121212141
Active damping of the e-p instability at the Los Alamos Proton Storage Ring
A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). The feedback system configuration, setup procedures, and optimization of performance are described. Results of several experimental tests of system performance are presented including observations of instability threshold improvement and grow-damp experiments, which yield estimates of instability growth and damping rates. A major effort was undertaken to identify and study several factors limiting system performance. Evidence obtained from these tests suggests that performance of the prototype was limited by higher instability growth rates arising from beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizonta...
120417645
Snakes and spin rotators for high energy accelerators
Abstract A modification to the continuous family of snake and spin rotators, discovered by Steffen, is discussed. A compact snake configuration is found to have the advantages of requiring a smaller total integrated dipole magnet strength and a smaller transverse displacement for circulating particles. A split snake configuration has the advantage of allowing an entire experimental insertion region to be located between the two halves of the snake. Such configurations could serve as both a snake and a 90° spin rotator for experiments requiring different helicity states. General properties of these snake configurations are discussed.
96454816
Design and fabrication of a multi-purpose Panofsky magnet
A fast, flexible magnet system, consisting of a Panofsky style ferrite picture-frame magnet and pulsed power supply, has been developed. Magnet specifications are: 8 cm /spl times/8 cm aperture, 23 cm length, 500 A pulsed/l60 A DC, and 1 /spl mu/s risetime. Designed for general accelerator physics studies, the magnet may be quickly converted from dipole to quadrupole or sextupole and higher multipole configurations by easily changing winding end terminations. In the quadrupole configuration a field gradient of 0.5 T/m is achieved at 500 A. This magnet has become an important tool for nonlinear beam dynamics experiments at the IUCF Cooler Ring.<<ETX>>
117036088
Comparison of multipole expansion and exact form of the eddy current field of the AGS Booster
Studies are made on magnetic field representation using a multipole expansion as well as the exact form to calculate the magnetic field produced by eddy currents in the vacuum chamber of the AGS Booster as well as the field produced by three turn correction coils attached to the top and bottom of the vacuum chamber. The multiple representation of the chamber field does not converge to the next field when X > 30mm and limits the particle motion. When the exact form of the chamber field is used, initial amplitudes in the horizontal plane (measured at QF) can be nearly as large as the chamber half aperture. Use of three turn correction coils to compensate the eddy current fields seems to reduce rather than increase the acceptance. 6 figs., 3 tabs.
120908048
Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”
124338422
FIRST OBSERVATION OF A SNAKE DEPOLARIZING RESONANCE
Using a 104MeV stored polarized proton beam and a full Siberian snake, we recently found evidence for a so-called {open_quotes}snake{close_quotes} depolarizing resonance. A full Siberian snake forces the spin tune {nu}{sub s} to be a half integer. Thus, if the vertical betatron tune {nu}{sub y} is set near a quarter integer, then the {nu}{sub s}=n{plus_minus}2{nu}{sub y} second-order snake resonance can depolarize the beam. Indeed, with a full Siberian snake, we found a deep depolarization dip when {nu}{sub y} was equal to 4.756; moreover, when {nu}{sub y} was changed to 4.781, the deep dip disappeared and the polarization was preserved. {copyright} {ital 1997} {ital The American Physical Society}
17302634
Vector mesons in dense matter
Abstract We will summarize the progress in understanding the changes in the vector meson spectral density in nuclear medium using the constraint equations obtained from the Borel transformed dispersion relation and QCD Operator Product Expansion. We will discuss the results for the scalar mass shift and dispersion effects (three momentum dependence) for the light quark system (ϱ,ω), the strange quark system (Φ) and the heavy quark system ( J /ψ) in nuclear medium. For the light quark system, a nontrivvial change in the mass and width is expected, while the dispersion effects are found to be small. Existing model calculations for the dispersion effects are compared to the constraint equation in detail. Very small, but accurate mass shifts are obtained for the heavy quark system.
118615477
AGT on the S-duality wall
Three-dimensional gauge theory T [G] arises on a domain wall between four-dimensional $ \mathcal{N} = 4 $ SYM theories with the gauge groups G and its S-dual GL. We argue that the $ \mathcal{N} = {2^*} $ mass deformation of the bulk theory induces a mass-deformation of the theory T[G] on the wall. The partition functions of the theory T[SU(2)] and its mass-deformation on the three-sphere are shown to coincide with the transformation coefficient of Liouville one-point conformal block on torus under the S-duality.
10444896
Active cooling control of the CLEO detector using a hydrocarbon coolant farm
Abstract We describe a novel approach to particle-detector cooling in which a modular farm of active coolant-control platforms provides independent and regulated heat removal from four recently upgraded subsystems of the CLEO detector: the ring-imaging Cherenkov detector, the drift chamber, the silicon vertex detector, and the beryllium beam pipe. We report on several aspects of the system: the suitability of using the aliphatic-hydrocarbon solvent PF TM -200IG as a heat-transfer fluid, the sensor elements and the mechanical design of the farm platforms, a control system that is founded upon a commercial programmable logic controller employed in industrial process-control applications, and a diagnostic system based on virtual instrumentation. We summarize the system's performance and point out the potential application of the design to future high-energy physics apparatus.
10623913
= 4 Superconformal Chern-Simons theories with hyper and twisted hyper multiplets
We extend the = 4 superconformal Chern-Simons theories of Gaiotto and Witten to those with additional twisted hyper-multiplets. The new theories are generically linear quiver gauge theories with the two types of hyper-multiplets alternating between gauge groups. Our construction includes the Bagger-Lambert model of SO(4) gauge group. A family of abelian theories are identified with those proposed earlier in the context of the M-crystal model for M2-branes probing (2/n)2 orbifolds. Possible extension with non-abelian BF couplings and string/M-theory realization are briefly discussed.
122265337
A QCD Sum Rule Approach with an Explicit Di-quark Field
We introduce a phenomenological QCD sum rule with an explicit diquark field. We investigate certain configurations of hadrons are expected to have a good diquark structure. The parameters of the model are a diquark mass $${(m_\phi)}$$ and condensate $${(\langle \phi^2\rangle)}$$ . Assuming that Λ baryons can be represented by a diquark and a spectator quark configuration, we find the sum rule works well for Λ, Λc, and Λb. We also find a duality relation between the mass and the condensate for which the parameter sets give good Borel curves. To maintain good Borel curve, a smaller diquark condensate is needed for an increased diquark mass. Using these parameter sets, we test the diquark structure in some hadrons which contain both good and bad diquark configurations.