After completing magnet studies, 5 magnet sectors were ordered from Vacuumschmelze (Hanau, D). Upon reception, the integrated field and multipoles were measured using the stretched wire technique at CERN's Magnetic Measurements Lab. Field components along x and y axes met specifications for all sectors. A 3D mapping of one magnet showed good agreement with simulations. One sector was vibrated and passed the test. 2 magnets were integrated into mini.PAN.
Once silicon strip detector specifications were defined, an order was placed. All sensors were delivered by November 2020. Mechanical sensors supported development of detector assembly on the front-end board, wire bonding, and preliminary vibration tests. Front-end boards were designed, produced, and tested — first in the lab with radioactive sources, then with particle beams at CERN (Geneva, CH). The boards were integrated into 3 tracker modules, each with 2 X- and 1 Y-sensor. The best 6 X- and 3 Y-sensors were integrated into mini.PAN. Detectors showed excellent performance, achieving 6 µm spatial resolution, further improved by combining measurements with the Pixel detector.
Pixel detector activities aimed to develop modules with four Timepix3 assemblies in a 2×2 configuration. A prototype PCB was tested with 4 naked Timepix3 ASICs and a quad bump-bonded to a 300 µm silicon sensor. The setup was tested in beams at the Nuclear Physics Institute in Řež (CZ), DCPT (Aarhus, DK), and CERN. Further studies addressed low-power modes and temperature dependence of energy measurement. After validating readout and electronics, final modules for mini.PAN were designed and calibrated. 2 modules with 2 readout systems were integrated into mini.PAN.
The TOF component identification involved simulations to define scintillator type and geometry. Various SiPM models were studied and tested with radioactive sources and lasers. Final components — scintillators, SiPMs, and ASICs — were selected and ordered. TOF mechanics, SiPM boards, and adapter boards were produced. TOF modules and prototypes were tested with particle beams at CERN. 2 modules were integrated into mini.PAN.
Data handling uses 4 GPIO board developed at the University of Geneva to read tracker and TOF modules via adapter boards. The Data Handling Unit (DHU) reads the GPIO boards, and uses a Katherine interface to read the Pixel detector. The DHU, a compact computer, is not integrated into the instrument.
Thanks to mini.PAN’s modular design, qualification tests (e.g. vibration) can be performed on individual detector modules. Most elements rely on technologies already used in space instruments. Mini.PAN was progressively integrated: tracker modules with magnet boxes, then Pixel modules, and finally TOF modules. The instrument was tested with particle beams at CERN and CNAO (Pavia, IT). It achieved a spatial resolution of 3.7 µm. Ion beam tests confirmed charge separation up to Z = 22. Kinetic energy resolution matches simulations: 0.18 for 400 MeV protons and 0.13 for 120 MeV electrons. Vibration tests at SERMS labs (Terni, IT) were successful for all modules and a mechanical simulator.
At the beginning of the project, a logo and website were created (
http://www.pan-space.eu(opens in new window)). PAN has been presented at various conferences and workshops.
In December 2023, a proposal based on the mini.PAN/Pix.PAN concept was submitted to ESA’s “Small Missions for Exploration – Destination the Moon” call. It was selected for a pre-Phase A study starting in December 2024. The concept is also under consideration for SWORD, an ESA space weather mission to monitor Earth’s radiation belts, which is currently under pre-Phase A study.
Data relevant to mini.PAN performance — including beam test data and calibrations — are openly available via the YARETA FAIR repository (
https://yareta.unige.ch/(opens in new window)) with metadata describing beam type, energy, detector setup, and data content.
