The present invention relates to a vacuum bifurcation chamber for splitting the vacuum
space over the vacuum jacketed line of a cryocooler connecting the application side of
High temperature superconducting (HTS) machine.
BACKGROUND OF THE INVENTION
A cryocooler is used for achieving and sustaining desired cryogenic temperature in HTS
machines. The cryocooling operation is carried out in a closed loop process. In this
process cold gas is transferred from cryocooler to HTS machines while warm gas is
collected from HTS machine and given back to cryocooler. Cryocooler has a vacuum
jacketed line for transfer and collection of cryogen along with flexibility of mechanical
connections. Usually the vacuum jacketed line is connected to the rotating coupling of the
HTS machine. This rotating coupling connects the stationary cryocooler and rotating
superconducting rotor of the HTS machine. HTS machine has many weld joints and
pipings carrying the cryogen. These cryogenic pipings carry pressurized cryogen inside
the rotor of the HTS machine over which there is a vacuum. This complexity makes it
susceptible to cryogen leak and contamination of the vacuum space. Contamination of
vacuum in the vacuum jacketed line can lead to deteriorated cryocooling performance or,
in some extreme cases, failure of cryocooling process.
APPLICANTS ADMITTED PRIOR ART
1. Patent no: EP913023B1
A rotor assembly for use within a superconducting electric motor includes a
superconducting winding formed of high temperature superconductor and during
operation, generates a flux path within the rotor assembly; and a high permeability
magnetic material, positioned within at least a portion of the flux path so as to decrease
the overall reluctance of the flux path. The rotor assembly may include a support
member having an internal volume and formed of a non-magnetic, high-strength
resilient. The support member supports on its outer surface the superconducting

winding and within its internal volume, the high permeability magnetic material. The
magnetic material may be in the form of a core member to provide the low reluctance
portion to the flux path generated by the superconducting wading.
2. Patent No. WO0049703A9
A high temperature superconducting rotor for a synchronous machine includes a high
temperature superconducting field winding, a field winding support concentrically
arranged about the high temperature superconducting field winding, and a thermal
reserve concentrically arranged about the field winding support. The thermal reserve
includes a thermally conductive material. The material is either electrically conductive,
for example, aluminum, or electrically non-conductive, for example, ceramics such as
beryllium oxide or alumina. The thermal reserve material includes segmentation in a
direction normal to the rotor axis, along the rotor axis, neither, or both. The rotor
includes a banding concentrically arranged about the thermal reserve. The banding
includes an electrically conductive material, for example, steel, an electrically non-
conductive material, for example, Kevlar, or both. The rotor incudes an outer layer
concentrically arranged about the thermal reserve. the outer layer includes a thermally
non-conductive material.
3. Patent no :EP913023A1
A rotor assembly for use within a superconducting electric motor includes a
superconducting winding formed of high temperature superconductor and during
operation, generates a flux path within the rotor assembly; and a high permeability
magnetic material, positioned within at least a portion of the flux path so as to decrease
the overall reluctance of the flux path. The rotor assembly may include a support
member having an internal volume and formed of a non-magnetic, high-strength
resilient material. The support member supports on its outer surface the
superconducting winding and within its internal volume, the high permeability
magnetic material. The magnetic material may be in the form of a core member to
provide the low reluctance portion to the flux path generated by the superconducting
winding.

4. Patent No. US20120274161A1
Provided are a rotor core, a method for cooling a rotor core, and a superconducting
rotating machine, capable of effectively and uniformly cooling superconducting coils
without causing cold brittleness in an extremely low temperature. The rotor core, which
is made of a substantially hollow cylindrical member of nonmagnetic material, has a
cylindrical cavity defined therein and extending in the longitudinal axis of the member.
Helium gas is delivered in the rotor core from the proximal to distal sides and vice
versa, which ensures a uniform cooling of the rotor core. This also ensures a uniform
and effective cooling of the superconducting coils.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a vacuum bifurcation chamber for
splitting the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine.
Another object of the invention is to propose a vacuum bifurcation chamber for splitting
the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine, which restricts the
minimum helium leak rate (higher than 10-9 mbar-litre/sec) through the vacuum bifurcation
chamber.
A still another object of the invention is to propose a vacuum bifurcation chamber for
splitting the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine, which achieves a
vacuum of magnitude 10-7 mbar or higher in the vacuum bifurcation chamber.
Yet another object of the invention is to propose a vacuum bifurcation chamber for splitting
the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine, which ensures
minimum pressure drop across cold and warm gas pipings.

Another object of the invention is to propose a vacuum bifurcation chamber for splitting
the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine, which ensures
minimum heat leak into the chamber in from atmosphere.
A further object of the invention is to propose a vacuum bifurcation chamber for splitting
the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine, which is configured
to maintain the mechanical integrity of the chamber in a steep internal pressure gradient
environment (from 10-7 mbar vacuum level in the chamber to 4 bar pressure cryogen in
the cold gas pipe).
A still further object of the invention is to propose a vacuum bifurcation chamber for
splitting the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS) machine, in which a buckle-
free extension cylinder and flanges provided to sustain an external environmental
atmospheric pressure of 1 bar and internal vacuum of 10-7 mbar.
Still another object of the invention is to propose a vacuum bifurcation chamber for
splitting the vacuum space over the vacuum jacketed line of a cryocooler connecting the
application side of High temperature superconducting (HTS, which achieves flexibility in
operation of the cryocooler by connecting it with one application after the other without
disrupting the vacuum of the vacuum jacketed line.
SUMMARY OF THE INVENTION
The present inventors recognized that one of the solutions to the prior art can be
designing and disposition of the vacuum jacketed line from that of rotating
superconducting rotor of the HTS machine. But, a separated vacuum along with a
bifurcation chamber poses many challenges to be addressed. Firstly, the vacuum
chamber must not add much heat load to the basic system, otherwise it will add more

difficulties in an already process. Further, the chamber must also maintain required
vacuum, but with a minimum leak rate. The mechanical integrity of the basic system
should also be looked into with caution because the environment, where this bifurcation
chamber is employed, has a steep pressure gradient from 10-7 mbar vacuum level in the
chamber to 4 bar pressure cryogen in the cold gas pipe. However, an addition of a
bifurcation chamber will definitely give advantages to complete system if challenges are
met holistically.
The addition of a bifurcation chamber splits the vacuum space of vacuum jacketed line of
the cryocooler from the HTS machine application side. This will enable the uninterrupted
operation of the cryocooler irrespective of vacuum level of the HTS machine side. Also
the contaminated vacuum of HTS machine will not hamper or affect the operation of the
cryocooler. Another advantage is to get a flexibility in operation of the cryocooler by
connecting it with one HTS application after the other without disrupting the vacuum of
vacuum jacketed line, which transfers the cryogen from the cryocooler to HTS application
and collects it back from the HTS application in a closed loop operation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Vacuum Bifurcation Flange along with Extension Cylinder
Figure 2 Complete Vacuum Bifurcation Chamber
Figure 3 Integration of Vacuum Bifurcation Chamber with Cryocooler and HTSC Machine
Application
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig 1 represents a vacuum bifurcation flange 101 along with an extension cylinder 102.
The vacuum bifurcation flange has two extension pipes 104,107 (one for cold gas 104
and another one for warm gas 107) welded to it in same plane of the flange. These two
extension pipes have one gas adopter each 105,106 to weld it to threaded connections.
The vacuum bifurcation flange has a groove 109 for placing O-ring to maintain the vacuum

inside the vacuum bifurcation chamber. Six tapped holes 110 are also provided in the
each side of vacuum bifurcation flange to fasten two split rings onto it. The extension
cylinder is welded to vacuum bifurcation flange on one side, while the other side of it is
welded to cryocooler connecting flange 103. The cryocooler connecting flange also has
a groove 108 for placing O-ring to maintain the vacuum inside the vacuum bifurcation
chamber. Six tapped holes 111 are also provided in the rear side of cryocooler connecting
flange to fasten two split rings onto it.
Fig.2 represents the complete vacuum bifurcation chamber along with various pipings
and threaded connections. The two adopter 208,211 of extension pipes 104,107 are
further welded to two another secondary adopters 209,212. These secondary adopters
are each welded to threaded male connections 210,213 before placing female nuts over
it to connects to HTS application side. The two adopter of extension pipes are also welded
to cold gas and warm gas pipes 205,207. Cold gas is transferred from cryocooler to HTS
application while warm gas is collected from HTS application and given back to cryocooler
in a closed loop operation. These cold and warm gas pipes are each welded to threaded
male connections 204,206 before placing female nuts over it to connect to cryocooler
side.
Fig. 3 represents the integration of vacuum bifurcation chamber 301 with cryocooler
vacuum jacketed line 302 and HTS machine application side 303. Cold gas is transferred
from cryocooler to HTS application while warm gas is collected from HTS application and
given back to cryocooler in a closed loop operation.

WE CLAIM
1. A vacuum bifurcation chamber for splitting the vacuum space over the vacuum
jacketed line of a cryocooler connecting the application side of High temperature
superconducting (HTS) machines, comprising:-
- a vacuum bifurcation flange (101) having a groove (109), and at least six
tapped holes (110) configured on rear side of the flange (101),
- a cryocooler connecting flange (103) having a groove (108), and tapped holes
(111) of corresponding number of that of the bifurcation flange (101),
wherein the bifurcation flange (110) is provided with an extension cylinder (102)
and extension pipes, one each for cold gas (104) and warm gas (107) welded in
same plane of the flange (101), wherein each of the extension pipes (104,107)
having one each primary gas adaptor (105,106) welded at the threaded connection
of the pipes (104,107),
characterized in that the two primary gas adaptors (105,106) are welded to two
secondary gas adaptors (209,212) at one end and to the threaded male connectors
(210,213,204,206) at the other end.
2. The vacuum bifurcation chamber as claimed in claim 1, wherein cold and warm gas
connections are made to the cryocooler and the HTS machine at both sides
(210,213;204,206).
3. The vacuum bifurcation chamber as claimed in claim 1, wherein O-rings of applicable
size and diameter are placed in grooves (109,108) of the vacuum bifurcation flange
(2101) and cryocooler connecting flange (103).
4. The vacuum bifurcation chamber as claimed in claim 1, wherein split rings are
fastened on to the vacuum bifurcation flange (101) and cryocooler connecting flange
(103) after placement of the O-rings.

5. The vacuum bifurcation chamber as claimed in claim 1, wherein the helium leak rate
is achieved less than 10-9 mbar-litre/sec through the vacuum bifurcation chamber
(301).
6. The vacuum bifurcation chamber as claimed in claim 1, wherein the vacuum of
magnitude 10-7 mbar or higher in the vacuum bifurcation chamber (301) is maintained.
7. The vacuum chamber as claimed in claim 1, wherein a miniscule pressure drop across
cold and warm gas pipings is obtained.
8. The vacuum bifurcation chamber as claimed in claim 1, wherein the mechanical
integrity and non-buckling parameters of the chamber (301) are maintained despite
steep pressure gradients in and around the chamber (301).