1. Summary of local beam screen cooling capacity and limitations for the HL-LHC (indico 668032) (v.1.1)
Daniel Berkowitz (TE-CRG)
On behalf of HL-LHC / WP9 / Heat Load Working Group
106th HiLumi WP2 Meeting
CERN, 03 October 2017

2. Outline Global cooling limitations Local cooling limitations
Sectors 2-3 / 7-8 as potentially weakest sectors
Local cooling limitations
Ensuring the beam screen refrigeration
Heat loads on the beam screens
For LHC, Run3 and HL-LHC
Conclusions
From our last meeting (indico )
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

3. Cryo-Configuration (from Run1 to Run5)
HL-LHC
Modification towards HL-LHC
ex-LEP
LHC
Refrigerators:
S1-2
S2-3
S3-4
S4-5
S5-6
S6-7
S7-8
S8-1
Period
2010
– 2012
Run 1
LHC
4 TeV
Run 2
6.5 TeV
Run 3
Ultimate
Run 4
HL-LHC
Nominal
Run 5
LHC IT
ARC+DS MS
RF400MHZ
LS1
2015
– 2018
LS2
2021
– 2023
LS3
weakest Sectors on HL-LHC
(exLEP plants taking care of triplets)
2026
– 2029
HL-LHC
LS4
RF800MHZ
2031
– 2033
D.Berkowitz for HL-LHC WP9 – Oct16 – EDMS v.1.0.
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

4. Global cooling limitation Overview of the useful margin (HL-LHC)
From 98th HiLumi WP2 Meeting, 29 June 2017
Global cooling limitation Overview of the useful margin (HL-LHC)
weakest Sectors
kW of useful margin for e-clouds + unknowns
Daniel Berkowitz (TE-CRG) - HL-LHC WP9

5. Local cooling limitation Ensuring the beam screen refrigeration
Beam-Induced heating will increase in the HL-LHC and have an impact on beam screen (BS) refrigeration
20 𝐾
6 𝐾
1.2 𝑏𝑎𝑟
3 𝑏𝑎𝑟
In general, 2 ways to solve the problem:
Counteract the heat load mechanisms → BS treatment (i.e. amorphous carbon coating)
Increase cooling capacity (unfortunately limited)
clearly preferred (medium/long term), but requires extensive studies and time.
investigated to allow a short-term solution and win extra time (LS3?) letting option a) to mature.
Local increase of cooling power could be achieved by:
Increase of 𝑇 𝑜𝑢𝑡 at BS from 20 K to 30 K
Increase of mass flow 𝑚
𝑚 limited by ∆p at
Control valve → 𝐾v
Cooling circuit itself
For LSS only!
Not treated here
Daniel Berkowitz (TE-CRG) - Heat Load Working Group
Details in study: “Increase of BS capacity at the LSS of the HL-LHC” – D.Berkowitz

6. demands more cooling capacity from the cryoplant !
The 3 Possible Actions
3 different actions are possible:
Complexity # 1 2 3
Action
None
(as it is now)
Open valves (fully)
could be done
right away
SAM ≈ 90
Semi-SAM ≈ 175
ARC cell ≈ 338
Valve opening
O%=100%
Control Valve
©Velan
Valve seat
Valve needle
Change valve seat
For SAM / Semi-SAM
KV can be increased to 0.3
(confirmed by supplier)
SAM ≈ 450
Semi-SAM ≈ 400
ARC cell ≈ 365
Control Valve
Change valve body
Requires cutting
the pipes!
SAM ≈
Semi-SAM ≈
ARC cell ≈ 375
Remarks
Valve opening
O%=80%
SAM:
KV = 0.05
Semi-SAM:
KV = 0.1
Cooling
Capacity
[W] *
SAM ≈ 62
Semi-SAM ≈ 122
ARC cell ≈ 300
demands more cooling capacity from the cryoplant !
* see appendix3 for table with cooling capacities
Daniel Berkowitz (TE-CRG) - Heat Load Working Group
Details in study: “Increase of BS capacity at the LSS of the HL-LHC” – D.Berkowitz

7. Type of data used for heat load estimations
LHC
Run3
HL-LHC
Heat-In leaks DR
scaling
Resistive heating
Synchrotron radiation
WP2
Image current
Electron clouds
Beam gas scattering
Secondary particle losses
Red corresponds to preliminary data…
Later to be repalced with values provided by WP2.
see appendix2 for scaling laws and beam parameters
Due to high uncertainties, heat loads from e-clouds are shown independently (!)
“Unknowns” are not considered
Static
Dynamic
(w/o e-clouds)
e-clouds
Beam Screen Heat Load
LHC Run3 HL-LHC
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

8. Estimated heat loads on the beam screen circuit
Example for Q5/6 R2
Valve :
The valve itself is not a limiting factor because the seat can be changed
→ However, there is a global limit on how much we can demand from the cryoplant !
80%
100%
Change Seat
HL-LHC load is significant!
5% of entire sector capacity (7.6 kW) just for Q5+Q6!
→ The use of carbon coating would „restore“ valuable capacity.
In Run3, the valve opening becomes a limiting factor. Change of valve seat is recommended at LS2.
Orange bar indicates current observations (measurements), which are higher for Q5/6 (but lower for Q4D2 strings!)
→ discrepancy with theoretical values. Why?
→ maybe unknown heat load sources?
To be investigated…
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

9. Estimated heat loads on the beam screen circuit
(see appendix3 for complete overview)
S1-2 will be warmed up.
Oportunity to test coating?
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

10. Conclusions
1. We need to take a closer look at LHC loads to understand discrepancies with theoretical values.
Or maybe are there unknown heat load sources?
2. The beam screen capillaries are not a local limitation for SAMs.
However, current valve seats become a limiting factor during Run3 and shall be exchanged.
There is no need to exchange the valves.
3. Carbon coating restores cooling capacity at K, which is especially interesting for “weaker” ex-LEP cryoplants.
Coating Q5&Q6 at Point 2/8 can restore ~350 W per sector.
Coating Q4D2 strings can restore further ~300 W per sector.
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

11. Thank you See backup slides for complementary information…
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

12. Estimated heat loads on the beam screen circuit (HL-LHC)
Appendix 1
Estimated heat loads on the beam screen circuit (HL-LHC)
Useful Margin:
LHC: ~ 5 kW (~ 65 %)
HL-LHC: ~ kW (~ 45 %)
LHC-Run2016 required the entire margin to cover for e-clouds + unknowns
e-clouds to be covered by the useful margin (!)
LHC
HL-LHC
In relative power w.r.t.
installed capacity [%]
In absolute heat power [W]
Daniel Berkowitz (TE-CRG) - HL-LHC WP9
Presented at 98th HiLumi WP2 Meeting, 29 June 2017

13. Estimated heat loads on the existing cryoplants (HL-LHC)
Appendix 1
Estimated heat loads on the existing cryoplants (HL-LHC)
Useful Margin
E-clouds are not part of the heat-load budget (!)
There is some margin available on the various circuits.
However, a “capacity transfer” is only possible to a limited extend!
Daniel Berkowitz (TE-CRG) - HL-LHC WP9
Presented at 98th HiLumi WP2 Meeting, 29 June 2017

14. Refrigeration duty of the existing plants (LHC vs HL-LHC)
Appendix 1
Refrigeration duty of the existing plants (LHC vs HL-LHC)
decrease w.r.t. LHC (removal of SRF modules)
Others, increase w.r.t. LHC
LHC
HL-LHC
Excludes photo-electron effect
Limited change in refrigeration duty for the 8 existing plants.
Daniel Berkowitz (TE-CRG) - HL-LHC WP9
Presented at CEC 2017, Madison (USA), 11 July 2017

15. Beam Parameters and Scaling Laws
Appendix 2
Beam Parameters and Scaling Laws
EDMS v0.4
Machine parameters as used for the cryo-evaluation:
Beam
Conditions
Energy
Bunch population
Bunch number
Bunch length
Luminosity *
Machine
𝐸 [TeV]
𝑁𝑏 [p+/bunch]
𝑛𝑏 [-]
4 𝜎 𝜏 [ns]
𝐿 [1034 Hz / cm2]
LHC
7.00
1.15E+11
2808
1.00
1.00**
Run 3
1.70E+11
2748
1.75**
HL-LHC
2.20E+11
1.20
5.00**
* At the high‑luminosity detectors ATLAS and CMS.
** Luminosity limited to 1.75E34 (instead of ultimate value of 2.3E34) due to installed hardware (inner-triplets).
Document name: “Scaling Factors for HL-LHC Heat Load Analyses”
Scaling laws used so far
Daniel Berkowitz (TE-CRG) - Heat Load Working Group

16. Capacity Limits Updated Values! Appendix 3
Daniel Berkowitz (TE-CRG) - Heat Load Working Group
Details in study: “Increase of BS capacity at the LSS of the HL-LHC” – D.Berkowitz

17. Capacity increase for the different magnet types
Appendix 3
Capacity increase for the different magnet types
Type
Inventory 
Length [m]
QBS
[W/m per aperture]
QBS increase (w.r.t. #0)
#1 Open valve
#2 Change seat
#3 Change body #0
Op80% #1
Op100% #2
Change seat #3
Change body
SAM Type 1
Q5 L/R1
Q5 L/R5
Q6 L/R1
Q6 L/R5
8.2
3.5
7.7
14.9
61.9
SAM Type 2
Q6 L/R4
Q4 L/R6
Q5 L/R6
6.9
4.2
9.1
17.9
80.5
D3 L/R4
11.2
2.6
5.6
10.8
38.4
Q6 L/R2
Q6 L/R3
Q6 L/R7
Q6 L/R8 12
2.4
5.2
10.0
34.6
Q5L2
Q5R2
Q5L8
Q5R8 13
2.2
4.8
9.2
30.6
Semi-SAM
Q5D4L4
D4Q5R4
16.7
3.4
7.1
11.9
20.9
Q4D2L1
D2Q4R1
Q4D2L5
D2Q4R5
19.4
2.9
6.0
16.6
Q4D2L2
Q4D2R2
Q4D2L8
Q4D2R8
22.8
2.5
5.0
13.0 IT
IT L/R1
IT L/R5 35
5.3
6.2
6.7
IT L/R2
IT L/R8 45
3.8
4.3
4.6
Arc half cell
all sectors
53.5
3.2
Increase is very
limited
LSS2 & LSS8
increase factor
Updated Values!
Details in study: “Increase of BS capacity at the LSS of the HL-LHC” – D.Berkowitz

18. Capacity requirement if change occurs all over the LSS sections
Appendix 3
Capacity requirement if change occurs all over the LSS sections
Is it feasible to increase the BS capacity at all LSS magnets? Would the Refrigerators “notice” it?
Total BS on a
LSS R/L = 77 W *
Sector = 5 kW *
77 𝑊 5 𝑘𝑊 =1.5%
Depends on the total increase of BS capacity. IR 1 2 3 4 5 6 7 8
LSS  L1 R1 L2 R2 L3 R3 L4 R4 L5 R5 L6 R6 L7 R7 L8 R8
Total [W]
Op80%
440
310 62
245
378
123
372
Op100%
618
423 91
358
527
182
514
Change seat
2061
1060
461
1395
1606
987
1516
Change body
3706
1628
830
2670
2910
2223
2424
w.r.t. 5 kW* at Sector [-]
8.8%
6.2%
1.2%
4.9%
7.6%
2.5%
7.4%
12.4%
8.5%
1.8%
7.2%
10.5%
3.6%
10.3%
41.2%
21.2%
9.2%
27.9%
32.1%
19.7%
30.3%
74.1%
32.6%
16.6%
53.4%
58.2%
44.5%
48.5%
Updated Values!
* Average capacity (magnet side only) based on „LHC Design Report“ tables 11.2; 11.6; 11.9
Details in study: “Increase of BS capacity at the LSS of the HL-LHC” – D.Berkowitz

19. Estimated heat loads on the beam screen circuit
Appendix 3
Estimated heat loads on the beam screen circuit
Preliminary
Daniel Berkowitz (TE-CRG) - Heat Load Working Group
Magnets at P1/5 are not shown for HL-LHC because those will be replaced by new hardware

20. Estimated heat loads on the beam screen circuit
Appendix 3
Estimated heat loads on the beam screen circuit
Preliminary
Daniel Berkowitz (TE-CRG) - Heat Load Working Group
Magnets at P1/5 are not shown for HL-LHC because those will be replaced by new hardware