Time Differential Perturbed Angular Correlation Spectroscopy (TDPAC) is a Nuclear Solid State Technique where one uses the angular correlation between the directions of the consecutively emitted gamma rays (following the nuclear decay of an irradiated probe in the host material of study) to study the local hyperfine properties of the mentioned irradiated probe surrounded by the matrix of the host material. This technique relies on the (sub-nanosecond) precise measurement of the time intervals between the two relevant gamma ray pulses to accurately characterize the count rate ratio R(t), where information of hyperfine parameters is contained and extracted.  

 

Traditionally, TDPAC was done analogue, as the digitizer back then were not fast enough to provide an accurate timestamp of the gamma ray pulses required for TDPAC spectroscopy. With the advancement of the digitizer technologies, 2nd generation TDPAC devices such as DIGIPAC and KATAME was made, bottlenecked by the inadequate PCIe lanes of the servers back in the 2010s. They were characterized by having each digitizer being connected to an individual server, which is then controlled by a separate central server via local area network (LAN) communication. PACBit is the 3rd generation TDPAC spectrometer, designed to leverage upon the high amount of available PCIe lanes afforded by AMD's 3rd Gen (and beyond) Threadripper PRO solution, providing an all-in-one package (i.e. just a single server) designed for ease of use/maintenance, as well as eliminating latency issues caused by LAN.