15145205
NONLINEAR DYNAMICS IN THE SPEAR3 DOUBLE-WAIST CHICANE*
One of the two 7.6 m long straight sections in SPEAR3 has been divided into two short straights to provide places for two new small-gap insertion devices (IDs) [1,2]. A chicane generates an angular separation of 10 mrad between the two straights. A quadrupole triplet has been added in the center of the 7.6 m long chicane to create a ‘double-waist chicane’ optics with βy=1.6 m at the center of each of two future IDs. The new optics also reduces βy to 2.5 m in the four 4.8 m straight sections. In this paper, we discuss nonlinear dynamic studies associated with design and implementation of the new optics. We present tracking results generated during the design stage and compare them to nonlinear dynamics measurements made with the quadrupole triplet installed in SPEAR3. INTRODUCTION The double-waist chicane optics were designed over the course of four years, culminating in final optics design reviews in 2004 [1]. Details of the linear optics design can be found in these proceedings [2]. The new optics has reduced βy at six locations, with stronger focusing, higher vertical tune and chromaticity, and stronger sextupole strengths. The new quadrupole triplet was installed in SPEAR3 in summer, 2005, to enable testing of the new optics during the 2005-2006 run. Measurements over the past several months have shown that the optics perform as expected, with good injection and lifetime. Delivery of user beam in the new optics will start this fall. This paper will present the nonlinear dynamics tracking studies that were done for the 2004 optics design reviews, and will compare the tracking to subsequent beam measurements. TRACKING STUDIES Figures 1 and 2 compare dynamic aperture tracking in AT [3] for the old optics and the new, double-waist chicane optics. The tracking setup includes: • Symplectic integration for insertion devices [4], including BL11 with end correctors [5]. • Random and systematic magnet multipoles. • 5 mm vertical physical half aperture from IDs. • ~15 random magnet error seeds, each with 1% beta-beat and coupling. • 10,000 turns, synchrotron oscillations, radiation, ξx,y=+1.0,+1.25. Tracking without insertion devices (IDs) showed that the old optics had a larger dynamic aperture, but with IDs the dynamic apertures are comparable (Figs 1, 2). The aperture for negative x is particularly important, because the injected beam arrives on the inside of the ring. The off-energy (blue) dynamic aperture is also similar in the old and new optics. This is critical for the two dominant lifetime effects in SPEAR3: bremsstrahlung and Touschek scattering. -0.025 -0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02 0.025 0 1 2 3 4 5 x 10 -3 X0 [m] Y 0 [m ] Baseline with IDs, DAPA On Energy Best/Worst On Energy Mean 3% Best/Worst 3% Mean Figure 1: Dynamic aperture tracking at injection point for old optics with IDs. Envelope shows multiple error seeds. -0.025 -0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02 0.025 0 1 2 3 4 5 x 10 -3 DW with IDs, DAPA
18932536
Bunch length measurements in SPEAR3
A series of bunch length measurements were made in SPEAR3 for two different machine optics. In the achromatic optics the bunch length increases from the low-current value of 16.6 ps rms to about 30 ps at 25 ma/bunch yielding an inductive impedance of -0.17 Omega. Reducing the momentum compaction factor by a factor of ~60 [1] yields a low-current bunch length of ~4 ps rms. In this paper we review the experimental setup and results.
73565205
Bunch Length Measurements With Laser/SR Cross-Correlation
By operating SPEAR3 in low-{alpha} mode the storage ring can generate synchrotron radiation pulses of order 1ps. Applications include pump-probe x-ray science and the production of THz radiation in the CSR regime. Measurements of the bunch length are difficult, however, because the light intensity is low and streak cameras typically provide resolution of only a few ps. Tests are now underway to resolve the short bunch length using cross-correlation between a 60-fs Ti:Sapphire laser and the visible SR beam in a BBO crystal. In this paper we report on the experimental setup, preliminary measurements and prospects for further improvement.
36577415
Application of independent component analysis to Fermilab Booster
Autocorrelation is applied to analyze sets of finite-sampling data such as the turn-by-turn beam position monitor (BPM) data in an accelerator. This method of data analysis, called the independent component analysis (ICA), is shown to be a powerful beam diagnosis tool for being able to decompose sampled signals into its underlying source signals. They find that the ICA has an advantage over the principle component analysis (PCA) used in the model-independent analysis (MIA) in isolating independent modes. The tolerance of the ICA method to noise in the BPM system is systematically studied. The ICA is applied to analyze the complicated beam motion in a rapid-cycling booster synchrotron at the Fermilab. Difficulties and limitations of the ICA method are also discussed.
121916752
Emittance measurement and modeling for the Fermilab Booster
117893818
Compensation of dogleg effect in Fermilab Booster
The edge focusing of dogleg magnets in Fermilab Booster has been causing severe distortion to the horizontal linear optics. The doglegs are vertical rectangular bends, therefore the vertical edge focusing is canceled by body focusing and the overall effect is focusing in the horizontal plane. The maximum horizontal beta function is changed from 33.7m to 46.9m and maximum dispersion from 3.19m to 6.14m. Beam size increases accordingly. This is believed to be one of the major reasons of beam loss. In this technote we demonstrate that this effect can be effectively corrected with Booster's quadrupole correctors in short straight sections (QS). There are 24 QS correctors which can alter horizontal linear optics with negligible perturbation to the vertical plane. The currents of correctors are determined by harmonic compensation, i.e., cancellation of dogleg's harmonics that are responsible for the distortion with that of QS correctors. By considering a few leading harmonics, the ideal lattice can be partly restored. For the current dogleg layout, maximum {beta}{sub x} is reduced to 40.6m and maximum D{sub x} is reduced to 4.19m. This scheme can be useful after the dogleg in section No.3 is repositioned. In this case it can bring {beta}{sub x} from 40.9m down to 37.7m, D{sub x} from 4.57m to 4.01m.
119193640
Clarifying some remaining questions in the anomaly puzzle
We discuss several points that may help to clarify some questions that remain about the anomaly puzzle in supersymmetric theories. In particular, we consider a general $\mathcal{N}=1$ supersymmetric Yang–Mills theory. The anomaly puzzle concerns the question of whether there is a consistent way in the quantized theory to put the R-current and the stress tensor in a single supermultiplet called the supercurrent, even though in the classical theory they are in the same supermultiplet. It was proposed that the classically conserved supercurrent bifurcates into two supercurrents having different anomalies in the quantum regime. The most interesting result we obtain is an explicit expression for the lowest component of one of the two supercurrents in 4-dimensional spacetime, namely the supercurrent that has the energy-momentum tensor as one of its components. This expression for the lowest component is an energy-dependent linear combination of two chiral currents, which itself does not correspond to a classically conserved chiral current. The lowest component of the other supercurrent, namely, the R-current, satisfies the Adler–Bardeen theorem. The lowest component of the first supercurrent has an anomaly, which we show is consistent with the anomaly of the trace of the energy-momentum tensor. Therefore, we conclude that there is no consistent way to construct a single supercurrent multiplet that contains the R-current and the stress tensor in the straightforward way originally proposed. We also discuss and try to clarify some technical points in the derivations of the two supercurrents in the literature. These latter points concern the significance of infrared contributions to the NSVZ β-function and the role of the equations of motion in deriving the two supercurrents.
119248497
Strange quark matter in strong magnetic fields within a confining model
model. The confinement is modeled by means of the Richardson potential for quark-quark interaction modified suitably to account for a strong magnetic field. We compare our results for the equation of state and magnetization of matter to those derived within the MIT bag model. The differences between these models arise mainly due to the momentum dependence of the strong interaction between quarks in the Richardson model. Specifically, we find that the magnetization of strange quark matter in this model �
54948502
Chiral electric separation effect in the quark-gluon plasma
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient σχe, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=σχe(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure σχe∝μμ5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density μ5 ≠ 0. Using the Hard-Thermal-Loop framework, the CESE conductivity for the QGP is found to be σχe = (#)TTrfQeQA/g⁴ln(1/g) μμ5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.
118465675
Anisotropic hydrodynamics, bulk viscosities, and r -modes of strange quark stars with strong magnetic fields
In strong magnetic fields the transport coefficients of strange quark matter become anisotropic. We determine the general form of the complete set of transport coefficients in the presence of a strong magnetic field. By using a local linear response method, we calculate explicitly the bulk viscosities {zeta}{sub perpendicular} and {zeta}{sub ||} transverse and parallel to the B field, respectively, which arise due to the nonleptonic weak processes u+s{r_reversible}u+d. We find that for magnetic fields B 10{sup 18} G, the dependence of both {zeta}{sub perpendicular} and {zeta}{sub ||} on the field is strong, and they exhibit de Haas-van Alphen-type oscillations. With increasing magnetic field, the amplitude of these oscillations increases, which eventually leads to negative {zeta}{sub perpendicular} in some regions of parameter space. We show that the change of sign of {zeta}{sub perpendicular} signals a hydrodynamic instability. As an application, we discuss the effects of the new bulk viscosities on the r-mode instability in rotating strange quark stars. We find that the instability region in strange quark stars is affectedmore » when the magnetic fields exceed the value B=10{sup 17} G. For fields which are larger by an order of magnitude, the instability region is significantly enlarged, making magnetized strange stars more susceptible to r-mode instability than their unmagnetized counterparts.« less
119286304
Z'-gauge Bosons as Harbingers of Low Mass Strings
Massive Z'-gauge bosons act as excellent harbingers for string compactifications with a low string scale. In D-brane models they are associated to U(1) gauge symmetries that are either anomalous in four dimensions or exhibit a hidden higher dimensional anomaly. We discuss the possible signals of massive Z'-gauge bosons at hadron collider machines (Tevatron, LHC) in a minimal D-brane model consisting out of four stacks of D-branes. In this construction, there are two massive gauge bosons, which can be naturally associated with baryon number B and B-L (L being lepton number). Here baryon number is always anomalous in four dimensions, whereas the presence of a four-dimensional B-L anomaly depends on the U(1)-charges of the right handed neutrinos. In case B-L is anomaly free, a mass hierarchy between the two associated Z'-gauge bosons can be explained. In our phenomenological discussion about the possible discovery of massive Z'-gauge bosons, we take as a benchmark scenario the dijet plus W signal, recently observed by the CDF Collaboration at Tevatron. It reveals an excess in the dijet mass range 150 GeV/c^2, 4.1\sigma beyond SM expectations. We show that in the context of low-mass string theory this excess can be associated with the production and decay of a leptophobic Z', a singlet partner of SU(3) gluons coupled primarily to baryon number. Even if the CDF signal disappears, as indicated by the more recent D0 results, our analysis can still serve as the basis for future experimental search for massive Z'-gauge bosons in low string scale models. We provide the relevant cross sections for the production of Z'-gauge bosons in the TeV region, leading to predictions that are within reach of the present or the next LHC run.