One second after the Big Bang neutrinos decoupled from the expanding plasma that was to become our Universe. These neutrinos still exist, but are now at a temperature of 1.9 K, which makes their energy too low for existing detection methods. Within the PTOLEMY collaboration we have developed a design for a detector to observe these relic neutrinos for the first time. When captured by a tritium nucleus they can induce inverse beta decay, a two-body decay where the electrons are monochromatic with an energy around 100 meV above the end-point of the tritium decay spectrum. To observe this signal above the enormous background from three-body tritium decay we need to measure the electron energy with unprecedented precision.
There are daunting experimental challenges. This research proposal addresses two major ones. First, there is the tritium-on-graphene target production and determination of its properties that are essential to have monochromatic electrons. To qualify the radiopurity and backgrounds we will develop novel field effect transistors (FETs) based active pixels on a graphene substrate. Graphene has unique properties which make it potentially superior to silicon for particle detection. In principle, the absorption and/or desorption of a single tritium atom can be detected in a measurable change of its resistance.
The second challenge is a novel RF detection technique to provide a single electron energy estimator while leaving it nearly undisturbed. We need to detect the RF signal of 1fW in a time of around 300 microseconds to provide an estimate of the initial electron energy with 0.1% precision. Detection of the relic neutrinos would be of similar importance as the discovery of the cosmic microwave background, for which two Nobel Prizes have been awarded, and provide us with a unique image of our Universe one second after the Big Bang.
