Poloidal flux loops
There are a total of 27 poloidal flux loops. 8 flux loops are mounted to the top and 8 to the bottom shell pair, and 11 flux loops are mounted inside the center stack (Fig. 1).
Shell-Mounted Loops
Each shell-mounted poloidal flux loop has three output leads: a positive lead, a negative lead, and a center-tap tied to external ground through the LIMO shield/case. The loop itself is protected in a stainless tube which is insulated from the shells and shorted to vessel ground.
Estimated shell-mounted flux loop positions as of 2017:
| Upper |
Lower | |||
| Loop ID |
Machine R [cm] |
Machine Z [cm] |
Machine R [cm] |
Machine Z [cm] |
| 1 |
12.22 |
5.08 |
12.11 |
-4.6 |
| 2 |
14.48 |
19.61 |
13.98 |
-20.8 |
| 3 |
20.15 |
33.42 |
19.58 |
-33.18 |
| 4 |
28.87 |
39.33 |
28.71 |
-39.17 |
| 5 |
40.34 |
38.62 |
40.06 |
-38.54 |
| 6 |
53.94 |
29.41 |
54.04 |
-29.41 |
| 7 |
62.52 |
18.46 |
61.92 |
-19.65 |
| 8 |
67.67 |
8.24 |
68.18 |
-8.32 |
Acquisition
Shell-mounted
The shell-mounted flux loops pass out of the vacuum vessel through 19-pin Mil-C feedthroughs at upper and lower outboard ports in section C-D. Each loop is connected to integrator chassis 4, channels 1-8 (lower) and 9-16 (upper), and digitized in Helios channels 9-16 (upper) and 25-32 (lower). These channels are planned to be shared with the PCS. The diagnostic channels are stored in the LTX_B tree in .DIAGNOSTICS.MAGNETIC.FLUX_LOOPS.UPPER_SHELL:LOOP_X and .DIAGNOSTICS.MAGNETIC.FLUX_LOOPS.LOWER_SHELL:LOOP_X.
Centerstack
The centerstack flux loops are routed through a 25-pin D-sub connector at the outer edge of the centerstack bottom, below section D-E. Each loop is connected to integrator chassis 4 channels 17-27, and digitized in Helios channels 33-43. These channels are not planned to be shared with the PCS. The diagnostic channels are stored in the LTX_B tree in .DIAGNOSTICS.MAGNETIC.FLUX_LOOPS.CENTERSTACK:LOOP_XX.
Loop Voltage Monitor
There are also two toroidal loop voltage monitors.
Upper shell flux loop #1 (see Fig. 1) is split just before the integrator, with one branch passing through a 1/2 Vin voltage divider to Neos input 96, where it appears unintegrated in the tree as .DIAGNOSTICS.MAGNETIC:V_LOOP.
As of May 13th 2021, the loop voltage monitor has been switched to use lower shell flux loop #1 due to suspiciously anomalous V_LOOP signals. This will affect shots 102647 onward.
As of Oct. 4th 2018, documentation on the other loop voltage monitor is not available.
Related Pages
Diagnostics
Magnetics (Local): Reentrant array | Toroidal array | Saddle coils | Shell eddy sensors
Magnetics (Areal): Poloidal flux loops | Loop voltage | Diamagnetic loop | IP Rogowski
Spectroscopy: Thomson scattering | ChERS | X-ray spectroscopy | Spectrometry | Vacuum UV spectroscopy
Microwaves: Reflectometry | Interferometry
Physical Probes: HFS edge probes | LFS SOL probes | RFEA
Operational Diagnostics: Ion gauges | Coil current monitors | Thermocouples | RTDs
