120340582
Edge imaging in intense beams
The appearance of rings of charge observed near the edge of beams from high-perveance guns is described with a simple ray tracing technique inspired by the particle-core model. We illustrate the technique, which has no analog in light optics, with examples from experiments employing solenoid focusing of an electron beam. The rings of charge result from the combined effects of external focusing and space-charge forces acting on paraxial fringe particles with relatively large initial transverse velocities. The model is independent of the physical mechanisms responsible for the fringe particles. Furthermore, the focal length for edge imaging in a uniform focusing channel is derived using a linearized trajectory equation for the motion of fringe particles. Counterintuitively, the focal length decreases as the beam current increases.
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.
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.
123426433
Electro-mechanical design for injection in the University of Maryland Electron Ring
Closure of the University of Maryland Electron Ring (UMER) is anticipated in May 2003. An initial prototype of the injection "Y" has been completed. Electro-mechanical aspects of the design and test results of this prototype are presented. The design incorporates an offset quadrupole and a pulsed dipole to achieve the 10-degree bend required from the injection line. To accommodate penetration of the pulsed dipole magnetic field a glass gap has been inserted at the point of injection. A fixture was used to align the sections of the assembly and serves as a permanent mount plate. A similar method will be used for extraction of the beam after the electron ring has been closed.
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.
109353411
YO! — A Time‐of‐Arrival Receiver for Removal of Femtosecond Helicity‐Correlated Beam Effects
The G0 parity violation experiment at Jefferson Lab is based on time‐of‐flight measurements, and is sensitive to timing effects between the two electron helicity states of the beam. Photon counters triggered by time‐of‐arrival at the target mandate that timing must be independent of delays associated with different orbits taken by the two helicity states. In addition, the standard 499 MHz beam structure is altered such that 1 of every 16 microbunches are filled, resulting in an arrival frequency of 31.1875 (31) MHz, and an average current of 40 μA. Helicity correction involves identifying and tracking the 31 MHz sub‐harmonic, applying a fast/fine phase correction, and finally producing a clean 31 MHz trigger and a 499 MHz clock train. These signals are phase‐matched to the beam arrival at the target on the order of femtoseconds. The 10 kHz output bandwidth is sufficiently greater than the 30 Hz helicity flip settling time (500 μs). This permits the system to correct each helicity bin for any orbit‐induced...
108516447
Carbon fiber grounding in the D0 Run IIb silicon detector design
Abstract Carbon fiber support structures have become common elements of silicon detector designs. While the use of carbon fiber solves a variety of mechanical problems, it presents a challenging set of electrical concerns. Well-designed coupling and grounding schemes are essential for producing low-noise environments within the detectors. General principles involved in grounding systems with carbon fiber structures are described, as well as specific applications to the D0 Run IIb silicon detector.
118474620
Studies of single top quark production at the Tevatron
In this paper we present several measurements of single top quark production from the CDF and D0 experiments at the Tevatron. The various analyses utilize integrated luminosity ranging from 2.1 to 4.8 fb{sup -1}. The results include the observation of single top production with a combined cross section of 2.76{sub -0.47}{sup +0.58} pb for a top quark mass of 170 GeV/c{sup 2}, as well as measurements of top quark polarization and first evidence for t-channel production.