The NLC is required to operate with approximately 85% uptime out of a 6500 hour running cycle. Of particular concern are global system failures, and machine damage.
Global System Failures: These are failures where a single non-redundant device failure can prevent the operation of the machine and cause downtime.
Machine Damage Failures These are failures where a single non-redundant device failure can destroy parts of the machine, resulting in significant downtime. Machine protection (MPS) is provided in 3 types of systems:
Conventional Interlocks: Shut down system operation in the event of failures of water, vacuum, and similar systems. Where possible this system will be separated to prevent an open interlock from shutting down more of the machine that is necessary
MAID: Maximum Allowable Interpulse Difference: This system checks the BPMs on each pulse and shuts down the beam before the next pulse if the orbit is out of tolerance. The entire NLC system is designed to minimize the number of devices which can change the beam orbit sufficiently to cause damage in an interpulse period.
FBA: Fast Beam Abort: This system looks at a summary interlock status from all "fast" devices and aborts the beam in the damping ring. Fast refers to devices which can significantly change the beam orbit in an interpulse period.
Reliability Recommendations: Architectural design changes are more effective in increasing reliability than component reliability improvements. Where possible the system should be designed to minimize the number of components whose failure can prevent operation of the entire machine. In particular, modularity at the Octet level would greatly increase the system reliability.
Specific System Failure Modes:
Sector RF Failure: The accelerator is designed to operate with the loss of an Octet of klystrons. Loss of an entire sector, however, will probably prevent beam operation. RF reliability document reliability.pdf (now obsolete).
Updated sector reliablility ideas document: ReliableSector.pdf, (frame maker format).
Reliability related comments on various systems:
EPICS control system: epicscomments.pdf (frame maker document)