1 BROOKHAVEN SCIENCE ASSOCIATES Review of May 29 Excursion Bob Casey

2 BROOKHAVEN SCIENCE ASSOCIATES Injection Building Local Control Room Linac Tunnel Klystron Gallery Equipment Racks for Linac and LTB line Booster (only arc 1 installed)

3 BROOKHAVEN SCIENCE ASSOCIATES Closeup of Linac and Booster Tunnel Beam Dump 1 Equipment not installed here LB-B1 dipole LB-B2 LOTO Safety shutter LOTO Penetration fulled with lead 100 MeV beam bent too far. 1.7 R/h in localized spot on the booster wall MON Interlocked monitors did not see levels large enough to alarm or trip Monitors alarmed locally Beam Dump 2 Controlled Area

4 BROOKHAVEN SCIENCE ASSOCIATES Statement of the event While operating at 100 MeV, the power supply for the D1 bending magnet was inadvertently ramped to full power, bending the electron beam beyond the extent of the shadow shield and permitting the beam to strike the linac side wall. No radiation exposure to personnel resulted from this event. The area affected by the increased radiation levels was posted as a controlled area with radiation monitors providing local alarms.

5 BROOKHAVEN SCIENCE ASSOCIATES

6 Zoom in to the shielding Beam direction

7 BROOKHAVEN SCIENCE ASSOCIATES As seen from the top of the dipole This was the existing shield Beam went this way This is the upgraded shield

8 BROOKHAVEN SCIENCE ASSOCIATES Events of 5/29/12 Operator tuning machine with 100 MeV beam energy at 15 nC/s current while commissioning “beam loading compensation” in the linac. Legitimate but uncommon method of commissioning this mode of operation. While steering the beam to beam dump 2, a typographical error caused the dipole to ramp up to its maximum current. This combination caused the beam to bend 4 times more than designed Beam misses downstream shield wall and created radiation levels in tunnel which caused local alarms

9 BROOKHAVEN SCIENCE ASSOCIATES Events (cont.) Two electrical workers inside the tunnel but outside of the controlled area heard local alarms and went to the control room. GERT trained, wearing TLD, did not go through the controlled area. Operators responded according to procedure and informed RCD personnel. While RCD en route, operators tried to diagnose the alarm. Told workers to remain out of the tunnel. RCD verified the high alarm levels. Immediate investigation showed no dose at location of workers. RCD instructed operators to terminate the beam. Operators terminate the beam and shut off the linac until further approval. Total time ~ 45 – 50 minutes.

10 BROOKHAVEN SCIENCE ASSOCIATES Subsequent Events LCC and ESH immediately advised. It was decided to reproduce the scenario after work and obtain a more comprehensive radiation survey. With the power supply at full power, and the electron beam at 100 MeV and 15 nC/s, levels as high as 1.7 R/h in contact with wall were measured. Multibunch operation was immediately suspended until corrective actions taken.

11 BROOKHAVEN SCIENCE ASSOCIATES Area Monitor

12 BROOKHAVEN SCIENCE ASSOCIATES Radiation Levels and Dipole Current During Event

13 BROOKHAVEN SCIENCE ASSOCIATES Supplemental Shield Design Assumptions Supplemental shield was designed to prevent levels > greater than 5 mr/h in the Booster tunnel from a miss- steered 22 nC/s electron beam at 230 MeV striking the lead shield. It was not designed to intercept a 100 MeV beam when the dipole was powered to full current.