Diagnosing nsls-ii : a new advanced synchrotron light source *

NSLS-II, the successor to NSLS (National Synchrotron Light Source) at Brookhaven National Lab, is scheduled to be open to users worldwide by 2015 as a world-class advanced synchrotron light source because of its unique features: its half-mile-circumference (792 m) Storage Ring provides the highest beam intensity (500 mA) at medium-energy (3 GeV) with sub-nm-rad horizontal emittance (down to 0.5 nm-rad) and diffraction-limited vertical emittance at a wavelength of 1 Å (<8 pm-rad). As the eyes of NSLS-II accelerators to observe fascinating particle beams, beam diagnostics and controls systems are designed to monitor and diagnose the electron beam quality so that NSLS-II could be tuned up to reach its highest performance. The design and implementation of NSLS-II diagnostics and controls are described. Preliminary commissioning results of NSLS-II accelerators, including Linac, Booster, and Storage Ring, are presented. INTRODUCTION The construction of NSLS-II (NSLS-2) began in Mar. 2009. Three years later, preliminary Linac commissioning started in Mar. 2012. The Injector, which includes Linac, Booster and transfer-lines in between, has been successfully commissioned by Feb. 2014. The Storage Ring commissioning is on going and in good progress -50 mA stored beam was achieved in July 2014. When the whole machine is fully commissioned and tuned up, NSLS-II will be the most advanced third-generation light source in terms of the following parameters: 1) The lowest horizontal emittance at 0.5nm-rad; 2) The smallest beam size at ~3um; 3) The highest beam current (intensity) at 500mA; 4) The highest photon spectral brightness due to the lowest emittance, the smallest beam size, and the highest beam current as stated above. Figure 1: Beam Parameters Measured at NSLS-II. Machine commissioning and tuning up is all about diagnosing. To achieve the exceptional performance of NSLS-II, beam diagnostics and control systems are designed to monitor and diagnose the electron beam of NSLS-II accelerator complex. Diagnosing NSLS-II means measuring a variety of beam parameters (~10 types), including beam charge/current, filling pattern, beam position/orbit, beam size/profile, energy spread, tunes, emittance, bunch length, beam losses, etc., via a variety of beam monitors (~16 types, ~370 total device counts as shown in Table 1 below) distributed around the whole machine. Figure 1 briefly shows how the NSLS-II accelerators are diagnosed, i.e. what kind of beam parameters is measured from Linac to Storage Ring. Effective diagnosing of NSLS-II accelerator depends on the effective combinations of a variety of beam monitors, control and data acquisitions (DAQ), and high level physics applications. Figure 2 shows how beam instrumentation, controls, and physics work together to diagnose the NSLS-II machine. Figure 2: NSLS-II diagnostics and control architecture. BEAM MONITORS AND SUBSYSTEMS NSLS-II accelerators consist of one Injector and one Storage Ring (SR). According to the functionality as well as geographical distribution, the Injector is divided into 4 sub-accelerators: Linac, Linac to Booster (LtB) transfer line (including 2 beam dumps), Booster, Booster to Storage ring (BtS) transfer line (including 1 beam dump). Table 1 gives a summary of the beam monitors distributed over the whole machine. From system functionality and application point of view, the variety of beam monitors as shown in Table 1 could be classified into a few subsystems such as beam position monitor (BPM), filling pattern (Wall Current Monitor, Fast Current Transformer), beam intensity (Integrating Current Transformer, DC Current Transformer), loss control and monitoring (Beam Loss Monitor, Scraper), beam profile (Screen, Visible Light Monitor, Streak camera), tunes, etc., as shown in Figure3. ___________________________________________ *Work supported by DOE contract No: DE-AC02-98CH10886 yhu@bnl.gov MOPF20 Proceedings of IBIC2014, Monterey, CA, USA ISBN 978-3-95450-141-0 100 Co py rig ht © 20 14 CC -B Y3. 0 an d by th er es pe ct iv ea ut ho rs Overview and Commissioning Table 1: Beam Monitors at NSLS-II Linac Ltb Booster BtS SR