Bubble-Induced Vibration in Liquid Nitrogen Cryopump by Manoj Kumar Gupta

Guided by: Dr. D S Sharma and Dr V J Lakhera With Synopsis and CD 13EXTPHDE99

ABSTRACT: Gravitational Waves (GW) predicted by Einstein in 1915 were detected by
LIGO (Laser Interferometer Gravitational-Wave Observatory) on September
14, 2015. This is the first direct detection of GW and the first observation of a
binary black hole merger. The comparative low signal of the GW makes the
observation very challenging; however, continuous improvement in detection
equipment will open to observe more phenomenon of the universe.
Liquid Nitrogen Cryopump is one of the key components of LIGO system to
maintain the UHV and also the main source of noise due to bubbles. The
bubble induced noise is one of the noises that could distort the signal.
Cryogenic fluids are always in the boiling modes and inducing the bubble
noise continuously.
The present work is an attempt to theoretically inv estigate bubble induced
vibration and noise with the help of bubble dynamics. The configuration of
LN2 cryopump as circular concentric shell makes the investigation more
challenging. The departure force on the liquid nitrogen bubble is of the order
of 10-5 N, which provides the initial acceleration of ~2g. The bubble moves
through the liquid nitrogen and impacts the surface, which produces the
vibration and noise. The noise is analyzed in terms of force, acceleration,
velocity and the displacement. The induced noises are in the range -16 dB to -
146 dB. This work will open the new window for th e cryogenic fluid usability
for the vibration free environment. Hence it is a new emerging area of
investigation.