alexander aleksandrov oak ridge national laboratory oak ridge, usa

Spallation Neutron Source Project: Commissioning Results, First

Operation Experience, and Upgrade Plans

Alexander Aleksandrov

Oak Ridge National LaboratoryOak Ridge, USA

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

Nanoscale sc ience and technology presents extraordinary opportunities

DNA

Microelectromechanical Devices

Fly ash

Atoms of silicon

Head of a pin

Quantum corral of 48 iron atoms

Human hair

Red blood cells

Ant

Mic

row

orl

d

0.1 nm

1 nanometer (nm)

0.01 m10 nm

0.1 m100 nm

0.01 mm10 m

0.1 mm100 m

1 cm10-2 m

10-3 m

10-4 m

10-5 m

10-6 m

10-7 m

10-8 m

10-9 m

10-10 m

Visiblespectrum

Na

no

wo

rld

103 nanometers

106 nanometers

Dust mite

ATP synthase

Nanotube electrode Nanotube transistor

1 angstrom

Neu

tro

n s

catt

erin

g

Neutrons probe a broad range of length scales


FissionFission chain reaction continuous flow 1 neutron/fission

SpallationSpallationno chain

reactionpulsed operation 30

neutrons/proton Time resolved exp.

Spallation-Evaporation Production of Neutrons


• 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

The Spallation Neutron Source


The Spallation Neutron Source Partnership

~177 M$ ~60 M$

~113 M$~20 M$

Description AcceleratorProject Support 75.6Front End Systems 20.8 20.8Linac Systems 315.9 315.9Ring & Transfer Systems 142.0 142.0Target Systems 108.2Instrument Systems 63.3Conventional Facilities 378.9Integrated Control Systems 59.7 59.7BAC 1,164.4Contingency 28.3

TEC 1,192.7R&D 100.0 80.0

Pre-Operations 119.0 95.2

TPC 1,411.7 713.6

~63 M$

~106 M$

SNS-ORNL Accelerator systems: ~167 M$

At peak : ~500 People worked on the constructionof the SNS accelerator Oak Ridge, TN

35° 49' N , 83° 59' W


Spring 1999


Spring 2000


Spring 2001


Spring 2002


Spring 2003


Spring 2006


SNS Accelerator Complex

945 ns

1 ms macropulse

Cur

rent

mini-pulse

H- stripped to protons

Cur

rent

1ms

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

Deliver beam to Target

Chopper system makes

gaps

Ion Source2.5 MeV 1000

MeV86.8 MeV

CCL SRF, =0.61SRF, =0.81

186 MeV 387 MeV

DTLRFQ


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

1 mm

Pits on inner surface in this geometry

17 Instruments Now Formally Approved

•Fundamental Physics to Engineering

•Chemistry to “Genomes to Life”


The SNS Main Parameters

1.1071.0981.058Ring rf frequency [MHz]

0.20.150.15Ring space-charge tune spread, Qsc

683691695Pulse length on target [ns]

707068Chopper beam-on duty factor [%]

6.06.06.0Linac beam macro pulse duty factor [%]

654226Average macropulse H- current [mA]

925938Peak Current from front end system

3.92.51.6Linac average beam current [mA]

5.03.01.4Beam power on target, Pmax [MW]

12 + 8 (+1 reserve)12 + 8 (+1 reserve)12SRF cryo-module number (high-beta)

1.6

1.0 / 1060

35 (+2.5/-7.5)

27.5 (+/- 2.5)

33+48

11

1000

Baseline

2.5

1.0 / 1100

31

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1300

Upgrade

3.8

1.0 / 1110

34

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1400

Ultimate

Ring bunch intensity [1014]

Ring injection time [ms] / turns

Kinetic energy, Ek [MeV]

Peak gradient, Ep (=0.81 cavity) [MV/m]


Number of SRF cavities

SRF cryo-module number (med-beta)











1.6

1.0 / 1060

35 (+2.5/-7.5)

27.5 (+/- 2.5)

33+48

11

1000

Baseline

2.5

1.0 / 1100

31

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1300

Upgrade

3.8

1.0 / 1110

34

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1400

Ultimate









• 65 kV, 45 mA H- ion source

• Electrostatic LEBT with pre-chopper

• 2.5 MeV 402.5 MHZ RFQ

• 3.6 m long MEBT with chopper and beam diagnostics

Front End (injector)


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)


Drift Tube Linac in the tunnel


805 MHz Coupled-Cavity Linac (side coupled)

• CCL accelerates beam to 187 MeV

• System consists of 48 accelerating segments, 48 quadrupoles, 32 steering magnets and diagnostics (55 m total length)

Bridge Coupler 44 final machining


Coupled-Cavity Linac in the tunnel


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


Superconducting Cavity Performance

Nr

of

Cav

itie

sN

r o

f C

avit

ies

High Beta

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28E0 (MV/m)

Freq

uen

cyMedium Beta

01234567

0 2 4 6 8 10 12 14 16 18 20 22 24

E0 (MV/m)

Fre

qu

en

cy


Super Conducting Linac in the Tunnel


High-Power RF Systems

• Compact High Voltage Converter Modulators using solid state devices (IGBT)

• High-Power RF System: klystrons, waveguides, circulators

– 7 402.5 MHz 2.5 MW klystrons

– 4 CCL 5 MW Klystrons

– 81 SCL 550 kW klystrons


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)

Digital Low Level RF system


SNS Central Helium Liquefying Facility

• Cold box specifications are:

• 8300 Watts on the shield

• 2400 Watts @ 2.1Kelvin

• 15g/s Liquefaction


Circumference 248 m

Energy 1 GeV

Revolution period 1 μs

Number of turns 1060

Final Intensity 1.5x1014

Peak Current 52 A

Number of magnets >300

(bend and focusing)

The SNS Accumulator Ring


Ring Installation Progress


SNS Liquid Mercury Target


SNS Remote Handling Manipulators


Commissioning Timeline

2002 2003 2004 2005 2006

DTL Tanks 1-3

Front-End

DTL Tank 1

DTL/CCL

SCL

Ring

Target


5x1013/pulse Protons Delivered to the Target

Final RTBT Beam Current Monitor

Ring Beam Current Monitor

Beam on Target View Screen


1st “Production Run”


Transition to Operation

0

500

1000

1500

2000

2500

0 12 24 36Months

Bea

m P

ower

(kW

), P

rodu

ctio

n H

rs

50

55

60

65

70

75

80

85

90

95

Rel

iabi

lity

Beam Power GoalNeutron Production HoursReliability

0

500

1000

1500

2000

2500

0 12 24 36Months

Bea

m P

ower

(kW

), P

rodu

ctio

n H

rs

50

55

60

65

70

75

80

85

90

95

Rel

iabi

lity

Beam Power GoalNeutron Production HoursReliability

FY08FY07 FY09


The SNS Power Upgrade Main Parameters











1.6

1.0 / 1060

35 (+2.5/-7.5)

27.5 (+/- 2.5)

33+48

11

1000

Baseline

2.5

1.0 / 1100

31

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1300

Upgrade

3.8

1.0 / 1110

34

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1400

Ultimate


















1.6

1.0 / 1060

35 (+2.5/-7.5)

27.5 (+/- 2.5)

33+48

11

1000

Baseline

2.5

1.0 / 1100

31

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1300

Upgrade

3.8

1.0 / 1110

34

27.5 (+/- 2.5)

33+80 (+4 reserve)

11

1400

Ultimate








alexander aleksandrov oak ridge national laboratory oak ridge, usa

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