Timepix detectors are USB-powered particle trackers based on Medipix technology developed at CERN. Each detector consists of the Medipix chip coupled to a silicon sensor and incorporated into a readout system about the size of a USB pen drive, developed at the Institute of Experimental and Applied Physics (IEAP) in Prague, Czech Republic.
The detectors have been used in a variety of disciplines from the study of cosmic rays to biomedical imaging. Now NASA is using them on board the ISS to accurately monitor radiation doses in space.
“There’s nothing else in the world that has quite the capability of Timepix detectors to identify individual particle tracks,” says Lawrence Pinsky, a Medipix2 Collaboration member who drove the push to get Timepix detectors into space. “The ISS Timepix detectors will gather data to characterize the radiation field as a function of time, taking precise measurements of the spectrum of charge and velocity of particles present inside the spacecraft.”
Heavy-ion radiation is one of the many radiation types the ISS detectors will measure. Heavy ions occur naturally only in space, although they are produced artificially on Earth in accelerators and cancer-treatment facilities. While the effects of acute exposure to heavy-ion radiation –that is, exposure to heavy doses over very short periods of time – are relatively well understood, the effect of chronic exposure remains unclear.
“We know that heavy ions – the bare nuclei rattling around in space – are hugely more effective at causing long-term health risks per unit of energy,” says Pinsky. “But assessing the full extent of these risks is difficult. Studies have been conducted at heavy-ion treatment facilities using cell cultures, but they are historically unreliable when transferred to implications for humans.”
The ISS Timepix detectors will measure baseline characteristics of heavy-ion radiation, to help radiation experts understand the nature of the exposure to astronauts, as well as the potential long-term side effects of heavy-ion cancer therapy.
NASA has already approved Timepix detectors to fly on the first test flight of the Orion module – part of the next generation of manned US spacecraft. Launch is scheduled for 2014, giving the Medipix3 Collaboration the chance to improve their detectors even further. “This first trip to the ISS is an opportunity for us to get some real experience using the detectors in space, which will drive the development of the next generation of Timepix,” says Pinsky.