**DESIGN CRITERIA DOCUMENT**

**WBS 1.4.2**

**Drift Tube Linear Accelerator**

###### 

**Date: October 2000**

SNS-104020000-DC0001-R00

**DESIGN CRITERIA DOCUMENT**

**WBS 1.4.2**

**Drift Tube Linear Accelerator**

# 

**Tom Ilg**

Date Published: August 2000

**DESIGN CRITERIA DOCUMENT**

**WBS 1.4.2**

**Drift Tube Linear Accelerator**

# 

# 

August 2000

####### Linac Systems Senior Team Leader

Linac Systems Mechanical Group
Leader\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

DTL Systems Lead
Engineer\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Contents

[1.0 Scope 5](#scope)

[2.0 Functions and system description
6](#functions-and-system-description)

[2.1 RF Structure (WBS 1.4.2.2) 7](#rf-structure-wbs-1.4.2.2)

[2.1.1 Post Coupler Assembly 8](#post-coupler-assembly)

[2.1.2 RF Slug Tuners 8](#rf-slug-tuners)

[2.1.3 Endwalls 8](#endwalls)

[2.1.4 Waveguide Iris 8](#waveguide-iris)

[2.1.5 Monitor Loops 8](#monitor-loops)

[2.2 DTL Drift Tubes (WBS 1.4.2.3) 8](#dtl-drift-tubes-wbs-1.4.2.3)

[2.3 Vacuum System (WBS 1.4.2.4) 8](#vacuum-system-wbs-1.4.2.4)

[2.4 Water System (WBS 1.4.2.5) 9](#water-system-wbs-1.4.2.5)

[2.5 Mechanical Support (WBS 1.4.2.6)
9](#mechanical-support-wbs-1.4.2.6)

[2.6 Alignment System (WBS 1.4.2.6.2)
9](#alignment-system-wbs-1.4.2.6.2)

[2.7 Assembly (WBS 1.4.2.7) 9](#assembly-wbs-1.4.2.7)

[2.8 Installation (WBS 1.4.2.8) 9](#installation-wbs-1.4.2.8)

[3.0 Design Requirements 9](#design-requirements)

[3.1 DTL Requirements 9](#dtl-requirements)

[3.1.1 RF Structure (WBS 1.4.2.2) 10](#rf-structure-wbs-1.4.2.2-1)

[3.1.1.1 RF surfaces 11](#rf-surfaces)

[3.1.1.2 Vacuum seals 11](#vacuum-seals)

[3.1.1.3 Permanent RF seals 11](#permanent-rf-seals)

[3.1.1.4 Demountable RF seals 11](#demountable-rf-seals)

[3.1.2 DTL Tank 11](#dtl-tank)

[3.1.2.1 Tank diameter 11](#tank-diameter)

[3.1.2.2 RF performance 11](#rf-performance)

[3.1.2.3 Tank material 12](#tank-material)

[3.1.2.4 Vacuum load effects 12](#vacuum-load-effects)

[3.1.2.5 Vacuum pumping ports 12](#vacuum-pumping-ports)

[3.1.3 Slug tuner 12](#slug-tuner)

[3.1.3.1 Slug tuner locations 12](#slug-tuner-locations)

[3.1.3.2 Vacuum integrity 13](#vacuum-integrity)

[3.1.4 Post couplers 13](#post-couplers)

[3.1.4.1 Post coupler locations 13](#post-coupler-locations)

[3.1.4.2 Post coupler assembly 13](#post-coupler-assembly-1)

[3.1.4.3 Vacuum integrity 13](#vacuum-integrity-1)

[3.1.5 Endwalls 13](#endwalls-1)

[3.1.5.1 Endwall locations 14](#endwall-locations)

[3.1.5.2 Vacuum integrity 14](#vacuum-integrity-2)

[3.1.6 Waveguide iris 14](#waveguide-iris-1)

[3.1.6.1 Waveguide iris performance 14](#waveguide-iris-performance)

[3.1.6.2 Input power feed connection 14](#input-power-feed-connection)

[3.1.6.3 Waveguide iris location 14](#waveguide-iris-location)

[3.1.6.4 Iris dimensions 14](#iris-dimensions)

[3.1.6.5 Vacuum integrity 14](#vacuum-integrity-3)

[3.1.7 Monitor Loop 15](#monitor-loop)

[3.1.7.1 Monitor Loop Performance 15](#monitor-loop-performance)

[3.1.7.2 Dimensions of Monitor Loop Interface
15](#dimensions-of-monitor-loop-interface)

[3.1.7.3 Monitor Loop Assembly 15](#monitor-loop-assembly)

[3.1.7.4 Vacuum Integrity 15](#vacuum-integrity-4)

[3.1.2 Drift Tubes (WBS 1.4.2.3) 15](#drift-tubes-wbs-1.4.2.3)

[3.1.2.1 Drift-Tube Stems 15](#drift-tube-stems)

[3.1.2.2 Drift-Tube Locations 16](#drift-tube-locations)

[3.1.2.3 Quadrupole Magnets 16](#quadrupole-magnets)

[3.1.2.4 Quadrupole Gradients 16](#quadrupole-gradients)

[3.1.2.5 Alignment Fiducials 16](#alignment-fiducials)

[3.1.2.6 Dimensions of Drift-Tube/Magnet Assemblies
16](#dimensions-of-drift-tubemagnet-assemblies)

[3.1.2.7 Steering dipoles 16](#steering-dipoles)

[3.2 Vacuum System (WBS 1.4.2.4) 17](#vacuum-system-wbs-1.4.2.4-1)

[3.3 Water System (WBS 1.4.2.5) 18](#water-system-wbs-1.4.2.5-1)

[3.4 Mechanical systems (WBS 1.4.2.6)
19](#mechanical-systems-wbs-1.4.2.6)

[3.4.1 Beam centerline location 19](#beam-centerline-location)

[3.4.2 Travel range 19](#travel-range)

[3.4.3 Adjustments 19](#adjustments)

[3.4.4 Support stand fabrication requirements
19](#support-stand-fabrication-requirements)

[3.4.5 Installation of stand 19](#installation-of-stand)

[3.4.6 Electrical grounding 20](#electrical-grounding)

[3.4.7 Dimensions of Support Stand 20](#dimensions-of-support-stand)

[3.5 Alignment system (WBS 1.4.2.6.2)
20](#alignment-system-wbs-1.4.2.6.2-1)

[3.5.1 Alignment requirements 20](#alignment-requirements)

[3.5.2 Alignment environment 20](#alignment-environment)

[3.6 Structural requirements 20](#structural-requirements)

[3.6.1 Seismic requirements 20](#seismic-requirements)

[3.6.2 Vibration and stability 21](#vibration-and-stability)

[3.6.3 Floor loading 21](#floor-loading)

[3.7 Assembly 21](#assembly)

[3.7.1 Assembly 22](#assembly-1)

[3.7.2 Alignment 22](#alignment)

[3.7.3 Low power RF tuning 22](#low-power-rf-tuning)

[3.7.3.1 Low power adjustable endwalls
22](#low-power-adjustable-endwalls)

[3.7.3.2 Low power adjustable post couplers
22](#low-power-adjustable-post-couplers)

[3.7.3.3 Low power adjustable slug tuners
22](#low-power-adjustable-slug-tuners)

[3.7.3.4 Bead-perturbation measurements
22](#bead-perturbation-measurements)

[3.7.4 Assembly and tuning environment
22](#assembly-and-tuning-environment)

[3.7.5 Shipping 22](#shipping)

[3.7.6 Pre-installation check out 23](#pre-installation-check-out)

[3.8 Installation 23](#installation)

[4.0 System Interfaces 24](#system-interfaces)

[4.1 Interfaces within Linac Systems
24](#interfaces-within-linac-systems)

[4.1.1 RF Power 24](#rf-power)

[4.1.2 Coupled-Cavity Linac 24](#coupled-cavity-linac)

[4.1.3 Diagnostics 24](#diagnostics)

[4.2 Interfaces With Other SNS Systems
24](#interfaces-with-other-sns-systems)

[4.2.1 Front-End Systems 24](#front-end-systems)

[4.2.2 Conventional Facilities 24](#conventional-facilities)

[4.2.3 Control Systems 24](#control-systems)

[5.0 Quality Assurance 25](#quality-assurance555555.5555555555555555)

[5.1 General 25](#general)

[5. 2 Tests 25](#tests)

[5.2.1 Engineering Tests 25](#engineering-tests)

[5.3 Quality Conformance Inspections
25](#quality-conformance-inspections)

[5.3.1 Certifications 25](#certifications)

[6.0 Safety Requirements 25](#safety-requirements)

[7.0 Documentation 26](#documentation)

[7.1 Specifications 26](#specifications)

[7.2 Engineering Drawings and Associated Lists
26](#engineering-drawings-and-associated-lists)

[7.3 Technical Manuals and Procedures
26](#technical-manuals-and-procedures)

[7.3.1 Procedures 26](#procedures)

[7.3.2 Manuals 26](#manuals)

[7.4.4 Documentation Numbering 26](#documentation-numbering)

[8.0 Operations and Maintenance Requirements
26](#operations-and-maintenance-requirements)

[8.1 Operating Modes 26](#operating-modes)

[8.2 Surveillance and in-service inspection requirements
26](#surveillance-and-in-service-inspection-requirements)

[8.3 General Maintenance 26](#general-maintenance)

[8.4 Abnormal Events and Recovery Procedures
26](#abnormal-events-and-recovery-procedures)

[9.0 Installation Requirements 27](#installation-requirements)

[10.0 Acceptance Testing Requirements
27](#acceptance-testing-requirements)

[11.0 Commissioning Requirements 27](#commissioning-requirements)

[12.0 Codes and Standards 27](#codes-and-standards)

[12.1 SNS documents 27](#sns-documents)

[12.2 Non-SNS documents and standards
27](#non-sns-documents-and-standards)

[Appendix A 28](#appendix-a)

[Drift tube cell geometry table 28](#drift-tube-cell-geometry-table)

[Appendix B 29](#appendix-b)

[DTL Magnet, Post coupler, and Diagnostics schematic Layout
29](#dtl-magnet-post-coupler-and-diagnostics-schematic-layout)

List of Tables

[Table 3.1.2 DTL RF Structure Summary 10](#__RefHeading___Toc496945641)

[Table 3.1.3 Tank RF Power 11](#__RefHeading___Toc496945642)

[Table 3.1.4 DTL slug tuner configuration
12](#__RefHeading___Toc496945643)

[Table 3.1.5 Post coupler configuration
13](#__RefHeading___Toc496945644)

[Table 3.1.6 Waveguide Iris Performance Requirements
14](#__RefHeading___Toc496945645)

[Table 3.1.7 Monitor Loop Performance Requirements
15](#__RefHeading___Toc496945646)

[Table 3.1.8 Drift Tube/Magnet Assembly Alignment Tolerances
16](#__RefHeading___Toc496945647)

[Table 3.2.1 Vacuum pressure limits along the beamline in the DTL.
17](#__RefHeading___Toc496945648)

[Table 3.2.2 Summary of the DTL vacuum system design parameters.
17](#__RefHeading___Toc496945649)

[Table 3.3.3 DTL drift tubes nominal water cooling system design and
operation parameters. 18](#__RefHeading___Toc496945650)

[Table 3.5.1 DTL alignment budget 20](#__RefHeading___Toc496945651)

**DESIGN CRITERIA DOCUMENT**

**WBS 1.4.2**

.0-1 Specification Tree;

**DRIFT TUBE LINEAR ACCELERATOR**

**OF THE**

**SPALLATION NEUTRON**

**SOURCE**

# 1.0 Scope

This document establishes the performance, design, development, and test
requirements for the Drift Tube Linear Accelerator (DTL). The linac
follows the MEBT and accelerates the H beam from an energy of 2.5 MeV to
970 MeV. Two types of RF structure perform this task. The first
structure is a 402.5‑MHz DTL that accelerates the beam to 86.8 MeV.
Figure 1.1 shows a general schematic of the Spallation Neutron Source
(SNS) Front End and Linac System Layout.

![](media/image2.wmf)

**Figure 1.1 SNS Front End and Linac System Layout**

# 2.0 Functions and system description

The DTL is the first of two accelerators that comprise the Linear
Accelerator of SNS. It accelerates the beam from 2.5 MeV to 86.8 MeV.
Figure 2.1 is a general layout of the 86.8 MeV DTL system and figure 2.2
is a cut-away view of DTL tank 1 assembly showing the functional
components.

![](media/image3.png){width="7.193700787401575in"
height="3.2736220472440944in"}![](media/image4.png){width="7.159055118110237in"
height="2.382677165354331in"}

**Figure 2.1 86.8 MeV DTL system layout**

![](media/image5.png){width="7.189583333333333in"
height="4.397222222222222in"}

Figure 2.2 DTL tank 1 assembly partial cut-away view

*1. Drift tube assembly 2. Drift tube mount assembly 3. Upstream endwall
4. Endwall PMQ 5. Drift tube coolant fitting 6. Endwall coolant fitting
7. Drift tube stem 8. Drift tube alignment target hole 9. Slug tuner
10.Vacuum pumping slots 11. 300 l/s ion pump 12. Ion pump spool piece
13. 6" gate valve with 8"conflat flanges 14. 300 l/s Turbo pump 15.
Turbo pump spool piece with instrumentation ports 16. Endwall alignment
target hole 17. MEBT gate valve flange 18. Endwall RF and vacuum seals
19. Endwall coolant channels 20. Drag support strut 21. Welded support
structure 22. Tank wall coolant channel 23. Tank section interface
flange 24. Drag strut support fitting 25. Waveguide iiris assembly 26.
402.5 MHz window interface 27. Iris waveguide vacuum pumping slots 28. .
Iris waveguide turbo pump 29. Iris waveguide vacuum pump spool piece 30.
Iris waveguide NEG vacuum pump 31. Post coupler assembly 32. Monitor
loop 33.Veritcal support strut 34. Veritcal support fitting 35.
Downstream endwall 36. Lateral support strut and fitting 37. Iris
waveguide mount flange 38. Tank 1b section 39. Tank 1a section. 40. Tank
section RF and vacuum seals 41. Tank section alignment bushing 42. Tank
inside surface or diameter 43. Support stand alignment target hole 44.
Waveguide iris turbo pump gate valve. 45. Intertank beam box 46.
Intertank diagnostics 47. Intertank beam box vacuum pump 48. Endwall
alignment pin 49. Waveguide iris ion gauge. (water system not shown)*

The 402.5-MHz DTL will be based on the Alverez design. Cells are of
length and the transverse focusing period has a length of 6 at 402.5
MHz. A focusing period spans six RF gaps and has a focusing permanent
magnet quadrupole

(PMQ) inside each of the first two drift tubes, followed by a empty
drift tube, followed by defocusing quadrupoles inside the next two drift
tubes, and again followed by a empty drift tube. This layout is called a
FFODDO lattice. In some cases the empty drift tubes will be instrumented
with steering electromagnet dipoles (EMD) and beam position monitors
(BPM) diagnostics. The last four empty drift tubes of each DTL tank will
incorporate an EMD. Starting with DTL tank 2 the first 2 empty drift
tubes in each tank will incorporate a BPM. See appendix B for general
magnet locations. The DTL will have post couplers to stabilize and tune
the longitudinal field distribution.

## 2.1 RF Structure (WBS 1.4.2.2)

The DTL RF structure WBS consists of all items, except for the drift
tube, which is covered in WBS 1.4.2.3, that will see RF fields (tanks,
end walls, tuners, post couplers, and the waveguide iris). The RF
Structure provides a stable platform for an array of drift-tube
assemblies, post coupler assemblies and RF slug tuners. The structure,
or tank, also provides support and interfaces to other beam path
components, the RF system, the water system, and the vacuum system. The
structure contains passages to flow temperature controlled water to
regulate the temperature for frequency control.

### 2.1.1 Post Coupler Assembly

Post couplers provide longitudinal stability to the tank electric field
by providing a transverse field that couples with the drift tube body.
The number of post couplers required per DTL Tank varies, see appendix B
for general layout of post couplers per tank.

### 2.1.2 RF Slug Tuners

One type of static tuners are used to initially tune the tank. Slug
tuners, accessible from outside and underneath the tank, are used to
provide static frequency adjustment to the RF cavity. Slug tuner
penetration length is determined by Aluminum dummy slug tuners used in
the low power tuning process. Adjusting the slug tuner penetration
length is not required during operation.

### 2.1.3 Endwalls

Each tank has two endwalls located at the upstream and downstream end of
the DTL assembly. A total of twelve endwalls are required. Endwalls
provide a vacuum enclosure and RF surface terminations at each end of
the DTL tank assemblies. Endwalls provide for upstream and downstream
cell geometry and incorporate a half drift tube geometry and shape. The
endwalls are part of the FFODDO lattice structure and are required to
provide housings for PMQ's. Toriod diagnostics will be housed in empty
endwalls where available per the FFODDO lattice layout.

### 2.1.4 Waveguide Iris

Each tank has one waveguide iris to couple the RF power to the tank from
the waveguide. Each iris consists of the iris coupling slot, a tapered
waveguide transition, a half height WR2100 waveguide flange, and an
vacuum pumping system located near the 402.5 MHz window interface to
ensure the proper vacuum pressure in the region.

### 2.1.5 Monitor Loops

Each vessel has several monitor loops to sample the cavity field
strength at several points along the tank for feedback control and RF
phase and amplitude measurements.

## 2.2 DTL Drift Tubes (WBS 1.4.2.3)

The DTL is predominately comprised of a series of drift tubes, which the
proton beam passes through. In the DTL the beam undergoes periods of
acceleration separated by periods of drifting. Oscillating the
electrical charge of the drift tubes generates an electric filed between
the drift tubes which accelerates the beam particles, and the particles
drift at a constant velocity while inside the tubes because the electric
fields are shielded from the interior of the tubes. Thus, the tubes are
referred as drift tubes. The PMQ's are located inside the drift tubes
and provide transverse beam focusing within the DTL. The PMQ's must
withstand the operational radiation environment. Twenty-four steering
EMD's will be used to steer the beam, and they will be located in the
last four open drift tubes in each tank. Two empty drift tubes
downstream of the EMD drift tubes will have BPM's installed.

A total of 210 drift tubes assemblies are unevenly distributed within
the six tanks in a FFODDO lattice. Each drift-tube assembly consists
drift-tube body, a cylindrical copper can, and a stem that supports the
drift-tube from the tank and allows water coolant to enter and return
from the drift tube body.

## 2.3 Vacuum System (WBS 1.4.2.4)

The function of the vacuum system is to minimize interactions between
the beam and residual gases within the DTL. The vacuum system for each
tank consists of a set of ion pumps to maintain the vacuum of each tank
at the proper operating level. Each tank has a valve and connection for
a roughing system, that will evacuate the tank from atmospheric pressure
to a level appropriate to start the ion pumps. Each tank has a valve and
connection for backfilling the tank. Instrumentation is provided for
monitoring valve status and vacuum pressure.

## 2.4 Water System (WBS 1.4.2.5)

The cooling system must keep the DTL at an operating temperature of
about 80 F to 85 F. Temperature control and stability must satisfy the
requirements for maintaining cavity resonance control. The system
interfaces with the RF control system.

## 2.5 Mechanical Support (WBS 1.4.2.6)

The mechanical support system is required to support the DTL tanks and
ancillary equipment including vacuum pumps, cooling water manifolds, and
electrical cables. The Support structure is required to provide adequate
stability that meets drift tube stability criteria as well as provide
seismic restraint to the DTL system.

## 2.6 Alignment System (WBS 1.4.2.6.2)

The alignment system is required to measure and properly align each
drift tube within each DTL tank. External alignment features, i.e.
optical target tooling holes, will be provided on each DTL tank for
proper alignment within the LINAC tunnel. The external alignment
features will be referenced to individual DTL endwall surfaces and/or
PMQ magnetic centers.

## 2.7 Assembly (WBS 1.4.2.7)

The DTL assembly process is responsible for assembling all components
from the RF structure, drift tube assemblies, mechanical support, and
portions of the water system. Drift tubes shall be alignment per WBS
1.4.2.6.2 followed by the low power tuning process. The low power tuning
process will provide DTL frequency measurements and adjustments, and
field measurements and adjustments. The WBS is required to provide the
shipping of each assembled and tuned DTL to ORNL. The shipping method
shall protect the contents from all damages, scratches, and marks etc.
during the packaging and shipping process. Contents shall be stabilized
against movement, and prevented from any mechanical or chemical damage
during transportation.

## 2.8 Installation (WBS 1.4.2.8)

The installation process is responsible for installing and locating all
6 DTL tanks from the assembly process (WBS 1.4.2.7) into the LINAC
tunnel including providing longitudinal and transverse alignment, with
respect to a gobal coordinate system or to the appropriate component(s).
All remaining DTL components from WBS 1.4.2.6 Mechanical systems, WBS
1.4.2.5 Water systems, and WBS 1.4.2.6 DTL Vacuum systems will be
install.

# 3.0 Design Requirements

## 3.1 DTL Requirements

Table 3.1 is a summary of the major DTL requirements. Appendix A
contains the DTL drift-tube cell geometer requirements.

**Table 3.1.1 DTL Requirements**

+--------------------------------------------------+-------------------+
| Parameters                                       | Value             |
+--------------------------------------------------+-------------------+
| Input Energy                                     | 2.5 MeV           |
+--------------------------------------------------+-------------------+
| Structure frequency (MHz)                        | 402.5             |
+--------------------------------------------------+-------------------+
| Output Energy (MeV)                              | 86.8              |
+--------------------------------------------------+-------------------+
| Average beam current                             | 2.08 mA           |
+--------------------------------------------------+-------------------+
| Peak macropulse current                          | 52 mA             |
+--------------------------------------------------+-------------------+
| Average macropulse current                       | 36 mA             |
+--------------------------------------------------+-------------------+
| Macropulse repetition rate                       | 60 Hz             |
+--------------------------------------------------+-------------------+
| Macropulse beam period                           | 1.0 msec          |
+--------------------------------------------------+-------------------+
| RF Structure Beam duty factor                    | 7.02 %            |
+--------------------------------------------------+-------------------+
| Physical length (m)                              | 36.5              |
+--------------------------------------------------+-------------------+
| Number of tanks                                  | 6                 |
+--------------------------------------------------+-------------------+
| Total number of cells                            | 214               |
+--------------------------------------------------+-------------------+
| Bore radius (cm)                                 | 1.25              |
+--------------------------------------------------+-------------------+
| Focusing lattice                                 | FFODDO            |
+--------------------------------------------------+-------------------+
| Lattice period length                            | 6                 |
+--------------------------------------------------+-------------------+
| Quadrupole Gradient (kG/cm)                      | 3.5               |
+--------------------------------------------------+-------------------+
| First quadrupole for H^-^ in the vertical plane  | Focusing          |
+--------------------------------------------------+-------------------+
| Number of PMQs                                   | 147               |
+--------------------------------------------------+-------------------+
| Accelerating gradient Eo (MV/m)                  | 3.6               |
+--------------------------------------------------+-------------------+
| Ave. acceleration rate (MeV/m)                   | 2.38              |
|                                                  |                   |
| Beam Height                                      | 50 inches         |
+--------------------------------------------------+-------------------+

### 3.1.1 RF Structure (WBS 1.4.2.2)

Table 3-2 is a summary of the parameters of the RF structure.

[]{#__RefHeading___Toc496945641 .anchor}Table 3.1.2 DTL RF Structure
Summary

  ----------------------------------- -----------------------------------
  Total Number of Drift tubes         210

  Tank #1 Drift tubes + endwalls      59 + 2

  Tank #1 Length                      4.2 m

  Tank #2 Drift tubes + endwalls      47 + 2

  Tank #2 Length                      6.0 m

  Tank #3 Drift tubes + endwalls      33 + 2

  Tank #3 Length                      6.3 m

  Tank #4 Drift tubes + endwalls      27 + 2

  Tank #4 Length                      6.4 m

  Tank #5 Drift tubes + endwalls      23 + 2

  Tank #5 Length                      6.3 m

  Tank #6 Drift tubes + endwalls      21 + 2

  Tank #6 Length                      6.3 m

  Magnet Type                         Permanent Magnet Quadrupole,
                                      Sm~2~CO~17~

  Quad Gradient                       3.7 kG/cm

  Lattice                             FFODDO

  Tank #1 Post couplers               20

  Tank #2 Post couplers               23

  Tank #3 Post couplers               16

  Tank #4 Post couplers               27

  Tank #5 Post couplers               23

  Tank #6 Post couplers               21

  Total DTL Length                    36.5 m

  Drift-Tube Bore Radius              2.5 cm

  Tank Inside Diameter                43.472 cm for tanks 1 & 2, 45 cm
                                      for tanks 3 thru 6

  Kinetic Energy after Tank #1        7.523 MeV

  Kinetic Energy after Tank #2        22.838 MeV

  Kinetic Energy after Tank #3        39.789 MeV

  Kinetic Energy after Tank #4        56.579 MeV

  Kinetic Energy after Tank #5        72.495 MeV

  Kinetic Energy after Tank #6        86.828 MeV
  ----------------------------------- -----------------------------------

.1.1-1 Diagram of DTL Tanks;

#### 3.1.1.1 RF surfaces

All RF surfaces shall have a minimum electrical conductivity of 95% IACS
(International Annealed Copper Standard). Sharp corners shall be
smoothed with a minimum radius of .06" to .09". Surface roughness shall
not exceed 60-inch, and buffing or abrasive polishing is not permitted.
Plating, if required, shall be copper electro-deposited from an acid
bath to a minimum thickness of .002" to .003" (50 m to 80m).
Intermediate nickel plating strikes are permissible. Zinc strikes shall
not be used. Plating thickness shall be inspected using a calibrated
eddy-current type tester or equivalent.

#### Vacuum seals

All vacuum seals shall be of either metallic or elastomer construction
providing the following requirements are meet.

1.  The cumulative radiation dose limit for selected materials do not
    exceed 2.16 x 10^6^ Rads for thirty years.

2.  The total leak rates and outgassing rates shall be minimized to meet
    the required operating base pressure of 1.8410^-7^ Torr (N~2~).

3.  Dual-function (RF and vacuum) seal design is allowed providing items
    1 and 2 above are meet.

#### Permanent RF seals 

RF joints shall be flush with the RF surface and made by welding or
brazing with high conductivity alloys.

#### Demountable RF seals 

All RF seals shall be of metallic construction. Demountable RF seals
shall be used only where permanent joints are impractical. Demountable
seals shall be designed around a sealing element with stored spring
energy. Dual-function (RF and vacuum) seal design is allowed. RF seal
surfaces are to be plated with ether sliver, copper, or gold.

### DTL Tank

#### 3.1.2.1 Tank diameter

The inside diameter of tanks 1 and 2 shall be 17.115.010 inches. The
inside diameter of tanks 3 thru 6 shall be 17.717.010 inches. The inner
surface of each tank shall meet a cylindricity tolerance of .010".
Should a tank, for ease of manufacture or assembly, be constructed of
more than one beamline section, the total concentricity tolerance of the
assembled sections of the tank shall be .005" or less.

.1.1-1 DTL Tank Summary;

#### 3.1.2.2 RF performance

Each tank shall resonate at a frequency of 402.5 MHz at the nominal
operating temperature and vacuum pressure. The RF power required for
each tank at accelerating gradient shall be less than or equal to the
values in Table 3-3.

.2.1.1.1-1 Tank RF Power;

[]{#__RefHeading___Toc496945642 .anchor}Table 3.1.3 Tank RF Power

  ---------------- --------------------------- ---------------------------
  Tank No.         Accelerating gradient       RF Power in MW
                   (MeV/m)                     

  1                Ramped field, 1.13 to 2.97  0.53

  2                Ramped field, 2.98 to 3.6   1.64

  3                3.6                         1.93

  4                3.6                         1.93

  5                3.6                         1.87

  6                Ramped field, 3.6 to 3.77   1.88
  ---------------- --------------------------- ---------------------------

##### 3.2.1.6.5 Performance parameters

The performance parameters of the tanks are as specified in the SNS
parameters list, SNS100000000-PL-0001-R03. Each DTL tank shall be water
cooled to provide resonance frequency control.

#### 3.1.2.3 Tank material

The tanks shall be constructed of low carbon steel and the endwalls of
OFE copper. The design shall allow a safety factor in accordance with
the applicable sections of the ASME Boiler and Pressure Vessel Code,
Section VIII. The tanks shall withstand repeated high vacuum cycling
and/or temperature cycling without deleterious effects on the tank inner
surfaces, vacuum integrity, RF characteristics, or structural rigidity.

#### 3.1.2.4 Vacuum load effects

Allowable deflections of the tank wall and endwalls shall be determined
by analysis. Specifications shall be maintained for the following:
longitudinal field distribution, drift-tube alignment and tank resonant
frequency.

#### 3.1.2.5 Vacuum pumping ports

The apertures of the vacuum pumping ports shall be slotted to minimize
the RF fields in the pumping ports. The slot orientation shall be in the
same direction as the RF currents. The total vacuum pumping conductance
per port shall be 1000 liters/sec or higher to allow for adequate
pumping to achieve the operational base pressure.

### Slug tuner

Slug tuners shall have enough tuning range to correct for all possible
frequency errors resulting from manufacturing tolerances. Minimum
required tuning range for all slug tuners in each tank should be 2 MHz.
Slug tuner diameter shall be 3.75 inches. Aluminum dummy slug tuners
used in the low power tuning process determines slug tuner penetration
length. The slug tuners will carry significant RF currents and will
require water-cooling. The slug tuner assembly shall be constructed of
OFHC copper and allow for water coolant to enter an exit the tuner
assembly.

#### 3.1.3.1 Slug tuner locations

Tank 1 shall have 8 slug tuners. Tanks 2 thru 6 shall have 12 slug
tuners. Slug tuners shall be approximately equally spaced along the
longitudinal axis of each tank. See table 3.1.4 for the slug tuner
configuration.

[]{#__RefHeading___Toc496945643 .anchor}Table 3.1.4 DTL slug tuner
configuration

  ------------------ ---------------------- ------------------------------
  Tank number        Number of slug tuners  Location

  1                  8                      Approximately equally spaced

  2                  12                     Approximately equally spaced

  3                  12                     Approximately equally spaced

  4                  12                     Approximately equally spaced

  5                  12                     Approximately equally spaced

  6                  12                     Approximately equally spaced
  ------------------ ---------------------- ------------------------------

#### 3.1.3.2 Vacuum integrity

The total leak rates and outgassing rates shall be minimized to meet the
required operating base pressure of 1.8410^-7^ Torr (N~2~).

### 3.1.4 Post couplers

The post-stabilizers shall be capable of changing the field distribution
to meet the SNS parameters list, SNS100000000-PL-0001-R03.

#### 3.1.4.1 Post coupler locations

The number locations of post couplers required per DTL Tank varies, see
table 3.1.5 and appendix B for general location of post couplers. The
post couplers shall be nominally located on the drift-tube centerlines.
Post coupler axis orientation and stem penetration shall be determined
experimentally in the DTL cold model.

[]{#__RefHeading___Toc496945644 .anchor}Table 3.1.5 Post coupler
configuration

  ------------- ------------- -------------------------------------------
  Tank number   Number of     Location
                post couplers 

  Tank 1        19            Every third drift tube starting on drift
                              tube #3 of tank 1, alternating sides of
                              tank thereafter

  Tank 2        23            Every two drift tubes starting on drift
                              tube #2 of tank 2, alternating sides of
                              tank thereafter

  Tank 3        16            Every two drift tubes starting on drift
                              tube #2 of tank 3, alternating sides of
                              tank thereafter

  Tank 4        27            Every drift tube starting on drift tube #1
                              of tank 4, alternating sides of tank
                              thereafter

  Tank 5        23            Every drift tube starting on drift tube #1
                              of tank 5, alternating sides of tank
                              thereafter

  Tank 6        21            Every drift tube starting on drift tube #1
                              of tank 6, alternating sides of tank
                              thereafter
  ------------- ------------- -------------------------------------------

All post couplers start on right side of each DTL tank

#### 3.1.4.2 Post coupler assembly

The nominal stem diameter of the post coupler shall be .50". The post
coupler shall have an appropriately sized \"tab\" determined by the cold
model. The post couplers will carry significant RF currents and will
require water-cooling. The post coupler assembly shall be constructed of
OFHC copper and allow for water coolant to enter an exit the post
coupler stem.

#### 3.1.4.3 Vacuum integrity

The total leak rates and outgassing rates shall be minimized to meet the
required operating base pressure of 1.8410^-7^ Torr (N~2~).

### 3.1.5 Endwalls

The endwalls shall be constructed of OFE copper. The endwalls shall
withstand repeated high vacuum cycling and/or temperature cycling
without deleterious effects on the endwall inner surface, vacuum
integrity, or RF characteristics. Endwall nose deflections due to
thermal gradients and vacuum loading shall be minimized to reduced end
cell frequency shifts. Maximum half-cell frequency shift shall be -500
kHz. The endwalls shall be water cooled to control the nose deflections
due RF heating.

#### Endwall locations

Endwalls are located at each end of the each DTL tank. Each endwall
shall have the appropriate half drift geometry required for the
respective cell location. See appendix A for drift tube geometry
information.

#### 3.1.5.2 Vacuum integrity

The total leak rates and outgassing rates shall be minimized to meet the
required operating base pressure of 1.8410^-7^ Torr (N~2~).

### 3.1.6 Waveguide iris

#### 3.1.6.1 Waveguide iris performance

The iris shall have the performance specified in Table 3.1.6. An
appropriately sized vacuum pumping system shall be incorporated to
ensure a pressure of 1.84 x10-8 torr or less in the region between the
window and the iris.

.2.1.3.1-1 Input Power Coupler Performance Requirements;

[]{#__RefHeading___Toc496945645 .anchor}Table 3.1.6 Waveguide Iris
Performance Requirements

  ----------------------------------- -----------------------------------
  Frequency                           402.5 Megahertz

  Peak Power                          2.0 Megawatts

  Pulse Width                         1.6 milliseconds

  Repetition Rate                     60 Hertz

  Max. duty factor                    7.02%

  Average power transmitted           140 kW
  ----------------------------------- -----------------------------------

#### 3.1.6.2 Input power feed connection

The waveguide iris shall mate with the 402.5 MHz window using a
half-height WR2100 waveguide flange.

#### 3.1.6.3 Waveguide iris location

The irises shall be located at approximately the tank midpoints. The
coupler shall be positioned 45o from the top, clockwise as viewed from
the beam input end of the tank. The iris shall be removable from the
tank to allow inspection, repair and replacement.

#### Iris dimensions

The iris slot size shall be nominally .079 inches wide by 3.188 inches
long. Final iris dimensions shall be determined during the low power RF
tuning process.

#### 3.1.6.5 Vacuum integrity

The total leak rates and outgassing rates shall be minimized to meet the
required operating base pressure of 1.8410^-7^ Torr (N~2~).

### 3.1.7 Monitor Loop

#### 3.1.7.1 Monitor Loop Performance

The monitor loops shall have the performance specified in Table 3.1.7

.2.1.3.2-1 Monitor Loop Performance Requirements;

[]{#__RefHeading___Toc496945646 .anchor}Table 3.1.7 Monitor Loop
Performance Requirements

  --------------------------------------- -------------------------------
  Type                                    H type loop

  Output Power at full field              2 Watts

  Pulse Width                             1 millisecond

  Repetition Rate                         60 Hertz

  Output Impedance                        50 Ohms
  --------------------------------------- -------------------------------

#### 3.1.7.2 Dimensions of Monitor Loop Interface

There shall be six (6) monitor loops per tank equally spaced along the
length of the tank. They shall be located 58.5o from the horizontal
centerline, counterclockwise as viewed from the beam input end of the
tank. The loops shall be removable from the tank to allow inspection,
repair and replacement.

#### 3.1.7.3 Monitor Loop Assembly

The following materials shall be used:

Conductors: OFHC copper

Insulators: \>96% Al2O3

The monitor loop shall be flanged to allow removal. The monitor loop
shall mate with a type N connector.

#### 3.1.7.4 Vacuum Integrity

The total leak rates and outgassing rates shall be minimized to meet the
required operating base pressure of 1.8410^-7^ Torr (N~2~).

### 3.1.2 Drift Tubes (WBS 1.4.2.3)

The drift-tubes shall provide a vacuum tight enclosure for the
quadrupole magnet. The vacuum integrity of the drift-tubes shall be
verified using helium leak detection. Unproven materials or processes
shall be thoroughly tested for sparking, vacuum compatibility, and
mechanical and electrical properties. The drift-tubes shall have the
dimensions as specified in Appendix A of this document.

#### 3.1.2.1 Drift-Tube Stems

The stems shall be constructed of stainless steel. The Drift-tube stem
area exposed to RF and vacuum shall be copper plated. They shall have a
water passage in them to maintain the drift-tubes at the tank operating
temperature. Nominal diameter shall be 20 mm.

#### 3.1.2.2 Drift-Tube Locations

The drift-tube assemblies shall be located according to the locations
specified in Appendix A of the Linac SRD, SNS104000000-SR0001-R00. The
magnetic centers shall be aligned using an in situ magnet alignment
system such as a voltage-pulsed-wire apparatus, Reference \"Taut Wire
Alignment of Multiple Permanent Magnet Quadrupoles\". The Drift-Tube/
Magnet Assembly Alignment Tolerances shall be as listed in Table 3-6.

#### 3.1.2.3 Quadrupole Magnets

Quadrupole magnets shall be of the [16 piece]{.mark} permanent magnet
quadrupole design. Pole tip fields of up to 1.2 T are required. Magnetic
field direction and pole position shall be fixed, reference Linac SRD,
and mechanical alignment techniques shall be provided for assembly into
the drift-tube bodies. The quadrupole rotational axis shall be held to
0.5o with respect to the horizontal and vertical alignment. All magnets
shall be characterized for harmonic content and shall be measured at 80%
of aperture for N=3 \@1% of total and N=4 through 6 @ 1/2% of total.
Magnetic center shall be concentric to the drift-tube body to 0.15 mm or
0.3 mm Total Indicator Reading. Magnets shall be axially centered in the
drift-tube body along the beam direction to 0.15 mm.

#### 3.1.2.4 Quadrupole Gradients

The quadrupole magnets shall have the gradients as shown in Appendix A
of this document. The plus (+) gradient indicates that the quadrupole is
X-focusing and the minus (-) gradient indicates that the quadrupole is
Y-focusing. The tolerance on the gradient times length of a quadrupole
is 1%.

.2.2.2.1.1.7-1 Drift-Tube/ Magnet Assembly Alignment Tolerances;

[]{#__RefHeading___Toc496945647 .anchor}Table 3.1.8 Drift Tube/Magnet
Assembly Alignment Tolerances

  -----------------------------------------------------------------------
  Description of Error                        Tolerance
  ------------------------------------------- ---------------------------
  Quadrupole transverse displacement          0.07 mm

  Quadrupole tilt                             5.8 mrad

  Quadrupole roll                             2.5 mrad

  Quadrupole-gradient error                   0.3%
  -----------------------------------------------------------------------

#### .2.2.2.1.1.7-2 Drift-Tube/ Magnet Assembly Tolerance Budget;

#### 

#### 3.1.2.5 Alignment Fiducials

Three precision holes for mounting alignment targets shall be located on
each fixed end flange. Each hole and spotface shall be inspected and the
locations documented with respect to the magnetic center of the end wall
quadrupoles, and the RF surface of the low-energy end wall.

#### 3.1.2.6 Dimensions of Drift-Tube/Magnet Assemblies

The alignment of the quadrupole magnet, drift-tube, and stem shall be as
shown TBD. For the end assemblies, the alignment of the magnet and
drift-tube in the flange shall be as shown in TBD. The tolerances on the
alignments shall be

#### 3.1.2.7 Steering dipoles

Each Steering Magnet shall have a BL product of 1600 Gauss-cm. All
Steering Magnets must fit within an existing Drift Tube design. In order
to avoid a requirement for "soft vacuum", the insulation system shall
not be hygroscopic. The magnets must be able to withstand furnace braze
temperatures with no adverse affect in performance. There will be a
minimum of two horizontal and two vertical magnets per module. See
appendix A for Dipole magnets locations.

## 3.2 Vacuum System (WBS 1.4.2.4)

The primary requirement for the DTL vacuum systems is to provide
sufficient pumping to overcome the surface outgassing of vacuum facing
components and maintain a beam tube pressure that is below the values
required for a 2-mA beam operation. Table 3.4 shows the Vacuum pressure
limits along the beamline in the DTL. Table 3.5 shows the summary of SNS
LINAC vacuum system design parameters.

See the DTL and Coupled cavity vacuum systems design criteria document,
SNS-104020400-TR0002-R01, for a further detail regarding the DTL vacuum
systems requirements.

[]{#__RefHeading___Toc496945648 .anchor}Table 3.2.1 Vacuum pressure
limits along the beamline in the DTL.

  ----------------- ----------------- ----------------- -----------------
  **Linac Section** **DTL Tank**      **Exit Beam       **Max Allowable
                                      Energy**          Pressure**

                    **No.**           **MeV**           **Torr**

  DTL               1                 7.5 (starts at    1.8410^-7^
                                      2.5)              

  DTL               2                 22.8              1.8410^-7^

  DTL               3                 39.8              1.8410^-7^

  DTL               4                 56.6              1.8410^-7^

  DTL               5                 72.5              1.8410^-7^

  DTL               6                 86.8              1.8410^-7^
  ----------------- ----------------- ----------------- -----------------

[]{#__RefHeading___Toc496945649 .anchor}Table 3.2.2 Summary of the DTL
vacuum system design parameters.

+---------------------+------------------------------------------------+
| Parameter           | DTL                                            |
+---------------------+------------------------------------------------+
| Operating Base      | -   Sum of weighted partial pressures of       |
| Pressure (after     |     residual gases \< 1.8410^-7^ Torr          |
| initial outgassing  |                                                |
| and RF              | -   Weighting factors:                         |
| conditioning)       |                                                |
|                     | > He = 0.125                                   |
|                     | >                                              |
|                     | > H~2~ = 0.15                                  |
|                     | >                                              |
|                     | > H~2~O = 0.66                                 |
|                     | >                                              |
|                     | > N~2~ = 1.0                                   |
|                     | >                                              |
|                     | > CO = 1.0                                     |
|                     | >                                              |
|                     | > O~2~ = 1.0                                   |
|                     | >                                              |
|                     | > CO~2~ = 1.5                                  |
+---------------------+------------------------------------------------+
| RF Structure Gas    | -   Initial outgassing before RF conditioning  |
| Load                |     2.510^-9^ Torr-L/s/cm^2^                   |
|                     |                                                |
| (During             | -   Outgassing during RF conditioning = TBD    |
| conditioning        |                                                |
| period)             |                                                |
+---------------------+------------------------------------------------+
| (During             | -   Outgassing during steady-state operating = |
| steady-state        |     1.010^-10^ Torr-L/s/cm^2^                  |
| operation following |                                                |
| all conditioning)   |                                                |
+---------------------+------------------------------------------------+
| Number of           | -   6 DTL tanks with independent vacuum        |
| structures          |     systems                                    |
+---------------------+------------------------------------------------+
| Number of Pumps or  | -   Three, 300 L/s ion pumps per tank          |
| Pumping Stations    |                                                |
|                     | -   One 300 L/s turbo pump and one fore pump   |
|                     |     (turbo/roughing station) per tank          |
|                     |                                                |
|                     | -   One, 1000 L/s NEG pumps and one 70 L/s     |
|                     |     turbo pumps per tank for the one RF window |
+---------------------+------------------------------------------------+
| Valves              | -   Turbo/roughing stations should be able to  |
|                     |     be isolated with valves to provide for     |
|                     |     installation and maintenance issues.       |
|                     |                                                |
|                     | -   Isolation valves will be provided between  |
|                     |     DTL tanks and before tank 1 and after      |
|                     |     tank 6. Note that clearance problems       |
|                     |     prohibit a valve between tanks 1 and 2.    |
+---------------------+------------------------------------------------+
| RF Window Gas Load  | -   Peak gas load during RF conditioning are   |
|                     |     TBD                                        |
+---------------------+------------------------------------------------+
| Control System      | -   One vacuum control system (PLC, computer,  |
| Domain              |     electronics rack, etc) per DTL tank        |
+---------------------+------------------------------------------------+
| Vacuum Interfaces   | -   Vacuum level between DTL and MEBT is 4 x   |
|                     |     10^-7^ Torr                                |
+---------------------+------------------------------------------------+
| Other               | -   Possible water-cooled grid in pumping port |
|                     |     to reduce RF losses                        |
|                     |                                                |
|                     | -   Permanent magnet surface outgassing rate = |
|                     |     TBD Torr/L/s/cm^2^                         |
+---------------------+------------------------------------------------+

## 3.3 Water System (WBS 1.4.2.5)

The DTL water cooling system removes the waste heat from the copper RF
structure and maintains resonance through active temperature control. A
representative set of data for the heat load, water flow rates, water
temperature, and resonance control parameters for the DTL drift tubes is
given in Table 3.9. Further detail and discussions regarding the water
system requirements and design can be found in the DTL and Coupled
cavity water system design criteria document, SNS-104020400-TR0001-R01.

[]{#__RefHeading___Toc496945650 .anchor}Table 3.3.3 DTL drift tubes
nominal water cooling system design and operation parameters.

+-----------------------+-----------------------+-----------------------+
| Parameter             | Value                 | Comments/References   |
+-----------------------+-----------------------+-----------------------+
| -   Nominal heat load | -   0.05-1.85 kW      | Heat load is          |
|     per drift tube    |                       | different for each    |
|                       | -   26.6C (79.9^o^F)  | drift tube            |
| -   Nominal average   |                       |                       |
|     operating         |                       | Average drift tube    |
|     temperature of    |                       | operating temperature |
|     drift tubes       |                       | is identical to       |
|                       |                       | average CCL copper    |
|                       |                       | temperature.          |
+-----------------------+-----------------------+-----------------------+
| -   Nominal water     | -   0.13-3.22x10^-4^  | Flow rate is adjusted |
|     flow rate per     |     m^3^/s (0.2-5.1   | for each individual   |
|     drift tube        |     gpm)              | drift tube. A uniform |
|                       |                       | frequency shift for   |
| -   Water flow rate   | -   6.3x10^-6^ m^3^/s | all cells within a    |
|     accuracy per      |     ( 0.1 gpm)        | tank is obtained by   |
|     drift tube        |                       | balancing the flow    |
|                       | -   6.3x10^-6^ m^3^/s | rate and tailoring    |
| -   Water flow rate   |     ( 0.1 gpm)        | the cooling channels  |
|     resolution and    |                       | for each individual   |
|     stability per     | -   1.                | drift tube.           |
|     drift tube        | 06x10^12^-3.22x10^14^ |                       |
|                       |     Pa/m^6^s          | Flow resistances for  |
| -   Flow resistance   |     (0.61-185.92      | each drift tube are   |
|     across drift      |     psi/gpm^2^)       | estimated from        |
|     tubes             |                       | standard pipe flow    |
|                       |                       | correlations.         |
+-----------------------+-----------------------+-----------------------+
| -   Drift tube water  | -   20.0C (68.0 ^o^F) | Initial drift tube    |
|     inlet temperature |                       | water inlet           |
|     prior to RF power | ```{=html}            | temperature chosen to |
|     and during        | <!-- -->              | equal mean desired    |
|     steady-state,     | ```                   | operating             |
|     full RF power     | -   8.3^o^C           | temperature. Drift    |
|                       |     (14.9^o^F) about  | tube water inlet      |
| ```{=html}            |     mean inlet        | temperature must      |
| <!-- -->              |     temperature       | remain constant as RF |
| ```                   |                       | power is introduced.  |
| -   Temperature range | ```{=html}            | An approximate        |
|     of water          | <!-- -->              | 8.3^o^C band about    |
|                       | ```                   | this mean temperature |
| -   Nominal           | -   0.6-2.6^o^C       | will be required for  |
|     temperature rise  |     (1.1-4.7 ^o^F)    | full resonance        |
|     of cooling water  |                       | control (i.e. to get  |
|     through 1 drift   | -   0.1^o^C           | 50 kHz frequency      |
|     tube              |                       | adjustment).          |
|                       | -   0.1^o^C           |                       |
| -   Temperature       |                       | A 0.4^o^C change in   |
|     accuracy          | ```{=html}            | water temperature     |
|                       | <!-- -->              | corresponds to a      |
| -   Temperature       | ```                   | change in RF          |
|     resolution        | -   0.4^o^C           | frequency of 2.4 to   |
|                       |                       | 2.8 KHz.              |
| -   Temperature       |                       |                       |
|     stability         |                       |                       |
+-----------------------+-----------------------+-----------------------+
| -   Frequency shift   | -   6-7 kHz/1^o^C     | Resonance is          |
|     per change in     |                       | maintained by         |
|     water inlet       | -   50 kHz            | dynamically adjusting |
|     temperature       |                       | the water temperature |
|                       | -   2.5 kHz           | in the drift tube     |
| -   Range of          |                       | circuit and the tank  |
|     frequency control |                       | circuit               |
|                       |                       | simultaneously.       |
| -   Stability in      |                       |                       |
|     frequency control |                       |                       |
+-----------------------+-----------------------+-----------------------+
| -   Chilled water     | -   7.2^o^C           |                       |
|     supply            |     (45.0^o^F)        |                       |
|     temperature       |                       |                       |
|                       | -   0.28C ( 0.5^o^F)  |                       |
| -   Chilled water     |                       |                       |
|     supply            |                       |                       |
|     temperature       |                       |                       |
|     stability         |                       |                       |
+-----------------------+-----------------------+-----------------------+

## 3.4 Mechanical systems (WBS 1.4.2.6)

### 3.4.1 Beam centerline location

Each stand shall locate the nominal beam centerline of each tank at a
height of 50 inches from the floor.

### 3.4.2 Travel range

Support system for technical components must be able to provide
adjustments over a 2-inch vertical range.

### Adjustments

The DTL tanks shall be adjustable in any direction by .50", with respect
to the stand. Positioning precision shall be .005". The support stand
height shall be adjustable in the vertical direction by 1.50" using
shims at the floor and stand interface.

### Support stand fabrication requirements 

All welding shall conform to AWS D1.1-2000. Structural steel tubing
shall conform to ASTM A-500 grade 2 or better.

### 3.4.5 Installation of stand

Each stand shall have provision for permanently securing it to a
concrete floor, once the necessary adjustments have been achieved. All
mounting hardware, brackets, etc., shall be contained within the
envelope of the stand proper. The mounting design shall allow the use of
flat washers and lock washers.

### 3.4.6 Electrical grounding

The DTL tank and its support stand must be securely grounded. A pair of
\"earth\" ground connections shall be provided on each end of the stand.
These connections shall be .500-13unc-2b threaded holes, with at least
five (5) complete threads. All connections shall be on the left side of
the structures, looking \"downstream\". The pair of holes shall be about
4.00 inches apart.

### 3.4.7 Dimensions of Support Stand

The width shall be limited to 36" and the length shall be limited to
that of the tank it supports.

## 3.5 Alignment system (WBS 1.4.2.6.2)

The alignment system is required to measure and properly align each
drift tube within each DTL tank. External alignment features, i.e.
optical target tooling holes, will be provided on each DTL tank for
proper alignment within the LINAC tunnel. The external alignment
features will be referenced to individual DTL endwall surfaces and/or
PMQ magnetic centers.

### 3.5.1 Alignment requirements

Table 3.3.4 shows the required alignment budget for drift tubes and DTL
tanks.

[]{#__RefHeading___Toc496945651 .anchor}Table 3.5.1 DTL alignment budget

+------------------------------------------------+---------------------+
| **Alignment Parameter**                        | **Value (inches)**  |
+------------------------------------------------+---------------------+
| PMQ (drift tube) magnetic centers              | .005 transverse     |
|                                                |                     |
|                                                | .005 longitudinal   |
+------------------------------------------------+---------------------+
| Dipole (drift tube) magnetic centers           | .005 transverse     |
|                                                |                     |
|                                                | .005 longitudinal   |
+------------------------------------------------+---------------------+
| Empty drift tubes geometric centers            | .010 transverse     |
|                                                |                     |
|                                                | .010 longitudinal   |
+------------------------------------------------+---------------------+
| DTL tank to tank                               | .005 transverse     |
|                                                |                     |
| Using endwall PMQ magnetic centers and/or      | .010 longitudinal   |
|                                                |                     |
| Endwall geometric centers                      |                     |
+------------------------------------------------+---------------------+

### 3.5.2 Alignment environment

Drift tube alignment shall be performed in a temperature and vibration
controlled environment. Daily temperature variations in the DTL during
alignment shall not exceed 2 degrees Fahrenheit. Alignment shall not be
performed in proximity to vibration sources such as reciprocating
machinery, i.e. pumps, motors etc.

## 3.6 Structural requirements

### 3.6.1 Seismic requirements

The linac and associated systems must survive a PC-2 earthquake, 0.55g
peak acceleration per DOE-STD-1020-94.

### 3.6.2 Vibration and stability

Performance of the DTL shall not degrade when exposed to the natural
levels of vibration expected at the SNS site. Vibratory motion of drift
tubes with internal PMQs or EMQs shall not have deleterious effects on
beam quality. Drift tube stability criteria = TBD -inch transverse RMS

Figure x-x below shows the estimated baseline vibratory environment to
be used.

![](media/image6.png){width="5.75in" height="4.53125in"}

**Figure 3.6.1 Estimated baseline vibratory environment**

### 3.6.3 Floor loading

Each stand, with its DTL tank installed, shall have a floor load of less
than [TBD]{.mark} pounds per linear foot on a [TBD]{.mark} foot x TBD
foot grid or 2 line loads of [TBD]{.mark} pounds per linear foot
separated by 3 feet or 2 each [TBD]{.mark} pound loads on a 3 foot by 3
foot grid.

## 3.7 Assembly

The DTL assembly process is responsible for assembling all components
from the RF structure, drift tube assemblies, mechanical support, and
portions of the water system. Drift tubes shall be alignment per WBS
1.4.2.6.2 followed by the low power tuning process. The low power tuning
process will provide DTL frequency measurements and adjustments, and
field measurements and adjustments. The WBS is required to provide the
shipping of each assembled and tuned DTL to ORNL. The shipping method
shall protect the contents from all damages, scratches, and marks etc.
during the packaging and shipping process. Contents shall be stabilized
against movement, and prevented from any mechanical or chemical damage
during transportation.

### 3.7.1 Assembly

### 3.7.2 Alignment

See section 3.5 of this document.

### 3.7.3 Low power RF tuning

Low power RF tuning shall provide DTL frequency measurements and
adjustments, and field measurements and adjustments. Bead-perturbation
measurements shall be used to aid in the tuning process. Adjustable
tuning components or dummy endwalls, post couplers, and slug tuner shall
be used to aid in the field and frequency adjustments. All low power RF
tuning measurements shall meet parameters specified in the SNS
parameters list, SNS-10000000-PL001-R03.

#### 3.7.3.1 Low power adjustable endwalls

Each low endwall drift tube nose shall have an adjustable range of 0.120
inches. The endwall nose shall not come in contact with the drift tubes.
Each endwall nose shall have the required geometry per appendix A of
this document. The low power endwalls shall be made from Aluminum
6061-T6. No copper plating is required. RF seasl are required per
sections 3.1.1.3 and 3.1.1.4 of this document.

#### 3.7.3.2 Low power adjustable post couplers

Each low post coupler shall have 360 rotational adjustments and a full
tank penetration adjustment. The rotational adjustment shall have an
accuracy of 0.50. The penetration adjustment shall have an accuracy of
0.020 inches. The post coupler tip shall not come in contact with the
drift tubes. The low power post coupler shall be made from Aluminum
6061-T6. No copper plating is required. Low power post couplers
quantities and locations shall be per section 3.1.4 and appendix A of
this document. RF seals are required per sections 3.1.1.3 and 3.1.1.4 of
this document.

#### 3.7.3.3 Low power adjustable slug tuners

Each low power slug tuner shall have a tank penetration adjustment of
3.00 inches 0.020 inches. The low power slug tuner shall be made from
Aluminum 6061-T6. No copper plating is required. Low power slug tuner
quantities and locations shall be per section 3.1.3 of this document. RF
seals are required per sections 3.1.1.3 and 3.1.1.4 of this document.

#### 3.7.3.4 Bead-perturbation measurements

The bead-perturbation measurements measure the field tilt sensitivity.
Post couplers will be adjusted to set the field distribution. The
bead-perturbation measurements shall be performed on each DTL tank
individually. The bead-perturbation measurement will use a 0.25-inch
diameter hollow aluminum bead attached to an 8-pound test nylon fishing
line. The bead shall pass thru the endwalls and drift tubes of each tank
at a constant rate of approximately 5 inches per second. The nylon line
shall not deflect more than 0.002 inches.

### 3.7.4 Assembly and tuning environment

Assembly and RF tuning shall be performed in a temperature and vibration
controlled environment. Daily temperature variations shall not exceed 2
degrees Fahrenheit. Alignment and tuning shall not be performed in
proximity to vibration sources such as reciprocating machinery, i.e.
pumps, motors etc.

### 3.7.5 Shipping

The shipping method shall protect each DTL assembly and all attached
components from all damage, scratches, and marks etc. during the
packaging, shipping, and un-packaging processes. Each DTL assembly shall
be stabilized against movement, and prevented from any mechanical or
chemical damage during transportation. A temperature between 65 F and
90F shall be maintained during the packaging, shipping, and un-packaging
processes.

*Further detail will be provided during title II (final design) phase of
this project.*

### 3.7.6 Pre-installation check out

The pre-installation check out shall consist of the following steps:

1.  Un-pack the DTL tank assemblies and components

2.  Check for external damage

3.  Using the bead-perturbation measurements, verify RF stability and
    distribution has not changed during the shipping process.

4.  Using the optical alignment system, verify the drift transverse
    alignment has not changed during the shipping process.

5.  *Further detail will be provided during title II (final design)
    phase of this project*

## 3.8 Installation

The installation process is responsible for installing and locating all
6 DTL tanks from the assembly process (WBS 1.4.2.7) into the LINAC
tunnel including providing longitudinal and transverse alignment, with
respect to a gobal coordinate system or to the appropriate component(s).
All remaining DTL components from WBS 1.4.2.6 Mechanical systems, WBS
1.4.2.5 Water systems, and WBS 1.4.2.6 DTL Vacuum systems will be
install.

*Further detail will be provided during title II (final design) phase of
this project*.

# 4.0 System Interfaces

The DTL has interfaces with a number of other WBS elements as listed
below. The location of the interface, details of the hardware that forms
the physical interface, and the parameters that define the function
interface, between the DTL and these respective systems are outlined
below and will be completely defined in separate interface control
documents developed during detail design.

## 4.1 Interfaces within Linac Systems

### 4.1.1 RF Power

*a. RF Power*

Function: 402.5 MHz power is provided by the RF system to accelerate the
beam.

Physical: Half height WR2100 waveguide flange below the 402.5 MHz Rf
window including an interface

flange for an arc detector located on the iris waveguide.

*b. RF Controls*

Function: The DTL monitor loop provides cavity field information.

Physical: At the N-type coax connector provided on the DTL.

### 4.1.2 Coupled-Cavity Linac

Function: Continuation of accelerating structure past the DTL.

Physical: The beam flange past the DTL-supplied gate valve with a
flexible bellows connection for mechanical compliance.

### 4.1.3 Diagnostics

Function: Diagnostics are incorporated throughout the DTL beamline to
provide beam physics information.

Physical: See appendix B for general location of beam diagnostics.

## 4.2 Interfaces With Other SNS Systems

### 4.2.1 Front-End Systems

Function: Medium-energy beam transport between the radio-frequency
quadrupole and the DTL.

Physical: See drawing 155Y504100, MEBT/DTL interface control drawing.

### 4.2.2 Conventional Facilities

Functional interfaces to Conventional Facilities (WBS 1.8) are
identified in the Systems Requirements Document for the Title I Design
of the Front End Building, the Linac Tunnel, and the Klystron Building,
SNS10830000SR0001.

### 4.2.3 Control Systems

See the vacuum system design criteria document,
SNS-104020400-TR0002-R01, for the vacuum system control requirements.

See the water system design criteria document, SNS-104020400-TR0001-R01,
for the water system control requirements. See the control systems
design criteria document, document number TBD, for the general control
system requirements..0 QUALITY ASSURANCE;

## 

# 5.0 Quality Assurance555555.5555555555555555

## 5.1 General

All activities associated with the DTL will be conducted in accordance
with the requirements contained in SNS-QA-P01, SNS QA Plan; and accepted
engineering standards and practices. Good engineering practices within
the established design process will ensure future safe and reliable
operation of the SNS, and mitigate conditions that could pose a threat
to success. In all cases, consensus standards will be used to accomplish
design activities. Where existing standards do not adequately control an
activity, appropriate administrative controls will be considered.

Thoughtfully derived and properly "graded" controls for design,
manufacture, installation, testing, and operation of the remote handling
systems will be established prior to execution of each of these
activities. Additional controls will only be proposed in cases where
they enhance success.

Successful QA program performance will be verified through validation
activities such as design reviews, surveillance activities, inspections,
tests, and readiness reviews.

## 5. 2 Tests

### 5.2.1 Engineering Tests

Tests used primarily for the purpose of acquiring data to support the
design and development shall be specified in the individual development
and product specifications.

## 5.3 Quality Conformance Inspections

DTL tank design and performance requirements identified in this
specification and referenced specifications shall be verified by
inspection, analysis, demonstration, similarity, test, or a combination
of these.

### 5.3.1 Certifications

A copy of inspection and test records and certifications relating to the
requirements associated with the following parameters, as a minimum
shall be prepared:

a.  PMQ magnet mapping

b.  Endwall alignment mapping

c.  Drift tube alignment measurements

d.  Final electric field distribution and tilt sensitivity tests

e.  Frequencies measurements

f.  Vacuum leak checks

g.  Hydrostatic leak checks

h.  Inspection reports on fabricated components

# 6.0 Safety Requirements

The DTL shall meet all applicable Department of Energy and other Federal
safety regulations, plus those applicable State, Local, and SNS safety
requirements, and the SNS Environment, Safety, and Health (ES&H) Plan. A
hazard analysis shall be conducted in conjunction with the design of the
DTL tanks. Particular emphasis shall be placed on restricting the use of
hazardous materials where possible; grounding of electrical systems; RF
radiation emission; cleanliness. RF leakage shall conform to the
requirements of ANSI C95.1-1982.

# 7.0 Documentation

Technical documentation shall be delivered, sufficient in level of
detail, type and quality to allow re-procurement and satisfy the SNS
documentation standards and practices. Electronic, PDF files shall be
provided. The technical documentation package shall include the
following.

## 7.1 Specifications

The following specifications shall be developed:

a\. Fabrication Specification establishing the requirements for
manufacture and acceptance of the DTL tanks and components.

b\. Process Specifications defining specific process involved in
manufacturing techniques.

c\. Material specifications defining raw materials and semi-fabricated
material (e.g. electrical cable, piping)

d\. Interface Control Documents specifying the interfaces for beam input
from the MEBT.

## 7.2 Engineering Drawings and Associated Lists

Drawings and associated lists shall be provided. SNS Drawing Numbering
System, and Global Drafting Manual, supplemented by procedures and
instructions pertinent to SNS only, shall be used as guides.

## 7.3 Technical Manuals and Procedures

### 7.3.1 Procedures 

Procedures shall be provided for, at minimum,

a\) initial installation and set-up of equipment

b\) normal operation of equipment

c\) normal and/or preventative maintenance

d\) a troubleshooting guide for any anticipated potential malfunctions

### 7.3.2 Manuals

Manuals shall be provided for, at minimum, all purchased components and
subsystems delivered to SNS.

### 7.4.4 Documentation Numbering

The SNS document numbering procedure shall be followed.

# 8.0 Operations and Maintenance Requirements

## 8.1 Operating Modes

The DTL normal operating mode is with beam on. The water system has
multiple operating modes, see the DTL and Coupled cavity water system
design criteria document, SNS-104020400-TR0001-R01.

## 8.2 Surveillance and in-service inspection requirements

No design requirements have been identified.

## 8.3 General Maintenance

No design requirements have been identified.

## 8.4 Abnormal Events and Recovery Procedures

No design requirements have been identified.

# 9.0 Installation Requirements

TBD

# 10.0 Acceptance Testing Requirements

TBD

# 11.0 Commissioning Requirements

TBD

# 12.0 Codes and Standards

The DTL systems shall be designed in accordance with the codes and
standards of record as evoked by the Systems Requirements Document for
the SNS Linear Accelerator and the following:

## 12.1 SNS documents

SNS Environment, Safety, and Health (ES&H) Plan," (Reference Doc No:
102030000ES0001R00, 12-1-99)

SNS-QA-P01, SNS QA Plan; Quality Assurance Plan for the Target System of
the Spallation Neutron Source Project, Title I (Preliminary Engineering
Design).

SNS Systems Requirements Document for Equipment, Device and Signal
Naming,\" SNS 102000000 SR0001-R00

System Requirements Document for Title I Design of the Front-end
Building, the Linac Tunnel and the Klystron Building," SNS
108030000SR000

## 12.2 Non-SNS documents and standards

American Welding Society AWS D1.1-2000, Structural Welding Code - Steel

American Society of Mechanical Engineers, ASME NOG-1

490 Specification Practices

Global Drafting Standard

Dimensioning and Tolerancing per ASME Y14.5M-1994

ASME Boiler and Pressure Vessel Code. Section VIII

ANSI C95.1-1982 American National Safety Standard Levels with respect to
Human Exposure to Radio Frequency Electromagnetic Fields (300
kHz-100GHz)

Structural Steel Tubing per ASTM A-500

# Appendix A 

## Drift tube cell geometry table

Face angles are in degrees

All other parameters are in inches

Tk = DTL tank number

DT = Drift tube number in respective tank

CellLen = Cell Length

CellLoc = Cell location from start of MEBT

Zstem = center of drift tube from tank upstream endwall

FA_1 = Face angle of upstream drift tube

FA_2 = Face angle of downstream drift tube

Flat_1 = Distance between tangencies of Rin_1 and Rout_1 on upstream
drift tube

Flat_2 = Distance between tangencies of Rin_2 and Rout_2 on downstream
drift tube

Rin_1 = Drift tube inside bore radius on upstream drift tube

Rin_2 = Drift tube inside bore radius on downstream drift tube

Rout_1 = Radius between flat and face angle on upstream drift tube

Rout_2 = Radius between flat and face angle on downstream drift tube

DT_Len = Drift tube body length

Rb_1 = Inside bore tube radius of upstream drift tube

Rb_2 = Inside bore tube radius of downstream drift tube

Rc_1 = Outside corner radius of upstream drift tube

Rc_2 = Outside corner radius of downstream drift tube

Diam = Outside diameter of drift tube

GapLen = Gap length, distance between drift tube noses

GL = Focusing gradient (tesla)

![](media/image7.jpeg){width="6.024305555555555in"
height="3.821527777777778in"}

**Figure A-1 Drift tube cell geometry**

# Appendix B

## DTL Magnet, Post coupler, and Diagnostics schematic Layout

Table of symbols