The award responds to US Department of Energy SBIR Topics FY2019,
Phase 1, Release 1, August 13 2018, Topic: 30. a. (2) SRF cavity joining
techniques that create vacuum seals without resorting to the use of
bolted flanges in order to minimize particulates.
​
This work validated a System that removes the greatest source of
particle generation in the Superconducting Radio Frequency Cavity
assembly clean room – the rubbing between bolt and nut fasteners –
and substitutes highly sprung “C” shaped spring clamps.  A Spring
Clamp System was designed, detailed, manufactured, developed and
tested. By sealing the flanges of an SRF cavity superfluid helium leak
tight, it prove the concept.  Specifically, the clamps produced the high
force necessary to crush a standard diamond section, hard aluminum
alloy gasket just as the bolts do. 
 
In use, the clamps are initially sprung open beyond their final sprung
state using Hydraulic Clamp Opener Mechanism and are slid over their
positions on the flanges in opposing pairs. This simultaneous clamping
avoids any tipping of the flanges about the metallic seal as when only
one clamp is applied.  When released, the clamp’s tips close the gap to
the flange and apply their substantial remaining spring force to press
the flanges together and crush the gasket. Additional pairs of clamps fill
all the positions. The Hydraulic Clamp Opener Mechanism is sealed
within a particle stopping enclosure while in the clean room and opened
the clamps sufficiently so that minimal rubbing of metallic surfaces is
involved in clamp application.

​Unfortunately, the Clamps developed as Model 1 are too big for
convenient application to cryomodules and the community has not
adopted them as a substitute for bolts. Model 2, at half the size and half
the spring force could possibly fit into SRF Cryomodule designs.
However, it uses a non-standard, soft aluminum gasket. It is very hard
to convince the SRF community to adopt a new gasket without extensive
successful use where a leak may result in extended down time and 6 to
7 figure expense in repairing the leak. Future work requires developing a

soft aluminum gasket that doesn’t have machining tares at its contact
edges and making enough joints without a leak such that the community
would adapt the clamp system as less risky than the particles generated
in the clean room by bolts and nuts.