비만아 부모의 돌봄 경험: q 방법론

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment: Editorial

The High Energy Photon Source (HEPS) is an ultralowemittance, kilometer-scale storage ring light source to be built in China. In this paper we will introduce the progress of the physical design and studies on HEPS over the past one year, covering issues of storage lattice design and optimization, booster design, injection design, collective effects, error study, insertion device effects, beam lifetime, etc.

Progress of Lattice Design and Physics Studies on the High Energy Photon Source

The High Energy Photon Source (HEPS) is a highenergy, ultralow-emittance, kilometer-scale storage ring light source to be built in China. The HEPS lattice design has been started since 2008. In this paper we will review the evolution of the HEPS lattice design over the past ten years, focusing mainly on the linear optics design and nonlinear optimization.

http://jacow.org/ipac2018/papers/tupmf049.pdf

Evolution of the Lattice Design for the High Energy Photon Source

A low-frequency quarter-wave superconducting β = 1 structure has been proposed as a main accelerating cavity for the newly planned storage ring light source with ultra-low emittance. In the development of High Energy Photon Source, a 6 GeV diffraction-limited light source at the Institute of High Energy Physics, a compact 166.6 MHz proof-of-principle cavity was designed. By optimizing its geometry, the cavity’s mechanical properties have been significantly improved with a focus on stress, pressure sensitivity, Lorentz-force detuning, microphonics and tuning capabilities. The cavity was later fabricated, post-processed and tested in a vertical manner at cryogenic temperatures. High peak electromagnetic fields have been achieved with an excellent cryogenic performance, largely exceeding the design goal and project specifications. In addition, the measured mechanical parameters are in good accordance with simulation results. Small Lorentz coefficients and low pressure sensitivities were measured during the tests. This constitutes the first demonstration of a solid low-frequency β = 1 superconducting cavity design with compact geometry and favorable mechanical properties.

The mechanical design, fabrication and tests of a 166.6 MHz quarter-wave beta=1 proof-of-principle superconducting cavity for HEPS

Studies on Collective Instabilities in HEPS

The High Energy Photon Source (HEPS) is a 6-GeV, kilometer-scale, quasi-diffraction limited storage ring light source to be built in China. Getting the first turn and approaching the closed orbit is very important in accelerator commissioning. In order to make first turn beam commissioning efficiently, we develop a MATLAB tool based on AT for automatic beam correction and closed orbit searching. The algorithm and simulation results are presented in this paper. INTRODUCTION HEPS is kilometer-scale, quasi-diffraction limited storage ring light source. Its emittance is very small, and correspondingly, its focusing is very strong. Unknown error sources may be introduced to cause large orbit distortion even beam loss when magnet manufacture and installation. It is questioned whether the beam can be survived and accumulated with such a low emittance and strong focusing when the HEPS project is being on beam commissioning for the first time. For the sake of safety and efficiency, we develop a first-turns correction code. In this code, we turn off all of the nonlinear devices firstly. As to the first one turn beam searching, we take certain number of BPMs and correctors as a section and optimize the lattice section by section, during which process single turn response matrix is used to find corrector setting as initial value. Then, on this basis, we scan the SVD mode number and ‘kick factor’ to find the kick angle that make the beam transfer as far as possible, at the same time, the orbit is smallest. This function is described in the ‘Main Step 1’ section of ‘METHOD’ part. As to the closed orbit searching, we think there is no difference to making the beam transfer multi-turns, like 20 turns. So, we take similar way like the last step, but all of the BPMs and correctors are used. The details are shown in ‘Main Step 2’ of ‘METHOD’ part. METHOD The goal of the first turns around strategy is to get the first beam when the machine is just completed. All the sextupoles, octupoles and cavities are off. Then, two main steps are used to steer the lattice and get the closed orbit. Main Step 1 Take certain number of BPMS and correctors as a group and optimize the lattice group by group until we get the first turn orbit, as shown in Fig. 1. The optimizing goal is to get the corrector setting that make the beam transfer as far as possible and the orbit be smallest. The response matrix of single turn and the SVD method are used to this goal. Figure 1: Outline of the main step 1. The Response Matrix of Single Turn It is different to the normal meaning of response matrix which is based on the conception of closed orbit. For our case, the corrector value will just affect the orbit and BPM reading behind this corrector. And so, the format of the response matrix seems like

First Turn Around Strategy for HEPS

The beam-ion interaction is a potential limitation of beam performance in electron accelerators, especially where the beam emittance is of a great concern in future ultra-low emittance light source. "Conventionally", the beam instability due to beam-ion interaction is attributed to two types of effects: ion trapping effect and fast ion effect, which emphasize the beam-ion dynamics in different time scales. Whereas, in accelerators, the beam suffers from a mixture of ion trapping effect and fast ion effect, leading to a more complicated process and requiring a self-consistent treatment. To evaluate the beam characteristics, as emittance growth under the influence from beam-ion effect, a new numerical simulation code based on the "quasi-strong-strong" model has been developed, including modules of ionization, beam-ion interaction, synchrotron radiation damping, quantum excitation, bunch-by-bunch feedback, etc. In the study, we do not regularly distinguish the ion trapping effect and the fast ion effect, but treat beam-ion interaction more generally and consistently. The lattice of High Energy Photon Source, a diffraction limit ring under construction in Beijing, is used as an example to show the beam-ion effect. It is found that in this low emittance ring, the beam-ion instability is not a dominant mechanism in operation mode with a high beam current, but seriously occurs in a lower beam current region. When the beam-ion instability were significantly driven and can not be damped by the synchrotron radiation damping, the simulations show the bunch-by-bunch feedback system based on the Finite Impulse Response filter technique can be adopted to mitigate it effectively.

Studies of the beam-ion instability and its mitigation with feedback system

A parallelized, time-dependent 3D particle simulation code is under developing to study the high-intensity beam dynamics in linear accelerators. The self-consistent space charge effect is taken into account with the Particle-InCell (PIC) method. In this paper, the structure of program and the parallel strategy are demonstrated. Then, we show the results of code verification and benchmarking. It is proved that the solvers in P-TOPO code and parallel strategy are reliable and efficient. Finally, the beam dynamics simulation of C-ADS Injector-I at IHEP are launched with P-TOPO and other codes. The possible reasons for the differences between results given by separated codes are also proposed. INTRODUCTION A new particle simulation code Parallelized-Trace of Particle Orbits (P-TOPO) is now under development to study space charge effect at high intensity linacs [1-5]. The motivation is to improve the efficiency and calculation capability, based on the OpenMP techniques, of the TOPO code [6]. In the P-TOPO code, the basic elements, which supply external field to particles in linear accelerator, such as multi-pole, solenoid, RFQ, superconducting cavities, are modelled analytically or represented by field map obtained from CST. The internal interactive space charge filed between particles is solved with the classic PIC method [7]. The Injector-I of Chinese Accelerator Driven SubCritical System (C-ADS) project is composed of ECRIS, LEBT, RFQ, MEBT1, SC section and MEBT2, which is under beam commissioning in IHEP. In recent experiment, a 10.1 MeV, 10.03 mA pulse beam is successfully achieved [8]. In this paper we will give a brief introduction of Injector-I and show the beam simulation results in detail with P-TOPO code. In section 2, the brief structure and parallelization strategy of PTOPO are introduced. In section 3, code verification and benchmarking are given. In section 4, simulation results of C-ADS Injector-I are given by P-TOPO code and other widely used codes. Several reasons are proposed to interpret the difference among results given by P-TOPO and other codes. Conclusion and summary are given in section 5. P-TOPO P-TOPO is developed with C++ language and parallelized based on the OpenMP techniques to achieve a high beam processing. Now, it can be run at PC with any number of cores. The structure of this program is as Fig. 1. 1) The MAIN class is in charge of getting the electricmagnetic field from external elements or inner space charge field, and particle updating under the effect of these obtained fields. 2) The Lattice class composed of elements class could be used to establish accelerator lattice with great flexibility. The external field supplied by certain element could be represented by a field map from CST or by analytical approximation. 3) The Beam class saves the beam information and calculates the beam parameters, like twiss parameters, emittance, beam size, et. 4) The Distribution class serves as initial particle distribution generator for specific type.

Beam Dynamics Study of C-Ads Injector-I With Developing P-Topo Code

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