DPA calculations with FLUKAA. Lechner (CERN) Dec 5th, 2014 11 / 20 DPA in LHC primary collimators...

DPA calculations with FLUKA

A. Lechner, L. Esposito, P. Garcia Ortega, F. Cerutti, A. Ferrari, E. Skordison behalf of the FLUKA team (CERN)

with valuable input from

R. Bruce, P.D. Hermes, S. Redaelli (CERN) and N. Mokhov (FNAL)

2nd EuCARD2 ColMat-HDED annual meeting

Dec 5th, 2014

A. Lechner (CERN) Dec 5th , 2014 1 / 20

Introduction

Contents

1 Introduction

2 FLUKA and DPA

3 DPA in LHC primary collimators (IR7) due to halo particles (preliminary)

4 DPA in HL-LHC inner triplet magnets (IR1/5) due to proton collision debris

5 Summary


Introduction

Radiation transport in matter ... stochastic in nature


Introduction

LHC beam-machine interaction studies: from beam losses to secondary shower description

FLUKA is regularly used at CERN to perform LHCbeam-machine interaction simulations in the context of

machine protection

collimation

BLM threshold settings

high-luminosity upgrade

design studies for new devices (absorbers etc.)

radiation to electronics (R2E project)

activation studies

background to experiments

...

Types of LHC beam losses simulated withFLUKA – both, normal and accidental ...

luminosity production in experiments

halo collimation

injection and extraction failures

residual gas in vacuum chamber

dust particles falling into beam

...

Main focus of this presentation

• DPA calculations with FLUKA (incl. examples)


Introduction

Validation of dose calculations for TeV proton losses (controlled beam loss experiments)

• FLUKA is based, as far as possible, on well bench-marked microscopic models

• However, first years of LHC operation also allowed tovalidate FLUKA dose predictions against Beam LossMonitors (BLMs) measurements

• BLMs measure dose from secondary showers inmachine elements (magnets, collimators, etc.)

• Several thousand BLMs are installed around the ring

(ICs, filled with N2 gas, about 1500 cm2 active vol.)

Losses induced by beam wire scanner ([email protected] TeV)

- Quench test 2010 in LHC IR4 (M. Sapinski et al.)

- Wire scans: showers due to collision products registered in BLMsinstalled on downstream magnets (∼35 from wire scanner)

10-1

100

101

10115 10120 10125 10130 10135

DB

LM

/N

i (pG

y)

s (m)

FLUKAMeasurement

Absolute comparison!

Ni =number of inelastic proton-wire interactions (derived analytically)

Direct losses on MQ beam screen† (p@4 TeV)

- Quench test 2013 in arc sector 56 (A. Priebe et al.)

- Proton losses on beam screen (over ∼1.5 m) by means of orbitbump/beam excitation, dose measured by BLMs outside of MQcryostat

10-1

100

101

16172 16176 16180

DB

LM

/N

p (

pGy)

s (m)

FLUKAMeasurement

Absolute comparison! (Np=number of lost protons (measured)

†FLUKA simulations based on MAD-X loss distribution from V. Chetvertkova et al.


FLUKA and DPA

Contents

1 Introduction

2 FLUKA and DPA



5 Summary


FLUKA and DPA

FLUKA and DPA in a nutshell

• DPA can be induced by all particles produced in the hadronic cascade

• displacement damage related to energy transfers to atomic nuclei

Charged particles (incl.heavy ions)

During transport DPA based on non-ionizing energy loss (NIEL)along particle step (restricted above damage thresh-old Eth), using Lindhard partition function ζ(T )and energy dependent displacement efficiency κ(T )

Figures: stopping powers for oxygen ions in silicon (left), silver ions in gold(right)


FLUKA and DPA

FLUKA and DPA in a nutshell

continued from previous page:

Charged particles (incl.heavy ions)

Particle falls belowtransport threshold

Nuclear stopping power integrated (using Lindhard partitionfunction)

Elastic and inelastic en-counters

Recoils and secondary charged particles explicitly produced iftheir energy lies above transport threshold (i.e. they becomea projectile), otherwise they are treated as below threhold.

Neutrons

≤20 MeV1 DPA is based on (un)restricted NIEL as provided by NJOY

> 20 MeV recoils: same as for elastic and inelastic encounters of chargedparticles

1For ≤20 MeV neutron transport, FLUKA uses multi-group approach (group-to-groupscattering probabilities from NJOY).


DPA in LHC primary collimators (IR7) due to halo particles (preliminary)

Contents

1 Introduction

2 FLUKA and DPA



5 Summary



Estimating DPA in LHC primary collimators (made of AC150)

• Two step simulation:

◦ Spatial distribution of inelastic proton-nucleuscollisions in collimators is derived by means ofmulti-turn tracking simulations (usingFLUKA-Sixtrack coupling, in collaborationwith LHC collimation team)

◦ Starting from this loss distribution, the DPAdistribution is calculated in detailed (low-cut)FLUKA shower calculations in jaw ofTCP.C6L7

• Note:

◦ By starting from the spatial distribution ofinelastic collisions, we neglect the DPAcontribution of primary protons before thecollision

• Assumptions for DPA calculations:

◦ beam energy of 7 TeV◦ horizontal losses only◦ annual beam losses of 1.15×1016 protons

→ corresponding to 40 fb−1 in 2012→ one needs to apply approximately a factor

100 to get an estimate for HL-LHC lumigoal (4000 fb−1)



Spatial distribution of inelastic proton collisions in the horizontal TCP

Tracking results from P. Garcia Ortega.

0.0·1005.0·10131.0·10141.5·10142.0·10142.5·10143.0·10143.5·1014

0 10 20 30 40 50 60

Inel

astic

col

lisio

ns (

1/cm

)

Distance from TCP front (cm)

Long. loss distr. in TCP.C6L7 (1.15x1016 protons lost)

External jaw (pos. x)Internal jaw (neg. x)

1015

1016

1017

1018

1019

0 50 100 150 200

Inel

astic

col

lisio

ns (

1/cm

)

Distance from TCP surface (µm)

Impact parameters in TCP.C6L7 (1.15x1016 protons lost)


→ tracking simulations show unequal sharing of losses between TCP.C6L7 jaws (∼6:1)



DPA in TCP jaws (1.15×1016 protons lost) – preliminary results

TCP.C6L7

-10 -5 0 5 10

x (cm)

-4

-2

0

2

4

y (

cm)

0

1

2

3

4

0 10 20 30 40 50 60

Peak

DPA

(10

-3)


TCP.C6L7 (1.15x1016 protons lost)


DPA in TCP.C6L7, at peak (1.15x1016 protons lost)

-0.21 -0.2 -0.19 -0.18 -0.17 -0.16

x (cm)

-0.1

-0.05

0

0.05

0.1

y (c

m)

10-6

10-5

10-4

10-3

10-2DPA in TCP.C6L7, at peak (1.15x1016 protons lost)

0.16 0.17 0.18 0.19 0.2 0.21

x (cm)

-0.1

-0.05

0

0.05

0.1

y (c

m)

10-6

10-5

10-4

10-3

10-2Assumed Ethr (AC150): 35 eV

Max. DPA: ∼3×10−3

Transp.thre.

photons 100 keV

e−/e+ 500 keV

neutrons 10−5 eV

ions 0.25 keV/nucl

other 1 keV



Anatomy of DPA predictions in TCP jaw – preliminary results

0

1

2

3

4

0 10 20 30 40 50 60

Peak

DPA

(10

-3)


TCP.C6L7, external jaw (1.15x1016 protons lost)

TotalIons (above thresh.)

Pions (above thresh.)Protons (above thresh.)

Electrons (above thresh.)Ions (below thresh.)

Neutrons (below thresh.)

Table below : contributionsto peak DPA at a depth of∼15 cm (for the TCP jawwith higher proton losses)

Peak DPA Type of

contribution: contribution:

62% Ions above transport threshold (>250 eV/nuc)

→ explicitly generated recoils

20% Pions above transport threshold (>1 keV)

5-6% Protons above transport threshold (>1 keV)

5-6% Ions below transport threshold (<250 eV/nuc)

→ non-transported recoils

6-7% Electrons above transport threshold (>500 keV)

<0.5% Others

Percentage values rounded; (statistical) error of contributions: ∼1%


DPA in HL-LHC inner triplet magnets (IR1/5) due to proton collision debris

Contents

1 Introduction

2 FLUKA and DPA



5 Summary



HL-LHC (inner triplet and D1 in IR1/5): FLUKA models and brief recap of layout

FLUKA model by L. Esposito (HL-LHC WP10)

20 30 40 50 60 70 80

Distance from IP (m)

LHCD1Q3Q2a Q2bQ1

MCBX

MCBX

MCBX

20 30 40 50 60 70 80

Distance from IP (m)

HL-LHC

D1Q3Q2a Q2bQ1

MCBX

MCBX

MCBX

CP

• HL performance goal for proton collisions@IR1/5:

◦ instantaneous luminosity of 5×1034 cm−2s−1

(= 5 × design luminosity)

◦ integrated luminosity of 3000 fb−1

(250 fb−1 per year)

HL-LHC: Q1,Q2,Q3→ Nb3Sn; D1, MCBX→ NbTi



Peak DPA and NIEL in coils of triplet quadrupoles, correctors and D1 (3000 fb−1)

0

10

20

30

40

50

20 30 40 50 60 70 80

Pea

k d

ose

(M

Gy

) Q1 Q2a Q2b Q3 D1

MC

BX

MC

BX

MC

BX

0

0.5

1

1.5

2

20 30 40 50 60 70 80

Pea

k D

PA

(10

-4)

0

0.5

1

1.5

20 30 40 50 60 70 80

Pea

k N

IEL

(1

01

2 G

eV/c

m3)

Distance to IP1 (m)

NIELRestricted NIEL

Assumed Ethr : 30 eV

Peak dose vs DPA:

• the latter has itsmaximum in Q1

• see particle fluenceson next page

Max. DPA: ∼1.8×10−4

DPA in Q1b coils , magnet end (10-4)

-10 -5 0 5 10

x (cm)

-10

-5

0

5

10

y (

cm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8


-10 -5 0 5 10

x (cm)

-10

-5

0

5

10

y (

cm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8



Peak fluences in coils of triplet quadrupoles and D1 (3000 fb−1)

0.0·100

5.0·1017

1.0·1018

1.5·1018

2.0·1018

20 30 40 50 60 70 80

Peak

flu

ence

(1/

cm2 )

Q1 Q2a Q2b Q3 D1

PhotonsElectrons and positrons

0.0·100

5.0·1016

1.0·1017

1.5·1017

2.0·1017

20 30 40 50 60 70 80

Peak

flu

ence

(1/

cm2 )

Neutrons

0.0·100

4.0·1015

8.0·1015

1.2·1016

1.6·1016

20 30 40 50 60 70 80

Peak

flu

ence

(1/

cm2 )

Distance to IP1 (m)

ProtonsCharged hadrons

Neutrons in coils:

• max. fluence:1.8×1017 cm−2

• correlation peakneutron fluence –peak DPA

• see anatomy of DPAcalculations in nextpage

Transp.cut:

photons 100 keV

e−/e+ 500 keV

neutrons 10−5 eV

ions 0.25 keV/nucl

other 1 keV



Anatomy of DPA predictions in Q1

Contributions to DPAmaximum in Q1:

• Dominated by low-energy neutrons (forwhich FLUKA relies onNJOY-based values forDPA)


-10 -5 0 5 10

x (cm)

-10

-5

0

5

10

y (

cm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Peak DPA Type of

contribution: contribution:

70.7% Neutrons <20 MeV (NJOY)

24.4% Ions above transport threshold

(>250 eV/nucleon)

→ explicitly generated recoils (from neutron,proton, etc. interactions)

1.7% Protons above transport threshold (>1 keV)

1.6% Ions below transport threshold

(<250 eV/nucleon)

→ non-transported recoils

1.0% Electrons above transport threshold (>500 keV)

0.6% Pions above transport threshold (>1 keV)

<0.1% Others

Percentage values rounded; (statistical) error of contributions: few 0.1%


Summary

Contents

1 Introduction

2 FLUKA and DPA



5 Summary


Summary

Summary

• FLUKA offers a powerful way to calculate DPA for beam losses as encountered in theLHC operational environment or during beam tests

◦ In particular, allows to take into account the contribution of different particle types,including all particles produced in the particle shower development

• DPA estimates for horizontal primary collimator (preliminary):

◦ Simulation predicts a peak DPA of 3×10−3 for ∼40 fm−1 aka 1×1016 protons lost(or ∼0.3 for ∼4000 fm−1)

◦ Predominant contribution comes from recoils◦ However, present calculations still neglect contribution of primary protons before

they have an inelastic interaction

• DPA estimates for HL-LHC proton collision debris impacting on triplet magnets (IR1/5):

◦ FLUKA predicts max. DPA of ∼1.8×10−4 in Q1 coils for 3000 fm−1

◦ Dominant contribution due to neutrons <20 MeV (fluence up to 1.8×1017 cm−2)


Date post:	24-Feb-2021
Category:	Documents
Upload:	others
View:	3 times
Download:	0 times

DPA calculations with FLUKAA. Lechner (CERN) Dec 5th, 2014 11 / 20 DPA in LHC primary collimators...

Documents