Hall D Interlocks
Version Draft
July 3, 2000
Hall D interlocks
Prepared by the JLab Safety Systems Group
Revision Draft
July 3, 2000
Hall D Protection Systems.doc
printed 2/17/16
pp 1
Hall D Interlocks
Version Draft
July 3, 2000
Hall D Protection Systems
This document describes the hazards associated with Hall D beam operation and the
means used to mitigate the hazard. Hall D description material may be found at the
following web site:
http://dustbunny.physics.indiana.edu/HallD/
Beam Containment has three objectives:
Beam containment for personnel protection.
Beam Containment for protection of the environment.
Beam containment for equipment protection – MPS.
This analysis assumes that shielding is adequate for worst credible case beam loss.
Shielding may include fencing around potential high radiation areas.
Hazards
Prompt ionizing radiation
Powered Arc Dipoles
Limits
Prompt Ionizing Radiation – Dose and Dose rates outside shielding (as best I can
understand from conversations with Bob May)
 15 rem/hr for up to 20 minutes - worst case credible accident
 100 mrem/hr continuous inside controlled area (radcon fence)
 5 mrem/hr in uncontrolled area (outside radcon barrier) but inside site fence
 10 mrem at site fence integrated over 1 year (assume 32 weeks operation per year gives
2urem/hr)
Radiation exposure (dose per event > 5 rem) beyond DOE/Federal limits has an assumed
severity of the same level as permanent disability. This is not due to the actual risk but
rather due to the perceived risk. One lawsuit will result in >>$ 100k in expenses. NCRP
88 rates exposure of 5-25 rem as ‘high’. Our limit is 15rem in any hour (15rem/hr x 20
minutes max).
Electrical Hazards
>50 V and > 5 mA accessible conductor (OSHA definition)
Equipment limits
Diamond Radiator ?? kW beam power
Electron Beam Dump 60 kW
Photon Beam Dump ?? kW
Collimator ??kW intercepted photon flux
Hall D Protection Systems.doc
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Hall D Interlocks
Hazard
Version Draft
Source
July 3, 2000
Example Cause
Effect
Likelihood1
Risk
Code2
Administrative
Layer
Independent Protection
Layer3
Safety System
Prompt
Ionizing
Radiation
Transient4 electron beam into
photon line.
Tagger Magnet Failure.
Abrupt change in tagger current.
Hysteresis cycle while beam on.
Beam directed to Hall D.
Elevated radiation levels outside
shielding.
1/10 years
3
Tagger Software Interlocks
Permanent Magnets in beam line bend
beam down.
Tagger Supply Interlocks
PSS BCM in photon line
Tagger current compared to vertical
bend current.
Prompt
Ionizing
Radiation
Prompt
Ionizing
Radiation
Continuous5 electron beam into
photon line
Tagger Magnet Failure
1/10 years
3
Tagger Software Interlocks
Collimator missing
Human error
1/15 years
3
Pre start-up inspection.
Collimator software interlocks.
Permanent Magnets in beam line bend
beam down.
Tagger Supply Interlocks
Collimator position interlock fail-safe.
PSS BCM in photon line
Tagger current compared to vertical
bend current.
PSS CARM in counting room.
MPS beam loss monitors detect
elevated radiation at photon dump.
Prompt
Ionizing
Radiation
Collimator iron missing
Human error
Beam directed to Hall D
Elevated radiation levels outside
shielding.
Full Power light beam on photon
target.
Elevated radiation levels in counting
room.
Elevated radiation levels outside
photon dump
Elevated radiation levels outside
shielding.
1/10 years
3
Pre start-up inspection.
None
Prompt
Ionizing
Radiation
Prompt
Ionizing
Radiation
Electrocution
Collimator sweeper magnet
missing
Human error
Elevated radiation levels outside
shielding
1/10 years
3
Pre start-up inspection
Sweeper interlocks
High current beam sent to Hall D
Catastrophic beam loss
Destruction of radiator
1/10year
3
Gun/Separator set up
MPS BCM Max Current Monitor.
Electrocution
1/10 years
3
Operations Procedures
None
Prompt
Ionizing
Radiation
Transient Beam Loss in vertical
bend
RF Separator misphased
Gun laser misphased
Chopper misphased
>800 VDC wrt ground.
Magnets powered during access
Short in upper Dipole Magnet. Beam is
directed to surface. Magnet yoke a
thick target.
PSS CARM in counting room.
MPS beam loss monitors detect
elevated radiation at photon dump.
MPS Beam loss monitors.
PSS CARM in counting room.
MPS beam loss monitors detect
elevated radiation at photon dump.
PSS BCM
CARM
Elevated external radiation.
Beam Burn through
(>2.5kW)
1/10 years
3
Box Supply interlocks
Beam Position Locks
Beam loss monitor
Prompt
Ionizing
Radiation
Continuous Beam Loss in
vertical bend
Short in upper Dipole Magnet. Beam is
directed to surface. Magnet yoke a
thick target.
Elevated external radiation.
Beam Burn through
(>2.5kW)
1/10 years
3
Box Supply interlocks
Beam Position Locks
Beam loss monitor
Prompt
Ionizing
Radiation
Transient Beam Loss before
tagger
(horizontal section)
Beam misteered up
Elevated external radiation over
beamline.
1/month
3
Beam Position Locks
Operator Monitoring
Prompt
Ionizing
Radiation
Continuous Beam Loss before
tagger
(horizontal section)
Beam misteered up
1/month
3
Beam loss monitor
Operator Monitoring
Prompt
Ionizing
Radiation
Obstruction in electron vertical
bend
Bad Valve
Component left in beam line
1/5years
3
EPICS read back
Passive Shielding
Vacuum System
Berm fenced off
Beam Loss monitors at bends
Local BCM
Passive Shielding
Berm fenced off
Beam Loss monitors at bends
Local BCM
Passive Shielding
Vacuum System
Beam Loss Monitor
Local BCM
Passive Shielding
Vacuum System
Beam Loss Monitor
Local BCM
Local BCM
Exposed leads on dipole magnets
1
Likelihood after application of administrative and independent protection layers but before safety system. Likelihood is best guess based on experience with similar equipment or estimates.
Estimated per JLab EH&S manual chapter 3210.
3
Independent Protection Layer is a verifiable mitigating measure that may be under configuration control but is not a safety system.
4
‘Transient’ is an unsustainable condition. e.g. high power beam loss will eventually lead to burn through and beam shutdown.
5
‘Continuous’ is a condition sustainable for > 20 minutes, e.g. low level beam loss, operation into thick radiator.
2
Hall D Protection Systems.doc
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PSS interlock of magnets. Power
off during access.
CARM on top of berm
CARM on top of berm
CARM on top of berm
CARM on top of berm
CARM on top of berm
Hall D Interlocks
Hazard
Version Draft
Source
Example Cause
July 3, 2000
Effect
Likelihood1
Risk
Code2
Administrative
Layer
Independent Protection
Layer3
Safety System
Prompt
Ionizing
Radiation
Prompt
Ionizing
Radiation
Prompt
Ionizing
Radiation
Obstruction in electron horizontal
line
Bad Valve;
Component left in beam line
Elevated radiation level outside
shielding.
1/5years
3
Operator intervention
Passive Shielding
Local BCM
Obstruction in electron dump line
Bad Valve
Component left in beam line
Elevated radiation level outside
shielding.
1/5 years
3
Operator intervention
Dump Ion Chamber
None
Photon Beam loss in photon line
Incorrect beam position on target
1/5 years
3
Operator intervention
Beam loss monitors in front of
collimator.
CARM outside berm
Prompt
Ionizing
Radiation
Photon beam loss in collimator
Collimator misaligned
1/1 year
3
Operator intervention
Ion Chamber in photon beam line
CARM inside Counting House
CARM at end of dump
Prompt
Ionizing
Radiation
Collimator apertures misaligned
Instrumentation error
1/6 months
3
Software alarm
Collimator position interlock.
CARM inside Counting House
CARM at end of dump
Prompt
Ionizing
Radiation
Thick target in photon line
Bad valve.
Object left in beam line.
Human error
Elevated radiation levels outside
shielding.
Elevated radiation levels in counting
house.
Elevated radiation levels outside
shielding.
Elevated radiation levels in counting
house.
Elevated radiation levels outside
shielding.
Elevated radiation levels in counting
house.
Damage to collimator.
Elevated radiation levels outside
shielding
1/2 years
3
Operations/Maintenance
procedures.
EPICS read back of valve status.
Beam loss monitoring.
Valve FSD interlock
CARM outside shielding
Prompt
Ionizing
Radiation
Loss of tagger dump cooling
Stuck valve.
Catastrophic leak.
No fill after maintenance.
Destruction of dump for power > 2
kW.
Cost > $10k
1/10 years
3
Control software monitoring and
alarm.
Dump monitor chassis and alarm.
MPS interlock on dump cooling.
Prompt
Ionizing
Radiation
Prompt
Ionizing
Radiation
Equipment
Damage
Transient Beam loss in dump line
Beam misteered
Incorrect tagger magnet current
1/ month
2
Beam Position Locks
Operator monitoring
Dump ion chambers
CARM outside of berm
Continuous Beam loss in dump
line
Beam misteered
Incorrect tagger magnet current
1/2 years
2
Dump ion chambers
CARM outside of berm
Viewer IN, no limit on beam
power
Switches buggered out.
EPICS readback stuck.
Elevated external radiation levels.
Destruction of viewer.
1/5 years
2
Operator confirmation of viewer
operation.
Software heartbeat for viewer software.
CARM outside berm.
Equipment
Damage
Tune-up dump IN, no limit on
beam power
Switches buggered out.
EPICS readback stuck.
Destruction of dump.
Water damage to beam line.
1/10 years
2
Operator confirmation of dump
operation.
Software heartbeat for dump software.
None
Hall D Protection Systems.doc
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Operator monitoring
pp 4
Hall D Interlocks
Version Draft
July 3, 2000
Recommendations for interlocks:
Tagger Interlocks
4-20 mA current transducer on tagger power leads. Current must be in proper range for
interlock to clear. (PLC?)
Set point can be tied to arc energy measurement similar to BELS. (Think about
operational considerations such as either system doing hysteresis.)
Current Monitors
Beam current accounting between start of vertical bend (downstairs) and primary
radiator. Include max current monitor function to trip if current > limit.
PSS BCM in front of beam stoppers
PSS BCM in photon beam line.
Ion Chambers/BLMs
Loss monitor at primary target
Loss monitor at primary beam dump
Loss monitors in front of collimator
Loss monitors in front of photon beam dump
CARMs
CARM on top of vertical beam bend berm
CARM in counting house
CARM at rear of photon endstation (roof?)
Maybe one additional CARM between tagger and tagger dump (outside beam line)
Other considerations
Wire scanner must be linked to beam loss detection devices to avoid false trips when
scanning.
Search and secure? Operating and access modes need to be defined
Considerations for confined space
Believe that dump placement is not in the best interest of ALARA
Inhibit beam when magnets are cycling, e.g. hysteresis
Plan for insertable 2KW dump downstairs in front of PSS critical devices.
Hall D Protection Systems.doc
printed 2/17/16
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Hall D Interlocks
Version Draft
July 3, 2000
Hall D interlock devices
Beam Current Monitor
Beam Dump
Tagger Magnet
Permanent Magnet
Dipole Magnet
Magnet
Target/Detector
Magnet
Collimator Magnet
Magnet
Beam Loss Monitor
Area Radiation Monitor
Beam Stopper
Risk Assessment Table from JLab EH&S manual, section 3210.
Hall D Protection Systems.doc
printed 2/17/16
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