Why do we angle the exiting quench pipe downwards?

The primary reason for angling the exiting quench pipe downwards is to prevent helium from being released straight up into the atmosphere. When a quench occurs, the supercooled helium gas escapes rapidly. If the quench pipe is directed upwards, the helium would disperse into the air, which could be hazardous, especially in populated or enclosed areas. By angling the quench pipe downwards, the gas is directed towards a specific area where it can dissipate safely, thus minimizing potential risks associated with the helium gas dispersing vertically.

While preventing rain and snow from entering the quench pipe is important for maintaining the integrity and function of the system, the main focus is on managing the gas release effectively. Animal safety may also be a consideration in certain environments, but it is not the primary reason for this design choice.

Therefore, the most accurate justification for angling the exiting quench pipe downwards is rooted in managing the release of helium gas safely and efficiently, making options related to environmental conditions or animal considerations secondary to the primary safety concern. Thus, the answer that captures the essence of this safety measure is the option that states preventing direct upward helium release is the critical factor.