We successfully launched a weatherballon with our instrument CHAOSjunior as part of “Highlights der Physik”, a science festival taking place in Kiel. The clear blue sky allowed a launch at around 11:45 am. Many spectators followed the launch and interesting questions were asked, especially by kids. We even had a send-off by a friend and colleague from the Department of Extraterrestrial Physics who accompanied our ballon with his plane. He took the pictures of the balloon from the air. Currently, we are on our way to Rostock to recover CHAOSjunior. Stay tuned for further information on CHAOSjunior and visit our social media channels and the channels of “Highlights der Physik”.
CHAOSjunior is a reduced version of the CHOAS experiment. The sensor head consists of a scintillator of Bismuth Germate Oxide (BGO) and two silicon detectors taken from High Energy Telecope (HET-B) in front of and behind the BGO. Two photodiodes were glued on the hexagonal BGO at opposite sides. The energy deposited in the detectors is proportional to the signals from the detectors. During configuration, the calibration parameter is determined. For this purpose a radioactive source of bismuth isotope 207 Bi is used. The characteristic lines of this source are known relatively precisely and can therefore be used for the calibration. First, the calibration of the HET-B detectors was carried out without BGO. The calculation of the channel names was chosen in following way. CHAOSjunior basically consists of three detectors, one HET-B, the BGO and another HET-B. These are named A,B and C in the direction of particle pass through. The information from the BGO (B) is shared between two channels. These are designated B1 and B2. The two HET-B detectors have only one channel each, these are designated AA and CC respectively. For calibration of preampfilters the sensor units were stimulated by a radioactive source of bismuth isotope 207 Bi. This isotope was placed in front of the sensor head. The prominent emission lines were taken from NUDAT3 (https://www.nndc.bnl.gov/nudat3/ ). The Compton effect of the γ lines at 569.698 keV and 1060 keV could be well observed for both HET-B signals where the first edge is much more precise. The data recorded was adapted by three models, one for the x-ray peaks and one for each Compton-edge. The models deliver the noise s and the calibration parameters u, which allow the conversion of the signals into keV.
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.
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.
BGO wrapped in teflon tape and put into old casing from HET
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.
