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Abstracts
P2.15
Exploding and Imaging Bubbles in Superfluid Helium
Yadav Neha(1), Vadakumbatt Vaisakh(1), Maris Humphrey J.(2), Ghosh
Ambarish(3)
1)Indian Institute of Science, Department of Physics, Bangalore, India 560012
2) Brown University, Department of Physics, Providence, Rhode Island 02912
3) Indian Institute of Science, Center For Nano Science And Engineering,
Bangalore, India 560012
An electron bubble in liquid Helium-4 under saturated vapour pressure becomes
hydrodynamically unstable at a pressure more negative than-1.9 bars, which
can be easily achieved with focused sound waves. Here, we report on imaging
the cavitation of an electron bubble at 30000 frames per second, which reveals
that the bubbles can grow to as large as 1 mm within 2 ms of the cavitation
event. As revealed from our numerical simulations, the inertia of the bubble wall
during cavitation plays an important role in determining its maximum size. The
dependence on temperature and static pressure within the experimental chamber
will also be discussed.
P2.16
NANO-SIZE INHOMOGENEITY SUBSTRATE ANALYSIS USING
SURFACE ELECTRONS OVER SUPERFLUID HELIUM FILM
Bezsmolnyy Yaroslav, Nikolaenko Viktor, Sokolov Svyatoslav
B.Verkin Institute for Low Temperature Physics and Engineering of NAS of
Ukraine, Department of Physics of Quantum Fluids and Crystals, Prospekt
Nauky, 47, Kharkiv 61103, Ukraine
The quality of the substrate is a crucial in building of a quantum system.
The surface electrons (SEs) over helium film with thickness d on substrate
can be a good tool to analyze the surface. The mobility of SEs is limited by
interactions with the helium atoms in gas, with ripplons and by surface roughness:
m
−
1
=
m
−
1
c
+
m
−
1
im
(
m
c
and
m
im
are mobilities of SE for ideal and real substrate).
The variation potential from substrate is
δv
≈ −
Q
d
e
2
4
π
0
Z
πξ
A
A
Z
1
/
2
e
−
2
πZ
A
(0.1)
(
Z
is distance of SE from the substrate,
ξ
and
A
are effective amplitude and
period of inhomogeneities). At
A
≈
z
≈
d
≈
10
−
5
cm (z is distance from liquid
helium surface)
δV
≈
10
−
3
K
and at
z
≈
d
≈
A/
2 the
δV
≈
1
K
that leads to
decreasing SEs conductivity. We suppose the activation energy can be applied
instead of value
δV
. Here we propose innovation method providing a uniformity
of d by accurate horizon of the cell and using electro-mechanic driver with plunger
to adjust the liquid level.
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