Identification Of Reaction Product Mass By Microchannel Plate Detector

The reaction products produced in heavy-ion nuclear reaction are often complex and diverse.The open reaction channels in the nuclear reaction process are not unique,and the products produced will be diverse.Only by clearly identifying the various reaction products,can the information of products be accurately measured,such as energy,mass and other related information.Especially in the heavy ion nuclear reaction,the reactants involved in the reaction is heavier and has higher energy,and multiple reaction channels are opened.The reaction products are more complex in this case.In order to study such a large variety of complex reaction products,particle identification is necessary.The time-of-flight method has the advantage of simple experimental equipment,and is often used to identify the mass number of reaction products.At the same time,many detectors can use this method to identify reaction products.For example,semiconductor detectors can be used as time-stop detectors.In order to obtain a time detector with better performance,a better time-resolved time start and stop detector was developed based on the microchannel plate（MCP）.The time of flight of the product can be measured with a single microchannel plate detector in combination with other detectors such as semicon-ductor detectors,or with two microchannel plate detectors.Based on the microchannel plate,a position-sensitive detector has also been developed,which can reconstruct the flight trajectory of particles more accurately.The initial test of the rise time of the microchannel plate detector was carried out with a²⁴¹Amαsource.The rise time of the small-size microchannel plate detector（microchannel plateΦ26 mm）was about 450 ps,and that of the large-size microchannel plate detector（microchannel plateΦ45 mm）was about 600 ps.Measuring the time-of-flight of the prod-ucts with the two microchannel plate datectors,the inertial time resolution was 137.8 ps（FWHM）.In the experiments³²S+^90,96Zr,^112,124Sn,the microchannel plate detector and the silicon semiconductor detector were combined to measure the time of flight,and the mass of resolution of the products was 1.86 u,2.03 u,1.60 u and 1.84 u respectively.A microchannel plate detector array for measuring the mass of fission fragments was built in the target chamber of the Beijing HI-13 tandem accelerator R60°pipeline with a diameter of 1.2 m.The detector array consists of eight groups of microchannel plate de-tectors and two groups of three-layer silicon detector telescopes.The time resolution of the microchannel detectors was tested with a three-componentαsource,and the time resolution of each group of microchannel plate detectors basically met the experimental requirements.Using the²⁵²Cf fission source to test the mass resolution,the light and heavy fragments are well separated in the two-dimensional spectrum of the time-of-flight versus energy correla-tion.The mass distribution of the fission fragments obtained by the experiment is basically consistent with the evaluation value,and the mass resolution obtained by preliminary pro-cessing of the test data was 1.7 u.Wedge-shaped anode plates for position sensitive detectors have been improved using simple printed circuit board technology.Using the²⁴¹Amαsource to test the position-sensitive detector,the two-dimensional imaging distortion was small,the linearity was good,and the position resolution was better than 0.3 mm.The detector performance has met the requirements of the experiment.