BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source at Brookhaven National Laboratory. As in many other light sources, top-off injection is considered as a standard operation mode resulting in more stable beam intensity to minimize heat load variation on the beamline optics. Top off injection specifications include maintaining the stored beam current within 0.5% and the bunch to bunch charge variation within 20% bands. To make the top off commissioning smooth and efficient, a virtual machine model based on the measured beam properties was developed. The model helped to study robustness of this application operating under different conditions and optimize the input parameters. Once tested the model was transitioned to beam commissioning. To make the beam tests more efficient, the beam lifetime was controlled by adjusting RF voltage and scrapers. In this paper, we'll share the experience from the test stage to machine implementation of the top-off controls.
BNL, Upton, Long Island, New York, USA
Top Off operation is the desired mode of operation for 3rd generation light sources to ensure beam current stability for user experiments. However, top off operation introduces the hazard of injecting electrons into the front ends with the beamline shutters open. This hazard can be mitigated with the appropriate safety system. This past year, the NSLS-II has transitioned from decay mode to top off operation with the introduction of the Top Off Safety System (TOSS). Top Off was initially demonstrated September 22, 2015 and become standard mode of operating. In this paper we discuss the top off safety system, operation with the system, and future directions.
BNL, Upton, Long Island, New York, USA
Recently, NSLS-II introduced top off as the standard mode of beam delivery for the users. During top off, we are required to maintain the beam current within ±0.5% of nominal, and the bunch to bunch variation over the train less than 20% for all operating conditions. In this paper, we discuss the algorithm used for top off, simulations of various operating conditions and performance of the algorithm during operations.
BNL, Upton, Long Island, New York, USA
A Matlab interface package for Elegant simulation code is under development. This package combines advantages of Elegant, which is one of the most advanced codes for accelerator simulations, with advantages of useful and effective Matlab functions for data processing, analysis, optimization, and real-time machine control using Maltab Middle Layer. A number of functions have been already developed: calculation of lattice parameters and Twiss functions, linear and high-order chromaticity, amplitude-dependent tune shifts, modification of lattice elements, correction of betatron tunes and chromaticity, a set of functions for graphic representation. These functions have been successfully used at NSLS-II for tracking and turn-by-turn simulations near the half-integer resonance, for maximizing tunability and dynamic aperture of NSLS-II Booster, and for calculating limits of top-up Booster energy interlock.
BNL, Upton, Long Island, New York, USA
NSLS II storage ring RF system has the digital ramp control function, enabling rapid change of the cavity phase and amplitude. This, together with largely overcoupled RF cavity and transmitter geometry, enables the possibility to "ping" the beam in longitudinal phase space. Similar to the pinger commonly used for transverse beam dynamic studies, the RF jump presents with a powerful tool for investigation of the machine longitudinal beam dynamics. During our beam studies, RF phase was jumped within a short interval of time (less than synchrotron period). Using turn-by-turn data from BPMs we measured the machine energy acceptance with and without damping wigglers. This paper presents the beam study results.
BNL, Upton, Long Island, New York, USA
Performance, capabilities and limitations of various algorithms for linear magnet optics correction have been studied experimentally at NSLS-II. For the crosscheck, we have selected 4 algorithms based on turn-by-turn beam position analysis: weighted correction of betatron phase and amplitude, independent component analysis, model-independent analysis, and driving-terms-based linear optics characterization. A LOCO algorithm based on closed orbit measurement has been used as a reference. For the correction, either iterative solving of linear problem (matrix inversion with singular-value decomposition) or variational optimization has been used. For all the algorithms, accuracy limitations and convergence of linear lattice correction are discussed.