Shielding calculations for the design of new Beamlines at ALBA - PowerPoint PPT Presentation

1 Shielding calculations for the design of new Beamlines at ALBA Synchrotron A. Devienne¹ M.J. García-Fusté¹ Health & Safety Department, ALBA Synchrotron A. Devienne RADSYNCH17 21/04/17

Content 2 1. Context 2. Material & Methods 2.1 Geometry constrains 1.1 ALBA Synchrotron 2.2 Sources 1.2 Shielding design at ALBA 2.3 FLUKA code 1.2 Objective 3. Results 4. Open points & Conclusions 3.1 Shielding elements 3.2 Dose maps A. Devienne RADSYNCH17 21/04/17

1.1 Description of ALBA 3 1.1 ALBA Synchrotron  ALBA Synchrotron: particle accelerator located near Barcelona city generating bright beams of synchrotron radiation. ALBA accelerates electrons up to 3 GeV .  CELLS : C onsortium for the C onstruction the E xploitation of the S ynchrotron L ight L aboratory  Staff: 210 persons (53 women) A. Devienne RADSYNCH17 21/04/17

1.1 Description of ALBA 4 1.1 ALBA Synchrotron LINAC Electron beam 110 MeV perimeter BOOSTER 270 m 110 MeV to 3 GeV STORAGE RING 3 GeV stored electron beam 150 mA (currently) - designed for 400 mA A. Devienne RADSYNCH17 21/04/17

5 1.2 Shielding design at ALBA • 2017-2020: Phase III Beamlines (1 Hard X-Rays microfocus XAIRA and 1 Instrumentation 2017 – 2020 NOTOS ) + upgrade the current BLs  ALBA • 2015 – 2017: Phase II Beamlines (1 Infrared 2015 – 2017 MIRAS and 1 Soft X-Rays LOREA BL)  ALBA 2012 • 2012: Phase I Beamlines (4 Hard X-Rays and 3 Soft X-Rays BLs)  P. Berkvens (ESRF) 2010 • Tunnel and Linac bunker  K. Ott (BESSY) A. Devienne RADSYNCH17 21/04/17

6 1.2 Shielding design at ALBA Hard X-Rays Beamline (NCD) Tunnel bunker Soft X-Ray Beamline (BOREAS) Infrared Beamline (MIRAS) A. Devienne RADSYNCH17 21/04/17

7 1.2 Shielding design at ALBA • LOREA is the 9 th BL of ALBA and will be dedicated to low-energy ultra- high-resolution angular photoemission for complex materials (energy range of 10-1000 eV) End Station Tunnel (Concrete Wall) Experimental Area E- Beam (3Gev) Beam Line Optical Hutch 3D preliminary design of LOREA Beamline A. Devienne RADSYNCH17 21/04/17

8 1.2 Goal of the study 1.3 Objective • Design LOREA Beamline shielding elements using FLUKA code to guarantee public access zone 1 outside the shielding in operation LOREA Beamline 3D FLUKA geometry 1 public access zone: equivalent dose rates below 0.5 μSv/h, derived from the dose limit for non-exposed workers, assuming 2000 h/year) A. Devienne RADSYNCH17 21/04/17

9 2. Material & Methods A. Devienne RADSYNCH17 21/04/17

10 2.1 Geometry constrains LOREA geometry: 1 side wall T (1.5 m normal concrete) Source 1 side wall S (thickness and 1 back wall B material to be defined Target 1 roof R by calculation) Target : Simplified LOREA Optical Hutch drawing 2° inclined Mirror M1 (Copper) Pipes : Diameter 70 mm LOREA Optical Hutch FLUKA 2D top view A. Devienne RADSYNCH17 21/04/17

11 2.2 Sources Gas Bremsstrahlung : Electromagnetic cascade produced • Source of by the interaction of the e- beam with the residual gas radiation inside the vacuum chamber. It depend on the Current Intensity (mA), the e- Energy (3GeV), the pressure and composition inside the vacuum chamber Insertion Device Undulator : Radiation depends on the Undulator parameters and directly proportional to the current intensity (mA). A. Devienne RADSYNCH17 21/04/17

2.3 Define FLUKA cards 12 2.3 FLUKA Code Some FLUKA parameters (cards) of the simulations: • DEFAULTS: PRECISION • PHOTONUC: Activate photonuclear interaction • EMFCUT: Energy threshold production: 1 keV for photon and 100 keV for e- e+ • BIASING: no biasing card used A. Devienne RADSYNCH17 21/04/17

13 2.3 FLUKA Code a) Gas Bremsstrahlung source Beam: Electron 3 GeV Target: Residual gas inside a 8.62 m length straight section Average 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) Relative Molecule pressure (%) H 2 80 Electron beam CO 10 CO 2 5 Noble gas 3 H 2 O 2 A. Devienne RADSYNCH17 21/04/17

14 2.3 FLUKA Code a) Gas Bremsstrahlung source: 1e+08  The flux obtained is considered as source for the LOREA shielding calculations 1 keV 1 GeV Photon flux (photons/s) for 400 mA e- beam, scored with USRBDX card at the end of the Storage Ring straight section A. Devienne RADSYNCH17 21/04/17

15 2.3 FLUKA Code b) Insertion Device source Use of hsource.f sub routine 1.E+16 to read histogram and use as a Flux (Ph/s/0.1%BW) 1.E+13 souce for the Shielding 1.E+10 1.E+07 Calculation with the BL 1st 1.E+04 Mirror as main Target 1.E+01 1.E-02 1.E-05 1.E-08 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 Energy (eV) Maximum ID photon flux for each Undulator energy range (analytic calculations by ALBA Accelerator division) 15 Apple II LOREA Undulator A. Devienne RADSYNCH17 21/04/17

16 3. Results A. Devienne RADSYNCH17 21/04/17

3. Results 17 3.1 Shieling elements • Optical Hutch Shielding thicknesses and material for the LOREA Corresponding vacuum in straight optics hutch wall and roof (mm) section for 0.5 μSv/h (mbar) Wall S (side wall) 2.5 × 10 -8 20 mm lead + 50 mm polyethylene Roof 2.5 × 10 -8 15 mm lead Wall B (back wall) 60 mm of lead 5.0 × 10 -8 + 50 mm of lead in central 1 m 2 + 105 mm of lead Opt-to-Exp guillotine + 50 mm of lead local screen behind mirror + 20 mm other white beam scattering source A. Devienne RADSYNCH17 21/04/17

18 3.1 Shielding elements • Local shielding elements # Shielding Elements Height Width Thickness Material (cm) (cm) (cm) 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 Dimensions defined by 6 OH backwall central reinforcement 100 100 5 Pb basic ray tracing • Beamstops and collimators # 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 Reduction of a factor 15 of the scattered bremsstrahlung radiation escaping from the Optical Hutch through the beampipe A. Devienne RADSYNCH17 21/04/17

19 3.2 Dose maps a) Gas Bremsstrahlung source case equivalent dose rate maps (DOSE-EQ) - horizontal view at beam level - Doble collimation system Beamstop Photon dose rate map (in µSv/h) 0.5µSv/h Lead screen Total dose rate map (in µSv/h) from scattered bremsstrahlung with real LOREA geometry and shielding Neutron dose rate map (in µSv/h) A. Devienne RADSYNCH17 21/04/17

3.2 Dose maps 20 a) Gas Bremsstrahlung source equivalent dose rate (DOSE-EQ) Back wall (S) Side wall (S) 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 A. Devienne RADSYNCH17 21/04/17

21 3.2 Dose maps a) Gas Bremsstrahlung source case equivalent dose rate maps (DOSE-EQ) - transversal view at beam level - 0.5µSv/h Total dose rate map (in µSv/h) from Dose rate profile (in µSv/h) from scattered scattered bremsstrahlung with real LOREA bremsstrahlung outside LOREA Roof (R) as a geometry and shielding function of the distance along the roof (red curve: photon dose rate; green curve: neutron dose rate; blue curve: total dose rate) A. Devienne RADSYNCH17 21/04/17

22 3.2 Dose maps b) ID Undulator dose rate maps (at 400 mA): Total dose rate map (in µSv/h) from ID Undulator source  Shielding requirements for scattered synchrotron radiation are largely met by the shielding thicknesses required for scattered bremsstrahlung . A. Devienne RADSYNCH17 21/04/17

23 3.2 Dose maps • Comparison with experimental data from ALBA beamlines 0.5 µSv/h Inside BL Gamma dose rate map (in µSv/h) from scattered bremsstrahlung at LOREA at Outside BL 400 mA Gamma dose rate measurements at BOREAS BL compared with storage ring current and FE state  Results obtained with FLUKA are in agreement with experimental data (Ionizating chamber FHT192) from a similar Beamline at ALBA ( few µSv/h current inside the Optical Hutch - proportional to the electron beam - and background reading outside) A. Devienne RADSYNCH17 21/04/17

24 4. Open points & conclusion A. Devienne RADSYNCH17 21/04/17

25 4.1 Open points 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 into 48 inputs (now integrated in Flair) … (vs. Manpower)  use of biaising (in particular playing with importance inside the shielding element) could allow better statistic in regions of interest,  Use of 2-steps simulations using intermediate results A. Devienne RADSYNCH17 21/04/17