Top-off Mode Research Articles

Development of a high-sensitivity tune measurement system based on diode-detection at HLS-II

We have developed a high-sensitivity tune measurement system based on diode detection for an electron storage ring, and we have carried out the tune measurement without beam excitation on the Hefei Light Source-II (HLS-II) storage ring. In this paper, we present in detail the design of the developed system for the HLS-II storage ring, and have carried out the simulations and experiments. The developed system is mainly composed of the analog front-end (AFE), spectrum analyzer, and host computer. We verified the performance of the AFE by simulation and offline experiment. In the experiment, we employed the host computer for real-time observation of the tune. As a result, the online experiments of the developed system on the HLS-II storage ring show a good signal-to-noise ratio of about 25 dB in the top-off mode without beam excitation. Compared with the conventional tune measurement system of the electron storage ring, the advantages of our system are its simple structure, low cost, and no beam excitation is required.

Upgrade of low level RF system based on Micro Telecom Computing Architecture (MTCA) for HLS-II LINAC

The performance of Hefei Light Source II (HLS-II) has improved a lot after major maintenance and reconstruction. To further provide continuous and stable light, the RF system of the HLS-II LINAC needs to be upgraded for top-off mode. It is required that the RF power source have long-time stability and reliability, but the old analog low level RF system(LLRF) can’t meet the requirement. Hence a digital low level RF control system based on Micro Telecom Computing Architecture(MTCA) is designed and implemented to control the amplitude and phase of the RF power source. This system is composed of digital board cards based on FPGA, RF board cards, MTCA chassis and a frequency synthesis system. It works at 2856 MHz of S band, with phase and amplitude stability up to 0.2° and 0.04% respectively, which meets the top-off mode requirement of 0.25° RMS phase jitter of the digital low-level RF system in the HLS-II LINAC.

Shielding calculations for the National Synchrotron Light Source-II experimental beamlines

Brookhaven National Laboratory is in the process of building a new Electron storage ring for scientific research using synchrotron radiation. This facility, called the “National Synchrotron Light Source II” (NSLS-II), will provide x-ray radiation of ultra-high brightness and exceptional spatial and energy resolution. It will also provide advanced insertion devices, optics, detectors, and robotics, designed to maximize the scientific output of the facility. The project scope includes the design of an electron storage ring and the experimental beamlines, which stores a maximum of 500mA electron beam current at an energy of 3.0GeV. When fully built there will be at least 58 beamlines using synchrotron radiation for experimental programs. It is planned to operate the facility primarily in a top-off mode, thereby maintaining the maximum variation in the synchrotron radiation flux to <1%. Because of the very demanding requirements for synchrotron radiation brilliance for the experiments, each of the 58 beamlines will be unique in terms of the source properties and experimental configuration. This makes the shielding configuration of each of the beamlines unique. The shielding calculation methodology and the results for five representative beamlines of NSLS-II, have been presented in this paper.

Radiological considerations for bulk shielding calculations of national synchrotron light source-II

Abstract Brookhaven National Laboratory is designing a new electron synchrotron for scientific research using synchrotron radiation. This facility, called the “National Synchrotron Light Source II” (NSLS-II), will provide x-ray radiation of ultra-high brightness and exceptional spatial and energy resolution. It will also provide advanced insertion devices, optics, detectors and robotics, and a suite of scientific instruments designed to maximize the scientific output of the facility. The project scope includes the design, construction, installation, and commissioning of the following accelerators: a 200 MeV linac, a booster synchrotron operating from 200 MeV to 3.0 GeV, and the storage ring which stores a maximum of 500 mA current of electrons at an energy of 3.0 GeV. It is planned to operate the facility primarily in a top-off mode, thereby maintaining the maximum variation in stored beam current to

Top-Off Injection and Higher Currents at the Stanford Synchrotron Radiation Lightsource

The Stanford Synchrotron Radiation Lightsource (SSRL) at the SLAC National Accelerator Laboratory (SLAC) is currently working on increasing its stored current from originally 100 to 500 mA. SSRL worked with the SLAC Radiation Protection Department on mitigating the possible radiological hazards from these upgrades. This paper describes the related analyses, new safety systems, and beam tests. The top-off injection mode (injection with beamline stoppers open) is essential for operation at high currents. The radiological consequences of various situations were analyzed, a new Beam Containment System (BCS) was implemented, and radiation surveys were performed during tests. Since March 2010, all beamlines have been operating in top-off mode. Operation with higher beam currents was also analyzed for radiological hazards, and a new Beamline BCS was installed. The storage ring is now operating with 200 mA during user runs, and tests are ongoing with higher beam currents. Soon the power of the injection current will also be raised from 1.5 W at present to 5 W maximal.

Maximizing integrated brightness in Touschek-dominated synchrotron light sources

We present a numerical study to maximize the integrated performance of third generation synchrotron radiation sources for cases where the beam lifetime is dominated by large-angle intrabeam (Touschek) scattering. The performance is characterized in two areas of user interest: high brightness and total flux. We study the effect on the time integral of these quantities through varying parameters such as the lifetime, vertical beam emittance, time between fills, filling time, and total beam current. The effect on topoff mode of operation in also discussed.