Linac4 LBE/LBS & Main Dump Conceptual Design and open issues

1. Linac4 LBE/LBS & Main Dump Conceptual Design and open issues Ivo Leitão – Linac4 BCC Meeting – 24/11/2011

2. Conceptual Design

3. Design Status Phase 1: Cylindrical core Geometry “Optimum” Pre-Design Analytical Models Pre-Design Parametric Study Materials Circular cooling pipes - water cooling Cooling Systems Phase 2: FEM Simulations Geometry Validation and Refinement of the Pre-Design Energy Deposition Final Design Design Tools Materials Radio Protection Cooling Parameters Manufacturing Constrains

4. Common Design (MD, LBE & LBS) Worst conditions (Power & Working Hours) Worst conditions (1) Before source upgrade (20 mA) (2) After source upgrade (40 mA)

5. Current Conceptual Design Cover Core UHV flange Cooling Jacket Design restrictions: (General Dimensions - mm)

6. Cooling System Turbulent Regime Optimization changing the number of ducts Flow Characteristics Helical and rectangular ducts improve heat transfer Geometric Relations (1) “Heat Exchangers”. H. Martin. Hemisphere Publishing Corporation, (1992). (2) “Fluid Friction and its Relation to Heat Transfer”. C. M. White. Transactions of the Institution of Chemical Engineers, (1932).

7. Contact Interfaces Pre-Stress with Interference of 100 µm Interference of 100 µm (diameter) between the Core (Graphite) and the Jacket (Copper) Thermal Conductance Contact Model for Interface Copper-Copper (2) Interface conditions (Pre-Stress Conditions) Interference of 100 µm (diameter) between the Core (Graphite) and the Jacket (Copper) (1) Contact Model for Interface Copper-Graphite (3) Interface conditions (Pre-Stress Conditions) (1) “Fundamentals of Machine Elements”. B. Hamrock et al. McGraw-Hill, (1999). (2) “Thermal Contact Conductance of Nominal Flat Surfaces”. H. Yuncu. Journal of Heat and Mass Transfer, (2006). (3) “Thermal Conductance Models for Joints Incorporating Enhancement Materials”. I. Savija et al. Journal of Thermophysics and Heat Transfer, (2003). (4) “An Approximate Thermal Contact Conductance Correlation”. V.W. Antonetti et al. Experimental/Numerical Heat Transfer in Combustion and Phase Change, (1991).

8. FEM Model Inputs Pre-Stress, Thermal Conductance and Energy Deposition Interface Copper-Graphite (1) Energy Deposition Fixed Support Interface Copper-Copper Cooling System (1) Thanks to AsenChristov, VasilisVlachoudis (Fluka Team)

9. Thermal Results For 100 µm of interference Temperature at the peak of energy deposition (for 300 shots) Temperature Field (ºC) (300thshot) Power extracted by the Cooling System (for 300 shots) Temperature at the surface of the cooling pipe (for 300 Shots)

10. Structural Results For 100 µm of interference Stassi Stress Ratio Distribution (300thShot) Safety Factor (1st Shot) =1.22 Safety Factor (300th shot) = 1.06 Parametric Study of Interference Fatigue? Safety Factor=1.06 Safety Factor=1.28 Contact loss

11. Conclusions (Conceptual Design) • Geometry and cooling system already defined (only few dimensions may change) • Keep going with structural analysis (include fatigue analysis) • Detailed design was started (with Design Office) • Results show that beam conditions are a bit “tight” for LBE, it is possible to increase the beam size? • Will the Slit be built? If not, the beam size could be increased? (LBS~LBE beam conditions).

12. Open Issues

13. Radiation Damage  Radiation damage is caused by the displacement of atoms from their equilibrium position  Deterioration of the material properties is usually quantified by (Dpa) Displacements per atom •  Empirical correlations to relate Dpa with change in materials properties • First Estimation of the Dpa (40mA Source): • * Dpa values are being calculated more precisely by the Fluka team (1) Thanks to AsenChristov, VasilisVlachoudis (Fluka Team)

14. Change in Physical Properties Increase in elasticity and compression strength ? Contact problems / Increase in Pre-Stress? “Neutron irradiation effects on the properties of carbon materials”. C. H. Wu et al. Journal of Nuclear Materials. (1994). “Effect of High-Energy Proton Beam Irradiation on the Behavior of Graphite Collimator Materials for LHC”. A. I. Ryazanov et al. Cern, (2010) “Neutron induced thermal properties changes in carbon fiber composites irradiated from 600 to 1000ºC”. J. P. Bonal and C. H. Wu et al. Journal of Nuclear Materials, (1996).

15. Change in Physical Properties Measurement + Commissioning + Reliability Measurement + Commissioning Main dump Measurement If Thermal Conductivity  Temperature  Stresses  Creep  Risk of failure   80-200 C˚ 500 C˚ Measurement LBE dump 400 C˚ Measurement + Commissioning Same references as in the previous slide

16. Actions / Results Possible actions (Meeting with A. Lombardi and M. Vretenar): 1) Limit the current to 20 mA during the reliability run  2) Reduce the reliability run to 6 months (Main Dump) Reduce the accumulated fluence in the center of the core 3) Enlarge the beam to 6mm x 8.8mm (rms) (Main Dump) ? 4) Steerer in front of the dump (Main Dump only) during the reliability run Case study of the Main Dump with 20mA, 6mmx8.8mm beam, with/without steerer after reliability test Temperature at the peak of energy deposition (for 150 shots) Temperature along the center (for the 150th Shot) More calculations needed (structural)

17. Conclusions (Open Issues) • Presented radiation damage study is only a estimative, but indicates possible problems in the future. • Proposed actions should be taken, but the question “Steerer or not” still remains open (more detailed study?) • Should the Main Dump be changed after reliability test and commission? Or wait until (if) it breaks? • Should the Main Dump and its spare be placed inside the shielding and a “changing” mechanism foreseen? Instead of expose technicians to high dose rates?

18. Thank you Ivo Leitão – Linac4 BCC Meeting – 24/11/2011