Previous analyses have assumed that wedge absorbers are triangularly shaped with equal angles for the two faces. In this case, to linear order, the energy loss depends only on the position in the direction of the face tilt, and is independent of the incoming angle. One can instead construct an absorber with entrance and exit faces facing rather general directions. In this case, the energy loss can depend on both the position and the angle of the particle in question. This paper demonstrates that and computes the effect to linear order.

Success in the application of the action and phase analysis to find linear errors at RHIC Interaction Regions [1] has encouraged the creation of a technique based on the action and phase analysis to find non linear errors. In this paper we show the first attempt to measure the sextupole components at RHIC interaction regions using the action and phase method. Experiments done by intentionally activating sextupoles in RHIC and in SPS [2] will also be analyzed with this method. First results have given values for the sextupole errors that at least have the same order of magnitude as the values found by an alternate technique during the RHIC 2001 run [3].

Beam induced electron multipacting may be among the main reasons for the vacuum pressure rise when circulating high intensity ion and proton beams in RHIC. Latest simulation results are benchmarked with recent experimental observations for RHIC, and compared to other general computer codes. The influence of the electron multipacting to the vacuum properties is also discussed.

As one of the most critical system for RHIC operation, the beam abort kicker system has to be highly available, reliable, and stable for the entire operating range. Along with the RHIC commission and operation, consistent efforts have been spend to cope with immediate issues as well as inherited design issues. Major design changes have been implemented to achieve the higher operating voltage, longer high voltage hold-off time, fast retriggering and redundant triggering, and improved system protection, etc. Recent system test has demonstrated for the first time that both blue ring and yellow ring beam abort systems have achieved more than 24 hours hold off time at desired operating voltage. In this paper, we report break down, thyratron reverse arcing, and to build a fast re-trigger system to reduce beam spreading in event of premature discharge.

A future muon collider or neutrino factory requires fast acceleration to minimize muon decay. We have previously described an FFAG ring that accelerated muons from 10 to 20 GeV in energy. The ring achieved its large momentum acceptance using a low-emittance lattice with a small dispersion. In this paper, we present an update on that ring. We have used design tools that more accurately represent the ring's behavior at large momentum offsets. We have also improved the dynamic aperture from the earlier design.

During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX.

Deuteron and gold beams have been accelerated to a collision energy of {radical}s = 200 GeV/u in the Relativistic Heavy Ion Collider (RHIC), providing the first asymmetric-species collisions of this complex. Necessary changes for this mode of operation include new ramping software and asymmetric crossing angle geometries. This paper reviews machine performance, problem encountered and their solutions, and accomplishments during the 16 weeks of ramp-up and operations.

Fixed target studies of small branching ratio decay processes require intense beams and smooth spills. Longitudinal structure arises through collective effects, well below the coasting beam stability threshold. These structures have been observed at the Brookhaven AGS and dependence on intensity and momentum spread measured. Measurements and amelioration techniques have been developed and will be described.

As part of a future upgrade to the Relativistic Heavy Ion Collider (RHIC), electron cooling is foreseen to decrease ion beam emittances. Within the electron cooling section, the ''hot'' ion beam is immersed in a ''cold'' electron beam. The cooling effect is further enhanced by a solenoid field in the cooling section, which forces the electrons to spiral around the field lines with a (Larmor) radius of 10 micrometers, reducing the effective transverse temperature by orders of magnitude. Studies of the effect of solenoid field errors on electron beam temperatures are reported.

Polarized proton beam has been accelerated and stored at 100 GeV in Relativistic Heavy Ion Collider (RHIC) to study spin effects in the hadronic reactions. The essential equipment includes four Siberian snakes and eight spin rotators in two RHIC rings, a partial snake in the AGS, fast relative polarimeters, and ac dipoles in the AGS and RHIC. This paper summarizes the performance of RHIC as a polarized proton collider and of AGS as the injector to RHIC.

The luminosity performance of a future linear collider (LC) will depend critically on the performance of the damping rings. The design luminosities of the current LC proposals require rings with very short damping times, large acceptance, low equilibrium emittance and high beam intensity. We discuss the design strategies for lattices achieving the goals of dynamical stability, examine the challenges for alignment and coupling correction, and consider a variety of collective effects that threaten to limit beam quality. We put the design goals in context by referring to the experience of operating facilities, and outline the further research and development that is needed.

To address regulatory issues regarding worker safety, radon gas concentrations have been monitored as part of the operation of a deep tunnel excavated from a highly fractured tuff formation. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured rock. An iTOUGH2 model was developed to predict radon concentrations for prescribed ventilation rates. The numerical model was used (1) to estimate the permeability and porosity of the fractured formation at the length scale of the tunnel and extending tens of meters into the surrounding rock, and (2) to understand the mechanism leading to radon concentrations that potentially exceed the regulatory limit. The mechanism controlling radon concentrations in the tunnel is a function of atmospheric barometric fluctuations propagated down the tunnel. In addition, a slight suction is induced by the ventilation system. The pressure fluctuations are dampened in the fractured formation according to its permeability and porosity. Consequently, as the barometric pressure in the tunnel drops, formation gases from the rock are pulled into the opening, resulting in high radon concentrations. Model calibration to both radon concentration data measured in the tunnel and gas phase pressure fluctuations observed in …

Automatic differentiation (AD) is a way to accurately and efficiently compute derivatives of a function written in computer codes. We describe the procedures necessary to apply the AD method to the multiphase, multicomponent, nonisothermal flow simulator TOUGH2. In particular, we apply the AD method to the ECO2 module of the TOUGH2 code to explore a scheme for efficiently calculating the Jacobian matrix, which is required by the Newton-Raphson method for handling the nonlinearities arising at each iteration. The ECO2 module allows TOUGH2 to accurately simulate CO2 sequestration in aquifers. The robustness and efficiency of the AD-generated derivative codes are compared to the conventional derivative computation approach based on first-order finite differences (FD). Our result with the test problem set indicates that the AD-generated derivative code could improve the convergence behavior in the linear solution step, taking less computational time to compute one linear matrix system.

One of the critical issues for the development of Laser Wake Field Acceleration (LWFA), which has the promise of creating table-top, GeV accelerators, is the loading of beamlets into the accelerating buckets. All optical injection schemes, which include LILAC, beat-wave colliding pulse injection, wave breaking injection, and phase-kick injection, provide a technique for doing so. Although a single bunch can have desirable properties such as energy spread of the order of a few percent, femtosecond duration k and low emittance (<1 mm-mrad), recent simulations show that such methods lead to efficiencies of transfer of plasma wave energy to beam energy that are low compared with conventional RF accelerators when only a single pulse is generated. Our latest simulations show that one can improve on this situation through the generation of a beamlet train. This can occur naturally through phase-kick injection at the front of the train and transverse wave breaking for the trailing pulses. The result is an efficiency improvement of the order of the number of beamlets in the train.

Gesellschaft fur Schwerionenforschung (GSI) has proposed a large expansion of the existing facility in Darmstadt, Germany. The proposal includes an accelerator, SIS200, with rigidity of 200 Tam that utilizes 4 T superconducting dipoles ramped at 1 T/s. An R&D program including both the superconductor and the magnet is directed at achieving the desired ramp rate with minimal energy loss. The RHIC arc dipoles, with 8 cm aperture, possess adequate aperture and field strength but are ramped at only 1/20 of the desired rate. However, for reasons of speed and economy, the RHIC dipole is being used as the basis for this work. The superconductor R&D has progressed far enough to permit the manufacture of an initial cable with satisfactory properties. This cable has been used in the construction of a I m model magnet, appropriately modified from the RHIC design. The magnet has been tested successfully at 2 T/s to 4.38 T.

Brookhaven National Laboratory plans to build a partial helical snake for polarized proton acceleration in the AGS. It will be a 3 Tesla superconducting magnet having a magnetic length of 1.9 meter. AGS needs only one magnet and currently there is no plan to build a prototype. Therefore, the first magnet itself must function at the design operating field and provide the required field quality, spin rotation and deflections on the particle beam. New software have been developed that exchanges input/output between the OPERA3d field design program, the Pro-Engineering CAD model and the software that drives the machine to make slots in aluminum cylinders where blocks of 6-around-I NbTi wires are placed. This new software have been used to carry out a number of iterations to satisfy various design requirements and to assure that the profile that is used in making field computations is the same that is used in cutting metal. The optimized coil cross-section is based on a two layer design with both inner and outer layers having five current blocks per quadrant. The ends are based on a design concept that will be used for the first time in accelerator magnets.

The INTRODUCTION to this paper summarizes the history of the Global Accelerator Network (GAN) concept and the recent workshops that discussed the relationship between GAN and Remote Operations. The REMOTE OPERATIONS SCENARIOS section brings out the organizational philosophy embodied in GAN-like and to non-GAN-like scenarios. The set of major TOPICS RAISED AT THE WORKSHOPS are only partially resolved. COLLABORATION TOOLS are described and discussed, followed by examples of REMOTE ACCELERATOR CONTROL PROJECTS around the world.

Methods for determining the parameters necessary for modeling fluid flow and contaminant transport in the shallow subsurface are in great demand. Soil properties such as permeability, porosity, and water retention are typically estimated through the inversion of hydrological data (e.g., measurements of capillary pressure and water saturation). However, ill-posedness and non-uniqueness commonly arise in such inverse problems making their solutions elusive. Incorporating additional types of data, such as from geophysical methods, may greatly improve the success of inverse modeling. In particular, ground-penetrating radar (GPR) has proven sensitive to subsurface fluid flow processes. In the present work, an inverse technique is presented in which permeability distributions are generated conditional to time-lapsed GPR measurements and hydrological data collected during a transient flow experiment. Specifically, a modified pilot point framework has been implemented in iTOUGH2 allowing for the generation of permeability distributions that preserve point measurements and spatial correlation patterns while reproducing geophysical and hydrological measurements. Through a numerical example, we examine the performance of this method and the benefit of including synthetic GPR data while inverting for fluid flow parameters in the vadose zone. Our hypothesis is that within the inversion framework that we describe, our ability to predict flow across control …

Full waveform inversion of seismic data is a challenging subject partly because of the lack of precise knowledge of the source. Since currently available approaches involve some form of approximations to the source, inversion results are subject to the quality and the choice of the source information used. A new full waveform inversion scheme has been introduced (Lee and Kim, 2003) using normalized wavefield for simple two-dimensional (2-D) scalar problems. The method does not require source information, so potential inversion errors due to source estimation may be eliminated. A gather of seismic traces is first Fourier-transformed into the frequency domain and a normalized wavefield is obtained for each trace in the frequency domain. Normalization is done with respect to the frequency response of a reference trace selected from the gather, so the complex-valued normalized wavefield is source-independent and dimensionless. The inversion algorithm minimizes misfits between measured normalized wavefield and numerically computed normalized wavefield. In this paper the full waveform inversion is extended to three-dimensional (3-D) problems.

Low emittance electron storage rings, such as those used in third generation light sources or linear collider damping rings, rely for their performance on highly stable alignment of the lattice components. Even if all vibration and environmental noise sources could be suppressed, diffusive ground motion will lead to orbit drift and emittance growth. Understanding such motion is important for predicting the performance of a planned accelerator and designing a correction system. A description (known as the ATL model) of ground motion over relatively long time scales has been developed and has become the standard for studies of the long straight beamlines in linear colliders. Here, we show how the model may be developed to include beamlines of any geometry. We apply the model to the NLC and TESLA damping rings, to compare their relative stability under different conditions.

Silicone rubber received attention as an alternative to polyvinyltoluene in applications in which the scintillator is exposed to high doses because of the increased resistance of the rubber to the formation of blue-absorbing color centers. Work by Bowen, et al., and Harmon, et al., demonstrated their properties under gamma/x-ray irradiation, and Bell, et al. have shown their response to thermal neutrons. This last work, however, provided an example of a silicone in which both the boron and the scintillator were contained in the rubber as solutes, a formulation which led to the precipitation of solids and sublimation of the boron component. In the present work we describe a scintillator in which the boron is chemically bonded to the siloxane and so avoids the problem of precipitation and loss of boron to sublimation. Material containing up to 18% boron, by weight, was prepared, mounted on photomultipliers, and exposed to both neutron and gamma fluxes. Pulse height spectra showing the neutron and photon response were obtained, and although the light output was found to be much poorer than from samples in which boron was dissolved, the higher boron concentrations enabled essentially 100% neutron absorption in only a few millimeters' thickness of rubber.

Evaporation from the surface of a porous medium is a complex process, governed by interplay between (1) coupled liquid and vapor flow in the porous medium, and (2) relative humidity, temperature, and aerodynamic conditions in the surrounding air. In order to avoid the computational expense of explicitly simulating liquid, gas, and heat flow in the porous medium (and the possible further expense of simulating the flow of water vapor in the atmosphere), evaporative potentials can be treated in a simplified manner within a model where liquid is the only active phase. In the case of limited air mixing, evaporation can be approximated as a diffusion process with a linear vapor-concentration gradient. We have incorporated a simplified scheme into the EOS9 module of iTOUGH2 to represent evaporation as isothermal Fickian diffusion. This is notable because the EOS9 module solves a single equation describing saturated and unsaturated flow, i.e., phase transitions and vapor flow are not explicitly simulated. The new approach was applied to three simple problems and the results were compared to those obtained with analytical solutions or the EOS4 module, which explicitly considers advective and diffusive vapor flow. Where vapor flow within the porous medium can be neglected, this new …

To meet the performance parameters of the Spallation Neutron Source (SNS) for high beam intensity with low losses, the compact accumulation ring will contain 32 sector dipoles with 1.44 m effective length and a large aperture, 170 mm. The magnets are built from potted coils and machined pieces of solid iron. When first assembled, the dipoles met the requirements for field uniformity but the rms variation of the integral transfer function (ITF) was much larger than design at both fields of interest, 1.11 T{center_dot}m and 1.33 T{center_dot}m, corresponding to proton energies of 1.0 GeV and 1.3 GeV respectively. Based on initial measurements, shims have been added to the return legs or poles, as appropriate, in order to bring the rms variation of the 1.0 GeV ITF to the specification, 0.01%. The value of the ITF rms variation at 1.3 GeV for the shimmed magnets is 0.033%. Sorting the magnets has significantly reduced the load on the correctors due to this ITF variation.

This paper describes measurements of beam spot size and emittance of electron beams from a pulsed power photo-injector operating at 150keV output energy. In these measurements, electron bunches with charge up to 20 pC were created by a 300 fs pulse duration Ti: Sapphire laser system illuminating a polished copper cathode. Images of the electron beam were captured at two locations downstream from a solenoid focusing magnet. The focal spot size was studied as a function of bunch charge and accelerating gradient. Beam waists down to 85 microns were obtained. The focal spot size was found to be dominated by spherical aberration at low beam charges, however the beam trajectory is in good agreement with simulation.