Radiation Protection Studies for the HIE ISOLDE Post-Accelerator

1. Radiation Protection Studies for the HIE ISOLDE Post-Accelerator A. Dorsival, S. Giron, Joachim Vollaire on behalf of DGS-RP

2. Outline • Introduction • Post-accelerated beams in ISOLDE today (before LS1) • Increased radiological hazards with HIE-ISOLDE • Shielding analysis for the new post-accelerator • Definition of the source term • FLUKA calculations and shielding integration • Maximum dose rate due to ion beam losses • RP monitoring • Conclusions and Perspectives HIE-ISOLDE Safety Review 05/11/2013

3. Post-accelerated beams in ISOLDE today • Current (warm) post-accelerator: • Already a source of X-ray with a max. energy of 400 keV (concrete + lead shielding) • Neutron energy ~ 3 MeV/amu below the Coulomb barrier (threshold value for nuclear reaction to occur) HIE-ISOLDE Safety Review 05/11/2013

4. Post-accelerated beams in ISOLDE today • RF interlock (captured key) prevent access during RF operation • RP measurements inside and outside the Linac Pos 1: 186 mGy/h Pos 2: 7 mGy/h Pos 3: 700 mGy/h Pos 4: 1.5 mGy/h Dose rate outside less than a few mSv/h HIE-ISOLDE Safety Review 05/11/2013

5. Increased radiological hazards with HIE-ISOLDE X-ray emitting devices { Existing { New (Radioactive) Ion beams 1 pnA = 6.25e9 ions/s Standard beam EDMS 1227549 (D. Voulot) Exceptional (emittance measurements) HIE-ISOLDE Safety Review 05/11/2013

6. Shielding for the new post-accelerator • Constraints & Challenges: • Accelerator inside the experimental hall • Consider space constraints and services necessary • define the source term !!!! • Strategy: • Review of existing facilities (Legnaro, Triumf…) • Measurements of X-ray emitted by prototype cavities • Conservative approach to extrapolate the maximum dose rate with the operation of several cavities in parallel • FLUKA calculations with a detailed layout of the shielding enclosure to identify possible weaknesses and access restrictions HIE-ISOLDE Safety Review 05/11/2013

7. Measurements of X-ray • Measurements performed on prototype cavities tested in SM18 (CERN) and IPN Orsay IPNO SM18 Dose Rate mGy/h Dose Rate mGy/h • Conclusions: • Hundreds of mGy/h during He processing • Few tens of mGy/h during normal operation 1 Gy ~ 1 Sv HIE-ISOLDE Safety Review 05/11/2013

8. Normalization for shielding calculations • Test bench in SM18 implemented as a FLUKA geometry • Starting randomly electron (900 keV = max. energy) in the ion beam plane • Normalization to the measurement results to obtain the electron emission rate Dose Rate mGy/h I0= 8 x 1013pps For 350 mGy/h at the monitor location 350 mGy/h HIE-ISOLDE Safety Review 05/11/2013

9. FLUKA calculation for the shielding • Detailed FLUKA geometry of the tunnel (penetrations, door…) • No access to the vault during RF operation (as today) • Design objective for the bulk shielding, remain below 1mSv/h due to X-ray from the cavities Penetration “chimney” (steel) Lead window Access door HIE-ISOLDE Safety Review 05/11/2013

10. Results of FLUKA calculations • Starting 600/900 keV (low/high beta) electrons using the normalization factor derived from the SM18 conditions with He processing in all cavities (pessimistic) • Normal RF operation/conditioning dose rate should be lower by more than a factor 10 Horizontal Cut at beam height – He Processing (all cavities) HIE-ISOLDE Safety Review 05/11/2013

11. Results of FLUKA calculations • Many penetrations on the roof (empty in the geometry) • Locally hundred of mSv/h on the roof during He processing • BASELINE : NO ACCESS TO THE ROOF DURING RF conditioning /He Processing and RF operation • Could be relaxed if measurements show acceptable levels HIE-ISOLDE Safety Review 05/11/2013

12. Post-Accelerator shielding status • Lateral concrete blocks have been delivered and installed • Still assessing the strategy for the up-beam shielding (1 cm of lead today) and the possibility to implement the final shielding for Phase 2 later • Repeat dose rate measurement on “production” cavities (possible safety margin) HIE-ISOLDE Safety Review 05/11/2013

13. Dose rate in case of (stable) ion beam losses Full beam loss of 1 ppA (profile) Example full beam loss of 1 ppA (dipole magnet) He 19.8 MeV/amu He 12 MeV/amu HALL ACCESSIBLE HALL ACCESSIBLE • Stable pilot (10 ppA /20 MeV/amu): • 130 mSv/h full beam loss (He) • Emittance meas. (1 pnA/11.3 MeV/amu): • 2 mSv/h full beam loss (He) Exclusion area for emittance measurements HIE-ISOLDE Safety Review 05/11/2013

14. Radiation monitoring • Replacement of ARCON monitor by RAMSES monitor launched during LS1 • Increase the monitoring of the low energy beam lines in case of RIB losses (Gamma Radiation Monitoring System GRAMS) • Monitoring specification take into account the post-accelerator operation and the high energy beam lines Conceptual specification • XRM (X-ray monitor) for pulsed x-ray • AMF (Area Mixed Field Radiation monitor) suitable for (n,g) • Local alarm units + 2 XRM above HIE-ISOLDE Safety Review 05/11/2013

15. Radiation monitoring integration 2 1 7 10 5 6 3 4 8 9 HIE-ISOLDE Safety Review 05/11/2013

16. Conclusions and perspectives • Comparison with existing facilities to determine that X-ray was the main hazard to consider for the tunnel • Effort to assess maximum dose rate for different cavity operation phases • Conservatism in the approach used : maximum energy for the e-, performances of prototype, all cavities conditioned in parallel…) • Ion beam intensity much lower than what is used in ISAC2 (TRIUMF) with the hall accessible to users • The RP monitoring has been specified accounting for X-ray monitoring and higher beam energies • Existing hazards and corresponding RP procedures will remain (contamination risks when opening the vacuum system and dose rate in case of strong gamma emitters beam loss or collection) • Future studies to assess the activation/RIB implantation for beam intercepting device (waste studies….) HIE-ISOLDE Safety Review 05/11/2013

17. Acknowledgements • A. Bernardes, R. Catherall, M. Fraser, J. Hast , Y. Kadi, S. Maridor, J. Mildenberger, I. Mondino, B. Nicquevert, D. Parchet, E. Siesling, M. Therasse, A. Trudel, G. Vandoni, W. Venturini , D. Voulot….. HIE-ISOLDE Safety Review 05/11/2013