The plastic scintillator is probably one of the most widely used organic detectors in nuclear and particle physics. Its mounting, operation and handling are relatively simple, and well-understood, and thus it is often equipped in the Time-Of-Flight (TOF) measurements.
A TOF resolution of about 100 ps is enough for most of the general-purpose applications, e.g. for particle identification of radioactive beam with mass number less than 100. However, in recent years there are increasing demands for ultra-fast timing-pick up detectors in high precision measurements. Here we take a TOF mass spectrometry (MS) as an example to illustrate the importance of time determination. The TOF-MS is known as one of the most efficient methods for mapping the nuclear mass surface for short-lived nuclei near the drip line. Currently the single-pass TOF-MS can achieve a mass resolving power of about 5000, and the dominant source is the time resolution of TOF measurements. For a typical flight time of about 500 ns, if the time resolution were improved from current 100 ps to about 10 ps, the final mass resolution of TOF-MS could in principle be enhanced by up to one order of magnitude. This corresponds to an uncertainty of about ±500 keV for the mass of a single nucleus with A ~ 50.
If succeed, the TOF-MS could significantly speed up the march towards mass measurements of the most neutron-rich nuclei with fairly good precision. The main motivation of present work is to develop a TOF system based on fast plastic scintillators for the TOF-MS measurement of heavy ions at relativistic energies of several hundred MeV/u.