Kiman Ha

Techniques for transparent lattice measurement and correction

A novel method has been successfully demonstrated at NSLS-II to characterize the lattice parameters with gated BPM turn-by-turn (TbT) capability. This method can be used at high current operation. Conventional lattice characterization and tuning are carried out at low current in dedicated machine studies which include beam-based measurement/correction of orbit, tune, dispersion, betabeat, phase advance, coupling etc. At the NSLS-II storage ring, we observed lattice drifting during beam accumulation in user operation. Coupling and lifetime change while insertion device (ID) gaps are moved. With the new method, dynamical lattice correction is possible to achieve reliable and productive operations. A bunchby-bunch feedback system excites a small fraction (~1%) of bunches and gated BPMs are aligned to see those bunch motions. The gated TbT position data are used to characterize the lattice hence correction can be applied. As there are ~1% of total charges disturbed for a short period of time (several ms), this method is transparent to general user operation. We demonstrated the effectiveness of these tools during high current user operation.

Beam position monitor gate functionality implementation and applications

Graphical abstract

Fast glitch detection of coupled bunch instabilities and orbit motions

During high current operation at NSLS-II storage ring, vertical beam size spikes have been noticed. The spikes are believed due to ion instability associates with vacuum activities localized in the ring. A new tool has been developed using gated BPM turn-by-turn (TBT) data to detect beam centroid glitches. When one turn orbit deviates outside the predefined window, a global event will be generated. This allows synchronized data acquisition of TBT beam positions around the ring. Bunch by bunch data is acquired at the same time to analyze the possible coupled bunch instabilities (CBI). Besides CBI mainly due to ion bursts, fast orbit glitches have been captured with the new tool. Sources of the glitches can be identified.

Upgrade of NSLS-II Active Interlock System

The NSLS-II Storage Ring is protected from possible damage from synchrotron radiation by a dedicated active interlock system (AIS). The AIS monitors electron beam position and angle and triggers beam drop if beam orbit exceeds the boundaries of pre-calculated active interlock envelope. The one year worth of the AIS operation showed that there is a number of erroneous machine trips associated with the AIS. In this paper we describe an upgrade of the AIS that allowed us to get rid of the Storage Ring faults and improved the overall NSLS-II reliability.

NSLS-II Active Interlock System and Post-Mortem Architecture

The NSLS-II at Brookhaven National Laboratory (BNL) started the user beam service in early 2015, and is currently operating 13 of the insertion device (ID) and beamlines as well as constructing new beamlines. The fast machine protection consists of an active interlock system (AIS), beam position monitor (BPM), cell controller (CCs) and front-end (FE) systems. The AIS measures the electron beam envelop and the dumps the beam by turning off RF system, and then the diagnostic system provides the post-mortem data for an analysis of which system caused the beam dump and the machine status analysis. NSLS-II post-mortem system involves AIS, CCs, BPMs, radio frequency system (RFs), power supply systems (PSs) as well as the timing system. This paper describes the AIS architecture and PM performance for NSLS-II safe operations. INTRODUCTION NSLS-II storage ring (SR) completed commissioning in 2014 [1-2], and started operation and user beam service in 2015. In 2016, up to 16 insertion devices were installed as well as the user service with two superconducting RF cavity and 250 mA stored beam current. The active interlock system is one of the major machine protection systems from the synchrotron radiation. The main purpose of AIS is to protect the insertion device vacuum chamber and the storage ring vacuum chamber from missteered synchrotron radiations from IDs and Dipole magnets radiation. The required active interlock insertion device (AI-ID) system response time is maximum < 1 ms, because through 1 ms duration damping wiggler (DW) aluminum vacuum chamber will increase the surface temperature to 100 C at 1.5 mrad vertical angles. For the storage ring bending magnet protection, which is called the active interlock bending magnet (AI-BM), the response time is 10 ms. Allowance envelop defined for protecting the device and configured offset is xy=+/-0.5 mm, and the angle is xy=+/0.25 mrad. This paper will present the AIS hardware configuration, FPGA internal functions, global PM hardware configuration and internal timing diagrams. NSLS-II operation status and the future plan. SYSTEM DESCRIPTION NSLS-II AIS showed robust and stable performance during operation, and lots of flexibilities for implementing machine protection from the synchrotron radiation and critical machine faults. One of the benefits is the real-time offset/angle calculation, and all of the decision engines are located at the central FPGA core, which is called C31. The AIS hardware layout is shown in Fig 1, and more details of the system and each device regarding characteristics and functions are described in [1-2]. AI Database And Web interface softIO C1 softIO C2 AI FPGA Interfa ce RF Transmitter and LLRF C OPI-CSS PM Client DISK Storage EPS RF Transmitter and LLRF D Input signals from machine Ethernet cable (1 Gbps) Wire (TTL) SDI fiber network (5 Gbps) Cell 1 Cell 30 SDI CW SDI CCW Timing