Alpine (micro)climate is among the
most sensitive to the industrially-increasing CO2 levels, and its
changes has already been documented instrumentally over the past hundred years
(e.g. a later snow onset in winter). However, in order to predict future
climate change and its impact on mountainous areas, one often lacks solid
evidence of what the climate was like in the past. To this end, the formation
of polished rock surfaces by sliding ice (glaciers), and the subsequent
preservation of these surfaces after the ice is gone (glaciers melt), holds key
information about past environmental conditions (ice thickness, snow cover,
temperature, cloudiness), often inaccessible otherwise. DTU Nutech has recently
pioneered two novel fields in radiation physics, which could be of particular value
in addressing past climate (change):
1) Surface exposure dating. When
freshly polished rock surfaces are exposed to sunlight, photons that penetrate
into the rock (following a Beer-Lambert law) may interact with trapped
electrons, effectively causing the progressive removal of the latter from the
uppermost crystals. Consequently, the longer a rock is exposed to sunlight, the
thicker the uppermost luminescence-free zone becomes:
Thus, the description of
luminescence gradients in exposed glacially-polished rocks provides
unprecedented information about the duration of ice- (and snow-)free periods,
sky cover, and micrometer-scale weathering of rock surfaces (after the glacial
2) Infrared Photoluminescence
(IRPL). The recent discovery of a direct and non-destructive way of probing (quantifying)
metastable electrons (i.e. electrons trapped within lattice defects) in the feldspar
mineral, is an important breakthrough in solid state physics:
and has immediate bearings on almost
all fields of retrospective dosimetry of common natural materials.
The IRPL signal, which arises from
the recycling of trapped electrons between their ground and excited states due
to optical stimulation, has an unprecedentedly high intensity and holds promise
for defect mapping at nanometer scales, thus potentially allowing the mapping
of luminescence gradients in exposed bedrock at an unprecedented precision.
In the current project, we seek to
investigate IRPL depth profiles in a suite of glacially-polished surfaces from
a famous high-Alpine pass (Gotthard), where the last meltdown of the European
Ice Cap (and hence the subsequent duration of bedrock exposure) are known
precisely from independent techniques. The aim of this project is twofold. The development
and testing of a new instrument (the spatially-resolved infrared
photoluminescence reader), will go hand in hand with investigating an ideal
case study (Gotthardpass), where abundant independent information on rock
exposure time, surface roughness, post-exposure snow cover, temperature, insolation
etc., puts maximum constraints on the expected IRPL profiles. Alongside the
development of the new instrument, you may find yourself working on a broad
array of veteran/novel equipment (low-level gamma spectrometers, Risø TL/OSL
readers, X-ray fluorescence spectrometers, and the CryOgenic LUminescence
Research facility), participating in the development of new instruments (e.g.
the spatially-resolved infrared photoluminescence reader), analyzing surface
roughness data from an optical 3D scanner (ATOS Core), researching insolation
models and developing/refining the kinetic model of feldspar luminescence.
The project is of strong
multidisciplinary nature, and is thus sufficiently flexible to follow your own
personal interest(s) and areas of competence. Primarily, we seek to clarify and
improve our understanding of the basic physical processes occurring inside
natural crystals exposed to radiation, light and heat with a motivation to
develop concrete applications in glacial geology and climate research. DTU
Nutech has >30 years of research in developing new instruments to facilitate
cutting edge research in ionising radiation dosimetry.
the environmental processes that affect luminescence gradients in exposed rock.
present-day environmental parameters at the Gotthardpass (Switzerland).
actual luminescence gradients from Gotthardpass (Switzerland) using a multitude
of radiation measurement techniques.
the quality and reproducibility of results, in light of the various
environmental and radiation factors.
the credibility/uncertainties of the obtained environmental parameter
in the development of novel equipment (spatially-resolved IRPL reader).
Supervisor: Mayank Jain
Co-Supervisor: Benny Guralnik
Curious mind; Enjoys handiwork/engineering; Experimentalist mentality (try – fail – try again); Comfortable with math and modelling (MATLAB)