1. Alexander Aleksandrov Oak Ridge National Laboratory
Spallation Neutron Source Project: Commissioning Results, First Operation Experience, and Upgrade Plans
Alexander Aleksandrov
Oak Ridge National Laboratory
Oak Ridge, USA

2. Neutrons probe a broad range of length scales
Neutron scattering
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

3. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spallation-Evaporation Production of Neutrons
Fission
chain reaction
continuous flow
1 neutron/fission
Spallation
no chain reaction
pulsed operation
30 neutrons/proton
Time resolved exp.
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

4. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
The Spallation Neutron Source
The SNS began operation in 2006
At 1.4 MW it will be ~7x ISIS, the world’s leading pulsed spallation source
The peak neutron flux will be ~20-100x ILL
SNS will be the world’s leading facility for neutron scattering
It will be a short drive from HFIR, a reactor source with a flux comparable to the ILL
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

5. The Spallation Neutron Source Partnership
SNS-ORNL Accelerator systems: ~167 M$
~20 M$
~113 M$
~106 M$
~177 M$
~60 M$
At peak : ~500 People
worked on the construction
of the SNS accelerator
~63 M$
Oak Ridge, TN
35° 49' N , 83° 59' W
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

6. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spring 1999
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

7. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spring 2000
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

8. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spring 2001
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

9. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spring 2002
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

10. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spring 2003
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

11. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Spring 2006
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

12. SNS Accelerator Complex
Front-End: Produce a 1-msec long, chopped, low-energy H- beam
LINAC: Accelerate the beam to 1 GeV
Accumulator Ring: Compress 1 msec long pulse to 700 nsec
H- stripped to protons
Deliver beam to Target
2.5 MeV
86.8 MeV
186 MeV
387 MeV
1000 MeV
Ion Source
RFQ
DTL
CCL
SRF, b=0.61
SRF, b=0.81
Chopper system makes gaps
945 ns
Current
1ms
mini-pulse
Current
1 ms macropulse
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

13. The SNS Target: 2-MW Design
Cavitation-induced pitting is an issue.
Options for mitigation:
Materials, Geometry
25 kJ/pulse at 7x15cm beam size sets of transverse and longitudinal shock wave.
Needs to be exchanged every 3 month
Pits on inner surface in this geometry
1 mm
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

14. 17 Instruments Now Formally Approved
Fundamental Physics to Engineering
Chemistry to “Genomes to Life”

15. The SNS Main Parameters
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

16. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Front End (injector)
65 kV, 45 mA H- ion source
Electrostatic LEBT with pre-chopper
2.5 MeV MHZ RFQ
3.6 m long MEBT with chopper and beam diagnostics
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

17. 402.5 MHz Drift Tube Linac (DTL)
DTL accelerates beam to 87 MeV
System includes 210 drift tubes in six separate tanks (37m total length)
Inside drift tubes: permanent magnet quadrupoles, electromagnetic dipole correctors, strip-line beam position monitors (BPM)
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

18. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Drift Tube Linac in the tunnel
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

19. 805 MHz Coupled-Cavity Linac (side coupled)
Bridge Coupler 44 final machining
CCL accelerates beam to 187 MeV
System consists of 48 accelerating segments, 48 quadrupoles, 32 steering magnets and diagnostics (55 m total length)
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

20. Coupled-Cavity Linac in the tunnel
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

21. 805MHz Super Conducting RF Linac (SCL)
SCL accelerates beam from 187 to 1000 MeV
81 6-cell superconducting cavities in 23 cryo-modules (157m)
Cavities are operated at 2.1K or 4.2K
Two cavities geometries are used to cover broad range in particle velocities
Cavities are assembled into strings
Medium beta cavity
High beta cavity
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

22. Superconducting Cavity Performance
Nr of Cavities
Nr of Cavities
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

23. Super Conducting Linac in the Tunnel
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

24. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
High-Power RF Systems
Compact High Voltage Converter Modulators using solid state devices (IGBT)
High-Power RF System: klystrons, waveguides, circulators
MHz 2.5 MW klystrons
4 CCL 5 MW Klystrons
81 SCL 550 kW klystrons
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

25. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
Digital Low Level RF system
Cavity field and phase droop with feedback alone (left) and feedback + feedforward (right) beam loading compensation.
Phase width of the bunch along the pulse with feedback alone (left) and feedback + feedforward (right)
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

26. SNS Central Helium Liquefying Facility
Cold box specifications are:
8300 Watts on the shield
Kelvin
15g/s Liquefaction
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

27. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
The SNS Accumulator Ring
Circumference m
Energy GeV
Revolution period μs
Number of turns
Final Intensity x1014
Peak Current A
Number of magnets >300
(bend and focusing)
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

28. Ring Installation Progress
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

29. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
SNS Liquid Mercury Target
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

30. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
SNS Remote Handling Manipulators
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

31. Commissioning Timeline
2002
2003
2004
2005
2006
Front-End
DTL/CCL
SCL
DTL Tank 1
DTL Tanks 1-3
Ring
Target
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

32. 5x1013/pulse Protons Delivered to the Target
Ring Beam Current Monitor
Beam on Target View Screen
Final RTBT Beam Current Monitor
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

33. A. Aleksandrov RuPAC 2006 Sept. 10 – 14, 2006 Novosibirsk
1st “Production Run”
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

34. Transition to Operation
FY07
FY08
FY09
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk

35. The SNS Power Upgrade Main Parameters
A. Aleksandrov RuPAC Sept. 10 – 14, Novosibirsk