32e - Large area time-of-flight diamond detector for heavy-ion beam diagnostics

Heavy-ion beams are used extensively in nuclear physics research advancing a deeper understanding of atomic nuclei and nuclear reactions, as well as in production of rare isotopes finding a wide acceptance in nuclear medicine. Advanced fragment separators for rare isotope beam production, and high-rigidity spectrometers for heavy-ion beam experiments require the development of advanced ion-beam diagnostics and controls, providing fast and precise identification of nuclear reaction fragments in a broad energy range on an event-by-event basis. Heavy-ion collisions produce multiple nuclear fragments with a large range of charge, mass, and kinetic energy. Today, the mass number is identified by time-of-flight measurements (TOF) using plastic scintillators which have a picosecond time resolution but are prone to fast radiation degradation. The increasing beam intensity capability of next generation facilities for rare isotope beams, such as the Rare Isotope Beam facility (FRIB) at MSU, demands the development of new detectors capable of sustaining the increasing rate capability. Heavy-ions have a very short range in detector material leading to high radiation damage and signal saturation in Si-detectors and scintillators under high-flux conditions. Thus, under intense CW heavy-ion beams, plastic scintillators and Si-detectors experience fast degradation, quickly rendering them unusable. The impact of this project is dependent on the unique properties of diamond which make it superior to silicon or silicon carbide detectors. Diamond has excellent radiation tolerance, can dissipate significant heat load, and its electronic properties are stable over a wide temperature range. Its high electron and hole mobility and low electric capacitance provides very fast signal response, down to sub-nanosecond range. Recent progress in synthetic diamond CVD growth significantly improved its electronic quality and reduced the cost thus making diamond devices increasingly commercially attractive. Here we propose to develop a large area thin PCD-detector of 60×60 mm2 size. To achieve that, we suggest a new CVD growth approach using a diamond “green body” made from sintered diamond powder as a growth substrate for CVD diamond, to produce large area e-grade PCD wafers of up to 3.5” diameter and 100-200 µm thickness with low stress and no bending. It will then be possible to fabricate large diamond detectors from a single PCD-plate, or to fabricate even larger mosaic PCD-detectors, reaching up to 120×120 mm2 in size. Single crystal diamond (SCD) sensors, though with smaller sizes, installed together with PCD-detectors will provide the necessary energy resolution of < 1%. Those large area TOF diamond detectors will have a picosecond time resolution time response (< 100 ps), high radiation stability and the ability to operate at elevated temperatures without cooling. Our prior work in using e-grade diamond for radiation detectors shows acceptable performance in many applications at significantly reduced cost. Calibration and benchmarking of the diamond detector prototypes will be carried out in collaboration with the FRIB facility at MSU.