This all started with brainstorming about two years ago. I did a lot of the preliminary research and began to learn what a gamma ray scintillator does and how it does it. Then in early 2015 I started roughing out a design with the (later unsuccessful) goal of having something we could launch in the annual August flight. Due to not following my methodology closely I got distracted by the ground station tracking system that had been needing improvements since the WiFi project flight. Then life got in the way.
In November 2015 the second blow in the collapse of the energy industry hit and ate up all my free time. I am now back to part-time consulting and have the time and energy to restart this project.
In no particular order, here are the things I have done up to this writing:
- Research the concepts of Gamma Ray Spectroscopy
- Determine the major components used. A Photomultiplier tube (PMT) and a scintillating material (sensor) are required. The PMT will need a high voltage power supply and its output will need shaping and conditioning of the pulses.
- Deep dive the web to see what major components cost and what is in/out of reach for this project
- Research the things required for general High Voltage (HV) design
- Research HV power supply noise
- Determine what work in the Gamma Ray Spectroscopy field might have relevance and download any papers, presentations, and datasheets that are potentially relevant
- Determine what the form factor of the enclosure will be (approximately)
- Perform enough research to determine what type scintillating crystal would have good availability, minimal degradation for used parts, and could be purchased on a hobbyist budget. I decided on an organic material.
- The organic that seemed the best match to the requirements up to this point was a Polyvinyltoluene (PVT) sensor. One of the industry standards is the BC-xxx series made by Saint Gobain Crystals in Ohio, USA.
- Some of this material was available surplus on e-Bay.
- The same process was used to decide on a Hammamatsu PMT. The R9420 had a good mix of size, sensitivity, and e-Bay availability
- So I purchase a PMT and a scintillating crystal.
- From the PMT and crystal choice I was able to determine the HV power supply requirements.
The things I need to do now to get the project back on track and well defined are:
- Go back through all my notes and get "back up to speed" and where I was.
- Design the power supply and get parts. Then simulate it, tweak as required, and build a breadboard prototype.
- At this point I will have done the informal parts of my project steps and I need to go back and formalize them to build a proper plan of how to move forward to meet the balloon launch objective of August 2017 (along with all the needed test points and payload integration.
This is the first time I have experimented with "going public" on a project as it is being done. The old saying is, "sausage is a tasty treat, but you don't want to have to see it being made." Because of that I have been reluctant to share things until they were fully cooked. My hope is that by showing the process, it will keep me motivated and hopefully help others.
Onward to the edge of space!