Considerations for an SPL-Beamdump Thomas Otto CERN in collaboration with Elias Lebbos, Vasilis Vlachoudis (CERN) and Ekaterina Kozlova (GSI) Partly supported by the EC under Framework Programme 7 (sLHC-PP)

Beam specification PurposeBeam parameter (at E = 5GeV) Commissioning1.5 E14 protons pulse Hz 1 E20 protons over 5 months Annual Set-Up + Machine Development 2 weeks year hours week E14 protons pulse -1, 0.1 Hz 2.5 E19 protons year -1 Emergency abort1.5 E14 to 7.5 E15 protons s -1 for very short duration Thomas Otto SPL DumpSPL – ESS Workshop Lund, –

Dump Core: where the energy goes Originally developed for project X at Fermilab Layered graphite- tungsten core in a water-cooled aluminum-shell Power density (W cm -3 ) for 1.5 E13 protons s -1 Al CW air Thomas Otto SPL Dump3

Avg. Power density along beam axis (W cm -3 ) Assuming 1.5×10 14 protons/pulse and 1 pulse every 10s CORETUNGSTENIRON Thomas Otto SPL Dump4

Dump shield: containing the secondaries Tungsten shell Iron block External concrete layer Total size: L = 300 cm W = H = 200 cm W Fe Concrete Power density (W cm -3 ) for 1.5 E13 protons s -1 (different colour scale from last page)

Absorbed dose – does equipment survive ? Thomas Otto SPL DumpSPL – ESS Workshop Lund, – m upstream from dump, D ≈1 Gy h-1. Could be a problem for highly integrated electronics, semiconductor detrectors,...

And the public road ?? Dump location 17 Sv/h Dump Air Wall Earth Factor 10 m -1 7 m of earth will reduce H*(10) to 1.7  Sv h -1 Public area with low frequentation: H*(10) < 2.5  Sv h -1 required 7

Estimating activity and decay Monte-Carlo Radiation Transport + Nuclear Model Activation estimates Dose rate estimates (from decay of the radionuclides) Predictions depend critically on Quality of the nuclear model Representation of materials in the code The sensitivity of the predictions on these parameters is not always clear Take as a guideline, allow for safety factors Thomas Otto SPL Dump8SPL – ESS Workshop Lund, –

Maintenance in the tunnel Ambient dose equivalent rate H*(10) after the commissioning run (worst case) 2 m upstream from dump: H*(10) ≈ 100 mSv h -1 (1 day) ≈ 1 mSv h -1 (2 weeks) H*(10) (Sv h -1 ) After 1 day After 2 weeks Thomas Otto SPL Dump9SPL – ESS Workshop Lund, –

Tunnel wall and earth: protecting the environment Here, insertion in a 4.4 m wide tunnel 40 cm concrete wall Several metres of earth “Stars” (inelastic interactions), leading to activation of matter surrounding the dump Profile of activity concentration in earth: exponential decline 10

Soil activation Soluble radionuclides: H(100%) 22 Na (20%) Activation build-up and decay: In equilibrium: Production = Activity Conservative: equilibrium reached only after many years ! Thomas Otto SPL Dump

Conservative estimate of A eq Average proton intensity 2.5 E19 y -1 ≈ 8.13 E11 s -1 3 m “activation” layer around accelerator All activity diluted only in soil humidity (very conservative) Result for water sample: 3 H: 2.4 kBq l Na: 100 Bq l -1 Comparison with limits: Drinking water: 28 l exceed radioactivity limit Don’t source close to SPL Waste water: (ingress in tunnel) 3 H o.k. 22 Na: Factor 3 Covered by conservativism of model Thomas Otto SPL Dump12SPL – ESS Workshop Lund, –

Summary / Conclusions Dump for commissioning and set-up Dump core design “borrowed” from FNAL Absorbed dose and ambient dose rate from activation: avoid sensitive equipment a few metres upstream Critical operation: repair of dump cooling system Soil activation: Don’t source drinking water close to accelerator Water ingress (waste water o.k.) Public protected from stray radiation