[institut] seminar u utorak 01.11.2016. Dr. Károly Tőkési

[Bratislav Marinkovic]

Poštovane koleginice i kolege,

Pozivamo Vas na 

SEMINAR PROJEKTA #OI 171020 

LABORATORIJA ZA FIZIKU ATOMSKIH SUDARNIH PROCESA 

U utorak, 01.11.2016. sa početkom u 11 časova u sali "Dragan Popović"
Instituta za fiziku: 

"_CHARGE RELAXATION IN MACROSCOPIC GLASS CAPILLARY AFTER ION BEAM
IRRADIATION_" 

_DR. KÁROLY TŐKÉSI_ 

_Institute for Nuclear Research, Hungarian Academy of Sciences (Atomki),
4026 Debrecen Bem tér 18/c, Hungary, EU_ 

_ELI-ALPS, ELI-HU Non-profit Ltd., Dugonics tér 13, H-6720 Szeged,
Hungary, EU_ 

Abstract: 

            While the guiding of ions through glass-capillaries due to
charged patches is qualitatively understood [1], the complex nature of
the electric conduction in such insulators makes quantitative
predictions still a challenging task. Indeed, for a given ion beam, the
guiding is determined by the charging rate combined with the discharge
rate where the "discharge" dynamics of the charge patches at the surface
depend on the electrical properties of insulators and on the position
and nature of grounded electrodes.  In order to get some insights into
the discharge dynamics in those insulators, we did a combined
experimental and theoretical study of the charge relaxation in glass
capillaries. We studied the discharge of the conical macro-capillary
after irradiation with highly charged ions. The electric field,
generated by the initially deposited charges is monitored by a bypassing
ion beam. The latter is deviated by the electric field and its Coulomb
deflection is followed in time on a position sensitive detector,
yielding the relaxation in time of the deposited charge. 

Using a home-made numerical code [2], the same observables were
simulated and compared to the experimental data. They highlight the
importance of the depolarization field due to the ionic conductivity in
glasses. Indeed, if the conductivity was due to electron and hole
mobility alone, the discharge curve has a non-exponetial form, which
contradics our experimental data, which show a perfectly exponetial
decrease of the charge. Least but not last, it was found that much
attention must be paid to secondary electrons generated by the beam, as
they contibute strongly to discharge the capillary. They effect on the
discharge is highlited. 

References: 

[1] K. Schiessl, W. Palfinger, K. Tőkési, H. Nowotny, C. Lemell, and J.
Burgdörfer, Phys. Rev. A.72 (2005) 062902. 

[2] E. Giglio, R.D. DuBois, A. Cassimi, K.Tőkési, Nucl. Instr. and Meth.
Phys. Res. B354 (2015) 82. 

-- 
Dr. Bratislav Marinkovic
Head of Laboratory for Atomic Collision Processes
Institute of Physics Belgrade
University of Belgrade
Republic of Serbia
Pregrevica 118, 11080 Belgrade, Serbia
tel:+381 11 316 0882
fax:+381 11 316 2190
http://mail.ipb.ac.rs/~marinkov
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