Duohui He

Development of Measurement and Transverse Feedback System at HLS

In order to cure and damp coupled bunch (CB) instabilities caused by the high order modes (HOMs) of the RF cavity and the resistive wall impedance of the Ring vacuum chamber. HOMs are ineluctable during the operation of the accelerator. An observer system characterized by bunch by bunch measurement of transverse β oscillation and longitudinal synchrotron phase oscillation has been constructed and commissioned at Hefei Light Source (HLS) [1, 2]. A transverse bunch-by-bunch feedback system is under construction. The design and development of the observe systems, as well as diagnostics results of machine instabilities are presented in this paper.

Coherent harmonic generation experiment on Hefei Synchrotron Radiation Source

An experiment facility for coherent harmonic generation in ultraviolet spectral range has been built on the storage ring at University of Science and Technology of China. In this paper, the facility, the measurement of the spontaneous radiation spectrum of the optical klystron and preparations for coherent harmonic generation experiment are described.

Several new beam measurement systems for HLS

This paper describes several new beam instruments for Hefei light source (HLS). These new beam instruments include a tuning measurement system to measure the beam tune and chromaticity, a DCCT measurement system to measure the beam DC current and beam life, and a closed orbit measuring system to measure the beam position. Some applications of these measurement systems and their measurement results are presented.

Measurement and Research of Beam-Based Alignment With AC k-Modulation at HLS

A new beam-based alignment (BBA) measurement system with AC k-modulation module was developed recently at Hefei Light Source (HLS), which equipped the quadrupole magnets on the storage ring with a current shunt system which was able to vary the magnet current of a given quadrupole at a given frequency. The corresponding closed orbit oscillation amplitude measured for different beam positions in the quadrupole reached a minimum when the beam was centered in the quadrupole. Amplitude estimation algorithms of software lock-in amplifier and interpolated FFT were discussed. A V-shaped curve was used to determine the offset; a method using a parabola fit to determine the offset was also discussed. This BPM-to-quadrupole offset was determined at HLS with an accuracy of ~50 mum. The reproducibility of the beam based alignment using this technique is about 20 mum (RMS)

A Method to Calibrate Beam Position Monitor at HLS 200 MeV Linac

In order to improve injection efficiency of HLS 200Mev LINAC, we redesign a new strip line beam position monitor system, which is consisted of a strip line structure and a signal processing system. We decide on an online calibration method based on beam to find out the geometry centre displacement and relative gain offset. Before the BPM testing bench has been prepared, we make a simulation based on the model accounted for all factors influencing signal amplitudes and get the calibrating results. At last, we analyze the nonlinearity effect on the calibration results.

Methods of measurement for the beam-based alignment system in HLS

The beam-based alignment system is given in HLS (Hefei light source), in which a switchable shunt resistor was installed on quadrupole to bypass a small percentage of the magnet current. The system can be used to position the beam in the magnetic center of quadrupoles. In measurement, some methods (linear fitting with single corrector, parabola fitting with single corrector, linear fitting with local bump, and parabola fitting with local bump) are used. These measurement results are given, and compared among above methods.

Design and simulation of beam position monitor for 200 MeV linac in HLS

In order to improve injection efficiency of HLS (Hefei Light Source), an appropriate BPM (beam position monitor) is needed to provide the transverse positions and longitudinal phases of linac and transfer line beam. The original stripline BPM for HLS Linac, which is 20.8 degrees in azimuthal angle and has a poor performance in coupling signals on electrodes, is redesigned and calculated through Mafia and CST Microwave Studio. The new stripline BPM structure, which is 60 degrees and 183.8 mm long, has a better performance in time response, spectrum, linearity and sensitivity when a beam passes by. Lastly, the position resolution and time resolution of the new structure is theoretically calculated, which meets the requirement of HLS Linac and transfer line.

Design of S-band cavity BPM for HLS

For the development of accelerators we require increasingly precise control of beam position. Cavity BPMs promise a much higher position resolution compared to other BPM types and manufacture of cavity BPMs is in general less complicated. The cavity BPM operating at S-band for HLS (Hefei Light Source) was designed. It consists of two cavities: a position cavity tuned to TM110 mode and a reference cavity tuned to TM010 mode. To suppress the monopole modes we use waveguides as pickups. Superheterodyne receivers are used in electronics for many cavity BPMs while we decide to use chip AD8302 produced by Analog Devices to process the signals. To simulate and calculate the electromagnetic field we use MAFIA.

Application and design of photon beam position monitor in HLS

This paper described the design of a split photon beam position monitor in HLS (Hefei Light Source). The two methods of position processing are given and compared. The monitor was tested and calibrated, the results are well watched with the computed results. The photon beam position monitor has been used in a slow local orbit feedback system. The result of the slow local orbit feedback was given.

Design and Experiment of 200MeV Energy Spectrum Analysis System of Linac in NSRL

Energy Spectrum Analytic System of 200MeV Linear Accelerator in NSRL is used to measure the beam energy and energy spread. This paper shows the status of the system, and analyses a few of its shortcomings. In the NSRL phase‐II Project, the system is required to improve. The results of simulation calculation and some preliminary experiment are described.