1. The LHC Beam Dumping System
This talk: Design and Safety of the system
System requirements
System description, interface to other systems
Details on technical solutions chosen – effect on safety
Operational procedures – effect on safety
Expected availability of the system
Next talk: Failure scenarios and dedicated protection devices of the beam dumping system (B. Goddard)
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

2. Beam Dumping System, MPS review, 11 – 13 April 2005
System Requirements
Loss free extraction of one or both beams from the LHC onto an external absorber
Fast extraction kickers and septa
> 89 s extraction kicker flat top length: 1 LHC turn
System must be SAFE:
“Always” available
“Always” adjusted to the correct beam energy (see talk E. Carlier: ‘Safe Beam Energy Tracking’)
Abort gap without beam, for extraction kicker rise time, of 3 s
Synchronisation to abort gap from RF
Abort gap monitoring: similar system foreseen as in Berkeley (S. Hutchins)
If necessary: abort gap cleaning (see talk W. Höfle: ‘Transverse Damper’)
Dilution of the beam on absorber block
Dilution kicker magnets
Long dump lines between dilution kickers and dump block
Maximum 3 turns delay between IL generation and beam dump (this includes delay due to beam interlock system)
System must be available: not too many aborted fills due to beam dump
Safe or “Always” … see 
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

3. System Requirements: Safety of the System
Safety: always be available
No missing beam dump request
No ‘bad dumps’
Requirement on the complete Machine Protection System is SIL 3 (see introductory talk R. Schmidt)
Failure rate between 10-7/h and 10-8/h
For 4000 hours of operation per year this means Mean Time to Failure > 2500 years
The Beam Dumping system should contribute to this overall number in a balanced manner with the other elements of the MPS (BIS, BLMs etc.): it should not be the critical system
See talk R. Filippini: ‘Will the Machine Protection System let the LHC Safely Operate’
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

4. System Description Main Elements
TDE dump block
10 x MKB kickers
DILUTION
15 x MSD septa Q4
Kick enhancement
TCDS protection
TCDQ protection
15 x MKD kickers
EXTRACTION
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

5. Beam Dumping System, MPS review, 11 – 13 April 2005
Tunnel Layout
40 m
Total length of ‘dumpline’ :
975m from kicker MKD to dump block TDE
Dump cavern IP
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

6. Beam Dumping System, MPS review, 11 – 13 April 2005
Extraction of the beam
15 magnets, tape- wound C-shaped steel cores, with 15 generators (MKD): deflection in the horizontal plane
Extraction can take place with either 14 or 15 magnets
Nominal extraction angle with 15 magnets: mrad
30 % kick enhancement by standard quadrupole (Q4)
Deflection in the vertical plane by 15 septa (MSD)
System deflection angle: 2.4 mrad
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

7. Beam Dumping System, MPS review, 11 – 13 April 2005
Extraction kicker MKD
Prototype magnet
Strip-wound
Core
Conductor
Ceramic vacuum
chamber
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

8. Measured Extraction kicker Pulses: According to Design
Calibration of series magnets, ceramic chambers and generators:
Overshoot: Individual magnets < 7.5 %; System < 10 %
Rise time: Individual magnets < 2.8 s; System < 3.0 s
Pulse length: More than 90 s
MEASRUE effect of metalised ceramic chamber on absolute integrated magnetic field strength, overshoot, delay between current and magnetic field
Measurement with calibrated, fast inductive probe
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

9. Vertical Extraction Septum MSD
15 units (3 types) per beam
Laminated iron-dominated magnets
Three different families:
Different distance between apertures
Different number of coil layers
Positioned back to back for the two beam
Total of 2.4 mrad (V)
Circ. Chamber to 250ºC
One power converter per beam
Magnet coil
Extracted beam
Vacuum chamber
Circulating beam
Vacuum chamber
Laminated yoke
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

10. Beam Dumping System, MPS review, 11 – 13 April 2005
Dilution of the Beam
10 modules of dilution kickers magnets with individual generators (MKB)
Similar C-shaped steel cores as the extraction kickers MKD and similar generator technology
In vacuum tank, no ceramic chamber
System deflection each plane: ± 0.28 mrad
Sinusoidal pulse shape
4 Magnets in the horizontal plane
6 Magnets in the vertical plane
Initially only two in each plane
Limit beam current to half nominal V H
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

11. Beam Dumping System, MPS review, 11 – 13 April 2005
Beam Dump Figure
ds between consecutive bunches, 25 ns apart
Minimum velocity  10 mm/s
Dilution failures discussed in next talk
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

12. TDE Dump Block
0.7 m and 3.5 m of Graphite, 1.73 g/cm3 density
Steel cylinders under N2 overpressure.
No water cooling; forced air flow around cylinder. Monitor N2 temperature.
3.5 m of Graphite with 1.1 g/cm3 density
 0.7m  7.7 m C cylinder
1 m Al, 2 m Fe
900 T of radiation shielding blocks
Design such that no structural damage to be expected during 20 years of operation with ultimate LHC intensities
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

13. Beam Dumping System, MPS review, 11 – 13 April 2005
Beam Instrumentation
BLMs
BPM
Position Interlock BPM
Plus: – 2 BCTs per line at MKB
– 4 screens (OTR) per line at MSD, MKB, (TD), TDE
Used for System Post-Mortem
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

14. Beam Dumping System, MPS review, 11 – 13 April 2005
Functional Diagram
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

15. Safety Calculations of the System
Operational scenario
Assume 200 days/year of operation, 10 hours per run followed by post mortem, 400 fills per year
Systems includes
MKD generators, magnets, electronics, beam energy tracking (assumptions), survey system, (re-)triggering system
Not included: Septa, Q4, MKB, TDE
Failure rates
Assume constant failure rates
Calculated in accordance to the Military Handbook 217F
Others
The system may fail only when it operates
It cannot be repaired if failed unsafe  GAME OVER
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

16. Resulting Numbers
Availability over one year: False dumps distribution per year: average 2 x ( 2.6 ± 1.6 )
Unsafety per year ( 400 missions): 2 x 1.4 10-7
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

17. Gains in Safety due to Specific Design Features
Correct functioning with 14 out of 15 magnets
If no redundancy on number of extraction kickers: Unsafety number of 1.4  10-7/year becomes 0.01 year
Critical element is the extraction kicker magnet and its connectors
No online surveillance before pulsing
Assumed conservative failure rate of 2  10-7/h
Stack of solid state switches
GTO-stack failure rate 1.4  10-9/h (fail open), much better than gas tubes (thyratrons)
Triggering and re-triggering of the system
All trigger lines are doubled and ‘crossed’
Re-triggering: if a MKD switch closes it will automatically re-trigger all other MKD & MKB systems. Also adds as back-up for the normal trigger system
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

18. (Re-)Triggering Circuit
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

19. Double branch extraction kicker generator
Main capacitors in parallel
Main switches
Comp. circuit
Single branch generator would result in system unsafety of 2.4  10-6/year (instead of 1.4  10-7/year)
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

20. Safety Design Features, continued
System settings according to Beam Energy
Self-surveillance (BET), see talk E.Carlier
Redundant online monitoring of charged capacitors in the generator. Also online monitoring of the extraction septum and Q4 current with fast interlock system (supplementary to the power converter interlock).
Without surveillance of the powering system of the extraction kickers (BET system) unsafety of the beam dumping system becomes 2.2  10-3/year (instead of 1.4  10-7/year )
Even though redundancy of the number of extraction kicker system allows for the wrong powering of one extraction unit !
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

21. Operational Procedures
Beam dump system ‘post-mortem’
After every dump request the beam positions in the beam dump line and the beam dump figure will be analysed
Also comparison of total current in the ring and in the beam dump lines and beam loss monitor readings will be checked
After every dump request the redundancy of the trigger lines and double branches in the generators is verified
Only if this is correct, beam is allowed in the LHC with a system which is assumed to be ‘as good as new’
Unsafety without post-mortem would be 5.4  10-5/year (instead of 1.4  10-7/year )
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

22. Commissioning and Maintenance
After the equipment commissioning a three month ‘reliability run’ of the complete system is foreseen
Find teething problems of the system
Find bottom of ‘bath tub curve’
Confirm numbers for safety and availability
Maintenance procedures will be defined
Based on post mortem results and lifetime cycles of equipment components
UPS system included
Safe beam dump in case of power cut is designed into the system. The main energy is stored in the capacitors within the generators
Power cut scenarios will be tested during the system tests
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005

23. Beam Dumping System, MPS review, 11 – 13 April 2005
Conclusions
Safety inherent in design, due to:
Redundancy
Surveillance
System post mortem
Operational procedures
Detailed quantitave safety analysis has been made
Acceptable results
Acceptable availability numbers
Acknowledgements: The many people working on the beam dumping project.
Jan Uythoven, AB/BT
Beam Dumping System, MPS review, 11 – 13 April 2005