PEPX-type lattice design and optimization for the High Energy Photon Source

A new generation of storage ring-based light source, called diffraction-limited storage ring (DLSR), with the emittance approaching the diffraction limit for multi-keV photons by using the multi-bend achromat lattice, has attracted worldwide and extensive studies of several laboratories, and been seriously considered as a goal of upgrading the existing facilities in the imminent future. Among various DLSR proposals, the PEPX design based on the third-order achromat concept and with the special design of a high-beta injection straight section demonstrated that, it is feasible to achieve sufficient ring acceptance for off-axis injection in a DLSR. For the High Energy Photon Source planned to be built in Beijing, PEPX-type lattice has been designed and continuously improved. In this paper, we report the evolution of the PEPX-type design, and discuss the main issues relevant to the linear optics design and nonlinear optimization.Comment: 9 pages, 9 figures, submitted to Chinese Physics

Pulsed sextupole injection for Beijing Advanced Photon Source with ultralow emittance

In this paper we present the physical design of the pulsed sextupole injection system for Beijing Advanced Photon Source (BAPS) with an ultralow emittance. The BAPS ring lattice is designed in such a way that two options of pulsed sextupole injection are allowed, i.e., with septum and pulsed sextupole in different drift spaces or in the same drift space. We give the magnetic parameters of the injection system and the optimal condition of the optical functions for both options. In addition, we find that the pulsed sextupole induces position-dependent dispersive effect and causes non-ignorable effect on the injection efficiency in a storage ring with a relatively small acceptance, which should be well considered

ESRF-type lattice design and optimization for the High Energy Photon Source

A new generation of storage ring-based light source, called diffraction-limited storage ring (DLSR), with emittance approaching the diffraction limit for multi-keV photons by means of multi-bend achromat lattice, has attracted worldwide and extensive studies. Among various DLSR proposals, the hybrid multi-bend achromat concept developed at ESRF predicts an effective way of minimizing the emittance and meanwhile keeping the required sextupole strengths to an achievable level. For the High Energy Photon Source planned to be built in Beijing, an ESRF-type lattice design consisting of 48 hybrid seven-bend achromats is proposed to reach emittance as low as 60 pm.rad with a circumference of about 1296 m. Sufficient dynamic aperture promising vertical on-axis injection and moderate momentum acceptance are achieved simultaneously for a promising ring performance.Comment: 8 pages, 6 figures, submitted to Chinese Physics

Suppression of the emittance growth induced by coherent synchrotron radiation in triple-bend achromats

The coherent synchrotron radiation (CSR) effect in a bending path plays an important role in transverse emittance dilution in high-brightness light sources and linear colliders, where the electron beams are of short bunch length and high peak current. Suppression of the emittance growth induced by CSR is critical to preserve the beam quality and help improve the machine performance. It has been shown that the CSR effect in a double-bend achromat (DBA) can be analyzed with the two-dimensional point-kick analysis method. In this paper, this method is applied to analyze the CSR effect in a triple-bend achromat (TBA) with symmetric layout, which is commonly used in the optics designs of energy recovery linacs (ERLs). A condition of cancelling the CSR linear effect in such a TBA is obtained, and is verified through numerical simulations. It is demonstrated that emittance preservation can be achieved with this condition, and to a large extent, has a high tolerance to the fluctuation of the initial transverse phase space distribution of the beam.Comment: 9 pages, 4 figure

CH3NH3PbI3/GeSe bilayer heterojunction solar cell with high performance

Perovskite (CH3NH3PbI3) solar cells have made significant advances recently. In this paper, we propose a bilayer heterojunction solar cell comprised of a perovskite layer combining with a IV-VI group semiconductor layer, which can give a conversion efficiency even higher than the conventional perovskite solar cell. Such a scheme uses a property that the semiconductor layer with a direct band gap can be better in absorption of long wavelength light and is complementary to the perovskite layer. We studied the semiconducting layers such as GeSe, SnSe, GeS, and SnS, respectively, and found that GeSe is the best, where the optical absorption efficiency in the perovskite/GeSe solar cell is dramatically increased. It turns out that the short circuit current density is enhanced 100% and the power conversion efficiency is promoted 42.7% (to a high value of 23.77%) larger than that in a solar cell with only single perovskite layer. The power conversion efficiency can be further promoted so long as the fill factor and open-circuit voltage are improved. This strategy opens a new way on developing the solar cells with high performance and practical applications.Comment: 8 pages, 8 figures, 3 tables, accepted by Solar Energ

Towards the ultimate storage ring: the lattice design for Beijing Advanced Photon Source

A storage ring-based light source, Beijing Advanced Photon Source (BAPS) is proposed to store 5-GeV low-emittance electron beam and to provide high-brilliance coherent radiation. In this paper, we report our efforts of pushing down the emittance of BAPS to approach the so-called ultimate storage ring, while fixing the circumference to about 1200 m. To help dealing with the challenge of beam dynamics associated with the intrinsic very strong nonlinearities in an ultralow-emittance ring, a combination of several progressive technologies is used in the linear optics design and nonlinear optimization, such as modified theoretical minimum emittance cell with small-aperture magnets, quasi-3rd-order achromat, theoretical analyzer based on Lie Algebra and Hamiltonian analysis, multi-objective genetic algorithm, and frequency map analysis. These technologies enable us to obtain satisfactory beam dynamics in one lattice design with natural emittance of 75 pm

Suppression of the emittance growth induced by CSR in a DBA cell

The Emittace growth induced by Coherent Synchrotron Radiation(CSR) is an important issue when electron bunches with short bunch length and high peak current are transported in a bending magnet. In this paper, a single kick method is introduced which could give the same result as the R-matrix method, and much easier to use. Then with this method, an optics design technique which could minimize the emittance dilution within a single achromatic cell.Comment: 7 pages, 6 figure

Highly efficient light management for perovskite solar cells

Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells

Quantum Dynamics Interpretation of Black-box Optimization

In recent decades, with the emergence of numerous novel intelligent optimization algorithms, many optimization researchers have begun to look for a basic search mechanism for their schemes that provides a more essential explanation of their studies. This paper aims to study the basic mechanism of an algorithm for black-box optimization with quantum theory. To achieve this goal, the Schroedinger equation is employed to establish the relationship between the optimization problem and the quantum system, which makes it possible to study the dynamic search behaviors in the evolution process with quantum theory. Moreover, to explore the basic behavior of the optimization system, the optimization problem is assumed to be decomposed and approximated. Then, a multilevel approximation quantum dynamics model of the optimization algorithm is established, which provides a mathematical and physical framework for the analysis of the optimization algorithm. Correspondingly, the basic search behavior based on this model is derived, which is governed by quantum theory. Comparison experiments and analysis between different bare-bones algorithms confirm the existence of the quantum mechanic based basic search mechanism of the algorithm on black-box optimization.Comment: The paper may provide a new quantum perspective for studying the basic search behavior of the intelligence algorithm

Quantum Dynamics of Optimization Problems

In this letter, by establishing the Schr\"odinger equation of the optimization problem, the optimization problem is transformed into a constrained state quantum problem with the objective function as the potential energy. The mathematical relationship between the objective function and the wave function is established, and the quantum interpretation of the optimization problem is realized. Under the black box model, the Schr\"odinger equation of the optimization problem is used to establish the kinetic equation, i.e., the Fokker-Planck equation of the time evolution of the optimization algorithm, and the basic iterative structure of the optimization algorithm is given according to the interpretation of the Fokker-Planck equation. The establishment of the Fokker-Planck equation allows optimization algorithms to be studied using dynamic methods and is expected to become an important theoretical basis for algorithm dynamics.Comment: 7 page