1. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 1 Commissioning and Initial Operating Experience with the SNS Accelerator Complex

2. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 2  Beam and Neutronics Project Completion goals were met  10 13 protons delivered to the target  The SNS Construction Project was formally Completed in June 2006  We have officially started SNS Operations First Beam on Target, First Neutrons and Technical Project Completion Goals Met April 28, 2006

3. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 3 SNS Accelerator Complex 945 ns 1 ms macropulse Current mini-pulse Current 1ms Front-End: Produce a 1-msec long, chopped, H- beam 1 GeV LINAC Accumulator Ring: Compress 1 msec long pulse to 700 nsec Chopper system makes gaps Ion Source 2.5 MeV1000 MeV87 MeV CCL SRF,  = 0.61 SRF,  =0.81 186 MeV387 MeV DTL RFQ Accumulator Ring RTBT Target HEBT InjectionExtraction RF Collimators Liquid Hg Target

4. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 4 SNS High-Level Design Parameters Ring is designed for 2 MW at 1 GeV; installed for 1.3 GeV (mostly)

5. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 5 The SNS Partnership ORNL Accelerator Systems Division responsible for integration, installation, commissioning and operation

6. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 6 Spring 1999

7. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 7 Now

8. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 8 Front-End Systems  Front-End H - Injector was designed and built by LBNL  402.5 MHz Radiofrequency quadrupole accelerates beam to 2.5 MeV  Medium Energy Beam Transport matches beam to DTL1 input parameters  Front-end delivers 38 mA peak current, chopped 1 msec beam pulse  H - Ion Source has been tested at baseline SNS parameters in several endurance runs  >40 mA, 1.2 msec, 60 Hz

9. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 9 Accumulator Ring and Transport Lines Circum 248 m Energy 1 GeV f rev 1 MHz Q x, Q y 6.23, 6.20  x,  y -7.9, -6.9 Accum turns1060 Final Intensity1.5x10 14 Peak Current52 A RF Volts (h=1) 40 kV (h=2) 20 kV Injected  p/p  0.27% Extracted  p/p  0.67% HEBT Accumulator Ring RTBT Injection Collimation RF Extraction Target  Designed and built by Brookhaven National Lab

10. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 10 Ring and Transport Lines HEBT Arc Injection Ring Arc RTBT/Target

11. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 11 Target Region Within Core Vessel Core Vessel water cooled shielding Core Vessel Multi-channel flange Outer Reflector Plug Target Target Module with jumpers Moderators Proton Beam

12. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 12 Normal Conducting Linac: Front-End Output Emittance and Bunch Length  MEBT inline emittance system allows routine measurement  Expect 0.3  mm mrad, rms, norm  Results (  mm mrad, rms, norm)  X = 0.29  Y = 0.26  Bunch length measured with mode-locked laser system RMS Bunch Length (deg) Rebuncher phase (deg)

13. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 13 DTL and CCL RF Setpoints by Phase Scan Signature Matching CCL Module 2 RF Phase BPM Phase Diff (deg) J. Galambos, A. Shishlo  To tune up the linac requires finding phase and amplitude setpoints for 95 RF systems within 1%/1 deg (specification)  Model-based methods utilizing time-of-flight data have been developed  Normal conducting linac phase and amplitude setpoints determined by Phase- Scan Signature Matching  Plot shows data (lines) compared to model (pts) for two CCL2 amplitudes

14. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 14 CCL Module 1 Longitudinal Bunch Shape Monitor Measurements  Measured values are close to the predicted bunch length  Measurements were motivated by earlier observations of a longer bunch, presumably due to longitudinal mismatch BSM107 BSM111

15. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 15 Superconducting Linac Tuneup by Phase Scan  Fit varies input energy, cavity voltage and phase offset in the simulation to match measured BPM phase differences  Relies on absolute BPM phase calibration  With a short, low intensity beam, results are insensitive to detuning cavities intermediate to measurement BPMs SCL phase scan for first cavity Solid = measured BPM phase diff Dot = simulated BPM phase diff Red = cosine fit Cavity phase BPM phase diff 

16. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 16 Low-level RF Feedforward  Beam turn-on transient gives RF phase and amplitude variation during the pulse, beyond bandwidth of feedback  LLRF Feedforward algorithms have been commissioned (Champion, Kasemir, Ma, Crofford) Without Feed-forward With Feed-forward

17. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 17 SCL Operations: Fault Recovery (Galambos)  We have successfully tested a cavity fault recovery algorithm in which the phase of all downsteam cavities are adjusted in response to a change in setpoint of a given cavity Cavity 3a turned off Final cavity phase found within 1 degree, output energy within 1 MeV Turned on cavity 4a, reduced fields in 11 downstream cavities

18. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 18 Ring/RTBT/Target Commissioning Timeline January-May 2006 Jan. 12:Received approval for beam to Extraction Dump. Jan. 13:First beam to Injection Dump. Jan. 14:First beam around ring. Jan. 15:>1000 turns circulating in ring Jan. 16:First beam to Extraction Dump. Jan. 26:Reached 1.26E13 ppp to Extraction Dump. Feb. 11:~8 uC bunched beam (5x10 13 ppp) Feb. 12:~16 uC coasting beam (1x10 14 ppp) Feb. 13:End of Ring commissioning run April 3-7: Readiness Review for RTBT/Target April 27: Received approval for Beam on Target April 28: First beam on target and CD4 beam demonstration

19. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 19 Accumulation and Extraction of 1.3x10 13 protons/pulse (January 26, 2006) Ring Beam Current Monitor 200 turn accumulation extraction Extraction Dump Current Monitor

20. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 20 Ring Orbit Correction: H,V Bumps are Due to Injection Kickers Horizontal Orbit BPM Amplitude Vertical Orbit

21. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 21 Ring Optics Measurements: Betatron Phase Advance and Chromaticity VertHoriz Natural Chromaticity (Design) -6.9-7.9 Natural Chromaticity (Measured) -7.2-8.2 Corrected Chromaticity (Meas) 0.00.1 Plots show measured betatron phase error vs. model-based fit Data indicates that the linear lattice is already very close to design

22. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 22 High Intensity Studies (Danilov, Cousineau, Plum)  Beam intensity records (protons/pulse):  5x10 13 in bunched beam, transported to target  1x10 14 unbunched, coasting beam  We searched for instabilities by i) delaying extraction, ii) operating with zero chromaticity, iii) storing a coasting beam  No instabilities seen thus far in “normal” conditions  See instability centered at 6 MHz, growth rate 860 us for 10 14 protons in the ring, driven, as predicted by extraction kicker impedance  Z calc  22-30 kOhm/m  Z meas  28 kOhm/m.  In coasting beam also see very fast instability at 0.2-1x10 14 protons in the ring, consistent with e-p. Growth rate 20-200 turns. f  30-80 MHz depending on beam conditions.  Scaling these observations to nominal operating conditions predicts threshold > 2 MW for extraction kicker (as previously predicted) Slow: Extraction Kicker Fast: electron-proton

23. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 23 Phase Space Painting Stripping Foil Injected Beam Initial Closed Orbit Final Closed Orbit X pxpx Wei et. al., PAC 2001, 2560 X-Y space after 1060 Turns

24. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 24 Phase Space Painting 65 mm 80 mm Beam on Target View Screen Beam profiles in RTBT

25. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 25 Summary of Achieved Beam Parameters ParameterBaseline/ Design Achieved in Commissioning/AP Achieved in Operation Units Linac Transverse Output Emittance 0.40.3 (H), 0.3 (V)0.4  mm-mrad (rms,norm) CCL1 bunch length344degrees rms Linac Peak Current38> 3820mA Linac Output Energy10001012890MeV Linac Average Current1.61.05 (DTL1 run) 0.003 (SCL run) 0.067mA Linac H-/pulse1.6x10 14 1.3x10 14 (DTL1) 8.0x10 13 (SCL run) 1.0x10 14 (Ring run) 4.3x10 13 Ions/pulse Linac Pulse length/Rep- rate/Duty Factor 1.0/60/6.01.0/60/3.8 (DTL1 run) 0.85/0.2/0.017 (SCL) 0.6/5/0.3msec/Hz/% Extracted protons/pulse1.5x10 14 0.96x10 14 0.43x10 14 Protons/pulse Beam Power1440460kW

26. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 26 Beam-Power-on-Target History Beam Power [0-65 kW] Beam power administratively limited to 10 kW until November 8 Feb 1, 2007 May 1, 2006

27. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 27 FY 2007 Integrated Beam Power by Day and Cumulative  6.3 MW-hrs delivered in Run 2007-1

28. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 28 Technical Challenges: Equipment Reliability  Beam Chopper Systems  Repeated failures in Low-energy and Medium-energy Beam Transport chopper systems  New, more robust, designs will be designed and manufactured this year (FY07 Accelerator Improvement Project)  High-Voltage Converter Modulators  A number of weak components limit MTBF to  2700 Hrs  Several prototype improvements are in test in single operational units  Improvements will be deployed this year on full system of 14 modulators (FY07 Accelerator Improvement Project)  Ion Source and Low Energy Beam Transport System  Water Systems  Problems associated with clogging flow restrictors, failed gaskets, poor conductivity monitoring and control, etc.  Reliability improvements have been underway since CD-4 (also FY07 AIP)  Cryogenic Moderator System  Thermal capacity degraded in 3 week cycle prior to December 2006  Manufacturer attempted repair in December  Capacity improved, but some sign of degradation remains  Mercury Pump  Seal failed end of November  Operating the pump now with failed seal, mitigated by installation of a cover plate to direct gas to the Mercury Off-Gas Treatment System  Replacement Mercury Pump in expected to be available for installation in September

29. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 29 Technical Challenges: Beam Power  Beam losses must be kept below 1 Watt/m to limit residual activation  We measure higher than desired losses in the Ring Injection area  We are unable to simultaneously transport waste beams (from stripping process) to the injection dump and properly accumulate in the ring  Internal Review of Injection Dump performance was held in November and follow-up meeting in December  Short-term fixes allow >100 kW operation; mid-term fixes (April 2007) are in preparation; long-term fix requires redesign of injection dump beamline and 2 new magnets  An aggressive accelerator physics program has reduced losses and activation while allowing increased beam power  We are not operating 9 Superconducting RF cavities (out of 81) out of concern for potential failures  Recent tests indicate that 6 of these 9 cavities are operable up to 15 Hz repetition rate  Those tests also show that the behaviour of individual cavities is the same at higher repetition rates, up to the full 60 Hz  We are building infrastructure to provide cryomodule repair and maintenance capabilities on-site. We are formulating plans to restore operation of all cavities, and to procure spare cryomodules

30. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 30 Outlook: Performance Goals FY08FY07 FY09  SNS Beam Power Upgrade Project will increase linac output energy to 1.3 GeV and provide 3 MW beam power

31. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 31 E-P Feedback Experiment at the PSR  We formed a collaboration to carry out an experimental test of active damping of the e-p instability at the LANL PSR (ORNL, LBNL, IU, LANL)  We deployed a broadband transverse feedback system designed and built by ORNL/SNS and demonstrated for the first time damping of an e-p instability in a long-bunch machine  We observed a 30% increase in e-p instability threshold with feedback on.

32. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 32  We have observed > 90% H- to proton stripping efficiency in proof-of-principle tests at SNS Laser Beam H-H- proton  H0H0 H 0* Step 1: Lorentz Stripping Step 2: Laser Excitation Step 3: Lorentz Stripping High-field Dipole Magnet H -  H 0 + e - H 0 (n=1) +   H 0* (n=3)H 0*  p + e - Laser-Stripping Injection Proof-of- Principle Experiment H- to protons

33. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 33 Yes, We’ve Had a Few Surprises  RFQ resonant frequency shifted by 100 kHz  Never found the cause; retuned in 2003  Bunch length 3x design in CCL1; also had difficulty keeping DTL5 at design field  Found a charred piece of paper in DTL Tank 5 in 2004  Large local losses and poor trajectory near SCL/HEBT transition  Found large dipole deflection with orbit response studies  Found current shunted around one quad coil  Beam is rotated about 6 degrees on target view screen  Excessive fundamental power through two SCL HOM feedthroughs; others impacted  Large local losses in injection dump line

34. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 34 Summary  Completed 7 beam commissioning runs, amounting to more than 1 year of dedicated beam commissioning and operating time  Achieved beam and neutron project completion requirements within project schedule  SNS construction project was formally completed in June 2006 on-budget and on-schedule  We are now in the early operations stage with local users  We are beginning to ramp up the beam power of the SNS accelerator complex

35. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 35 SNS Beam Diagnostic Systems RING 44 Position 2 Ionization Profile 70 Loss 1 Current 5 Electron Det. 12 FBLM 2 Wire 1 Beam in Gap 2 Video 1 Tune RING 44 Position 2 Ionization Profile 70 Loss 1 Current 5 Electron Det. 12 FBLM 2 Wire 1 Beam in Gap 2 Video 1 Tune SCL 32 Position 86 Loss 9 Laser Wire 24 PMT Neutron SCL 32 Position 86 Loss 9 Laser Wire 24 PMT Neutron RTBT 17 Position 36 Loss 4 Current 5 Wire 1 Harp 3 FBLM RTBT 17 Position 36 Loss 4 Current 5 Wire 1 Harp 3 FBLM HEBT 29 Position 1 Prototype Wire-S 46 BLM, 3 FBLM 4 Current HEBT 29 Position 1 Prototype Wire-S 46 BLM, 3 FBLM 4 Current IDump 1 Position 1 Wire 1 Current 6 BLM IDump 1 Position 1 Wire 1 Current 6 BLM EDump 1 Current 4 Loss 1 Wire EDump 1 Current 4 Loss 1 Wire LDump 6 Loss 6 Position 1 Wire,1 BCM LDump 6 Loss 6 Position 1 Wire,1 BCM CCL/SCL Transition 2 Position 1 Wire 1 Loss 1 Current CCL/SCL Transition 2 Position 1 Wire 1 Loss 1 Current CCL 10 Position 9 Wire 8 Neutron, 3BSM, 2 Thermal 28 Loss 3 Bunch 1 Faraday Cup 1 Current CCL 10 Position 9 Wire 8 Neutron, 3BSM, 2 Thermal 28 Loss 3 Bunch 1 Faraday Cup 1 Current Operational MEBT 6 Position 2 Current 5 Wires 2 Thermal Neutron 3 PMT Neutron 1 fast faraday cup 1 faraday/beam stop D-box video D-box emittance D-box beam stop D-box aperture Differential BCM MEBT 6 Position 2 Current 5 Wires 2 Thermal Neutron 3 PMT Neutron 1 fast faraday cup 1 faraday/beam stop D-box video D-box emittance D-box beam stop D-box aperture Differential BCM DTL 10 Position 5 Wire 12 Loss 5 Faraday Cup 6 Current 6 Thermal and 12 PMT Neutron DTL 10 Position 5 Wire 12 Loss 5 Faraday Cup 6 Current 6 Thermal and 12 PMT Neutron Not Operating

36. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 36 Baseline SNS Ion Source Performance LBNL H - ion source + ORNL antennas Source performed well during SNS commissioning. Successful commissioning would not be possible without use of longer- lived antennas. 10-40 mA routinely delivered at ~0.1% duty-factor. Availability improved: 86%  ~100% during later commissioning periods (target comm: 77 days). Largest availability gain  redesigning LEBT insulators Antennas: Welton et al, RSI 73 (2002) 1008 + Beam attenuation ~5 mA/day Run #9 ran for 16 days / 33 mA / 0.4 mA/day. 3 Typical Test Runs Our Best Run (employs new operating procedure) Catastrophic antenna failure ~10 lifetime tests performed at full 7% duty-factor and max current. Best results shown Outcome: Insufficient beam current, frequent antenna failures and poor beam stability with time Vigorous R&D program to meet SNS operational requirement of 40 mA and SNS-PUP requirement of 60 mA.

37. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 37 Recent Ion Source R&D Accomplishments Ionization Cone Cs injection collar Air duct Cs Line Extractor electrode ions Elemental Cs system  65 mA-1.2 ms, 70 mA-0.2 ms pulses achieved at 10Hz!  ~2x increase in RF power efficiency.  Multi-day runs show excellent beam stability.  Multiple cesiations show excellent reproducibility.  ~5% droop and good ~30 us rise times.  Beam emittance is expected to be similar to baseline source. Al 2 O 3 insulator Anode Cooling channel Plasma stream Cathode Ions  Multi-year lifetime achieved at DESY at <1% duty-factor  Plasma gun enhances H - ~50%  51 mA – 0.2 ms pulses achieved with no Cs and no B-field confinement.  65 mA – 0.2 ms, 50 mA – 1.2 ms pulses achieved with Cs and no confinement. Welton et al, LINAC 2006, Knoxville External Antenna & Plasma Gun Welton et al, LINAC 2006, Knoxville

38. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 38 Energy Stability – Pulse to Pulse (J. Galambos)  RMS energy difference jitter is 0.35 MeV, extreme = + 1.3 MeV  Parameter list requirement is max jitter < +1.5 MeV 865 MeV beam ~ 1000 pulses 20  sec pulse 12 mA beam

39. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 39 SCL Laser Profile Measurements  SCL laser profiles (H + V) were available at 7 locations  3 at medium beta entrance, 3 at high beta entrance and 1 at the high beta end Measured horizontal profile after SCL cryomodule 4

40. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 40 Neutrons: 4-methyl pyridine N-oxide 5 kWatt, 3 hour, ¼ detector, T = 3 K 4  eV

41. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 41 The Spallation Neutron Source  The SNS is a short-pulse neutron source, driven by a 1.4 MW proton accelerator  SNS will be the world’s leading facility for neutron scattering research with peak neutron flux ~20–100x ILL, Grenoble  SNS construction project, a collaboration of six US DOE labs, was funded through DOE-BES at a cost of 1.4 B$  SNS will have 8x beam power of ISIS, the world’s leading pulsed source  Stepping stone to other high power facilities