30244510
Microwave Instability across the Transition Energy
It is well known that during the acceleration of hadrons in a storage ring, the beam always goes above the microwave instability threshold near the transition energy ¿t. The reason is that the longitudinal revolution frequency spread of the beam which otherwise provides Landau damping vanishes at the transition energy. The amount of the beam dilution near the transition energy is determined by ¿th, the length of time when the beam stays unstable, and the growth rate of the instability. It is pointed out in this paper that ¿th is proportional to the fourth power of ¿t, and thus the choice of a large ¿t is not desirable from this point of view. An analysis is also given of the microwave instability induced beam dilution for the proposed Relativistic Heavy Ion Collider at BNL.
120908048
Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”
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.
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>>
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}
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.
117701762
Origin of Cosmic Acceleration with Large Scale Structure
The current accelerating universe can be explained by adding an exotic energy density with a negative pressure or modifying the gravity. Both the physical energy component and the modification of gravity can give rise to an effective dark energy equation of state which can characterize the expansion history of the universe. To distinguish the true origin of the cosmic acceleration, we need to know experiments giving both the expansion history of the universe and the growth rate of matter density fluctuations. Large scale structure surveys can satisfy this requirement. We investigate the Integrated Sachs Wolfe effect as one of possible methods to constrain the effective dark energy equation of state.
118846082
Perturbative non-Fermi liquids from dimensional regularization
We devise a dimensional regularization scheme for quantum field theories with Fermi surface to study scaling behaviour of non-Fermi liquid states in a controlled approximation. Starting from a Fermi surface in two space dimensions, the co-dimension of Fermi surface is extended to a general value while the dimension of Fermi surface is fixed. When Fermi surface is coupled with a critical boson centered at zero momentum, the interaction becomes marginal at a critical space dimension d_c=5/2. A deviation from the critical dimension is used as a small parameter for a systematic expansion. We apply this method to the theory where two patches of Fermi surface is coupled with a critical boson, and show that the Ising-nematic critical point is described by a stable non-Fermi liquid state slightly below the critical dimension. Critical exponents are computed upto the two-loop order.
118756118
Anisotropy due to Brans-Dicke Theory
It is well known that the viscous Bianchi type-I metric of the Kasner form is not able to describe an anisotropic universe, which satisfies the second law of thermodynamics and the dominant energy condition in Einstein's theory of gravity. We investigate this problem in Brans-Dicke theory of gravity using the Bianchi type-I metric with the perfect fluid. We show that it is possible to have the dominant energy condition and the growth of entropy in this model. Also we apply this model to explain the anomaly concerning the low quadrupole amplitude of the angular power spectrum of the temperature anisotropy observed in WMAP data.
54971266
Effects on the two-point correlation function from the coupling of quintessence to dark matter
We investigate the effects of the nonminimal coupling between the scalar field dark energy (quintessence) and the dark matter on the two-point correlation function. It is well known that this coupling shifts the turnover scale as well as suppresses the amplitude of the matter power spectrum. However, these effects are too small to be observed when we limit the coupling strength to be consistent with observations. Since the coupling of quintessence to baryons is strongly constrained, species-dependent coupling may arise. This results in a baryon bias that is different from unity. Thus, we investigate the correlation function in this coupled model. We are able to observe the enhancement of the baryon acoustic oscillation (BAO) peak due to the increasing bias factor of baryon from this species-dependent coupling. In order to avoid the damping effect of the BAO signature in the matter power spectrum due to nonlinear clustering, we consider the coupling effect on the BAO bump in the linear regime. This provides an alternative method to constrain the coupling of dark energy to dark matter.
117367144
Vector Meson Properties in Hot Dense Matter