806a7586 - 1.0 - Interspace Optics Tube Technical Design Description.pdf

ITER UPPER WIDE ANGLE VIEWING SYSTEM PROJECT

55.GA UWAVS-35 TECHNICAL DESIGN DESCRIPTION FOR

INTERSPACE OPTICS TUBE

Sponsored by Oak Ridge National Laboratory c/o Princeton Plasma Physics Laboratory

Under Subcontract No: S013437

Prepared by General Atomics

304243-R00026 Revision A

GA Project 30424

PPPL APPROVAL

VERSION Date Signatory QA Engineer SE External

ITER

Reviewer

Approver

1.0 5/17/2024

Mark Smith Patrick Temple Pete Dugan N/A Ravinder Bhatia

SEE EDRM

Notification

N/A

304243-R00026 Revision A

ITER WIDE ANGLE VIEWING SYSTEM PROJECT

55.GA UWAVS TECHNICAL DESIGN

DESCRIPTION FOR INTERSPACE OPTICS TUBE

Sponsored by Oak Ridge National Laboratory c/o Princeton Plasma Physics Laboratory

Under Subcontract No: S013437

Prepared by General Atomics PO Box 85608

San Diego, CA 92186-5608

GA PROJECT 30424

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55.GA UWAVS TDD for Interspace Optics Tube 304243-R00026/A ii

REVISION HISTORY

Revision Date Description of Changes

A See Watermark Initial Release

POINT OF CONTACT INFORMATION

PREPARED BY:

Name Position Email Phone

Tyler Patterson Mechanical Engineer Tyler.Patterson@ga.com 858-455-3839

APPROVED BY:

Name Position Email Phone

David Chan Quality Engineer David.Chan@ga.com 858-455-3532

Sean McCartney Lead Engineer Sean.McCartney@ga.com 858-248-6652

Anthony Gattuso Program Manager Anthony.Gattuso@ga.com 858-455-2910 ea se d

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TABLE OF CONTENTS

REVISION HISTORY .................................................................................................................. II

POINT OF CONTACT INFORMATION ....................................................................................... II

1 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Definitions

2 SUBSYSTEM OVERVIEW

2.1 Key Functions

2.2 Primary Assemblies

2.3 Functional Flow Block Diagram

2.4 Size, Weight, and Power Summary

3 SUBSYSTEM DETAILED DESIGN DESCRIPTION

3.1 Optical Specifications

3.2 A40 Mirror Group Assembly

3.3 A50 Mirror Group Assembly

3.4 IOT Optical Bench and Enclosure Assembly

3.5 IOT Interface Plate Assembly

3.6 IOT Services Assembly

3.7 Optomechanical Performance Summary

4 SUMMARY OF SUBSYSTEM INTERFACES AND SERVICES

4.1 Interface with Interspace Support Structure

4.2 Interface with Upper Port Services

4.3 Interface with 55.GA Line of Sight

5 INSTRUMENTATION AND CONTROLS

REFERENCES

APPENDIX A IOT SUBSYSTEM MATERIAL SPECIFICATIONS

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LIST OF FIGURES

Figure 1. Coverage of divertor from a) one UWAVS diagnostic and b) five Upper Port UWAVS diagnostics

Figure 2. Definitions of Tokamak directions and global cylindrical coordinate system (a);

Global Port Plug Coordinate System (b)

Figure 3: 55.GA UWAVS diagnostic system

Figure 4. IOT subsystem (a-b) in context and (c) isolated with primary assemblies annotated

Figure 5. IOT subsystem functional flow diagram

Figure 6. Pictorial views of the A40 mirror group assembly (a-b) within the IOT subsystem, with enclosure panels hidden, and (c) isolated

Figure 7. Pictorial view comparison of (a) A40-M1 and (b) A40-M2 mirror subassemblies.

Mirror maximum dimensions noted for reference (local height x width x thickness)

Figure 8. A40-M1 tip-tilt assembly components shown in (a) normal view and (b) zoomed normal view, with mirror cell hidden. Physical architecture common to both A40 mirrors

Figure 9. A40-M1 mirror subassembly physical architecture. Mirror (a) normal, (b) side, and

(c) rear isometric views. Some components transparent for clarity

Figure 10. A40-M2 mirror subassembly physical architecture. Mirror (a) normal, (b) side, and (c) rear isometric views. Some components transparent for clarity

Figure 11. Drivetrain component overview for A40-M2 tip DOF. (a) Rear and (b) zoomed rear mirror views; (c-d) detailed component views

Figure 12. A40 mirror cell assembly flexure retention. (a) Pictorial assembly view and (b-d) isolated component/feature views

Figure 13. Pictorial view of the A50 mirror group assembly (highlighted orange) within the IOT subsystem. Enclosure panels hidden

Figure 14. Pictorial view comparison of all A50 mirror subassemblies. Mirror maximum dimensions noted for reference (local height x width x thickness)

Figure 15. Common A50 mirror mounting physical architecture, shown for the A50-M1 mirror subassembly. (a) Exploded pictorial view and (b-d) pictorial views of primary subassembly components

Figure 16. (a) Pictorial, (b) section, and (c-e) component views of the common A50 mirror group kinematic mount mechanism

Figure 17. (a) Pictorial and (b) normal section views of the A50 mirror group kinematic mount, and face flexure. A50-M1 shown, features common to all A50 mirror subassemblies

Figure 18. Pictorial view of the IOT optical bench and enclosure assembly

Figure 19. (a) Pictorial view of IOT optical bench and (b) typical COTS optical bench cutaway view

Figure 20. Section views of the IOT (a-b) fore and (c-d) aft beam shrouds, with 20 C as-design (red) and estimated worst-case operational (blue) beam paths shown

Figure 21. IOT interface plate assembly (a) pictorial view, (b-c) zoomed pictorial views, and

(d) typical weld-on stud

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Figure 22. Top-down view of the IOT interface plate assembly, with annotations indicating key features of the IOT interface plate

Figure 23. Pictorial view of the interface plate assembly showing installed (background) and exploded (foreground) interface plate pucks and optical bench posts

Figure 24. IOT service assembly (a) contextual and (b) isolated pictorial views, with proposed connectors (inset)

Figure 25. IOT service assembly route and subsystem disconnect shown in (a) portside and

(b) bottom-up views

LIST OF TABLES

Table 1. Applicable CAD models

Table 2. IOT subsystem size, weight, and power summary

Table 3. IOT optical specification summary

Table 4. Optomechanical alignment performance summary for all IOT mirrors

Table 5. Summary of component material specifications for the IOT subsystem ea se d

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ACRONYMS

Acronym Description

ALARA As Low as Reasonably Achievable

BEOC Back End Optics & Cameras

BOL Bio-Shield Optical Labyrinth

CDA Clean Dry Air

CG Center of Gravity

COTS Commercial-off-the-shelf

CP Closure Plate

DOF Degree of Freedom

DSM Diagnostic Shield Module

EM Electromagnetic

EPDM Ethylene Propylene Diene Monomer

EPP Equatorial Port Plug

FDR Final Design Review

FDR Final Design Review

FEA Finite Element Analysis

FEOMS Front End Optical Modular Systems

FEOT Front End Optics Tube

HCC Hard Core Components

I&C Instrumentation & Control

ICD Interface Control Diagram

IO ITER Organization

IOT Interspace Optics Tube

IS Interface Sheet

ISS Interspace Support Structure

LCS Local Coordinate System

MMOI Mass Moment of Inertia

PC Port Cell

PCSS Port Cell Support Structure

PDR Preliminary Design Review

PF Poloidal Field

PI Port Integrator

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Acronym Description

PIC Protection Important Component

QC Quality Class

RBM Rigid Body Motion

RoC Radius of Curvature

ROM Range of Motion

SDDR Shut Down Dose Rate

SDPD System Detailed Performance Definition

SI International System

SPH Spherical

SPS XYP Spherical XY Polynomial

STOP Structural Thermal Optical Performance

SWaP Size Weight and Power

TBD To be Determined

TCWS Tokamak Cooling Water System

TDD Technical Design Description

TF Toroidal Field

TGCS Tokamak Global Coordinate System

UP Upper Port

UWAVS Upper Wide Angle Viewing System

VV Vacuum Vessel ea se d

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1 INTRODUCTION

The 55.GA Upper Port Wide Angle Viewing System (UWAVS) views the divertor in sections and provides machine protection (monitoring for overheating of surfaces), plasma control (basic and advanced), and physics measurement roles. UWAVS is located in UP 2/8 (RFDA), UP 11/14

(USDA) and UP 17 (EUDA). The UWAVS coverage of the divertor is shown in Figure 1.

Figure 1. Coverage of divertor from a) one UWAVS diagnostic and b) five Upper Port UWAVS diagnostics

1.1 Purpose

The purpose of this document is the technical design description (TDD) of the Interspace Optical

Tube (IOT) subsystem, as part of the ITER diagnostic 55.GA Upper Wide Angle Viewing System

(UWAVS). This document is prepared as a deliverable for the Preliminary Design Review (PDR), in accordance with the Sub-System Requirement Document [1] and Statement of Work [2].

The IOT subsystem resides in the ITER Ex-Vessel Interspace and is baselined as an identical design for all five installed instances of UWAVS (Upper Ports 2, 8, 11, 14, and 17). In subsequent sections, the IOT subsystem design is described as follows:

Subsystem overview.

Subsystem detailed design description.

Summary of subsystem interfaces and services.

Summary of subsystem instrumentation and control scheme.

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1.2 Scope

This document provides detailed component design architecture, function, and methodology for the UWAVS (55.GA) IOT subsystem at the preliminary design phase. The IOT subsystem design is common for all five Upper Ports (2, 8, 11, 14, and 17).

High-level definitions of the UWAVS system architecture, decomposition, and functions are described in the UWAVS System Design Description Document [3].

1.3 Definitions

1.3.1 Units

The units of the international system (SI) are used unless otherwise stated.

1.3.2 Coordinate Systems

All loads are specified in the ITER Tokamak Global Cartesian Coordinate System (TGCS) unless otherwise stated. The ITER Tokamak Global Coordinate System mostly used in structural analysis can either be Cartesian (X, Y, Z) or cylindrical (radial - R), toroidal - φ, vertical - Z), as shown in Figure 2. The identifier of the toroidal direction angle φ is counterclockwise when viewed from above. Also, the “poloidal” direction is often used, identifying the (combined radial and vertical direction) perpendicular to the toroidal direction and parallel to the magnetic flux surfaces of the plasma.

Figure 2. Definitions of Tokamak directions and global cylindrical coordinate system (a);

Global Port Plug Coordinate System (b).

a) b)

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1.3.3 Geometry

The CAD geometry referenced throughout this report is listed below in Table 1.

Table 1. Applicable CAD models.

Model CAD File

Native CATIA File UWAVS_IOT_SUBYSYSTEM_ASSY.CATProduct, A.192 ea se d

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2 SUBSYSTEM OVERVIEW

The UWAVS architecture is based on a modular approach that includes key functional subsystems in and outside of the vacuum vessel as shown in Figure 3.

Figure 3: 55.GA UWAVS diagnostic system.

The IOT subsystem resides in the Interspace, supported by the Interspace Support Structure

(ISS). At the fore end (TGCS negative X-direction), the IOT resides immediately next to the Port

Plug Closure Plate and provides a mechanically passive interface with the Vacuum Vessel

Window. At the aft end, the IOT projects the UWAVS line of sight into the Bio-shield Optical

Labrinth (BOL) subsystem. Depending on the port location, surrounding the IOT will be shielding, other diagnostic equipment, and various forms of ITER infrastructure.

2.1 Key Functions

The IOT provides active beam steering to compensate for vacuum vessel thermal displacements during operation and functions as an optical relay, as well as a neutronic dogleg.

2.2 Primary Assemblies

The IOT consists of five assemblies: the A40 mirror group assembly, A50 mirror group assembly, interface plate assembly, optical bench and enclosure assembly, and IOT services assembly.

Figure 4 shows the IOT subsystem and highlights the primary assemblies.

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Figure 4. IOT subsystem (a-b) in context and (c) isolated with primary assemblies annotated.

The A40 mirror group assembly provides active alignment to compensate for relative thermal displacement of the vacuum vessel during operation. The A40 mirror group consists of two parallel flat mirrors, actuated in a combined five degrees of freedom: tip and tilt on both mirrors and piston on A40-M2. Both A40 mirrors are constrained to a holding cell via preloaded flexures, which directly oppose precision-machined reference pads.

The A50 mirror group assembly consists of four large mirrors, with variable surface shapes, which provide an optical relay, as well as neutronic dogleg. Like the A40 mirrors, the A50 mirrors are constrained via preloaded flexures and reference pads. Additionally, each A50 mirror is mounted via a 3-point, ruggedized kinematic mount which allows for fine adjustment of tip, tilt, and piston during initial assembly and alignment. The kinematic mounts will be locked in place for the operational lifespan after initial alignment.

The interface plate assembly facilitates the interface between the IOT and ISS and allows for initial installation alignment to compensate for gross ISS absolute installation tolerances. The optical bench and enclosure assembly provides the primary structural support for the IOT mirror groups, as well as protection from contamination and stray light sources. The IOT services assembly routes electrical power and signal from the ISS interface point to necessary locations within the subsystem. The IOT services assembly also provides disconnect points for both subsystem and component installation and maintenance events.

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2.3 Functional Flow Block Diagram

Figure 5 shows the IOT subsystem block diagram that highlights function, decomposition, and interfaces. Color codes and line types are noted in the legend.

Figure 5. IOT subsystem functional flow diagram.

2.4 Size, Weight, and Power Summary

Table 2 summarizes the IOT subsystem size, weight, and power (SWaP). Maximum dimensions and volume, as well as center of gravity (CG) and primary mass moment of inertia (MMOI) are listed for select items. APPENDIX A provides a notional summary of component material specifications for the IOT subsystem.

A40-M1 A40-M2 A50-M1 A50-M2 A50-M4

INTERSPACE SUPPORT STRUCTURE (ISS)

IOT OPTICAL BENCH

INTERSPACE OPTICAL TUBE (IOT)

BOLFEOMS A50-M2

COOLANT FLOW

SYSTEM BOUNDARY

DATA SIGNAL

POWER INTERFACE

LEGEND

IO

INTERFACES

55.GA

SUBASSEMBLY

PHYSICAL CONNECTION

OPTICAL PATH

AIR PRESSURE

OPTICAL

COMPONENT

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Table 2. IOT subsystem size, weight, and power summary.

REV DESCRIPTION CG_X CG_Y CG_Z MMOI_X MMOI_Y MMOI_Z MAX POWER SUPPLIED

- - - - - [M^3] (INPUT) [KG] [MM] [MM] [MM] [KG-M^2] [KG-M^2] [KG-M^2]

0 A.197 IOT SUBSYSTEM 2.56 1550.65 13992.90 -7.60 5210.62 225.80 2246.34 2211.85 -

1 A.42 INTERFACE PLATE ASSY 0.35 470.95 13872.85 16.38 4950.69 28.83 559.02 587.03 -

2 - (Bulk material) - 463.16 - - - - - - -

2 - Hardware (bolts, helical inserts, etc.) - 7.79 - - - - - - -

1 A.71

OPTICAL BENCH AND ENCLOSURE

ASSY

2.24 757.66 14018.96 -2.11 5324.10 109.86 1017.98 1012.28

Thermocouples (Type K, TBD)

Humidity/particulate (TBD)

2 A.60 IOT OPTICAL BENCH 0.26 367.08 - - - - - - -

2 A.52 A40 ENCLOSURE - 63.23 - - - - - - -

2 A.35 A50 ENCLOSURE - 280.52 - - - - - - -

2 A.14 FORE SHROUD - 8.63 11906.64 -24.12 5446.64 0.11 0.23 0.21 -

2 A.17 AFT SHROUD - 26.43 16064.00 -150.93 5583.78 0.55 2.31 2.31 -

2 - Hardware (bolts, helical inserts, etc.) - 4.03 - - - - - - -

2 - All else (cable trays, tie-downs, etc) 3.71

1 A.55 A40 MIRROR GROUP ASSY - 50.12 - - - - - - -

2 A.49 A40M1 MIRROR SUBASSY - 18.75 12416.35 -18.84 5570.81 0.16 0.16 0.11

Motors (24 VDC, 1.08 A)

Limit switches (250 VAC, 1 A)

Brakes (24 VDC, 3.2 W)

Thermocouples (Type K, TBD)

2 A.40 A40M2 MIRROR SUBASSY - 31.37 12268.14 -96.64 5181.15 0.45 0.32 0.51

Motors (24 VDC, 1.08 A)

Limit switches (250 VAC, 1 A)

Brakes (24 VDC, 3.2 W)

Thermocouples (Type K, TBD)

1 A.37 A50 MIRROR GROUP ASSY - 202.56 - - - - - - -

2 A.30 A50M1 MIRROR SUBASSY - 47.27 13755.85 -201.04 5412.11 1.87 1.45 0.55 Thermocouples (Type K, TBD)

2 A.29 A50M2 MIRROR SUBASSY - 37.43 12571.24 143.04 5277.57 0.89 0.61 0.37 Thermocouples (Type K, TBD)

2 A.17 A50M3 MIRROR SUBASSY - 55.92 15619.46 125.04 5387.43 2.61 1.99 0.82 Thermocouples (Type K, TBD)

2 A.19 A50M4 MIRROR SUBASSY - 61.81 14389.80 -188.85 5435.95 3.18 2.62 0.74 Thermocouples (Type K, TBD)

1 A.19 IOT SERVICES ASSY - 69.39 - - - - - - -

2 -

PLACEHOLDER (CABLING,

CONNECTORS)

- 65.61 - - - - - - -

2 -

PLACEHOLDER (HW, BRACKETS,

ETC.)

- 3.78 - - - - - - -

MASS

MAX

VOLUME

LEVEL

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3 SUBSYSTEM DETAILED DESIGN DESCRIPTION

Subsequent sections discuss the technical details of each primary assembly, as well as how each assembly and its constituent features help achieve the key functions of the IOT subsystem.

3.1 Optical Specifications

Table 3 provides a summary of optical specifications for each of the IOT optics. Each optic will be discussed in in more context (e.g., design, function, performance) throughout subsequent sections. The following notes apply to the optical specifications in Table 3:

RoC = Radius of curvature.

SPS XYP = “XY polynomial” surface shape.

SPH = “spherical” surface shape.

All optics in the IOT are reflective, hence only the front side specifications (coating, RoC) are reported.

For more detailed optical design information see the 55.GA System Detailed Performance

Definition (SDPD) [4].

Table 3. IOT optical specification summary.

Group Optic Material Front Coating Surface Shape

Front RoC (mm)

Thickness (mm)

A40 M1 NBK7 Highly Reflective, Full Bandwidth (Ag+) Flat Inf ~25

A40 M2 NBK7 Highly Reflective, Full Bandwidth (Ag+) Flat Inf ~25

A50 M1 NBK7 Highly Reflective, Full Bandwidth (Ag+) SPS XYP 1E+18 ~25

A50 M2 NBK7 Highly Reflective, Full Bandwidth (Ag+) Flat Inf ~25

A50 M3 NBK7 Highly Reflective, Full Bandwidth (Ag+) SPH 160729.12 ~25

A50 M4 NBK7 Highly Reflective, Full Bandwidth (Ag+) SPS XYP -1E+18 ~25

3.2 A40 Mirror Group Assembly

The IOT A40 mirror group assembly, shown in Figure 6, provides active beam steering to compensate vacuum vessel thermal displacement. The assembly is subject to unique design challenges due to the following constraints:

Large and heavy optics due to optical footprint and material requirements. Each mirror is on the order of 400 x 350 x 25 mm, with a density of approximately 2510 kg/m3

(NBK-7 glass, [5]).

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Minimal spatial clearances from the 55.GA beam path and neighboring components due to general space claim requirements.

Environmental conditions (radiation, electromagnetics, thermal) and compatibility of electromechanical components.

Figure 6. Pictorial views of the A40 mirror group assembly (a-b) within the IOT subsystem, with enclosure panels hidden, and (c) isolated.

The A40 mirror group assembly consists of two individual mirror subassemblies, with remotely actuated local alignment in-situ at each mirror, for a total of five degrees of freedom (A40-M1 tip/tilt, A40-M2 piston/tip/tilt). Each mirror subassembly is mounted to the A40 enclosure separately. The A40 mirror subassemblies share a common physical design architecture, consisting of the following components, as shown in Figure 7.

Mirror mounting bracket (common concept).

Tip-tilt assembly (common concept, customized to each mirror).

Mirror mount cell assembly (common concept, customized to each mirror).

Piston assembly (applicable to A40-M2 only).

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Figure 7. Pictorial view comparison of (a) A40-M1 and (b) A40-M2 mirror subassemblies. Mirror maximum dimensions noted for reference (local height x width x thickness).

The mirror mounting brackets are monolithic 316L stainless steel components with notional lightweighted features. The brackets will be precision machined at select interfaces to maintain the required tolerances and alignment. The bracket bases are aligned to the IOT optical bench and TGCS, while the bulk of the brackets are configured at a compound angle to interface with the A40 mirror positions. The bracket mounting hardware is locked using wedge-lock washers [6] and torque striping. The brackets contain two press-fit counterbores which accept a pair of ball bearings from the tip-tilt assembly. Figure 9 and Figure 10 highlight the key features of the mirror mounting bracket for A40-M1 and A40-M2, respectively.

The tip-tilt assembly is comprised of 316L stainless steel bracketry, 316L (or similar) stainless steel shafts and bearings, and commercial-off-the-shelf (COTS) stepper motors (with associated drivetrain components). The mirror mounting bracket, along with the cross bracket and yoke bracket form a U-joint, which is in line with the mirror geometric centroid in the local vertical (Y) and transverse (X) directions but offset approximately 69.5 mm in the mirror normal (Z) direction.

This U-joint provides an offset gimbal functionality allowing tip and tilt of the mirror. The tip and tilt axes are aligned orthogonal to one another and held in place by axially aligned groups of 10 mm diameter shafts, ball bearings, and thrust bearings. Figure 8 shows the tip-tilt assembly components in the context of A40-M1; the physical architecture is common to both A40 mirrors.

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Figure 8. A40-M1 tip-tilt assembly components shown in (a) normal view and (b) zoomed normal view, with mirror cell hidden. Physical architecture common to both A40 mirrors.

Each of the tip and tilt axes is remotely actuated by a drivetrain which contains a COTS stepper motor, a standard torque-multiplying (i.e., speed-reducing) gearbox, and a spring-set brake.

A common stepper motor is baselined for tip and tilt of both A40 mirrors, which is size NEMA17 and designed to be radiation-hardened. The tip and tilt axes are driven unidirectionally (to mitigate gearbox resolution backlash), with an open loop control scheme. Two radiation-hardened limit switches are baselined per degree of freedom to provide “home” and “away” feedback. See

Section 3.2.1 for detailed discussion of the remote actuation drivetrain components. Figure 9 and

Figure 10 highlight the key features, as well as local degrees of freedom, of the tip-tilt assembly for A40-M1 and A40-M2, respectively.

The mirror mount cell assembly consists of a mount cell, a glass mirror, and a group of mirror retention flexures. The mount cell is an open-faced monolithic feature made of 316L stainless steel which houses the mirror. The mirror is held in the cell using three face flexures and two edge flexures. Each flexure is located opposite of precision pads or bosses on the mirror mount cell.

See Section 3.2.2 for detailed discussion of mirror retention flexures. Both A40 mirrors are NBK-7 glass, coated with a highly reflective, full bandwidth coating, per the SDPD [4]. Located at the rear face of the mirror mount is an M5 threaded hole pattern which mates with the yoke bracket of the tip-tilt assemblies. Figure 9 and Figure 10 highlight the key features of the mirror mount cell assembly for A40-M1 and A40-M2, respectively.

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Figure 9. A40-M1 mirror subassembly physical architecture. Mirror (a) normal, (b) side, and (c) rear isometric views. Some components transparent for clarity.

The piston assembly is unique to the A40-M2 mirror subassembly and, as such, provides the entirety of piston alignment for the A40 mirror group assembly. The piston assembly is comprised of a 316L stainless steel welded bracket, a custom linear stage made of 316L (or similar) stainless steel, and a COTS stepper motor (with associated drivetrain components).

The bracket and stage combine to provide an offset piston functionality, which is aligned with the

IOT axial direction (TGCS X-direction). The stage provides low-resistance, high durability actuation using COTS 15 mm stainless steel rails and ball bearing carriages. All hardware is locked using wedge-lock washers [6] and torque striping.

The piston axis is remotely actuated by a drivetrain which contains a COTS stepper motor, a standard torque-multiplying (i.e., speed-reducing) gearbox, and a spring-set brake. The piston drivetrain components are common with the tip-tilt assembly, apart from requiring unique mounting and gear ratio considerations. See Section 3.2.1 for detailed discussion of the remote actuation drivetrain components. Figure 10 highlights the key features, as well as local degree of freedom, of the piston assembly for A40-M2.

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Figure 10. A40-M2 mirror subassembly physical architecture. Mirror (a) normal, (b) side, and

(c) rear isometric views. Some components transparent for clarity.

3.2.1 A40 Remote Actuation Drivetrain Components

The A40 mirror group assembly achieves the beam steering function using remotely controlled actuation of electromechanical components in five degrees of freedom. Each degree of freedom shares a common drivetrain architecture consisting of a COTS stepper motor, a standard torque-multiplying (i.e., speed-reducing) gearbox, and a spring-set brake. Additional COTS drivetrain components are implemented in each DOF to facilitate the local motion, e.g., ball and thrust bearing for tip/tilt, and precision lead screw and linear stage for piston.

The electromechanical components will be controlled using an open-loop scheme, with only

“home/away” feedback provided by radiation-hardened limit switches. The motors and gearboxes will be unidirectionally driven to mitigate gearbox backlash, which would otherwise degrade resolution. The driver/controller will be remotely located in the Diagnostic Hall. The remote location of the driver/controller eliminates radiation concerns, while not exceeding the standard cabling length capacity of the motors (>100 m). For detailed discussion of the instrumentation and control scheme, see Section 5.

As mentioned prior, each DOF shares a common drivetrain physical architecture, with different key specifications, as listed below. Figure 11 shows the implementation of the common drivetrain physical architecture for the A40-M2 tip DOF.

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Actuators, brakes, and gearboxes:

Model RH-U17-2 [7]

Radiation-hardened, double stage stepper motor, size NEMA17, with spring set brake

32 oz-in static hold torque; 18.2 oz-in detent/brake torque

1.8 deg standard full step (micro-stepping available)

Inline and right-angle torque-multiplying gearboxes (variable gear ratio, per DOF)

Precision lead screw for piston (A40-M2 piston DOF only)

Unidirectional drive (to mitigate gearbox backlash/resolution hit)

Cabling run >150 m (without amplification/relay)

Supplemental components: ball bearings, thrust bearings, linear guide rails and ball bearing carriages

Feedback sensors:

Model 363-SWITCH-RAD1 [8]

Radiation-hardened limit switch, for “home/away” feedback

Driver/Controller:

DMC-41x3 [9]

Motion controller with up to 8 axes (quantity one controller, per port installation of UWAVS)

Open-loop control scheme

Located in Diagnostic Hall

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Figure 11. Drivetrain component overview for A40-M2 tip DOF. (a) Rear and (b) zoomed rear mirror views; (c-d) detailed component views.

The baselined drivetrain components and specifications listed above provide a minimum design margin of at least 20% with respect to maximum static torque, or load requirements. The electromechanical drivetrain components have also been screened for the environmental conditions in the Interspace; namely: radiation, electromagnetic, and thermal conditions. More detailed environmental verification will be completed during the final design phase.

See Section 3.7 for a summary of optomechanical performance verification of the A40 mirror group assembly.

3.2.2 A40 Flexure Retention Mechanisms

Elastic flexures are designed to preload and retain mirrors within the mirror mount cells.

Furthermore, the optic contact geometry and material are tuned to maintain contact stress below allowable glass tensile strength limits (13.7 MPa, peak tensile per [10]).

A common mirror flexure design is employed between the IOT A40 and A50 mirror group assemblies. Flexures are designed for adequate performance (i.e., preload, contact stress) based

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Designing for the heaviest mirror results in additional margin for all other lighter mirrors. Using a

5g acceleration in the mirror LCS envelops the worst-case IOT load case of SL-2 and 1G accelerations in TGCS (<12,12,23> m/s2).

Two locations of flexure mechanism are required: the first interfaces with the reflective face of the mirrors, and the second interfaces with the edges of the mirrors. Due to spatial constraints, two geometrical configurations are required. The two configurations share a common physical architecture, with different specifications, as listed below. Figure 12 shows the implementation of the common IOT flexure retention mechanisms for the A40-M1 mirror mount cell assembly.

Face flexure assembly (3X per optic):

17-7 stainless steel flexure and shim(s)

6061-T6 Aluminum contact pad

M5 SHCS bolt and wedge-lock washer

Contact geometry: 25 x 50 mm cylinder (R x L)

Flexure geometry: 10 x 50 x 1 mm (L x W x H, effective beam size)

Edge flexure assembly (2X per optic):

17-7 stainless steel flexure and shim(s)

6061-T6 Aluminum contact pad

M4 SHCS bolt and wedge-lock washer

Contact geometry: 50 x 20 mm cylinder (R x L)

Flexure geometry: 15 x 20 x 1 mm (L x W x H, effective beam size)

Each flexure assembly mounts opposite a precision-machined reference pad on the mirror mount cell. The direct pairing of flexure assemblies and reference pads minimizes mirror misalignment, as well as bending stress. R el ea se d

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Figure 12. A40 mirror cell assembly flexure retention. (a) Pictorial assembly view and (b-d) isolated component/feature views.

3.3 A50 Mirror Group Assembly

The IOT A50 mirror group assembly serves as an optical image relay, as well as a neutronic dogleg as shown in Figure 13. The assembly also provides initial installation alignment compensation at each mirror in three degrees of freedom (DOF): tip, tilt, and piston. The assembly is subject to unique design challenges due to the following constraints:

Large and heavy optics due to optical footprint and material requirements. Each mirror is on the order of 400 x 350 x 25 mm, with a density of approximately 2510 kg/m3 (NBK-7 glass, [5]).

Highly sensitive optics to misalignments and deformations due to prescribed optical surface shapes and 55.GA system imaging requirements.

Minimal spatial clearances from the 55.GA beam path and neighboring components due to general space claim requirements.

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Figure 13. Pictorial view of the A50 mirror group assembly (highlighted orange) within the IOT subsystem. Enclosure panels hidden.

The A50 mirror group assembly consists of four individual mirror subassemblies, each mounted to the IOT optical bench separately. All four of the A50 mirror subassemblies share a common physical design architecture, consisting of the following components (see Figure 14).

Optical bench bracket (common concept, customized to each mirror).

Ruggedized kinematic mount (identical for all mirrors).

Mirror mount cell assembly (common concept, customized to each mirror).

Figure 14. Pictorial view comparison of all A50 mirror subassemblies. Mirror maximum dimensions noted for reference (local height x width x thickness).

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The optical bench brackets are welded 316L stainless steel, with a nominal 15 mm thickness. The brackets will be post-weld machined at select interfaces. The bracket bases and stiffeners are aligned to the IOT optical bench and TGCS, and the mirror mounting plate is configured at a compound angle to interface between the optical bench and the A50 mirror positions. The bracket bases are pinned and bolted to the optical bench using 10 mm pins and M10 bolts, respectively.

The M10 bolts will be locked using wedge-lock washers from [6] and torque striped. The mirror mounting plate contains three press-fit counterbores which accept the ruggedized kinematic mount v-groove features. Figure 15a and Figure 15b highlight the key features of the optical bench bracket.

Discussion of the ruggedized kinematic mount can be found in Section 3.3.1. Figure 15 highlights the key features of the ruggedized kinematic mount.

The mirror mount cell assembly consists of a mount cell, a glass mirror, and a group of mirror retention flexures. The mount cell is an open-faced monolithic feature made of 316L stainless steel. The mirror is held in the cell using three face flexures and two edge flexures. Each flexure is located opposite of precision pads or bosses on the mirror mount cell. See Section 3.3.2 for additional discussion of mirror retention flexures. All four A50 mirrors are NBK-7 glass, coated with a highly reflective, full bandwidth coating, per the SDPD [4]. Located around the perimeter of the mount cell are three threaded bosses, which interface with the ruggedized kinematic mounts.

Figure 15 highlights the key features of the mirror mount cell assembly.

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Figure 15. Common A50 mirror mounting physical architecture, shown for the A50-M1 mirror subassembly. (a) Exploded pictorial view and (b-d) pictorial views of primary subassembly components.

3.3.1 A50 Ruggedized Kinematic Mount Mechanism

The A50 mirrors are secured to the removable modules using a kinematic mechanism that provides fine adjustment at factory assembly to minimize tolerance impact on performance.

The ruggedized kinematic mount mechanism is a multicomponent feature designed to provide repeatable and robust kinematic constraint of the mirrors, with in-situ initial alignment adjustability.

The key components of the kinematic mount are the v-groove, sphere-cylinder nut, and threaded cone, stacked upon one another as shown in Figure 16.

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Figure 16. (a) Pictorial, (b) section, and (c-e) component views of the common A50 mirror group kinematic mount mechanism.

Stacking the v-groove, sphere-cylinder nut, and cone creates a true kinematic constraint, but also maintains lower contact stresses via line or annular contact regions. Other simpler kinematic mounting configurations, for example three spheres in v-grooves, creates unmanageable point contacts. The kinematic constraint is required to provide accurate, adjustable, and repeatable positioning of the mirrors. The lower contact stresses are required to maintain acceptable structural design margin under the expected loads.

Additional features and hardware are required to provide in-situ adjustment (M24 external threads), joint preload (M10 bolt and hardware), and local tip/tilt alignment (M10 spherical washer). After alignment, bolt preload, and final alignment verification, the kinematic mounts are locked into place for operation by spot welding, and torque striped.

Three mounting interfaces complete the kinematic constraint of the mirror. The local vertical

(z-direction) adjustment of the three kinematic mounts using the M24 threads provides in-situ alignment in three degrees of freedom: tip, tilt, and piston.

The baselined kinematic mount components have the key design parameters listed below.

V-groove: 20 mm diameter x 60 degree groove, 440C stainless steel (or similar)

Sphere-Cylinder: 20 mm diameter x 60 degree groove, 440C stainless steel (or similar

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Threaded cone: 20 mm diameter x 60 degree cone, 440C stainless steel (or similar), M24 external threads, 26 mm hex boss for standard wrench

Other hardware: M10 through bolt with standard flat washer and hex nut, M10 spherical washer

3.3.2 A50 Mirror Flexure Retention Mechanisms

A common mirror flexure design is employed between the IOT A40 and A50 mirror group assemblies. Both the face and edge flexures are designed for adequate performance based on the limiting case of the heaviest IOT mirror (A50-M2, ~7 kg). Designing for the heaviest mirror results in additional margin for all other lighter mirrors. See Section 3.2.2 for detailed discussion.

Figure 17 shows the implementation of the common IOT flexure retention mechanisms, for reference.

Figure 17. (a) Pictorial and (b) normal section views of the A50 mirror group kinematic mount, and face flexure. A50-M1 shown, features common to all A50 mirror subassemblies.

3.4 IOT Optical Bench and Enclosure Assembly

The IOT optical bench and enclosure assembly provides structural support and damping, as well as protection from contamination and stray light sources. The assembly also provides the necessary provisions for component access and replacement during maintenance activities. The

IOT optical bench and enclosure assembly consists of the following components, as shown in

Figure 18.

IOT optical bench inseparable assembly.

A40 and A50 enclosure subassemblies.

Fore and aft beam shrouds.

Auxiliary components (e.g., cable tie-downs and trays).

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Figure 18. Pictorial view of the IOT optical bench and enclosure assembly.

The IOT optical bench is baselined as a custom-COTS honeycomb breadboard optical bench.

Honeycomb optical benches are industry standard for optical laboratory environments because of their high stiffness, vibration damping, surface flatness, and functional threaded hole mounting patterns. Standard benches are often configured for more specialized applications, hence the custom-COTS designation. The IOT optical bench is a standard 4 in (101.6 mm) thick bench, with the customized features listed below and shown in Figure 19. See [11] for exemplary optical bench specifications.

Maximum footprint of 3270 x 787 mm (length x width), with cutout sections, and standard

M6 threaded holes on a 25 mm square pattern.

316L (update) stainless steel top/bottom sheets and honeycomb core; edge welded and bonded.

Welded and flush-mount bolt/pin inserts for all primary load bearing points (e.g., bench posts, mirrors, enclosures).

Welded, reinforced, and flush-mount lifting points at four locations along transverse edges.

Radiation-compliant side closeout panels (316L stainless steel).

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Figure 19. (a) Pictorial view of IOT optical bench and (b) typical COTS optical bench cutaway view.

The A40 and A50 enclosure subassemblies mount to the IOT optical bench. While the A50 mirror group mounts directly to the optical bench, the A40 mirror group mounts to the A40 enclosure, which in turn transfers the load to the optical bench. The A40 and A50 enclosures also provide mounting points for auxiliary components such as service cable trays and internal electrical disconnect bulkheads.

Both enclosures are configured from a range of standard metric 316L stainless steel tubing, plates, and panels. Generally, 3-5 mm thick tubing and 3 mm panels are used. Notional panels secured with floating captive hardware (both nuts and screws) enclose all boundaries of the IOT subsystem to facilitate efficient maintenance access.

One beam shroud is mounted to each of the A40 and A50 enclosures to protect the diagnostic line of sight from contamination and stray light as it passes between 55.GA subsystems. Both beam shrouds are designed to provide adequate beam path clearance for the range or operational conditions and deformations. Both beam shrouds are also designed as retractable concentric tubes to allow maintenance access and mechanical compliance between subsystems during operational loading. Figure 20 shows the fore and aft beam shrouds in the context of the IOT subsystem, with estimated optical beam paths as designed (red) and worst-case operational

(blue) conditions.

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The beam shrouds are configured from 316L stainless steel standard sized tubes, custom bushings, and welded flanges for mounting. Large grip handles, spring-loaded plunger pins, and oversized pinholes facilitate in situ shroud retraction and locking at variable lengths.

The fore beam shroud includes an ethylene propylene diene monomer (EPDM) boot in liner with the stainless steel tubes to provide thermomechanical decoupling from the Vacuum Vessel (VV).

The foremost portion of the fore beam shroud is a 316L stainless steel flange with captive M5 hardware for mounting to the VV window housing. The design interface between the fore beam shroud and the VV window housing ensures adequate thermomechanical compliance and environmental (i.e., radiation) compatibility.

Figure 20. Section views of the IOT (a-b) fore and (c-d) aft beam shrouds, with 20 C as-designed (red) and estimated worst-case operational (blue) beam paths shown.

3.5 IOT Interface Plate Assembly

The IOT interface plate assembly facilitates the interface between the IOT and the Interspace

Support Structure (ISS). The IOT interface plate assembly also provides initial installation alignment to overcome significant absolute installation tolerances of the ISS projected in [12]. See

Section 4 for additional information regarding external interfaces. The IOT interface plate assembly consists of the following components, as shown in Figure 21.

IOT interface plate (55.GA and PI shared scope).

Interface plate pucks and hardware (55.GA scope).

Optical bench posts and hardware (55.GA scope).

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Figure 21. IOT interface plate assembly (a) pictorial view, (b-c) zoomed pictorial views, and (d) typical weld-on stud.

The IOT interface plate is owned by the Port Integrator (PI), with 55.GA design input for critical interface features. The interface plate is an 18 mm thick steel plate, trimmed to a

55.GA-determined footprint with four key features, as listed below and shown in Figure 22.

Counterbores for interface plate pucks (12X).

Weld-on M16 threaded studs (16X) and associated 16 mm location clearance pinholes

(2X) for optical bench posts. See [13] for exemplary weld-on studs.

Threaded inserts for hoist rings, or similar lifting equipment interface (exact location and size TBD).

IOT electrical service cutout/passthrough.

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Figure 22. Top-down view of the IOT interface plate assembly, with annotations indicating key features of the IOT interface plate.

The interface plate pucks secure the IOT interface plate to the ISS using M20 bolts and wedge-lock washers [6] in an oversized slot, as shown in Figure 23. Translation of the bolt shank in the slot, combined with rotation of the puck in the interface plate counterbore allow for planar

(local XY) alignment of the IOT interface plate assembly during initial installation.

The optical bench posts mount over the M16 weld-on studs of the interface plate using hex nuts and wedge-lock washers [6]. The posts have adequate clearance for both the weld-on stud flashing, as well as standard wrench clearance around an M16 hex nut.

Two configurations of posts are required, with one configuration containing press-fit precision locating pins to mate with the 16 mm pinholes on the interface plate, as well as a pin and pinhole on the IOT optical bench.

At the bottom side of the posts a 5 mm shim stack is nominal. This shim stack allows for +/- 5 mm coarse vertical (TGCS Z-direction) adjustment during initial installation. At the topside of the posts are M20 helical threaded inserts to accept the mating bolts from the IOT optical bench. Figure 23 shows a configuration of the optical bench posts with press-fit pins.

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Figure 23. Pictorial view of the interface plate assembly showing installed (background) and exploded (foreground) interface plate pucks and optical bench posts.

3.6 IOT Services Assembly

The IOT services assembly facilitates delivery of general services from the Upper Port to internal

IOT components, and provides other auxiliary functions to support installation, removal, and maintenance of the IOT subsystem and its components. Auxiliary service functions consist of, but are not limited to, the following: internal disconnects, cable service loops, cable tie-downs, and service trays/supports.

The baseline design of the IOT only requires electrical power/signal services to be supplied during operation. There is no foreseeable need for active cooling at any time, however a positive-pressure clean dry air (CDA) supply may be desirable during initial installation, as well as maintenance events. See [14] for additional discussion of the baselined on-site assembly plan.

The IOT services assembly consists of the following components, as shown in Figure 25.

IOT internal cable route and disconnects (55.GA scope).

IOT-ISS interface/disconnect (55.GA and PI shared scope).

IOT-ISS cable route and disconnect (PI scope).

The IOT internal cable route facilitates electrical services from the IOT external interface to internal components. The internal cable route provides power/signal to the A40 mirror group for actuation, feedback, and temperature sensing, as well as the A50 mirror group and a handful of locations throughout the IOT subsystem for temperature sensing. Quick-disconnect, military-grade electrical connectors are provided along the internal cable route, near the

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Figure 24. IOT service assembly (a) contextual and (b) isolated pictorial views, with proposed connectors (inset).

The IOT-ISS disconnect provides the service detachment point for subsystem installation and removal. With disconnects located both upstream (internal to IOT) and downstream (ISS) there should be no need to manipulate this disconnect, unless installing or removing the entire IOT subsystem. The IOT-ISS disconnect is notionally designed as a Staubli CombiTac modular connector [16], mounted on the aft-portside of the IOT interface plate.

The IOT-ISS cable route is PI design scope, with 55.GA design ownership ending at the IOT-ISS disconnect. A notional IOT-ISS cable route and ISS disconnect are shown in Figure 25 for reference only.

Internal mounting provisions and external interface requirements (e.g., cable bundle size, interface location) are discussed in Section 3.4 and Section 4, respectively.

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Figure 25. IOT service assembly route and subsystem disconnect shown in

(a) portside and (b) bottom-up views.

3.7 Optomechanical Performance Summary

The optomechanical performance of the IOT subsystem has been validated to a PDR-level of maturity, via two general categories of analysis:

Structural Thermal Optical Performance (STOP) analysis

Tolerance and alignment compensator analysis

A notional IOT subsystem level STOP analysis was completed, as detailed in [17], based on key design parameters (e.g., optical path length, mount material) and preliminary environmental specifications from the 55.GA Ex-Vessel SLS [18]. The results of the STOP analysis indicate acceptable design performance, with detailed verification planned during the final design phase.

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In support of the IOT subsystem level STOP analysis other calculations were performed, including optic-flexure stress calculations and estimated rigid body motion (RBM) of mirror subassemblies using a subsystem level Finite Element Analysis (FEA). The subsystem level FEA summary can be found in [19].

A two-part tolerance analysis was performed by the mechanical [20] and optical [17] teams. A key output of the tolerance analysis was the Range of Motion (ROM) and resolution requirements for the alignment compensators of the A40 and A50 mirror group assemblies, as detailed in Section

3.2.1 and 3.3.1, respectively.

The actively compensated DOFs of A40 combine to provide the beam steering functionality. The

A50 mirror group alignment compensators are considered static, can be adjusted during initial installation, and locked in place for the operational lifespan. Table 4 provides a summary of the required alignment specifications, as compared with the realizable alignment specifications, for all IOT mirrors.

Table 4. Optomechanical alignment performance summary for all IOT mirrors.

For the tip and tilt DOFs (RX, RY) both A40 mirrors have sufficient ROM, but insufficient resolution. The piston DOF of A40-M2 has insufficient ROM, but sufficient resolution.

A50-M1, -M2, and -M3 have sufficient ROM in all DOFs, while A50-M4 has insufficient tip and tilt

ROM (RX, RY). All A50 mirrors have insufficient resolution, in all DOFs.

The shortcomings of the IOT mirror alignment performance will be addressed in the final design phase; first by reviewing (and potentially relaxing) requirements, and second by design modifications to meet requirements.

ROM Res ROM Res ROM Res ROM Res ROM Res ROM Res

A40-M1 Active - - 0.35 0.025 23.39 0.025 - - 64.00 0.650 91.00 0.650

A40-M2 Active -19.5^

(+XX.X)

0.045 0.24 0.025 21.82 0.025 15.00 0.001 54.00 0.650 81.00 0.650

A50-M1 Static 0.20 0.01 10.00 0.08 10.00 0.08 5.00 0.050 23.00 0.230 33.00 0.330

A50-M2 Static 0.20 0.01 10.00 0.08 10.00 0.08 5.00 0.050 23.00 0.230 33.00 0.330

A50-M3 Static 0.20 0.01 10.00 0.08 10.00 0.08 5.00 0.050 24.00 0.240 32.00 0.320

A50-M4 Static 0.20 0.01 100.00 0.10 100.00 0.10 5.00 0.050 24.00 0.240 31.00 0.310

Table Notes:

ROM = Range of Motion; Res = Resolution

^ Greater travel required in negative Z-direction… unilateral ROM planned.

* Preliminary realizable alignment specifications (to be revised)

+/-RX [mrad] +/-RY [mrad] +/-DZ [mm] +/-RX [mrad]Optic ID Alignment

Type

Realizable Alignment Specifications*Required Alignment Specifications +/-DZ [mm] +/-RY [mrad]

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4 SUMMARY OF SUBSYSTEM INTERFACES AND SERVICES

This section provides a brief, high-level summary the IOT subsystem external interfaces and service requirements. Detailed interface descriptions and associated data can be found in the following interface sheets (IS):

55.GA IS for UPP-02 [21].

55.GA IS for UPP-08 [22].

55.GA IS for UPP-11 [23].

55.GA IS for UPP-14 [24].

4.1 Interface with Interspace Support Structure

The IOT subsystem requires one mechanical interface with the ISS. This interface is facilitated by the IOT interface plate assembly, as discussed in Section 3.5. The interface plate falls under the design ownership of the respective Port Integrator, with 55.GA design features implemented, and is common to all instances of UWAVS.

4.2 Interface with Upper Port Services

The IOT subsystem requires only electrical service provisions. These services will be facilitated at one interface bulkhead with the respective Port Integrator and is common to all instances of

UWAVS. See Section 3.6 for additional discussion of the IOT service design, as well as preliminary external interface bulkhead and cable route.

4.3 Interface with 55.GA Line of Sight

The IOT subsystem requires two beam shrouds which interface with the 55.GA optical line of sight, one at both the fore and aft end of the subsystem.