| Experiments Protection during
the LHC operation |
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INJECTION MAGNETS FAILURES
Definition: the beam is injected onto a wrong
trajectory due to the failure of the injection magnets.
Consequences on the experimental detectors:
Action (interlocks):
- TDI must be in place and TDI interlock not masked for
safe beam
- SIS interlock on the TL (Transfer Line) trajectory.
(Easy to implement, but can be tricky to analyze reliably)
- HW interlock on the TL PC currents must not be masked
for safe beam
WRONG SETTINGS AT INJECTION
Definition: Magnets can be wrongly set. Dipoles and
orbit correctors located in the Experimental Insertions could be
dangerous for the experiments.
Consequences on the experimental detectors:
The consequences for the ATLAS detector can
be found on the two presentations below which are based on
the note of Dariusz Bocian
"Accidental Beam Losses during Injection in the Interaction
Region IR1", LHC Project Note 335, 2004
Issues:
- Definition of Safe Beam for the experimental detectors
- Detection of Safe Beam lost in the experimental area
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CIRCULATING BEAM at 450 GeV |
ERRONEOUS INJECTION
DURING 450 GEV COLLISIONS
Definition: erroneous injection
during 450 GeV collisions. This is only possible at 450 GeV
since the MKI interlock on energy does not work. However, if
the TDI is out (standard during collisions), a maskable HW
interlock is set at the level of the injection BIC. Does not
provide full protection against an injection since it can be
masked for safe SPS beams.
Consequences on the experimental
detectors: to be computed if necessary
Action (interlocks):
1. SIS
interlock on TI2/8 TED (Transfer Line Dump) position
(require TED IN [takes > 1 minute to move]) during
stable beams. Easy to implement.
2. SIS interlock on MKI state (require OFF) during
stable beams. Easy to implement.
3. SIS interlock on end of line PCs (require OFF) during
stable beams. Easy to implement.
4. SIS interlock to prevent masking TL HW interlocks
during stable beams. Relatively easy to implement.
LOCAL BUMPS
Definition:
local bumps could be created in the experimental
insertion with the available strength of the orbit
correctors and hit the detectors located very close to the
beam.
Consequences on the experimental
detectors:
LHCb: At 450 GeV you can bump the beam into VELO
when in closed position (5 mm from beam) with a closed
bump.
Action (interlocks):
SIS
interlock on corrector settings CHANGES: at begin of
stable beams, record corrector settings by SIS.
Interlock if any change larger than say 5-10 microrad
occurs during stable beams. Relatively easy to
implement.
POWERING FAILURES
Definition:
failure of the powering system during collisions.
Consequences on the experimental
detectors:
LHCb: consequences on VELO of the Q5 and D1
failure can be found in Andres Gomez Alonso
talk.
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CIRCULATING BEAM at 7 TeV |
LOCAL BUMPS
Definition:
local bumps could be created in the experimental
insertion with the available strength of the orbit
correctors and hit the detectors located very close to the
beam.
Consequences on the experimental
detectors:
Action (interlocks):
POWERING FAILURES
Definition:
failure of the powering system during collisions.
Consequences on the experimental
detectors:
Definition:
failure of the dump system (unsynchronized beam abort)
Consequences on the experimental detectors:
CMS: consequences on the CMS detector
can be found in Mika Huhtinen
talk.
Action (absorbers, TCDQ & TCDS):
"Protecting LHC Components Against Radiation Resulting From
an Unsynchronized Beam Abort ", LHC Project Report 478,
April 2001
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