1070-9878/06/$20.00 © 2006 IEEE
Two-phase Emission Detectors: Foundations and
Alexander I. Bolozdynya
Department of Physics, Case Western Reserve University
10900 Euclid Avenue
Cleveland, Ohio 44106-7079, U.S.A.
A new class of radiation detectors has recently been introduced into experimental
practice. The detectors employ the effect of effective extraction of charge carriers from
condensed non-polar dielectrics into the equilibrium gas phase under influence of an
applied electric field. This approach makes possible to combine in one detector
condensed detecting medium of a large mass, necessary for detecting rare events, with
a rarefied phase, in which signals due to a few or even single electrons can be amplified
and measured through the
gas-discharge or electroluminescence processes. We will
discuss properties of working media that can be used in emission detectors, the physics
of charge carrier penetration through the inter-phase boundary and we will also
review applications of two-phase dielectrics for detecting ionizing radiation and exotic
Electron emission, ion emission, electroluminescence devices,
radiation detectors, elementary particles, superconducting devices.
electrons, liberated by ionizing radiation, i.e.
chemically unbound to molecules of condensed nonploar
dielectrics, can be efficiently transferred into the gas phase
from quasi-free states in condensed Ar, Kr, Xe, CH
, solid Ne
and some liquid saturated hydrocarbons, as well as from
localized states in dielectrics with a positive ground state
potential such as helium.
Using the transition of electrons
across phase boundaries allows effective amplification of
weak signals in order to construct novel extremely sensitive
CHARGE CARRIERS EMISSION FROM
Since the dielectric constant of non-polar dielectrics in the
condensed phase is larger than that of the saturated gas,
charge carriers experience an image potential
interface acting against their emission into the gas. The image
potential is temperature dependent approaching zero at
temperatures close to the critical temperature. At the electric
, applied to extract electrons from the condensed
dielectric, and the energy of the ground state of quasi-free
, the total potential energy of electrons in the
vicinity of the inter-phase surface may be described in terms
of a one-dimensional potential (Figure 1a).
Potential energy near the interface of two-phase dielectrics
favorable for emission of excess electrons from the quasi-free state (a) and
from the localized state (b).
Manuscript received on 15 September 2005, in final form 3 March 2006.