Reactor & Spallation Neutron Sources

Ken Andersen Oxford School of Neutron Scattering ESS Neutron Instruments Division Oxford, 2013-09-04 Overview

• Neutron Facilities – overview & trends • Reactor-based sources – Institut Laue-Langevin • Fission vs Spallation – principles & limitations • Components of a pulsed spallation neutron source – accelerator – target – moderators • Neutron source time structure – the time-of-flight method • Long-pulse neutron sources

JEEP- II

ISIS TUD HZB FRM2 LLB BNC ILL PSI

page Major neutron sources in the world

2000 2010 2020 ILL (F) HZB (D) Continuous PSI (CH) FRM-II (D) HFIR (USA) NIST (USA)

JRR-3 (J) PIK (RU) IBR-2/2M (RU)

ISIS-1 (UK) Pulsed ISIS-2 (UK) SNS (USA)

J-PARC (J) ESS (SE) Major neutron sources in the world

Fission/Spallation Continuous/Pulsed ILL (F) X X HZB (D) X X PSI (CH) X X FRM-II (D) X X HFIR (USA) X X NIST (USA) X X JRR-3 (J) X X PIK (RU) X X IBR-2/2M (RU) X X ISIS-1 (UK) X X ISIS-2 (UK) X X SNS (USA) X X J-PARC (J) X X ESS (SE) X X Neutron Sources

• About 10 major neutron facilities worldwide • Fission (continuous) • Spallation (pulsed) • User facilities • Number 1 is Institut Laue-Langevin (ILL) in Grenoble, France • 40 instruments ILL • 700 experiments a year • Mainly condensed-matter physics, ISIS chemistry and soft matter

page ILL Reactor Neutron Source • Highly-enriched uranium • Compact design for high brightness • Heavy-water cooling • Single control rod • 57MW thermal power

2.5 m

page ILL Reactor Neutron Source

cold thermal hot

moderator liquid D2 Liquid graphite D2O moderator 20K 300K 2000K temperature neutron 3→20Å 1→3Å 0.3→1Å wavelength sample 1Å→100 0.3→5Å 0.1→2Å lengthscale nm sample 1kHz→1 0.1→10 1→100 timescale THz THz THz

page ILL Reactor Neutron Source

2nd guide hall (6 instruments)

1st guide hall (20 instruments)

page ILL Reactor Neutron Source

HCS VC S

beam tubes beam Thermal Thermal

page ILL Moderator Brightnesses Evolution of neutron sources

1020

s SNS

- 2 HFIR ILL ISIS-TS1 J-PARC 15 MTR NRU ISIS-TS2 10 IPNS

n/cm NRX HFBR ZING-P FRM-II PIK WNR X-10 KENS SINQ ZINP-P 1010 CP-2

CP-1 Thermal flux Thermal flux 105 Berkeley 37-inch cyclotron 350 mCi Steady State Sources Ra-Be source Pulsed Sources 1 Chadwick 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020

(Updated from Neutron Scattering, K. Skold and D. L. Price, eds., Academic Press, 1986) Spallation vs Fission

Fission Spallation vs Fission

Fission

200 MeV/fission 2.35 – 1 = 1.35 neutrons freed => 150 MeV/neutron Spallation vs Fission

Fission

200 MeV/fission 2.35 – 1 = 1.35 neutrons freed => 150 MeV/neutron

Spallatio n: Spallation vs Fission

Fission

200 MeV/fission 2.35 – 1 = 1.35 neutrons freed => 150 MeV/neutron

Spallatio 1 GeV proton in: n: 250 MeV becomes mass (endothermic reaction) 30 neutrons freed => 25 MeV/neutron Spallation vs Fission

Fission

200 MeV/fission 2.35 – 1 = 1.35 neutrons freed => 150 MeV/neutron

Spallatio 1 GeV proton in: n: 250 MeV becomes mass (endothermic reaction) 30 neutrons freed => 25 MeV/neutron 6x more neutrons per unit heat Spallation Sources

• Proton beam parameters: energy (=voltage) and current • Current: neutron production is proportional to number of protons • Energy: neutron production is proportional to proton energy (E>500MeV)

G.J. Russell et al, AIP Conf. Proc. 346, 93 (n/p) PRODUCTION NEUTRON (1995)

• Neutron production is proportional to Power = Voltage x Current – e.g. ISIS: 800MeV x 200uA = 160kW – e.g. ESS: 2.5GeV x 2mA = 5MW

Spallation Sources

• Spallation: 10x higher neutron brightness per unit heat – about 6x more neutrons per unit heat ¶3N – about ½ production volume B =

ΔΩ ΔA ¶A¶t¶W

Spallation Sources

• Spallation: 10x higher neutron brightness per unit heat – about 6x more neutrons per unit heat ¶3N – about ½ production volume B =

ΔΩ ΔA ¶A¶t¶W

• 1MW spallation source = 10MW reactor – e.g. 800MeV at 1.25mA – e.g. 2.5GeV at 0.4mA • Pulsed nature gives additional information • Spallation has not yet reached the limit imposed by cooling power – Short-pulse limitations: peak power on target

1020

ESS

s SNS

- 2 HFIR ILL ISIS-TS1 J-PARC 15 MTR NRU ISIS-TS2 10 IPNS

n/cm NRX HFBR ZING-P FRM-II PIK WNR X-10 KENS SINQ ZINP-P 1010 CP-2

CP-1 Thermal flux Thermal flux 105 Berkeley 37-inch cyclotron 350 mCi Steady State Sources Ra-Be source Pulsed Sources 1 Chadwick 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020

(Updated from Neutron Scattering, K. Skold and D. L. Price, eds., Academic Press, 1986) Neutrons vs Light

light neutrons λ < μm < nm E > eV > meV n 1→4 0.9997→1.0001

θc 90° 1° 1018 p/cm2/ster/s 1014 n/cm2/ster/s Φ/ΔΩ (60W lightbulb) (60MW reactor) P left-right up-down spin 1 ½ interaction electromagnetic strong force, magnetic charge 0 0 Why neutrons?

• Thermal neutrons have wavelengths similar to atomic distances

• Thermal neutrons have energies comparable to lattice vibrations

• Neutrons are non-destructive

• Neutrons interact weakly: they penetrate into the bulk

• Neutrons interact via a simple point-like potential: amplitudes are straightforward to interpret

• Neutrons have a magnetic moment: great for magnetism

• Neutrons see a completely different contrast to x-rays e.g. hydrogen very visible Why neutrons?

100 keV ISIS, Oxfordshire, UK (160kW) ISIS, Oxfordshire, UK (160kW) ISIS: Today’s leading spallation neutron source 160kW SNS, Oak Ridge, USA: 1MW today J-PARC, Tokai, Japan: 1MW soon J-PARC, Tokai, Japan: 1MW soon Short-Pulse Spallation Sources

• Accelerator – H- ion source – Linear accelerator – Stripper converts H- to H+ – Synchrotron • Spallation target • Reflector • Moderators Linear accelerator: LINAC Linear accelerator: LINAC SNS ion source: H- Different types of Linac Drift-Tube Linac (DTL)

Radio-Frequency Quadrupole (RFQ) Elliptical cavities

“Low β” / “High β”

β=v/c Synchrotron

• Synchronise: • B-field: bend • E-field: accelerate ISIS • E & B field: focus • Magnets to each other • Injection • Stripper foil • Extraction • Kicker magnet Synchrotron

• Synchronise: • B-field: bend E-field: accelerate • B- • E & B field: focus field H+ stripper • Magnets to each other foil Injection • H- • Stripper foil • Extraction • Kicker magnet Synchrotron

• Δtlinac ≈ 1 ms

• Ering ≈ 1 GeV ISIS – v ≈ 3x108 m/s

• Lring ≈ 200 m

• Δtring ≈ 1 μs ISIS target 1: solid tungsten

SNS target: liquid mercury J-PARC target ISIS TS2 Target

decoupled poisoned

solid CH4

coupled H 2 Target: 66mm W coupled solid CH4 SNS target Target-Reflector-Moderator Neutronics

• Target produces neutrons in MeV range • Moderators contain H to thermalise neutrons • Largest scattering cross-section (80b) • Lowest mass: same as neutron • on average, ½ energy lost per collision • 100MeV -> 10meV requires about 25 collisions

• Moderators embedded in reflector, usually D2O-cooled Be • Minimal absorption • Large scattering cross-section (8b) • Little thermalisation

4 6 Target-Reflector-Moderator Neutronics

Target plane

B e Target protons in Target-Reflector-Moderator Neutronics

10cm above/below Target B e protons in Target-Reflector-Moderator Neutronics

10cm above/below Target B e protons in

0 100μ 200μ s s Target-Reflector-Moderator Neutronics

Decoupling

Cadmium absorptio Cd n protons in

0 100μ 200μ s s Target-Reflector-Moderator Neutronics

Decoupling

Cadmium absorptio Cd n

0 100μ 200μ s s Target-Reflector-Moderator Neutronics

Decoupling Poisoning Cadmium absorptio Cd n

Gadoliniu m absorption 0 100μ 200μ s s The time-of-flight (TOF) method distance

Data 1 3

2.5

1.5

0.5

0 -0.5 Δt time -1 -5 0 5 10 15 20

A The time-of-flight (TOF) method distance l = h /mv = 3.956 /v [Å] [m/ms]

Data 1 3

2.5

1.5

0.5

0 -0.5 Δt time -1 -5 0 5 10 15 20

A The time-of-flight (TOF) method distance

detector   2d sin  sample

Data 1 3

2.5

1.5

0.5

0 -0.5 Δt time -1 -5 0 5 10 15 20

A Moderator Decoupling & Poisoning

J-PARC H2 moderators at 10 17 1MW Hg Target Be reflector Coupled Peak Structure at 5meV 1MW 25Hz Coupled Decoupled /sr/eV/pulse)

/s 16 Poisoned 2 10 Decoupled

Poisoned (center) ILL cold (56 MW) 10 15

10 14 -4 -3 -2 -1 0 1

10 10 10 10 10 10 Pulse Peak Intensity(n/cm Energy (eV) Moderator Decoupling & Poisoning

10 17 Hg Target Be reflector Coupled 1MW 25Hz Cadmium absorption /sr/eV/pulse) /s 16 2 10 Decoupled

Poisoned (center) ILL cold (56 MW) 10 15

Gadolinium absorption 10 14 -4 -3 -2 -1 0 1

10 10 10 10 10 10 Pulse Peak Intensity(n/cm Energy (eV) Moderator Decoupling & Poisoning 1.4 Intensity

1.2

10 17 1 Hg Target Be reflector Coupled λ=1Å 1MW 25Hz

0.8 /sr/eV/pulse)

/s 16 2 10 0.6 Decoupled

λ=2Å Poisoned (center) 0.4 ILL cold (56 MW) 10 15 λ=5Å 0.2

time (μs) 0 10 14 -4 -3 -2 -1 0 1 10 10 10 10 10 10 0 100 200 Pulse Peak Intensity(n/cm -0.2 300 Energy (eV) 0 10 20 30 40

A SNS moderators

Top Bottom

decoupled poisoned H2

coupled H decoupled 2

coupled H2 poisoned H2O

20 cm ISIS TS2

decoupled poisoned

solid CH4

coupled H 2 Target: 66mm W coupled solid CH4

Water Jacket Moderator Temperature

ISIS-TS1 moderators at 160kW Comparison between pulsed sources

Facility Power Rep.Rat Start Instr. Thml AvB Thml Cold Cold e @1.5Å PkB AvB PkB @1.5Å @3Å @3Å ILL 57/57 MW - 1971 38 2.6x1013 2.6x1013 7x1012 7x1012 ISIS- 128/192 kW 50 Hz 1984 18 4x1010 5x1013 1.5x1010 7x1012 TS1 ISIS- 32/48 kW 10 Hz 2009 11 1.1x1010 4x1013 2.7x1010 1.8x1013 TS2 SNS 0.9/1.4 MW 60 Hz 2006 20 2.7x1011 1.5x1014 5x1011 5x1013 J-PARC 0.3/1.0 MW 25 Hz 2009 21 1.4x1011 2x1014 5x1011 1.3x1014 ESS -/5 MW 14 Hz 2019 22 1.1x1013 2.8x1014 9x1012 2x1014 Pulsed-source time structures cold neutrons log(Intensity) short pulse 10

0 100μ ILL 1 s ISIS- 0.1 TS1

0 20 40 60 80 100 120 time (ms) Pulsed-source time structures cold neutrons log(Intensity) short pulse 10

0 100μ ILL 1 s ISIS- ISIS- 0.1 TS1 TS2

0 20 40 60 80 100 120 time (ms) Pulsed-source time structures cold neutrons log(Intensity) short pulse 10

SNS 0 100μ ILL 1 s ISIS- ISIS- 0.1 TS1 TS2

0 20 40 60 80 100 120 time (ms) Pulsed-source time structures cold neutrons log(Intensity) short pulse 10 J-PARC

SNS 0 100μ ILL 1 s ISIS- ISIS- 0.1 TS1 TS2

0 20 40 60 80 100 120 time (ms) Pulsed-source time structures cold neutrons log(Intensity) long pulse 3ms 10 J-PARC ESS SNS ILL 1 ISIS- ISIS- 0.1 TS1 TS2

0 20 40 60 80 100 120 time (ms) Beyond short-pulse limits

SNS instantaneous power on target: 17kJ in 1μs: 17 1 GW x Reaches limits of spallation source technology: shock waves in target, space charge density in accelerator ring, …

Beyond short-pulse limits

simplif y

SNS instantaneous power on target: 17kJ in 1μs: 17 1 GW x ESS instantaneous power on target: 125MW 360kJ in 2.86ms

Long-Pulse Principle

Brightness Cold coupled 14 (n/cm2/s/ster/Å) 10 moderators λ=5ÅISIS TS1 ISIS TS2 SNS 1MW J-PARC 300kW ILL

0 1 2 3 time (ms) Long-Pulse Principle

Brightness Cold coupled 14 (n/cm2/s/ster/Å) 10 moderators λ=5ÅISIS TS1 ISIS TS2 SNS 1MW J-PARC 300kW ILL ESS 5MW

0 1 2 3 time (ms) Long-Pulse Principle

Brightness Cold coupled 14 (n/cm2/s/ster/Å) 10 moderators λ=5ÅISIS TS1 ISIS TS2 SNS 1MW J-PARC 300kW ILL ESS 5MW

0 1 2 3 time (ms) Long-Pulse Principle

Brightness Cold coupled 14 (n/cm2/s/ster/Å) 10 moderators λ=5ÅISIS TS1 ISIS TS2 SNS 1MW J-PARC 300kW ILL ESS 5MW

0 1 2 3 time (ms) Long-Pulse Principle

Brightness Cold coupled 14 (n/cm2/s/ster/Å) 10 moderators λ=5ÅISIS TS1 ISIS TS2 SNS 1MW J-PARC 300kW ILL ESS 5MW

0 1 2 3 time (ms) Thank you!

Ken Andersen Oxford School of Neutron Scattering ESS Neutron Instruments Division Oxford, 2013-09-04