Hamahoto develops the world’s largest photodiode array and establishes mass production system for HL-LHC experiment

On February 14, Hamamatsu Photonics Co., Ltd. (Hamahoto) launched the “CMS experimental device” in the “High Luminous LHC (HL-LHC) experiment” which is an improvement of the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN). announced that it has developed a photodiode (PD) array “8-inch pixel array detector”, which is the world’s largest photodiode (PD) array for high-energy physics applications, and has established a mass production system. bottom.

At the same time, it was announced that full-scale supply for the experimental equipment will start from February 27, and that a total of 27,000 units will be delivered by around the summer of 2025.

Approximately 30 Japanese research institutes and companies are participating in the construction and operation of CERN’s LHC, which is known for detecting the Higgs boson in 2012, among others. As equipment for the LHC, the company has developed and delivered a silicon strip detector, which is a particle track detector, and a photomultiplier tube and avalanche photodiode, which are calorimeters that measure radiation energy.

At CERN, we are currently conducting the HL-LHC experiment, in which the collision frequency between protons (protons are a type of hadron) has been increased compared to the conventional LHC experiment, with the aim of making even more precise measurements of the Higgs boson and detecting dark matter, an unknown substance. Preparations are underway to implement In this experiment, it is possible to obtain more data by increasing the collision frequency. However, the energy of the generated radiation also increases at the same time, so the PD array used to measure the energy is required to have high radiation resistance and a large area. Suppose that you have been working on the development of a large-area PD array.

This time, they have successfully developed an 8-inch pixel array detector as a highly radiation-tolerant PD array that is the world’s largest class for high-energy physics applications that measures the energy of radiation such as gamma rays and electrons.

PD arrays lose sensitivity when exposed to radiation. This decrease in sensitivity can be suppressed by applying a high voltage, but this in turn increases the risk of damage. In the HL-LHC experiment to reproduce the state of the early universe, the amount of radiation that passes through this product is equivalent to 1.5 quadrillion neutrons per 1 cm 2 . was required to be maintained.

Until now, the company had succeeded in prototyping a large-area PD array based on a 6-inch wafer with high radiation resistance that could operate even when a voltage of 800 V was applied. Suppose that a further increase in area was required.

This time, with the aim of using wafers with a larger area as the material, we will introduce new manufacturing equipment that can handle 8-inch wafers, and at the same time, apply the manufacturing technology for optical semiconductor elements that we have cultivated so far. By reviewing the conditions from scratch, we succeeded in improving the uniformity of the thickness of the film formed on the wafer and the concentration of impurities. As a result, the area of ​​the PD array has been increased (approximately twice that of the conventional one) while maintaining the same high radiation resistance as the conventional one.

In addition, by launching a new dedicated inspection system capable of inspecting all channels of the PD array, we will be able to mass-produce the same product that supports the high radiation resistance and large area required for the HL-LHC experiment. Suppose it is established.

Full-scale supply of this product is scheduled to start on February 27, 2020, for the CMS experimental equipment in the HL-LHC experiment. The company explains that it is expected to contribute to new research such as precision measurement and the search for dark matter.

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