Preparing for bake out
The bake out cables have been installed and will allow to bake out of the vacuum chamber up to 150° C, the maximum of the bake out wires and viton o-rings currently utilised. Total heating power is 700W and the vacuum chamber will be covered with aluminium foil for insulation and better heat dispersion.
The whole setup was rearragned to improve safety and minimise interference. The left rack contains all high voltage and high current low voltage power supplies. All feedthroughs and connections will also be placed on the left side of the vacuum setup. The right rack contains all the measuring, analysing and logging equipment and all related vacuum gauges have also been placed on the right side of the vacuum chamber. Cable crossings of power and measuring wiries has thus been minimised. Grounding on both racks has been extended and all ion gauge equipment utilising high voltages have been additionally grounded.
New high voltage power supply
Recently a Glassman PS/WG-50P6-X68 50kV 6mA power supply was acquired. The power supply was listed as non working and Glassman was not able to provide a digital copy of the manual. After some trial and error all the connections and jumpers could be reverse engineered. The power supply seems to be specially designed for the spectrometer it was originally used for. The circuit for selecting preset voltages was replaced with a normal multiturn potentiometer to select the voltage limit.
The next step was to change the polarity of the high voltage multiplier. All the diodes were reversed and the negative high voltage feedback connection was deduced by some trial and error. The negative voltage current feedback could not be found and is inverted using an inverting opamp circuit.
The power supply was load tested up to 4kV/7mA and seems to be working correctly. When the feedthrough has been modified further testing will be done.
Initial electrolysis tests
To test the dryer requirements and the electrolysis setup itself a simple test setup was made. A hose, ~20mm diameter, 500mm length, was filled with indicating silica gel to dry the D2/D2O mixture from the electrolysis setup. The electrolysis setup itself consists of an oil bubbler filled with approximately 6ml of D2O and using 2 platina electrodes. NaHCO3 (baking soda) is used as electrolyte and depending on the flow we use 30V at 300mA to power the electrolysis setup (although this also causes heating and cooling is need for prolonged electrolysis...).
Using the QMG-064 we made some scans of the gas spectrum at lower pressures to asses the D2O contamination, the photos show an early spectrum and an annotated spectrum where the D+2 slowly starts to increase over the other peaks. The N+2 and O+2 results from remaining air in the dryer and D2 lines because they were not evacuated to vacuum before starting electrolysis. These gasses will slowly be purged over time and in the future the electrolysis system will be pulled to a vacuum to minimize any N2 and O2. No absolute values can be provided since there are still problems with the QMA.
Initial grid tests
Today the first tests with the new grid were done. The high voltage feedthrough is a 40kV vacuum feedthrough mounted on a DN100 CF blind in which we have drilled the appropriate holes. The grid stalk consists of a stainless steel rod with two holes with screws to clamp the grid stalk and feedthrough rod. The grid itself is made of tungstens. This will allow to easily interchange different grid configurations and to exactly position the grid in the center or off-center if that is necessary.
Vacuum pressure control ready
The Granville Phillips 216 metal seated valve has been installed and connected to the vacuum chamber. This electrically controlled valve is fully metal and allows to control pressures ranging from 10-11 to 6000 Torr. The accompanying controller provides PID control but this will most likely be replaced by a custom pressure control system.
High voltage supply ready
The high voltage transformer enclosure has been finished. It features a center tapped x-ray transformer and a small ballast under transformer oil with voltage and current monitoring on the secondary side. Preparations have been made for external oil cooling and temperature monitoring.
The enclosure will be mounted in a rack unit combined with an arduino microcontroller. The arduino will be used to control the transformer via phase cutting. This will allow to limit voltage, current, power and temperature.
In the future also a smoothing capacitor will be added.
About Radiant Matter Research
Radiant Matter Research is a Dutch research project on alternative designs for fusion reactors. Currently the tokamak reactor design is the standard for fusion while inertial electrostatic and electrodynamic confinement fusion receive little to no attention. This project, run by two students on a very limited budget, tries to offer a practical approach to these technologies to advance the development of fusion energy.
We would like to thank the following people and companies for their support: