Septum protection challenges by
LIU beams in the SPS
Matteo Marzo EN-STI-FDA
Students' coffee - 04-05-2017
Overview
• LSS4-TPSG4 and the TT40 extraction line
• LHC Injectors Upgrade (LIU) in view of the HL-LHC
• FLUKA simulations: LIU beam parameters and loss
scenarios
• Conclusions
[email protected]
2
Overview
• LSS4-TPSG4 and the TT40 extraction line
• LHC Injectors Upgrade (LIU) in view of the HL-LHC
• FLUKA simulations: LIU beam parameters and loss
scenarios
• Conclusions
[email protected]
3
LSS4 and the TT40-TI8 extraction line to LHC (1)
SPS-LSS4 418 period
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4
LSS4 and the TT40-TI8 extraction line to LHC (2)
SPS MSE septum
•
In LSS4 6 electromagnetic septa are used to extract
the beam
•
They bend the SPS proton beam, driving it towards
TT40 and TI8, to finally deliver it to the LHC
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5
LSS4 and the TT40-TI8 extraction line to LHC (3)
F
•
The septa are characterized by a constant dipolar
magnetic field able to bend and consequently extract
the beam (right hand rule)
•
As the name suggests, they allow the presence of both
circulating and extracted beams
•
Those septa have to be protected in case of beam
losses: if they are damaged, the SPS beam cannot be
properly injected in the LHC
Image courtesy of M.Fraser
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6
LSS4 and the TT40-TI8 extraction line to LHC (4)
F
•
In 2003 the TPSG4 beam diluter was firstly installed in
LSS4
•
It is used to protect the septa and prevent direct
impacts of the beam on the septa
•
It should absorbs energetic particles in case of missteering beams
TPSG4 located downstream the QFA.418
quadrupole and upstream the first septum…
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7
Overview
• LSS4-TPSG4 and the TT40 extraction line
• LHC Injectors Upgrade (LIU) in view of the HL-LHC
• FLUKA simulations: LIU beam parameters and loss
scenarios
• Conclusions
[email protected]
8
A jump to the future…the HL-LHC!
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9
LHC Injectors Upgrade (LIU)
Run1
Run2
Run3
LIU present status
L = 1.5×1034 cm-2s-1
Lint = ~70 fb-1
Run4
Run5
Run6
HL TARGET
L = 5.0×1034 cm-2s-1
Lint = ~3000 fb-1
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10
LHC Injectors Upgrade (LIU)
Run1
Run2
Run3
LIU present status
L = 1.5×1034 cm-2s-1
Lint = ~70 fb-1
Run4
Run5
Run6
HL TARGET
L = 5.0×1034 cm-2s-1
Lint = ~3000 fb-1
But… what do we mean by luminosity?!?
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11
A bit of math: how to increase the luminosity? (1)
• Nev : number of events
• R: event rate
• σev : cross-section (m2, 1b = 10-24 cm2)
• L(t) : luminosity (cm-2s-1)
•
ò L(t)dt : int. luminosity (fb-1 = 1039 cm-2)
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12
A bit of math: how to increase the luminosity? (1)
• Nev : number of events
• R: event rate
• σev : cross-section (m2, 1b = 10-24 cm2)
• L(t) : luminosity (cm-2s-1)
•
ò L(t)dt : int. luminosity (fb-1 = 1039 cm-2)
With the HL-LHC we want to maximize the (integrated) luminosity in order to
maximize total number collisions!
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13
A bit of math: how to increase the luminosity? (2)
Introducing a series of approximations (*) to express the luminosity in a closed-form expression:
Lµ
nb N b1 N b2
s s
*
x
*
y
b *e
s*=
g
• Nb1, Nb2: bunch populations for the 2 beams
• nb: number of colliding bunches at the interaction point IP(*)
• σx*, σy*: transverse beam size at the interaction point IP(*)
• β: beta function (m)
• ε : emittance (μm rad)
• γ: relativistic gamma
(*) G.Papotti,
“Luminosity and Beam-Beam at the LHC”, CAS Chevannes-de-Bogis, 10-02-2017
[email protected]
14
A bit of math: how to increase the luminosity? (2)
Introducing a series of approximations (*) to express the luminosity in a closed-form expression:
Lµ
nb N b1 N b2
s s
*
x
*
y
b *e
s*=
g
• Nb1, Nb2: bunch populations for the 2 beams
• nb: number of colliding bunches at the interaction point IP(*)
• σx*, σy*: transverse beam size at the interaction point IP(*)
• β: beta function (m)
• ε : emittance (μm rad)
• γ: relativistic gamma
In order to maximize the (integrated) luminosity we can increase the number of protons
per bunches of the colliding beams and reduce the beam size (smaller σ, that is to say
smaller emittance and/or smaller beta function- not concerning the injectors upgrade-)!
Higher number of p/b
Smaller σ
Overall higher beam density
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15
How is then the LIU project related to the HLLHC?
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16
LHC Injectors Upgrade (LIU): the SPS
“The LHC Injectors Upgrade (LIU) project has the ultimate goal of making the injectors
capable of delivering reliably the beams required by the HL-LHC” LIU Technical
Design Report – Volume I: Protons - 15 Dec 2014
Achieved
LIU target
N [1011 p/b]
1.20
2.32
ε
2.60
2.08
p [GeV/c]
450
450
Bunches
288
288
Total energy [MJ]
2.49
4.82
It’s worth noticing that:
• The increase of N implies a larger amount of energy involved in LIU (luminosity increases)
• The decrease of ε means that the beam is more focused (luminosity increases)
Are the injectors (Linac3, Linac4, LEIR, PSB, PS, SPS) in the present configuration able to
sustain potential beam losses, given the change of the beam parameters, in the LIU phase?
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17
Let’s rewind and go back to LSS4...what about
the septa we were talking about, in the LIU
phase? Are they still safe?
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18
In other words, is the TPSG4 still capable of
protecting the septa, given the new LIU beam
parameters?
The answer is obviously “NO!”
• Different solutions have been studied to protect the TPSG4 from direct impact of the
LIU beam
• The most suitable option seemed to be the installation of an additional carboncarbon absorber upstream the QFA.418
• 8 quadrupole
PRESENT
LIU
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19
Overview
• LSS4-TPSG4 and the TT40 extraction line
• LHC Injectors Upgrade (LIU) in view of the HL-LHC
• FLUKA simulations: LIU beam parameters and loss
scenarios
• Conclusions
[email protected]
20
FLUKA geometry model
The FLUKA model has been built taking into account the presence of
the TPSC4, for the LIU project
QDA
MSE.x
QFA
• TPSC4: carbon-carbon
20x20x1350 mm3
parallelepiped
• TPSG4: carbon-carbon,
Titanium, INCONEL
TPSG4
BPCE
TPSC4
MDH
LIU beam parameter
Value
N [1011 p/b]
2.32
ε
2.08
p [GeV/c]
450
Bunches
288
Total energy [MJ]
4.82
[email protected]
21
How to find the most critical impact condition?
Sensitivity analysis changing the impact
parameter and FLUKA results…
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22
Impact parameters and FLUKA trajectory check
The geometry has been built using the LineBuilder and the TPSC4, TPSG4 and the
septa are oriented according to the beam extraction
•
The FLUKA trajectory has been checked to verify that magnetic fields were
properly loaded in the FLUKA model
•
0σ, ±1σ and ±5σ impacts on the upstream end of the TPSC4, from both side, have
been simulated to see how the energy deposition on the downstream elements
changes
BPCE
•
MSE.x
TPSG4
QFA
MDH
-1σ / -5σ
TPSC4
0σ / +1σ / +5σ
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23
LIU beam, Fluka simulations: sensitivity analysis
Most heavily
loaded object
~1/3 of total energy
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24
Energy peak profile on the TPSC4 (diluter upstream
the QFA.418 quad)
TPSC Energy Deposition
4000
Peak: ~3.3kJ/cm3
3500
TPSC characteristics
0s
+1s
+5s
-1s
-5s
Dimensions: 20x20x1350 mm3
•
Material: carbon composite
•
Material density: ρ = 1.75 g/cm3
•
Specific heat: cp ~ 1.90 J/g/K @ ~1000oC
3
Energy density [J/cm ]
3000
•
2500
2000
1500
1000
500
-580
-560
-540
-520
-500
-480
-460
-440
-420
Z [cm]
Peak location, as a function of
the beam position
We simulated a 3.3 kJ/cm3 peak, corresponding to ~1300 oC.
This is well below the limit, as this material can survive
up to ~2800 oC in vacuum
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25
Dose peak profile on the QFA.418 (quadrupole)
QFA418 Beam Pipe Dose & Temperature rise
QFA418 Coil Dose
0s
+1s
+5s
-1s
-5s
100
200
0s
+1s
+5s
-1s
-5s
50
150
100
40
40
Dose [J/g]
60
Temperature Rise [oC]
Dose [J/g]
80
60
30
20
50
20
10
0
-250
-200
-150
-100
-50
0
50
100
150
0
200
0
-200
-150
-100
-50
Z [cm]
0
50
100
150
Z [cm]
QFA beam pipe characteristics
•
Material: 316LN stainless steel
•
Material density: ρ = 8.03 g/cm3
•
Specific heat: cp ~ 0.48 J/g/K
[email protected]
26
200
Dose peak profile on the QFA.418 (quadrupole)
QFA418 Beam Pipe Dose & Temperature rise
Peak of ΔT ~170
100
QFA418 Coil Dose
oC
200
0s
+1s
+5s
-1s
-5s
0s
+1s
+5s
-1s
-5s
50
150
100
40
40
Dose [J/g]
60
Temperature Rise [oC]
80
Dose [J/g]
60
30
20
50
20
10
0
-250
-200
-150
-100
-50
0
50
100
150
0
200
0
-200
-150
-100
-50
Z [cm]
QFA beam pipe characteristics
•
•
•
Material: 316LN stainless steel
•
Material density: ρ = 8.03 g/cm3
•
Specific heat: cp ~ 0.48 J/g/K
0
50
100
150
Z [cm]
Peak location
Localized energy deposition on the vacuum chamber
Worst +1s case scenario 90J/g  ~170 oC
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27
200
Dose peak profile on the QFA.418 (quadrupole)
QFA418 Beam Pipe Dose & Temperature rise
Peak of ΔT ~170
100
QFA418 Coil Dose
oC
200
0s
+1s
+5s
-1s
-5s
0s
+1s
+5s
-1s
-5s
50
150
100
40
40
Dose [J/g]
60
Temperature Rise [oC]
80
Dose [J/g]
60
30
20
50
20
0
-250
10
-200
-150
-100
-50
0
50
100
150
0
200
0
-200
-150
-100
-50
Z [cm]
0
50
100
150
Z [cm]
Peak location
The QFA.418 is a focusing quadrupole (focusing on the
horizontal plane and defocusing on the vertical plane
for positive particles, vice versa for negative ones)
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28
200
Dose peak profile on the QFA.418 (quadrupole)
QFA418 Beam Pipe Dose & Temperature rise
Peak of ΔT ~170
100
QFA418 Coil Dose
oC
0s
+1s
+5s
-1s
-5s
200
0s
+1s
+5s
-1s
-5s
50
150
100
40
40
Dose [J/g]
60
Temperature Rise [oC]
Dose [J/g]
80
60
30
20
50
20
0
-250
10
-200
-150
-100
-50
0
50
100
150
0
200
0
-200
-150
-100
-50
Z [cm]
0
50
100
150
Z [cm]
Peak spots
The peak is clearly due to low energy positive particles
defocused by the quadrupole’s magnetic field, in the
vertical plane
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29
200
Dose peak profile on the QFA.418 (quadrupole)
QFA418 Beam Pipe Dose & Temperature rise
QFA418 Coil Dose
0s
+1s
+5s
-1s
-5s
100
200
0s
+1s
+5s
-1s
-5s
50
150
100
40
40
Dose [J/g]
60
Temperature Rise [oC]
Dose [J/g]
80
60
30
20
50
20
0
-250
10
-200
-150
-100
-50
0
50
100
150
0
200
0
-200
-150
-100
-50
Z [cm]
0
50
100
150
Z [cm]
Peak spots
•
Since in the original mesh a few bins were shared
between air and stainless steel (artificial increase of
dose!), we decided to refine the binning
•
Worst +1s case scenario 65J/g  ~120 oC, it does
not pose any issue from a thermo-mechanical point of
view, even if we have high ΔT gradient in the region of
the maximum!
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30
200
Dose peak profile on the TPSG4 (diluter downstream
the QFA.418 quad)
TPSG Dose
140
0s
+1s
+5s
-1s
-5s
TPSG characteristics
Hot spot on the INCONEL
block of the TPSG4
(E=1130 J/cm3)
•
Dimensions: 25x50x3100 mm3
•
Design: 3 consecutive blocks
•
Materials: carbon composite, Ti alloy, INCONEL
(Ni-based)
80
•
Materials densities: ρcc = 1.75 g/cm3, ρTi = 4.43
g/cm3, ρIN = 8.19 g/cm3
60
•
Specific heat: cpcc ~ 1.20 J/g/K, cpTi ~ 0.52 J/g/K,
cpIN ~ 0.44 J/g/K,
120
100
TiAlV
L=30cm
Dose [J/g]
CC r=1.75 g/cm3 L=250cm
40
20
0
-200
-150
-100
-50
0
50
100
150
200
Z [cm]
•
•
•
+1s impact parameter is the most critical,
TPSG4 dose: ~140 J/g (ΔT~305 oC, still acceptable thermomechanical stresses)
Peak mainly due to protons losing a bit of energy in the TPSC4,
being over-focused by the quad and directly impacting the
TPSG4!
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31
How could we mitigate the energy peak on the
TPSG, in case of +1σ impact?
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32
Possible options
1. Titanium instead of INCONEL in the last 30cm of the TPSG4
2. 3mm cut in the downstream block of the TPSG4 (INCONEL or Titanium)
3. We move the TPSC4 ~1m upstream the first quad?
3mm
Geometry of the 3mm cut
in the TPSG4 downstream
end
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33
Dose on the TPSG4
TPSG Dose
140
120
+1s
+1s IN600 --> Ti
+1s cut Ti
+1s cut IN600
100
TiAlV
L=30cm
Dose [J/g]
CC r=1.75 g/cm3 L=250cm
80
60
40
20
0
-200
-150
-100
-50
0
50
100
150
200
Z [cm]
•
Ti Vs INCONEL: dose reduction by a factor ~1.75, but peak still present in the TPSG4
•
3mm cut in the last block of the TPSG4: dose reduction by a factor ~7, in both the
simulated cases!
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34
But…
Where did the particles which were responsible for the dose peak
in the downstream end of the TPSG4, in the +1σ configuration,
end up, after the 3mm cut?
We decided to score proton fluence downstream the TPSG4 and this
is the result ...
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35
Protons fluence
Summary:
•
Simulated particles: 5.7x106
•
Recorded upstream QDA.419: 9.9x105
•
Recorded upstream QDA.419 above 449 GeV: 9.7x105 (17.0% of the total)
Protons (20% of the total)- the ones responsible for the dose peak in the downstream end of the TPSG4follow the magnetic field in the septa, enter the quadrupole and go downstream the QDA.419 !
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36
Dose and ΔT peak profile on the MSEx
(electromagnetic septa)
MSE water channel Dose & Temperature rise
MSE other coil Dose & Temperature rise
18
100
0s
+1s
+5s
-1s
-5s
16
0s
+1s
+5s
-1s
-5s
4.5
90
4
200
80
14
3.5
8
2
6
50
1.5
30
4
1
20
2
0.5
10
0
-150
-100
-50
0
50
100
0
150
100
40
50
0
-150
Z [cm]
-100
-50
0
50
100
0
150
Z [cm]
Copper coil
Water pipes to cool
down the coil
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37
Temperature Rise [oC]
2.5
150
60
Dose [J/g]
Dose [J/g]
3
10
Temperature Rise [oC]
70
12
Dose and ΔT peak profile on the MSEx
(electromagnetic septa)
MSE water channel Dose & Temperature rise
MSE other coil Dose & Temperature rise
18
100
0s
+1s
+5s
-1s
-5s
16
0s
+1s
+5s
-1s
-5s
4.5
90
4
200
80
14
3.5
8
2
6
50
1.5
30
4
1
20
2
0.5
10
0
-150
-100
-50
0
50
100
0
150
Z [cm]
100
40
50
0
-150
-100
Copper coil
•
In the water pipes ΔT => Δp: pressures waves propagation
through the pipe!
•
Operational limit ΔpH2O < 50bar ( =>ΔT ~7°C (*))
•
Water channels FLUKA simulated ΔT is ~4°C (cpH2O=4.187
J/g/K) => below the limit! (after the 3mm cut in the TPSG4,
a decrease of ~1°C is seen in the cooling pipes)
(*) J.Borburgh, "MSE coil temperature rise with TPSC4” LIU-SPS BLPT meeting",
28-09-16
Temperature Rise [oC]
2.5
150
60
Dose [J/g]
Dose [J/g]
3
10
Temperature Rise [oC]
70
12
-50
0
50
100
0
150
Z [cm]
Water pipes to cool down the coil
A 2 jaw TPSC4 would help in protecting
the copper coil of MSEs
[email protected]
38
Dose and ΔT peak profile on the MSEx
(electromagnetic septa)
MSE water channel Dose & Temperature rise
MSE other coil Dose & Temperature rise
18
100
0s
+1s
+5s
-1s
-5s
16
0s
+1s
+5s
-1s
-5s
4.5
90
4
200
80
14
3.5
8
2
6
50
1.5
30
4
1
20
2
0.5
10
0
-150
-100
-50
0
50
100
0
150
100
40
50
0
-150
Z [cm]
-100
Copper coil
•
Longitudinal limit to thermal elongation for the coils body
ΔT < 100°C (*)
•
Vertical limit: 7÷41μm between the coil’s body and the
magnet’s yoke (*)
•
FLUKA simulated ΔT is ~170°C in the coils body:


-50
0
50
100
0
150
Z [cm]
Water pipes to cool down the coil
Mechanical stresses @ ~170°C to be quantified
What will happen to water in contact with copper @ ~170°C
(*) J.Borburgh, "MSE coil temperature rise with TPSC4” LIU-SPS BLPT meeting",
28-09-16
Temperature Rise [oC]
2.5
150
60
Dose [J/g]
Dose [J/g]
3
10
Temperature Rise [oC]
70
12
A 2 jaw TPSC4 would help in protecting
the copper coil of MSEs
[email protected]
39
Overview
• LSS4-TPSG4 and the TT40 extraction line
• LHC Injectors Upgrade (LIU) in view of the HL-LHC
• FLUKA simulations: LIU beam parameters and loss
scenarios
• Conclusions
[email protected]
40
Results of the sensitivity analyses
• The +1σ impact configuration is the most critical
• A peak of 3.3 kJ/cm3 arises in the TPSC4 (below the limit for carbon carbon)
• The QFA.418 quad gets ~1/3 of the total beam energy and a local peak of ~120°C
in the quadrupole’s vacuum pipe that doesn’t pose any issue
• The energy deposited in the TPSG4 downstream end (INCONEL) shows a peak ~140
J/g (ΔT~305 oC, acceptable thermo-mechanical stresses)
• The increase of temperature in the septa cooling pipes is ~3÷4°C (within the limits)
and for the copper coils ~170°C (still under study)
• 3mm cut in the INCONEL block to lower the dose peak in the TPSG4: dose
reduction of a factor ~7 in the TPSG4 itself and ΔT decrease of ~1°C in the MSE’s
cooling pipes… but 20% of protons are lost downstream the QDA.419
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41
Many thanks!