Valving superfluid helium is a difficult task in cryogenic
apparatus design. As helium is chilled below the liquid state, helium
becomes "superfluid" or a quantum fluid which acquires some
unusual properties and obeys the laws of quantum mechanics more than classic
mechanics. The challenge for a valve designer is that the fluid
functionally has no viscosity. Therefore the closure must be
precise and very high seat to poppet pressures are required for the valve.
These pressures approach the elastic limit
of the seat material or poppet material. In order to activate a
well sealed mechanical valve a forceful long throw prime mover that generates
only microwatts of waste heat is required. TbDy actuators are ideal
for this task.
In order to achieve the force required to lift the poppet from the valve
seat, a TbDy magnetostrictive crystal is activated by a 1000 gauss field.
This field is
generated from a small high temperature superconducting (HTSC) coil.
Because the coil is superconducting no significant waste heat is generated
(at the microwatt level). A variation of the device uses a superconducting
flux tube to maintain an open or closed state indefinitely, without power
high temperature super conducting HTSC solenoid activation up to 77 Kelvin
a small dead volume on experiment side of 20 microliters
negligible heat of operation
high sphericity ball used to generated seat
flux tube option for steady state, current-off operation.
The Inventors and Developers
Valve Design: Robert Chave
Valve Development: Christian Lindensmith, JPL
HTSC Coil Development John Voccio, America Superconductor
NASA New Technology Award, NPO-20271: "Liquid Helium Valve
for Use at Cryogenic Temperatures with Magnetostrictive Actuation"
NASA New Technology Award, NPO-20502/0100b: "Superconducting
Flux Tube (SFT) Actuation of magnetostrictive Valve for Cryogenic Application"
United States Patent entitled " Magnetostrictive Actuation",
Serial Number 09/183,387, R. Chave, C. Lindensmith, J. Dooley, B. Fultz,
and M. Birsan, Application filed, Oct. 29, 1998 claiming the benefit of
U.S. Provisional Application No. 60/063, 991, filed Oct. 29, 1997
picture NASA Tech Briefs & RGC
first test in liquid nitrogen of valve
picture C Lindensmith