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1 LHC Machine Protection Rossano Giachino Acknowledgments to my colleagues of the MPWG Rossano Giachino for input and material. J.Wenninger B.Todd R.Schmidt.

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Presentation on theme: "1 LHC Machine Protection Rossano Giachino Acknowledgments to my colleagues of the MPWG Rossano Giachino for input and material. J.Wenninger B.Todd R.Schmidt."— Presentation transcript:

1 1 LHC Machine Protection Rossano Giachino Acknowledgments to my colleagues of the MPWG Rossano Giachino for input and material. J.Wenninger B.Todd R.Schmidt B. Puccio September 2007

2 Outline Energy stored in the LHC magnets LHC Dipole Magnets Power Interlock Controllers Quench Protection System Energy stored in the LHC beams LHC Beam Energy Beam Losses and Damage Potential Beam Absorbers, Beam Dump and Collimators Beam Interlock System Conclusion

3 3 Beam 1 3 Top energy/GeV Circumference/m Linac PSB CPS = 4 PSB SPS = 11 x PS LHC = 27/7 xSPS LEIR CPS SPS Booster LINACS LHC Ions protons Beam 1 Beam 2 TI8 TI2 Note the energy gain/machine of 10 to 20 – and not more ! The gain is typical for the useful range of magnets !!!

4 Sector 1 5 DC Power feed 3 Octant DC Power LHC 27 km Circumference Powering Sector: 154 dipole magnets & about 50 quadrupoles total length of 2.9 km LHC Powering in 8 Sectors Powering Subsectors: long arc cryostats triplet cryostats cryostats in matching section

5 energy ramp preparation and access beam dump injection phase coast LHC cycle: charging the magnetic energy L.Bottura 450 GeV 7 TeV start of the ramp

6 6 Outline Energy stored in the LHC magnets LHC Dipole Magnets Power Interlock Controllers Quench Protection System Energy stored in the LHC beams LHC Beam Energy Beam Losses and Damage Potential Beam Absorbers, Beam Dump and Collimators Beam Interlock System Conclusion

7 7 Energy stored in LHC magnets : where Most energy is stored in the magnetic field of the dipoles B = 8.33 Tesla I = A L = H

8 8 Energy stored in LHC magnets Energy is proportional to volume inside magnet aperture and to the square of the magnet field E dipole = 0.5 L dipole I 2 dipole Energy stored in one dipole is 7.6 MJoule For all 1232 dipoles in the LHC: 9.4 GJ

9 9 The energy stored in the magnets corresponds to.. an aircraft carrier at battle-speed of 55 km/h

10 10 The energy stored in the magnets corresponds to.. An important point to determine : How fast can this energy be released? 10 GJoule corresponds to… the energy of 1900 kg TNT the energy of 400 kg Chocolate

11 Powering Interlock Controller PLC-based Powering Interlock Controllers (PIC) are used to manage the interlock signal between the power converters and the quench protection system. The PIC also interfaces to the Beam Interlock System and will request a beam dump if the electrical circuit that fails is considered to be critical for beam operation. Powering Interlock System Quench Protection Power Converters Discharge Switches AUG UPS Cryogenics

12 12 Quench A Quench is the phase transition of a super-conducting to a normal conducting state. Quenches are initiated by an energy in the order of mJ Movement of the superconductor by several m (friction and heat dissipation) Beam losses Failure in cooling To limit the temperature increase after a quench The quench has to be detected The energy is distributed in the magnet by force-quenching the coils using quench heaters The magnet current has to be switched off within << 1 second

13 Energy extraction system in LHC tunnel Resistors absorbing the energy Switches - for switching the resistors into series with the magnets

14 14 If it does not work… P.Pugnat During magnet testing the 7 MJ stored in one magnet were released into one spot of the coil (inter-turn short)

15 Challenges for quench protection Detection of quench for all main magnets 1600 magnets in 24 electrical circuits ~800 others Detection of quench across all HTS current leads 2000 Current Leads Firing heater power supplies, about 6000 heater units Failure in protection system False quench detection: downtime of some hours Missed quench detection: damage of magnet, downtime 30 days Systems must be very reliable

16 16 Outline Energy stored in the LHC magnets LHC Dipole Magnets Power Interlock Controllers Quench Protection System Energy stored in the LHC beams LHC Beam Energy Beam Losses and Damage Potential Beam Absorbers, Beam Dump and Collimators Beam Interlock System Conclusion

17 Energy stored in the beams Stored beam energy: Proton Energy Number of Bunches Number of protons per bunch Proton Energy: 7 TeV In order to achieve very high luminosity: Number of bunches per beam: 2808 Number of protons per bunch:1.05 ×10 11 Stored energy per beam: 362 MJoule 25 ns 3×10 14 protons / beam

18 18 Stored energy comparison Increase with respect to existing accelerators : A factor 2 in magnetic field A factor 7 in beam energy A factor 200 in stored energy

19 A proton injected into the LHC will end its life… In a collision with an opposing beam proton The goal of the LHC ! On the LHC beam dump At the end of a fill, be it scheduled or not. On a collimator or on a protection device/absorber The collimators must absorb protons that wander off to large amplitudes to avoid quenches.

20 20 Beam induced damage test 25 cm Controlled experiment: Special target (sandwich of Tin, Steel, Copper plates) installed in an SPS transfer line. Impact of 450 GeV LHC beam (beam size σ x/y ~ 1 mm) Beam The effect of a high intensity beam impacting on equipment is not so easy to evaluate, in particular when you are looking for damage : heating, melting, vaporization …

21 21 Results…. A B D C ShotIntensity / p+ A1.2×10 12 B2.4×10 12 C4.8×10 12 D7.2×10 12 Melting point of Copper is reached for an impact of 2.5×10 12 p. Stainless steel is not damaged, even with 7×10 12 p. Results agree with simulation Based on those results the MPWG has adopted for the LHC a limit for safe beams with nominal 450 GeV of: protons ~ 0.3% of the total intensity Scaling the results yields a 7 TeV of: protons ~ 0.003% of the total intensity

22 22 Beam absorber The beam dump block is the ONLY element of the LHC that can safely absorb all the beam! All other absorbers in the LHC (collimators and protection devices) can only stand partial losses – typically up to a full injected beam, i.e. equivalent to the energy stored in the SPS at 450 GeV. Beam Energy Tracking Beam Dumping System DCCT Dipole Current 1 DCCT Dipole Current 2 RF turn clock

23 LHC Layout IR3, IR6 and IR7 are devoted to protection and collimation ! IR6: Beam dumping system IR4: Radio frequency acceleration IR5:CMS experiment IR1: ATLAS experiment IR8: LHC-B experiment IR2: ALICE experiment Injection IR3: Momentum Collimation (normal conducting magnets) IR7: Collimation (normal conducting magnets) Beam dump blocks

24 24 LHC Layout IR3, IR6 and IR7 are devoted to protection and collimation ! IR6: Beam dumping system IR4: Radio frequency acceleration IR5:CMS experiment IR1: ATLAS experiment IR8: LHC-B experiment IR2: ALICE experiment Injection IR3: Momentum Collimation (normal conducting magnets) IR7: Collimation (normal conducting magnets) Beam dump blocks about 8 m concrete shielding beam absorber (graphite)

25 25 Beam+/- 3 sigma 56.0 mm 1 mm +/- 6 sigma = 3.0 mm Example: Setting of collimators at 7 TeV - with luminosity optics Very tight settings orbit feedback !! Ralphs Assmanns EURO Collimators at 7 TeV, squeezed optics

26 26 Beam Interlock System and Inputs Protection for the entire machine against beam incidents. Interface to all parties involved in protection, including powering interlock systems and injectors (SPS). Microsecond reaction times.

27 27 Injection Kickers Safe LHC Parameters Beam Current Monitors Current Energy SafeBeam Flag Energy SPS Extraction Interlocks TL collimators Beam Energy Tracking Beam Dumping System DCCT Dipole Current 1 DCCT Dipole Current 2 RF turn clock LHC Beam Interlock System Access Safety System Beam Dump Trigger Timing PM Trigger BLMs aperture BPMs for Beam Dump LHC Experiments Collimators / Absorbers NC Magnet Interlocks Vacuum System RF + Damper dI/dt beam current BLMs arc BPMs for dx/dt + dy/dt dI/dt magnet current Operators Software Interlocks Screens Powering Interlock System Quench Protection Power Converters Discharge Switches AUG UPS Cryogenics essential circuits auxiliary circuits Beam Interlock System and Inputs Protection for the entire machine against beam incidents. Interface to all parties involved in protection, including powering interlock systems and injectors (SPS). Microsecond reaction times.

28 Architecture of the BEAM INTERLOCK SYSTEM Beam-1 / Beam-2 are Independent! 20 Users per BIC Half maskable Half un-maskable - fast reaction time (~ s)

29 29 Safe LHC parameters Safe Beam Flags required by Beam Interlock Controllers, to permit masking of selected interlock channels, in particular during commissioning Aperture kickers, to disable kickers when there is no safe beam Beam Presence Flags required by SPS extraction, to permit extraction of high intensity beam only when there is circulating beam in the LHC

30 30

31 31 Outline Energy stored in the LHC magnets LHC Dipole Magnets Power Interlock Controllers Quench Protection System Energy stored in the LHC beams LHC Beam Energy Beam Losses and Damage Potential Beam Absorbers, Beam Dump and Collimators Beam Interlock System Conclusion

32 32 Conclusions There is no single Machine Protection System: LHC Machine Protection relies on several systems working reliably together Safe operation of the LHC start at the SPS, via extraction into TT40/TI8 and TI2, via the transfer lines, via LHC injection etc. Safe operation of the LHC requires a culture: as soon as the magnets are powered, there is the risk of damage due to the stored magnet energy as soon as the beam intensity is above a certain value (…that is much less than 0.1% of the full 7 TeV beam), there is the risk of beam induced damage safe operation of the LHC relies not only on the various hardware systems, but also on operational procedures and on the controls system (software interlocks)

33 33 Machine protection at the LHC Machine protection activities of the LHC are coordinated by the LHC Machine Protection Working Group (MPWG), co-chaired by R. Schmidt & J. Wenninger. Since 2004 the MPWG is also coordinating machine protection at the SPS (ring & transfer lines).


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