activation and "hands-on" maintenance criteria for heavy-ion accelerators

Ivan Strašík ● Activation and "Hands-On" Maintenance Criteria for Heavy-Ion Accelerators ● SATIF10

Activation and "Hands-On" Maintenance Criteria for Heavy-Ion Accelerators

I. Strašík1,2, E. Mustafin1, M. Pavlovič3, N. Sobolevskiy4, V. Chetvertkova1,2

1GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany2Johann Wolfgang Goethe Universität Frankfurt am Main, Germany3Slovak University of Technology in Bratislava, Slovakia4Institute for Nuclear Research of the Russian Academy of Sciences, Moscow,

Russia

1


Motivation

The activation of accelerator structures due to beam-losses is an important issue for existing (LHC, SNS, RHIC, …) and planned (FAIR) hadron facilities.

Quantification of residual activity induced by lost particles is necessary to evaluate radiation hazard to personnel during “hands-on” maintenance.

Activation studies of the AccPhy group at GSI Darmstadt.• Irradiation experiments with heavy ions.• Monte Carlo simulations (FLUKA, SHIELD, MARS, GEANT4).

• Validation of the simulation codes.• Activation of various accelerator components.

• General – beam pipe, bulky targets.• Specific – slow-extraction area of the SIS100 synchrotron.

• Tolerable beam-loss criteria for “hands-on” maintenance on heavy ion accelerators.

2


Experimental studies of the residual activity

2003: target materials: stainless steel, copper beam: 12C beam energies: 200, 300 and 400 MeV/u [1] A. Fertman et al, GSI-Acc-Note-2003-07-001, (2003)

2005 – 2006: target materials: stainless steel, copper beam: 238U beam energies: 120, 500 and 950 MeV/u [2] A. Fertman et al, Nucl. Instr. and Meth. in Phys. Res. B Vol. 260 (2007) [3] I. Strašík et al., Nucl. Instr. and Meth. in Phys. Res. B Vol. 266, (2008)

2009: target material: copper, alluminium beam: 40Ar beam energies: 500 MeV/u and 1 GeV/u [4] I Strašík et al., Nucl. Instr. and Meth. in Phys. Res. B Vol. 268, (2010) [5] V Chetvertkova et al., to be submitted in Nucl. Instr. and Meth. in Phys. Res. B

2010: target material: alluminium beam: 238U beam energies: 500 MeV/u and 950 MeV/u [6] V. Chetvertkova et al., to be submitted in Nucl. Instr. and Meth. in Phys. Res. B

2008: target material: stainless steel beam: 238U beam energy: 1 GeV/u [7] I. Strašík et al., Proceedings of HIAT09 Conferrence, (2009)

3


Validation of the simulation codes

AE – experimentally measured activityAS – activity calculated by simulation codes

target material: stainless steelbeam: 238Ubeam energy: 950 MeV/usimulation codes: FLUKA, SHIELDcooling time: 3 days

0.0

1 0.1

4

0.0

2 0.0

9

0.1

5 0.2

9

0.1

8

0.0

2

0.0

1

0.0

0

0.0

4

0.0

2

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

2

0.1

1

10

7-B

e

44

m-S

c

46

-Sc

47

-Sc

48

-V

51

-Cr

52

-Mn

54

-Mn

56

-Co

57

-Co

57

-Ni

58

-Co

99

-Mo

10

3-R

u

12

1-T

e

12

6-S

b

12

7-X

e

13

1-B

a

13

1-I

13

9-C

e

14

1-C

e

14

6-G

d

14

9-G

d

16

9-Y

b

20

6-B

i

23

7-U

Isotope

Ra

tio A

E/A

S

0

2

Ratio Experiment/FLUKARatio Experiment/SHIELDRelative Activity

individual isotopesdepth profiles

total activity of all isotopes ratio Experiment/FLUKA = 1.09 (u = 0.1 %)

ratio Experiment/SHIELD = 0.66 (u = 0.5 %)

0E+00

1E-09

2E-09

3E-09

4E-09

5E-09

6E-09

7E-09

0 20 40 60 80 100 120 140Depth [mm]

Act

ivity

[Bq/

mm

/ion]

ExperimentSimulation (FLUKA)

Range

52Mn

4


Criterion for the proton accelerators of 1 W/m

"One important outcome of this workshop is the agreement that an average beam loss of 1 W/m in the uncontrolled area should be a reasonable limit for hands-on maintenance." (page 3 in workshop proceedings)

BEAM HALO AND SCRAPINGThe 7th ICFA Mini-workshop on High Intensity High Brightness Hadron Beams

Wisconsin, USA, September 13-15, 1999

0 200 400 600 800 1000

-400

-200

0

200

400

X [c

m]

Z [cm]

0.0

0.1

0.3

1.0

3.2mSv/h

-400 -200 0 200 400

-400

-200

0

200

400

Y [c

m]

X [cm]

0.0

0.1

0.3

1.0

3.2mSv/h

effective dose-rate at the distance 30 cm from the beam-pipe: ~1 mSv/h

beam: 1 GeV protonsbeam-pipe material: stainless steelbeam-losses: 1 W/m

beam-pipe wall thickness: 2 mmbeam-pipe length: 10 mbeam-pipe diameter: 10 cmangle of incidence: 1 mrad

irradiation time: 100 dayscooling time: 4 hourssimulation code: FLUKA

1 W/m ~ 6.2 × 109 protons/m/s at 1 GeV

5


Residual activity induced by heavy ions

primary beam: 1H, 4He, 12C, 20Ne, 40Ar, 84Kr, 132Xe, 197Au, 238Ubeam energy: 200 MeV/u – 1 GeV/ubeam-pipe material: stainless steelbeam-losses: 1 W/m beam-pipe wall thickness: 2 mmbeam-pipe length: 10 mbeam-pipe diameter: 10 cmangle of incidence: 1 mrad

irradiation time: 100 dayscooling times: 0 days, 4 hours,1 day, 1 week, 2 months, 1 year, 10 yearssimulation code: FLUKA, SHIELDcalculated quantities: activity [Bq], effective dose-rate [mSv/h]

6


Isotope inventory and their relative activities

cooling time: 1 day

Isotope inventory and their relative activities do not depend on the projectile species.

0

10

20

30

40

51Cr 48V 52Mn 54Mn 49V 55Fe 58Co 56Co

Induced isotopes

Rel

ativ

e ac

tivity

[%] 1H 4He 12C

20Ne 40Ar 84Kr

132Xe 197Au 238U

51Cr 48V 52Mn 54Mn 49V 55Fe 58Co 56Co

1H 4He 12C20Ne

238U

40Ar 84Kr132Xe 197Au

Projectiles

simulation code: FLUKA beam energy: 500 MeV/u

7


Time evolution of the induced activity

0 100 200 300 4000.0

0.2

0.4

0.6

0.8

1.0

1H 4He12C 20Ne40Ar 84Kr132Xe 197Au

238U GC

At/A

eoi

Time [days]At – total activity at given time (t)

Aeoi – total activity immediately after irradiation (eoi)

GC – generic curve

8

The time-evolution of the activity can be described by means of a generic curve.



Dependence of the activity on beam parameters

0 50 100 150 200 250105

106

107

108

109

1010

1011

0 days 1 day 1 week 2 months 1 year 10 years

Primary ion mass number

Act

ivity

[B

q]

1 GeV/u

0 50 100 150 200 250105

106

107

108

109

1010

1011

0 days 1 day 1 week 2 months 1 year 10 years


Act

ivity

[B

q]

200 MeV/u

Activity induced in the beam pipe by 1 W/m of primary beam-losses calculated with FLUKA.

1. Activity is decreasing with increasing primary-ion mass.2. Activity is decreasing with decreasing primary-ion energy.

9


Probability of the nuclear interaction

0

200

400

600

800

1000

0 10 20 30 40 50 60Path length [cm]

Kin

etic

ene

rgy

[MeV

]

Mean free path

protons

Range0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5Path length [cm]

Kin

etic

ene

rgy

[MeV

/u]

Mean free path

Range

238U ions

SRIM

• Range

• Mean free path[1] S. Kox et.al., Physics Letters B Vol. 159.

stainless steel

• Material

10


“Hands-on” maintenance criteria for heavy ions

1) Inventory of the isotopes does not depend on the projectile species.

2) Time evolution of the activity correlates to the generic curve.

3) The activity induced by 1 W/m of beam losses is decreasing with increasing ion mass and with decreasing energy.

Ap(1GeV) – normalized activity induced by 1 GeV proton beam (reference)Ai(E) – normalized activity induced by the beam of interest at given energy

the normalized activity [Bq/W/m]

0 50 100 150 200 2500

10

20

30

40

50

60

70

80 200 MeV/u 300 MeV/u 400 MeV/u 500 MeV/u 600 MeV/u 700 MeV/u 800 MeV/u 900 MeV/u 1 GeV/u

Ap(1

Ge

V)/

Ai(E

)

Primary ion mass number0 50 100 150 200 250

0

10

20

30

40

50

60

70

80 200 MeV/u 300 MeV/u 400 MeV/u 500 MeV/u

700 MeV/u

1 GeV/u

Ap(1

Ge

V)/

Ai(E

)


FLUKA SHIELD

11


Activation of bulky accelerator-structures

Besides the beam pipe, accelerators contain also bulky structures like a magnet yoke or a coil.

Activation of the bulky target (cylinder)

diameter: 20 cm, length: 60 cm

material: copper, stainless steel

irradiation time: 3 months

primary beams: 1H, 4He, 12C, 20Ne, 40Ar, 84Kr, 132Xe, 197Au, 238U

beam energies: 200 MeV/u – 1 GeV/u

irradiation time: 3 monthscooling times: 0 days, 4 hours, 1 day, 1 week, 2 months, 1 year, 10 yearssimulation code: FLUKA, SHIELDcalculated quantities: activity [Bq]

The calculated activities were normalized to the unit beam-power of 1 W delivered continuously to the target.

12


0

10

20

30

40

51Cr 48V 52Mn 54Mn 58Co 55Fe 49V 56Co

Induced isotopes

Re

lativ

e a

ctiv

ity [%

]

1H 4He 12C

20Ne 40Ar 84Kr

132Xe 197Au 238U

51Cr 48V 52Mn 54Mn 58Co 55Fe 49V 56Co

1H 4He 12C20Ne

238U


stainless steel

Projectiles

0

10

20

30

40

64Cu 58Co 51Cr 57Co 56Co 48V 54Mn 52Mn

Induced isotopes

Re

lativ

e a

ctiv

ity [%

]

1H 4He 12C

20Ne 40Ar 84Kr

132Xe 197Au 238U

64Cu 58Co 51Cr 57Co 56Co 48V 54Mn 52Mn

1H 4He 12C20Ne

238U


copper

Projectiles

cooling time: 1 day

Isotope inventory induced in the bulky targets and their relative activities depend on the target material.

Isotope inventory induced in various materials

13



0 50 100 150 200 2500

10

20

30

40

50


Ap(1

GeV

)/A

i(E)


stainless steel

0 50 100 150 200 2500

10

20

30

40

50


Ap(1

GeV

)/A

i(E)


copper

Ap(1GeV) – normalized activity induced by 1 GeV proton beamAi(E) - normalized activity induced by the beam of interest at given energy

“Hands-on” maintenance criteria for the bulky targets

14

simulation code: FLUKA


Dependence of the criteria on the target parameters

• Induced activity depends on the robustness of the target.

• The criteria for heavy ions are less strict for the beam pipe than for the bulky target.

Ap(1GeV) – the normalized activity induced by 1 GeV proton beamAi(1GeV/u) – the normalized activity induced by the beam of interest at energy 1GeV/u

0 50 100 150 200 2500

5

10

15 beam pipe (2 mm wall thickness) beam pipe (20 mm wall thickness) bulky target

Ap(1

GeV

)/A

i(1G

eV/u

)


• Heavy-ion reactions involves projectile break-up and emission of secondary nucleons from the projectile. [1] M. Maiti et al., Nucl. Instr. and Meth. in Phys. Res. A 556.

[2] U. Brosa and W. Krone, Physics Letters B 105.

• The break-up nucleons with high final energy do not undergo much interaction with the target nuclei and fly away at very forward angles.[3] A. Bonaccorso and D.M. Brink, Physical Review C 57.

• This allows them to escape from the thin-wall beam-pipe which lowers the activation level.

15


Angular distribution of the escaping nucleons

0 5 10 15 20 25 30 35 40 450

1x1010

2x1010

3x1010

4x1010

1H 4He 12C

20Ne 40Ar 84Kr

132Xe 197Au 238U

Nuc

leon

yie

ld [n

ucle

on/(

Wsr

)]

Nucleon angle [degree]

wall thickness: 2 mm

0 5 10 15 20 25 30 35 40 450

1x1010

2x1010

3x1010

4x1010

1H 4He 12C

20Ne 40Ar 84Kr

132Xe 197Au 238U

Nuc

leon

yie

ld [n

ucle

on/(

Wsr

)]

Nucleon angle [degree]

wall thickness: 20 mm

Angular distribution of nucleons escaping from the beam pipe for wall thickness of 2 mm and 20 mm calculated with FLUKA.

The angles are given with respect to the beam-pipe longitudinal central axis.

Contribution to the escaped particles to the beam-pipe activation is missing and the induced activity is lower than in case of the bulky target.

16


Conclusions

Tolerable beam-loss criteria for “hands-on” maintenance on heavy-ion accelerators were specified for the beam-pipe and the bulky-target geometry.

The tolerable beam losses for heavy ion accelerators were specified by scaling the existing value of 1 W/m for protons.

The criteria for uranium beam are 12 W/m at 1 GeV/u in case of the beam-pipe geometry.

The criteria for the bulky accelerator structures are more strict – 5 W/m at 1 GeV/u uranium beam.

The criteria calculated by FLUKA and SHIELD are in good agreement except the beam energy 200 MeV/u.

The thin-wall beam-pipe exhibits significant leakage of the heavy-ion projectiles’ break-up nucleons from the wall, which decreases the induced activity.

17


Thank you for your attention

activation and "hands-on" maintenance criteria for heavy-ion accelerators

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