private:writeups:hallthrusters
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private:writeups:hallthrusters [2020/08/06 15:24] admin |
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| ====== Instabilities ====== | ====== Instabilities ====== | ||
| - | Several common low-frequency instabilities in HETs | + | Several common low-frequency instabilities in HETs. |
| + | |||
| + | Four main instabilities (plus a few lesser observed ones) | ||
| + | - Breathing mode (m=0 ionization instability) | ||
| + | - Spoke mode (m>1 ionization instability) | ||
| + | - Axial transit time oscillations (due to high electron resistivty) | ||
| + | - Azimuthal $E \times B$ electron drift instabilities (Related to strong $\nabla_z B_r$ gradients) | ||
| + | |||
| + | Impact HETs by | ||
| * these oscillations can indeed lead to violent conditions that could potentially damage the thruster discharge supply | * these oscillations can indeed lead to violent conditions that could potentially damage the thruster discharge supply | ||
| Line 246: | Line 254: | ||
| * Maybe another way to think of this is an azimuthally rotating ionization region with an azimuthal structure $exp \left( i(m\theta - \omega t) \right) $ where the mode number, $m$, is an integer greater than 0. | * Maybe another way to think of this is an azimuthally rotating ionization region with an azimuthal structure $exp \left( i(m\theta - \omega t) \right) $ where the mode number, $m$, is an integer greater than 0. | ||
| - | ==== 3. Azimuthal drift instability related to axial gradients in $\nabla_z B_r$ ($E \times B$ electron drift instability) | + | ==== 3. Azimuthal |
| Line 285: | Line 293: | ||
| * due to a too large electron resistivity | * due to a too large electron resistivity | ||
| + | [Me] | ||
| + | * The dependence on large electron resistivity to me is counter intuitive. | ||
| ==== 5. Poorly understood and unnamed instability ... ==== | ==== 5. Poorly understood and unnamed instability ... ==== | ||
| Line 414: | Line 424: | ||
| ====== Magnetic field design ======= | ====== Magnetic field design ======= | ||
| - | * [Hofer2014] | + | [Hofer2014] |
| + | * While a complete understanding of electron dynamics is currently unavailable, | ||
| of Hall thruster design. | of Hall thruster design. | ||
| + | [Bouef2017] | ||
| + | * The radial electric field (location and magnitude) is directly related to | ||
| + | - Electron transport | ||
| + | - electric field distribution | ||
| + | - ionization | ||
| + | - ion beam divergence through the potential distribution (I don't get this) | ||
| + | - Wall erosion by ions | ||
| ====== Open issues related to HETs ====== | ====== Open issues related to HETs ====== | ||
| (Need citations...) | (Need citations...) | ||
| Line 435: | Line 452: | ||
| * Discharge current measurements - Measurement of total current, I_elec + I_ion. | * Discharge current measurements - Measurement of total current, I_elec + I_ion. | ||
| * Highspeed videos of exhaust. | * Highspeed videos of exhaust. | ||
| + | |||
| + | |||
| + | ====== Ionization region ====== | ||
| + | |||
| + | ==== Length of ionization region ==== | ||
| + | |||
| + | [Boeuf2017] | ||
| + | * TODO | ||
| + | |||
| + | |||
| ====== Questions ====== | ====== Questions ====== | ||
| * Why is there no ion saturation limit to Hall thrusters? | * Why is there no ion saturation limit to Hall thrusters? | ||
| Line 446: | Line 473: | ||
| * [Boeuf2017] As the thruster size and power change, the current density does not change and stays on the order of 1000 A/m^2 in most Hall thrusters. | * [Boeuf2017] As the thruster size and power change, the current density does not change and stays on the order of 1000 A/m^2 in most Hall thrusters. | ||
| * Would secondary electrons generated by electron striking channel walls be an alternative source of electrons? | * Would secondary electrons generated by electron striking channel walls be an alternative source of electrons? | ||
| + | * There' | ||
private/writeups/hallthrusters.1596727455.txt.gz · Last modified: 2020/08/06 15:24 by admin
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