METU-DBL: A Cost Effective Proton Irradiation Facility

Middle East Technical University Defocusing Beamline (METU-DBL) delivers protons with selectable kinetic energies between 15 - 30 MeV, and proton flux 10 ⁶ - 10 ¹⁰ protons/cm ²/s on 21.55 cm x 15.40 cm beam area with beam uniformity within ±6% at the test region in accordance with the ESA ESCC No. 25100 standard for single event effect (SEE) tests. High proton fluences can be achieved, allowing users to test space-grade materials; electronic circuits, ASICs, FPGAs, optical lenses, structural elements, and coating layers for LEO, GEO, and interplanetary missions. Secondary particles are created during proton-material interactions with the first beam collimator and beam dump. The total received dose on the Device-Under-Test (DUT) never exceeds 0.1% of the dose from the primary protons. A secondary measurement station has been constructed next to the first collimator, providing neutrons for neutron experiments. A rotating drum can hold multiple samples for neutron experiments. At the target region, a robotic table is located, which provides mechanical and electrical mounting points to the samples and allows multiple samples to be tested in a row. A modular vacuum box can also be attached on the robotic table for any test that may require a vacuum environment. Power rails on the robotic table provide various outputs for the DUT. For the data acquisition, high-speed networking and a modular industrial PC are available at the target station. The design of the METU-DBL control software enables test users to integrate and optimize the data acquisition and controlling of the DUT. Beam properties at the target region are measured with the diamond, Timepix3, and fiber scintillator detectors on the robotic table. With diamond and Timepix3 detectors, measurements are taken from the five different points (center and the four corners) of the test area to measure the proton flux and ensure that it is uniform across the full test area. Fiber scintillators on both axes (X and Y) scan the target area to cross-check the beam profile's uniformity. Secondary doses during the irradiation test are measured by a Geiger sensitive to electrons and gammas above 0.1 MeV and a neutron detector located at the entrance of the R&D room. The room cools down relatively fast after any irradiation (<1 hour). Accurate linear energy deposition rates and absorbed doses on the samples are calculated using MCNP6, FLUKA, and Geant4 Monte Carlo codes. Alanine dosimetry measurements that are calibrated with simulations are also used to estimate the absorbed dose on the sample.