Processing of the signals from the liquid-xenon calorimeter of the CMD-3 detector for timing measurements

Detecting near-threshold nucleon production reactions is one of the tasks that must be performed by the CMD-3 cryogenic magnetic detector operating at the Budker Institute of Nuclear Physics. Events of neutron-antineutron pair production, followed by antineutron annihilation, are detected by the detector calorimeters. The energy range differing by ∼25 MeV from the nucleon-producing threshold is the most interesting region for studying such events. At energies such as these, antineutrons annihilate in a cylindrical liquid-xenon calorimeter ≥5 ns after the beams collide. For reliable identification of these events, it is necessary that the flight time of these particles to the calorimeter be determined with an accuracy of 3 ns or better. The calorimeter is composed of a set of ionization chambers with the anode and cathode readout. The time of charge collection from the anode cells is 4.5 μs. Therefore, for the instant when a signal appears in the calorimeter to be determined with a required accuracy, a special signal processing method has been developed, with which it is possible to measure the arrival time of the calorimeter signals with the required accuracy in the real time mode. The prototype of the developed measuring channel has been tested. The test results basically satisfy the requirements: for the arriving signal equivalent to the deposited energy of 200 MeV, the measured time resolution is 3.1 ns, which is close to the calculated value of 2.9 ns.