LHC Accelerator Research Program bnlfnallbnlslac Accelerator Detector Safety
LHC Accelerator Research Program bnl-fnal-lbnl-slac Accelerator & Detector Safety with LER Outline: - LER beam loss worst scenario - Proposal for distributed beam dump system - Protection of detectors and accelerator components in LER-LHC transfer line areas - Conclusions LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 1
Maximum energy deposition due to LER beam energy deposition simulations by Nikolai Mokhov LER dipole model for simulations Assumptions: (i) energy 1. 5 Te. V, (ii) intensity 3. 2 e 14 ppp, (iii) σx = σy = 0. 14 cm, (iv) beam disposal at V = 1. 2 cm, and H = 6. 5 cm Result: - Most energy deposited in the 1 st meter of magnet length with a maximum at z ~ 25 cm - Radiation peaks at z ~ 50 cm LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 2
Maximum energy deposition due to LER beam Energy deposition profile: z = 25 cm (yoke) 1. 2 e 8 m. J/g z = 50 cm (SC) 6 e 5 m. J/g Residual radiation dose profile at v = (1 -1. 4) cm Residual radiation dose profile at z = 50 cm Conclusions: 1. If full (3. 2 e 14 ppp) 1. 5 Te. V beam hits the magnet yoke some of its portions may melt. 2. For the same conditions 1/160 of beam intensity (2 e 12 ppp) is acceptable. LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 3
Distributed LER beam dumping system - Implement a beam dump system at each of 8 straight sections of LHC. - As the LER ring is 1. 35 m above the LHC one, these dumping systems will not interfere with the LHC components. - Beam is dumped horizontally into a scatter block composed of C, Al, Cu, Fe (in this order) increasing acceptable level of beam intensity to ~ e 13 ppp. - For a 1. 5 Te. V beam a kicker magnet of 1 Tm generates grazing angle of ~ 300 μrad, diluting the energy deposition density by a factor of 5 -10, or equivalent beam intensity of (1 -2) e 12 ppp beam. Top view Side view LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 4
Protection of LER magnets at IR 1 and IR 5 In the IR 1 and IR 5 sections, failure of the LER-LHC transfer line magnets may send beam anywhere between the LER and LHC ring levels. With 1/8 of beam intensity, however, the failed beam is largely contained in a 1 m long absorber. There is enough available free space between transfer line magnets to place 1 m long collimators. With the collimators, no more than 1 magnet (2 m) should be affected by a failed beam. LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 5
Protection of LHC magnets and detectors at IR 1 and IR 5 The LHC magnets at IR 1 and IR 5 are only vulnerable to the failure of the fast switching magnets. It appears that with large magnet gaps of new HD 1 a and HD 1 b dipoles the failed beams (beams enter those magnets vertically) will likely traverse through them undisturbed. The Q 1, 2, 3 triplet magnets, however, will take the hit if unprotected. So, a beam collimator must be installed between the HD 1 a and Q 1, 2, 3 magnets. LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 6
Triggering the beam dump magnets Timing limits for triggering the beam dump magnets: (i) Time needed to develop trigger signal (quench, temperature rise, or any other reason to abort beam in the arcs) ~ 0. 5 μsec. (ii) The kicker magnet supply rise time of 3 μsec (assuming the same system as in transfer lines) (iii) Time needed to pass trigger signal to the kicker magnet power supply. If 8 beam dumping systems were evenly distributed around the LER ring there would be 89 μsec / 8 = ~11 μsec time difference between them. The longest travel time for the abort signal to the kicker magnet supply is from the center of the 1/8 section of the arc: ½ x 11 μsec = 5. 5 μsec. Conclusion: About (0. 5 + 3 + 5. 5) μsec = 9 μsec is needed to begin aborting the beam. This means that up to 10% of the beam may not be aborted into the dedicated dumps in the arc magnets. However, even in the worst case such a beam would dissipate its energy into multiple arc magnets. So, placing even short collimators between these magnets (e. g. in the correctors space) would strongly suppress possible damage as such a failed beam must enter magnet core at very small grazing angles. LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 7
Summary and conclusions In the case of a catastrophically failed LER beam: 1. The LER beam with its maximum energy of 1. 5 Te. V can be sufficiently contained in collimators not exceeding 1 m of length. 2. Eight dedicated beam dumps around the LER ring will reduce maximum deposited energy density to ~ 10% of a full beam. 3. Short collimators (<0. 5 m per half-cell) in the LER arc magnets together with small grazing angles of a failed beam will likely suppress the deposited energy density to an acceptable level. 4. Multiple collimators between the LER-LHC transfer line magnets will likely minimize potential LHC and/or LER accelerator component loss in this area. 5. There is no danger to LHC detectors resulting from the LER beam failure. LER Workshop, CERN, October 11 -12, 2006 Detector Safety with LER - Henryk Piekarz 8
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