Speaker
Description
The enhancement of time response in scintillator-based gamma-ray detectors is crucial for applications such as Time-of-Flight Positron Emission Tomography (TOF-PET) and experimental nuclear and particle physics. One promising approach to achieve this improvement is by utilizing Cherenkov radiation, which is emitted nearly instantaneously compared to traditional scintillation light. However, a major limitation of Cherenkov-based detection is the low yield of detectable photons, as most are emitted in the ultraviolet (UV) range, where many materials exhibit high absorption and reduced transparency.
To overcome this limitation, we propose the use of Redshifted Cherenkov Radiators (RCR). By introducing fluorescent dopants into liquid solvents, Cherenkov photons are shifted from the UV to the visible spectrum, where materials are more transparent and conventional photodetectors exhibit higher efficiency. This technique aims to increase the number of detected Cherenkov photons, ultimately leading to improved timing resolution in radiation detectors.
To evaluate the feasibility of this approach, we tested different liquid solvents, including octadecene (ODE), chloroform (CHCl₃), and dimethyl sulfoxide (DMSO), with POPOP as a wavelength-shifting dopant. UV absorption analysis confirmed that ODE exhibits the highest transparency in the UV range and the incorporation of POPOP led to an increase between 17% to 56% in detected Cherenkov photons, as shown in Figure 1 left, which compares the relative detection yield for different solvents with and without the wavelength shifter.
Time-correlated single photon counting (TCSPC) measurements indicated a slight degradation (~15%) in time response due to the re-emission process. However, coincidence time resolution (CTR) measurements with LYSO detectors, using the setup illustrated in Figure 1 right2, showed that the increase in detected photons compensates for this degradation. Consequently, further improvements in detector design to enhance Cherenkov photon detection could simultaneously improve light yield and time resolution, reinforcing the potential of RCR detectors for applications requiring maximized light collection.
The redshifting of Cherenkov photons using fluorescent dopants significantly enhances detection efficiency while maintaining competitive time resolution. The increased photon yield offsets the minor time degradation, making RCR technology a promising solution for high-performance TOF-PET detectors. These results indicate that further refinements in redshifting materials and detection optimization could push the limits of molecular imaging and precision timing applications.