Superconductive Radiation Space Shielding

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Superconductive Radiation Space Shielding for Exploration Missions R. Battiston INFN-TIFPA and University of Trento Italian Space Agency COSPAR 2014 Moscow Friday 15 August 14

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Transcript of Superconductive Radiation Space Shielding

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Superconductive Radiation Space

Shieldingfor Exploration Missions

R. BattistonINFN-TIFPA and University of Trento

Italian Space Agency

COSPAR 2014 Moscow

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The Consortium

SPA 2012 2.2.02 Key technologies for in-space activities

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FP7  SR2S  program  (2013-­‐15)

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Radia7on  effects  on  biological  7ssues  

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The  interplanetary  travel  case

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•          The  evidence  for  cancer  risks  from  humans  who  are  exposed  to  low-­‐LET  radia:on  is  extensive  for  doses  above  100  mSv  (10  rem).

•          The  doses  that  are  to  be  expected  on  space  missions,  as  well  as    the  nuclear  type  and  energies,  are  quite  well  understood.  

•          The  main  contribu:on    to  the    ionizing  radia:on  encountered  in  space    are  

• Solar  Par:cle  Events    (SPE)• Galac:c  Cosmic  Rays    (GCR)•  

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Distribu=on  of  energies  of  GCR.  This  is  a  graph  of  the  more  abundant  nuclear  species    in  CR  as  measured  near    Earth.  Below  a  few  GeV/nucleon  these  spectra  are  strongly  influenced  by  the  Sun.  The  different  curves  for  the  same  species  represent  measurement  extremes  resul=ng  from  varying  solar  ac=vity  (Physics  Today,  Oct.  1974,  p.  25)  

Par=cle  spectra  observed  in  SPE  compared  with  the  GCR    spectrum

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Galac7c  cosmic  radia7on

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%  of  death  due  to  cancer  -­‐  95%  CL

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Durante  &  CucinoUa,  Nat.  2008

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Doses  for  explora7on  missions.....

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• FREE  SPACE:    equivalent    doses  in  excess  of  1.2  Sv  /yr  (∼120  rem/yr)  

• SPACECRAFT  (thin)  SHIELDING:  about    700-­‐800  mSv/yr  (70-­‐80  rem/yr)

• ON  THE    MARS  SURFACE:  between  100  and  200  mSv/yr  (10  and  20    rem/yr),  depending  on  the  loca:on    

• ON  THE    MOON  SURFACE  :  223  mSv/yr  (22,3  rem/yr)    with  oscilla:ons  of  ±  10  rem/yr    as  a  func:on  of  solar  ac:vity  

–for  comparison:    ISS  about  18  rem/yr      -­‐-­‐>    6  month  expedi7ons

•  

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Projec7on  of  risk  of    radia7on  on  

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95%  CL

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3%  REID  limit  =>increase  of  P(cancer  death)  

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Mars  Mission  1000  days  in  space  

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SR2S  mission  scenarios  

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SR2S  mission  scenarios  

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Shield  in  space  if  it  is    “thin”  ...           .......then  it  “adds”  dose

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Shield  in  space  if  it  is    “thin”  ...           .......then  it  “adds”  dose

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Shield  in  space  if  it  is    “thin”  ...           .......then  it  “adds”  dose

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Spacecrafts structures 2 - 6 cm Al eq

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Advanced  materials  can  help  SPE  not  GCR

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Advanced  materials  can  help  SPE  not  GCR

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Spacecrafts structures 2 - 6 cm Al eq

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 So  we  turn  to  ac7ve  radia7on  shields

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Ac7ve  magne7c  shielding  

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Magne7c  shield  configura7ons

• The  angular  deflec:on  in  the  magne:c  field  may  be  compared  to  the  kine:c  energy  lost  by  ioniza:on,  where  BL  replace  the  electromagne:c  and  nuclear  radia:on  length  to  characterizing  the  shielding  performance  of  the  material

• Unconfined  Field  (e.g.  Earth’s  field),  very  large  volume  (L),  lower  field  strength  (B)  

• Confined  field:  small  volume  (L),  higher  field  (B)  and  larger  mass

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The  ATLAS  superconduc7ng  toroid

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Previous  Monte  Carlo  Studies

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Ac7ve  magne7c  shielding  

• Principle  of  opera=on

• B    field  tangent  to  the  shielded    volume  bends  par7cle  away

• 1)  toroidal  B  field,  orthogonal  to  Hab  axis

• 2)  solenoidal  B  field,  parallel  to  Hab  axis

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1)  TOROIDAL-­‐ORTHOGONAL  FIELD

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eg.  racetrackstoroid

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...but  also

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double  helix donut

double  handle

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2)  SOLENOIDAL-­‐PARALLEL  FIELD

eg.  coaxial  solenoids

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...but  also

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mul:solenoid axial  mul:donut

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Shielding  power  :    ∫BdL

Re

Ri

For  an  ideal  toroid,  the  shielding  power  is  defined  as

-­‐-­‐>  large  radius-­‐-­‐>  large  B  we  would  reach  effec:ve  

shielding  with  ∫BdL≈15  Tm

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Magnet  mechanical  structure

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•                              •                  P(Pa)  =  B2/  2μo  (T2)

Toroidal field !B non uniform! 1-large inward pressure !structural mass

2-low leakage field

Solenoidal    field  !  B  is  uniform  !1-­‐large  outward  forces

2-­‐large  leakage  field!  compensaNon  coil

Avoid  stresses  on  superconducNng  cable    !coil  support  

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SRS2  tradeoff  -­‐>  racetrack  toroid  system

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Magnet  mechanical  structure

•  Magnet  design  iteraNons  in  SR2S  

•  Structure  design  opNmizaNon:

–minimize  the  material  traversed  by  GCR  to  avoid  secondary  producNon

–maximize  the  BdL  to  deflect  away    Z<3  parNcles

–exploit  the  passive  material  to  absorb    Z>2  parNcles  (stopping  power)

•  Perform  Monte  Carlo  calculaNons  of  the  dose  reducNon  factor  for  GCR  and  SPE

•  Improve  the  use  advanced  materials  and  mechanical  soluNons  to  reduce  mass.    

•  Current  design  configuraNon:  BdL  ≈  8  Tm  

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Superconduc7ng  cable  for  space  applica7ons

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Superconductors  for  space  

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Columbus  cable  for  SPACE  applica7ons

FROM  17  TO  10.2  grams,  

40%  weight  reducNon

FROM:

3x0,5  nickel  clad  wire

3x0,2  copper  stabiliza:on

TO:

3x0,5  :tanium  clad  wire

3x0,5  alluminium  stabiliza:on

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Example  of  mass  op7miza7on

First  Design:•24  Coils     !  High  loads  on  the  racetrack

! Concentrated  Loads  on  the  Tube   " ! High  Local  DeformaNon   ! More  sensiNve  at  mechanical              tolerance

Smart

 

SoluNo

n

New  Design:•  120  coils     ! Lower  loads  on  the  racetrack

!  Loads  uniformly  distributed                              on  the  tube             ! Lower  DeformaNon   ! Less  SensiNve  at  mechanical                              tolerance

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Analy7cal  and  Monte  Carlo  analyses

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See    M.  Giraudo  talks  

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Magne7c  shielding  of  a  SPE  event

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• The  Columbus  habitat  was  surrounded  by  the  full  model  already  used  in  the  past,  without  considering  hydrogen  and  endcaps

• The  density  of  every  component  was  reduced:– 0%  of  the  total  

– 25%  of  the  total  

– 50%  of  the  total  

– 75%  of  the  total  

– Total  (around  315  tons)

Simula:on  varying  the  mass    -­‐  M.  Giraudo,  M.  Vuolo

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• Par:cles  were  generated  on  a  cylinder  around  the  habitat  !  No  evalua:on  of  the  radia:on  shielding  at  the  endcaps:– For  this  reason,  the  obtained  dose  values  are  valid  only  to  perform  a  comparison  between  the  different  studied  configura:ons,  they  are  not  absolute  values  of  dose  per  event  in  space.

Source  

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• Various  components  of  the  primary  radia:on  field  in  space  par:ally  absorbed  in  the  walls  of  the  spacecrai

• Secondary  radia:on  produced  by  scajering  and  reac:ons  of  the  primary  radia:on  in  the  walls  and  other  materials  within  the  spacecrai

• GCR:  about  90%  hydrogen  nuclei;  9%  alpha  par:cles  and  1%  are  the  nuclei  of  heavier  elements

High  energy  protons  and  neutrons:

• Knockout  and  spalla:on  reac:on– Built-­‐up  of  light  par:cles  and  heavy  ion  target  fragments  with  high  LET  

and  low  ranges.  

About  radia:on  field  inside  the  spacecrai

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HZE:  predominant  processes  in  their  penetra:on  through  majer  are  energy  loss  through  atomic  and  molecular  collisions,  and  absorpNon  and  parNcle  producNon  from  nuclear  interacNons  with  spacecrai  materials  and  :ssues•E>100  MeV/u  dominant  reac:on  mode:  fragmenta:on

– Nuclear  absorp:on  cross  sec:on      ̴  A1/3

•E<100  MeV/u  dominant  reac:on  modes:  elas:c  scajering,  compound  nucleus  forma:on,  and  excita:ons  of  discrete  nuclear  levels  that  decay  by  gamma  emission  or  par:cle  emission  

•Transport  of  HZE  highly  modulated  by  nuclear  reac:ons  in  passing  through  majer

HZE

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• In  case  of  thick  shielding  important  source  of  dose

• Low-­‐energy  neutrons  from  evapora:on  processes  where  a  neutron  is  boiled  off  from  the  nucleus  because  it  contains  an  excess  of  energy  from  its  last  interac:on

• High  energy  neutrons  from  high-­‐energy  collisions  (ten’s  of  GeV/nucleon)  where  the  result  of  the  interac:on  is  a  spray  of  nuclear  fragments  and  par:cles

• H  approximately  the  same  mass  as  the  neutron  !  the  best  neutron-­‐scajering  medium  available– The  hydrogen-­‐bearing  materials  reduce  the  number  of  higher  energy  

neutrons  in  the  500  keV  to  20  MeV  energy  range  that  penetrate  the  shield  materials  considered.  In  fact,  the  more  hydrogen,  the  bejer  the  overall  shielding  characteris:cs.

Neutrons

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Preliminary  Results  Varying  Mass:  Protons  +  He    GCRAll  doses  presented  are  EffecNve  sex  averaged  doses  according  ICRP123  

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FIELD  ON

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Preliminary  Results  Varying  Mass:  Protons  +  He    GCRAll  doses  presented  are  EffecNve  sex  averaged  doses  according  ICRP123

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FIELD  OFF

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Preliminary  Results  Varying  Mass:  Ions  (z=3  to  26)  GCRAll  doses  presented  are  EffecNve  sex  averaged  doses  according  ICRP123

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FIELD  ON

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Preliminary  Results  Varying  Mass:  Ions  (z=3  to  26)  GCRAll  doses  presented  are  EffecNve  sex  averaged  doses  according  ICRP123

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FIELD  OFF

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Preliminary  Results  Varying  Mass:  TOTAL  dose  

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Normaliza:on  extended  to  all  the  solid  angle.  Note  that  we  are  genera:ng  par:cles  from  a  lateral  source.  In  this  preliminary  analysis  we  are  not  considering  ‘endcaps  effect’!

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Dose  Eq.  Results

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• Carbon  Epoxy  cylinder  has  the  best  performance  in  reducing  the  number  of  secondary  neutrons

• The  effect  of  Boron  is  not  influen:al  on  the  results

• We  have  to  inves:gate  the  energy  distribu:on  of  neutrons  and  the  cross  sec:ons  for  the  simulated  configura:ons

Cross  sec:ons  comparison

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Energy  distribu:on  of  secondary  neutrons  dose

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Lin-­‐Log    scale

Negligible  contribuNon  below  100  KeV

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Cross  sec:ons  for  different  materials    ENDF-­‐VII  (n,Total)

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Considering  different  materials  configura:ons  :

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1. Carbon  Epoxy,  same  geometry  (No  Titanium)

• Pb  internal  cylinder                  (3  cm  thick  –  75  tons)

• All  Carbon  Epoxy  (Coils  and  structures)

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Material  componentMaterial  componentMaterial  componentMaterial  component Other  featuresOther  featuresOther  features

ConfiguraNon COILS STRUCT.  1 STRUCT.  2 Solid  H2   Par:cle Field G4    Phisiscs  List

B4C/Al Coil  Eq.  Mat   Titanium B4C/Al -­‐   H OFF QBBC

C  Epoxy   Coil  Eq.  Mat   Titanium C  Epoxy   -­‐   H OFF QBBC

C  Epoxy  HP Coil  Eq.  Mat   Titanium C  Epoxy   -­‐   H OFF QGSP_BERT_HP

No  Mat Coil  Eq.  Mat   Titanium -­‐ -­‐   H OFF QBBC

Lead Coil  Eq.  Mat   Titanium Lead -­‐   H OFF QBBC

All  Carbon Carbon  Epoxy Carbon  Epoxy Carbon  Epoxy -­‐   H OFF QBBC

Carbon_NoTi Coil  Eq.  Mat   Carbon  Epoxy Carbon  Epoxy -­‐   H OFF QBBC

Hydro+B4C/Al Coil  Eq.  Mat   Titanium B4C/Al 10  tons   H OFF QBBC

Hydro+B4C/Al+Field Coil  Eq.  Mat   Titanium B4C/Al 10  tons   H ON QBBC

C  Epoxy    Field  (H) Coil  Eq.  Mat   Titanium C  Epoxy   -­‐   H ON QBBC

C  Epoxy    Field  (H+He) Coil  Eq.  Mat   Titanium C  Epoxy   -­‐   H+He ON QBBC

C  Epoxy    Field  x2  (H+He) Coil  Eq.  Mat   Titanium C  Epoxy   -­‐   H+He ON  (double) QBBC

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STRUCT.  1

Solid  H2

STRUCT.  2

COILS

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Effec:ve  Doses:  All  Configura:ons

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Freespace  H,  normalized  on  the  lateral  region  (47%  of  total  solid  angle)

Field  Off

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Conclusions  (1)

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•The  SR2S  project  brings  one  of  the  most  challenging  magnet  systems  to  be  built

•Various  of  the  technologies  for  such  a  space  superconduc:ng  system  do  not  exist  yet

•SR2S  is  an  extraordinary  technology  development  field  and  technology  driver

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Conclusions  (2)

•Ac:ve  Radia:on  Shielding  for  explora:on  is  a  necessity

•Passive  shielding  for  GCR  is  not  adequate  and  for  SPE  can  only  protect  limited  volumes  

•Ac:ve  magne:c  shielding  becomes  effec:ve  at  high    ∫  BdL  values  and    only  if  the  material  thickness  traversed  by  the  GCR  is  “small”

•Interplay  between  ac:ve  and  passive  shielding  is  complex  and  detailed  simula:ons  are  needed  to  understand  it

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Conclusions  (3)•Op:miza:on  of  magne:c  and  structural  forces    is  mandatory

•During  the  first  year  SR2S  has  developed  the  basic  tools  for  ac:ve  shield  analysis,  started  a  sistema:c  inves:ga:on  and  achieved  important  technological  developments

•We  are  analyzing  a  toroidal  configura:on:      other  magne:c  configura:ons  would  also    deserve  careful  study  

•A  R&D  path  towards  future  developments  for  light,  high  field,  modular  toroidal  shield  design  has  been  iden:fied

•Collabora:on  and  synergy    with    NASA,  ESA  and  EU  56

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• In  order  to  reduce  neutron  contribu:on  we  must  consider  genera:on  and  absorb:on  of  n  in  different  materials

• Heavy  materials  as  lead  (Pb)  have  a  large  absorb:on  cross  sec:on  but  in  case  of    high  energy  protons  (GCR)  they  produce  more  neutrons  (large  secondaries  genera:on).  GeneraNon  >  AbsorbNon

• Boron  rich  materials  are  efficient  neutron  absorber  only  in  the  low  energy  region  where  dose  contribu:on  is  negligible.

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Conclusions  (4)

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• Using  Carbon  Epoxy  in  place  of  Titanium  reduces  significantly  the  neutron  produc:on  but  increases  protons  contribu:on.  

• The  magne:c  field  is  off  in  this  configura:on  and  proton  contribu:on  may  be  decreased  by  the  field.  

• The  choice  of  structural  materials  is  fundamental

• Materials  and  field  must  work  in  synergy  in  order  to  improve  the  dose  reduc:on  avoiding  secondaries  produc:on  

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Conclusions  (5)

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Thank you !

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SC  cables

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