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.
121916752
Emittance measurement and modeling for the Fermilab Booster
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.
73562312
Lattice Calibration with Turn-By-Turn BPM Data
Turn-by-turn beam position monitor (BPM) data from multiple BPMs are fitted with a tracking code to calibrate magnet strengths in a manner similar to the well known LOCO code. Simulation shows that this turn-by-turn method can be a quick and efficient way for optics calibration. The method is applicable to both linacs and ring accelerators. Experimental results for a section of the SPEAR3 ring is also shown.
40726551
ELECTRON TRAPPING IN WIGGLER AND QUADRUPOLE MAGNETS OF CESRTA
The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D [1]. One of the primary goals of the CesrTA program is to investigate the interaction of the electron cloud with low emittance positron beam to explore methods to suppress the electron cloud, develop suitable advanced instrumentation required for these experimental studies and benchmark predictions by simulation codes. This paper reports the simulation of the electron-cloud formation in the wiggler and quadrupole magnets using the 3D code CLOUDLAND. We found that electrons can be trapped with long lifetime in a quadrupole magnet due to the mirror field trapping mechanism and photoelectrons produced in the wiggler zero field zone have long lifetime due to their complicated trajectory.
11909349
Simulation of ultra-short pulses in a storage ring
Simulation study was performed with the tracking code Elegant [M. Borland, APS Report LS-287] to show beam quality evolution for a short, intense electron bunch after being injected to the SPEAR3 storage ring. The electron bunch with an intensity of 1 mA (0.78 nC) and a length of nearly 1 ps (FWHM) is found to degrade rapidly due to coherent synchrotron radiation (CSR) which causes large uneven longitudinal phase space distortion. The bunch length remains short and the longitudinal line density remains smooth for about 10 turns. For such a beam to circulate in the ring, a total of 10 MV rf power is needed to compensate for the energy loss.
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.
119190505
Kubo formulas for relativistic fluids in strong magnetic fields
Magnetohydrodynamics of strongly magnetized relativistic fluids is derived in the ideal and dissipative cases, taking into account the breaking of spatial symmetries by a quantizing magnetic field. A complete set of transport coefficients, consistent with the Curie and Onsager principles, is derived for thermal conduction, as well as shear and bulk viscosities. It is shown that in the most general case the dissipative function contains five shear viscosities, two bulk viscosities, and three thermal conductivity coefficients. We use Zubarev's non-equilibrium statistical operator method to relate these transport coefficients to correlation functions of the equilibrium theory. The desired relations emerge at linear order in the expansion of the non-equilibrium statistical operator with respect to the gradients of relevant statistical parameters (temperature, chemical potential, and velocity.) The transport coefficients are cast in a form that can be conveniently computed using equilibrium (imaginary-time) infrared Green's functions defined with respect to the equilibrium statistical operator. - Highlights: > Strong magnetic fields can make charged fluids behave anisotropically. > Magnetohydrodynamics for these fluids contains 5 shear, 2 bulk viscosities, and 3 heat conductivities. > We derive Kubo formulas for these transport coefficients.
119294799
Electric fields and chiral magnetic effect in Cu + Au collisions
Abstract The non-central Cu + Au collisions can create strong out-of-plane magnetic fields and in-plane electric fields. By using the HIJING model, we study the general properties of the electromagnetic fields in Cu + Au collisions at 200 GeV and their impacts on the charge-dependent two-particle correlator γ q 1 q 2 = 〈 cos ⁡ ( ϕ 1 + ϕ 2 − 2 ψ RP ) 〉 (see main text for definition) which was used for the detection of the chiral magnetic effect (CME). Compared with Au + Au collisions, we find that the in-plane electric fields in Cu + Au collisions can strongly suppress the two-particle correlator or even reverse its sign if the lifetime of the electric fields is long. Combining with the expectation that if γ q 1 q 2 is induced by elliptic-flow driven effects we would not see such strong suppression or reversion, our results suggest to use Cu + Au collisions to test CME and understand the mechanisms that underlie γ q 1 q 2 .
118405311
Superfluidity and collective modes in Rashba spin-orbit coupled Fermi gases
Abstract We present a theoretical study of the superfluidity and the corresponding collective modes in two-component atomic Fermi gases with s -wave attraction and synthetic Rashba spin–orbit coupling. The general effective action for the collective modes is derived from the functional path integral formalism. By tuning the spin–orbit coupling from weak to strong, the system undergoes a crossover from an ordinary BCS/BEC superfluid to a Bose–Einstein condensate of rashbons. We show that the properties of the superfluid density and the Anderson–Bogoliubov mode manifest this crossover. At large spin–orbit coupling, the superfluid density and the sound velocity become independent of the strength of the s -wave attraction. The two-body interaction among the rashbons is also determined. When a Zeeman field is turned on, the system undergoes quantum phase transitions to some exotic superfluid phases which are topologically nontrivial. For the two-dimensional system, the nonanalyticities of the thermodynamic functions and the sound velocity across the phase transition are related to the bulk gapless fermionic excitation which causes infrared singularities. The superfluid density and the sound velocity behave nonmonotonically: they are suppressed by the Zeeman field in the normal superfluid phase, but get enhanced in the topological superfluid phase. The three-dimensional system is also studied.
119185690
Hermiticity of the Dirac Hamiltonian in curved spacetime
In previous work on the quantum mechanics of an atom freely falling in a general curved background spacetime, the metric was taken to be sufficiently slowly varying on time scales relevant to atomic transitions that time derivatives of the metric in the vicinity of the atom could be neglected. However, when the time dependence of the metric cannot be neglected, it was shown that the Hamiltonian used there was not Hermitian with respect to the conserved scalar product. This Hamiltonian was obtained directly from the Dirac equation in curved spacetime. This raises the paradox of how it is possible for this Hamiltonian to be non-Hermitian. Here, we show that this non-Hermiticity results from a time dependence of the position eigenstates that enter into the Schroedinger wave function, and we write the expression for the Hamiltonian that is Hermitian for a general metric when the time dependence of the metric is not neglected.