![](media/image1.pct){width="5.973611111111111in"
height="0.4576388888888889in"}

71-030211-CLN-01

TO: DISTRIBUTION\
FROM: C NEUMEYER\
SUBJECT: RESISTIVE WALL MODE SYSTEM SCOPING STUDY

***\
Reference:*** 72-030123-JM-01 ***"***Preliminary Requirements For NSTX
Resistive Wall Mode And Error Field Feedback Coils And Power Supplies",
J. Menard, S. Sabbagh

[Summary]{.underline}

The purpose of this memo is to 1) identify the design issues, 2) develop
the design concepts and 3) outline the tasks related to the
implementation of a Resistive Wall Mode (RWM) and error field correction
system on NSTX.

Since a GA/PPPL collaboration has already deployed an RWM system on
DIIID it is advantageous for NSTX to build upon this experience and
utilize coil and power supply concepts already developed. Therefore a
starting point for this study is to determine to what extent the GA coil
and power supply designs can be adopted for NSTX duty.

It is concluded herein that the DIIID internal coil design can be
adopted on NSTX, but there are many challenges to in-vessel
installation. As an alternative, external coils can formed from power
cables (preferably 2 turns), but installation will again be challenging
due to small available space and many obstructions. Further study is
necessary to 1) quantify the performance difference (VALEN code) and 2)
quantify the cost/schedule difference between internal and external
coils. The information contained herein should provide the necessary
input to these steps.

The Robicon Switching Power Amplifiers (SPAs) used by GA appear to be
suitable for the NSTX application. However, one or more DC source power
supplies need to be identified. The PPPL Transrex power supplies could
be used, but their voltage does not match. The cost of procuring new DC
source power supplies needs to be traded off against the cost of
modifying one or more Transrex supplies to run at a lower voltage. It
does appear that the SPAs and DC source supplies can be installed at
FCPC without excessive DC line impedance. However, this needs to be
confirmed.

More effort is required to estimate the costs. However, some information
is already in hand regarding the cost of the main components, namely the
coil and power supplies. Based on the GA experience the GA style coils,
assembled in-vessel, would cost \$100K-\$150K per coil, so 6 coils would
cost \$600K-\$900K. If they could be assembled ex-vessel and passed
through a port then the cost could be significantly less, but this needs
to be determined. External coils formed from cable would be less
expensive, but their performance and feasibility needs to be
demonstrated.

The GA style SPA costs approximately \$150K. If a new DC source power
supply is required, then the cost of one 1.5MW unit which would feed one
SPA would be of order \$175K. For the SPA/DC source combination,
ultimately three units would be required, but initial operations could
commence with one unit. So, the initial cost for the power supplies,
might be of order \$325K, and for the final system, \$975K.

It must be kept in mind that the above costs are only those of the main
components. There will be other costs associated with other components
and the overall system integration.

Follow-on work outlined in this memo aims to develop a design concept
and cost estimate for the entire system.

#### Requirements

Per the reference memo and discussions with J. Menard et al the proposed
NSTX system requirements are summarized in the following table.

## RWM System Requirements Summary

  ----------------------------------- -----------------------------------
  Number of Coils                     6

  Coil Location                       Centered about midplane

  Coil Connections                    Diametrically opposite coils
                                      connected in anti-series forming 3
                                      independently controllable circuits

  Coil height                         Approximately equal to gap between
                                      passive plates \~ 1 m.

  DC Field at r=R0+0.6\*a             50 gauss

  AC Field at 1kHz, r=R0+0.6\*a       10 gauss

  Maximum Ripple                      +/- 2% of full load DC

  Pulse Length                        5 sec

  Repetition Period                   300 sec
  ----------------------------------- -----------------------------------

#### GA RWM System

# Coil Systems

GA started their RWM experimental program with a coil system consisting
of a set of 6 external coils centered about the mid-plane[^1]. The coils
were wound using 4 turns of 750MCM cable carrying up to 5kA for 10s.
These were designed to produce 30 gauss at the plasma edge. They were
located at approximately R=2.56m, or 0.22m from the plasma edge. See
figure 1. Note the support scheme, including the struts mounted off of
the VV on the right hand side of the figure.

![](media/image2.jpeg){width="4.711111111111111in"
height="3.533333333333333in"}

*Figure 1 -- DIIID External Coils*

More recently an internal coil system has been added which consists of
12 coils, 6 above and 6 below midplane[^2]. See figure 2.

![](media/image3.jpeg){width="4.6930555555555555in"
height="3.509027777777778in"}

*Figure 2 -- DIIID Internal Coils*

The coils are approx. 0.5 m tall by 2.0 meter wide, single turn water
cooled tubular copper conductors (14.4mm OD, 8.6mm ID) wrapped with one
half-lapped layer of polyamide (0.5mm (0.002") thickness Kapton)
insulation, a 1.7 mm thick Vespel spacer, and an additional layer of
Kapton tape, all encased in a 304SS tube (19mm OD). The coils are
capable of 7kA continuous with 5.5m/sec water cooling. Because a fully
assembled coil cannot be passed into the vessel, the coil is fabricated
outside the vessel in three pieces; a lower conductor assembly, an upper
conductor assembly and a 35 mm diameter concentric lead assembly. Leads
are brought out from two coils at a time through 10" diameter openings.

The design requires in-vessel joining of copper with three induction
brazes and six orbital welds of the stainless vacuum jacket. The coils
are installed under PFC tiles and are baked to 350°C. The design
provides a double barrier of copper and stainless steel against water
leakage into the machine. In order to detect water leaks in the copper
or leaks through the stainless into the vessel, the insulation space is
sealed in two places outside the vessel using machined polyamide and "O"
rings. During the initial bake of the vessel, this space is vacuum
pumped to remove moisture and gases that evolve. After cool down, dry
nitrogen gas is back filled to about 0.7 bar, and sealed off. The
pressure in this trapped volume is monitored to detect either water
leaks through the copper (higher pressure) or stainless sheath leaks to
the vacuum (lower pressure). During vessel baking, the cooling water in
the coils is replaced with dry nitrogen in order to limit oxidization of
the copper.

An extensive R&D program was conducted in '00 and '01 which led to the
installation of two prototype coils in DIIID. After their removal they
were hipot tested (to destruction) and found to withstand 5kV.

The 12 production coils were fabricated during the first 6 months of '02
and then installed during a 3 month opening. So far there have been no
leaks or any other problems with the coils.

The total cost associated with the fabrication and installation of the
12 production coils was \$2M, most of which was for labor costs. However
this figure includes costs for a significant amount of PFC tile removal,
modification, and re-installation, along with the relocation and
replacement of some magnetic diagnostics. So the cost associated with
the coils themselves was perhaps of the order of \$1.5-\$1.8M or approx.
\$100K-\$150K per coil.

If NSTX elects to install internal coils, the GA design could be
adapted, taking advantage of their prior R&D and experience. Furthermore
the coils could be fabricated by GA and they could lead in the
installation task, especially the in-vessel brazing and welding
operation. In fact the NSTX installation would be simpler and less
demanding due to the lower bakeout requirement (the coils would be
attached to the vessel wall at 150°C), simpler geometry (the coils on
the mid-plane would conform to the cylindrical shape of the vessel), and
lower fields (and forces). It may be possible to install the coils
through Bay K on NSTX (future NBI port) and avoid much of the in-vessel
fabrication, which would be a great simplification. Similarly, if the
coils were installed during a center stack removal then would be
possible to pass them into the vessel via the opening at the top of
NSTX. One additional challenge presented by NSTX is the CHI operation
which places a 1kV bias on center stack casing. But part of the voltage
can appear on the resistive grounded outer VV. So RWM coils mounted on
the outer VV of NSTX should be designed for a hipot of 2\*1+1=3kV. GA
tests of their insulation scheme, to destruction, indicate a dielectric
strength of 5kV.

*Power Supplies*

The power supplies consist of two parts, a rectifier DC source and an
IGBT chopper "Switching Power Amplifier" (SPA)[^3]. One DC source can be
connected to supply one or more SPA units.

The SPA choppers are subdivided into three parallel modules which can be
controlled separately and connected to three independent loads or
combined in parallel to drive one load. The DC inputs to the three
chopper modules are connected in parallel, and each to chopper module
input includes an input filter capacitor and output filter inductor. See
figure 3.

![](media/image4.pct){width="3.6618055555555555in"
height="4.082638888888889in"}

*Figure 3 -- DIIID DC Supply and SPA Configuration*

The SPAs were specified and procured by PPPL and manufactured by
Robicon. Cost per SPA is of order \$150K. The DC source supplies were
obtained from LLNL surplus. SPA characteristics are given in the
following table.

+-----------------------------------+----------------------------------+
| Pulse Current per Module          | 1.667kA                          |
+-----------------------------------+----------------------------------+
| Pulse Current (3 parallel module) | 5kA                              |
+-----------------------------------+----------------------------------+
| Pulse Duration                    | 10 sec                           |
+-----------------------------------+----------------------------------+
| Pulse Period                      | 180 sec                          |
+-----------------------------------+----------------------------------+
| Input Voltage                     | 300Vdc                           |
+-----------------------------------+----------------------------------+
| Switching Frequency               | 3.5kHz (first version)           |
|                                   |                                  |
|                                   | 7.0kHz (second version)          |
+-----------------------------------+----------------------------------+
| Input Filter Capacitance (3       | 0.2835 millifarad, 800V          |
| parallel module)                  |                                  |
+-----------------------------------+----------------------------------+
| Output Filter Inductor (per       | 11 microhenry                    |
| module)                           |                                  |
+-----------------------------------+----------------------------------+
| Output Filter Inductor (3         | 3.67 microhenry                  |
| parallel module)                  |                                  |
+-----------------------------------+----------------------------------+
| Cabinet Footprint Dimensions      | 6' wide x 6' deep x 8' tall      |
+-----------------------------------+----------------------------------+

The SPA IGBTs consist, in each bridge arm, 2 parallel IGBT devices
(EUPEC 400A/1200V).

If NSTX elects to procure the same SPA units then there is a possibility
that they could be operated at a somewhat higher voltage. The 300Vdc
number probably originated from the surplus LLNL supplies. The IGBTs and
caps can probably operate a bit higher.

For the DC source, it may be possible to utilize PPPL Transrex
rectifiers which at present produce a DC voltage of 1012.85Vdc at
alpha=0. It would be necessary to either supply the Transrex units with
a lower AC input voltage (e.g. 4.16kV would yield approx. 300Vdc) or
control them to a lower voltage with suitable accessories to prevent
overvoltage. Alternativly, new DC source power supplies could be
procured or obtained from surplus TBD.

[Analysis of Implementation Options]{.underline}

A spreadsheet analysis was performed for several NSTX design options.
This was helpful in identifying the issues. The GA internal and external
coil designs were also analyzed so as to provide a benchmark.

The complexities of the magnetics (mutual coupling to VV and resultant
eddy current effects) were not included in the model. However, skin
effect was accounted for. In arriving at the results in the GA cases,
the physical dimensions, circuit resistances and inductances, including
choke values, were based on information extracted from several GA
publications^1,2^,[^4]. In the NSTX cases the choke value was chosen so
as to limit the peak-to-peak ripple to 4% of the total amp-turns.

The following table provides a summary of the cases studied.

+-----------+----------+----------+----------+----------+-----------+
|           | GA       | GA       | NSTX     | NSTX     | NSTX      |
|           |          |          |          | External | External  |
|           | Internal | External | Internal |          |           |
|           |          |          |          | Coil     | Coil      |
|           | Coil     | Coil     | Coil     |          |           |
+-----------+----------+----------+----------+----------+-----------+
| #Turns    | 1        | 4        | 1        | 1        | 2         |
+-----------+----------+----------+----------+----------+-----------+
| Peak DC   | 5kA/     | 5kA/2    | 5kA/     | 5kA/     | 5kA/      |
| Current   | 5kA-turn | 0kA-turn | 5kA-turn | 5kA-turn | 10kA-turn |
+-----------+----------+----------+----------+----------+-----------+
| Rcoil     | R0       | 2.56m    | 1.68m    | 1.85m    | 1.85m     |
|           | +a=2.34m |          | (5/8"    | (6"      |           |
|           | (note 1) |          | inside   | outside  |           |
|           |          |          | VV wall) | VV wall) |           |
+-----------+----------+----------+----------+----------+-----------+
| dZcoil    | 1.02m    | 1.6m     | 1.0m     | 1.0m     | 1.0m      |
+-----------+----------+----------+----------+----------+-----------+
| Rpoint    | R0+0.6\  | 2.07m    | R0+0.6\  | 1.26m    | 1.26m     |
| (target   | *a=2.07m |          | *a=1.26m |          |           |
| for       |          |          |          |          |           |
| field)    |          |          |          |          |           |
+-----------+----------+----------+----------+----------+-----------+
| Br @      | 9.6e-3   | 6.65e-3  | 9.05e-3  | 6.98e-3  | 6.98e-3   |
| Rpoint    | gauss/   | gauss/   | gauss/   | gauss/   | gauss     |
| (note 2)  | amp-turn | amp-turn | amp-turn | amp-turn | /amp-turn |
+-----------+----------+----------+----------+----------+-----------+
| Br @      | 48.1     | 133.0    | 45.2     | 34.9     | 69.8      |
| Rpoint @  | gauss    | gauss    | gauss    | gauss    | gauss     |
| Peak DC   |          |          |          |          |           |
| Curr      |          |          |          |          |           |
+-----------+----------+----------+----------+----------+-----------+
| Br @      | 4.8      | 1.1      | 6.3      | 4.9      | 4.9 gauss |
| Rpoint @  | gauss    | gauss    | gauss    | gauss    |           |
| 1kHz      |          |          |          |          |           |
+-----------+----------+----------+----------+----------+-----------+
| Coil      | GA       | 750MCM   | GA       | 500MCM   | 250MCM    |
| Conductor |          | cable    |          | cable    | cable     |
+-----------+----------+----------+----------+----------+-----------+
| Coil      | Rd       | Rd       | R        | R        | R         |
| Impedance | c=1.33mΩ | c=1.64mΩ | dc=1.1mΩ | dc=0.5mΩ | dc=1.86mΩ |
|           |          |          |          |          |           |
|           | L=6.6µH  | L=128µH  | L=5.1µH  | L=5.25µH | L=22.6µH  |
+-----------+----------+----------+----------+----------+-----------+
| #Series   | 2        | 2        | 2        | 2        | 2         |
| Coils     |          |          |          |          |           |
+-----------+----------+----------+----------+----------+-----------+
| DC Feed   | R        | R        | 2x250'   | 2x250'   | 2x250'    |
| Cable     | dc=6.3mΩ | dc=6.3mΩ | 500MCM   | 500MCM   | 500MCM    |
|           |          | L=32.8µH | cable    | cable    | cable     |
|           | L=32.8µH |          |          | Rd       | R         |
|           |          |          | Rd       | c=35.1mΩ | dc=35.1mΩ |
|           |          |          | c=35.1mΩ |          |           |
|           |          |          |          | L=56.3µH | L=56.3µH  |
|           |          |          | L=56.3µH |          |           |
+-----------+----------+----------+----------+----------+-----------+
| SPA       | 3.5kHz   | 3.5kHz   | 7.0kHz   | 7.0kHz   | 7.0kHz    |
| Switching |          |          |          |          |           |
| Frequency |          |          |          |          |           |
+-----------+----------+----------+----------+----------+-----------+
| SPA       | 300V     | 300V     | 300V     | 300V     | 300V      |
| Voltage   |          |          |          |          |           |
+-----------+----------+----------+----------+----------+-----------+
| Lchoke    | 50µH     | 0        | 1.4µH    | 1.2µH    | 0         |
+-----------+----------+----------+----------+----------+-----------+
| Peak-peak | 5.7%/    | 1.9%/    | 4.0%/    | 4.0%/    | 4.0%/     |
| ripple    |          |          |          |          |           |
| (note 3)  | 2.8gauss | 2.5gauss | 1.8gauss | 1.4gauss | 2.8gauss  |
+-----------+----------+----------+----------+----------+-----------+

Notes:

1)  GA Internal coils consist of 2 sets, one above and one below mid.
    This radius chosen to simulate such coils using 1 set centered about
    the mid-plane.

2)  Br estimated based on planar, anti-series coil pair

3)  \% based on amp-turns

The following curves depict the dependence of current, field, and pulse
length on frequency for the various cases, considering the variation in
inductive impedance as well as the skin effect on resistance.

![](media/image5.pct){width="4.570138888888889in"
height="5.143055555555556in"}

*Figure 4 -- Available Peak Current (amp-turns) vs. Frequency*

![](media/image6.pct){width="4.9840277777777775in"
height="3.9451388888888888in"}

*Figure 5 -- Radial Field vs. Frequency*

![](media/image7.pct)

*Figure 6 -- Available Equivalent Square Wave vs. Frequency for Cable
Formed Coils*

Based on the analysis performed, the following observations are made.

1 -- All of the designs come close to meeting the requirement for 50
gauss under DC conditions. However they all fall short of the
requirement for 10 gauss at 1kHz, even with the simple model used which
does not simulate the demagnetizing effect of the eddy currents in the
VV. It appears that 10 gauss is only available up to around 500Hz.

2 -- The necessity of the additional choke, and higher switching
frequency for the new GA internal coils so as to keep the ripple down,
appears evident.

3 -- At least for the simple model used herein, the ripple requirement
dictates the minimum allowable circuit inductance for a given driving
voltage. This imposes, therefore, a fundamental limit on system
performance. It may actually be advantageous to reduce the base DC
voltage (nominally 300 volts) under certain conditions to reduce the
ripple.

4 -- The effect of the VV is probably very important in determining the
ripple response. Considering that the NSTX VV is 5/8" (0.625") thick
304SS, and the skin depth at 1kHz is only 0.550" in 304SS (resistivity =
7.7e-7 ohm-m), the VV may serve as an effective ripple filter, reducing
or eliminating the need for external inductance (choke).

5 -- If the VV does serve effectively as a ripple filter, then the noise
pick-up on in-VV magnetic diagnostics would be reduced in the case of
external RWM coils.

6 -- For NSTX, it would appear that the resistive and inductive
impedance of a cable run from the NTC to FCPC, assumed here to be 250',
can be tolerated, allowing the equipment to be installed at FCPC. If
closer study finds too small a margin in this regard, perhaps the DC
source voltage can be increased above 300V to compensate.

7 -- For the cable formed coils (the GA external coil from 4 turns @
750MCM, the NSTX external coil from 2 turns @ 250MCM, the NSTX coil from
1 turn @ 500MCM) the available pulse length (equivalent square wave) is
a function of frequency. For the 500MCM and 750MCM conductors, the
allowable pulse length at peak DC current exceeds 5 seconds with a 300
second repetition rate (rated NSTX pulse length and duty factor).
However, if a 250MCM cable is used (e.g. to conserve space and allow a 2
turn external coil to be formed) then the pulse length at the low end of
the frequency range would be less than 5 seconds as shown in figure 6.

8 -- Since the water cooled GA conductor is designed for 7kA continuous
then, as long as the DC feeds, etc., are 500MCM or larger, then the RWM
could run at rated current for the full 5 second pulse.

9 -- The net field available from 3 coil pairs will be higher than that
available from one. Figure 7 shows the spatial variation of Br (at
r=R0+0.6\*a) on the mid-plane for the case of the 1 turn NSTX external
coil when all three coil pairs are identically operated. The ratio of
multi-coil to single coil field in this case is 2.37.

![](media/image8.pct){width="6.002777777777778in"
height="3.902083333333333in"}

*Figure 7 -- Spatial Variation of Br at r=R0+0.6\*a on Midplane for 1T
External Coil*

#### Installation Issues

Installation of either internal or external coils on NSTX will be
extremely challenging due to the limited space.

*Internal Coils*

Since there are 6 coils there will be pairs of vertical limbs every 60
degrees in the toroidal direction. Since the NSTX RF antennae span a 90
degree sector (associated with ports C, D, and E), there must be two
passages of vertical limbs in the antenna region. As can be seen in
Figure 8 there is insufficient room to pass the vertical limbs in the
gaps between the faraday shields and boron nitride shields. There is a
gap, however, of order 3/4\" between the inner wall of the VV and the
boron nitride mounting plate, on the outboard side of the box (note gap
on left side of figure 8). This gap could be increased by perhaps 1/4\"
by removing some of the material on the mounting plate. If the conductor
(assume GA conductor 19mm dia, approx 3/4\") was routed in this location
then the current center would be, at best, 3/4\"+1/4\"-(3/4\")/2 = 5/8\"
from the inside edge of the wall. The edge of the conductor would be
1/4\" from the wall.

![](media/image9.jpeg){width="4.079861111111111in"
height="2.720138888888889in"}

##### Figure 8 -- NSTX RF Antenna Assembly

Another potential interference exists with the NBI protective plates
which are centered at port H. See figure 9.

![](media/image10.jpeg){width="4.170833333333333in"
height="3.0708333333333333in"}

*Figure 8 -- NSTX NBI Protective Plates*

These plates consist of 1\" graphite tiles attached to 0.5\" SS backing
plates. There are four plates (2 x 2) \~20\" high by 26\" wide. The
radial gap to the VV wall is estimated by D. Loesser to range from
2.5-4.0\".

Finally, there may be interferences with the heating/cooling tubing
associated with the passive plate sytem.

Based on these considerations it seems that the best orientation for the
RWM coils would be 6 spans as follows: B-D, D-F, F-H, H-J, J-L, L-B.
Coil leads would, presumably, be brought out via penetrations in
existing port covers. But it is concievable that new penetrations could
be created, e.g. on the midplane in the gap between existing midplane
ports.

The feasibility of in-VV coil installation needs to be confirmed, and
the extent of tasks (e.g. modifying/relocating other parts) needs to be
quantified.

# External Coils

An external coil system could be installed using the route presently
taken by the locked mode sensor coils. The horizonal limbs of the coils
would follow the bore of the PF5 coils and could be supported from same.
The vertical limbs could perhaps use the PF5 U/L support struts for
mechanical support. However, the space is extremly tight and congested.
It is unlikely that an ideal picture frame shape could be realized. The
effect of non-ideal coil configuration would need to be addressed.
Because of the superior performance, a 2 turn system would be preferred,
if it can fit. The coils would be formed using 250MCM, 600V power cable
which has an OD of 0.92 inches and a minimum bend radius of
4\*0.92=3.6".

*Coil Supports*

The RWM coils, whether inside or outside the VV, will experience EM
forces due to interaction with the TF, and the poloidal field from the
PF coils and plasma. The forces need to be calculated and the support
system designed accordingly.

*Power Supplies*

It appears that the inductance and resistance of a 500MCM cable run from
FCPC to the NTC, assumed 250', is tolerable in terms of circuit
performance. This means that the SPA and DC source power supplies could
be located in FCPC. On the other hand, the SPA power supplies could be
located in the NBPC building at the present location of the workshop
mezzanine. The cable run exposed to the high frequency current would
then be reduced to perhaps 100'. However it is likely that the DC source
power supplies need to be located at FCPC due to the high AC power input
(3\*5kA\*0.3kV=4.5MW) and the possibility of use of one or more of the
Transrex units.

[Implementation Plan]{.underline}

NSTX Physics would like, ideally, to install the RWM system during the
summer '03 opening. This of course depends on funding availability, and
feasibility of completing the work during the available time (the in-VV
coils may prove impossible because of this). To reduce initial cost
impact, the power supply system should be divided into two stages. The
first consisting of one SPA and one DC source power supply, and the
second stage adding two more SPA units and, if necessary, two more DC
source units.

[Job Planning]{.underline}

In order to develop a plan for the job, cost and schedule estimates need
to be performed. The following table lists the tasks to be performed,
along with proposed assignments. It would be highly desirable to develop
an estimate by March 15, 2003. The estimate should include M&S, labor,
and minimum calendar time to accomplish each task.

  ----------------------------------------------------------- --------------
  Task                                                        Assignment

  Compare performance of in-VV vs. ex-VV (1T and 2T) coils,   J Bialek
  including power supply response model                       

  Estimate forces on coils                                    C Neumeyer

  Assess feasibility and cost of in-VV coils                  L Dudek

  a\. Interference with RF antenna system                     

  b\. Interference with NBI protective plate                  

  c\. Interference with passive plate cooling lines           

  d\. Attachment technique                                    

  e\. Lead penetrations                                       

  f\. Fabrication/assembly tasks (can coils be passed through 
  bay K, other modifications/interferences)                   

  Estimate costs to fabricate in-VV coils                     P Anderson
                                                              (GA)

  Assess feasibilitiy and cost of ex-VV coils (preferrably    G Labik
  2T)                                                         

  a\. Routing                                                 

  b\. Method of support                                       

  c\. Extent of deviation from ideal rectangular shape        

  Develop concept for power suppl y design                    S Ramakrishnan

  a\. Identify DC source                                      

  b\. Select location(s) for SPA and DC source(s)             

  c\. Develop design of DC circuit including cable runs,      
  disconnect/grounding switches                               

  d\. Develop protection/interlock design                     

  Model power supply performance using PSCAD, include model   R Hatcher
  of coupling to VV                                           

  Develop concept for control system (interface with existing R Marsala
  Sky PSRTC/PCS)                                              
  ----------------------------------------------------------- --------------

cc: T Egebo J Menard M Ono M Peng

A Von Halle M Williams

[^1]: "Resistive Wall Mode Feedback System on DIIID", J. Scoville et al,
    18^th^ SOFE, Albuquerque, Oct. 1999

[^2]: "Design, Fabrication, Installation and Testing of In-Vessel
    Control Coils for DIIID", P. Anderson et al, 22^nd^ SOFT, Helsinki,
    Sept 2002

[^3]: Operating & Maintenance Manual, PU PO#S-04108-G, Robicon
    SO#1-64739

[^4]: "Modeling and Design of A Resistive Wall Mode Stabilization System
    with Internal Field Coils In DIIID", G. Jackson et al, 44^th^ APS,
    Orlando, Nov. 2002