Top-Off Safety

1. Top-Off Safety Yongjun Li ASAC Meeting October 22, 2009

2. Top-off Safety Study Group • Yongjun Li (Accelerator Physicist--Tracking Analysis) • Samuel Krinsky (Accelerator Physics Group Leader) • Brett Parker (Accelerator Physicist) • Richard Heese (Injection Systems Design) • Robert Casey (ES&H) • P.K. Job (Radiation Physicist) • Sushil Sharma (Mech. Engineering Group Leader) • Dick Hseuh (Vacuum Group Leader) • Plan to add an electrical engineer for interlocks

3. Outline Methodology for top-off safety simulation NSLS-II beamlines, and their physical apertures Machine fault scenarios Magnet field profiles and parameters scan Interlock system requirement for top-off safety Conclusions

4. Methodology of Top-Off Safety Simulation • Top-off safety simulation is used to prove that implementation of fixed apertures and hardware interlocks is sufficient to prevent injected beam from escaping through the open beamline safety shutters, despite possible machine equipment faults. • We have decided to use forward tracking as developed by A. Terribilo (SLAC), because it allows us to • specify collimators to stop errant electron beam close to the ring • predict the source points of scattering shower produced by errant electron beam

5. NSLS-II Beamlines • NSLS-II beamlines can be catalogued into classes according to their source point locations: • Source points in IDs at long straight sections • Source points in IDs at short straight sections • Source points in Three Pole Wigglers (TPWs) • Source points from Bending Magnets. • Infrared beamlines

6. An Example: NSLS-II Damping Wiggler Beamline Multipole Chamber Dipole Chamber Photon stopper Safety Shutter Fixed Mask mid point of long straight 37mm 112mm 38mm bellow 75mm 23mm stick absorber 38mm crotch absorber

7. An Example of Forward Tracking Sextupole SH1 partially shorted; +5% energy deviation; scan over allowed initial phase space crotch absorber stick absorber stick absorber stick absorber vacuum chamber fixed mask photon shutter bellow blue dash line: stored beam orbit red solid line: photon beamline centre blue solid lines: collimators and vacuum chamber Damping Wiggler

8. Machine Fault Scenarios We are working to identify and classify all possible fault scenarios. Our fault classification is based on that developed at ALS • Low probability events: • Dipoles fault: • Field error limited to <5% by interlock on coil current, voltage and existence of stored beam current • Quadrupoles and sextupole fault (no interlock): • Power supply mis-setting • Whole magnet is completely or partially shorted. • Only one pole is completely or partially shorted. • High probability events: • Dipoles variation: • Trim coils +/- 3% • Quadrupoles and sextupole variation: • Vertical offset of beam trajectories, adjustment of K values and power supply ripples • Correctors: • variation from -100% to 100%. • Energy deviation: +/- 5.0% • Aperture misalignment: +/-2mm • Tracking scan considers the combination of magnet fault scenarios: one low probability event + all high probability events

9. Examples of Magnets Field Profiles B. Parker 1D transverse field profiles Normal quadrupole Quadrupole with one pole shorted 2D dipole field profiles Normal sextupole Sextupole with one pole shorted

10. Interlock Requirements (Preliminary) Only applied when injecting with safety shutters open • Beam current • Stored beam current > 25 mA • Loss rate of stored beam current is not >> than normal • Energy match • Injected beam has < 5% energy deviation from stored beam (interlock of dipoles at BTR + energy slits) • Lattice match • Storage ring dipole can’t be below 95% of design field • Based on present analysis, no quadrupoles and sextupoles need to be interlocked

11. Parameters Scan Results • We have scanned 3 typical beamlines: • Long straight line DW beamline • Short straight line ID beamline • Three Pole Wiggler beamline • Thus far our forward tracking analysis shows that with specified apertures and interlocks, these beamlines are safe for top-off injection. • In order to facilitate large scans, we are working to modify the code to enable parallel computation

12. Conclusions Forward tracking method is being applied to the analysis of NSLS-II top-off safety Possible machine fault scenarios are being determined, and included in parameter scan Preliminary specification for interlocks has been proposed and is being tested by tracking analysis Some typical beamlines have been scanned. With the specified interlocks, preliminary analysis indicates they are safe in top-off operation We will complete baseline tracking analysis in FY10 and safety analysis report for review in FY11. Hardware implementation will be ready for commissioning