30677291
EXPERIMENTAL PROGRESS: CURRENT FILAMENTATION INSTABILITY STUDY *
Current Filamentation Instability, CFI, is of central importance for the propagation of relativistic electron beams in plasmas. CFI has potential relevance to astrophysics, magnetic field and radiation generation in the afterglow of gamma ray bursts, and inertial confinement fusion, energy transport in the fast-igniter concept. An experimental study of this instability is underway at the Brookhaven National Laboratory - Accelerator Test Facility. We use the particle-in-cell code QuickPIC to study phenomena observed in the experiment. These include merging of filaments and the dependence of the growth rate of the instability on plasma density and beam emittance.
35408696
WITNESS BUNCH ACCELERATION IN A MULTI-BUNCH PWFA ∗
We present initial experimental results showing the excitation of plasma wakefields by a train of two drive bunches. These wakefields are experienced by a trailing witness bunch that gains energy while retaining a finite energy spread. These well controlled plasma wakefield accelerator (PWFA) experiments are important to test the theory of the PWFA and serve as a testbed for techniques that will be used in high energy experiments.
29439632
PROGRESS IN EXPERIMENTAL STUDY OF CURRENT FILAMENTATION INSTABILITY
Current Filamentation Instability, CFI, is of central importance for the propagation of relativistic electron beams in plasmas. CFI could play an important role in the generation of magnetic fields and radiation in the afterglow of gamma ray bursts and also in energy transport for the fast-igniter inertial confinement fusion concept. Simulations were conducted with the particle-in-cell code QuickPIC for e beam and plasma parameters at the Brookhaven National Laboratory – Accelerator Test Facility, BNL-ATF. Results show that for a 2cm plasma the instability reaches near saturation. An experimental program was proposed and accepted at the BNL-ATF and an experiment is currently underway. There are three components to the experimental program: 1) imaging of the filaments, beam density, at the exit from the plasma, 2) measurement and imaging of the transverse plasma density gradient and measurement of the magnetic field and 3) identifying the radiation spectrum of the instability. Preliminary results from phase one will be presented along with the progress and diagnostic design for the following phases of the experiment.
138041514
GENERATION AND CHARACTERIZATION OF 5-MICRON ELECTRON BEAM FOR PROBING OPTICAL SCALE STRUCTURES
In recent years advanced acceleration technologies have progress toward combination of electron beam, laser and optical scale dielectric structures. In present paper described generation of the electron beam probe with parameters satisfied to perform test of such optical structures.
117206415
Event‐by‐Event Energy Estimation and Spectral Determination with Milagro
The observed characteristics of a TeV gamma ray shower which triggers Milagro depend on core location, zenith angle, and primary energy. An algorithm to estimate the primary energy on an event‐by‐event basis based upon observed quantities has been devised. This algorithm is applied to signals observed from sources to determine energy spectra in the energy range 1 to 100 TeV. Results for spectral determination are presented for the Crab nebula. For the Crab nebula our results are similar to atmospheric Cherenkov telescope measurements.
121348159
Measurement of the Crab spectrum with Milagro
Through use of new algorithms for estimating γ-ray and cosmic ray primary energies of events in Milagro we determine the energy spectra of gamma rays from the Crab nebula and spectra of Milagro background triggers have been determined in the energy range 1 to 100 TeV. The measured spectra are compared with those measured by ACT techniques and direct measurements of cosmic ray spectra.
119464489
Cosmic microwave background radiation anisotropy induced by cosmic strings
We report on a current investigation of the anisotropy pattern induced by cosmic strings on the cosmic microwave background radiation (MBR). We have numerically evolved a network of cosmic strings from a redshift of Z = 100 to the present and calculated the anisotropies which they induce. Based on a limited number of realizations, we have compared the results of our simulations with the observations of the COBE-DMR experiment. We have obtained a preliminary estimate of the string mass-per-unit-length µ in the cosmic string scenario.
118291149
The Effective Potential In De Sitter Space
124123364
Comments on the Doorway State in Pb 206
The neutron capture cross section of $^{206}\mathrm{Pb}(n, \ensuremath{\gamma})$ has been measured with high resolution at the Oak Ridge electron linear accelerator. The capture results show that the reported ${s}_{\frac{1}{2}}$ doorway in $^{206}\mathrm{Pb}$ is not observed in the photon channel.