BEXUS Projects of Kiel University
SETH – CHAOS – FaNS – TANOS – ADAM – PING – FRED
Last week the big BGOs have arrived. One alone weighs over 1kg. Currently, two BGOs are covered with photodiodes. One with two on opposite sides and one with three each at an angle of 120 degrees. Subsequently, the dependence of the light output (sum of the diode signals) on the number and arrangement of the diodes is to be determined experimentally.
After performing a calibration measurement for the two HET-B detectors, the BGO was now also integrated into the sensor head and the two glued-on diodes were connected to the two free slots on the preamplifier board. The gain was changed to 3 in advance. Additionally two temperature sensors were connected. One measures the temperature directly at the BGO mount, the other is intended to look out of the box during flight and measure the environmental temperature.
Trigger thresholds for each channel were set to 5mV. In coincidence, the two BGO diodes trigger from even 3mV.
First measurements are running and results will follow shortly right here.
Today we have submitted our letter of intent to the BEXUS program marking our first steps to a possible participation in the next BEXUS-cycle
Our instrument CHAOS (Cherenkov Atmospheric Observation System) represents a scaled-down version of the ATHENA High Energy Particle Monitor (AHEPaM), which is designed to measure the background radiation of the ATHENA mission.
The preamplifier boards for CHAOSJunior were soldered according to slightly modified scematics of the High Energy Telescop (HET) experiment. For the detector setup of the balloon flight in September 2023, only four preamplifers are necessary and only those four were assembled for now. Since the HET preamp board has room for twelve preamps in total, more can be added at a later time for the detector setup of CHAOS. The assembled preamplifier board was tested for any short circuits and function of the operating points. The boards are working as desired and can now be tested further with attached detectors.
Today Myrdin and Stephan started to put together the sensor head of Chaos-Jr. Two spare Solo-EPD-HET-B detectors were put into a spare HET housing. The wires were soldered to the preamplifier board that was assembled by Sophie. The sensor is now connected to a RPiRENA on a Raspberry Pi1 and is taking data. Next we will put a ²⁰⁷Bi Source next to the sensor to perform a calibration with gamma and X-rays.
Observe how two preamplifiers are still unconnected. That is where the photodiodes from the BGO scintillator will be connected.
From September 25 to 30, 2023, the science festival “Highlights der Physik” will come to Kiel. As part of this event, we plan to fly a weather balloon with a CHAOSJunior experiment. This consists of a small hexagonal bismuth germanium oxide scintillator (BGO) with two photodiodes glued on opposite sides and two segmented solid state detectors (SSDs), which were adopted from the High Energy Telescop (HET) experiment. These HET-B detectors are placed in front of and behind the BGO and are used for coincidence measurements. In the past weeks, two photodiodes were glued to the BGO on opposite sides. The so prepared BGO was wrapped today in such a way that the light generated in the BGO is reflected on all inner sides and reaches the diodes. This BGO with diodes will be first tested in an already existing test can the following days. In the meantime, a pre-amplifier board for the flight is soldered and connected to the BGO diodes and the HET-B detectors. Then this setup will be tested.
The proposed CHAOS instrument needs a fairly large area Solid State Detector (SSD). All Detectors that we can use are spare parts from earlier space missions. For this large area SSD we put our eyes on a couple of recently rediscovered Soho Costep EPHIN F-Detectors, manufactured in the 1980ies.
A quick test revealed that all but one of them have excessive bias currents. The one good detector, unit F2, was subject of a C-V measurement, Capacitance versus bias Voltage. That kind of measurement tells about the impurity concentrations (dopands) and thickness of the detector.
The results confirm that the detector is about 700µm thick, and needs about 150V bias to be fully depleted, which is in range with the expectations. The diameter of the SSD is about 8cm.
This EPHIN F2 detector may become the anticoincidence counter of CHAOS. Currently it is tested in operation with cosmic muons and a gamma ray source.
Welcome to the internet presence of the Chaos project. For the next two years you will find updates of the project in this place. The server is a virtual maschine provided by netcup.de.
We don’t have a name for our new team yet, but we have a lot of motivated students and ideas for the next BEXUS project proposal from Kiel University.
With our project we want to do preliminary development work for the ATHENA High Energy Particle Monitor (AHEPaM), which will measure the non-photonic background radiation for the space X-ray telescope ATHENA.
In addition, we want to launch a light junior version beforehand using our own weather balloon as part of the Science Festival “Highlights of Physics” in Kiel.