1. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 1 EURATOM/VR Association, Department of Physics and Astronomy Division of Applied Nuclear Physics, Ångström Laboratory, Uppsala University, Sweden 2 EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, UK M Cecconello 1, S Conroy 1, G Ericsson 1, M Weiszflog 1, R Akers 2 and M Turnyanskiy 2 Study of advanced neutron diagnostics for MAST

2. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 2/39 Outline TRANSP neutron sources used in MCNP MCNP modelling and some results Collimators, detectors, DAQs and magnetic compatibility An appetizer from JT60U Fast ions, neutron emission and neutron diagnostic in MAST Proposed neutron camera for MAST and MAST Upgrade A look at the near future and conclusions

3. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 3/39 Redistribution of fast ions due to TAE in JT60U M Ishikawa et al Nucl. Fusion 47 (2007) 849–855

4. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 4/39 Most of the fusion neutron production is due to beam-thermal reactions the beam-beam term accounts for 10 -20 % of the total while the thermal-thermal is negligible. Neutron emission on MAST Neutron rate S n = 1 – 10 x 10 13 s -1 reduction in the beam-plasma interaction energy (due to the relative velocity of beam-thermal), leading to a reduced fusion reactivity. Energy shift of the neutron spectra. Effect of NBI heating and induced toroidal rotation: D + D  3 He (0.82 MeV) + n (2.45MeV), Q = 3.27MeV

5. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 5/39 Fast Ions and Neutron Emissivity The neutron emissivity profile is strongly dependent on the fast ion spatial and energy distribution. TRANSP simulated poloidal projections of co passing fast ion distributions with V || /V~0.7-1 with and w/o anomalous fast ion diffusion TRANSP simulated neutron source

6. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 6/39 Fast Particles Studies on MAST Study of fast ions driven modes is important to understand the redistribution and/or losses of fast ions that can affect the heating efficiency, the stored energy and cause damage to the PFCs. Document fast particle driven collective instabilities AE: TAE, EAE, BAE, Alfvén cascades, high frequency CAE Energetic Particle modes: chirping modes, long-lived modes Effects of fast ions upon core instabilities Typically n = 1 internal kink: sawteeth, fishbones, infernal mode Use on/off axis beams as source of fast ions Exploit specific capabilities of MAST Super-Alfvénic beams, V NBI ~ 2.5 V A Large fast ion fraction with high β (above ITER values) Externally driven modes (TAE antenna), n = 1 – 3

7. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 7/39 Example of instabilities and neutron yield on MAST “The LLM does not seem to cause notable plasma energy degradation in MAST discharges. However […] changes in the LLM frequency, possibly indicat[e] an enhancement of fast particle losses.” [1] Long Lasting Modes during NBI and current ramp-up t (s) S n (x 10 13 s -1 ) [1] M.P. Gryaznevich et al Nucl. Fusion 48 (2008) 084003 P NBI = 1.5 MW

8. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 8/39 MAST Present Neutron Diagnostic 235 U Fission Chamber (from PPPL) 1 - pulse (5 ms) and current (10 μs) modes - Campbelling mode (0.5 ms) - calibrated with a 252 Cf neutron source and backed up by activation foil measurement - no saturation expected with the increased neutron rate from NBI upgrades 1 (Planned installation of a spare 235 U and a 238 U for neutrons with E n > 1 MeV.) Used for total emission strength measurements (fusion reaction rate) relative emissivity profile  transport properties & MHD study the energy spectra  reacting ions energy distribution What have studied the possibility of:

9. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 9/39 Proposed neutron diagnostic for MAST and MAST U Horizontal fan of 14 lines of sight Vertical fan of 9 lines of sight Camera system consisting of: Collimator with liquid scintillator detectors Radial position of the detectors between 3 and 4 m Preferred location: MAST NPA location

10. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 10/39 Horizontal lines of sight

11. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 11/39 MAST SOUTH PINI Injector (2.5MW/5s) MAST SW Injector (2.2MW/0.4s) MAST Vessel CFC Beam Dumps MAST S-WEST PINI Injector (2.5MW/5s) Horizontal lines of sight and PINI injectors R = 4 m neutron camera

12. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 12/39 Vertical lines of sight MASTMAST Upgrade Massive PF coils in the way of a vertical stack of lines of sight.

13. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 13/39 TRANSP Simulation of MAST Neutron Source (cm -3 s -1 ) P NBI = 3.2 MW (co-NBI) I p = 0.6 MA T e  T i  0.8 keV Pulse 18821 @ 0.25 s Quasi-stationary H-mode plasma: Neutron emissivity radial profile

14. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 14/39 Synthetic MAST Neutron Source (cm -3 s -1 ) Neutron emissivity radial profile

15. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 15/39 TRANSP Simulation of MAST U Neutron Source (cm -3 s -1 ) P NBI = 10 MW (1 PINI co, 1 PINI counter, 2 PINIs off-axis co) I p = 1.2 MA T e  2.4 keV Neutron emissivity radial profile Scenario C (long pulse operation)

16. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 16/39 MCNP Model of MAST and of the Neutron Source Volume sampled for neutron spectra. Vertical sectionHorizontal section Neutron Source

17. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 17/39 MCNP Neutron Flux and Spectrum Calculations MCNP calculates: the flux of neutrons per MAST neutron the energy spectrum of the flux of neutrons per MAST neutron neutron flux (cm -2 s -1 )

18. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 18/39 Source Neutron Energy Spectrum For Maxwellian distributions, the energy distribution of the neutrons is very nearly Gaussian

19. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 19/39 Neutron Flux throughout MAST Area (midplane) log 10 (  MCNP )

20. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 20/39 Horizontal Lines of Sight & Neutron Emissivity MAST 14 13 12 11 10 9 8 7 6 5 4 3 2 1

21. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 21/39 Horiz. Lines of Sight & Neutron Emissivity MAST U 14 13 12 11 10 9 8 7 6 5 4 3 2 1 For MAST Upgrade the same lines of sight are used.

22. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 22/39 Neutron Collimator and Shielding for MCNP Polyethylene sphere: L = 50, 70 and 90 cm L D D = 11.24 and 35.68 mm A = 1 and 10 cm 2 Detector located at the sphere centre Detector area defined by the collimator diameter Collimator cross-section is circular

23. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 23/39 Horizontal Lines of Sight: Field of View @ R = 3 m L = 50 cm, A = 10 cm 2 L = 90 cm, A = 1 cm 2 radial field of view width  40 cm radial field of view width  8 cm

24. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 24/39 Collimated Neutron Energy Spectrum @ R  3.2 m L = 50 cm, A = 10 cm 2 L = 90 cm, A = 1 cm 2 MCNP Line of sight # 6

25. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 25/39 Horizontal Collimated Neutron Fluxes @ R  3.2 m L = 90 cm, A = 1 cm 2 central column shadowing

26. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 26/39 MCNP Direct Fluxes and Line Integrated Emissivity Line integrated emissivity along the line of sight Direct neutron flux (no neutron scattering)

27. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 27/39 Horizontal Collimated Neutron Fluxes @ R  3.2 m total direct backscattered shield scattered Neutron flux components

28. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 28/39 MAST Vertical Lines of Sight and Field of View L = 90 cm, A = 1 cm 2, R = 3 m vertical field of view width  4 cm

29. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 29/39 Vertical Collimated Neutron Fluxes @ R  3.2 m L = 90 cm, A = 1 cm 2

30. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 30/39 Expected Count Rates on MAST  detector efficiency 10 x A, 10 x S n A = 1 cm 2, S n = 10 13 s -1 10 x A, S n

31. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 31/39 Count Rate and Time Resolution on MAST Assuming a complete camera system, the count rate required for a neutron emissivity profile measurement with a Poissonian statistical uncertainty  = N -1/2 and a time resolution  t is:  t = 1 ms,  = 0.1  C  0.1 MHz With the present system (  3 MW NBI power)we can push the time resolution to 10 ms with a statistical uncertainty of 10 % (central channels), by using a vertically elongated collimator. For MAST Upgrade a the time resolution of less than 10 ms, with  = 0.1, might be achievable due to the much higher expected NBI power. This is NOT as an uncertainty of 10 % on the emissivity profile!

32. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 32/39 Different Collimator Cross-Sections circularelongated L = 90 cm, A = 1 cm 2 L = 90 cm, A = 4 cm 2

33. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 33/39 Neutron Collimator and Shielding Need of neutron collimation, shield against scattered neutrons and against  rays emission associated with capture of thermal neutrons by surrounding materials (neutron shield, magnetic shield, support structure). Boron loaded Polyethylene 0.48 MeV  are produced by 10 B(n,  ) 7 Li reduction of the 2.23 MeV  s Polyethylene (CH 2 ) 2.23 MeV  are produced by H(n,  )D Both give rise to significant  -background in the scintillator. MCNP estimate of  -background not yet performed.

34. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 34/39 Neutron Detector Liquid scintillators BC-501A (NE213) from Saint-Gobain Crystals Good PSD capabilities for n/  discrimination Hamamatsu R762 PMT Requires temperature control for stability and flash point (< 25 °C) Response function for neutron spectroscopy (energy calibration) Good contact with Physikalisch-Technische Bundesanstalt (2.5 MeV monoenergetic neutron sources,  sources). Calibration for absolute neutron yield measurements High efficiency (5 %) and high count rate capabilities Neutron  Recoil protons  photons LED Gain stabilization Temperature monitor SiPM (SensL) Insensitive to B field

35. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 35/39 Data Acquisition PMT Fast Amplifier Flash ADC Flash ADC with 1Gsamples memory, 10 bit resolution Sampling rate of 200 MHz (  t = 5 ns), 8 GHz maximum Raw data transfer in PC connected to flash ADCs after acquisition is finished Individual pulses are recorded (  t = 350 ns) Neutron/  discrimination and post processing is carried out via software on the PC Count rate of analog PSD systems is restricted by the gate integration time of the electronic circuit to 10 5 kHz.

36. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 36/39 Magnetic Field at Detector Location in MAST R (m)B (mT) 33246 42232 Poloidal field is mainly perpendicular to the PMT side R (m)B (mT) 3136 4100 MAST B  < 1 mT MAST Upgrade B  < 2 mT B (T) Magnetic shielding not too difficult.

37. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 37/39 What happens next ? 2008 - 2009 Proof-of-principle at MAST Single line of sight for radial and vertical scans Test of different collimator geometries Neutron emissivity profiles measurements 2009 Finalize design of neutron camera for MAST 2009 Application for partial funding to the Swedish Research Council (VR) Application in April, answer in November 2010/2011 ? Installation and Operation Extensive MCNP simulations Shielding and support, DAQS development Emissivity profiles from inversion of neutron camera data EFDA Priority Support: 0.33 ppy and 156 k€ for development

38. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 38/39 Neutron Camera on MAST and MAST U Reduced time resolution but spatially resolved neutron emissivity profiles t (s) S n (x 10 13 s -1 ) Fast ions spatial distribution Reacting ions energy distribution function

39. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 39/39 Conclusions Acknowledgments Special thanks to B Lloyd, G Cunningham, N Conway, M Dunstan, R Scanell, M Walsh and the MAST team. Single line of sight proof-of-principle for MAST is doable and can provide and indication of the neutron emissivity profiles in a reasonable amount of pulses. Neutron camera with L = 90 cm, A = 10 cm 2 is required for achieving in MAST high performing plasmas a time resolution of 10 ms with enough spatial resolution (at least 10 horizontal LoS, 9 vertical LoS) and sufficient statistic (10 % uncertainty). In MAST Upgrade, depending on the total NBI power available, the time resolution can be pushed below 10 ms (10 % uncertainty). In principle the same collimator structure can be used for both MAST and MAST Upgrade Liquid scintillators with DPSD seem ok

40. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 40/39 MAST Vertical Stack Not a viable solution due to PF coils presence.

41. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 41/39 Different Neutron Emissivity Profiles compared Line integrated neutron emissivity MAST 18821 MAST Synthetic

42. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 42/39 Post-experiment data processing pile-up reprocessing, dedicated n/  separation simultaneous n/  discrimination and PHA correction for PMT gain variations Digital Pulse Shape Discrimination n  Y. Kaschuck, Nuclear Instruments and Methods in Physics Research A 551 (2005) 420–428

43. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 43/39 Liquid Scintillator as Neutron Spectrometer pulse height counts sourcemeasured Courtesy of A. Zimbal Physikalisch-Technische Bundesanstalt The energy spectrum of neutrons provides information on their production mechanisms and the energy distributions of the reacting ions. recoil proton edge Compton electron edge

44. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 44/39 Liquid Scintillator Energy Calibration Low Z material:  interactions are Compton only L(E  ) = L (E n ) but E   2-3 E n E n : L(E n ) = L(E  ) electron energy equivalent L(E) is linear in E e non linear in E p Compton electron recoil proton eeeMeV

45. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 45/39 MAST U Vertical Lines of Sight and Field of View L = 90 cm, A = 1 cm 2, R = 3 m vertical resolution  4 cm

46. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 46/39 Magnetic Field at Detector Location in MAST Upgrade B (T) R (m)B (mT) 3136 4100 The poloidal field is mainly perpendicular to the PMT side The toroidal field is negligible (< 2 mT)

47. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 47/39 Photo-multiplier Magnetic Shielding Outer shield: soft iron (1 mm thick, r in = 23 mm) Inner shield:  -metal (0.8 mm thick, r in = 21 mm) 150 mT Shielding factor up to 10 4 0.2 mT B(T)

48. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 48/39 Neutron Energy Spectrum outside MAST Vessel

49. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 49/39 TRANSP Simulation of MAST Neutron Source - 3 P NBI = 3.5 MW (co-NBI) I p = 0.6 MA T e  T i  1.1 keV Pulse 18808 @ 0.28 s

50. M Cecconello et al 4 th IAEA Technical Meeting on Spherical Tori 14 th International Workshop on ST – Rome, Italy, October, 7 – 10, 2008 50/39 Counting modes Pulse Mode Current Mode Campbelling Mode