FLUKA STUDIES OF DOSE RATES IN THE ATLAS STANDARD OPENING SCENARIO - - PowerPoint PPT Presentation

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FLUKA STUDIES OF DOSE RATES IN THE ATLAS STANDARD OPENING SCENARIO - - PowerPoint PPT Presentation

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AccApp17 13th International Topical Meeting on the Nuclear Applications of Accelerators FLUKA STUDIES OF DOSE RATES IN THE ATLAS STANDARD OPENING SCENARIO J. C. Armenteros, A. Cimmino, S. Roesler and H. Vincke HSE-RP J. C. Armenteros

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SLIDE 1
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SLIDE 2

FLUKA STUDIES OF DOSE RATES IN THE ATLAS STANDARD OPENING SCENARIO

  • J. C. Armenteros, A. Cimmino, S. Roesler and H. Vincke

HSE-RP

  • J. C. Armenteros Carmona

juan.carlos.armenteros.carmona@cern.ch August 1st, 2017

August 1st, 2017 2/29

AccApp’17 13th International Topical Meeting on the Nuclear Applications of Accelerators

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SLIDE 3

ATLAS Detector

August 1st, 2017 3/29

ATLAS (A Toroidal LHC Apparatus)

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SLIDE 4

Motivation

  • An extended period without beams in the Large Hadron Collider

(LHC) at CERN is scheduled for 2024-2025. This stop in

  • perations, known as Long Shutdown 3 (LS3), is required for the

experiments, as well as the accelerator, to perform crucial consolidation and upgrade tasks.

  • In particular, the ATLAS Inner Detector (ID) will be

decommissioned and replaced by a new tracking system (ITk), allowing the experiment to collect 4000/fb.

  • Given the location of the inner detector with respect to the beam

pipe and the expected integrated luminosity up to LS3 of 300/fb, a detailed radiological assessment of the scheduled work is needed.

August 1st, 2017 4/29

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SLIDE 5

Aim

  • Consider the detector configuration changes

with the toolkit SESAME:

  • Various detector elements will be removed or displaced

during LS, YETS or EYETS (Extended Year End Technical Stop) to facilitate the interventions.

  • This variation of detector geometry strongly influences the

results of the simulation and needs to be taken into account.

August 1st, 2017 5/29

  • Study using the Monte-Carlo particle transport

code FLUKA version 2011.2c.5 and DPMJET-III:

  • The ambient dose equivalent rates in the ATLAS

experimental cavern during future LS.

  • Estimate the expected radiation levels at the ITk

during the High Luminosity LHC shutdown periods.

1 µSv = 0.1 mrem

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SLIDE 6

Method: SESAME

August 1st, 2017 6/29

  • Simulating prompt radiation in the closed geometry, storing

the nuclides produced on a file.

  • Letting these nuclides decay in the open geometry after

some transformations/displacements.

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SLIDE 7

Method: SESAME

August 1st, 2017 7/29

  • Simulating prompt radiation in the closed geometry, storing

the nuclides produced on a file.

  • Letting these nuclides decay in the open geometry after

some transformations/displacements

Big wheel Forward shielding Toroid barrel Small wheel Extended calorimeter Inner detector Big wheel Toroid barrel Small wheel Extended calorimeter Inner detector

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SLIDE 8

Method: SESAME

August 1st, 2017 8/29

  • Simulating prompt radiation in the closed geometry, storing

the nuclides produced on a file.

  • Letting these nuclides decay in the open geometry after

some transformations/displacements

111 cm 123 cm 311 cm

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SLIDE 9

SESAME prompt step

  • The geometry corresponds to the operational closed scenario.
  • The source is a 2×7 TeV colliding proton beam (half-crossing

angle of 142.5 µrad). The total number of simulated proton collisions is 187000.

  • The magnetic field is switched on.
  • The FLUKA physics parameters are the standard for activation

studies:

  • The EM shower is off cause it is not particularly relevant for creation of

isotopes and it is very time consuming.

  • The information of the nuclides is stored with the SESAME

routines in a binary file.

August 1st, 2017 9/29

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SLIDE 10

SESAME decay step

  • The geometry is remodelled to match the standard opening scenario.
  • The source consists of loading the information from the modified binary file with

the nuclide information, where:

  • The nuclides belonging to regions that are transformed, change their position

accordingly.

  • The nuclides from regions that are removed, are also removed.
  • The nuclides created in air, are discarded as the air is continuously flushed with fresh

air during shutdown periods.

  • The magnetic field is turned off.
  • The EM shower is now on.
  • Usual particle thresholds:
  • All particles thresholds set to 100 keV.
  • Low energy neutrons in 260 groups from 0.01 meV to 20 MeV.
  • EM shower cuts for transport and production of electrons: 50 keV, and gammas: 10 keV.

August 1st, 2017 10/29

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SLIDE 11

SESAME decay step

  • The decay of the nuclides is scaled according to the irradiation profile provided by the

Technical Coordinator of ATLAS (ultimate scenario estimates, August 2016).

  • Ion runs can be judged as cooling times due to their small impact in the activation.
  • A 75% of peak luminosity levelling is considered up to LS3.

August 1st, 2017 11/29

  • The proton-proton inelastic total cross

section is of 75 mb up to LS1 and 80 mb afterwards.

  • The irradiation is supposed to be delivered

at the end of the proton run schedule, at the maximum luminosity (conservative scenario).

  • The ambient dose equivalent is scored in

the region of interest:

  • 0 ≤ R ≤ 1500 (150 bins).
  • 0 ≤ φ ≤ 2ϖ (1 bin).
  • 0 ≤ Z ≤ 2500 (250 bins).
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SLIDE 12

FLUKA 1-step

August 1st, 2017 12/29

  • Some regions materials are set to vacuum for decay purposes, to

simulate different contributions from the components that are displaced.

  • Multiple runs: Sum up the scorings (after displacement).
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SLIDE 13

FLUKA 1-step

  • There is only one geometry: the closed scenario.
  • The source is a 2×7 TeV colliding proton beam (half-crossing angle of

142.5 µrad). The total number of simulated proton collisions is 25000 (6 times).

  • One run per component (prompt and decay in a single step).
  • The magnetic field is turned on in the prompt and off in the decay.
  • The same physics cards than in the prompt step in the SESAME

approach, but the EM shower is now on.

  • Usual particle thresholds as from the decay step in the SESAME

approach.

  • The region of interest is extended to avoid artefacts in the

superposition afterwards.

August 1st, 2017 13/29

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SLIDE 14

Comparison: SESAME vs. FLUKA 1-step

August 1st, 2017 14/29

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SLIDE 15

Comparison: SESAME vs. FLUKA 1-step

August 1st, 2017 15/29

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SLIDE 16

Comparison: SESAME vs. FLUKA 1-step

August 1st, 2017 16/29

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SLIDE 17

Comparison: SESAME vs. FLUKA 1-step

  • General overestimation in

FLUKA 1-step method for

  • pen geometries.

August 1st, 2017 17/29

  • Shielding effect in SESAME

scheme for open geometries.

LS4 (28 days)

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SLIDE 18

Comparison: SESAME vs. FLUKA 1-step

  • General overestimation in

FLUKA 1-step method for

  • pen geometries.

August 1st, 2017 18/29

  • Shielding effect in SESAME

scheme for open geometries.

LS4 (56 days)

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SLIDE 19

Comparison: SESAME vs. FLUKA 1-step

  • General overestimation in

FLUKA 1-step method for

  • pen geometries.

August 1st, 2017 19/29

  • Shielding effect in SESAME

scheme for open geometries.

LS4 (181 days)

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SLIDE 20

Results

August 1st, 2017 20/29

  • 28 days of cooling time after

the proton run:

  • At a radial distance of

around 1-2 m from the beam line, it can be considered as controlled radiation area.

  • The remaining cavern is

considered as supervised radiation area.

  • In order to mitigate the

radioactive risk, and also to address any operational problems encountered near the beam pipe, a temporary shielding can also be placed.

2016 (28 days)

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SLIDE 21

Results

August 1st, 2017 21/29

  • 28 days of cooling time after

the proton run:

  • At a radial distance of

around 1-2 m from the beam line, it can be considered as controlled radiation area.

  • The remaining cavern is

considered as supervised radiation area.

  • In order to mitigate the

radioactive risk, and also to address any operational problems encountered near the beam pipe, a temporary shielding can also be placed.

LS2 (28 days)

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SLIDE 22

Results

August 1st, 2017 22/29

  • 28 days of cooling time after

the proton run:

  • At a radial distance of

around 1-2 m from the beam line, it can be considered as controlled radiation area.

  • The remaining cavern is

considered as supervised radiation area.

  • In order to mitigate the

radioactive risk, and also to address any operational problems encountered near the beam pipe, a temporary shielding can also be placed.

LS3 (28 days)

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SLIDE 23

Results

August 1st, 2017 23/29

  • 28 days of cooling time after

the proton run:

  • At a radial distance of

around 1-2 m from the beam line, it can be considered as controlled radiation area.

  • The remaining cavern is

considered as supervised radiation area.

  • In order to mitigate the

radioactive risk, and also to address any operational problems encountered near the beam pipe, a temporary shielding can also be placed.

LS4 (28 days)

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SLIDE 24

Results

August 1st, 2017 24/29

  • 28 days of cooling time after

the proton run:

  • At a radial distance of

around 1-2 m from the beam line, it can be considered as controlled radiation area.

  • The remaining cavern is

considered as supervised radiation area.

  • In order to mitigate the

radioactive risk, and also to address any operational problems encountered near the beam pipe, a temporary shielding can also be placed.

LS5 (28 days)

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SLIDE 25

Results

August 1st, 2017 25/29

  • 28 days of cooling time after

the proton run:

  • At a radial distance of

around 1-2 m from the beam line, it can be considered as controlled radiation area.

  • The remaining cavern is

considered as supervised radiation area.

  • In order to mitigate the

radioactive risk, and also to address any operational problems encountered near the beam pipe, a temporary shielding can also be placed.

LS6 (28 days)

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SLIDE 26

Benchmark

  • Comparison of measurements taken in 2016 YETS.
  • Good agreement but the underestimation might be due to some

material missing in the FLUKA geometry description (ID and flanges).

August 1st, 2017 26/29

0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2 2,4 50 100 150 200 Ratio (simulation/experimental) Distance (cm) FCal/LAr end plate (15.12.2016) FCal/LAr end plate (02.02.2017) SW shielding (15.12.2016) SW shielding (02.02.2017) Beam pipe at 1020 cm (15.12.2016) TAS (09.12.2016) 0,2 0,4 0,6 0,8 1,0 1,2 1,4 20 40 60 80 100 120 140 160 180 200 Ratio (simulation/experimental) Distance (cm) ID end plate (15.12.2016) ID end plate (02.02.2017) Beam pipe at 380 cm (15.12.2016) Beam pipe at 380 cm (02.02.2017) Beam pipe at 470 cm (15.12.2016) Beam pipe at 540 cm (15.12.2016)

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SLIDE 27

Conclusions

  • The SESAME approach is better as:
  • It still relies on FLUKA, it only provides tools to run the simulation.
  • It is not straightforward to transform and combine the scorings in

case of rotations in the FLUKA 1-step, and also precision error can arise because of the displacements and the bin width mismatch.

  • It avoids the repetition of the nuclide production, that has to be

done only once per closed geometry, and is very time consuming.

  • The results are validated according to some measurements taken

in 2016 YETS.

  • The radiation field is more realistically described in the open
  • scenario. Shielding regions can easily be added and the

replacement of components can be considered faster.

August 1st, 2017 27/29

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SLIDE 28

Acknowledgements

I would like to thank:

  • Tim Cooijmans and Moritz Guthoff, for their brilliant idea of

developing SESAME.

  • Ida Bergström for critical feedback and testing, and Chris

Theis for hints on interfacing C++ with FORTRAN77.

  • The CMS Beam and Radiation Instrumentation and

Luminosity (BRIL) working group, for granting Radiation Protection access to the code and letting us implement some new features.

August 1st, 2017 28/29

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SLIDE 29

August 1st, 2017 29