Reactor & Spallation Neutron Sources

Size: px

Start display at page:

Download "Reactor & Spallation Neutron Sources"

Dorothy Hamilton
6 years ago
Views:

1 Reactor & Spallation Neutron Sources Oxford School of Neutron Scattering Oxford, Ken Andersen ESS Instruments Division

2 ISIS ILL

3 Time evolution: Major neutron sources ILL BENSC (D) SINQ (CH) FRM-II (D) HFIR (USA) NIST (USA) JRR-3 (J) ISIS-1 (UK) ISIS-2 (UK) SNS (USA) J-PARC (J) ESS (S)

Neutron Sources ILL About 10 major neutron

ISIS 40 instruments 700 experiments a year Mainly

4 Neutron Sources ILL About 10 major neutron facilities worldwide Fission (continuous) Spallation (pulsed) User facilities Number 1 is Institut LaueLangevin (ILL) in Grenoble, France ISIS 40 instruments 700 experiments a year Mainly condensed-matter physics, but increasingly also chemistry and biophysics

5 ILL Reactor Neutron Source Highly-enriched uranium Compact design for high brightness Heavy-water cooling Single control rod 57MW thermal power 2.5 m

6 ILL Reactor Neutron Source cold thermal hot moderator liquid D 2 Liquid D 2 O graphite moderator temperature neutron wavelength sample lengthscale sample timescale 20K 300K 2000K 3 20Å 1 3Å 0.3 1Å 1Å 100 nm 1kHz 1 THz 0.3 5Å THz 0.1 2Å THz

7 ILL Reactor Neutron Source 2 nd guide hall (6 instruments) 1 st guide hall (20 instruments)

8 ILL Reactor Neutron Source

9 ILL Reactor Neutron Source HCS VCS HS Thermal beam tubes

10 Neutron Moderators at the ILL

12 Spallation Sources Spallation: 10x more neutrons per heat than fission 5MW spallation source = 50MW reactor Confusion: Heat input or output accelerators 10-20% effective Pulsed nature gives information which allows lower time-integrated flux P = IxV = 0.2-1MW efficient spallation requires proton E > 0.5 GeV => I = 0.2-1mA

13 Spallation Sources Continuous spallation source: SINQ at PSI in Switzerland Short-pulse spallation sources: ISIS, SNS, J-PARC H- Ion source Linear accelerator (normal- or super-conducting) Stripper converts H- to H+ Synchrotron Target Reflector Moderators

14 H- ion source SNS ISIS

15 Linac (drift tube)

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

17 ISIS (200kW)

18 SNS, Oak Ridge, Tennessee, USA (500kW in 2010, 1MW in 2012)

19 J-PARC, Tokai, Japan (100kW in 2010, 1MW in 2015)

20 J-PARC, Tokai, Japan (100kW in 2010, 1MW in 2014)

21 Pulsed-source time structure Intensity λ=1å" λ=2å" λ=5å" time (μs)"

22 log(intensity) Pulsed-source time structures cold neutrons short pulse µs ILL 0.1 ISIS-TS time (ms)"

23 log(intensity) Pulsed-source time structures cold neutrons ISIS-TS1 ISIS-TS2 ILL time (ms)"

24 log(intensity) Pulsed-source time structures cold neutrons SNS ISIS-TS1 ISIS-TS2 ILL time (ms)"

25 ISIS target 1: solid tungsten

26 SNS target: liquid mercury

27 J-PARC target

29 SNS target

30 Target-Reflector-Moderator Neutronics Target produces neutron in MeV range Moderators contain H to thermalise neutrons Largest scattering cross-section (80b) Lowest mass Moderators embedded in reflector, usually D 2 O-cooled Be Minimal absorption Large scattering cross-section (8b) Little thermalisation

31 SNS moderators Top Bottom decoupled poisoned H 2 coupled H 2 decoupled poisoned H 2 O coupled H 2 20 cm

Additional time-broadening: coupling between moderators and reflector Decoupling:

32 Target-reflector-moderator neutronics Proton pulse > 1 s Neutrons moderated by H Several cm depth of H required to thermalise 4Å neutron speed: 1cm / 10 s Additional time-broadening: coupling between moderators and reflector Decoupling: Cd between moderator and reflector Transparent above 0.3 ev Poisoning: Gd inside moderator

33 Pulsed-Source Moderators Intensity λ=1å λ=2å λ=5å decoupled coupled time ( s)

34 SNS moderators Top Bottom decoupled poisoned H 2 coupled H 2 decoupled poisoned H 2 O coupled H 2 20 cm

35 J-PARC coupled moderators Time Averaged Intensity (for CM) :1/4 of ILL Cold source Pulse Peak Intensity (for CM) ~100 of ILL Cold source Peak Structure at 5meV Coupled Decoupled Poisoned #35

36 ISIS TS2 decoupled poisoned solid CH 4 coupled solid CH 4 coupled H 2 Target: 66mm W Water Jacket

37 The future: Long-pulse spallation sources ESS, Sweden SNS 2nd Target Station

38 simplified Long pulses: use only linac

39 log(intensity) Pulsed-source time structures cold neutrons SNS ISIS-TS1 ISIS-TS2 ILL time (ms)"

40 log(intensity) Pulsed-source time structures cold neutrons long pulse 10 1 SNS 3ms ESS ILL 0.1 ISIS-TS1 ISIS-TS time (ms)"

41 Intensity Long-Pulse Principle time (ms)"

42 Intensity Long-Pulse Principle time (ms)"

43 Intensity Long-Pulse Principle time (ms)"

44 Intensity Long-Pulse Principle time (ms)"

45 Intensity Long-Pulse Principle time (ms)"

46 ESS Target Station

47 ESS Target Station

48 Thank you! Oxford School of Neutron Scattering Oxford, Ken Andersen ESS Instruments Division

SPALLATION NEUTRON SOURCES FOR SCIENCE AND TECHNOLOGY

Proceedings of the 8 th Conference on Nuclear and Particle Physics, 20-24 Nov. 2011, Hurghada, Egypt SPALLATION NEUTRON SOURCES FOR SCIENCE AND TECHNOLOGY M.N.H. Comsan Nuclear Research Center, Atomic