FLUKA simulations of UFO-induced lossesin the LHC arc
A. Lechner and F. Cerutti (on behalf of the FLUKA team)with valuable input by T. Baer
Meeting of the Quench Test Strategy WG
May 4th, 2012
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 1 / 14
Introduction
Introduction
Considered region: arc cell 19R3Outline
◦ BLM pattern for different potential UFOlocations around the MBs
◦ Comparison of simulation results againstBLM data measured in 2011 (with only 6BLMs present around the MQ)
◦ Demonstration of the resolution gain dueto additional BLMs installed in 2012: firstcomparison of simulations withmeasurements
◦ Peak energy density in MB coils for 3.5 TeVand 7 TeV
General BLM coverage of arc cells: 6 BLMs in proximity of each MQ
MQ MSCB
Beam 1
Beam 2
MB MB
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 2 / 14
Introduction
Introduction
19R3: cell with one of the highest UFO occurrence in 2011
Figure: BLM loss pattern caused by UFO@19R3 (15/10/2011)
Cell Beam # UFOs25R3 2 14419R3 1 12628R7 2 11826L3 1 7328L6 2 72
Table and figure by courtesy of Tobias.
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 3 / 14
Simulation setup
FLUKA geometry implementation of the LHC arc
MB.A19R3
MQ.19R3MB.C19R3
MB.B19R3
MQ.19R3
MQT.19R3
MCS.A19R3
fedb: FLUKA element database (magnets, interconnects, ...)
LineBuilder: tool to build FLUKA accelerator lines
(credits: A. Mereghetti , R. Versaci,V. Boccone, F. Cerutti, V. Vlachoudis, A. Lechner, ...)
MCS.C19R3
BLM
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 4 / 14
Simulation setup
UFO case studies
Simulations were performed for two potential UFOpositions ≈30 m apart (see figure below):
◦ Pos #1: in the QBBI.A19R interconnect
◦ Pos #2: in the MB.C19R center
Beam–UFO interactions:
◦ UFOs were assumed to be composed of Fe
◦ Only inelastic proton–UFO interactions weresimulated
Beam:
◦ Only beam 1 was considered (internal beam) since most UFOs in 19R3 wereobserved for this beam
◦ Simulations were performed for 3.5 TeV (both UFO positions) and 7 TeV(UFO pos #1 only)
Uncertainties:
◦ Note that simulations can always be affected by a certain systematic error,e.g. due to geometry approximations (still, arc model is reasonably accurate)
◦ For some quantities, statistical error can be high, in particular BLM signals inBLMs upstream of UFOs or in BLMs at large distances
MB.B19R3 MB.C19R3 MB.A19R3 MQ.19R3
BLM 1
Pos #1 Pos #2beam
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 5 / 14
Results, Part I: BLM response
BLM signals: MC vs measurements (2011)
MB.B19R3 MB.C19R3 MB.A19R3 MQ.19R3
Pos #1 Pos #2beam
MSCBB.19R3MQT.19R3
BLM 1
BLM 6
BLM 5
BLM 4
BLM 3
BLM 2
# Name FromIP3 (m)
1 BLMQI.19R3.B2E30 MQ 860.22 BLMQI.19R3.B1I10 MQ 863.33 BLMQI.19R3.B2E20 MQ 864.24 BLMQI.19R3.B1I20 MQ 865.45 BLMQI.19R3.B2E10 MQ 866.76 BLMQI.19R3.B1I30 MQ 869.2
Figure right:
◦ Shows a set of BLM pattern measuredbetween 04/2011 and 10/2011
◦ Red crosses: one of the largest UFOsmeasured in 19R3 (15/10/2011), withRS7 of BLMQI.19R3.B1I10 MQ being
3.9×10−4 Gy/sec
◦ All values normalized to signalmeasured with BLMQI.19R3.B1I10 MQ
◦ Note: statistical error of simulationresults large for Pos #1 (more CPUtime needed)
10-2
10-1
100
101
860 862 864 866 868 870
DB
LM/D
BL
MQ
I.19
R3.
B1I
10_M
Q
Distance to IP3 (m)
Red: largest UFO measured in 19R3 in 2011
FLUKA (UFO pos #1)FLUKA (3.5 TeV, UFO pos #2)
Measurements 2011 (3.5 TeV)
Given the spread in measured BLM data and the current statistical error of simulation results:
◦ no disentanglement of positions was possible for 2011 data
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 6 / 14
Results, Part I: BLM response
BLM signals: Measurements (2012)
Additional BLMs in 2012:
◦ Four additional BLMs were installed along the MBs in19R3 by the BLM team (S. Grishin, R. Tissier) in Feb2012 (installation triggered by Tobias)
# Name From IP3 (m)N1 BLMEI.19R3.B1I20 MBB.A19R3 826.8N2 BLMEI.19R3.B1I30 MBB.A19R3 830.8N3 BLMEI.19R3.B1I10 MBB.B19R3 846.5N4 BLMEI.19R3.B1I20 MBB.B19R3 858.1
MB.B19R3 MB.C19R3 MB.A19R3 MQ.19R3
BLM N1 BLM N2 BLM N3 BLM N4
Pos #1 Pos #2beam
MSCBB.19R3MQT.19R3
BLM 1
BLM 6
BLM 5
BLM 4
BLM 3
BLM 2
Table on the right:
◦ By courtesy of Tobias
◦ UFOs in 19R3 measured sofar in 2012 (up to the endof April)
◦ Largest BLM signals seenin different BLMs
◦ The few largest of allUFOs were recorded inBLMQI.19R3.B1I10 MQ
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 7 / 14
Results, Part I: BLM response
BLM signals: MC vs measurements (04/2012)
MB.B19R3 MB.C19R3 MB.A19R3 MQ.19R3
BLM N1 BLM N2 BLM N3 BLM N4
Pos #1 Pos #2beam
MSCBB.19R3MQT.19R3
BLM 1
BLM 6
BLM 5
BLM 4
BLM 3
BLM 2
Figure right:
◦ Shows the BLM pattern for the threelargest UFO events in 19R3 so farobserved in 2012 (largest UFOindicated by red crosses, where RS7 ofBLMQI.19R3.B1I10 MQ =2.5×10−4 Gy/sec)
◦ BLMs N1 and N2 not shown sincemeasured signal is very small
◦ All values normalized to signalmeasured with BLMQI.19R3.B1I10 MQ
◦ Note: simulation results obtained for3.5 TeV, while measurements are atenergies between 3.67 and 4 TeV(ramp, stable beams)
◦ Note: statistical error of simulationresults large for Pos #1 (more CPUtime needed)
Inelastic proton-UFO interactions required toproduce a signal as measured on 8/4/2011:
◦ Assuming Pos #2: ∼4 × 106
10-3
10-2
10-1
100
101
102
845 850 855 860 865 870
DB
LM/D
BL
MQ
I.19
R3.
B1I
10_M
Q
Distance to IP3 (m)
o UFO
Pos #
2
Red: largest UFO measured in 19R3 between 05/04/2012 and 20/04/2012
FLUKA (3.5 TeV, UFO pos #1)FLUKA (3.5 TeV, UFO pos #2)
Measurements 04/2012 (3.6-4 TeV)
UFO location:
◦ For these UFO events, simulation results strongly suggest UFO location to be rather closer to Pos#2 than Pos #1
◦ More UFO locations need to be studied to get more conclusive results
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 8 / 14
Results, Part II: energy density in magnets
Peak energy density in MB coils for [email protected] TeV and 7 TeV
MB.B19R3 MB.C19R3 MB.A19R3 MQ.19R3
BLM 1
Pos #1 Pos #2beam
Only UFO in Pos # 1 considered
Figure right:
◦ Shows peak energy density in MBmagnet coils
◦ All values per inelastic proton-UFOinteraction
Maximum peak energy density:
◦ Caused by neutral particles hitting thebent magnet aperture
Maximum peak energy density perinteraction:
◦ [email protected] TeV: ∼6 × 10−8 mJ/cm3
◦ p@7 TeV: ∼2.5 × 10−7 mJ/cm3
10-11
10-10
10-9
10-8
10-7
10-6
830 835 840 845 850 855 860 865 870
Distance to IP3 (m)
Peak
ene
rgy
dens
ity p
er in
elas
tic
prot
on-U
FO in
tera
ctio
n (m
J/cm
3 )
MB.B19R3 MB.C19R3
3.5 TeV7 TeV
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 9 / 14
Results, Part II: energy density in magnets
Lateral energy density profile in MB magnet for [email protected] TeV
Only UFO in Pos # 1 considered:
◦ UFO in interconnect upstream ofMB.B19R3 (see previous slide)
Plots below:
◦ Lateral energy density profiles perinelastic proton-UFO interaction (in alongitudinal layer of 10 cm thickness)
◦ Longitudinal position as indicated byarrows in plot on the right
10-9
10-8
10-7
830 832 834 836 838 840 842 844 846
Distance to IP3 (m)
Peak
ene
rgy
dens
ity p
er in
elas
tic
prot
on-U
FO in
tera
ctio
n (m
J/cm
3 )
MB.B19R3
3.5 TeV
MB cross section at longitudinal center
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
Energy density (mJ/cm3)
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
Energy density (mJ/cm3)
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
Energy density (mJ/cm3)
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
◦ Negative x: internal beam
◦ Beam direction: out of the screen
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 10 / 14
Results, Part II: energy density in magnets
Lateral energy density profile in MB magnet for p@7 TeV
Only UFO in Pos # 1 considered:
◦ UFO in interconnect upstream ofMB.B19R3
Plots below:
◦ Lateral energy density profiles perinelastic proton-UFO interaction (in alongitudinal layer of 10 cm thickness)
◦ Longitudinal position as indicated byarrows in plot on the right
10-9
10-8
10-7
10-6
830 832 834 836 838 840 842 844 846
Distance to IP3 (m)
Peak
ene
rgy
dens
ity p
er in
elas
tic
prot
on-U
FO in
tera
ctio
n (m
J/cm
3 )
MB.B19R3
7 TeV
MB cross section at longitudinal center
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
Energy density (mJ/cm3)
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
Energy density (mJ/cm3)
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
Energy density (mJ/cm3)
-30 -20 -10 0 10 20 30
x (cm)
-30
-20
-10
0
10
20
30
y (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
◦ Negative x: internal beam
◦ Beam direction: out of the screen
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 11 / 14
Results, Part II: energy density in magnets
Longitudinal energy density profile for [email protected] and 7 TeV
Only UFO in Pos # 1 considered:
◦ UFO in interconnect upstream ofMB.B19R3
Plots right:
◦ Longitudinal energy density profile inthe horizontal plane of the MB.B19R3(again per proton-UFO interaction)
◦ Plot at top: [email protected] TeV
◦ Plot at bottom: p@7 TeV
Drawing plane
Beamdirection
Energy density (mJ/cm3)
830 832 834 836 838 840 842 844 846
Distance to IP3 (m)
-30
-20
-10
0
10
20
30
x (c
m)
10-1410-1310-1210-1110-1010-910-810-710-6
Energy density (mJ/cm3)
830 832 834 836 838 840 842 844 846
Distance to IP3 (m)
-30
-20
-10
0
10
20
30x
(cm
)
10-1410-1310-1210-1110-1010-910-810-710-6
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 12 / 14
Results, Part III: Direct comparison BLM response and peak energy density
BLM dose & peak energy density in MB coils for [email protected]
Additional BLMs:
◦ Fake BLMs were included in simulationto study in more detail the BLM pattern
MB.B19R3 MB.C19R3 MB.A19R3 MQ.19R3
BLM 1
Pos #1 Pos #2beam
10-15
10-14
10-13
10-12
10-11
820 830 840 850 860 870
Distance to IP3 (m)
BL
M d
ose
per
inel
astic
prot
on-U
FO in
tera
ctio
n (G
y)
o Pos
#1
Fake BLMsInstalled BLMs
10-10
10-9
10-8
10-7
820 830 840 850 860 870
Distance to IP3 (m)
Peak
ene
rgy
dens
ity p
er in
elas
tic
prot
on-U
FO in
tera
ctio
n (m
J/cm
3 )
MB.B19R3 MB.C19R3
o Pos
#1
10-15
10-14
10-13
10-12
10-11
820 830 840 850 860 870
Distance to IP3 (m)
BL
M d
ose
per
inel
astic
prot
on-U
FO in
tera
ctio
n (G
y)
o UFO
Pos #
2
Fake BLMsInstalled BLMs
10-10
10-9
10-8
10-7
820 830 840 850 860 870
Distance to IP3 (m)
Peak
ene
rgy
dens
ity p
er in
elas
tic
prot
on-U
FO in
tera
ctio
n (m
J/cm
3 )MB.B19R3 MB.C19R3
o UFO
Pos #
2
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 13 / 14
Summary and conclusions
Summary and conclusions
◦ UFO location in arc cell 19R3◦ New BLMs yield a significant gain in resolution◦ First observations in 2012: UFOs seem to occur all along the arc cell◦ Largest UFOs events observed so far in 2012 were “close” to MQ
(potentially in the MB located just upstream)◦ More simulations (involving different UFO locations) would be required
to narrow down individual UFO locations
◦ For the same number of interactions and assuming the UFO to be locatedjust upstream of an MB:
◦ The simulation predicts a peak energy density in the MB coils about 4times higher at 7 TeV than at 3.5 TeV
◦ Correspondance between maximum BLM signal and peak energy density inMB coils:
◦ Impacted by UFO location in arc cell
A. Lechner (on behalf of the FLUKA team) May 4th , 2012 14 / 14
IntroductionSimulation setupResults, Part I: BLM responseResults, Part II: energy density in magnetsResults, Part III: Direct comparison BLM response and peak energy densitySummary and conclusions
