Process for growing large-size cesium iodide crystal by Czochralski method

Abstract

The invention discloses a process for growing a large-size cesium iodide crystal by a Czochralski method. The method comprises the following steps: charging, seeding, necking, shouldering and equal-diameter growth. The shouldering step is carried out by controlling the cooling rate of a shouldering stage to be 2-4 DEG C / 30min and the duration to be 30-40 min, continuously adjusting the heating power, keeping the heating power unchanged, and cooling the crystal at a low cooling rate of 2-4 DEG C / 2h under the condition that the rotating speed and the pulling speed are unchanged, wherein the crystals can be ended after growing to a preset length;, generally, the crystals are rapidly lifted until the crystals are completely separated from the melt, a slow cooling method is adopted to eliminatestress formed in the crystals during high-temperature growth, a power supply can be turned off when the working voltage is reduced to 50 V, and circulating cooling water is turned off when the furnace temperature reaches the room temperature. According to the process for growing the large-size cesium iodide crystal by adopting the Czochralski method, the cesium iodide is used for replacing sodiumiodide, and the Czochralski method is adopted for growth, so that the impact resistance of the detector is improved, and meanwhile, the cost is saved.

Description

technical field [0001] The invention relates to the technical field of preparation methods of cesium iodide crystals, in particular to a technique for growing large-sized cesium iodide crystals by pulling method. Background technique [0002] The space sodium iodide (NaI) crystal detector is composed of a crystal that captures cosmic gamma-ray bursts, a photomultiplier tube that multiplies and amplifies the cosmic gamma-ray burst signal, a high-voltage power supply that provides the working voltage of the photomultiplier tube, and a front-end electronic circuit. ; And sealed in a metal cylinder. However, due to the poor mechanical properties of sodium iodide (NaI) crystals and photomultiplier tubes, especially this detector uses large-scale flake-type sodium iodide (NaI) crystals (diameter 130mm, thickness 4mm) and large-scale photoelectric The multiplier tube (diameter 135mm, high-vacuum glass shell) has to pass the harsh space environment test and the 800g gravitational a...

AI Technical Summary

Problems solved by technology

However, due to the poor mechanical properties of sodium iodide (NaI) crystals and photomultiplier tubes, especially this detector uses large-scale flake-type sodium iodide (NaI) crystals (diameter 130mm, thickness 4mm) and large-scale photoelectric The multiplier tube (diameter 135mm, high-vacuum glass shell) has to pass the harsh space environment test and the 800g gravity acceleration impact test, which is quite difficult in mechanics and very expensive

In addition, sodium iodide crystals are fragile and have disadvantages such as poor impact resistance