Unlike most other MCP detector system, the RoentDek delay-line detectors such as DLD40 and DLD80 have a high ability to detect multiple particle hits (multi-hits) and analyze the position and time coordinates ("3d-detection") for each individual particle (hit).
However, if the relative arrival time (timely pulse pair distance) between two individual hits is of the order of the electronic pulse duration in the front-end electronics or below, the information on these hits might be lost or become ambiguous. Furthermore, the pulse-pair resolution limit (pulse pair dead time) of the used multi-hit TDC can impose another limitation on the acceptable timely pulse pair distance, e.g. for the RoentDek detector system with multi-hit TDC the pulse pair dead time is 10-15ns.
If two hits are closer in time they can still be recovered if the relative distance in x and y position exceeds a certain value. For details please follow this link.
Of course these consideration are also valid for a particle shower with more than two hits. Then the smallest timely pulse pair distance between any two hits applies for the above considerations.
To improve the multi-hit ability in the region below 10ns timely pulse pair distance RoentDek has introduced a delay-line detector system with the novel Hexanode (patents pending). It is similar in many respects to the standard DLD detector systems, but the Hexanode has a third independent delay-line layer, i.e. three delay-line layers are mounted with a relative angle of 60°. Signals from any two of the layers are sufficient to give a performance according to the standard DLD detectors (with two perpendicular delay-line layers) as described above, but:
It can be shown that by having a redundant third delay-line layer a complete and unambiguous recovery of multi-hits (with two or more particles) can be done if the relative timely OR spatial relative distance between any two hits is above the pulse-pair dead-time Dpp or Dpp × v^, respectively.
