Author name code: golding
ADS astronomy entries on 2022-09-14
author:"Golding, Thomas Peter"
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Title: Development of III-V barrier diode radiation-hard infrared
detectors for space applications
Authors: Wheeler, R.; Mason, I.; Jerram, P.; Stocken, P.; Jordan,
D.; Willis, M.; Carmichael, M.; Craig, A. P.; Golding, T.; Marshall,
A. R. J.
Bibcode: 2020SPIE11537E..0JW
Altcode:
Opto-electronic devices destined for space must be suitably
radiation-hard, meaning that they must be resilient to the effects of
high energy radiation in space. For high performance IR (infrared)
space-based applications, the current material of choice is MCT
(Mercury Cadmium Telluride). MCT is difficult and therefore expensive
to fabricate and the constituent materials are becoming increasingly
restricted by regulation. The new generation of barrier diode
detectors based on III-V materials offer a promising alternative to
MCT, providing comparable performance whilst offering devices that
are compatible with volume manufacturing processes. As part of a
DASA Space-to-Innovate Phase 1 funded project we have developed a
novel radiation hard unipolar barrierbased ABaT™ III-V MWIR diode
detector. The detector is being subjected to gamma and proton radiation
testing to demonstrate its suitability for space environments. To
compare the radiation performance of this diode, a number of other
typical III-V detector diode structures have been fabricated and
tested. In this paper we present the results of the project so far
and future plans to develop this into detector arrays.
Title: Formation of the helium extreme-UV resonance lines
Authors: Golding, T. P.; Leenaarts, J.; Carlsson, M.
Bibcode: 2017A&A...597A.102G
Altcode: 2016arXiv161000352G
Context. While classical models successfully reproduce intensities
of many transition region lines, they predict helium extreme-UV
(EUV) line intensities roughly an order of magnitude lower than the
observed value.
Aims: Our aim is to determine the relevant
formation mechanism(s) of the helium EUV resonance lines capable of
explaining the high intensities under quiet Sun conditions.
Methods: We synthesised and studied the emergent spectra from a 3D
radiation-magnetohydrodynamics simulation model. The effects of coronal
illumination and non-equilibrium ionisation of hydrogen and helium
are included self-consistently in the numerical simulation.
Results: Radiative transfer calculations result in helium EUV line
intensities that are an order of magnitude larger than the intensities
calculated under the classical assumptions. The enhanced intensity
of He Iλ584 is primarily caused by He II recombination cascades. The
enhanced intensity of He IIλ304 and He IIλ256 is caused primarily by
non-equilibrium helium ionisation.
Conclusions: The analysis
shows that the long standing problem of the high helium EUV line
intensities disappears when taking into account optically thick
radiative transfer and non-equilibrium ionisation effects.
Title: Non-equilibrium helium ionization in the solar atmosphere
Authors: Golding, Thomas Peter
Bibcode: 2017PhDT.......215G
Altcode:
No abstract at ADS
Title: The cause of spatial structure in solar He I 1083 nm multiplet
images
Authors: Leenaarts, Jorrit; Golding, Thomas; Carlsson, Mats; Libbrecht,
Tine; Joshi, Jayant
Bibcode: 2016A&A...594A.104L
Altcode: 2016arXiv160800838L
Context. The He I 1083 nm is a powerful diagnostic for inferring
properties of the upper solar chromosphere, in particular for the
magnetic field. The basic formation of the line in one-dimensional
models is well understood, but the influence of the complex
three-dimensional structure of the chromosphere and corona has however
never been investigated. This structure must play an essential role
because images taken in He I 1083 nm show structures with widths
down to 100 km.
Aims: We aim to understand the effect of
the three-dimensional temperature and density structure in the
solar atmosphere on the formation of the He I 1083 nm line.
Methods: We solved the non-LTE radiative transfer problem assuming
statistical equilibrium for a simple nine-level helium atom that
nevertheless captures all essential physics. As a model atmosphere we
used a snapshot from a 3D radiation-MHD simulation computed with the
Bifrost code. Ionising radiation from the corona was self-consistently
taken into account.
Results: The emergent intensity in the He
I 1083 nm is set by the source function and the opacity in the upper
chromosphere. The former is dominated by scattering of photospheric
radiation and does not vary much with spatial location. The latter
is determined by the photonionisation rate in the He I ground state
continuum, as well as the electron density in the chromosphere. The
spatial variation of the flux of ionising radiation is caused
by the spatially-structured emissivity of the ionising photons
from material at T ≈ 100 kK in the transition region. The hotter
coronal material produces more ionising photons, but the resulting
radiation field is smooth and does not lead to small-scale variation
of the UV flux. The corrugation of the transition region further
increases the spatial variation of the amount of UV radiation in the
chromosphere. Finally we find that variations in the chromospheric
electron density also cause strong variation in He I 1083 nm
opacity. We compare our findings to observations using SST, IRIS and
SDO/AIA data.