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: mikko.i.laitinen@jyu.fi

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

Fro

m J

ET

col

labo

ratio

n w

eb-p

age

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

Ref

eren

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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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Steel background

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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

110 120 130 140 150 160 1700.250.500.751.001.251.501.752.002.25

17001720174017601780180018201840186018801900

1823.7 keV

1800.0 keV

129.5 %

100 %

Rel

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Angle dependencies for energy ( ) and intensity ( )

Ene

rgy

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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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Energy [arb. units]

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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Energy [channels]

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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