3 MeV H - chopper beam dump Presentation by L.Bruno 1 3 MeV H - Chopper Beam Dump Pre-design study By L.Bruno AB/ATB M.Magistris AB/OP M.Silari TIS/RP

3 MeV H - chopper beam dump Presentation by L.Bruno 2 The Pre-design study OUTLINE 1. Introduction 2. Engineering baseline proposal 3. Radiation studies 4. Engineering studies 5. Issues & future work 6. Summary

3 MeV H - chopper beam dump Presentation by L.Bruno 3 Driving Parameters … continuously intercept a 3 MeV H - beam pulsed at 50 Hz with 2.8 ms long pulses. The maximum average beam current to be absorbed is 1.1 mA, with a mean power of 3.3 kW. The beam is circular and has a uniform profile of 6 mm radius, which results in a surface heat flux of ~30 MW m -2. The chopper beam dump has to …

3 MeV H - chopper beam dump Presentation by L.Bruno 4 Beam time-structure 20 ms 2.8 ms Coarse structure Fine structure 5 bunches to the end-of-line 3 bunches to the dump Because of inertia, the fine bunch time-structure does not affect the mechanical behaviour of the dump.

3 MeV H - chopper beam dump Presentation by L.Bruno 5 Lay-out of the chopper line 135 mm flange-to- flange only ! End-of- line dump Chopper dump The dump placed after the chopper would be able to absorb also the beam at the end of the 3 MeV test facility.

3 MeV H - chopper beam dump Presentation by L.Bruno 6 Engineering baseline The dump core is shrink-fit into an actively-cooled metal jacket. The cooling tubes are bonded by plastic deformation to the jacket Front view Side view  = 10 degrees Jacket Cooling tubes Dump core Chopped beam Water Un-chopped beam Vacuum Air ~ 100 mm Water  Vacuum flange

3 MeV H - chopper beam dump Presentation by L.Bruno 7 Materials Jacket: Aluminium Dispersion strengthened copper - Cu Al 2 O 3 Core: Graphite / C-C composite Hexagonal boron nitride Aluminium nitride Molybdenum alloy (TZM) Copper Tubes: Stainless steel 316 LN Duplex st. steel (1.4462)

3 MeV H - chopper beam dump Presentation by L.Bruno 8 Elastic scattering of protons It depends on the composition of the dump core Inelastic interactions Scored with an energy threshold of 1 keV Ionization Production of X-rays, estimated with an energy threshold of 1 keV Transport of photons and electrons Simulation of the whole electromagnetic cascade; energy threshold for particle transport = 1 keV The baseline was studied to investigate: Radiation study by the Monte Carlo code FLUKA

3 MeV H - chopper beam dump Presentation by L.Bruno 9 Energy distribution Per primary 3 MeV proton ABAB Energy deposited in the dump core: A = keV +/- 0.17% B = MeV +/ %(99.3%) Energy escaping from the dump: X-Rays, e - :0.1029keV +/- 0.4% p, X-rays, e - : 14.60keV +/- 0.5% ( = 0.029% of the beam energy) Energy deposition occurs at the inner surface of the dump core. Beam spot

3 MeV H - chopper beam dump Presentation by L.Bruno 10 Induced radioactivity There is no (p,n) reaction !!! Element Coulomb barrier [MeV] (p,n) Threshold [MeV] 11 B ( 11 C ) 12 C ( 12 N ) 14 N ( 14 O) 16 O ( 16 Fe) Al3.37 The Coulomb barrier prevents the 3 MeV protons from reacting Cu5.83 Cross-check: No inelastic interactions were scored with FLUKA on C, Cu, AlN, BN and TZM.

3 MeV H - chopper beam dump Presentation by L.Bruno 11 C Al N Cu TZM Downstream of the dump, there is a flux of scattered protons. The colour plots give the fraction of the primary protons scattered per square centimeter at 6 cm distance downstream of the dump. The maximum of this flux ranges from 0.1 per mil (carbon) to 3 per mil (TZM) of the incoming protons ( p + s -1 ) Scattered proton flux Per primary 3 MeV proton

3 MeV H - chopper beam dump Presentation by L.Bruno 12 Scattered proton spectrum at 20 cm downstream of the dump The spectrum of scattered protons 20 cm downstream of the dump at 0°, 15° and 30° with respect to the beam axis peaks at 1.5 MeV. 1.5 MeV

3 MeV H - chopper beam dump Presentation by L.Bruno 13 Electron flux [cm -2 proton -1 ] 5 cm downstream of the dump, a maximum energy of ~6 keV was scored for the electrons emitted from copper. The corresponding x-ray flux (1-4 keV, 1 keV being the FLUKA lower threshold) is about cm -2 per proton. TZM C Top view

3 MeV H - chopper beam dump Presentation by L.Bruno 14 Finite Element Analysis 2D Steady-state thermal field for a 10-fold geometric dilution of the heat flux 2D Steady-state stress field cooling tubes are checked against the ASME rules (American Society of Mech. Engineers) Material choice results are shown for the most promising Copper- based configuration Opportunities to optimize water cooling parameters and structural behavior The baseline was studied to investigate:

3 MeV H - chopper beam dump Presentation by L.Bruno 15 Finite Element Models 2D STEADY-STATE THERMAL ANALYSIS Boundary Conditions: Subcooled flow boiling at 20 °C, 40 bars, 12 ms -1 with turbulence promoter. Minimum heat transfer coeff. is 54 kWm -2. Load: Heat flux of 3 MWm -2. (geometrical dilution factor of 10). 2D STEADY-STATE MECH. ANALYSIS Boundary Conditions: simple support (x-symmetry plus fixed point), GPS (Generalized Plane Strain) without bending. Load: Thermal field plus 40 bar water pressure. Cu Al 2 O 3 3 MWm -2 Duplex St.Steel Fixed point 6 Water cooling R21 Ø8.4/8 4 12

3 MeV H - chopper beam dump Presentation by L.Bruno 16 Temperature [°C] T max = 90°C Subcooled flow-boiling is effective in limiting the maximum temperature of the dump core (T max =90°C). The maximum heat flux at the inner surface of the cooling tubes is 1.13 MWm -2,which is far below the critical heat flux (>100 MWm -2 ) for the given cooling parameters.

3 MeV H - chopper beam dump Presentation by L.Bruno 17 Von Mises Stress [Pa]  VM,max =134 MPa in Cu Al 2 O 3  VM,max =142 MPa in St. Steel The maximum Von Mises stresses are below 2/3 of the yield stress at the working temperature in the dump core (177 MPa for CuAl 2 O 3 ) and below the ASME allowable S m value in the cooling tubes (207 MPa for the duplex stainless steel).

3 MeV H - chopper beam dump Presentation by L.Bruno 18 Issues and further work Dump system Cooling system Alignment Temperature / Thermal gradient Dynamic effects / Mech. strength Radiation damage Dump core Handling Dump assembly Heat removal principle Geometrical accuracy Background Vacuum / Outgassing None expectedTo be validatedUnknown Problems?...

3 MeV H - chopper beam dump Presentation by L.Bruno 19 Status in April A proposal for the engineering baseline of the chopper beam dump is available; 2.The pre-design study of its physical and mechanical behavior was performed; 3.The most promising materials have been identified; 4.The interfaces for handling, cooling, instrumentation and control are being defined. 5.A detailed technical study is to be performed next. Summary

3 MeV H - chopper beam dump Presentation by L.Bruno 20 Design guidelines The dump should be… a reliable, permanent component; easily installed, serviced and dismantled; compact, robust with possibly in-situ spares; “Cost-effective”: the same design should be re-usable within an SPL-like machine.