Hirashin,
Please remember this rule:
"at" = "in" or "near"
"in" means completely within a clearly-defined boundary. This boundary is usually a building.
"at" means "within a clear-defined boundary" or "very near that clear-defined boundary".
A.
A1. Let's meet in the dormitory.
A2. Let's meet at the dormitory.
Example A1 means the meeting can only happen inside the dormitory building. Example A2 means the meeting can happen inside the dormitory building, in the dormitory courtyard, or on the sidewalk in front of the dormitory. We usually say example, A2, "Let's meet at the dormitory."
B.
B1. We landed in Haneda Airport.
B2. We landed at Haneda Airport.
In example B1, the airplane landed inside the airport terminal building! Or it can mean the people parachuted into a hole in the roof of the airport terminal building! Example B2 is usually the correct usage.
C.
C1. The weather in Haneda Airport is terrible.
C2. The weather at Haneda Airport is terrible.
Example C2 refers to weather anywhere within several miles of Haneda Airport. Example C1 refers to weather inside the airport terminal building! Example C2 is the correct usage. We never say example C1.
D.
D1. She works in Starbucks.
D2. She works at Starbucks.
Example D1 can only refer to work that is done inside the coffee shop building. But Starbucks baristas sometimes work outside, for example, to clean the windows. Starbucks managers sometimes have to go to another Starbucks to confer with another Starbucks manager. For this reason, we usually say D2.
E.
E1. I live in Chiba.
E2. I live at Chiba.
"At" adds a small feeling of ambiguity as to location. We cannot say, "I live at Chiba." This kind of ambiguity is impossible.
Now let's look at your example.
F. It is now used for experiments at research institutes such as JAXA.
Such experiments never happen completely inside research institute buildings. For this reason, we must say, "It is now used for experiments at research institutes such as JAXA."