1. 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)

2. 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

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

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

5. Constraints No precise drawings available
Material assumed to be EN GJS U 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

6. 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)

7. 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)

8. However…
In the past the dump was certainly used as much as last year or even more

9. 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: J/cm3/pulse

10. 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

11. 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
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

12. 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

13. 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

14. Steady state (MTE beam)
MTE_37kW
MTE_92kW

15. 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

16. 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

17. 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