Superconducting busbars

[jonmaddock]

In GitLab by @mkovari on Feb 2, 2021, 17:35

I believe that PROCESS assumes that the busbars for TF and PF coils are resistive. It has been suggested that HTS could be used to carry the current all the way to the power supply, which would save the power dissipated in a resistive busbar.

For example,

 TF coil resistive power (MW)                                             (rpower)                  6.254E+00  OP 
 TF coil inductive power (MVA)                                            (xpower)                  1.817E+01  OP 
 Aluminium bus current density (kA/cm2)                                   (djmka)                   1.250E-01     
 Aluminium bus cross-sectional area (cm2)                                 (albusa)                  4.529E+02  OP 
 Total length of TF coil bussing (m)                                      (tfbusl)                  3.373E+03  OP 
 Aluminium bus weight (tonnes)                                            (albuswt)                 4.125E+02  OP 
 Total TF coil bus resistance (ohm)                                       (rtfbus)                  1.951E-03  OP 
 TF coil bus voltage drop (V)                                             (vtfbus)                  1.105E+02  OP 

Any volunteers @ajpearcey @jmorris-uk @asbrown ?

[jonmaddock]

In GitLab by @skahn on Feb 4, 2021, 13:38

This is also my point of view.

The STEP runs are making HTS assumption setting a null resistivity for the bus bars.
An apropriate modelling of HTS bus bars may however beneficial.

[jonmaddock]

In GitLab by @mkovari on Nov 1, 2021, 10:46

As an aside, in ITER:

Feeders to the coils include the superconducting busbars, cryogen service lines, and
instrumentation cables. These feeders run from individual coil terminals inside the cryostat,
through cryostat feedthroughs (CF) and into coil terminal boxes (CTBs) or structure cooling
valve boxes (SCVBs). These boxes are located outside the cryostat and bioshield, in the
tokamak galleries which are accessible for hands-on maintenance.
...
The interface between power supplies and the magnets occurs at the CTBs where the
transition is made from superconducting busbars to room temperature (water-cooled
aluminium) busbars.

However, a power plant would probably have superconducting busbars all the way back to the power supplies.

[jonmaddock]

In GitLab by @mkovari on Nov 23, 2021, 08:25

See also Technical and economic feasibility study of high-current HTS bus bars for fusion reactors.

[mkovari]

We already have an input rhotfbus: 'TF coil bus (feeders) resistivity (ohm-m)'. Anyone can just set this to zero if they want.

Except that there is a special fudge in the resistive coil routine to set the bus bar resistivity equal to the TF conductor resistivity.
I have removed this, so this will change the results when resistive TF coils are used.

And the resistivity wasn't actually used, but instead a hard-coded value was used!

The resistivity of the PF coil bus bars was also hard-coded. Now changed: rhopfbus = 2.62D-8. This can be set to zero for superconducting bus bars.

And that of the CS bus bars - also now set to rhopfbus.

There are a lot of hard-coded assumptions in this part of the code - current density, length of bus bars, etc, which should be looked at some time.