Download - Setup for large area low-fluence irradiations with quasi-monoenergetic 0.1−5 MeV light ions
Setup for large areaSetup for large arealow-fluence irradiations withlow-fluence irradiations with
quasi-monoenergetic 0.1−5 MeVquasi-monoenergetic 0.1−5 MeV
light ionslight ions
M. Laitinen1, T. Sajavaara1, M. Santala2 and Harry J. Whitlow1
1 Department of Physics, P.O.B 35, FIN-40014 University of Jyväskylä, Finland2 Laboratory of Advanced Energy Systems, P.O.B 4100, FIN-02015 HUT, Finland
email: [email protected]
Motivation for the setup Particle response of prototype detectors, requirements for testing
facility: Large area for testing
multiple detectors at thesame time
Up to 10 cm x 10 cm
Low fluence
Well known uniform distribution needed
Flux lower than 1 particle s-1 mm-2
Monoenergetic beam
Energy distribution of the flux below 10 keV (FWHM), from 100 keV to 5 MeV
Quick change of beam energy
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Methods for low fluence large area irradiations
How to irradiate ? Radioactive sources
Limited energy (~3-6 MeV) range
Limited ion range (only 4He ions)
Implanters/ion sources High flux
Energy range limited to < 1 MeV(normally < 100 keV)
Methods for low fluence large area irradiations
RADEF (JYFL cyclotron, with direct beam)
Minimum energy ~5 MeV
Small accelerators (with direct beam)
Scatterers/wobblers needed → energy spread
Small fluxes difficult Large homogenous areas difficult
The idea of the setup Not using the primary beam but
instead the secondary beam of the small linear accelerator in JYFL
Secondary beam from particles that have undergone backscattering is used in detector testing with well known properties
Target is made of thin self-supporting carbon foil (10 g cm-2 ~50nm) where thin layer (2-25 nm) of single isotope element (Au, Rh, Nb, Co, Al eg.) has been deposited
Most of the primary beam goes through the target and hits the targetholder’s backwall from where it cannot backscatter to the detectors → virtually no background
IncomingPrimary beam0.2-5.2 MeV(for He)
Sample holder backwall
Sample holder
Thin Au layer on top of carbon foil
Backscattering from Au (+ C) to detectors
Removable samplesupports
Setup at the Pelletron accelerator
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O from AlOx
Carbon foil 10 g/cm2
Al 20 nm100 % of original intensity
Co 10 nm25 % of original intensity
Au 5 nm25 % of original intensity
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Backscattered energy [keV]
1600 keV He+ beam, detector at 152 degree
Au 60 nm2.5 % of original intensity
Reference detector data Flux and energy calibrated from
reference detector and multiple targets
Implanted Si surface barrier detector
~14 keV FWHM energy resolution
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FWHM~16 keV
True valuefor backscattered
beam closer to8 keV
Reference spectra and target Sample turret can be
modified to take up to 20 targets
In current system 5 targets can be loaded same time to the chamber
Logarithmic scale shows that there is a minor background below Au peak
Backscattering starts at the components of steel
Also for part of the background the origin is due to multiple scattering especially for low energies
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Energy [keV]
1600 keV primary He beam, detector at 152 degree
50 nm C foil5 nm Au
O peaks on C foil ?
Figures of merit for the setup Energy range
150 – 5000 keV for He 150 – 3000 keV for H
Flux Up to 500 particles per second
per cm2 (100 – 5 s-1 cm-2) For lowest energies maximum
fluxes get lower Cycle time
During last 2 day test period:He 1st day, H 2nd day, 5-7different accelerator energiesfor 3 different detector setsper day (up to 20 cycles per day).
Multiple detectors at once 4 minute down-pumping time
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1823.7 keV
1800.0 keV
129.5 %
100 %
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Angle dependencies for energy ( ) and intensity ( )
Ene
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Backscattering angle [degree]
83.7 %
1782.0 keV
Angles 'seen' from chambers 45 degree port,He from Au scatterer
Flux homogeneity Can be easily calculated for both
energy and intensity
NPA – results from the setup Neutral particle analyzers for Joint European Torus JET 1st tests showed strange double peak behaviour and bad
resolution 2nd set of detectors performs much better: Improved resolution
and effiency, no double peaks but small tail
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Reference 150 keV 200 keV 600 keV
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NPA, first real results 150 keV 200 keV 600 keV
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NPA detector, 2nd test
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Energy [arb. units]
200 keV (5 nm Au) 400 keV (5 nm Au) 800 keV (5 nm Au) 1500 keV (60 nm Au) 3000 keV (60 nm Au)
A novel silicon detector for neutral particle analysis in JET fusion research Kalliopuska J, Garcia F, Santala M, et al.NIM A, vol. 591, 1, p. 92-97 (2008)
Future improvements
H - beam currents limited now by ion source New ion source coming before summer
Order of magnitude increase to H currents
Heavier ions including Li available from new ion source
Beam blanker for the prototype detectors Total fluxes and energies calibrated from reference
detector before letting the beam to the test detector
Full understanding of reference spectrum through Monte Carlo simulations
Thank you for your attention !
Accelerator based materials physics
goup in JYFL
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Scattered He with different beam energies 200 keV (5 nm Au) 400 keV (5 nm Au) 800 keV (5 nm Au) 1500 keV (60nm Au) 2250 keV (60nm Au) 3000 keV (60nm Au)
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Scattered H with different beam energies 190 keV (60nm Au) 250 keV (60nm Au) 400 keV (60nm Au) 700 keV (60nm Au) 1100 keV (60nm Au) 1500 keV (60nm Au)
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NPA detector counts at different energies 200 keV (5 nm Au) 400 keV (5 nm Au) 800 keV (5 nm Au) 1500 keV (60 nm Au) 3000 keV (60 nm Au)
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Energy [channels]
Scattered He with different beam energies 200 keV (5 nm Au) 400 keV (5 nm Au) 800 keV (5 nm Au) 1500 keV (60nm Au) 2250 keV (60nm Au) 3000 keV (60nm Au)
NPA schematics
NPA linearity for Hydrogen
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