1. TDI: to coat or not to coat?

2. LMC action (for EN-STI, helped by TE-VSC and impedance team): study the impact of partial
coating or no copper coating of the graphite jaw for the TDI spares, and bring the topic back to the LMC in time for deciding on the coating strategy of the TDI spares

3. 0.5 mm copper coating missing
Transverse impedance
more quadratic behaviour at small width, saturating again with graphite impedance
With 2 mm missing, the transverse impedance to the TDI increases by a factor 13 (60 kOhm/m).
4 mm half gap
0.5 mm copper coating missing
All in graphite
[Note: 2015 TDI with nominal hBN and Ti coating  290 kOhm/m]
All in copper

4. Transverse impedance
copper
graphite
Ti-hBN
bad coating in 2015 on TDI8 (*4 scaling)
dipolar impedance /m length
4.4
105.6
290
1160
dipolar impedance for TDI (2.8 m)
12.32
295.68
812
3248
tune shift
4.00E-06
9.60E-05
2.64E-04
1.05E-03
total tune shift V
5.10E-04
6.02E-04
7.70E-04
1.56E-03
TDI as % of total tune shift 1%
16%
34%
68%
octupole current needed
10 A?
+~20%
+~30%
+~70%
TDI was a large impedance contributor at injection
Its contribution is almost zeroed thanks to copper coating
Removing the coating is not expected to cause problems if we have margin
For HiLumi, a factor 2 increase is expected in octupole current. Is this ok?

5. Simulating the impact of missing copper coating on TDI surface
Missing line of coating on top and bottom of the beam
longitudinal impedance increases “linearly” with missing coating width and then saturates towards “only graphite impedance” after 5 to 10 mm width
With 2 mm missing, the power loss to the TDI increases by a factor 10 (13 W/m of missing coating).
power loss gets dissipated in the graphite but could heat up the neighbouring copper layer
4 mm half gap
0.5 mm copper coating missing
All in graphite
Power loss for 2748 bunches with 1.25 ns at injection
[Note: 2015 TDI with nominal hBN and Ti coating  177 W/m]
All in copper

6. Simulating the impact of missing copper coating on TDI surface
Missing line of coating on only on one side
about half of the impedance compared to both sides
power loss on the jaw with missing coating should stay the same
4 mm half gap
0.5 mm copper coating missing

7. Power loss
copper
graphite
Ti-hBN
bad coating in 2015 on TDI8 (*2 scaling)
power loss /m length
1.5 36
180
354
power loss per TDI jaw (/2*2.8)
2.1 50
250
500
Important to remember: no (or very little) cooling available on the jaw
Is the increase ok?
Needs to know if this would become eventually a problem
Needs thermal simulation from EN-STI and max allowed temperature for the TDI (TE-VSC and EN-STI) with a heat load of 50 W at injection and ~5W at top energy.
 Longitudinal stability effects to be assessed, but no showstoppers assumed for now, to be confirmed with BE-RF

8. Proposed strategy for recommendation
Is no coating OK for transverse impedance for HiLumi
 To be assessed (40% more octupoles needed)
Is no coating OK for transverse impedance now
work of Nicolo
Is no coating OK for power loss now
 Answer from STI and VSC
Is no coating OK for power loss for HiLumi
 cooling!!!
Most likely yes
Most likely yes
yes
yes NO NO
If all yes, coating is not absolutely needed
If one of the two is no, needs coating
already now

10. Was TDI8 an issue for stability in 2016?
the instability gang (Gianni, Kevin, Lee)

11. Was TDI8 an issue for stability in 2016?

12. Was TDI8 an issue for stability in 2016?
“Correlation n’est pas raison”, but with a factor 2 increase in impedance and needed octupole as compared to beam 1

13. Rum with orange juice  drunk
Vodka with orange juice  drunk
Whisky with orange juice  drunk
 orange juice makes you drunk

14. Fill 4324

15. Fill 4326 instabilities Activity when closing TDI
Chroma decrease + RF manipulations  instabilities

16. Fill 4339

17. Fill 4342

18. Fill 4355

19. Fill 4360

20. Fill 4363

21. Fill 4370

22. Fill 4379

23. Fill 4383

24. Fill 4384

25. Fill 4385

26. Fill 4386

27. Fill 4406

28. Fill 4407
TDI out

29. Fill 4412

30. Fill 4414

31. Fill 4427

32. Fill 4430

33. Fill 4436

34. From fill 4437 onwards, recommendation to inject first B2, retract TDI8, then B1 (for vacuum, stability and gain of time in case of blow up)  stable

35. Strong activity in between two injections

36. Fill 4439 Strong activity not just at injection
After this chroma back to 15/15

37. Fill 4440 -> stable, actually one of the very long fills

38. Fill 4441 (ADT tests)