Academic Interests
Spacecraft charging, numerical particle-in-cell methods. Audio and signal processing.
Courses taught
Background
- Scientist NILU - Norwegian Institute for Air Research
- Product Manager- Elliptic Labs
- CTO - Squarehead Technology / labs
- Researcher - Vivid AS
Tags:
Electronics,
Instrumentation,
Space Physics
Publications
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Kjølerbakken, Kai Morgan; Miloch, Wojciech Jacek & Røed, Ketil
(2023).
Sheath formation time for spherical Langmuir probes.
Journal of Plasma Physics.
ISSN 0022-3778.
89(1).
doi:
10.1017/S0022377822001027.
Full text in Research Archive
Show summary
The formation time of the surrounding sheath of Langmuir probes in an ionospheric plasma has been studied to better understand the constraints this puts on the sampling frequency of a probe. A fully kinetic three-dimensional particle-in-cell model is used to simulate the temporal effects in the electron saturation region as the sheath forms. The stability of the probe current and the stability of the ion and electron density in the vicinity of the probe have been used to evaluate when the sheath was formed. Simulated results were compared with theoretical models and are in good agreement with the theoretical results. This shows that theoretical models can be used as guidance to estimate the formation time and to determine the sampling rate for a swept bias Langmuir system. Our results also show that the formation time is less affected by the plasma temperature and bias voltage as we move into the thick sheath regime, and will instead be determined by the plasma density. The presented results also show that applying a step function to the probe could be used to characterise ions species composition, or to estimate the ion density.
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Kjølerbakken, Kai Morgan; Miloch, Wojciech Jacek; Martinsen, Ørjan Grøttem; Pabst, Oliver & Røed, Ketil
(2022).
Numerical Study of Non-Linear Effects for a Swept Bias Langmuir Probe.
IEEE Transactions on Plasma Science.
ISSN 0093-3813.
50(5),
p. 1237–1245.
doi:
10.1109/TPS.2022.3164220.
Full text in Research Archive
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We present a numerical study disclosing non-linear effects and hysteresis loops for a swept bias Langmuir probe. A full kinetic particle in cell (PIC) model has been used to study the temporal sheath effects and the probe current. Langmuir "close to steady state" condition is required to characterize the plasma. However, during operations above frequencies normally used, capacitive and non-linear resistive effects are being unveiled. We demonstrate how ion and electron density and temperature change properties of the probe-plasma system. We also show that a swept Langmuir probe exhibits essential properties described as the "fingerprint of memristors" and how a Langmuir probe can be identified as a transversal memristor. Understanding non-linear processes might enable new ways to operate Langmuir probes with higher sampling rates and better accuracy.
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Kjølerbakken, Kai Morgan; Miloch, Wojciech Jacek & Røed, Ketil
(2021).
The influence of probe spacing and probe bias in a double Langmuir probe setup.
AIP Advances.
ISSN 2158-3226.
11.
doi:
10.1063/5.0058540.
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Multi-needle Langmuir probes are mounted on satellites and sounding rockets for high-frequency characterization of plasma in the ionosphere. Mounted on a spacecraft, the recorded probe current often differs from expected results. In this paper, we perform a numerical study using a particle in cell model to see how the spacing between the individual probes used in a multi-needle setup influences the measured current. We also study how the applied probe bias voltage can contribute to deviations. In our study, we use realistic electron temperatures and electron densities for the relevant part of the ionosphere. However, the results should be generally applicable and valid for other space environments as well as for laboratory Langmuir probe applications. From our study, we can see that when the distance is short, less than two Debye lengths, the current is highly affected, and we can see deviations of more than 60% compared to a single probe setup.
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Hafizovic, Ines; Nilsen, Carl-Inge Colombo; Kjølerbakken, Kai Morgan & Jahr, Vibeke
(2012).
Design and implementation of a MEMS microphone array system for real-time speech acquisition.
Applied Acoustics.
ISSN 0003-682X.
73(2),
p. 132–143.
doi:
10.1016/j.apacoust.2011.07.009.
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Holm, S; Brungot, John; Ronnekleiv, A; Hoff, Lars; Jahr, Vibeke & Kjølerbakken, Kai Morgan
(2007).
Acoustic passive integrated transponders for fish tagging and identification.
Aquacultural Engineering.
ISSN 0144-8609.
36.
Show summary
The results indicate that it is possible to develop a low-cost system for underwater identification of fish suitable for a high automation level. This could open up for improvements of logistics in for instance the fish fanning industry. (c) 2006 Elsevier B.V. All rights reserved.
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Ogul, Hasan; Aamodt, Jonas Moræus; Misra, Sanjay & Kjølerbakken, Kai Morgan
(2024).
2024 4th International Conference on Applied Artificial Intelligence (ICAPAI).
IEEE conference proceedings.
ISBN 979-8-3503-4976-4.
300 p.
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Brungot, John; Holm, Sverre; Hoff, Lars; Rønnekleiv, Arne; Kjølerbakken, Kai Morgan & Jahr, Vibeke
(2004).
VivID – patentert metode for merking og identifisering av fisk i vann.
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Lindem, Torfinn; Balk, Helge; Vibeke, J. & Kjølerbakken, K. M.
(2002).
Measurements of acoustic sound fields in a shallow river.
Show summary
From earlier experiments, we have seen indications that the sound field
from a horizontally aligned transducer in shallow water can differ from
the expected field. If this is the case, this phenomenon can have an
impact on the measured target strength from fish and on sample volume.
Hence, it has been important to verify this by controlled experiments.
We have measured the sound field produced by a Simrad ES120-4, 120kHz,
4x10 deg. split beam transducer in a shallow river. These measurements
were made with a Reason hydrophone. Reflections from the bottom and
surface made modifications to the transmitted pulse. In some positions
they could even form separate pulses. These pulses were sufficiently
separated in time to produce phantom echoes. Results from this
experiment will be presented.
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Kjølerbakken, Kai Morgan
(2022).
Computational Study of Langmuir Probe Properties in Ionospheric Plasma.
Universitetet i Oslo.
ISSN 1501-7710.
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Kjølerbakken, Morgan & Vallejo, Islen
(2015).
System design NBV.
NILU.
ISSN 978-82-425-2771-4.
Full text in Research Archive
Show summary
System design for «nasjonalt beregningsverktøy» describing data flow and infrastructure requirements.
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Published
Jan. 11, 2017 10:07 AM
- Last modified
Nov. 19, 2018 11:21 PM