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[National Spherical Torus Experiment]{.underline}

**NSTX**

GENERAL REQUIREMENTS DOCUMENT

NSTX-RQMTS-GRD-018

**Revision 2**

**December 8, 1998**

Prepared By:

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Charles Neumeyer

NSTX Project Engineering Manager

Approved By:

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Masa Ono Martin Peng

NSTX Project Director NSTX Program Director

+---------+--------+--------+-----------------------------------------+
| R       | Date   | CR     | Description of Change                   |
| evision |        |        |                                         |
+---------+--------+--------+-----------------------------------------+
| First   | 12     |        |                                         |
| Issue   | /10/96 |        |                                         |
+---------+--------+--------+-----------------------------------------+
| 1       | ~~3/   | 003    | 1.1.2.b, added Day 0 and Day 1          |
|         | 3/97~~ |        | categories; 1.1.2 c clarified           |
|         |        |        | diagnostics upgrades, added automatic   |
|         | 3/3/98 |        | GDC upgrade, added antenna upgrades;    |
|         |        |        | Table 1.1.2-1 clarified for up to 2     |
|         |        |        | beamlines, clarified PFC/VV req\'ts for |
|         |        |        | NBI upgrade; revised fig 1.1.3.1; added |
|         |        |        | 1.1.3 c and Table 1.1.3-2; added 1.1.4  |
|         |        |        | c & d; 1.2.1 g & h revised wording;     |
|         |        |        | 1.2.2 a deleted reference to S-1 domes, |
|         |        |        | f added isolation & grounding req\'ts   |
|         |        |        | for CHI; 1.2.3.1 c deleted req\'t for   |
|         |        |        | galvanically separate PF circuits;      |
|         |        |        | 1.3.1 a deleted req\'t for shared RF    |
|         |        |        | usage w/PBX-M, b changed nomenclature   |
|         |        |        | to refer to 12 strap antenna, cdeleted  |
|         |        |        | requirement for subsets of sources at   |
|         |        |        | different frequencies; Table 1.5-1      |
|         |        |        | complete revision; added 1.4.5 GDC,     |
|         |        |        | noted Day 1 Req\'t; 1.5 b changed AC    |
|         |        |        | rms to DC; 1.6.3 b added PF3 bipolarity |
|         |        |        | requirement; 1.7.Noted Data Acquisition |
|         |        |        | System Day 1 Req\'t, d Noted Day 1      |
|         |        |        | Req\'t; 2.1.2.3 c added 25 year life    |
|         |        |        | req\'t for infrastructure changes; adde |
|         |        |        | 2.1.2.3 e & f; 2.1.3.1 added            |
|         |        |        | \"Upgrade\"; 2.1.3.2 a deleted 15MW;    |
|         |        |        | 2.1.3.3 a added upgrade possibility of  |
|         |        |        | 2nd NB line; 2.1.3.5 added Automatic    |
|         |        |        | GDC Upgrade; 2.2.2 b revised CHI        |
|         |        |        | parameters; added 2.2.2 c; 2.2.4 a      |
|         |        |        | added possiblity of 2nd NB line; 2.3.3  |
|         |        |        | Noted Day 1 Req\'t, revised 2.3.3 a;    |
|         |        |        | added 2.3.4; added 2.5; deleted 2.6.1   |
|         |        |        | a,b,c,d; revised Table 2.6-1; 2.7.1 a   |
|         |        |        | specified field null target location;   |
|         |        |        | 2.7.4 a revised wording; added 2.7.5;   |
|         |        |        | 2.8 a changed disruption probability    |
|         |        |        | from 10 to 50%, changed rate from 0.5   |
|         |        |        | to 1MA/ms;                              |
+---------+--------+--------+-----------------------------------------+
| 2       | 1      | 009    | Revision 2 issued to correct            |
|         | 2/8/98 |        | typographic errors in [Revision         |
|         |        | 017    | 1]{.underline} date and footer date     |
|         |        |        | included in Revision 1. Revision 1 was  |
|         |        | 026    | issued as an attachment to CR-003.      |
|         |        |        | Revision 1 had incorrect date (3/3/97   |
|         |        | 037    | should have been 3/3/98) and footer had |
|         |        |        | incorrect date (October 20, 1997 should |
|         |        |        | have been March 3, 1998).               |
|         |        |        |                                         |
|         |        |        | Incorporated the following approved     |
|         |        |        | CR's.                                   |
|         |        |        |                                         |
|         |        |        | [CR-009]{.underline}-VV Upgrade (1.2.2  |
|         |        |        | a deleted)                              |
|         |        |        |                                         |
|         |        |        | [CR-017]{.underline} added PF-5         |
|         |        |        |                                         |
|         |        |        | 1.2.3a added PF5 & deleted 4a, Table    |
|         |        |        | 1.2.3.1-1 added PF5a&b and deleted      |
|         |        |        | PF4a, Table 1.2.3.1-2 added PF circuit  |
|         |        |        | 10, added 1.2.3.1g (designated existing |
|         |        |        | 1.2.3.1g to h)                          |
|         |        |        |                                         |
|         |        |        | [CR-026]{.underline} CHI power feed     |
|         |        |        | changes (1.6.4a and 2.2.2a)             |
|         |        |        |                                         |
|         |        |        | [CR-037]{.underline} Biasing outer VV   |
|         |        |        | for CHI (1.1.5b, 1.2.2d and 1.3.2a)     |
+---------+--------+--------+-----------------------------------------+
|         |        |        |                                         |
+---------+--------+--------+-----------------------------------------+
|         |        |        |                                         |
+---------+--------+--------+-----------------------------------------+
|         |        |        |                                         |
+---------+--------+--------+-----------------------------------------+
|         |        |        |                                         |
+---------+--------+--------+-----------------------------------------+
|         |        |        |                                         |
+---------+--------+--------+-----------------------------------------+

Preface 1

1 Functions, Configuration & Essential Features 2

1.1 General 2

1.1.1 Location 2

1.1.2 Design Basis and Upgrades 2

1.1.3 Directions of Fields & Currents 5

1.1.4 Material Selection 7

1.1.5 General Electrical Isolation Requirements 7

1.2 WBS 1 Torus Systems 8

1.2.1 Plasma Facing Components 8

1.2.2 Vacuum Vessel & Support Structure 9

1.2.3 Magnets 9

1.3 WBS 2 Plasma Heating & Current Drive Systems 11

1.3.1 High Harmonic Fast Wave (HHFW) 11

1.3.2 Coaxial Helicity Injection (CHI) 12

1.3.3 Electron Cyclotron (EC) Preionization 12

1.4 WBS 3 Auxiliary Systems 12

1.4.1 Vacuum Pumping System (VPS) 12

1.4.2 Cooling Water Systems (CWS) 13

1.4.3 Gas Delivery System (GDS) 13

1.4.4 Bakeout System 13

1.4.5 Glow Discharge Cleaning (GDC) System (Day 1 Requirement) 13

1.5 WBS 4 Plasma Diagnostics 13

1.6 WBS 5 Power Systems 15

1.6.1 AC Power Systems 15

1.6.2 TF Power Conversion System 15

1.6.3 PF Power Conversion System 15

1.6.4 CHI Power Conversion System 16

1.7 WBS 6 Central Instrumentation & Control (I&C) System 16

1.8 WBS 72 Project Physics 17

2 Performance & Operational Requirements 18

2.1 General 18

2.1.2 Baseline Requirements 22

2.1.2.1 Plasma Scenarios 22

2.1.2.1.1 Scenario I (OH/OH) 23

2.1.2.1.2 Scenario II (CHI/OH/HHFW) 23

2.1.2.1.3 Scenario III (OH, HHFW) 24

2.1.2.1.4 Scenario IV (OH/HHFW, CHI) 24

2.1.2.1.5 Scenario V (CHI/HHFW, CHI) 24

2.1.3 Upgrades 26

2.2 Plasma Heating and Current Drive 27

2.2.1 High Harmonic Fast Wave (HHFW) Heating & Current Drive 27

2.2.2 Coaxial Helicity Injection (CHI) 27

2.2.3 Electron Cyclotron (EC) Preionization 28

2.2.4 NBI Upgrade 28

2.3 Vacuum and Wall Conditioning 28

2.3.1 Base Pressure 28

2.3.2 Bakeout 29

2.3.3 Glow Discharge Cleaning (Day 1 Requirement) 29

2.3.4 Pre-shot Temperature 29

2.4 Fueling 29

2.4.1 Gas Injection 29

2.5 Limiter Requirements 29

2.6 Plasma Facing Components 30

2.7 Plasma Initiation and Equilibrium Control 31

2.7.1 Plasma Initiation 31

2.7.2 Radial Plasma Position Control 31

2.7.3 Vertical Plasma Position Control 32

2.8 Plasma Disruptions 33

3 Design Criteria 33

3.1 General Design Guidelines 33

3.2 Facilities Design Criteria 34

4 Environmental, Safety, and Health (ES&H) Requirements 35

4.1 Policy Statement 35

4.2 Radiological Design Objectives 36

5 Decontamination and Decommissioning Requirements 37

# Preface

The mission of the National Spherical Torus Experiment (NSTX) is to
assess the physics performance of the Spherical Torus (ST) concept, in
which the aspect ratio (ratio of major radius (R0) to minor radius (a),
R0/a) is much lower than most machines built to date. Supporting
objectives are to:

• Exploit techniques for non-inductive current drive and profile control
that are consistent with efficient continuous operation of a fusion
reactor without a central solenoid.

• Maximize the use of existing facilities and components so as to
minimize the cost of the project.

Top-level performance requirements for NSTX, along with cost and
schedule objectives, are included in the Project Definition Statement
(PDS).

Operational requirements and physics performance objectives are given in
the Project Requirements Document (PRD).

The General Requirements Document (GRD) defines the overall engineering
requirements.

System Requirements Documents (SRD) and System Design Descriptions (SDD)
shall be written for each major element of the Work Breakdown Structure
(WBS) and shall provide the detailed basis for the engineering design of
the machine.

The order of precedence for these requirements is the PDS, PRD, GRD,
SRD, SDD.

# 1 Functions, Configuration & Essential Features

The functions, configuration and essential features of the NSTX machine
and the various hardware elements of the WBS are outlined in the
following.

## 1.1 General

### 1.1.1 Location

a\. The NSTX machine shall be installed in the PPPL D-site Hot Cell,
henceforth referred to as the NSTX Test Cell.

### 1.1.2 Design Basis and Upgrades

a\. This GRD provides, in subsequent sections, the baseline requirements
for NSTX and provides additional information concerning upgrades.

b\. The baseline work scope is subdivided into two parts, namely that
which shall be in place at the time of first plasma and funded within
the Total Project Cost (TPC), henceforth referred to as Day 0 scope, and
that which will follow as the operational research program progresses,
henceforth referred to as Day 1 scope[^1]. Unless otherwise specified
herein, all requirements specified herein are applicable to the Day 0
scope. Day 1 items include the following:

• Glow Discharge Cleaning (GDC)

• Data Acquisition System

• Advanced Plasma diagnostics

\- IR Camera

\- Slow Diamagnetic Loop

\- Multichannel Bolometer

\- Survey Spectrometer (SPRED)

\- Soft X-Ray Imaging System

\- H detectors

\- CHERS

\- High-throughput CHERS background array

\- X-ray pulse height analysis

\- Neutral particle analyzer

\- Visible spectrometer

Note: Vacuum Vessel interface (port covers with diagnostic attachment
features) for the advanced plasma diagnostics listed above shall be
included as part of the Day 0 workscope.

c\. Upgrades consist of scope which is contemplated at present but may
or may not be undertaken, depending on the evolution of the experimental
program and the budgetary constraints. In order to minimize the life
cycle cost of the NSTX program and make optimum use of the facility, the
baseline design of NSTX shall not preclude the possibility of the
upgrades, and shall facilitate the upgrades whenever possible and cost
effective. Upgrades presently contemplated include the following:

• EC start-up upgrade

• Coaxial Helicity Injection (CHI) current sustainment

• Addition of Neutral Beam injection (NBI)

• Long pulse operation (with center stack replacement)

• Addition of pellet injector

• Plasma diagnostics upgrades

\- electron temperature profile measurement

\- plasma current profile measurement

• Automatic control for Glow Discharge Cleaning (GDC) between pulses

• Antenna tilting to align with the field lines

• Antenna bipolar drive

d\. No design features related to the EC upgrade are required in the
baseline NSTX facility.

e\. Any design features related to the CHI current sustainment mode
which are required on the torus and which cannot be readily added at a
later date shall be included in the baseline. Design features on
ancillary systems are not required for the baseline.

f\. Design features related to the NBI upgrade and the plan for their
implementation shall be as indicated in Table 1.1.2-1.

**Table 1.1.2-1: Plan for NBI Upgrade Features**

  ----------------------------------------------------------- --------------
  **Design Feature**                                          **Schedule**

  Plasma Facing Components (PFC) additional power             U
  dissipation\*                                               

  PFC protective armor for NB shine-through and inadvertent   U
  loading                                                     

  PFC beam dumps                                              U

  Vacuum Vessel (VV) additional power dissipation\*\*         U

  VV port compatibility and availability (up to two           B
  beamlines)                                                  

  Vacuum Pumping System (VPS) exhaust capability              B

  Cooling Water System (CWS) NB source cooling capacity       U

  Power Systems (PS) AC power (up to two beamlines)           B

  Central I&C additional control, data acquisition, and data  U
  network capacity                                            

  Facility space and provision for installation of NBI and    B
  related services                                            
  ----------------------------------------------------------- --------------

B = To be included in baseline

U = to be deferred until upgrade, unless convenient to include in
baseline at minimal cost

\* = During combined NBI + RF operations if the heating power exceeds
the baseline then the pulse duration and repetition period shall be
limited in accordance with the capability of the baseline PFCs, unless a
PFC upgrade is undertaken.

\*\* = During combined NBI + RF operations if the heating power exceeds
the baseline then the pulse duration and/or repetition period shall be
limited such that the average heat load is within the cooling capability
of the baseline VV design, unless a VV cooling upgrade is undertaken.

g\. Design features related to the long pulse upgrade and the plan for
their implementation shall be as indicated in Table 1.1.2-2.

**Table 1.1.2-2: Plan for Long Pulse Upgrade Features**

  ----------------------------------------------------------- --------------
  **Design Feature**                                          **Schedule**

  PFC active cooling                                          U

  Toroidal Field (TF) magnet inner legs                       U

  Toroidal Field (TF) magnet outer legs                       B

  Ohmic Heating (OH) magnet                                   not req\'d

  Poloidal Field (PF) magnets                                 B

  Plasma Heating & Current Drive long pulse capability        U

  Cooling Water System (CWS) additional cooling capacity      U

  Gas Delivery System (GDS) long pulse capacity               U

  Plasma Diagnostics long pulse capability                    U

  Power Systems (PS) AC and DC long pulse power supply        U

  Central I&C long pulse control and data acquisition         U
  capability                                                  
  ----------------------------------------------------------- --------------

B = To be included in baseline

U = to be deferred until upgrade, unless convenient to include in
baseline at minimal cost

h\. Baseline design features related to the pellet injector upgrade and
the diagnostics upgrades require only the provision for space and access
to a suitable Vacuum Vessel port, and are inherent in the baseline; no
special provisions are therefore required in the baseline.

### 1.1.3 Directions of Fields & Currents

a\. Figure 1.1.3-1 defines the positive sense of the right-handed
coordinate system which shall be used on NSTX.

![](media/image2.emf){width="2.0833333333333335in"
height="2.7083333333333335in"}

**NSTX Coordinate System**

**Figure 1.1.3-1**

Referring to Figure 1.1.3-1 the definition of positive sense of currents
and fields on NSTX shall be as indicated in Table 1.1.3-1.

**Table 1.1.3-1: NSTX Current/Field (+) Directions**

  ----------------------------------- -----------------------------------
  **Current/Field**                   **Nominal Direction**

  Plasma Current                      (+)

  Poloidal Coil Currents              (+)

  Toroidal Field                      (+)

  Radial Field                        (+) R

  Vertical Field                      (+) Z
  ----------------------------------- -----------------------------------

b\. Except for the RF launchers and the PFCs, all components of NSTX
shall be designed to permit operation with plasma current in either
direction and toroidal field in either direction. The RF launchers and
PFCs shall be designed to permit operation with plasma current in either
direction, but with toroidal field always in opposite direction.

c\. Toroidal angle = 0 degrees shall correspond to the \"north\"
direction, where the north-south axis in this context is defined as a
line parallel with the walls of the NSTX Test Cell which run
approximately in the magnetic (compass) north-south direction.
Furthermore, given this 0 degree reference, proceeding clockwise viewed
from above, the centerlines of the ports on the midplane occur at angles
as given in Table 1.1.3-2.

**Table 1.1.3-2: NSTX Port Centerline Angles**

  ----------------------------------- -----------------------------------
  **Port**                            **Angle**

  A                                   15

  B                                   45

  C                                   75

  D                                   105

  E                                   135

  F                                   165

  G                                   195

  H                                   225

  I                                   255

  J                                   285

  K                                   315

  L                                   345
  ----------------------------------- -----------------------------------

### 1.1.4 Material Selection

a\. All materials to be used in the torus and peripheral equipment (R
≤ 3.0 m, \|Z\| ≤ 3.0m) must have a relative magnetic permeability ≤ 1.02
unless otherwise authorized by the Project.

b\. Because of its deleterious effect on the High Harmonic Fast Wave
heating, the presence of ordinary hydrogen is to be avoided in the
vacuum chamber. Therefore its use is not planned as a fuel for NSTX, and
no NSTX components should introduce it.

c\. All materials utilized within the primary vacuum boundary shall be
on the PPPL Vacuum Committee approved list, or shall be approved by the
committee.

d\. All materials utilized within the primary vacuum boundary shall be
designed to withstand the anticipated temperatures during operation and
bakeout (section 2.3.2).

### 1.1.5 General Electrical Isolation Requirements

a\. All instrumentation shall be isolated via optical and/or magnetic
(isolation transformer) means prior to exiting the test cell boundary.
The isolation shall be rated to withstand a one minute DC hipot test at
5kV.

b\. All ancillary components which are in mechanical contact with the
vacuum vessel shall be electrically isolated from the vacuum vessel. The
isolation shall be rated to withstand a one minute AC hipot test at 2 kV
AC rms.

c\. Conducting loops formed by metallic structures within a radius of 3
meters from the centerline of the torus shall be broken by insulating
breaks. The insulation shall be rated to withstand a one minute AC hipot
test at 2 kV AC rms.

## 1.2 WBS 1 Torus Systems

### 1.2.1 Plasma Facing Components

a\. All surfaces which face the plasma (Plasma Facing Components (PFCs))
shall consist of carbon based materials designed to absorb the heat and
radiation flux from the plasma and heating systems, to minimize the
influx of impurities to the plasma, and to withstand the electromagnetic
forces associated with plasma disruption.

b\. The PFCs shall include inboard and outboard divertor plates for
absorption of the high heat flux due to plasma operation with Double
Null (DN) and Single Null (SN) separatrices (X-points), as well as
limiter (Natural Divertor) configurations.

c\. The PFCs shall include passive stabilizers consisting of upper and
lower plates connected in a saddle configuration, with toroidal
electrical breaks to avoid closed conducting toroidal loops. The precise
passive stabilizer geometry requirements and electrical characteristics
shall be established as part of the design evolution based on inputs
provided by the NSTX Project Physics Group.

d\. The PFCs shall include poloidal limiters to constrain the boundary
of cross sectional space occupied by the plasma. The passive stabilizers
and inner wall act as toroidal limiters.

e\. All PFCs shall be designed to accommodate a high temperature bakeout
mode to liberate trapped impurities.

f\. All PFCs shall be designed to accommodate a helium glow discharge
cleaning mode.

g\. Passive stabilizers shall be electrically connected to the Vacuum
Vessel via their mounting structures.

h\. Passive stabilizers shall be designed to be removable after the
machine has been assembled.

### 1.2.2 Vacuum Vessel & Support Structure

a\. The center stack casing shall be mechanically connected to, but
electrically isolated from, the upper and lower domes via a ceramic
insulator, so as to complete the vacuum boundary but allow for a
potential difference between the center stack casing and the remainder
of the vacuum vessel for CHI.

b\. Sufficient ports shall be provided with dimensions compatible with
the requirements of all types of Heating & Current drive systems (refer
to section 1.3) as well as diagnostic systems. Additional openings shall
be provided for personnel access.

c\. Vacuum Vessel ports for High Harmonic Fast Wave (HHFW, refer to
section 1.3.1) heating and current drive antennas shall accomodate the
RF feedthroughs associated with the antenna mounting, and shall be
located in accordance with the phasing requirements of the HHFW system.

d\. The lower dome of the outer section of the Vacuum Vessel shall be
connected electrically via eight toroidally symmetric connections to a
single point connection, which is designed to permit biasing (2kVDC) of
the outer Vacuum Vessel during CHI operations, and grounding of the
outer Vacuum Vessel at other times. Isolation shall be rated to
withstand a one minute DC hipot test at 2kV. Connections shall be sized
to carry the current during CHI operations as well as the return of the
current during bakeout heating of the center stack casing.

e\. Four toroidally symmetric connection points shall be provided at the
top and bottom of the center stack casing. Connections shall be sized to
carry the current during CHI operations as well as the return of the
current during bakeout heating of the center stack casing.

### 1.2.3 Magnets

1.2.3.1 Poloidal Field (PF) Magnets

a\. The PF magnets shall consist of an Ohmic Heating (OH) central
solenoid magnet, shaping field magnets (PF1a, PF1b), and outer PF
magnets (PF2a, 2b, 3a,3b,4b,4c, and PF5) as listed in Table 1.2.3.1-1.

**Table 1.2.3.1-1: PF Magnets**

  ----------------------------------- -----------------------------------
  **Designation**                     **Source**

  OH                                  New

  PF1a                                New

  PF1b                                New

  PF2a                                S-1, EF-1a

  PF2b                                S-1, EF-1b

  PF3a                                S-1, EF-2a

  PF3b                                S-1, EF-2b

  PF4b                                S-1, EF-3b

  PF4c                                S-1, EF-3c

  PF5a                                New

  PF5b                                New
  ----------------------------------- -----------------------------------

b\. The PF coil system shall be symmetric about the mid plane, defined
as the horizontal plane which passes through the elevation of maximum
plasma radial extent, except for PF1b which shall consist of a lower
coil only.

c\. The PF coils listed in Table 1.2.3.1-1 shall be connected in series
groups with independent current control as indicated in Table 1.2.3.1-2.

**Table 1.2.3.1-2: Independent PF Circuits**

  ----------------- -----------------------------------------------------
  **PF Circuit**    **Coil Grouping**

  1                 OH

  2                 PF1a, upper

  3                 PF1a, lower

  4                 PF1b, lower

  5                 PF2a, PF2b, upper

  6                 PF2a, PF2b, lower

  7                 PF3a, PF3b, upper

  8                 PF3a, PF3b, lower

  ~~9~~             PF4b,PF4c, upper & lower

  10                PF5a, PF5b, upper & lower
  ----------------- -----------------------------------------------------

d\. All series coil connections indicted in Table 1.2.3.1-2 shall result
in current flow which is equal in magnitude, and in the same direction,
in the series connected coils.

e\. All aspects of the PF coil design shall be compatible with NSTX
operation with plasma current and toroidal field in either direction.

f\. OH coil current and PF1b coil current shall always be in the same
direction.

g\. Operation of the PF4 and PF5 circuits shall be mutually exclusive.

h\. PF coil geometries and current scenarios shall be established as
part of the design evolution based on inputs provided by the NSTX
Project Physics Group, consistent with the requirements for start up
field null quality and loop voltage generation, as well as plasma
equilibrium control.

1.2.3.2 Toroidal Field (TF) Magnets

a\. The TF magnets shall consist of separate inner leg and outer leg
components, all connected in series. The utilization of cross sectional
area in the center stack of the machine shall be optimized to maximize
the conductor cross sectional area.

b\. All aspects of the TF coil design shall be compatible with NSTX
operation with plasma current and toroidal field in either direction.

## 

## 1.3 WBS 2 Plasma Heating & Current Drive Systems

### 1.3.1 High Harmonic Fast Wave (HHFW)

a\. The HHFW system shall utilize RF power produced by the six existing
Tokamak Fusion Test Reactor (TFTR) Ion Cyclotron Range of Frequencies
(ICRF) sources.

b\. The HHFW system shall utilize a twelve strap antenna mounted on the
vacuum vessel wall in the gap between the upper and lower passive
stabilizing plates. The antenna shall be arranged toroidally between the
NSTX vacuum vessel mid plane ports. Each current strap shall include a
back plane, a Faraday shield, and a local (bumper) limiter structure.
The antenna shall be compatible with bakeout and glow discharge modes of
operation.

c\. The twelve antennas shall be capable of operating at frequencies in
the range of 30MHz to 40MHz. All RF generators operating at any single
frequency shall be phase locked to provide control over the wave number
spectrum excited in the plasma at that frequency.

d\. Switches shall be provided to isolate HHFW power from the NSTX test
cell. These switches shall be interlocked with the test cell access
control system.

### 1.3.2 Coaxial Helicity Injection (CHI)

a\. The center stack casing and inner wall of the bore of the machine,
including the inboard divertor plates, shall be electrically isolated
from the remainder of the Vacuum Vessel to permit the biasing of this
structure with respect to the Vacuum Vessel, to drive a poloidal
component of plasma current. Both the center stack casing and the oyer
Vacuum Vessel shall be isolated from ground such that either one can be
grounded during CHI operations, with the other biased at the CHI
potential.

b\. The PFCs which form the electrodes from which the CHI current flows
shall be designed to dissipate the local power generation due to the CHI
current, during normal and fault conditions, and shall be designed to
withstand the electromagnetic forces due the fault current deliverable
by the CHI power supply system.

### 1.3.3 Electron Cyclotron (EC) Preionization

a\. The EC system shall provide microwave RF power in the electron
cyclotron range of frequencies for preionization.

b\. One EC launcher shall be installed at an outboard location in the
Vacuum Vessel to direct the microwave radiation toward the desired
absorption location. The launcher must be compatible with bakeout and
glow discharge modes. The launcher shall have a vacuum window connecting
it to the external transmission system. This window must have low
electrical loss at microwave frequencies and satisfy the thermal and
mechanical requirements for vacuum interfaces.

c\. Switches shall be provided to isolate EC power from the NSTX test
cell. These switches shall be interlocked with the test cell access
control system.

## 1.4 WBS 3 Auxiliary Systems

### 1.4.1 Vacuum Pumping System (VPS) 

a\. The VPS shall provide the required high vacuum environment for
plasma operations. It shall exhaust the spent plasma constituents after
each pulse, and shall exhaust the impurities associated with the bakeout
and glow discharge cleaning of the PFCs.

b\. The VPS shall be equipped with redundant Residual Gas Analyzers
(RGA).

### 1.4.2 Cooling Water Systems (CWS) 

a\. The CWS shall provide the required cooling water of the required
quality, temperature, pressure and flow for all NSTX systems.

b\. Instrumentation shall be provided to monitor the flow rate in all
individual magnet coil and bus bar cooling paths.

c\. Instrumentation shall be provided to monitor the inlet and outlet
water temperature of a subset of the magnet coil cooling paths, with
provision for alarming both high and low temperature conditions.

d\. The CWS and NSTX facility Heating, Ventilation, and Air Conditioning
(HVAC) system shall include dew point controls to prevent condensation
on water cooled components in the NSTX test cell.

### 1.4.3 Gas Delivery System (GDS) 

a\. The GDS shall provide the required gas injection for NSTX for
deuterium and helium as required for conditioning and plasma operations.

b\. Three piezoelectric valves shall be provided to control gas
injection to the Vacuum Vessel. The valves shall be supplied by
manifolds which connect to four source tanks in such a way that any
valve can be supplied from any source tank.

### 1.4.4 Bakeout System 

a\. The bakeout system shall include means for heating the surfaces of
the PFCs to the required temperatures for an indefinite period while
maintaining the Vacuum Vessel and components connected thereto to
temperatures within their temperature ratings.

### 

### 1.4.5 Glow Discharge Cleaning (GDC) System (Day 1 Requirement)

a\. NSTX shall be equipped with a GDC system for cleaning, under zero
field conditions, the internal Vacuum Vessel surfaces via the
bombardment of ions formed during the glow process.

## 

## 1.5 WBS 4 Plasma Diagnostics

a\. The baseline plasma diagnostics set shall consist of the elements
listed in Table 1.5-1.

**Table 1.5-1: Baseline NSTX Diagnostics Set**

+----------+------------------------------+---------------------------+
| **Availa | **Diagnostic**               | **Function**              |
| bility** |                              |                           |
+----------+------------------------------+---------------------------+
| Day 0    | Plasma current Rogowski      | Total plasma current      |
|          | coils                        |                           |
+----------+------------------------------+---------------------------+
|          | Eddy current Rogowski coils  | Halo current monitoring   |
+----------+------------------------------+---------------------------+
|          | Flux loops                   | Poloidal flux for plasma  |
|          |                              | control                   |
+----------+------------------------------+---------------------------+
|          | B, B coils                   | Plasma control/magnetic   |
|          |                              | fluctuations              |
+----------+------------------------------+---------------------------+
|          | Mirnov coils                 | Magnetic fluctuations     |
+----------+------------------------------+---------------------------+
|          | Visible TV camera            | External shape for plasma |
|          |                              | control                   |
+----------+------------------------------+---------------------------+
|          | 1 mm microwave               | Line-integrated plasma    |
|          | interferometer               | density                   |
+----------+------------------------------+---------------------------+
|          | Langmuir                     | Divertor parameters       |
|          | probes/thermocouples2        |                           |
+----------+------------------------------+---------------------------+
| Day 1    | IR camera                    | Heat loads                |
+----------+------------------------------+---------------------------+
|          | "Slow" diamagnetic loop      | Stored energy             |
|          |                              |                           |
|          | (using toroidal field coil)  |                           |
+----------+------------------------------+---------------------------+
|          | Multichannel bolometer       | Radiated power profile    |
+----------+------------------------------+---------------------------+
|          | Survey spectrometer (SPRED)  | Plasma impurities         |
+----------+------------------------------+---------------------------+
|          | Soft X-ray imaging system    | Plasma instabilities and  |
|          |                              | fluctuations              |
+----------+------------------------------+---------------------------+
|          | H detectors                  | Edge recycling            |
+----------+------------------------------+---------------------------+
|          | CHERS1                       | Ion temperature &         |
|          |                              | toroidal rotation         |
+----------+------------------------------+---------------------------+
|          | High-throughput CHERS        | Background subtraction    |
|          |                              | for CHERS                 |
|          | background array             |                           |
|          |                              | and Zeff(r) from visible  |
|          |                              | continuum                 |
+----------+------------------------------+---------------------------+
|          | X-ray pulse height analysis  | Core electron temperature |
+----------+------------------------------+---------------------------+
|          | Neutral particle analyzer    | Core ion temperature and  |
|          |                              | fast ions                 |
+----------+------------------------------+---------------------------+
|          | Visible spectrometer         | Edge/divertor             |
|          |                              | spectroscopy              |
+----------+------------------------------+---------------------------+

1CHERS: Charge-Exchange Recombination Spectroscopy

2Diagnostics incorporated into plasma facing components

b\. Diagnostic elements which must be located in the center stack
between the OH coil ground plane and the center stack casing (e.g.
Rogowski coils, Flux loops) shall be referenced to ground and shall be
insulated to withstand the full CHI voltage. The insulation shall be
rated for a one minute DC hipot test at 5kV.

## 1.6 WBS 5 Power Systems

### 1.6.1 AC Power Systems 

a\. The AC Power Systems shall provide all electrical power required for
the NSTX facility.

### 1.6.2 TF Power Conversion System 

a\. The TF Power Conversion System shall be designed to provide a
constant current in the TF magnets during an NSTX discharge based on a
reference current input signal provided in real time.

b\. Bus links or other means shall be provided in order that the current
in the TF magnets can be driven in either direction. The polarity
reversal procedure shall require 4 hours or less.

c\. No-load disconnect switches shall be provided to isolate the TF
Power System from the connections to the TF magnets. In addition,
no-load grounding switches shall be provided to ground the terminals of
the connections to the TF magnets. These switches shall be interlocked
with test cell access control.

d\. Redundant measurements of TF current shall be provided.

e\. The TF Power Conversion System shall include protection to avoid the
delivery of current which would overheat the TF magnets, assuming that
their coolant conditions are nominal.

## 

### 1.6.3 PF Power Conversion System 

a\. PF Power System shall be designed to provide a variable current in
the PF magnet circuits (listed in Table 1.2.3.1-2) during an NSTX
discharge based on a reference current input signal provided in real
time.

b\. All PF circuits except for OH and PF3 shall be unipolar during a
pulse. OH bipolarity is required to maximize the flux swing provided by
the OH coil. PF3 bipolarity is required to provide cancellation of the
stray field from the OH coil during plasma initiation, after which time
a current of the opposite polarity is required for plasma equilibrium
and shaping.

c\. Bus links or other means shall be provided in order that the current
in the PF magnets can be driven in either direction. The polarity
reversal procedure shall require 4 hours or less.

d\. No-load disconnect switches shall be provided to isolate the PF
Power System from the connections to the PF magnets. In addition,
no-load grounding switches shall be provided to ground the terminals of
the connections to the PF magnets. These switches shall be interlocked
with test cell access control.

e\. Redundant measurements of each PF current shall be provided.

f\. The PF Power Conversion System shall include protection to avoid the
delivery of current which would overheat the PF magnets, assuming that
their coolant conditions are nominal.

### 1.6.4 CHI Power Conversion System 

a\. The baseline CHI Power System shall be designed to deliver a
controlled current into the CHI electrodes with one electrode connected
to the center stack, and the other electrode connected to the outer
vacuum vessel.

b\. Protective features shall be included to prevent the application of
excess voltage to the electrode associated with the center stack.

c\. Bus links or other means shall be provided in order that the current
in the CHI circuit can be driven in either direction. The polarity
reversal procedure shall require 4 hours or less.

c\. No-load disconnect switches shall be provided to isolate the CHI
Power System from the connections to the CHI load circuit. In addition,
no-load grounding switches shall be provided to ground the terminals of
the connections to the CHI load circuit. These switched shall be
interlocked with test cell access control.

## 1.7 WBS 6 Central Instrumentation & Control (I&C) System

a\. The Central I&C system shall provide all supervisory control and
monitoring of the NSTX facility, including:

• Plant Control and Monitoring (asynchronous routine control and
monitoring)

• Synchronization (synchronization of triggered actions from master
clock events)

• Plasma Control Processor and Input/Output Interface (digital processor
and I/O hardware fo for interface with plasma control measurements and
actuators)

• Safety Interlocks (master supervisory control of experiment)

• Access Control (control and monitoring of access to the NSTX Test
Cell)

• Data Acquisition (Day 1 Requirement) (periodic sampling, acquisition
and display of regularly sampled data, and acquisition and display of
data sampled and stored by remote devices)

b\. The Central I&C system shall provide reference signals to local I&C
systems (provided by responsible WBS elements) for local feedback
control, but is not required to close the loop for feedback control of
plant processes.

c\. The NSTX Control Room shall be installed in the location previously
occupied by the TFTR Control Room.

d\. The design of the Central I&C system shall facilitate access to
archived NSTX data, as well as the control of diagnostic data
acquisition systems, by parties outside of the NSTX control room (e.g.
remote collaborators, physicists inside and outside of PPPL) (Day 1
Requirement).

e\. The Central I&C system shall provide sixteen (16) electrically
isolated, general purpose signal channels between the test cell and the
control room. These signals shall be displayed in the control room in
real-time.

## 1.8 WBS 72 Project Physics

a\. NSTX Project Physics shall be responsible for the specification of
all Plasma Control hardware and software.

b\. NSTX Project Physics shall provide the requirements to the other WBS
elements as listed in this document which are directly related to plasma
behavior including the following.

• PF coil current centers required to achieve NSTX mission

• PF coil current scenarios and equilibria which are required to achieve
NSTX mission including:

\- establishment of required field null quality for plasma initiation

\- establishment of required loop voltage for plasma initiation

\- reference plasma scenarios

\- plasma shape and profile flexibility equilibria

\- feed back control of radial and vertical position, as well as
divertor strike point position

• PF coil voltage requirements due to:

\- basic scenarios

\- feedback control of radial and vertical position, as well as divertor

strike point position

• Geometric and electrical characteristics of passive plates

• Description of cross sectional boundary of space occupied by plasma
for all modes of operation

• Maximum heat loads on PFCs, including divertor plates and limiters,
due to plasma operation and CHI

• Currents and voltages in passive structures and PF coils due to plasma
disruption.

• Effective impedance presented to CHI power supply circuit

# 

# 2 Performance & Operational Requirements

## 2.1 General

2.1.1 Definitions

a\. The events listed in Table 2.1.1-1 (in their nominal sequence of
occurrence) are defined for the purposes of requirements definition.

**Table 2.1.1-1: Definition of Events**

  -------------- --------------------------------------------------------
  **Name**       **Definition**

  SOP            Start of Pulse (start of power supply energization)

  SOPTF          Start of Pulse TF (start of TF current)

  SOPPF          Start of Pulse PF (start of PF current)

  SOFTF          Start of Flat Top TF

  SOI            Start of Initiation

  EOI            End of Initiation

  SOD            Start of Plasma Discharge

  SOF            Start of Plasma Flat Top

  SOX            Start of X-point

  EOX            End of X-point

  EOF            End of Plasma Flat Top

  EOD            End of Plasma Discharge

  EOFTF          End of Flat Top TF

  EOPPF          End of Pulse PF (end of PF current)

  EOPTF          End of Pulse TF (end of TF current)

  EOP            End of Pulse (end of power supply energization)
  -------------- --------------------------------------------------------

b\. The plasma major radius (R0) is defined as the radius from the major
axis of the torus to the center of the plasma on the mid plane. The
plasma minor radius (a) is defined as the half width of the plasma on
the mid plane. The nominal major radius of NSTX shall be 0.854 meters.

c\. All required flux swings (volt-seconds) are measured at R0, on the
mid plane.

d\. All required loop voltages are measured at R0, on the mid plane at
the EOI event time.

e\. For limiter (Natural Divertor, ND) plasmas, the plasma edge is
defined herein as the flux surface which is tangent with the inboard
limiting surface at the mid plane. The Scrape Off Layer (SOL) is defined
herein as the region between the plasma edge and the flux surface which
contains approximately 1- -3 ≈ 95% of the particle power loss from the
plasma. A fraction of the SOL impinges on the inboard limiting surface;
the remainder impinges on other PFCs. Refer to Figure 1.1.2-1.

![](media/image3.emf){width="3.44375in" height="6.1819444444444445in"}

**Limiter (Natural Divertor) Plasma**

**Figure 2.1.1-1**

f\. For Double Null (DN) X-point divertor plasmas, the inboard and
outboard plasma edges are defined as the flux surfaces which pass
through the X-points and which intersect the mid plane at R0+/- a. These
flux surfaces extend beyond the X-point and impinge on the inboard and
outboard divertors at the inboard and outboard strike points,
respectively. Refer to Figure 2.1.1-2.

![](media/image4.emf){width="4.569444444444445in"
height="4.833333333333333in"}

**Double Null Plasma**

**Figure 2.1.1-2**

g\. For Single Null (SN) X-point divertor plasmas, the plasma edge is
defined as the flux surface which passes through the active X-point and
which intersect the mid plane at R0+/- a. This flux surface extends
beyond the X-point and impinges on the inboard and outboard divertors at
the inboard and outboard strike points, respectively. Refer to Figure
2.1.1-3.

![](media/image5.emf){width="3.654166666666667in" height="4.30625in"}

**Single Null Plasma**

**Figure 2.1.1-2**

### 2.1.2 Baseline Requirements

#### 2.1.2.1 Plasma Scenarios

a\. The baseline NSTX facility shall be designed to provide the plasma
scenarios given in Table 2.1.2.1-1.

**Table 2.1.2.1-1: NSTX Plasma Scenarios**

+----------------+------------------+---------------+-----------------+
| **SCENARIO**   | **START-UP1**    | **CURRENT**   | **C             |
|                |                  |               | ONFIGURATION3** |
|                |                  | **S           |                 |
|                |                  | USTAINMENT2** |                 |
+----------------+------------------+---------------+-----------------+
| I              | Inductive        | Inductive     | ND, DN          |
+----------------+------------------+---------------+-----------------+
| II             | CHI              |               | SN              |
+----------------+------------------+---------------+-----------------+
|                |                  | Inductive,    | ND, DN, (SN)    |
|                |                  | HHFWCD        |                 |
+----------------+------------------+---------------+-----------------+
| III            | Inductive        | HHFWCD        | ND, DN          |
|                | (Half-Swing)     |               |                 |
+----------------+------------------+---------------+-----------------+
| IV             | Inductive        |               | ND, DN, (SN)    |
|                | (Half-Swing)     |               |                 |
+----------------+------------------+---------------+-----------------+
|                |                  | CHI4, HHFWCD  | SN5             |
+----------------+------------------+---------------+-----------------+
| V              | CHI              | CHI4, HHFWCD  | SN5             |
+----------------+------------------+---------------+-----------------+

1 EC Pre-ionization shall be utilized in all start-up scenarios

2 Contributions from the bootstrap current are expected during the
sustainment phase

3 ND - Natural Divertor; DN - Double Null X-Point; SN - Single Null
X-Point

4 CHI during sustainment phase shall be an upgrade

5 SN during sustainment phase if CHI used then; DN or ND otherwise

a\. In order to promote reliable plasma initiation and operational
flexibility, EC is applied in all scenarios to provide initial plasma
breakdown and (in case of the ECH upgrade) to facilitate sufficient
current ramp-up rate. For Scenarios I, II, and IV, which utilize OH
during the start-up, the OH loop voltage (in absence of a plasma) shall
be at least 3.0 V. For the scenarios that utilize coaxial helicity
injection (CHI) during start-up or sustainment, a SN configuration will
be used during the portion of the discharge in which CHI is applied. In
all the scenarios, a portion of the full 1 MA plasma current is expected
to be driven non-inductively by varying amounts of bootstrap current.

#### 2.1.2.1.1 Scenario I (OH/OH)

Scenario I is characterized by inductively ramping the initial EC pre
ionized plasma current to a full current of 1 MA in 0.2 to 0.4 sec,
holding the current flat for approximately 0.5 sec, and then ramping the
plasma current down in approximately 0.2 sec. Auxiliary heating will be
applied during the ramp-up phase and current flattop phase to increase
the plasma stored energy and temperature, and to attain high-t and
maintain this state during the current flattop. t will be ramped down
with the plasma current. Approximately 1.0 volt-seconds are supplied
between the start and end of the plasma pulse (0.6 volt-seconds from the
OH). The high harmonic heating technique will be developed in this
scenario. Plasmas will be in either the Natural Divertor or Double Null
configuration.

#### 2.1.2.1.2 Scenario II (CHI/OH/HHFW)

Scenario II is characterized by establishing a 0.5 MA target plasma
using Coaxial Helicity Injection and EC preionization, ramping the
current to 1 MA and holding it constant for up to 0.5 sec using a
one-half OH swing and/or High Harmonic Fast Wave current drive, and then
ramping the plasma current down. Auxiliary heating will be applied
during the 0.5 to 1.0 MA ramp-up phase and during the current flattop
phase to increase the plasma temperature, stored energy, and to maximize
t, maintaining high-t during the current flattop period. Up to 0.5
volt-seconds are supplied during the sustainment phase (Ip≥0.5 MA). The
plasma will be in a Single Null Divertor Configuration during the time
the CHI is applied, and in either a Natural Divertor, Double Null (or
Single Null) Divertor configuration thereafter. Other startup scenarios,
such as utilizing EC and HHFW heating, may be attempted.

### 

#### 2.1.2.1.3 Scenario III (OH, HHFW)

Scenario III is characterized by inductively ramping the initial EC
preionized plasma current to a full current of 1 MA in 0.2 to 0.4 sec,
holding the current flat for up to 4.5 sec using High Harmonic Fast Wave
current drive, and then ramping the plasma current down. Auxiliary
heating will be applied during the ramp-up phase and current flattop
phase to increase the plasma stored energy and temperature, and to
attain high-t and maintain this state during the current flattop. t will
be ramped down with the plasma current. Approximately 0.65 volt-seconds
are supplied between the start and end of the plasma pulse. The high
harmonic current drive technique will be developed in this scenario.
Plasmas will be in either the Natural Divertor or Double Null Divertor
configuration.

#### 2.1.2.1.4 Scenario IV (OH/HHFW, CHI)

Scenario IV is characterized by inductively ramping the initial EC
preionized plasma current to at least 0.5 MA in 0.2 to 0.4 sec, ramping
the current up to 1 MA and holding it constant for up to 4.5 sec using
Fast Wave Current Drive and/or Coaxial Helicity Injection (upgrade), and
then ramping the plasma current down. Auxiliary heating will be applied
during the ramp-up phase and during the current flattop phase to
increase the plasma temperature, stored energy, and to maximize t
(maximizing bootstrap current), and maintaining high-t during the
current flattop phase. Up to 0.65 volt-seconds are supplied between the
start and end of the plasma pulse. The plasma will be in a Natural
Divertor, or Double or Single Null Divertor configuration during the
start-up phase (before the CHI is on), and a Single Null Divertor
configuration during the time the CHI is applied.

#### 2.1.2.1.5 Scenario V (CHI/HHFW, CHI)

Scenario V is characterized by fully non-inductive operation. A target
plasma of 0.5 MA will be created using CHI and EC preionization, and
then the plasma current will be ramped up and maintained at the 1.0 MA
level using a combination of HHFW, CHI (upgrade), and bootstrap
currents. Auxiliary heating will be applied during the ramp-up phase and
during the current flattop phase to increase the plasma temperature,
stored energy, and to maximize t (maximizing bootstrap current), and
maintaining high-t during the current flattop phase. The plasma will be
in a Single Null Divertor configuration during the time the CHI is
applied. If the 1 MA plasma current can be maintained solely by HHFW
current drive and bootstrap current, the configuration will be relaxed
into one of Natural Divertor or Double Null Divertor.

2.1.2.2 Scenario Requirements

a\. For all reference scenarios described herein the TF flat top shall
extend for the full duration of plasma current, i.e. SOFTF ≤ SOI, and
EOD ≤ EOFTF.

b\. For all reference scenarios described herein the nominal toroidal
field shall be 3.0 kG at R0. However, it shall be possible to operate
with a toroidal field at 6.0kG with a TF flat top (SOFTF to EOFTF)
duration of 0.6 seconds.

c\. The peak-to-average toroidal field ripple shall be ≤ 0.5% over the
entire plasma cross section.

d\. For all reference scenarios described herein the PF current
distributions at SOI, EOI, SOD, SOF, SOX, EOX, EOF, and EOD shall be
specified by the NSTX Project Physics group.

e\. For all reference scenarios described herein the gap between the
outboard plasma edge at the mid plane and the surface of the HHFW
antennas shall be 2.0 cm.

f\. For all reference scenarios described herein the heating/current
drive power shall be applied to the plasma for the full duration SOD to
EOD, except for the EC which shall be applied only during the interval
SOI to EOI, with a maximum duration of 5 mS in the baseline, 100mS in
case of the EC upgrade.

g\. Operation of the CHI is limited to Single Null plasma
configurations.

2.1.2.2 Flexibility

a\. In addition to the basic scenarios described in section 2.1.2.1 the
design of the NSTX machine shall provide flexibility in terms of
variation of plasma shape during the interval between SOF and EOF, which
require PF current distributions different from those associated with
the basic scenarios. Plasma edge, SOL, and PFC heat load requirements
described for the basic scenarios will still apply, however.

b\. For all flexibility points the PF current distributions shall be
specified by the NSTX Project Physics group.

2.1.2.3 Pulse Repetition Period & Operating Life

a\. For the Inductive Scenario (Scenario I) the baseline NSTX machine
shall be designed for a pulse repetition period of 600 seconds and a
maximum of 48 pulses per 24 hour period.

b\. For the Non-Inductive Scenarios (Scenario II, III, and IV) the
baseline NSTX machine shall be designed for a pulse repetition period of
300 seconds and a maximum of 96 pulses per 24 hour period.

c\. The NSTX machine shall be designed to operate for a period of 10
years. However, new equipment related to the D-site infrastructure
(building and utilities) shall be designed for a 25 year operating life.

d\. NSTX operation shall be assumed to consist of 96 pulses per day, 5
days per week, 3 weeks per month, 9 months per year, for 10 years (total
of ≈ 130,000 pulses). Non-operating times are available for maintenance.

e\. For design purposes the distribution of pulses shall be assumed as
follows:

• 1/3 of the pulses will be double-swung OH covering inductive only,
short pulse operation

• 2/3 of the pulses will be single-swung OH covering non-inductive
current drive studies

f\. Approximately 25% of of all the shots shall be at high toroidal
field (6 kG). This proportion will be split into double-swung and
single-swung OH in the same proportion as 3 kG operation.

### 2.1.3 Upgrades

#### 

a\. The upgrades described herein are envisioned as possibilities which
may or may not be undertaken, depending on experience gained with NSTX
operation, and other factors. The baseline design of NSTX should
facilitate the upgrades when possible without significant cost impact.
As a minimum, the baseline design shall permit eventual upgrade and the
upgrade path shall be identified as part of the baseline design process.

2.1.3.1 Electron Cyclotron Upgrade (EC)

a\. To begin the physics investigation of the EC torus formation
start-up, an existing Oak Ridge National Laboratory (ORNL) system, 200
kW power for 100 msec, shall be used.

2.1.3.2 CHI Current Sustainment Power Supply Upgrade

a\. The CHI current sustainment power supply would be required to
provide a current of 20.0 kA for the full duration SOD to EOD.

2.1.3.3 Neutral Beam Injection (NBI) Upgrade

a\. The NSTX design shall consider an upgrade which would, initially,
place one TFTR Neutral Beam Injector on NSTX, operating in the range of
80 to 110kV with corresponding power to the plasma of 5.33 to 7.33MW,
for 5 seconds once every 300 seconds. Provision shall also be included
for the possible implementation of a second TFTR Neutral Beam Injector
at a later date.

b\. The baseline design for all NSTX components shall identify an
upgrade path for the neutral beam upgrade.

2.1.3.4 Long Pulse Upgrade

a\. The NSTX design shall consider an upgrade which would remove the
baseline TF and OH magnets, and place a new TF magnet in the center
stack. The NSTX plasma pulse length shall be assumed to be 60 seconds
for this upgrade. The long pulse repetition period shall be 3600
seconds.

b\. The baseline design for all NSTX components shall identify an
upgrade path for the long pulse operation.

2.1.3.5 Other Upgrades

a\. GDC and related systems shall be designed for an upgrade to
automatic GDC operation between NSTX discharges; however the baseline
NSTX device is not required to provide automatic shutters, e.g. which
may be required of some components.

. b. No quantitative performance or operational requirements are given
at this time for the Pellet Injection upgrade.

## 2.2 Plasma Heating and Current Drive

### 2.2.1 High Harmonic Fast Wave (HHFW) Heating & Current Drive

a\. The HHFW system shall be designed to deliver 6 MW of power to the
plasma for 5 seconds, once every 300 seconds.

### 2.2.2 Coaxial Helicity Injection (CHI)

a\. The CHI powers system shall be designed to provide a controlled
current waveform with a peak current of 50.0 kA, and rise time 5mS.

b\. For purposes of sizing the CHI power system components, the plasma
(viewed from the external circuit terminals) may be modeled by an
inductance of 80.0 µH, and aresistance of 7.0mΩ.

c\. Based on the nominal discharge current and equivalent circuit
parameters above, the nominal voltage across the CHI electrodes is
approximately 1kV. However, to provide flexibility, the design voltage
level shall be 2kV. All related electrical insulation shall withstand a
one minute, 5kV DC hipot test.

### 

### 2.2.3 Electron Cyclotron (EC) Preionization 

a\. The EC system shall be designed to deliver 20kW of power for 5 msec
to the plasma.

### 2.2.4 NBI Upgrade

a\. The NBI system (if the initial one beam line upgrade is undertaken)
shall be assumed to deliver 5 MW to the plasma at 80kV for 5 seconds
once every 300 seconds. The total power to be accomodated in the case of
a two beam line upgrade is TBD.

[2.2.5 Total Upgrade Auxiliary Heating Power]{.underline}

a\. PFCs and Vacuum Vessel cooling systems shall be designed to
dissipate 6MW for 5 seconds once every 300 seconds.

## 

## 2.3 Vacuum and Wall Conditioning

### 2.3.1 Base Pressure

a\. The NSTX shall operate in high vacuum conditions with a base partial
pressure of ≤1x10-8 torr for fuel gases (Z ≤ 2) and a base partial
pressure of ≤1x10-9 torr for impurity gases (Z \> 2) at 65°C.

b\. The impurity gas load during pump down to base pressure shall not
exceed 1x10-5 torr-l/s.

c\. The vacuum pumping system shall be capable of evacuating the Vacuum
Vessel from atmospheric pressure to 10-3 torr in less than 3 hours.

d\. The vacuum pumping system shall be capable of evacuating the Vacuum
Vessel from 2 x 10 -3 Torr to 1 x 10 -7 Torr during the interval between
each NSTX pulse with a fuel gas load of TBD liters.

e\. The vacuum pumping system shall maintain a vacuum of 10 -2Torr
during Glow Discharge Cleaning (GDC).

### 

### 2.3.2 Bakeout 

a\. The surfaces of the PFCs shall be heated during bakeout to 350°C.

b\. The temperature of the inner Vacuum Vessel surfaces shall be heated
to at least 150°C.

c\. Bakeout heaters shall be designed to heat the Vacuum Vessel and PFCs
to the required temperature in 48 hours. After completion of bakeout,
the machine shall be cooled down to an operation temperature (nominally
room temperature) in less than 24 hours.

### 2.3.3 Glow Discharge Cleaning (Day 1 Requirement) 

a\. The NSTX shall be equipped to provide glow discharge cleaning (GDC)
mode with DC glow in the range of 5 \~ 30 mtorr of D or He at voltages
up to \~450 V and currents up to \~20 A for indefinitely long periods .

### 2.3.4 Pre-shot Temperature

a\. In-vessel components shall be maintained at temperatures not less
than 50°C between discharges.

## 

## 2.4 Fueling

### 

### 2.4.1 Gas Injection

a\. The NSTX shall be provided with a programmable gas injection system
capable of supplying deuterium, and helium gases to the outboard mid
plane with a maximum throughput of 50 Torr-l/s.

## 

## 2.5 Limiter Requirements

### 

a\. The inner wall shall act as the inboard limiter.

b\. Passive plates and HHFW antenna shielding shall act as the outboard
limiter.

## 

## 

## 

## 

## 2.6 Plasma Facing Components

a\. PFCs shall withstand the heat loads given in Table 2.6-1[^2] for the
rated (SOD to EOD) pulse duration at the rated NSTX duty cycle, without
(as a design goal) divertor strike point sweeping. However, if
technology limits dictate the need for sweeping in some cases then
sweeping or other means for heat flux amelioration shall be considered.

**Table 2.6-1: PFC Heat Loads**

  -------------- --------------- ----------- ----------- ----------- ----------- --------- ----------- ---------
  **Scenario**   **Parameter**   **Inner                 **Outer                 **Inner   **Total**   
                                 Div**                   Div**                   Wall**                

                                 **Upper**   **Lower**   **Upper**   **Lower**                         

  **Natural      Total Power                                                               6.0         MW
  Divertor**                                                                                           

                 Radiated Power                                                            1.8         MW

                 Non-Radiated    0.0         0.0         1.1         1.1         2.1       4.2         MW
                 Power                                                                                 

                 Power Flux      0.000       0.000       0.094       0.094       2.000                 m
                 Width                                                                                 

                 Peak Flux       0.0         0.0         4.3         4.3         1.9                   MW/m\^2

  **Double       Total Power                                                               6.0         MW
  Null**                                                                                               

                 Radiated Power                                                            1.8         MW

                 Non-Radiated    0.4         0.4         1.7         1.7         0.0       4.2         MW
                 Power                                                                                 

                 Power Flux      0.038       0.038       0.038       0.038       2.000                 m
                 Width                                                                                 

                 Peak Flux       5.1         5.1         17.1        17.1        0.0                   MW/m\^2

  **Single       Total Power                                                               6.0         MW
  Null**                                                                                               

                 Radiated Power                                                            1.8         MW

                 Non-Radiated    0.0         1.4         0.0         2.8         0.0       4.2         MW
                 Power                                                                                 

                 Power Flux      0.000       0.092       0.000       0.100       2.000                 m
                 Width                                                                                 

                 Peak Flux       0.0         7.0         0.0         10.8        0.0                   MW/m\^2
  -------------- --------------- ----------- ----------- ----------- ----------- --------- ----------- ---------

b\. Heat flux on the divertors shall be assumed to impinge over a region
beginning at the strike point and ending at a distance of equal to the
power flux width (∆) given in Table 2.6-1. The peak heat flux given in
Table 2.6-1 occurs at the strike point. The heat flux (q) along the
power flux width shall be assumed equal to q(x) = qpeak \* -x/∆ where x
= 0 occurs at the strike point.

c\. Heat flux on the inner wall shall be assumed to impinge
symmetrically about the midplane with a profile as given in Table 2.6-2
and Figure 2.6-1. The profile shown yields a total power deposition of 1
watt over a cylinder with radius of 0.175 m and height of 2.0 m. For a
particular scenario therefore the profile shall be scaled by total power
on the inner wall given in Table 2.6-1.

**Table 2.6-2: Normalized Inner Wall Heat Flux Profile**

  ----------------------------------- -----------------------------------
  **Z(m)**                            **q(W/m\^2)**

  0                                   0.70

  0.2                                 0.41

  0.4                                 0.90

  0.6                                 0.35

  0.7                                 0.41

  1.0                                 0.00
  ----------------------------------- -----------------------------------

![](media/image6.emf)

**Figure 2.6-1: Normalized Inner Wall Heat Flux Profile**

## 2.7 Plasma Initiation and Equilibrium Control

### 2 7.1 Plasma Initiation

a\. The NSTX PF/OH magnets and power systems shall be designed to
produce a loop voltage ≥ 3.0V and a field null (≤ 2 Gauss) region ≥ 40
cm diameter for ≥ 2 mS at a target located at r=0.8 m on the midplane.

### 2.7.2 Radial Plasma Position Control

a\. The NSTX machine shall include a feedback equilibrium control
capability which will provide radial plasma position control such that:

• the radial location of the last closed flux surface on the outboard
mid plane can be maintained within ±1.0 cm of nominal.

• the radial location of the last closed flux surface on the outboard
mid plane can be moved by ±2 cm from nominal in approximately 10 msec,
in response to needs for RF coupling

Coil current and voltage requirements (in addition to those required to
accomplish the basic scenario) shall be specified by NSTX Project
Physics.

### 2.7.3 Vertical Plasma Position Control

a\. Conducting structure (passive plates) shall be provided which
decrease the growth rate of the vertical instability. Precise geometry
and required electrical characteristics of passive plates shall be
provided by NSTX Project Physics.

b\. The NSTX machine shall include a feedback equilibrium control
capability which will provide vertical position control such that the
location of the centroid of the plasma can be maintained within ± 1.0 cm
of nominal.. Coil current and voltage requirements (in addition to those
required to accomplish the basic scenario) shall be specified by NSTX
Project Physics.

### 2.7.4 Divertor X-Point Position Control 

a\. The NSTX machine shall include a feedback equilibrium control system
which will provide X-point position control such

• that the location of the outboard X-point can be maintained within
±1.0 cm of nominal. Coil current and voltage requirements (in addition
to those required to accomplish the basic scenario) shall be specified
by NSTX Project Physics

• the location of the outboard X-point can be moved ±12 cm along the
divertor surface with a response time of 2.0 seconds. Coil current and
voltage requirements (in addition to those required to accomplish the
basic scenario) shall be specified by NSTX Project Physics

[2.7.5 Field Errors]{.underline}

a\. To avoid locked modes from non-axisymmetric fields (including those
from coil misalignment, bus work, coil feeds, coil cross-overs, and
magnetic materials), the m=2 n=1 component of the vacuum error field (at
the q=2 surface) shall be limited to gauss[^3]. If necessary,
compensation coils must be installed.

## 2.8 Plasma Disruptions

### 

a\. The device shall be designed to accommodate major disruptions
characterized by:

• vertical or radial displacement

• a thermal quench occurring in 0.1‑1 ms

• a current decay with a time-varying decay rate, such that the peak
rate is ≤0. 1 MA/ms

• a peak poloidal halo current up to 10% of the maximum plasma current
prior to the disruption, with a toroidal peaking factor of 2:1; that is,
the toroidal dependence of the halo current is \[1 + cos ( - 0)\], for
all toroidal phase angles 0 from 0 to 2\*π. Halo current entry/exit
locations shall assume a separation of 1.0m with vertical displacement +
or - 0.25m about the midplane.

• a frequency of occurrence of 50 % in any phase or mode of operation.

# 

# 3 Design Criteria

## 

## 3.1 General Design Guidelines

a\. General design guidelines[^4] for various operating conditions,
based on probability of occurrence, are provided in Table 4.1-1.

 

**Table 3.1-1: General Design Guidelines**

  ------------- ------------------------ -------------- ------------------------
  **Operating   **Description**          **P,           **General Design
  Condition**                            Probability Of Guidelines**
                                         Occurrence In  
                                         A Year**       

  Normal Events Events that are planned  P=1            Provide safe and
                to occur regularly in                   reliable operation
                the course of facility                  
                operation                               

  Anticipated   Events of moderate       1\>P≥10-2      The facility should be
  Events        frequency which may                     capable of returning to
                occur once or more in                   operation without
                the lifetime of a                       extensive corrective
                facility                                action or repair

  Unlikely      Events which are not     10-2\>P≥10-4   The facility should be
  Events        anticipated but which                   capable of returning to
                may occur during the                    operation following
                lifetime of a facility                  potentially extensive
                                                        corrective actions or
                                                        repairs, as necessary

  Extremely     Events which are         10-4\>P≥10-6   Facility damage may
  Unlikely      limiting faults and are                 preclude returning to
  Events        not expected to occur                   operation
                during the lifetime of a                
                facility but are                        
                postulated because of                   
                their safety                            
                consequences                            

  Incredible    Events of extremely low  P\<10-6        Not considered in the
  Events        probability of                          design
                occurrence or of                        
                non-mechanistic origin                  
  ------------- ------------------------ -------------- ------------------------

## 3.2 Facilities Design Criteria

b\. The NSTX torus structure shall be designed to satisfy the Department
of Energy (DOE) standard for natural phenomena hazard (NPH) events[^5].
Only the effects of earthquake shall be considered for the NSTX torus
structure. DOE requires the use of Performance Categories (PC) to
specify the relative risk, environmental impact, importance, and cost of
each facility. The assessment for seismic loading and evaluation for
seismic response shall be followed to determine that the design of the
structure is acceptable with respect to the performance goals[^6]. There
are no safety class items associated with the NSTX machine since its
failure would not result in the release of significant quantities of
hazardous materials. On this basis the seismic performance goal for NSTX
torus structure is to maintain worker safety and it shall be placed in
NPH Performance Category 1 (PC-1). Those SSCs whose failure would
adversely effect the performance of the NSTX torus structure or create a
threat to worker safety shall also be placed in PC-1. All other systems
shall be placed in PC-0 and will thus have no seismic design
requirements.

The DOE design criteria5 allow the PC-1 structures, systems, and
components (SSC) to be designed using the simplified approaches
specified in building code, such as Uniform Building Code (UBC)[^7]. The
NSTX torus structure shall be installed in the D-site Hot Cell. The
seismic design shall consider the response to the motion of the machine
floor rather than the ground motion. According to UBC code, static
analysis approach may be used for determining the seismic effects. For
PC-1 SSCs the design forces may be based on the total lateral seismic
forces Fp given by UBC provisions:

Fp = Z I Cp WP = 0.135 Wp

Where:

Z = a seismic zone factor. For PPPL , Z=0.09g[^8]

I = an importance factor. For PC-1, I = 1.00

Cp = a horizontal force factor. Cp = 1.5 for non-rigid elements.

Wp = the weight of element or component

The lateral force shall be distributed in proportion to the mass
distribution of the machine. Forces shall be applied in the horizontal
directions that result in the most critical loadings for design.

b\. NSTX conventional facilities shall be designed in accordance with
DOE 6430.1A General Design Criteria and applicable national codes
referenced therein.

# 

# 4 Environmental, Safety, and Health (ES&H) Requirements

## 

## 4.1 Policy Statement

a\. The design, manufacture, fabrication, construction, installation,
test, operation, maintenance, modification, and eventual decontamination
and decommissioning of the NSTX shall be accomplished in a manner that
will protect personnel, visitors, the public, property and the
environment from injury. Pursuant to this policy, the NSTX project
shall:

• Comply with all applicable Federal, State, Local, and PPPL ES&H
regulations;

• Assess and minimize the risks inherent in the NSTX program;

• Actively encourage ES&H awareness on the part of NSTX personnel and
visitors.

In particular, NSTX shall be designed and operated in accordance with
DOE Orders and PPPL Environment, Safety and Health Directives. In the
event of conflicts between DOE Orders and PPPL Environment, Safety and
Health Directives, DOE Orders shall take precedence.

## 4.2 Radiological Design Objectives

a\. All operations must be planned to incorporate the radiation safety
guidelines, practices, and procedures included in PPPL ES&HD 5008,
Section 10.

b\. Radiological design objectives and regulatory limits to be observed
in the design and operation of the NSTX facility[^9] are defined in
Table 4.2-1.

**Table 4.2-1: Radiological Design Objectives**

+--------+----------+---------+------------+--------+--------+-------+
|        |          | **P,    | **Public   |        | **     |       |
|        |          | Probab  | Expos      |        | Occupa |       |
|        |          | ility** | ure**[^10] |        | tional |       |
|        |          |         |            |        | Expo   |       |
|        |          |         |            |        | sure** |       |
+--------+----------+---------+------------+--------+--------+-------+
| Con    |          | Of      | Regulatory | Design | Regu   | D     |
| dition |          | Occ     |            |        | latory | esign |
|        |          | urrence | Limit      | Obj    |        |       |
|        |          |         |            | ective | Limit  | Obje  |
|        |          | In A    | (rem per   |        |        | ctive |
|        |          | Year    | yr)        | (rem   | (rem   |       |
|        |          |         |            | per    | per    | (rem  |
|        |          |         |            | yr)    | yr)    | per   |
|        |          |         |            |        |        | yr)   |
+--------+----------+---------+------------+--------+--------+-------+
| R      | Normal   | P≥1     | 0.1 total  | 0.01   | 5      | 1     |
| outine | Op       |         |            | total  |        |       |
| Op     | erations |         | 0.01       |        |        |       |
| eratio |          |         | air        |        |        |       |
| n[^11] |          |         | borne[^12] |        |        |       |
|        |          |         |            |        |        |       |
|        |          |         | 0.004      |        |        |       |
|        |          |         | drinking   |        |        |       |
|        |          |         | water      |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
|        | Ant      | 1\      | 0.5 total  | 0.05   |        |       |
|        | icipated | >P≥10-2 | (including | per    |        |       |
|        | Events   |         |            |        |        |       |
|        |          |         | normal     | event  |        |       |
|        |          |         | operation) |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
| Ac     | Unlikely | 10-2\   | 2.5        | 0.5    | re     | ref13 |
| cident | Events   | >P≥10-4 |            |        | f[^14] |       |
| s[^13] |          |         |            |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
|        | E        | 10-4\   | 25         | 5[^15] | re     | ref15 |
|        | xtremely | >P≥10-6 |            |        | f[^16] |       |
|        | Unlikely |         |            |        |        |       |
|        | Events   |         |            |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
|        | In       | P\<10-6 | NA         | NA     | NA     | NA    |
|        | credible |         |            |        |        |       |
|        | Events   |         |            |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+

# 5 Decontamination and Decommissioning Requirements

a\. A plan for the decontamination and decommissioning (D&D) of NSTX
shall be developed in accordance with DOE Directives.

b\. None of the waste packages projected in the D&D plan to be generated
during the end of life disposal of NSTX (including a small amount of
mixed waste) shall exceed Class A low level waste limits as defined in
existing 10CFR61 regulations.

[^1]: \"Memorandum of Understanding Between PPPL and OFES on the NSTX
    Project Scope & Schedule\", 3/1/98

[^2]: \"NSTX Divertor Heat Flux Estimates\", S. Kaye, 10/24/96

[^3]: \"NSTX Non-Axisymmetric Field Error Tolerances\", S. Kaye,
    12/18/96

[^4]: The definition of operating conditions and general design
    guidelines are consistent with BNL 51444 Rev. 1

[^5]: U.S. Department of Energy, \"Natural Phenomena Hazards Performance
    Categorization Criteria for Structures, Systems, and Components\',
    DOE-STD-1021-93, July. 1993

[^6]: U.S. Department of Energy, \"Natural Phenomena Hazards Design and
    Evaluation Criteria for Department of Energy Facilities\",
    DOE-STD-1020-934 April. 1994

[^7]: \'Uniform Building Code\', 1991 Edition, International Conference
    of Building Officials, Whittier, CA 1991

[^8]: U.S. Department of Energy, \"Guidelines for Use of Probabilistic
    Seismic Hazard Curves at Department of Energy Sites\",
    DOE-STD-1024-92 December, 1992

[^9]: All operations must be planned to incorporate the radiation safety
    guidelines, practices, and procedures included in PPPL EHSD 5008,
    Section 10.

[^10]: Evaluated at the PPPL site boundary.

[^11]: Dose equivalent to an individual from routine operations (rem per
    year unless otherwise indicated)

[^12]: Compliance with this limit is to be determined by calculating the
    highest effective dose equivalent to any member of the public at any
    off site point where there is a residence, school, business, or
    office.

[^13]: Dose equivalent to an individual from an accidental release (rem
    per event)

[^14]: Refer to PPPL EHSD Section 10, Chapter 12 for emergency personnel
    exposure limits.

[^15]: For design basis accidents (DBAs), i.e., postulated accidents or
    natural forces and resulting conditions for which the confinement
    structure, systems, components, and equipment must meet their
    functional goals, the design objective is 0.5 rem.

[^16]: Refer to PPPL EHSD Section 10, Chapter 12 for emergency personnel
    exposure limits.