Showalter, M. R. & Macintosh, B. A.

Object Type: Article

System: The UNT Digital Library

(open access)

Beam-Beam Scans Within a Linear Collider Bunch-Train Crossing

Beam-beam deflection scans provide important beam diagnostics at the interaction point of a linear collider. Beam properties such as spot sizes, alignment, and waists are measured by sweeping one beam across the other. Proposed linear colliders use trains of bunches; if beam-beam scans can be done within the time of a bunch-train crossing rather than integrating over the bunch train, the acquisition rate of diagnostic information can be increased and the sensitivity of the scan to pulse-to-pulse jitter and slow drifts reduced. The existence of intra-train deflection feedback provides most of the hardware needed to implement intra-train beam-beam scans for diagnostic purposes. A conceptual design is presented for such beam-beam scans at the Next Linear Collider (NLC).

Date: February 22, 2006

Creator: Smith, S. R.

Object Type: Article

System: The UNT Digital Library

(open access)

Crossing angle collision and lifetime: Simulations, analysis, measurements and more simulations

To achieve the high luminosity required by heavy quark factories, multibunch operation is almost the only choice. The key to gain luminosity in multibunch operation is to reduce the bunch spacing. Therefore, colliding beams with a crossing angle becomes the favorite interaction region scheme. The introduction of a crossing angle in e{sup +}e{sup {minus}} colliders causes non-linear coupling between horizontal motion and longitudinal motion. This is illustrated in Figure 1. The beam-beam kick occurs when the particle passes the center of the opposing bunch. The strength of the kick, {Delta}r{prime} = F(r), is a nonlinear function of the distance, r, between the particle and the center of the opposite bunch. In head-on collisions, r is the transverse displacement, and the kick is in the transverse plane, so that the process is nonlinear but not influenced by the longitudinal motion. In collisions with a crossing angle, however, r is a function of longitudinal displacement, s, and the crossing angle, F, as well as transverse displacement. The distance r between the test particle and the bunch center can be written.

Date: July 1, 1995

Creator: Chen, T.

Object Type: Article

System: The UNT Digital Library

(open access)

Comparison of 2 mrad and 14/20 mrad Crossing Angle Extraction Lines

A study of the beam distributions in the 2 mrad and 14/20 mrad extraction lines are presented. Beam losses, energy losses due to synchrotron radiation and spin diffusion are shown. Synchrotron radiation distributions generated by the beam as it traverses the extraction lines are studied.

Date: July 17, 2006

Creator: Moffeit, Ken; Maruyama, Takashi; Nosochkov, Yuri; Seryi, Andrei; Wood, Mike & /SLAC

Object Type: Report

System: The UNT Digital Library

(open access)

Introduction to the Workshop, and a Brief Review of the Early Experiments on Multiple Crossing Laser Beams

The purpose of the workshop is to review recent experiments on the laser plasma interactions of multiple laser beams, and encourage interaction and collaboration on future experiments in this exciting emerging area. The format is a series of nine, 10 minute talks followed by a 5 minute question period covering the major topics of (1) scattering and transfer of power by multiple beams in ICF experiments; (2) basic studies of KEEN wave physics especially as facilitated by multi-beam interaction; and (3) compression of laser pulses by multi-beam interactions.

Date: June 12, 2005

Creator: Kirkwood, R K

Object Type: Article

System: The UNT Digital Library

(open access)

Long-Range Beam--Beam Interaction of Crossing Beams

None

Date: January 1, 1972

Creator: Keil, E.; Pellegrini, C. & Sessler, A. M.

Object Type: Report

System: The UNT Digital Library

(open access)

Summary of Working Group I - beam-beam instability with crossing angle

This report is a summary report from a panel addressing the problem of beam-beam instability in colliding beams at finite crossing angles. This problem arises in the process of increasing luminosity in large circular particle factories. The primary means of increasing luminosity comes down to increasing the number of bunches in each beam, while decreasing the spacing between bunches. This situation favors finite crossing angle collision schemes. However such schemes allow synchro-betatron coupling, as transverse and longitudinal energies are mixed. The authors summarize their discussions on this problem, and the present state of experience with such schemes.

Date: June 1, 1995

Creator: Chen, T.

Object Type: Article

System: The UNT Digital Library

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