Beam-based alignment in RHIC

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Investigation of the radiation background in the interaction region of the medium-energy electron relativisitic heavy ion collider (MeRHIC)

There are three main sources of the radiation background in MeRHIC: forward synchrotron radiation generated upstream of the detector, the direct backward radiation caused by the photons hitting beampipe downstream of the detector, and the indirect secondary radiation caused by hard photons hitting vacuum systems, masks, collimators, absorbers or any other elements in the interaction region. In this paper, we first calculate the primary radiation distribution by employing electromagnetic theory. Then we obtain the direct backward scattering rate by applying the kinematic Born approximation deduced from scattering dynamics. The diffuse scattering cross section is calculated as a function of the surface properties of the MeRHIC vacuum system. Finally, the dominating physical processes and minimization of indirect secondary radiation is presented and discussed

EMITTANCE GROWTH DUE TO BEAM-BEAM EFFECT IN RHIC.

The beam-beam interaction has a significant impact on the beam emittance growth and the luminosity lifetime in RHIC. A simulation study of the emittance growth was performed using the LIFETRAC code. The operational conditions of RHIC 2006 100GeV polarized proton run were used in the study. In this paper, the result of this study is presented and compared to the experimental measurements

Realistic Non-Linear Model and Field Quality Analysis in Rhic Interaction Regions.

The existence of multipole components in the dipole and quadrupole magnets is one of the factors limiting the beam stability in the RHIC operations. So, a realistic non-linear model is crucial for understanding the beam behavior and to achieve the ultimate performance in RHIC. A procedure is developed to build a non-linear model using the available multipole component data obtained from measurements of RHIC magnets. We first discuss the measurements performed at different stages of manufacturing of the magnets in relation to their current state in RHIC. We then describe the procedure to implement these measurement data into tracking models, including the implementation of the multipole feed down effect due to the beam orbit offset from the magnet center. Finally, the field quality analysis in the RHIC interaction regions (IR) is presented

Interaction region design for a RHIC-based medium-energy electron-ion collider

As a first step in a staged approach towards a RHIC-based electron-ion collider, installation of a 4 GeV energy-recovery linac (ERL) in one of the RHIC interaction regions is currently under investigation. To minimize costs, the interaction region of this collider has to use the present RHIC magnets for focusing of the high-energy ion beam. Meanwhile, electron low-beta focusing needs to be added in the limited space available between the existing separator dipoles. We discuss the challenges and present the current design status of this e-A interaction region

Beam-beam simulation code BBSIM for particle accelerators

A highly efficient, fully parallelized, six-dimensional tracking model for simulating interactions of colliding hadron beams in high energy ring colliders and simulating schemes for mitigating their effects is described. The model uses the weak-strong approximation for calculating the head-on interactions when the test beam has lower intensity than the other beam, a look-up table for the efficient calculation of long-range beam-beam forces, and a self-consistent Poisson solver when both beams have comparable intensities. A performance test of the model in a parallel environment is presented. The code is used to calculate beam emittance and beam loss in the Tevatron at Fermilab and compared with measurements. We also present results from the studies of two schemes proposed to compensate the beam-beam interactions: a) the compensation of long-range interactions in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven and the Large Hadron Collider (LHC) at CERN with a current-carrying wire, b) the use of a low energy electron beam to compensate the head-on interactions in RHIC

Synergistic Effects of Nanosecond Pulsed Electric Fields Combined with Low Concentration of Gemcitabine on Human Oral Squamous Cell Carcinoma In Vitro

Treatment of cancer often involves uses of multiple therapeutic strategies with different mechanisms of action. In this study we investigated combinations of nanosecond pulsed electric fields (nsPEF) with low concentrations of gemcitabine on human oral cancer cells. Cells (Cal-27) were treated with pulse parameters (20 pulses, 100 ns in duration, intensities of 10, 30 and 60 kV/cm) and then cultured in medium with 0.01 mu g/ml gemcitabine. Proliferation, apoptosis/necrosis, invasion and morphology of those cells were examined using MTT, flow cytometry, clonogenics, transwell migration and TEM assay. Results show that combination treatments of gemcitabine and nsPEFs exhibited significant synergistic activities versus individual treatments for inhibiting oral cancer cell proliferation and inducing apoptosis and necrosis. However, there was no apparent synergism for cell invasion. By this we demonstrated synergistic inhibition of Cal-27 cells in vitro by nsPEFs and gemcitabine. Synergistic behavior indicates that these two treatments have different sites of action and combination treatment allows reduced doses of gemcitabine and lower nsPEF conditions, which may provide better treatment for patients than either treatment alone while reducing systemic toxicities

Accumulator ring design for the NSNS project

The goal of the proposed National Spallation Neutron Source (NSNS) is to provide a short pulse proton beam of about 0.5 {mu}s with average beam power of 1 MW. To achieve such purpose, a proton storage ring operated at 60 Hz with 1 x 10{sup 14} protons per pulse at 1 GeV is required. The Accumulator Ring (AR) receives 1 msec long H{sup {minus}} beam bunches of 28 mA from a 1 GeV linac. Scope and design performance goals of the AR are presented, other possible technological choices and design options considered, but not adopted, are also briefly reviewed

Large array of sub-10 nm single-grain Au nanodots for use in nanotechnology

A uniform array of single-grain Au nanodots, as small as 5-8 nm, can be formed on silicon using e-beam lithography. The as-fabricated nanodots are amorphous, and thermal annealing converts them to pure Au single crystals covered with a thin SiO2 layer. These findings are based on physical measurements, such as atomic force microscopy (AFM), atomic resolution scanning transmission electron microscopy, and chemical techniques using energy dispersive x-ray spectroscopy. A self-assembled organic monolayer is grafted on the nanodots and characterized chemically with nanometric lateral resolution. We use the extended uniform array of nanodots as a new test-bed for molecular electronics devices.Comment: In press. One file, including the manuscript and supplementary informatio