Hefei Advanced Light Source Research Articles

Error study and correction of Hefei Advanced Light Source

Hefei Advanced Light Source (HALS) is a future diffraction limited storage ring. The machine performance under all kinds of magnet errors is a vital component in physical design. In this paper, we present our work on the closed orbit correction, the linear beam optics compensation and the coupling control in HALS. After correction, the dynamical aperture can suffice the injection scheme.

Establishing A Laser Treatment To Suppress The Sec-Ondary Electron Emission

Laser treatment has a significant influence on suppressing the secondary electron emission (SEE) in electron storage rings. A new synchrotron radiation light source, the Hefei Advanced Light Source(HALS), is under consideration and it has a strict requirement to suppress the SEE. In this paper, we used a laser with the wavelength of 355nm to process with copper sample. After the laser treatment, the secondary electron yield (SEY) reduces from 2.05 to 0.86. We also used the scanning electron microscope (SEM) to analysis the surface of the sample after the laser treatment. This paper reports the experiment set up and preliminary results.

Research and design of digital magnet power supply controller for HALS

Hefei Advanced Light Source (HALS) is the fourth-generation radiation light source in China which is under design. Ultra-low beam emittance requires higher performance of power supply system. The power supply controller is a key part of the power system. This article describes the design and testing of high-stability power controllers and fast corrector power supply controllers. A new controller architecture is proposed for the problems of the two controllers.

Research progress of power supply system in HALS

Hefei Advanced Light Source (HALS) is the fourth generation light source in China's planning and construction. In order to achieve the diffraction limit of the emission and improve the beam quality, the research on magnet power supply (MPS) technology is essential. We have designed a variety of solutions for different power supplies. We designed the first version of the high stability power supply control card. The first version of the high-stability power supply control card was designed and tested with a small power module. Our pre-research system has developed a corrector magnet power supply with a small signal response bandwidth higher than 10 kHz. The developed prototypes use self-developed controllers, and most of the test results can meet the requirements. This article describes the progress of the HALS power supply system.

The design and preliminary test of a stripline kicker for HALS

Stripline kicker is an important component of both on-axis longitudinal accumulation [1] and on-axis swap out injection schemes in HALS (Hefei Advanced Light Source). After more than one year of R&D, construction of the first prototype is completed. The kicker performance is simulated. The results show that in the range of 0 ~ 1 GHz, on differential mode, S11 is less than - 20 dB. In order to facilitate installation, the extension part and PTEF bracket were designed. The assembly of kicker and commercial feedthrough has been tested with pulse generator and network analyzer.

Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-research Project of HALS

A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.

The prototype of equipment protection system based on Ethernet POWERLINK for HALS

Abstract The Hefei Advanced Light Source (HALS) is brought forward to be a new diffraction limited storage ring (DLSR) light source. The technical pre-research project for the HALS is in progress. As an critical part of the project, a prototype of the equipment protection system (EPS) is developed to study the interlock protection for components of the light source. The prototype of the EPS is a distributed system based on Gigabit Ethernet POWERLINK (EPL) under EPICS architecture. A PC is used as the master managing node (MN), and 10 FPGA-based controllers is employed for the slave controlled nodes (CNs). EPL is used for the communication between the MN and CNs. This paper reports the design and results of a series of performance tests of the prototype system. The test results indicate that the prototype system can run stably with a communication cycle time 275 μ s , and the maximum global response time is about 870 μ s . This system is a feasible solution for the EPS of large-scale scientific facilities. In the further studies, the response time is expected to be further reduced by choosing high-speed photo couplers and properly arranged input signals.

A Fast-Response and High-Stability Power Supply for a Corrector Magnet in HALS

The beam quality of the new synchrotron radiation light source Hefei Advanced Light Source (HALS) requires a fast-responding, high-stability, magnet power supply (MPS). Inspired by the commercial electronic load and audio amplifier circuits, we designed a bipolar power supply that utilizes the linear amplification characteristics of the metal–oxide–semiconductor field-effect transistor (MOSFET) to improve the balance between the response speed and the resolution of the switching power supply. The frequency response of the designed power supply can reach 10 kHz and the long-term stability can reach 5 ppm. In addition, the ±10-A rated output power supply can resolve current changes of 0.1 mA. This article describes in detail the topology of the power supply, the feedback control strategy, and the design of the digital control card. Finally, the test platform construction, performance test methods, and final experimental results of the prototype are presented.

Simulation study of longitudinal injection scheme for HALS with a higher harmonic cavity system

Longitudinal injection is a promising on-axis injection scheme for diffraction-limited storage rings. In the latest version of the Hefei advanced light source (HALS), both the dynamic aperture and momentum aperture have been optimized. A longitudinal injection scheme was investigated on the HALS using a double-frequency radio frequency system. To evaluate the injection performance, various errors were considered. A series of tracking simulations were conducted, and the injection efficiency was obtained under different error levels.

Generation of two-color polarization-adjustable radiation pulses for storage ring light source

To date, two-color pulses are widely used in pump–probe experiments. For a ring-based light source, the power of the spontaneous radiation fluctuates randomly in the longitudinal direction. It is difficult to produce two-color double pulses by optical methods. In this paper, we introduce a method based on the echo-enabled harmonic generation scheme that generates two-color pulses in a storage ring light source. By adopting crossed undulators and a phase shifter, the polarization of the two-color pulses can be easily switched. A numerical simulation based on a diffraction-limited storage ring, the Hefei Advanced Light Source, suggests that the time delay and spectral separation of the two pulses can be adjusted linearly by changing the pulse duration and chirp parameters of the seed laser. A circular polarization degree above 80% could be achieved.

Simulation of beam gas coulomb scattering in HALS**Supported by Natural Science Foundation of China (11175182, 11175180)

In conventional research on beam gas coulomb scattering (BGCS), only the related beam lifetime using the analytical method is studied. In this paper, using the particle-in-cell Monte Carlo collisions (PIC-MCC) method, we not only simulated the beam lifetime but also explored the effect of BGCS on the beam distribution. In order to better estimate the effect on particle distribution, we study the ultra-low emittance electron beam. Here we choose the HeFei Advanced Light Source. By counting the lost particles in a certain time, the corresponding beam lifetime we simulated is 4.8482 h/13.8492 h in x/y, which is very close to the theoretic value (5.0555 h /13.7024 h in x/y). By counting the lost particles relative to the collided particles, the simulated value of the loss probability of collided particles is 1.3431e-04, which is also very close to the theoretical value (1.3824e-04). Besides, the simulation shows there is a tail in the transverse distribution due to the BGCS. The close match of the simulation with the theoretic value in beam lifetime and loss probability indicates our simulation is reliable.

Physics issues in diffraction limited storage ring design

Diffraction limited electron storage ring is considered a promising candidate for future light sources, whose main characteristics are higher brilliance, better transverse coherence and better stability. The challenge of diffraction limited storage ring design is how to achieve the ultra low beam emittance with acceptable nonlinear performance. Effective linear and nonlinear parameter optimization methods based on Artificial Intelligence were developed for the storage ring physical design. As an example of application, partial physical design of HALS (Hefei Advanced Light Source), which is a diffraction limited VUV and soft X-ray light source, was introduced. Severe emittance growth due to the Intra Beam Scattering effect, which is the main obstacle to achieve ultra low emittance, was estimated quantitatively and possible cures were discussed. It is inspiring that better performance of diffraction limited storage ring can be achieved in principle with careful parameter optimization.

Conceptual design of Hefei Advanced Light Source (HALS) injection system

The Hefei Advanced Light Source(HALS) is a super low emittance storage ring and has a very short beam life time. In order to run the ring stablely, top-up injection will be necessary. The injection system will greatly affect the quality of beam. This article first gives a physics design of the injecting system. Then the injecting system is tracked under different errors. The responses of storage beam and injecting beam are given in the article.

Conceptual design of Hefei advanced light source

The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, on-momentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm · rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.