The LHC Beam Dumping System u This talk

The LHC Beam Dumping System u This talk: Design and Safety of the system u u u 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 1

System Requirements u Loss free extraction of one or both beams from the LHC onto an external absorber u u u u Fast extraction kickers and septa > 89 s extraction kicker flat top length: 1 LHC turn System must be SAFE: Safe or “Always” … see u “Always” available u “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 u Synchronisation to abort gap from RF u Abort gap monitoring: similar system foreseen as in Berkeley (S. Hutchins) u If necessary: abort gap cleaning (see talk W. Höfle: ‘Transverse Damper’) Dilution of the beam on absorber block u Dilution kicker magnets u 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 Jan Uythoven, AB/BT Beam Dumping System, MPS review, 11 – 13 April 2005 2

System Requirements: Safety of the System u Safety: always be available u u u No missing beam dump request No ‘bad dumps’ Requirement on the complete Machine Protection System is SIL 3 (see introductory talk R. Schmidt) u u Failure rate between 10 -7/h and 10 -8/h u 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 u 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 3

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

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

Extraction of the beam u 15 magnets, tape- wound C-shaped steel cores, with 15 generators (MKD): deflection in the horizontal plane u u Extraction can take place with either 14 or 15 magnets Nominal extraction angle with 15 magnets: 0. 275 mrad u 30 % kick enhancement by standard quadrupole (Q 4) u Deflection in the vertical plane by 15 septa (MSD) u System deflection angle: 2. 4 mrad Jan Uythoven, AB/BT Beam Dumping System, MPS review, 11 – 13 April 2005 6

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

Measured Extraction kicker Pulses: According to Design Calibration of series magnets, ceramic chambers and generators: Overshoot: Individual magnets < 7. 5 %; System < 10 % Measurement with calibrated, fast inductive probe 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 Jan Uythoven, AB/BT Beam Dumping System, MPS review, 11 – 13 April 2005 8

Vertical Extraction Septum MSD u u u 15 units (3 types) per beam Laminated irondominated magnets Three different families: u u u 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 Jan Uythoven, AB/BT Beam Dumping System, MPS review, 11 – 13 April 2005 Magnet coil Extracted beam Vacuum chamber Circulating beam Vacuum chamber Laminated yoke 9

Dilution of the Beam u 10 modules of dilution kickers magnets with individual generators (MKB) u u 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 u 4 Magnets in the horizontal plane V u 6 Magnets in the vertical plane H u Initially only two in each plane u Limit beam current to half nominal Jan Uythoven, AB/BT Beam Dumping System, MPS review, 11 – 13 April 2005 10

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 11

TDE Dump Block 0. 7 m and 3. 5 m of Graphite, 1. 73 g/cm 3 density Steel cylinders under N 2 overpressure. 3. 5 m of Graphite with 1. 1 g/cm 3 density No water cooling; forced air flow around cylinder. Monitor N 2 temperature. 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 0. 7 m 7. 7 m C cylinder Jan Uythoven, AB/BT Beam Dumping System, MPS review, 11 – 13 April 2005 12

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

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

Safety Calculations of the System u Operational scenario u u Systems includes u u u MKD generators, magnets, electronics, beam energy tracking (assumptions), survey system, (re-)triggering system Not included: Septa, Q 4, MKB, TDE Failure rates u u u Assume 200 days/year of operation, 10 hours per run followed by post mortem, 400 fills per year Assume constant failure rates Calculated in accordance to the Military Handbook 217 F Others u u 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 15

Resulting Numbers Unsafety per year ( 400 missions): 2 x 1. 4 10 -7 Jan Uythoven, AB/BT Availability over one year: False dumps distribution per year: average 2 x ( 2. 6 ± 1. 6 ) Beam Dumping System, MPS review, 11 – 13 April 2005 16

Gains in Safety due to Specific Design Features u Correct functioning with 14 out of 15 magnets u u u Stack of solid state switches u u 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 u No online surveillance before pulsing u Assumed conservative failure rate of 2 10 -7/h GTO-stack failure rate 1. 4 10 -9/h (fail open), much better than gas tubes (thyratrons) Triggering and re-triggering of the system u u 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 17

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

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 19

Safety Design Features, continued u u System settings according to Beam Energy Self-surveillance (BET), see talk E. Carlier u u Redundant online monitoring of charged capacitors in the generator. Also online monitoring of the extraction septum and Q 4 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 ) u 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 20

Operational Procedures u Beam dump system ‘post-mortem’ u u u 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 21

Commissioning and Maintenance u After the equipment commissioning a three month ‘reliability run’ of the complete system is foreseen u u Maintenance procedures will be defined u u Find teething problems of the system Find bottom of ‘bath tub curve’ Confirm numbers for safety and availability Based on post mortem results and lifetime cycles of equipment components UPS system included u u 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 22

Conclusions u Safety inherent in design, due to: u u u Detailed quantitave safety analysis has been made u u Redundancy Surveillance System post mortem Operational procedures 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 23