Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 7 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 7 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 9 uppsatser.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 7 uppsatser.

<p>The incorporation of extremely compact multifunctional microsystems is a highly profitable long-term approach in spacecraft design. These systems bring substantial launch-cost reductions, and enable exciting space exploration and science missions.</p><p>Silicon microsystems technology is an adequate choice for the multifunctional microsystem development. However, the development of basic microsystems technology cannot be financed within application-specific space missions. Rather, the microsystems technology should be matured through fundamental research.</p><p>Silicon microsystems technology was used to develop a cold gas microthruster system suitable for minute movements of spacecraft (low Δv). In a hybrid integration, the system unit contains three silicon microsystem parts with four individual thrusters in total, together with external control electronics. The total mass is 0.35 kg.</p><p>Further integration will result in a mass of 0.08 kg. Complete system integration means that all package and interconnection levels are integrated into the silicon microsystem units. Several vital issues must be addressed, e.g. the reliable bonding of silicon wafers, the microfabrication process compatibility, and the manufacture process sequence. A graphical tool is introduced for process sequence evaluation.</p><p>Wafer bonding is used as fabrication process, assembly tool, and packaging technique. The quality and reliability of the bonded interfaces must be assessed in order to secure the operation of the microsystems in space. Therefore, statistical methods for burst test evaluation have been developed.</p><p>Weibull fracture probability functions have been derived in order to interpret the bond quality. In addition, rank-sum tests on spot series and analysis of variance are performed for bond quality diagnostics. The dependence on annealing temperature and surface-activation are presented, together with diagnosed degradation of insufficiently annealed bonds due to different spaceflight environments (thermal cycling, vibration, γ-irradiation).</p>

The incorporation of extremely compact multifunctional microsystems is a highly profitable long-term approach in spacecraft design. These systems bring substantial launch-cost reductions, and enable exciting space exploration and science missions. Silicon microsystems technology is an adequate choice for the multifunctional microsystem development. However, the development of basic microsystems technology cannot be financed within application-specific space missions. Rather, the microsystems technology should be matured through fundamental research. Silicon microsystems technology was used to develop a cold gas microthruster system suitable for minute movements of spacecraft (low Δv). In a hybrid integration, the system unit contains three silicon microsystem parts with four individual thrusters in total, together with external control electronics. The total mass is 0.35 kg. Further integration will result in a mass of 0.08 kg. Complete system integration means that all package and interconnection levels are integrated into the silicon microsystem units. Several vital issues must be addressed, e.g. the reliable bonding of silicon wafers, the microfabrication process compatibility, and the manufacture process sequence. A graphical tool is introduced for process sequence evaluation. Wafer bonding is used as fabrication process, assembly tool, and packaging technique. The quality and reliability of the bonded interfaces must be assessed in order to secure the operation of the microsystems in space. Therefore, statistical methods for burst test evaluation have been developed. Weibull fracture probability functions have been derived in order to interpret the bond quality. In addition, rank-sum tests on spot series and analysis of variance are performed for bond quality diagnostics. The dependence on annealing temperature and surface-activation are presented, together with diagnosed degradation of insufficiently annealed bonds due to different spaceflight environments (thermal cycling, vibration, γ-irradiation).

The PAMELA satellite experiment will soon be launched and during its 3 year mission perform measurement of charged particle fluxes in the cosmic radiation. PAMELA is specifically designed to identify antiprotons and positrons in the vast background of other charged particles. These antiparticle measurements will be performed using: a permanent magnet spectrometer, a scintillator based time of flight system, an electromagnetic imaging calorimeter, a transition radiation detector and a scintillator triggered neutron detector. There is also a scintillator based anticoincidence system to reject spurious triggers from out of acceptance events (developed and built at KTH). These detectors will allow the background in the antiproton and positron measurements to be significantly reduced, and PAMELA will thus be able to perform high precision measurements with unprecedented statistics and over a wide energy range, far surpassing any previous experiment. To determine the antiparticle identification and background rejection capability of the experiment, studies have been performed using simulations and data collected at particle beams. These studies have focused on: the proton rejection in positron measurements (using the calorimeter), contamination by locally produced pions in antiproton measurements and estimations of the expected statistics due to the energy dependence (caused by e.g. the geomagnetic field and the magnetic field in the spectrometer) of the gathering power. This work significantly extends previous studies of the PAMELA performance in antiparticle identification.

<p>The PAMELA satellite experiment will soon be launched and during its 3 year mission perform measurement of charged particle fluxes in the cosmic radiation. PAMELA is specifically designed to identify antiprotons and positrons in the vast background of other charged particles. These antiparticle measurements will be performed using: a permanent magnet spectrometer, a scintillator based time of flight system, an electromagnetic imaging calorimeter, a transition radiation detector and a scintillator triggered neutron detector. There is also a scintillator based anticoincidence system to reject spurious triggers from out of acceptance events (developed and built at KTH). These detectors will allow the background in the antiproton and positron measurements to be significantly reduced, and PAMELA will thus be able to perform high precision measurements with unprecedented statistics and over a wide energy range, far surpassing any previous experiment. To determine the antiparticle identification and background rejection capability of the experiment, studies have been performed using simulations and data collected at particle beams. These studies have focused on: the proton rejection in positron measurements (using the calorimeter), contamination by locally produced pions in antiproton measurements and estimations of the expected statistics due to the energy dependence (caused by e.g. the geomagnetic field and the magnetic field in the spectrometer) of the gathering power. This work significantly extends previous studies of the PAMELA performance in antiparticle identification.</p>

<p>Energetic neutral atoms (ENAs) are produced whenever a stellar wind encounters a neutral atmosphere. If a stellar wind proton comes sufficiently close to a neutral a charge-exchange reaction may take place, transforming the proton into an ENA. Unaffected by magnetic and electric fields, ENAs provide an opportunity for global imaging of stellar wind interactions.</p><p>This thesis presents methods and results of numerical modelling of stellar wind interactions. In particular it treats in depth production of ENAs at comets, Mars and the extrasolar planet HD 209458b.</p><p>Sufficiently accurate numerical models of stellar wind interactions require extensive computations. Parallel computing has therefore been used throughout the work, both for fluid and particle simulations of space plasmas. This thesis describes the use of a general simulation tool, providing parallel computing for space plasma simulations.</p><p>The thesis presents estimations of the magnitude and morphology of the ENA production at comets and HD 209458b. It compares the results obtained with observations and analyzes them in the light of ENA production at similar objects. Also, simulated ENA images for Mars were produced and compared to observations.</p>

Energetic neutral atoms (ENAs) are produced whenever a stellar wind encounters a neutral atmosphere. If a stellar wind proton comes sufficiently close to a neutral a charge-exchange reaction may take place, transforming the proton into an ENA. Unaffected by magnetic and electric fields, ENAs provide an opportunity for global imaging of stellar wind interactions. This thesis presents methods and results of numerical modelling of stellar wind interactions. In particular it treats in depth production of ENAs at comets, Mars and the extrasolar planet HD 209458b. Sufficiently accurate numerical models of stellar wind interactions require extensive computations. Parallel computing has therefore been used throughout the work, both for fluid and particle simulations of space plasmas. This thesis describes the use of a general simulation tool, providing parallel computing for space plasma simulations. The thesis presents estimations of the magnitude and morphology of the ENA production at comets and HD 209458b. It compares the results obtained with observations and analyzes them in the light of ENA production at similar objects. Also, simulated ENA images for Mars were produced and compared to observations.