1. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz1 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

2. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz2 Maximum energy deposition due to LER beam Assumptions: (i) energy 1.5 TeV, (ii) intensity 3.2 e14 ppp, (iii) σ x = σ y = 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 dipole model for simulations LER beam energy deposition simulations by Nikolai Mokhov

3. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz3 Maximum energy deposition due to LER beam Energy deposition profile: z = 25 cm (yoke) 1.2 e8 mJ/g z = 50 cm (SC) 6 e5 mJ/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 e14 ppp) 1.5 TeV beam hits the magnet yoke some of its portions may melt. 2. For the same conditions 1/160 of beam intensity (2 e12 ppp) is acceptable.

4. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz4 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 TeV 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) e12 ppp beam. Top view Side view

5. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz5 Protection of LER magnets at IR1 and IR5 In the IR1 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 1m 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 (2m) should be affected by a failed beam.

6. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz6 Protection of LHC magnets and detectors at IR1 and IR5 The LHC magnets at IR1 and IR5 are only vulnerable to the failure of the fast switching magnets. It appears that with large magnet gaps of new HD1a and HD1b dipoles the failed beams (beams enter those magnets vertically) will likely traverse through them undisturbed. The Q1,2,3 triplet magnets, however, will take the hit if unprotected. So, a beam collimator must be installed between the HD1a and Q1,2,3 magnets.

7. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz7 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.

8. LER Workshop, CERN, October 11-12, 2006Detector Safety with LER - Henryk Piekarz8 Summary and conclusions In the case of a catastrophically failed LER beam: 1. The LER beam with its maximum energy of 1.5 TeV 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.