shielding calculations for the design of new beamlines at...

A. Devienne RADSYNCH17 21/04/17

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A. Devienne¹M.J. García-Fusté¹

Health & Safety Department, ALBA Synchrotron

Shielding calculations for the design of new Beamlines at ALBA Synchrotron


Content

1. Context1.1 ALBA Synchrotron 1.2 Shielding design at ALBA1.2 Objective

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2. Material & Methods2.1 Geometry constrains 2.2 Sources2.3 FLUKA code

3. Results3.1 Shielding elements3.2 Dose maps

4. Open points & Conclusions


1.1 Description of ALBA ALBA Synchrotron: particle accelerator located near Barcelona city

generating bright beams of synchrotron radiation. ALBA accelerates electronsup to 3 GeV.

CELLS: Consortium for the Construction the Exploitation of the SynchrotronLight Laboratory

Staff: 210 persons (53 women)

31.1 ALBA Synchrotron


LINACElectron beam110 MeV

BOOSTER110 MeV to 3 GeV

STORAGE RING3 GeV stored electron beam150 mA (currently) - designed for 400 mA

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perimeter270 m

1.1 Description of ALBA1.1 ALBA Synchrotron


1.2 Shielding design at ALBA

• 2017-2020: Phase III Beamlines (1 Hard X-Raysmicrofocus XAIRA and 1 InstrumentationNOTOS) + upgrade the current BLs ALBA

• 2015 – 2017: Phase II Beamlines (1 InfraredMIRAS and 1 Soft X-Rays LOREA BL) ALBA

• 2012: Phase I Beamlines (4 Hard X-Rays and 3 Soft X-Rays BLs) P. Berkvens (ESRF)

• Tunnel and Linac bunker K. Ott (BESSY)2010

2012

2015 – 2017

2017 – 2020

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1.2 Shielding design at ALBA 6

Tunnel bunkerHard X-Rays Beamline (NCD)

Soft X-Ray Beamline (BOREAS) Infrared Beamline (MIRAS)


E- Beam (3Gev)

Beam Line Optical Hutch

• LOREA is the 9th BL of ALBA and will be dedicated to low-energy ultra-high-resolution angular photoemission for complex materials (energy rangeof 10-1000 eV)

Tunnel(Concrete Wall)

Experimental Area

EndStation

3D preliminary design of LOREA Beamline

1.2 Shielding design at ALBA 7


1.2 Goal of the study• Design LOREA Beamline shielding elements using FLUKA

code to guarantee public access zone1 outside the shielding inoperation

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1 public access zone: equivalent dose rates below 0.5 μSv/h, derived from the dose limit fornon-exposed workers, assuming 2000 h/year)

1.3 Objective

LOREA Beamline 3D FLUKA geometry


2. Material & Methods

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LOREA geometry:

1 side wall T (1.5 m normal concrete)

1 side wall S1 back wall B 1 roof R

Target :2° inclined Mirror M1 (Copper)

Pipes :Diameter 70 mm

Source

LOREA Optical Hutch FLUKA 2D top view

Simplified LOREA Optical Hutch drawing

Target(thickness and material to be defined by calculation)

2.1 Geometry constrains 10


Insertion Device Undulator: Radiation depends on theUndulator parameters and directly proportional to thecurrent intensity (mA).

• Source of radiation

Gas Bremsstrahlung: Electromagnetic cascade producedby the interaction of the e- beam with the residual gasinside the vacuum chamber. It depend on the CurrentIntensity (mA), the e- Energy (3GeV), the pressure andcomposition inside the vacuum chamber

2.2 Sources 11


• DEFAULTS: PRECISION

2.3 Define FLUKA cards

• BIASING: no biasing card used

• PHOTONUC: Activate photonuclear interaction

Some FLUKA parameters (cards) of the simulations:

• EMFCUT: Energy threshold production: 1 keV for photon and 100 keV for e- e+

2.3 FLUKA Code 12


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a) Gas Bremsstrahlung source

Molecule Relative pressure

(%)

H2 80

CO 10

CO2 5

Noble gas 3

H2O 2

Beam: Electron 3 GeVTarget: Residual gas inside a 8.62 m length straight sectionAverage pressure in the straight section: 5.0 × 10-9 mbar (design value) but calculations performed at atmospheric pressure (1 atm) and then scaled at design value (see [4] SLAC–PUB–6410, Nisy E. Ipe, Alberto Fasso)

Electron beam

2.3 FLUKA Code


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a) Gas Bremsstrahlung source:

Photon flux (photons/s) for 400 mA e- beam, scored with USRBDX card at the end of the Storage Ring

straight section

The flux obtained isconsidered as sourcefor the LOREAshieldingcalculations

1 GeV

1e+08

1 keV

2.3 FLUKA Code


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1.E-081.E-051.E-021.E+011.E+041.E+071.E+101.E+131.E+16

1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06

Flux

(Ph/

s/0.

1%B

W)

Energy (eV)

b) Insertion Device source Use of hsource.f sub routine to read histogram and use as a souce for the Shielding Calculation with the BL 1st Mirror as main Target

Apple II LOREA Undulator

Maximum ID photon flux for each Undulator energy range(analytic calculations by ALBA Accelerator division)

2.3 FLUKA Code 15


3. Results

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• Optical HutchShielding thicknesses and material for the LOREA

optics hutch wall and roof (mm)

Corresponding vacuum in straight

section for 0.5 μSv/h (mbar)

Wall S (side wall)

20 mm lead + 50 mm polyethylene 2.5 × 10-8

Roof

15 mm lead 2.5 × 10-8

Wall B (back wall)

60 mm of lead

+ 50 mm of lead in central 1 m2

+ 105 mm of lead Opt-to-Exp guillotine

+ 50 mm of lead local screen behind mirror

+ 20 mm other white beam scattering source

5.0 × 10-8

3. Results3.1 Shieling elements


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• Local shielding elements# Shielding Elements Height

(cm)

Width

(cm)

Thickness

(cm)

Material

1 Tunnel-to-OH guillotine 35.5 30.5 2 Pb

2 Local Pb screen 1 behind mirror 65 70 5 Pb

3 Local Pb screen 2 behind slits 45 45 2 Pb

4 Central reinforcement Pb screen 2 10 10 2 Pb

5 OH-to-EH guillotine 22 22 10.5 Pb

6 OH backwall central reinforcement 100 100 5 Pb

# Shielding Elements Height (cm) Width (cm) Thickness (cm) Material

1 In vacuum Tungsten Beamstop 8 8 5 W

2 Double collimator system 1.4 (aperture) 1.2 (aperture) 5 W

• Beamstops and collimators

3.1 Shielding elements

Dimensions defined by basic ray tracing

Reduction of a factor 15 of the scattered bremsstrahlung radiationescaping from the Optical Hutch through the beampipe


a) Gas Bremsstrahlung source case equivalent dose rate maps(DOSE-EQ) - horizontal view at beam level -

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Photon dose rate map (in µSv/h)

Neutron dose rate map (in µSv/h)

Total dose rate map (in µSv/h) from scattered bremsstrahlung with real LOREA geometry and shielding

0.5µSv/h

3.2 Dose maps

Beamstop

Doble collimationsystem

Lead screen


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Figure Dose rate profile (in µSv/h) from scattered bremsstrahlung outside LOREA as a function of the distance along the wall (in cm) : red curve: photon dose rate; green

curve: neutron dose rate; blue curve: total dose rate

3.2 Dose maps

Side wall (S) Back wall (S)

a) Gas Bremsstrahlung source equivalent dose rate (DOSE-EQ)


a) Gas Bremsstrahlung source case equivalent dose rate maps(DOSE-EQ) - transversal view at beam level -

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Total dose rate map (in µSv/h) from scattered bremsstrahlung with real LOREA

geometry and shielding

0.5µSv/h

Dose rate profile (in µSv/h) from scattered bremsstrahlung outside LOREA Roof (R) as a

function of the distance along the roof (red curve: photon dose rate; green curve: neutron dose rate; blue

curve: total dose rate)

3.2 Dose maps


Shielding requirements for scattered synchrotron radiation are largelymet by the shielding thicknesses required for scattered bremsstrahlung.

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b) ID Undulator dose rate maps (at 400 mA):

Total dose rate map (in µSv/h) from ID Undulator source

3.2 Dose maps


• Comparison with experimental data from ALBA beamlines

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Outside BL

InsideBL

Gamma dose rate measurements at BOREAS BL compared with storage ring current and FE state

Gamma dose rate map (in µSv/h) from scattered bremsstrahlung at LOREA at

400 mA

Results obtained with FLUKA are in agreement with experimental data (Ionizatingchamber FHT192) from a similar Beamline at ALBA ( few µSv/h current inside the Optical Hutch - proportional to the electron beam - and background reading outside)

0.5µSv/h

3.2 Dose maps


4. Open points & conclusion

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1. CPU time vs. Statistical error : 0.3 ms per primary particle, 1e+08 primary sent per cycles, 10 cycles per run 3 to 4 days for each run in 1 CPU 10-15% statistical error after the shielding Statistic improved by parallelization of the

simulations via Batch system to cluster: split into48 inputs (now integrated in Flair)

… (vs. Manpower) use of biaising (in particular playing with importance

inside the shielding element) could allow better statisticin regions of interest,

Use of 2-steps simulations using intermediate results

4.1 Open points


264. Open points4.1 Open points

Beam

Simplified (left) and 3D (right) LOREA Optical Hutch drawing with door on backwall

Target

2. Double frame door on Backwall: thickness optimization on theheaviest frame (600 kg)

Door B46 thickness Corresponding vacuum in straight section for 0.5 μSv/h (mbar)

60 mm lead 5.0×10-8

Door B66 thickness

40 mm lead 6.2×10-8

6 (-2) = 4 cm

6 cm 2 (+3) cm


FLUKA is a powerful code for the design of SynchrotronBeamline shielding (Radioprotection) and will be used at ALBAfor the Phase III Beamlines (2017-2020)

LOREA Optical Hutch shieldingwill be installed on October 2017and commissioned during 2018

Open points can be discussedto optimize the shielding calculations

274.2 Conclusion


Thank you for your attention

Email: [email protected] Website: www.albasynchrotron.es

Mª José García Arnaud Devienne José A. Alcobendas

ALBA Radioprotection Service

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[1] "The FLUKA code: Description and benchmarking" G. Battistoni, S. Muraro, P.R.Sala, F. Cerutti, A. Ferrari, S. Roesler, A. Fasso`, J. Ranft, Proceedings of the HadronicShower Simulation Workshop 2006, Fermilab 6--8 September 2006, M. Albrow, R. Rajaeds., AIP Conference Proceeding 896, 31-49, (2007)[2] "FLUKA: a multi-particle transport code" A. Ferrari, P.R. Sala, A. Fasso`, and J. Ranft,CERN-2005-10 (2005), INFN/TC_05/11, SLAC-R-773[3] Gas Bremsstrahlung Considerations in the Shielding Design of the Advanced PhotonSource Synchrotron Radiation Beam Lines, Nisy E. Ipe, Alberto Fasso , SLAC–PUB–6452[4] Impact of gas bremsstrahlung on synchrotron radiation beamline shielding at theadvanced photon source, Nisy E. Ipe, Alberto Fasso SLAC–PUB–6410[5] Shielding of Beamlines at ALBA: Comparison between different types ofbremsstrahlung, P. Berkvens. ALBA internal report.[6] Comparison of Design and Practices for Radiation Safety among Five SynchrotronRadiation Facilities, James C. Liu, Sayed H. Rokni, Yoshihiro Asano, William R. Casey,Richard J. Donahue, P.K. Job, SLAC-PUB-11139

4.2 References

shielding calculations for the design of new beamlines at...

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