Neutron based instruments for application to fusion and spallation sources

Transcription

1 Dipartimento di fisica G. Occhialini Università Degli Studi di Milano-Bicocca Seminar for the first annual research activities Neutron based instruments for application to fusion and spallation sources Song FENG (XXXI cycle Ph.D Student) October 1 th, 216 Tutor: Dr. Marco Tardocchi Cotutor: Prof. Giuseppe Gorini

2 2 Outline Background ChipIR and Single-event effects ITER and Neutral Beam Injector Telescope Proton Recoil Neutron Spectrometer Beam-target neutron emission at the ELISE Conclusions and future plans

3 Background 1. ChipIR and single event effects Atmospheric Fast Neutron Beams Pencil & Flood Target Fast Neutron Beam Be reflector Secondary Scatterer to produce beams Micro-electronic devices failure Single-event effects (SEE) Cosmic radiation (neutrons) Mimic the atmospheric fast neutron spectrum with times higher intensity at ground level Proton Beam (8MeV) Direct measurements of the neutron energy spectrum and flux: can benchmark the simulations; understand the underlying physics of this kind of facility better. Challenges High energy (up to 8MeV) High intensity (>1 6 neutrons cm 2 s 1 with En>1MeV) Complex background (Neutrons, Protons, Gamma rays ) Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Telescope Proton Recoil Neutron spectrometer Diamond Detectors Bonner Spheres Fission Counters Activation Foils 3/3

4 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 4/3 Background 2. ITER and Neutral Beam Injector PRIMA (Padova Research on ITER Megavolt Accelerator). Neutralization efficiency PRIMA SPIDER Negative ion source MITICA Full power injector DD fusion neutron measurement has been proposed as diagnostics of the beam homogeneity. Detailed physics behind this process can be investigated at ELISE and used to aid the detector design for beam diagnostics at SPIDER. ELISE test facility is an intermediate step between the currently used small sources and the test bed SPIDER.

5 5 Outline Background ChipIR and Single-effect events ITER and Neutral Beam Injector Telescope Proton Recoil Neutron Spectrometer Beam-target neutron emission at the ELISE Conclusions and future plans

6 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 6/3 2. TPR Neutron Spectrometer 1. Method Elastic scattering, (n, p) reaction Neutrons Thin target (CH 2 ) θ E p =E n cos 2 θ Signals ΔE Detector E Detector Coincidence Intensity/source Proton spectrum,mcnp Energy/MeV Advantages Good capability of spectrum unfolding; Detection efficiency can be calculated quite accurately (can be used to measure beam intensity) Disadvantage Low detection efficiency TPR neutron spectrometer was designed for measuring the fast neutron from 1 to 12MeV. A thin YAP (.1 in thickness) has been characterized on light output under 2MeV before. A thick YAP (1 1 ) was characterized here to extended the energy up to 8MeV.

7 2. TPR Neutron Spectrometer 2. Measurement at INFN-LNS (Catania) Proton energy from the Cyclotron accelerator: 62 MeV and 8 MeV 45 LaBr 3 detector Al foils 1 1 CH cm 22.5 Thin YAP + Au-Si Au Protons Some Al foils were placed at the front of the Au-Si detector to change the energy of incident protons. Calibrated with 6 Co and 137 Cs. Thick YAP + Au-Si Collimator Vacuum Chamber Song FENG. Seminar for the 1st annual research activities October 1 th, 216 7/3

8 Pronton energy on the thick YAP /MeV Song FENG. Seminar for the 1st annual research activities October 1 th, 216 8/3 2. TPR Neutron Spectrometer 3. Calculation of incident proton energy YAP 27.5 cm Protons θ 14 cm A B on H on C E E '' p ' p E p cos 2 θ 2 cos A sin ( 1 Α 2 θ ) 2 E p Ep=62 MeV MCNP Pstar Ep=8 MeV MCNP Pstar Position Coefficient on H, K 1 Coefficient on C, K 2 A Middle B (A-B)/Mid 8.3%.7% The thickness of Al foils before the detector /mm

9 2. TPR Neutron Spectrometer 4. ΔE-E particle discrimination Coincidence events as a function of the time difference of YAP and Si events (E and ΔE). E and ΔE events are considered to be in coincidence if the time difference Δt of their maxima falls inside a selected Δt window. A further tool for data reduction is given by the relation between E and ΔE. The peak scattering on C was only contributed by protons and was used to calibrate the detector here Song FENG. Seminar for the 1st annual research activities October 1 th, 216 9/3

10 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 1/3 2. TPR Neutron Spectrometer 5. Background analysis Intensity/source -1 3.x x1-7 Kill the collimator Original 2.x x1-7 1.x1-7 5.x1-8 2-D flux distribution of protons with the collimator and with a killed collimator Energy/MeV The lowest energy proton peak at 8MeV measurements was contributed by the leakage protons from the collimator. A proton peak was also observed on the background spectrum at the position of the proton peak scattering on C. It was contributed by the scattering protons on air.

11 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Intensity/counts 11/3 2. TPR Neutron Spectrometer 5. Background analysis Intensity/source x1-7 3.x x1-7 2.x x1-7 1.x1-7 5.x1-8 Ep=8MeV, line scale With target Without target Scattering on H Scattering on C Intensity/source Ep=8MeV, log scale With target Without target Scattering on H Scattering on C Proton energy on YAP/MeV Proton energy on YAP/MeV calculated pulse height spectra with and without plastic target Pulse height/channel The analysis of a measured PHS The double humped proton peak on measured PHS was analyzed by fitting with 2 Gauss peaks. The 2nd peak was assumed as the background and the 1st peak was used in this characterization.

12 Intensity(Counts) Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Intensity(Count) 12/3 2. TPR Neutron Spectrometer 6. Uncertainty analysis Ep=62 MeV RUN5 RUN15 RUN16 RUN Ep=8MeV RUN35 RUN36 RUN37 RUN38 RUN21 RUN42 RUN43 RUN Pulse height (channel) Movement of the channel at 62 and 8MeV Pulse height (channel) Measurements were performed for a long time with the same condition and a movement of peak channel was observed. The relative uncertainty was defined as about 9.8% for 62 MeV measurements and about 4.3% for 8 MeV measurements. As the channel shift can't be defined, the worst scenario 9.8% that was observed so far was used for all measurements. Statistical error is less than.5% and is negligible here.

13 Intensity/Counts Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Pulse height/channel 13/3 2. TPR Neutron Spectrometer 7. Calibration with γ sources Co-6 Cs-137 Full energy peak V 7V Chn= E Chn= E Pulse height/channel Energy/MeV The electron equivalent energy scales (in MeVee, MeV electron equivalent) of the spectra were obtained by calibrating with 137 Cs (.662MeV) and 6 Co (1.17 and 1.33MeV) γ sources.

14 Song FENG. Seminar for the 1st annual research activities October 1 th, /3 2. TPR Neutron Spectrometer 8. Light output Light output/mev ee E ee =( )E p +( ) E ee =( )E p +( ) Ep=62MeV Ep=8MeV Energy of incident protons/mev The relative light yield of the YAP:Ce crystal was determined to be (67.9±16.6)% for 8 MeV protons and (8.2±3.3)% for 62 MeV protons. Two measurements are consistent within the uncertainty. As the long term instability of the PMT gain was observed, a revision of the TPR design consist of adding a monitor light source to correct for long term shifts is suggested.

15 2. TPR Neutron Spectrometer 9. Conclusion and outlook Characterization of the TPR spectrometer based on a 1'' 1'' YAP(Ce) crystal to protons up to 8MeV was performed. The thick YAP(Ce) crystal shows a linear response in light output. The relative light yield was measured to be in the range of 51.3% to 83.5%. Two measurements with 62MeV and 8MeV protons are consistent within the experimental uncertainty. The observed long term instability of the PMT gain does not allow for an accurate measurements. A revision of the TPR design, which could consist of adding a monitor light source to correct for long term shifts, is suggested. In the future a Geant4 model will be developed, allowing a higher flexibility in the selection of high proton energy data bases and the modified nuclei model for data files. Song FENG. Seminar for the 1st annual research activities October 1 th, /3

16 16 Outline Background ChipIR and Single-effect events ITER and Neutral Beam Injector Telescope Proton Recoil Neutron Spectrometer Beam-target neutron emission at the ELISE Conclusions and future plans

17 Song FENG. Seminar for the 1st annual research activities October 1 th, /3 Background ITER and Neutral Beam Injector PRIMA (Padova Research on ITER Megavolt Accelerator). Neutralization efficiency PRIMA SPIDER Negative ion source MITICA Full power injector DD fusion neutron measurements have been proposed as diagnostics of the beam homogeneity. Detailed physics behind this process can be investigated at ELISE and used to aid the detector design for beam diagnostics at SPIDER. ELISE test facility is an intermediate step between the currently used small sources and the test bed SPIDER.

18 Song FENG. Seminar for the 1st annual research activities October 1 th, /3 3. Beam-target neutron emission at the ELISE 1. Background and motivation A parasitic experiment was performed at the ELISE facility in 214; A calibrated EJ31 liquid scintillator was used to measure neutron emission and benchmark calculations based on the Local Mixing Model (LMM) of deuterium implantation in the dump. In particular, the calculations seem to systematically overestimate neutron emission, with differences that are more pronounced at the highest counting rates, up to even 4% on a relative scale. Need a dedicated experiment to clarify this discrepancy. More accurate input data for calculation with new developed infra-red and calorimetry diagnostics.

19 Current/A Song FENG. Seminar for the 1st annual research activities October 1 th, 216 High voltage/kv 19/3 3. Beam-target neutron emission at the ELISE 2. Experimental I_Ion I_Calorimeter Time/s U-HV Time/s Deuteron ion beam was produced pulse by pulse and only the effective time for each pulse has been considered (net of pauses). The dedicated experiment was performed with increasing I from 5 to 17 A and a fixed voltage 3kV. Neutron emission was monitored by means of the same detector used in our previous experiment. A calibrated EJ31 liquid scintillator + a Hamamatsu H158 photomultiplier tube. A 14 bit, 4 MS/s digitizer based on the ATCA platform. Neutron/gamma-ray discrimination based on the different shapes of the waveforms.

20 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 2/3 3. Beam-target neutron emission at the ELISE 3. Neutron emission calculation with LMM Schematic diagram of the Local Mixing Model The neutron yield Y(t) can be calculated with the flux of deuteron beam in the target Φ(z,t), the number of deuteron deposited in the target n(z,t) and the D-D neutron production cross section σ(z,t):

21 Probability of deposition (%) Song FENG. Seminar for the 1st annual research activities October 1 th, /3 3. Beam-target neutron emission at the ELISE 3. Neutron emission calculation with LMM (1). Deuteron flux Φ(z, t) Φ(z, t) is the deuteron flux at depth z, which can be calculated by the deuteron current, deuteron energy and the TRansport of Ion in Matter (TRIM) program: High voltage (kev) Depth/ m Calculated distribution of probability of deuteron deposition with TRIM

22 Total stopping power(kev/um) Total stopping power(kev/um) Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Neutron produced DD cross section(mbar) Neutron produced DD cross section(mbar) 22/3 3. Beam-target neutron emission at the ELISE 3. Neutron emission calculation with LMM (2). Deuteron at depth z, n(z, t) Deuteron has maximum concentration rate in the copper. Assume the concentration rate at depth z and time t is c(z,t), saturated concentration rate is C s (2%) and the copper density is n cu : (3). Cross section σ(z, t) Stopping power calculated by TRIM; cross section used nuclear data library ENDF/B-VI. 18 de/dx vs energy 12 de/dx vs depth D-D cross section vs energy D-D cross section vs depth Energy/keV Depth/um Energy/keV Depth/um

23 3. Beam-target neutron emission at the ELISE Analysis of calculation Influence of beam 5 profile on the 5dump ,Normalized x x ,Normalized x x ,Normalized x x x Full size,normalized Half size,normalized x1 9 5x1 9 Neutron yield/ns -1 4x1 9 3x1 9 Full size Half size From full to half at 5s From full to half at 15s Time/s Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Neutron yield/ns -1 4x1 9 3x1 9 2x1 9 1x1 9 Full size Half size From half to full size at 15s Time/s Comparison of neutron intensity with different beam profiles in calculation Left: Use the full size beam profile at the beginning and then change to the half size beam profile at 5s and 15s; Right: Use the half size beam profile at the beginning and then change to the full size beam profile at 15s 23/3

24 Song FENG. Seminar for the 1st annual research activities October 1 th, /3 3. Beam-target neutron emission at the ELISE 5. Comparison of measurements and calculations Normalization area The simulation was normalized to convert from calculated neutron yield Y(t) to the measured counting rate with a coefficient, which also depends on neutron transport from the dump to the detector, besides the scintillator detection efficiency to neutrons. There is generally a better agreement with calculations based on I cal, as expected. Compared to our former experiment (a disagreement at the level of 4% at I=8 to 1 A), an accurate knowledge of the beam profile and current is essential for a reliable determination of the neutron emission and improves the agreement to a better than 1% level.

25 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 Discrepancy(%) 25/3 3. Beam-target neutron emission at the ELISE 5. Comparison of measurements and calculations 15 6% 9% 1% 12 SPIDER Discrepancy (%) =.3533 Power R 2 = Power (U I) The discrepancy gets higher as the current is increased. Some additional deuterium diffusion caused by temperature effects away from the saturation state must be included in the model to completely account for the observations. Diffusion effects may reduce neutron emission up to a factor 1.35 in full power operations at SPIDER (4A,1kV) based on the assumption that deuterium diffuse outside the LMM scales as the beam power.

26 Song FENG. Seminar for the 1st annual research activities October 1 th, /3 3. Beam-target neutron emission at the ELISE 6. Conclusion and outlook A dedicated experiment on beam-target neutron emission has been performed at the ELISE neutral beam test facility to investigate the accuracy of Local Mixing Model based calculations for the design of neutron diagnostics at SPIDER. Neutron emission can be described with an accuracy better than 1% at V=3 kv and I=7 to 17 A by using Improved beam current and profile diagnostics, which compares to about 4% in the previous experiment. Measured neutron emission is mostly sensitive to variations of the current hitting the dump. Diffusion effects beyond the Local Mixing Model are at play in beamtarget reactions and becomes progressively more important as current is increased. Diffusion effects may reduce neutron emission up to a factor 1.35 in full power operations at SPIDER (4A,1kV) based on the assumption that deuterium diffuse outside the LMM scales as the beam power. A quantitative determination of the diffusion coefficient required to further reconcile calculations and measurements in future experiments at the highest currents and voltages available at ELISE.

27 27 Outline Introduction ChipIR and Single-effect events ITER and Neutral Beam Injector Telescope Proton Recoil Neutron Spectrometer Beam-target neutron emission at the ELISE Conclusions and future plans

28 4. Conclusions Finished. Characterized the TPR neutron spectrometer based on a 1'' 1'' YAP(Ce) crystal to protons up to 8MeV. The thick YAP(Ce) crystal shows a linear response in light output from 51.3% to 83.5%. Analyzed the beam-target neutron emission at ELISE to investigate the accuracy of LMM based calculations for the design of beam diagnostics at SPIDER. Next... A new test in Catania to overcome the problems we had with the new detector design that includes a source to monitor the instability. Proposal submitted. The test of the TPR with neutrons at ChipIR. Proposal for a new experiment at ELISE at high power to QUANTIFY the extent of diffusion effects in beam-target neutron emission; revision of the calculations for SPIDER based on the outcome of that experiment Song FENG. Seminar for the 1st annual research activities October 1 th, /3

29 4. Conclusions Schools & Courses Summer school on Neutron detector and related applications - NDRA 216 June 29th July 2nd, 216, Riva del Garda, Trento, Italy Monte Carlo Simulation of Radiation Detectors prof. Giuseppe Gorini, Dr. G. Croci Publications & Posters S. Feng, R. Liu, X. X. Lu, et al. A study of 239 Pu production rate in a water cooled natural uranium blanket mock-up of a fusion fission hybrid reactor. Nuclear Fusion 56 (216) M. Nocente, S. Feng, D. Wunderlich, et al. Experimental investigation of beam-target neutron emission at the ELISE neutral beam test facility. Submitted to Fusion Engineering and Design. Poster: S. Feng, C. Cazzaniga, T. Minniti, M. Nocente, A. Muraro, M. Tardocchi, G. Gorini. Light response of a YAP:Ce scintillator to protons up to 8MeV for application to a TPR Spectrometer. On summer school NDRA 216, Trento, Italy. Poster: S. Feng, M. Nocente, G. Groci, et al. Experimental investigation of beam-target neutron emission at the ELISE neutral beam test facility. Proceeding of the 29 th Symposium on Fusion Technology, September 5 th 9 th 216, Prague, Czech Republic. Song FENG. Seminar for the 1st annual research activities October 1 th, /3

30 Seminar for the first annual research activities Thank you for your attention! October 1 th, 216 Song FENG. 3/3

31 Song FENG. Seminar for the 1st annual research activities October 1 th, 216 C/E 31/3 Beam-target neutron emission at the ELISE Comparison of measurements and calculations Neutron intensity/ns x1 5 1.x1 5 8.x1 4 6.x1 4 4.x1 4 2.x1 4. Experiment Ion current, I_ion Current on dump, I_cal Time/s I_ion I_cal Time/s Coefficient k was found by using the least squares method and was used to convert from calculated neutron yield to the experimentally measured neutron rate.(neutron transport & detection efficiency) In general, calculations compare significantly better to measurements by using the current on the dump, especially when the dump was seemed as saturated (yellow area). Problem: NO camera data and neutron measurements at the first 1 s.(gray area)

32 Song FENG. Seminar for the 1st annual research activities October 1 th, /3 Beam-target neutron emission at the ELISE Neutron measurements on SPIDER SPIDER experimental area: the beam dump is shown in yellow. Top view of the beam dump: the detector boxes are shown in green. Requirements: it should serve a well defined purpose as a diagnostic of SPIDER and provide information with a clear impact on the optimization of the SPIDER beam quality; it should be practical in terms of engineering integration in the device; the new diagnostic concept should be carried over to MITICA.