Radiation study of the TPC electronics

Radiation study of the TPC electronics

Georgios Tsiledakis, GSI

Topics

•Radiation transport code (FLUKA)

•Geometry description

•Definition of the suitable scoring region

•Calculation of the number of the particles and their energy distributions defining the left end-plate of the TPC made of 1cm and 10cm Al respectively

•Estimation of the particle fluences

•Summary

Simulation code (FLUKA)

• Hadron-hadron and hadron-nucleus elastic and inelastic interactions 0-20 TeV

• Electromagnetic and muon interactions 0-100 TeV (pair production and bremsstrahlung, multiple coulomb scattering and magnetic field transport, delta ray production)

• Particle transport: all stable hadrons, electrons, positrons, muons, photons

• Neutron multigroup transport and interactions 0-20 MeV• Neutron capture reactions with explicit photon emission• Accurate and detailed ionization energy loss• Efficient model for multiple scattering for all charged

particles

For this study, the transport cut for charged hadrons is set to 10 keV.The energy thresholds for electrons and photons that are used in central detectors are50 keV and 30 keV respectively.

Geometry descriptionFLUKA uses the Combinatorial Geometry. About 3200 volumes and 1500 regions are needed to describe the full ALICE experimental area, including the cavern, tunnels, vertical shafts, rooms, shielding, inner triplet and separation dipoles, the surrounding hall, beam elements, detectors and racks.Particle backscattering from concrete walls of caverns and shafts is taken into accountby approximating the walls by a 30 cm layer of concrete. Regions behind this layer aretreated as black-holes.

TPC gas volume: 79.25<r<278 cm and |z|<275 cmTPC gas: (90% Ne + 10% CO2) Wgttot=0.9MNe+0.1*(MC+2MO) There is a correspondence between FLUKA materials and low-energyneutron cross-sections.FLUKA low-energy neutron library doesn’t include Neon. Therefore, Fluorine has been chosen instead.

TPC gas

TPC gas

Al

Al

Air

Air

278.17

227.2

177.2

127.2

77.2

-77.2

-127.2

-177.2

-227.2

-278.17

-296 -285 -275

4 radial segments of 1cm width for scoring (-297<z<-296)

1234

4321 10cm of Al

(-285<z<-275)

or

1cm of Al(-276<z<-275)

Scoring region

[cm]

4 scored layers of airlayers Volume (cm3) Area (cm2)

1 32107 32107

2 47815 47815

3 63523 63523

4 80923 80923

[cm]

[cm]

1 FLUKA event: 80000 pions and kaons (HIJING) are propagated in the ALICE geometry at |eta|<5 In this study 5 fluka runs have taken place for 16000 primaries each run and after merging we had one central event in total, with 1cm and 10cm of Al respectively.

Scoring region

Estimation of particle numbers

•The radiation is strongly correlated to the total number of produced particles.•Use of a “current” estimator for counting particles from a boundary crossing scoring on each of the 4 layers apart that form the scoring region.

Energy spectra

1cm AlThermal neutrons ~0.025 eV

Energy spectra

1cm Al

10cm Al

98.5 % p99.9 % +/-,+/- E>10MeV99 % +/-4.1 % n

72 % e+/- with E>0.5 MeV

98.7 % p99.9 % +/-,+/- E>10MeV98.5 % +/-6.5 % n

93.9 % e+/- with E>0.5 MeV

Number of particles per central event

layers 1 2 3 4 sum 1 2 3 4 sum

protons 302 238 201 164 905 355 219 136 105 815

electrons 6820 2528 1084 1026 11458 4241 2382 1635 1524 9782

positrons 1682 706 435 285 3108 2731 1300 799 639 5469

photons 73057 67091 49298 28252 217698 66096 106206 45370 41727 259399

neutrons 17464 28906 39706 47574 133650 18180 26106 31812 37149 113247

muons+/- 442 402 436 305 1585 281 243 235 257 1016

pions+/- 2230 1638 1472 1133 6473 1871 1191 1045 835 4942

kaons+/- 185 102 83 60 430 164 79 62 48 353

primaries 101 174 452 499 1226 10 17 52 54 133

charged 11663 5615 3713 2974 23965 9644 5415 3913 3409 22381

1cm Al 10cm Al

Multiply with 4*1010 to get the number of particles traversing a layer in 10 ALICE yearsof Pb+Pb.[(8000 Hz)*(10 years)*(2.5 *106 sec/year)/(5 :to get from central to min bias multiplicity)]

layers 1 2 3 4 sum

protons 1.21E+13 9.52E+12 8.04E+12 6.56E+12 3.62E+13

electrons 2.73E+14 1.01E+14 4.34E+13 4.10E+13 4.58E+14

positrons 6.73E+13 2.82E+13 1.74E+13 1.14E+13 1.24E+14

photons 2.92E+15 2.68E+15 1.97E+15 1.13E+15 8.71E+15

neutrons 6.99E+14 1.16E+15 1.59E+15 1.90E+15 5.35E+15

muons+/- 1.77E+13 1.61E+13 1.74E+13 1.22E+13 6.34E+13

pions+/- 8.92E+13 6.55E+13 5.89E+13 4.53E+13 2.59E+14

kaons+/- 7.40E+12 4.08E+12 3.32E+12 2.40E+12 1.72E+13

primaries 4.04E+12 6.96E+12 1.81E+13 2.00E+13 4.90E+13

charged 4.67E+14 2.25E+14 1.49E+14 1.19E+14 9.59E+14

Number of particles per 10 ALICE years 1cm Al

80 100 120 140 160 180 200 220 240 260 280 300

1E13

1E14

1E15

Nu

mb

er

of

pa

rtic

les

pe

r 1

0 A

LIC

E y

ea

rs

Radius (cm)

p e- e+ g n +,- +,- k+,k- primaries all charged


layers 1 2 3 4 sum

protons 1.42E+13 8.76E+12 5.44E+12 4.20E+12 3.26E+13

electrons 1.70E+14 9.53E+13 6.54E+13 6.10E+13 3.91E+14

positrons 1.09E+14 5.20E+13 3.20E+13 2.56E+13 2.19E+14

photons 2.64E+15 4.25E+15 1.81E+15 1.67E+15 1.04E+16

neutrons 7.27E+14 1.04E+15 1.27E+15 1.49E+15 4.53E+15

muons+/- 1.12E+13 9.72E+12 9.40E+12 1.03E+13 4.06E+13

pions+/- 7.48E+13 4.76E+13 4.18E+13 3.34E+13 1.98E+14

kaons+/- 6.56E+12 3.16E+12 2.48E+12 1.92E+12 1.41E+13

primaries 4.00E+11 6.80E+11 2.08E+12 2.16E+12 5.32E+12

charged 3.86E+14 2.17E+14 1.57E+14 1.36E+14 8.95E+14


80 100 120 140 160 180 200 220 240 260 280 3001E11

1E12

1E13

1E14

1E15

Nu

mb

er

of

pa

rtic

les

pe

r 1

0 A

LIC

E y

ea

rs

Radius (cm)

p e- e+ g n +,- +,- k+,k- primaries all charged


Zv (cm)

Cou

nts

1cm Al

10cm Al

Z distribution of protons origin in the scoring region

Most of the primary protons are stopped in the 10cm Al end-plateand a significant slow proton production start

Particle fluxes and fluences

"Flux" counts the rate of arrivals per unit area indepedent of particle direction and its real physical meaning is that of path density, whereas "current" counts the rate crossing through a given plane, referred to area elements in the surface of the plane.

In FLUKA, flux is defined as the track-length of a particle per unit of volume and its unit can be expressed as (cm-2 s-1) and fluence is the time integral of flux expressed in units of (cm-2).

The results of the FLUKA tracklength estimator are always given as differential distributions of fluence in energy (cm-2 GeV –1 ) per primary.

The following plots are designed to allow visual integration of fluence having the areas under the curves proportional to the fluence (lethargy spectrums).

1 cm Aluminum

Energy (GeV)

dΦ/dE * E

Particles/cm2/primary

layer 1

layer 1

Cumul. Fluence (Particles/cm2/primary)

per central event

total:1.134e-05 +/- 2 %

thermal:1.687e-06

layer 1 layer 3

dΦ/dE * E dΦ/dE * E

Energy (GeV) Energy (GeV)

1 cm Aluminum

layer 1

Cumul. Fluence (Particles/cm2/primary) per central event

total:8.91E-06 +/- 45 %

layer 3


total:1.22E-06 +/- 7 %

Particles/cm2/primary Particles/cm2/primary

layer 1

Energy (GeV)

dΦ/dE * E

layer 1

dΦ/dE * E

Energy (GeV)

1cm Al 10cm Al

Particles/cm2/primaryParticles/cm2/primary

1.66E-7 +/- 6 % 1.87E-7 +/- 9 %


Cumul. Fluences (Particles/cm2/primary) per central event

layers 1 2 3 4

protons 1.66E-7 +/- 6 % 9.36E-8 +/- 8 % 7.05E-8 +/- 6 % 4.21E-8 +/- 7 %

electrons/positrons 7.33E-6 +/- 56 %

1.13E-6 +/- 24 % 5.4E-7 +/- 16 % 3.42E-7 +/- 38 %

neutrons 1.13E-5 +/- 2 % 1.17E-5 +/- 1% 1.18E-5 +/- 0.5 % 1.16E-5 +/- 1 %

thermal neutrons 1.69E-6 1.69E-6 1.75E-6 1.67E-6

muons+/- 3.17E-7 +/- 8 % 1.94E-7 +/- 6 % 1.79E-7 +/- 7 % 9.33E-8 +/- 4 %

pions+/- 1.02E-6 +/- 1 % 5.69E-7 +/- 3 % 4.1E-7 +/- 4% 2.67E-7 +/- 4 %

kaons+/- 7.66E-8 +/- 4 % 3E-8 +/- 8 % 2E-8 +/- 6 % 1.26E-8 +/- 7 %

charged 8.91E-6 +/- 46 %

2.01E-6 +/- 13 % 1.22E-6 +/- 7 % 7.57E-7 +/- 17 %

1cm Al

Multiply with 3.2*1015 to get the cumulative fluences for each layer in 10 ALICE years of Pb+Pb. [(80000 primaries) *(4*1010)=3.2*1015]

Cumul. Fluences (Particles/cm2/primary) per central event

layers 1 2 3 4

protons 1.87E-7 +/- 9 % 9.E-8 +/- 2 % 4.12E-8 +/- 8 % 2.49E-8 +/- 10 %

electrons/positrons 3.76E-6 +/- 9 % 1.35E-6 +/- 7 % 7.41E-7 +/- 12 % 5.46E-7 +/- 7.5 %

neutrons 1.05E-5 +/- 1 % 9.83E-6 +/- 0.5% 9.83E-6 +/- 1 % 9.49E-6 +/- 1.5 %

thermal neutrons 1.21E-6 1.04E-6 1.11E-6 1.25E-6

muons+/- 1.78E-7 +/- 5 % 1.01E-7 +/- 8 % 6.67E-8 +/- 4 % 7.88E-8 +/- 19.5 %

pions+/- 8.55E-7 +/- 2 % 3.92E-7 +/- 2 % 2.83E-7 +/- 4% 1.97E-7 +/- 6 %

kaons+/- 6.81E-8 +/- 12 %

2.48E-8 +/- 15 % 1.47E-8 +/- 15 % 9.66E-9 +/- 15 %

charged 5.05E-6 +/- 6 % 1.96E-6 +/- 5 % 1.15E-6 +/- 8 % 8.57E-7 +/- 4 %

10cm Al

Multiply with 3.2*1015 to get the cumulative fluences for each layer in 10 ALICE years of Pb+Pb. [(80000 primaries) *(4*1010)=3.2*1015]

Cumul. Fluences (Particles/cm2) per 10 ALICE years

layers 1 2 3 4

protons 5.31E+08 +/- 6 % 3.00E+08 +/- 8 % 2.26E+08 +/- 6 % 1.35E+08 +/- 7 %

electrons/positrons 2.35E+10 +/- 56 % 3.62E+09 +/- 24 % 1.73E+09 +/- 16 % 1.09E+09 +/- 38 %

neutrons 3.62E+10 +/- 2 % 3.74E+10 +/- 1 % 3.78E+10 +/- 0.5 % 3.71E+10 +/- 1 %

thermal neutrons 5.41E+09 5.41E+09 5.60E+09 5.34E+09

muons+/- 1.01E+09 +/- 8 % 6.21E+08 +/- 6 % 5.73E+08 +/- 7 % 2.99E+08 +/- 4 %

pions+/- 3.26E+09 +/- 1 % 1.82E+09 +/- 3 % 1.31E+09 +/- 4 % 8.54E+08 +/- 4 %

kaons+/- 2.45E+08 +/ -4 % 9.60E+07 +/- 8 % 6.40E+07 +/- 6 % 4.03E+07 +/- 7 %

charged 2.85E+10 +/- 46 % 6.43E+09 +/- 13 % 3.90E+09 +/- 7 % 2.42E+09 +/- 17 %

1cm Al

80 100 120 140 160 180 200 220 240 260 280 300

1E8

1E9

1E10

Cu

mu

lativ

e F

lue

nce

(p

art

icle

s/cm

2) p

er

10

AL

ICE

ye

ars

Radius (cm)

p e+,e- n thermal n +,- +,- k+,k- all charged

Cumul. Fluences (Particles/cm2) per 10 ALICE years 1cm Al

layers 1 2 3 4

protons 5.98E+08 +/- 9 % 2.88E+08 +/- 2 % 1.32E+08 +/- 8 % 7.97E+07 +/- 10 %

electrons/positrons 1.20E+10 +/- 9 % 4.32E+09 +/- 7 % 2.37E+09 +/- 12 % 1.75E+09 +/- 7.5 %

neutrons 3.36E+10 +/- 1 % 3.15E+10 +/- 0.5 % 3.15E+10 +/- 1 % 3.04E+10 +/- 1.5 %

thermal neutrons 3.87E+09 3.33E+09 3.55E+09 4.00E+09

muons+/- 5.70E+08 +/- 5 % 3.23E+08 +/- 8 % 2.13E+08 +/- 4 % 2.52E+08 +/- 19.5 %

pions+/- 2.74E+09 +/- 2 % 1.25E+09 +/- 2 % 9.06E+08 +/- 4 % 6.30E+08 +/- 6 %

kaons+/- 2.18E+08 +/- 12 % 7.94E+07 +/- 15 % 4.70E+07 +/- 15 % 3.09E+07 +/- 15 %

charged 1.62E+10 +/- 6 % 6.27E+09 +/- 5 % 3.68E+09 +/- 8 % 2.74E+09 +/- 4 %

10cm Al

Cumul. Fluences (Particles/cm2) per 10 ALICE years

80 100 120 140 160 180 200 220 240 260 280 300

1E8

1E9

1E10

Cu

mu

lativ

e F

lue

nce

(p

art

icle

s/cm

2) p

er

10

AL

ICE

ye

ars

Radius (cm)

p e+,e- n thermal n +,- +,- k+,k- all charged

Cumul. Fluences (Particles/cm2) per 10 ALICE years 10cm Al

Layer1cm Al 1 2 3 4Total Edep

(MeV)

55.7 +/- 45.6 20.64 +/- 3.9 19.44 +/- 1.76 14.72 +/- 4.8

Edep from e+/-,gMeV)

39.7 +/- 34.4 8.65 +/- 2.9 6.16+/-1.92 2.6 +/- 1

Layer10cm Al

1 2 3 4

Total Edep (MeV) 33.8 +/- 7.3 20.96 +/- 2.4 15.76 +/- 4.8 15.6 +/- 4

Edep from e+/-,gMeV)

19.68 +/- 4.2 11.84 +/- 2.1 8.85 +/- 4 5.91 +/- 2.9

Total and EM energy deposition in these 1cm thick layers of air perone central event

To obtain doses (in Gy) these results must be multiplied by (109*e/rho), where rho is the material density in g/cm3 and e the electron charge in Cb(rhoair=1.2E-3)

Summary

The cumulative fluence of neutrons as well as of charged particles is expected to be of the order of 1010 particles/cm2 per 10 ALICE years

The results of this simulation concerning the particle rates, fluences and energy distributions should be taken into account

for checking the radiation tolerance of the electronics

FLUKA calculation of the slow proton production in the TPC with the standard gas and after the addition of 5% Methane

Calculation of the slow proton production in the TPC• Use of a “current” estimator for counting particles.• Take into account only the first “hit” position in the TPC.• Include all the “unique” protons that are crossing or are created in the TPC region.

Log10(Age) (sec) Log10(Ekin) (GeV)

TPC gas with 5% CH4

TPC gas

Proton time spectra Proton energy spectra

Counts Counts

TPC gas volume: 79.25<r<278 cm and |z|<275 cm

TPC gas: (90% Ne + 10% CO2) Wgttot=0.9MNe+0.1*(MC+2MO)

New TPC gas: (85% Ne + 10% CO2 + 5% CH4)

Radial distribution of protons origin in the TPC

Rv (cm)

Counts

Conclusions

Prompt neutrons can scatter on H (due to the presence of 5% CH4

in the TPC gas) and produce a knockout proton background. Each slow proton deposit on average ~ 1.1 MeV having ~2 cm tracklength The additional energy deposition in the TPC due to them should be

less than ~3.5%

Slow protons/mip~270

# protons/central event

# protons created in the gas/central event

No CH4 3’208 120

5% CH4 4’364 1’415

Documents

Radiation study of the TPC electronics