SNS Power Upgrade Project: Advancing the Success of the SNS Accelerator

1. The SNS Power Upgrade Project Building on the Success of the SNS Accelerator Deployment Kevin Jones Research Accelerator Division Director

2. A Brief History of the SNS Power Upgrade Project (PUP) • SNS was designed from the outset to accommodate two major upgrades • Doubling the SNS proton beam power • Adding a Second Target Station (STS) • The PUP received CD-0 (approval of mission need) in November 2004 • Increase power by about a factor of 2 (1.3 x energy increase + 1.5 x current increase) • 6 year project – CD-4 in FY 2011 • In 2008, the beam current increase and necessary target improvements were moved to R&D and Accelerator Improvement Projects (AIPs) • The PUP received CD-1 (approval of conceptual design) in January 2009 • Increase beam energy to 1.3 GeV • No beam current increase • CD-4 now projected in FY 2015

3. The Power Upgrade Project is interwoven in the SNS Upgrade Path FY PUP is only an energy upgrade: The PEP completion milestone is demonstration of 1.3 GeV beam energy

4. The PUP has primary impact on four areas at SNS Accelerator: fill in empty drift sections with high-beta cryomodules Collimators Injection Upgrade Injection Magnets Front-End LINAC Extraction: fill in empty space with kickers Klystron gallery: fill in area provided with high power RF equipment for new cryomodules

5. The PUP design is based on experience • SNS has been operating at high power for almost two years • Incorporated lessons learned into CD-2 (preliminary design) basis • No R&D needed for the energy upgrade (PUP) MW Operation PUP CD-1 1000 PUP CD-0 Beam Power (kW) Nov. 2004 Nov. 2006 Jan. 2009

6. 8 new high-beta cryomodules are required for 1.3 GeV • SCL requirements: 8 cryomodules to reach 1.3 GeV • There are 9 empty slots available, one for spare • Long term SNS power upgrade impacts included 7 cryomodules sets an aggressive required gradient 8 cryomodules: conservative required gradient 6 cryomodules: very aggressive required gradient

7. The new cryomodules will reflect lessons learned from performance of existing units • The main limiting factor of performance • Electron loading (mainly from field emission + multipacting at the end group/Higher Order Mode (HOM) coupler) • Consequences • One bad cavity in a cryomodule can affect other cavities (collective behavior) • Heating mostly partial quench at the end group • Damage weak component (HOM coupler) especially during initial commissioning and conditioning

8. These lessons learned stimulated some design changes • End group material changed to high RRR (high purity) niobium • Higher thermal conductivity  higher thermal stability • Expect better surface condition after BCP • Add cooling block at the cavity string ends • Existing cavities: Inadequate cooling 8-10K at the flange • Fundamental power coupler • Accommodate the current upgrade • 700 kW peak, 70 kW average (cf. 550kW peak, 50 kW average) • Inner conductor made thicker (lower the inner conductor tip temperature by increasing thermal conduction) • Cost considerations • Vendor procurement cost is unaffected by design change • Potential savings in reducing cavity processing iterations

9. Design development uses all available operating experience • RF system designs incorporate MW operational experience lessons learned • e.g., use reworked HVCM design with 9 klystrons / modulator • Ring Injection upgrade design utilizes tools calibrated with existing operational experience • Developed to remediate issues with the original design Ring Injection Area Upgrades already done

10. Several modest but important issues must be addressed in the injection region • The original design of the ring injection area suffered due to lack of 3-D magnet modeling and particle tracking • The importance of reflected convoy electrons and cathode-spot in-vacuum breakdown (arcing) was not fully appreciated • To address the issues we’ve had in the ring injection area we’ve developed and benchmarked our model of the ring injection, including the 3-D magnet modeling and particle tracking • In addition to incorporating lessons learned, we will use these tools to check that our design is good prior to fabricating the magnets and other beam line components

11. Design development uses all available operating experience • Utility systems tested using the equipment where possible • Tower water system tested in spring/summer 2010 • Ring magnet systems run at 1.3 GeV settings in summer 2010 for electrical and ring cooling tests • Future tests planned • Cooling system that services the additional couplers for PUP to ascertain system capability • Radiation dose measurements in the Ring Injection area to determine whether a Rad-hard design is necessary

12. The PUP is inherently low risk in most technical areas Primary technical components are not fundamentally new • PUP SCL cryomodules are similar to existing cryo-modules • Required accelerating gradients are low • Simplify the design based on lessons learned (no Higher Order Mode couplers, etc.) We are building a spare cryo-module now:

13. The PUP is inherently low risk in most technical areas Primary technical components are not fundamentally new • Most of the Ring and transport lines are designed for 1.3 GeV • Injection chicane does require upgrade • Good understanding of the beam requirements, based on previous improvements • Installation activities will have to be integrated with operations • Cryomodules have been removed and installed during maintenance outages • PUP personnel were involved in the original construction and operations Cryo-module removed from tunnel under repair in the clean room

14. The RF systems replicate installed equipment • 6 HPRF Transmitters: • 6 Transmitter Racks • 36 Klystrons • 12 HV Tanks • 6 TRCCs • 36 Circulators • 36 Water Loads • 144 Directional Couplers • 36 Waveguide Runs • 18 Chase Inserts • 36 LLRF Systems: • 36 FCMs • 36 HPMs • Timing • Arc Detection • Reference Line • 4 HVCMs: • 4 Transformers • 4 SCR Cabinets • 4 Control Racks • 4 HVCM Interfaces are defined

15. The RF systems replicate installed equipment

16. Installation of PUP components must be integrated into the facility operating schedule • We will install cryomodules during maintenance outages • Have run with different numbers of installed cryomodules • Commission individually as installed during post-outage beam study time • We plan a two stage Accelerator Readiness Review (ARR): • An initial ARR for use of single new cryo-module at a time • Use a “Radiation Hold” lockout to prevent its use after initial commissioning • A final ARR after the Ring Injection upgrade for 1.3 GeV beam operation • Have experience operating with different beam energies and tools to facilitate this • Startup plan is drafted

17. Summary • The PUP technical risk is low • Our present operational performance informs the technical scope of work • We understand what is required to reach 1.3 GeV and how to implement it • Total project cost is ~$120M • An experienced team is in place • We are ready to build on the success of the SNS accelerator • Unfortunately, DOE informed us last week that this project will be cancelled and rolled into the Second Target Station project that will move forward with CD-1 in 2014 at the earliest