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SLS F illing P attern F eedback (FPF) system. Charge Distribution Control in SLS Storage Ring. Why?. Camshaft Bucket. SLS Storage Ring. Provide any desired bunch pattern Which buckets to fill How much charge/current. Bunch Train. total ring length = 960 ns each RF bucket = 2 ns
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SLSFilling Pattern Feedback(FPF) system Charge Distribution Control in SLS Storage Ring Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Why? Camshaft Bucket SLS Storage Ring Provide any desired bunch pattern • Which buckets to fill • How much charge/current Bunch Train • total ring length = 960 ns • each RF bucket = 2 ns • electron bunch length ~ few tens of picoseconds Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Better charge distribution With filling pattern feedback Longer lifetime in the middle of bunch train Without filling pattern feedback Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
X-BPM positions at 4S and 6S Better beam stability Filling pattern feedback starts Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
How? • Avalanche Photo Diode (APD) after bending magnet • Sample APD reading with fast ADC • Sort readings into buckets and integrate • Calibrate and scale readout • Compare to reference pattern • Sort buckets according to charge difference • Distribute bucket list for next injections • Adjust electron gun trigger delay (linac timing) • Transfer charges from BO to SR at the right time (main timing) Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Timing events LAN Linac timing IOC C PU DLY EVR Main timing IOC E-gun trigger C PU EVG FAN 3. Synchronize bucket list C PU EVR 2. Distribute bucket list (CA) Pulsed magnets triggers Injection control IOC Filling pattern IOC C PU MOT VHQ EVR ADC 1. Sample filling pattern Avalanche Photo Diode Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Filling pattern readout Integrated bunches Sampled bunch Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Bucket list distribution problem IOC_2(linac timing) 6 3 2 7 8 1 IOC_3 (main timing) 10 25 15 33 58 90 6 3 2 7 8 1 CA Synchronization over network not reliable 10 25 15 33 58 90 IOC_1 (filling pattern) Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Bucket list synchronization IOC_3 current copy CA IOC_2 unlock_event current copy CA unlock_event unlock_event CA IOC_1 generate bucket list recv. = ? copy new current unlock_event Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008
Filling pattern control panel Ref. pattern Actual pattern Dirk Zimoch for Babak Kalantari, EPICS Collaboration Meeting October 2008