111239993
MODELING AND EXPERIMENTS ON INJECTION INTO UNIVERSITY OF MARYLAND ELECTRON RING
The University of Maryland Electron Ring (UMER) is built as a low‐cost testbed for intense beam physics for benefit of larger ion accelerators. The beam intensity is designed to be variable, spanning the entire range from low current operation to highly space‐charge‐dominated transport. The ring has been closed and multi‐turn commissioning has begun. One of the biggest challenges of multi‐turn operation of UMER is correctly operating the Y‐shaped injection/recirculation section, which is specially designed for UMER multi‐turn operation. It is a challenge because the system requires several quadrupoles and dipoles in a very stringent space, resulting in mechanical, electrical, and beam control complexities. Also, the Earth’s magnetic field and the image charge effects have to be investigated because they are strong enough to impact the beam centroid motion. This paper presents both simulation and experimental study of the beam centroid motion in the injection region to address above issues.
9813062
Space-charge-dominated phenomena in the UMER source region
For space-charge-dominated beams, details of the beam distribution as it emerges from the source region can strongly influence beam evolution well downstream. This occurs because collective space-charge modes, excited as the beam is born, can remain undamped for many focusing periods. Nevertheless, traditional studies of the source region in particle beam systems have emphasized the behavior of averaged beam characteristics such as total current, rms beam size, or emittance, rather than the details of the full beam distribution function that are necessary to predict the excitation of any collective space-charge modes. Simulations of the source region using the particle-in-cell WARP code along with detailed comparisons to experimental measurements of the beam in the University of Maryland Electron Ring (UMER) are therefore being employed to understand the complex behavior that has been observed in the source region, including a surprising sensitivity of the beam evolution to details of the transverse velocity distribution.
119603668
Tomography as a diagnostic tool for phase space mapping of intense particle beams
A technique is described for the tomographic mapping of transverse phase space in beams with space charge. Most prior studies where performed at high energy where space charge was negligible and therefore not considered in the analysis. The tomographic reconstruction process is compared with results of simulations using the particle-in-cell code WARP. The new tomographic technique is tested for beams with different intensities (both emittance and space-charge dominated), and with different initial distributions. Effects of various errors in the data collection process on the reconstructed phase space are discussed. It is shown that the crucial factor is not necessarily the number of projections but the range of angles over which the projections are taken. This study also includes a number of experimental results on tomographic phase space mapping performed on the University of Maryland Electron Ring.
116947856
Hypernuclear fine structure in (Lambda*)Be-9
With a germanium detector array (Hyperball), we observed two γ-ray peaks corresponding to the two transitions (5/2 + → ½ + and 3/2 + → ½ + ) in the 9 A Be hypernucleus which was produced by the 9 Be(K - , π - ) reaction.The energies of the y rays are 3029 ′ 2 ′ 1 keV and 3060 ′ 2 ′ 1 keV. The energy difference was measured to be 31.4 + 2 . 5 - 3 . 6 keV, which indicates a very small A-spin-dependent spin-orbit force between a A and a nucleon. This is the smallest level splitting by far ever measured in a hypernucleus.
126136900
Threshold Measurement of the Reaction $\bar{p} p \to \bar{\ell}$ambda $\lambda$ at {LEAR}
29456018
Electromagnetic excitation of the delta resonance in nuclei.
Inclusive cross sections for the proton and nuclear targets of A = 4, 9, 12, and 16 were measured for 537 and 730 MeV electrons scattered at 37.1 deg. Systematic features of the continuum scattering data are compared with other electron scattering data and with photoabsorption measurements. A model calculation based on the isobar-hole formalism is compared with the data in the delta resonance region.
122467530
Measurement of the KL--> mu+mu-gamma Branching Ratio and Form Factor From KTeV
119115234
Z Boson Asymmetry Measurements at the Tevatron
We present measurements of the forward-backward asymmetry (A_fb) in dilepton pair decays of Z bosons produced in ppbar collisions using the full Tevatron dataset. The CDF experiment extracts a value for the effective weak mixing angle parameter sin^{2}\theta^{l}_{eff} of 0.2315 +/- 0.0010 from the A_fb distribution of dimuon events in 9.2 fb^{-1} of integrated luminosity. From dielectron events in 9.7 fb^{-1} of data, the D0 experiment finds sin^{2}\theta^{l}_{eff} = 0.23106 +/- 0.00053, the world's most precise measurement of sin^{2}\theta^{l}_{eff} from hadron colliders and with light quark couplings.