Absorber Introduction & Overview Jim Hylen LBNE Hadron Absorber Core Advanced Conceptual Design Review 20 January 2015
Outline • Summary of Requirements • Brief description of absorber design – Details of radiation & energy deposition are in Nikolai’s talk – Details of FEA are in Brian’s talk – Details of mechanical design/remote handling are in Vladimir’s talk • High level strategy • Beam accident assumptions & protection systems • Suitability of Aluminum as choice for the core material 2 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Requirements summary (see requirements document LBNE-doc-10148 on review web site for details) Physics requirement: • Stop leftover beam particles (absorb protons that miss the target or get scattered from it as well as hadrons, electrons, and photons generated in interactions of the primary beam with the target). Well defined end of the space where mesons decay to neutrinos. Proton beam hits target, producing shower of mesons Fraction of mesons decay to neutrinos (and muons) Hadron monitor detects charged particles (protons, mesons, muons) Absorber stops leftover protons, mesons and a fraction of the muons Monitor of muons penetrating absorber 3 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Absorber hall & support rooms RAW room Absorber to go here Decay pipe to go here Muon monitoring to go here 4 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Absorber hall layout for one level, showing support room detail (can zoom in for dimensions etc.) 5 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Need to accommodate hadron monitor, used to check beam alignment Overall absorber: Hadron monitor • Poured concrete volume: Insertion/extraction 24,000 ft 3 tower • Steel shielding: 2,500 ton • Aluminum: 39 ton 4 m diameter Decay pipe “Absorber core”: • Spoiler block • 5 Aluminum mask blocks • 9 Sculpted Al blocks • 4 Solid Al blocks • 4 Central steel blocks Beam which share the features: Water-cooled • Water cooled Hadron monitor steel core • Individually hung on Spoiler removable modules Water-cooled Al Mask blocks • Each 1 foot thick Aluminum core, 1 st 9 blocks are sculpted 6 MARS Energy Deposition & Radiological, N. Mokhov
Need to accommodate muon monitor(s), used to monitor beam stability muons are useful for monitoring neutrino beam, as they come from the same meson decays that produce the neutrinos Spaces for muon monitors after absorber, Absorber protection used by near detector group system would use a small chamber in one of these slots 7 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Operational & Radiological Requirements • Operate with minimal maintenance during the lifetime of the experiment – lifetime of Beamline Facility assumed 30 years with 20 years of actual beam operation • Support beam power up to 2.4 MW in a proton energy range from 60 to 120 GeV • Sustain beam-energy deposition under expected normal operation conditions as well as handle beam accident situations that may occur with some reasonable probability – Under Normal Operation, up to 30% of beam energy ends up in absorber – Set requirement to take 2 consecutive accident pulses of 100% beam power • Are including monitoring to limit accident to one 100% pulse • Provide radiation protection to people and ground-water – Keep below the allowable limits: • prompt radiation in beam-on accessible areas • residual radiation in areas that will be accessed for maintenance/repair • radio-activated air releases • activation of subsurface soil and groundwater • Serviceability – have the ability to replace core blocks in case of unforeseen failures 8 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Core serviceability Each core block is removable and replaceable Steel Storage of dead radio-activated equipment Al Cut-away to show gun drilled water cooling loop Images from: Vladimir Sidorov 9 Jim Hylen | Absorber Introduction & Overview 1/20/2015
State of design • The core is the most challenging part of absorber design, and is where our effort has been concentrated. Its advanced conceptual design is the focus of this review. We believe that the analysis that will be presented shows this to be a very viable design, and is ready to proceed to detailed mechanical design . • Some effort has also been directed at civil construction requirements, to allow cost estimates, and radiological issues that drive the civil construction have been seriously investigated. Some of that will be presented, although not the focus of this review. • The designs of the outer part of the absorber, the water systems, and the monitoring systems are at a conceptual level; real work on those systems will not start until after the core design passes review. They will then be subject to their own reviews after design and optimization efforts occur. • However, the concepts for the absorber protection monitoring follow fairly straightforwardly from NuMI experience, and will be shown in this talk. 10 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Conditions used as input to FEA LBNE will have two phases, 1.2 MW beam, then upgrade to 2.4 MW beam; but because of difficulty to upgrade absorber, design absorber from start for 2.4 MW There will be different configurations of targets and horns in LBNE over its lifetime, in particular: – The current baseline target/horn (using NuMI target/horn design) is financially driven; we know we can improve the beam by re-optimizing components – The current target/horn will only take 1.2 MW; we know we will re-design these components for 2.4 MW Want to leave flexibility to accommodate those future configurations. Thus we have designed to meet “worst case” scenarios: – Have assumed shortest reasonable target (two interaction lengths) • Giving worst non-interacting proton spot at absorber for normal operation – Have assumed beam can totally miss target, hitting absorber directly • Giving worst accident condition at absorber, although current baffle/target design does not allow such a severe condition – Have assumed tightest focus of beam at absorber (optics + beam-spot-at- target) for accident condition 11 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Beam parameters (see LBNE Beamline Operating Parameters LBNE-doc-10095 on review web site for details on phases and energy dependence) • If not noted, results presented for 120 GeV proton beam (worse than 60 GeV). Will also present results that show design is OK for 60 GeV proton beam. (In fact, absorber could take MUCH higher beam power at 60 GeV). • Beam parameters for various studies were picked for worst case upgrades: – 2.4 MW beam is 1.5e14 POT/spill, 1.2 second repetition at 120 GeV – Beam spot size at target is 1.7 mm RMS for 1.2 MW design, may be up to 3 mm for 2.4 MW designs; used 2.4 mm for accident study since with our optics this gives smallest spot at absorber (7 mm RMS) for beam accident condition – Baffle hole diameter: 17 mm at 1.2 MW, but may be up to 30 mm for 2.4 MW, so have used 30 mm for range of possible beam accidents – Normal operation modeled with fin-type two-interaction-length target where: • 0.3% of beam misses target entirely, giving 9 mm central spot on absorber (7 kW) • 13% of beam protons multiple scatter through target, giving 5 cm central spot on absorber (~300 kW) • The 2.4 MW target will probably include spoiler feature (described later for 1.2 MW target) and be longer, so these beam assumptions are conservative Designing to above parameters leaves significant flexibility for future configurations 12 Jim Hylen | Absorber Introduction & Overview 1/20/2015
Using experience with NuMI • LBNE core (gun-drilled water lines in aluminum blocks) based on NuMI absorber, which has been operating for a decade without any problems. • NuMI upstream decay pipe window is same material (Al 6061-T6) as absorber core, has seen same integrated proton-flux-density as LBNE absorber spoiler will, and has no problems so far. • Remote handling of core blocks based on T-block hanging system used successfully for last decade in NuMI target hall to swap horns and targets. • Beam Position Monitor (BPM) input to NuMI Beam Permit System, checking that beam is directed toward the target, has been used for last decade. • Thermocouples in absorber core watching for overheating have been an input to NuMI Beam Permit System for last decade. • Muon monitor has been used at NuMI, but not as input to Beam Permit System; some modifications/upgrades required to make this operate smoothly and reliably, and will be discussed. 13 Jim Hylen | Absorber Introduction & Overview 1/20/2015
NORMAL OPERATION 14 Jim Hylen | Absorber Introduction & Overview 1/20/2015
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