Thermo-mechanical analysis of the D3 dump in the TT2 line (PS) A. Pilan Zanoni (EN-STI-TCD) M. Calviani, E. Grenier-Boley (EN-STI-TCD) J. A. Briz Monago, V. Vlachoudis (EN-STI-FDA)

1.Introduction The D3 dump is located at the end of the TT2 transfer line It is currently the PS external beam dump No history on the design is available and no technical drawings of the dump has been found up to now It has been installed in the ~80s and – to our knowledge – never touched since

Location / Geometry Drawing: SPSLTT100001 Towards n_TOF (FTN) Towards SPS (TT10) Drawing: SPSLTT100001

Location / Geometry TT2 line According to EDMS 341746: 7.2m thick cast iron dump Dump D3 Dimensions scaled from drawing

Constraints No precise drawings available Material assumed to be EN GJS 400 18U RT (EN-JS1059) : ductile cast iron (spheroidal graphite). The same as for iron shielding blocks used around the accelerator complex Dump is made of blocks whose size is not well known either. We assume 1600x400x400mm3 as for EDMS 1307583

2. Beam parameters Beam types operated in the PS Energy (GeV/c) Intensity (x1010) Intensity LIU (x1010) Pulse length (Trev) Repetition Beam size (mm2) TOF 20 800 1000 1/8 1.2s 4.7x3.4 MTE 14 2000 5000 5 2.1x2.9** LHC 26 900 72/84 3.6s 1.2x1.4 AD 1400 4/20 2.4s 3.8x2.8 *Trev: revolution time in the storage ring. For PS 1Trev = 2.1μs **Beam size after LIU: σx=4mm, σy=5mm - MTE (multi turn extraction)

MTE beam shot to the dump in 2016 Recent high load on D3 Measurement of the intensity of the current MTE beam (in 1010ppp) over 5 hours in the D3 dump on August 3rd, 2016 between 08:34 and 14:00 (shielding test above the route Goward)

However… In the past the dump was certainly used as much as last year or even more http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1590452)

Beam configuration Assumed based on the current MTE beam (worst case) Beam operation is only MD-related 14 GeV/c, beam size 2.0x2.0mm, 2*1013 ppp over 5 hours Pulse length: 10.5 μs / repetition rate: 1.2 seconds shown for: Intensity: 2e13 ppp Peak energy deposition: 285.8 J/cm3/pulse

Beam operation remarks 1 each 3 pulses of the MTE beam is not fired Therefore we consider the following scenarios: MTE_24kW: Interrupted beam (2 pulses out of 3) MTE_37kW: Repeated beams (3 pulses out of 3 continuously) Scenarios Intensity Total power absorbed by the dump Peak energy MTE_24kW 2*1013 ppp 24.4 kW 285.8 J/cm3/pulse MTE_37kW 36.6 kW MTE_61kW 5*1013 ppp 61.1 kW 200.0 J/cm3/pulse MTE_92kW 91.6 kW

3. Geometric model ℎ c =𝑘 𝜎 𝑚 𝑝 𝐻 0.985 Thermal Conductance is evaluated from the Mikic-Yovanovic theory: ℎ c =𝑘 𝜎 𝑚 𝑝 𝐻 0.985 k – equivalent heat conductivity, σ – surface roughness, m - surface slope (rad), p – contact pressure, H – material hardness hc=0 W/m2K* hc=499 W/m2K Tair=22oC ε = 0.5 hc=0 W/m2K* hc=988 W/m2K *contact pressure p=0 Pa hc=1473 W/m2K hground=81.2 W/m2K Tground=22oC beam 3D model for thermal conductance and steady-state analyses (symmetric in XZ plane) Remark: the contact may be irregular (voids), reducing hc

4. Results (1 hour transient thermal) *properties as for T=600oC 1330oC* 1370oC* 888oC* 940oC* 524oC 571oC 348oC 400oC Average peak temperature over 1 hour Peak temperature for the last pulses Pre-LIU conditions Potential post-LIU conditions Melting point (cast iron): T=1153oC

4. Results (5 hours transient thermal) *properties as for T=600oC 1619oC* 1660oC* 1088oC* 1140oC* 643oC* 685oC* 425oC 476oC Average peak temperature over 5 hours Peak temperature for the last pulses Pre-LIU conditions Potential post-LIU conditions Melting point (cast iron): T=1153oC

Steady state (MTE beam) MTE_37kW MTE_92kW

Steady state (LHC beam) Theoretical sensitivity analysis LHC_BCMS (0.58e13 ppp, 8.5 kW) σx=1.2 mm, σy=1.4 mm 26 GeV/c 2.4s beam repetition rate HL_LHC (2.3e13 ppp, 33.7 kW) σx=1.2 mm, σy=1.4 mm 26 GeV/c 2.4s beam repetition rate

Thermal results Structural results Possible beams after LIU upgrade (5e13 ppp, 61-92kW) induces temperatures near or even higher than the melting point up to 1-5 hours of operation. Structural results Long exposure to high temperatures badly weakens the material from 425oC onwards (figure on the right) Dump under plastic deformation. Ultimate tensile strength is not reached after 5 hours for: MTE_24kW: max σeqv/σtensile = 0.77, max σeqv=193 MPa MTE_37kW: max σeqv/σtensile = 0.89, max σeqv=223 MPa Stress-rupture properties of ferritic ductile irons From: ASM Specialty Handbook: Cast Irons

5. Conclusion A note – summarizing the results – will be written D3 dump is heavily used during MDs – during physics run the average power on the dump is relatively low Current operation of the D3 dump (MTE, 2*1013 ppp) during special MDs with only 1 MTE/supercycle (or worse) will lead to increasingly local plastic deformation over time. Possible measures to contain that: Reduce the intensity or the time of beam radiation to the dump Give some time for passive cooling between supercycles Keep repeated MTE beam at 2 out of 3 pulses Validation of the thermal model will be cross-checked by measurements of the temperature on the surface of the cast iron block during 2017 run. If the current D3 dump is used the same way (i.e. without any limits during MDs) after the LIU upgrade: Operation beyond the melting point in the dump core Long time exposure to high temperatures strongly weakens the dump material (plastic flow, deformation, etc.) – under investigation potential impact on the dump structure A note – summarizing the results – will be written NB: it is highly likely that plastification or melting already occurred during past operation in the 90s