123869228
Minimization of Primary Electron Beam Radius at the Positron Production Target
To have a high positron yield, it is extremely important to minimize the primary electron beam radius at the positron production target. Various effects on electron beam blow-up have been analyzed. By comparing the measured beam radius with simulation, result at current BEPC positron source,some concrete effects on beam blow-up have been described. A design study on minimizing the electron beam radius at BEPC-II positron source is given, and the ways to reach this goal have been summarized.
109931583
The experimental study on beam-photoelectron instability in BEPC
A vertical coupled bunch instability explained as the photoelectron instability (PEI) was observed in the photon factory at KEK. To further investigate the instability, the experiments on the PEI have been carried out in Beijing Electron Positron Collider (BEPC) with the collaboration between MEP, China and KEK, Japan. Many interesting phenomena have been observed for different sets of parameters.
108288058
Beam dynamics studies on the 100 MeV/100 kW electron linear accelerator for NSC KIPT neutron source
We designed a 100 MeV/100 kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the basis of subcritical assembly. Beam dynamics studies have been conducted to reach the design requirements (E = 100 MeV, P = 100 kW, dE/E < 1% for 99% particles). In this paper, we will present the progress of the design and the dynamic simulation results. For high intensity and long beam pulse linear accelerators, the BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at a low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced downstream of the 1st accelerating section; the unwanted particles will be collimated there.
120808467
Travelling wave accelerating structure design for TESLA positron injector linac
A modified cup-like TW accelerating structure for TESLA Positron Pre-Accelerator (PPA) is designed by optimizing the structure geometry and by changing the iris thickness cell by cell in a section. This structure has high shunt-impedance and a large iris radius to meet with the requirements of high gradient and large transverse acceptance. The beam dynamics in the structure with the optimum solenoid focus held are studied. A satisfactory positron beam transmission and the beam performance at the PPA output have been obtained. In this paper the accelerating structure design is described in detail and the results are presented. (C) 2000 Elsevier Science B.V. All rights reserved.
56291250
BEPC status and plans
BEPC operation status over the past few years with the results in exciting physics and integrated luminosity enhancement are summarized. The status of the luminosity upgrade project is described. The future plans on the tau-charm factory and the new generation light source are presented.
122385836
Study on the characteristics of linac based THz light source
There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation: coherent synchrotron radiation (CSR), synchrotron radiation (SR), low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.
9310759
Unified Field Theory and Principle of Representation Invariance
The main objectives of this article are to postulate a new principle of representation invariance (PRI), and to refine the unified field model of four interactions, derived using the principle of interaction dynamics (PID). Intuitively, PID takes the variation of the action functional under energy-momentum conservation constraint, and PRI requires that physical laws be independent of representations of the gauge groups. One important outcome of this unified field model is a natural duality between the interacting fields (g,A,Wa,Sk), corresponding to graviton, photon, intermediate vector bosons W± and Z and gluons, and the adjoint bosonic fields $(\varPhi_{\mu}, \phi^{0}, \phi^{a}_{w}, \phi^{k}_{s})$. This duality predicts two Higgs particles of similar mass with one due to weak interaction and the other due to strong interaction. The unified field model can be naturally decoupled to study individual interactions, leading to (1) modified Einstein equations, giving rise to a unified theory for dark matter and dark energy (Ma and Wang in Discrete Contin. Dyn. Syst., Ser A. 34(2):335–366, 2014), (2) three levels of strong interaction potentials for quark, nucleon/hadron, and atom respectively (Ma and Wang in Duality theory of strong interaction, 2012), and (3) two weak interaction potentials (Ma and Wang in Duality theory of weak interaction, 2012). These potential/force formulas offer a clear mechanism for both quark confinement and asymptotic freedom—a longstanding problem in particle physics (Ma and Wang in Duality theory of strong interaction, 2012).
28322811
Dynamical electron mass in a strong magnetic field
Motivated by recent interest in understanding properties of strongly magnetized matter, we study the dynamical electron mass generated through approximate chiral symmetry breaking in QED in a strong magnetic field. We reliably calculate the dynamical electron mass by numerically solving the nonperturbative Schwinger-Dyson equations in a consistent truncation within the lowest Landau level approximation. It is shown that the generation of dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass that explicitly breaks chiral symmetry in the absence of a magnetic field.
37865159
Branching ratio measurements of exclusive B+ decays to charmonium with the Collider Detector at Fermilab
We report on measurements of the branching ratios of the decays B+-->chi(c1)(0)(1P)K+ and B+-->J/psiK(+)pi(+)pi(-), where chi(c1)(0)(1P)-->J/psigamma and J/psi-->mu(+)mu(-) in p (p) over bar collisions at roots=1.8 TeV. Using a data sample from an integrated luminosity of 110 pb(-1) collected by the Collider Detector at Fermilab we measure the branching ratios to be BR(B+-->chi(c1)(0)(1P)K+)=15.5+/-5.4(stat)+/-1.5(syst)+/-1.3(br)x10(-4) and BR(B+-->J/psiK(+)pi(+)pi(-))=6.9+/-1.8(stat)+/-1.1(syst)+/-0.4(br)x10(-4) where (br) is due to the finite precision on BR(B+-->J/psiK(+)), BR(chi(c1)(0)(1P)-->J/psigamma) is used to normalize the signal yield, and (syst) encompasses all other systematic uncertainties.
118858199
SIGMOID-TO-FLUX-ROPE TRANSITION LEADING TO A LOOP-LIKE CORONAL MASS EJECTION
Sigmoids are one of the most important precursor structures for solar eruptions. In this Letter, we study a sigmoid eruption on 2010 August 1 with EUV data obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO). In AIA 94 A (Fe XVIII; 6 MK), topological reconfiguration due to tether-cutting reconnection is unambiguously observed for the first time, i.e., two opposite J-shaped loops reconnect to form a continuous S-shaped loop, whose central portion is dipped and aligned along the magnetic polarity inversion line (PIL), and a compact loop crossing the PIL. A causal relationship between photospheric flows and coronal tether-cutting reconnections is evidenced by the detection of persistent converging flows toward the PIL using line-of-sight magnetograms obtained by the Helioseismic and Magnetic Imager on board SDO. The S-shaped loop remains in quasi-equilibrium in the lower corona for about 50 minutes, with the central dipped portion rising slowly at ~10 km s–1. The speed then increases to ~60 km s–1 about 10 minutes prior to the onset of a GOES-class C3.2 flare, as the S-shaped loop speeds up its transformation into an arch-shaped loop, which eventually leads to a loop-like coronal mass ejection. The AIA observations combined with Hα filtergrams as well as hard X-ray imaging and spectroscopy are consistent with most flare loops being formed by reconnection of the stretched legs of less-sheared J-shaped loops that envelopes the rising flux rope, in agreement with the standard tether-cutting scenario.
5366774
Observation of spontaneous emitted X-ray betatron radiation in beam-plasma interactions
An experiment is being carried out at the Stanford Linear Accelerator Center (SLAC) to see if an ion channel can wiggle a beam of ultra-relativistic electrons to produce X-ray radiation. The goal is to create an intense source of undulator radiation using a plasma wiggler in the 1-10 keV range and also to determine the suitability of such an electrostatic wiggler to create a coherent beam of X-rays via the ion channel laser mechanisml. Here we give some of the scaling laws for the power and frequency distribution of the spontaneous emission from sending an electron beam through such an ion channel. Some initial experimental observations are also presented.