Transcript Document

Neutron induced light-ion production
at 175 MeV
@ The Svedberg Laboratory, Uppsala
Svenskt Kärnfysikermöte XXVIII
KTH-AlbaNova, Stockholm, 12 November, 2008
Riccardo Bevilacqua
Department of Physics and Astronomy
Division of Applied Nuclear Physics
Uppsala University
The NEXT project
Neutron data Experiments for Transmutation
supported as a research task agreement by
• Statens Kärnkraftinspektion (SKI)
Swedish Nuclear Power Inspectorate
• Svensk Kärnbränslehantering AB (SKB)
Swedish Nuclear Fuel and Waste Management Co
• Ringhalsverket AB
70% Vattenfall + 30% E.ON
Ringhals Nuclear Power Plant
largest power plant in Scandinavia
started 2006-07-01
Background
(for neutron induced cross sections at 175 MeV)
• High-energy neutron applications:
– Medical (e.g., C, O)
• Cancer therapy with fast neutrons and protons
• Dose estimation
– Electronics (e.g., Si)
• Single Event Effect caused by cosmic-ray neutrons
– Accelerator Driven System (ADS) (e.g., Fe, Pb, U)
– Benchmark of Nuclear Reaction Models
Cosmic-rays
Silicon
Chip
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Neutron induced cross sections
& transmutation techniques in ADS
In a spallator coupled to a core: neutrons up to 1 GeV
Present nuclear data libraries: up to 20 MeV
Direct reactions models:
work reasonably well above 200 MeV
NEA nuclear science committee (A.J.Koning et al. 1998)
high priority for transmutation applications
cross section measurament of the (n,xp) reaction
in the range 20 – 200 MeV for 56Fe, 208Pb, 232Th, 238U...
Present status of light-ion production measurements:
lack of experimental data in the 100-200 MeV region
(< 100 MeV: Tohoku Univ. , LANL, Louvain-la-Neuve, Uppsala)
The current project
Extension of 96 MeV measurements using the new TSL
neutron facility @ Uppsala within the framework of an
international collaboration (Sweden – Thailand – Japan)
Double differential cross sections measurement at 175 MeV
• C(n,x) (experiment in 2007, analysis in progress)
• Fe(n,x) and Pb(n,x) (planned January 2009)
Comparison with theoretical model calculations
and high-energy nuclear data file
New neutron beam facility at
The Svedberg Laboratory (TSL), Uppsala
• Gustaf Warner Cyclotron
– Proton energy ~180 MeV
• Neutron source
– Li(p,n) reaction
– Quasi mono-energetic neutron source
– Neutron energy 11-175 MeV
Shielding and collinator were studied and
improved with use of MCNPX transport code
Experimental setup
• MEDLEY
– Detected light ions: p, d, t, 3He, α particle
– Composed 8 ΔE-ΔE-E telescope
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Angle: 20º -160º in step of 20º
ΔE detector: Si surface barrier semi-conductor detector
E detector: CsI(Tl) scintillator
Using ΔE-ΔE-E technique for particle identification
1000 μm
Experiment procedure
Neutron source
Li(p,n) reaction
Li target thickness: 23.5 [mm]
Proton beam energy: 178.7 [MeV]
Peak neutron energy: 174.3 [MeV]
Maximum proton beam current on target: 0.3 [μA]
Measurements
Target
Carbon (2007)
Iron (2007 and 2009)
Lead (2009)
CH2 (n-p scattering peak used to normalize cross sections)
Empty frame (background)
Particle identification
1000 μm
Improvement of particle identification
Thicker Si2 detector:
400-600 μm to 1000 μm
1000 μm
The LIONS (Light Ions) Club
Conversion to absolute cross section
1. Extract np elastic peak at 20º
Conversion to absolute cross section
2. Normalize
– CH2 (n-p scattering peak) data is used to normalize
the cross sections for C.
– NP cross section data from NN cross section
database (ref: http://gwdac.phys.gwu.edu)
C
NC
NN cross section database
Ref: http://gwdac.phys.gwu.edu
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 H 2M C tCH  CH CH
2
N H M CH 2 tC
2
C
2
C
N: Number of counts in the peak
M: Molecular mass
t: target thickness [mg/cm2]
Φ: relative neutron flux [n/cm2]
Ω: solid angle from target to telescope [sr]
Proton production from Carbon at 175 MeV
Masateru Hayashi,
private communication
(2008)Club
The LIONS
(Light Ions)
(Kyushu University, from April 2008 Mitsubishi electric Co.)
Summary
Measurament of double-differential cross section of
(n,x) reactions on C at 175 MeV was done 2007.
Additional iron shielding and thicker Si detectors
will improve particle identification and reduce
background.
New measuraments on Fe and Pb are planned for
January/February 2009.
The LIONS (Light Ions) Club
Aknoledgment
Masateru Hayashi, Kyushu University (Japan)
Stephan Pomp, Uppsala University (Sweden)
Vasily Simutkin, Uppsala University (Sweden)
Udomrat Tippawan, Chiang Mai University (Thailand)
Alexander Prokofiev, TSL Uppsala (Sweden)
The LIONS (Light Ions) Club
The LIONS (Light Ions) Club
The LIONS (Light Ions) Club
The LIONS (Light Ions) Club
Fast Neutron Therapy (1)
Advantage of Fast Neutrons:
high LET (Linear Energy Transfer) of the secondary particles created by
neutron interactions.
densely ionizing protons, alphas and heavy ion recoil products inflict a
significant number of DNA double strand breaks.
About 1.5 more double strand breaks (DSB) are observed after neutron
irradiation than after photon irradiation of equal dose (*)
(*) J. M. Cosset, M. Maher, and J. L. Habrand, "New particles in radiotherapy: an introduction“
Radiat. Environ. Biophys., vol. 34, pp. 37-39, 1995.
Fast Neutron Therapy (2)
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Typical survival curves for cells irradiated in 60Co and fast neutron beams under welloxygenerated (exposed to air) and anoxic conditions. RBE (relative biological effectivness) and
OER (oxygen enanchment ratio) values are given at the survival level illustrated (1 Gray = 100
rads) 60Co emits one electron with an energy of up to 315 keV and then two gamma rays with
energies of 1.17 and 1.33 MeV, respectively.
Single Event Effect
Neutron induced soft-errors in microelectronics
Cosmic-rays
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Silicon
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Single Event Effect (SEE) results stochastically from a
single interaction between a device and an ionising particle.
Neutrons, although not directly ionising, induce SEEs
through nuclear interactions with constituent ions of the
semiconductor lattice.
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ADS and Transmutation (1)
Transmutation aims at reducing the radiological impact
of actinides and fission products in the high-level waste
(HLW) by nuclear transformation of troublesome longlived nuclides in strong radiation fields.
The concept of accelerator-driven systems combines
a particle accelerator with a sub-critical core
ADS and Transmutation (2)
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TRU (Transuranics): actinides with a higher Z than that of uranium
MA: minor actinides
Proton beam 7Li target Proton beam Average Fraction of neutrons in the
Peak
energy
thickness current (µA) energy of
high-energy peak (%) neutron flux
(MeV)
(mm)
peak
(105 cm–2s–1)a
neutrons
(MeV)
Measured Calculated
24.68 ± 0.04
2
10
21.8
50
—
1.3
49.5 ± 0.2
4
10
46.5
39
36
2.9
97.9 ± 0.3
8.5
5
94.7
41
39
4.6
147.4 ± 0.6
23.5
0.6
142.7
55
40
2.1
aAt
the entrance of the beam line to the user area.
Flux measured with a monitor based on a thin-film breakdown
counter (TFBC), utilising neutron-induced fission of 238U with the
cross-section adopted as neutron flux standard
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(A. V. Prokofiev et al. Rad. Prot. Dos. 2007)
Quasi monoenergetic neutron
source
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(A. V. Prokofiev et al. Rad. Prot. Dos. 2007)
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1. External ion injection: The external ion source can be used with axial injection into the
cyclotron. An ECR source is used for a wide variety of ions (from alfa particles to Xenon).
2. The Cyclotron: Isochronous cyclotron for all particles except protons above 100 MeV. For
protons in the range 100-180 MeV the cyclotron works as a synchrocyclotron. Particles and
energies available.
3. Radiofrequency system: (System1 in figure) Two accelerating electrodes each covering an angle
from 72 degrees at centre to 42 degrees at max. radius. Possible to use between 12.25 and 24.5
MHz (on the orbit frequency of the ions and on harmonics 2, 3 and 4). Two modes of operation:
Fixed frequency (isochronous cyclotron) and Frequency Modulation (synchrocyclotron) Max.
accelerating voltage 50 kV in fixed frequency mode and 16 kV when used in FM mode over a
frequency band approx. 24-22 MHz. Max. power per system is 140 kW.
4. Vacuum system: Two large diffusion pumps with cryogenic baffles (and one smaller) combined
with two cryopanels in the cyclotron chamber, giving a vacuum of approx. 10 -7 mbar without gas
load from internal ion source and 10-6 mbar with internal ion source.
5. QA1 and QA2 (Quadrupole magnets for focussing of the beam)
6. Internal Ion Source: Internal Penning Ionization sources are used for protons and some light
ions (deuterons, alfa particles).
7. Sond 1: Measure the beam current.
8. Collimator: Used to reduce the beam size and the beam current.
9. BMA1 This bending magnet can switch the beam between the a-line and the b-line.
Main data of the Gustaf Werner Cyclotron
Single pole with three sectors for vertical focussing
Pole base diameter 2.8 m
Pole gap hill-hill 0.2 m, valley-valley 0.362 m
Magnet yoke (iron) weight 600 tons
Copper coil weight 50 tons, power consumption max. 300 kW
13 sets of radial gradient field correction coils and two sets of harmonic correction coils
Max. average field 1.75 T at a max. useful radius of 1.2 m
Bending limit K= 192 Q2/A MeV
Focussing limit (protons) 100 MeV, avoided by using frequency modulation up to 180 MeV