Neutron Metrology at PTB

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1 Neutron Metrology at PTB - Technical Infrastructure - Calibration Services - Research & Development R. Nolte Physikalisch-Technische Bundesanstalt Braunschweig, Germany Department 6.4

2 Mission of PTB What are PTB's capabilities? PTB measures with the highest accuracy and reliability metrology as the core competence For whom does PTB work? PTB stands for progress and reliability in metrology for the benefit of society, trade and industry, and science Organization: Highest technical authority under the auspices of the Federal Ministry of Economics and Labour (BMWA) Sites: Braunschweig, Berlin-Charlottenburg Staff: 1500 staff members Structure: Nine scientific and technical divisions (two of them in Berlin), subdivided into more than 100 sections and projects Annual budget: about 130 million Euro 2

3 Neutron groups at PTB Department 6.4: Ion accelerators and radiaton reference fields with: - WG1: accelerators - WG2: micro-ionbeam - WG3: reference fields - WG4: neutron cross section meas. Department 6.5: Neutron Radiation with: - WG1: detectors and data acquisition -WG2: n/γ-dosimetry -WG3: n/γ-spectrometry - WG4: radionuclide sources 3

4 Expertise in neutron detection at PTB Neutron generators need neutron detectors data analysis and neutron cross sections! PTB provides expertise in: Characterization of neutron beams from 25 mev to 200 MeV Irradiation in reference fields Data analysis techniques Neutron cross section measurements Development and modeling of detectors Upgrading of small-scale accelerators (VdG, Cyclotron) 4

5 Reference Fields at the Accelerator Facility Mono-energetic Neutrons according to ISO 8529, Sc (p;n) 45 Ti :24,5 kev 7 Li (p;n) 7 Be:144; 250; 565 kev T (p;n) 3 He: 1,2; 2,5 MeV D (d;n) 3 He: 5,0; 8,0 MeV T (d;n) 4 He: 14,8;19,0 MeV optional: 65 Cu (p;n) 65 Zn:1,2 kev Experimental Hall 25 m 30 m 14 m High Energy Photons according to ISO C (p;p γ) 12 C:4,443 MeV 19 F (p;αγ) 16 O: 6,13; 6,92; 7,12 MeV optional: 23 Na (p;γ) 24 Mg:8,93 MeV 11 B (p;γ) 12 C: 4,443;12,15;16,49 MeV 7 Li (p;γ) 8 Be:14,7; 17,64 MeV Intense Collimated Neutron Field with Broad Energy Distributions 9 Be + d (13,5 MeV) :< E n > 5 MeV 9 Be + p (22,0 MeV) :< E n > 10 MeV Compact Cyclotron v.d.graaff Accelerator Micro-Ionbeam diameter:< 2µm FWHM energies: 0.2 < E p < 20 MeV 0.4 < E α < 28 MeV 5

6 PTB Accelerator Facilty 3.75 MV van-de-graaff: p, d, α beams ns pulsing system (1.5 3 ns) CV28 isochronous cyclotron: p, d, α, ( 14 N) beams E p < 19 MeV, E d < 13.5 MeV, E α < 28 MeV internal pulse selector 6

7 Low-Scatter Facility in Chadwick Building 7

8 Monoenergetic Neutron Field Spectral fluence of monoenergetic neutrons from: T (p,n) 3 He E n = 1.2 MeV determined by: - TARGET- MC simulation Ti(T)-target; 1 mg/cm 2 Ti 0.5 mm Ag-backing - TOF-measurements (plastic scintillator at 3.5 m) - fluence determined with hydrogen proportional counter (standard uncertainty 2.5 %) (cm 2 MeVµC) -1 Φ E (E) / Q S00.ENE GU µg/cm 2 E p =2.050 MeV SDD=301.6 cm E n =1.203 MeV ,0 0,2 0,4 0,6 0,8 1,0 1,2 MeV 1,4 E Dr. Dietrich Schlegel PTB 6.41 contents uncollided scattered total experiment uncollided scattered total 07/09/ : ns 500 t Dr. Dietrich Schlegel PTB :28:40 8

9 Monoenergetic Neutrons 1.2 MeV 10 3 (cm 2 MeVµC) uncollided scattered total 10 3 (cm 2 MeVµC) uncollided scattered total Φ E (E) / Q 10 0 Φ E (E) / Q ,0 0,2 0,4 0,6 0,8 1,0 1,2 MeV 1,4 E 10 5 Dr. Dietrich Schlegel PTB S00 02-Sep ,0 0,2 0,4 0,6 0,8 1,0 1,2 MeV 1,4 E 10 5 Dr. Dietrich Schlegel PTB S02 02-Sep experiment uncollided scattered total 10 4 TOF measurement MC uncollided MC scattered MC total contents 10 2 contents ns 500 t Dr. Dietrich Schlegel PTB 6.41 S68E02_mcT 02-Sep-2002 T(p,n); Ti(T)-target; 1 mg/cm 2 Ti ns 400 t Dr. Dietrich Schlegel G68E12_mcT 02-Sep-2002 T(p,n); Ti(T)-target; 2 mg/cm 2 Ti 9

10 Monoenergetic Neutrons: 2.5 MeV and 5.0 MeV (cm 2 MeVµC) uncollided scattered total (cm 2 MeVµC) uncollided scattered total Φ E (E) / Q Φ E (E) / Q ,0 0,5 1,0 1,5 2,0 2,5 MeV 3,0 E Dr. Dietrich Schlegel PTB S01 experiment uncollided scattered total 02-Sep MeV 6 E Dr. Dietrich Schlegel PTB experiment uncollided scattered total S00 02-Sep-2002 contents 10 2 contents ns 500 t Dr. Dietrich Schlegel PTB 6.41 G68F02_mcT 02-Sep ns 500 t Dr. Dietrich Schlegel PTB 6.41 G68G15_mcT 02-Sep-2002 Ti(T)-target; 2 mg/cm 2 Ti Ti(D)-target; 2 mg/cm 2 Ti 10

11 Calibration Servives for Monoenergetic Neutron reaction <E n > E target (dφ/dt) Φ sc/φ (dη (10)/dt) MeV MeV cm -2 s -1 % msv h -1 7 Li (p,n) 7 Be LiOH Li (p,n) 7 Be LiOH Li (p,n) 7 Be LiOH Li (p,n) 7 Be LiOH 1.2E H (p,n) 3 He Ti(T) H (p,n) 3 He Ti(T) H (d,n) 3 He D 2 -Gas < H (d,n) 3 He D 2 -Gas < H (d,n) 4 He Ti(T) H (d,n) 4 He Ti(T) Fields produced according to ISO-standard 8529 QA system according to ISO-standard

12 High-Intensity Collimated Neutron Fields High-intensity neutron beams: Be + d ( < MeV) thick target yield for : E d = 9.43 MeV(a), MeV(b) and MeV Y s -1 for I d = 80 µa Be + p ( < 21 MeV) thick target yield for: E p = MeV(a), MeV(b) and MeV Y s -1 for I p = 80 µa More details: H.J. Brede et al., NIM A274 (1989)

13 D(d,n) neutron source 10 4 D(d,n): E n,0 = 9.5 MeV 10 4 D(d,n): E n = 14.8 MeV 10 3 gas in gas in events/bin 10 2 gas out events / bin 10 3 gas out TOF / arb. units TOF / arb. units No monoenergetic neutron sources available between 6 14 MeV D 2 + d: monoenergetic neutrons: D(d,n) 3 He breakup continuum: D(d,np)D careful study required! D(d,n)n2p Gas target: good background subtaction 13

14 Thermal Neutron Reference Field Research Reactor Geesthacht FRG-1: beamline 7 flight path (chopper- scanner) : 6.5 m 14

15 Properties of the Thermal Beam (N E /N ) / ev thermal beam at FRG-1: measured (TOF) Maxwellian (kt = 23.8 mev) rel. intensity E n / mev horizontal scan Thermal energy distribution: <E n > 48 mev Very low contamination with epithermal neutrons and photons! Fluence rate: ϕ < 10 5 cm -2 s -1 Dose rate: dh*(10)/dt < 5 msv/h Inhomogeneous beam profile (energy, intensity): Sanning required! 15

16 Thermal Neutron Reference Field diaphragm x 2.5 cm 2 double prisma 3 He monitor 16

17 Traceability to the activity standard Reference reaction: 197 Au(n th,γ) 198 Au Measurements: areal mass of foil: m F J E /J via TOF + σ a (E): <σ a > 4π βγ counting: A( 198 Au) Comparison of activation method with 6 LiGlass detector: Beam profile Campaign J W (σ0) <J > Au (<σa>) J LiGlass 10 5 s s s -1 C ± ± ± 0.03 C ± ± ± 0.06 Main contributions to total uncertainty of activation method: u m /m F = u <σ > /<σ a > = u A /A = u <J> /<J> = More details: R. Böttger et al., PTB report PTB-N-47 (2004) 17

18 High-Energy Neutron Fields Quasi-monoenergetic high-energy neutrons: 7 Li(p,n) E p = MeV Catholic University (UCL) in Louvain-la-Neuve / Belgium (E p = MeV) (Φ E /Φ ) / MeV proton energy loss in Li target ithemba Laboratory (TLABS) 0.05 in Somerset West / South Africa ( E p = MeV) E n / MeV More details: R. Nolte et al., NIM A 476 (2002) ) 18

19 High-energy photon fields High-energy photon fields: 12 C(p,p γ) 12 C: 4.4 MeV 19 F(p,αγ) 16 N: 6-7 MeV Important for BWR s: 16 O(n,p) 16 N* 4.4 MeV field contaminated with neutrons: 13 C(p,n) Spectrometry with Liquid scintillation detectors HPGe detectors Dosimetry: Ionization chambers (responsible: PTB dep. 6.3) other (p,γ) reactions of interest for interrogation techniques can be investigated 19

20 Reference Instruments: RPPC Cylindrical Proportional Counter for E n 1.2 MeV Counting gas H 2 /CH 4 (965 / 35 hpa) 24 kev E n 250 kev C 3 H 8 (600 hpa) 250 kev < E n 1.2 MeV Efficiency: MCWALL (tracking of recoil protons) + MCNP (neutron transport) Subtraction of room scatter with shadow cone method Photon sensitivity becomes a problem below 24 kev 20

21 Reference Instruments: RPT Recoil proton telescopes for E n > 1.2 MeV Optimized design for different energy ranges (RPT 1-3) Efficiency calculations: deterministic: FLX (only for RPT 1) Monte Carlo: SINENA, RPT2, WYHET n-p cross section: E n < 20 MeV: ENDF/B-V E n > 20 MeV: VL35 (phase shift analysis) 21

22 235,238 U Fission ionization chambers counts per bin α particles fission fragments pulse height / arb. units built at Harwell Lab., U.K. Components 5 electrodes with fissile material on both sides sensitive diameter 76 mm 200 mg 235 U or 238 U (440 µg/cm 2 ) mass of fissile material determined with 0.3% uncert. efficiency of fission fragment detection: 96% time resolution 5 ns (fwhm) fission events clearly separated from α-events in the pulseheight spectrum 22

23 Scintillation Detectors H/C ratio 1.2: response based on well-known n-p cross section Maximum pulse height proportional to neutron energy: spectrometry n/γ separation via pulse shape analysis: mixed neutron/photon fields Fast signals: high rates, TOF spectrometry However: all these properties are far from perfect! Carefull study required: Light yield Resolution Pulse height reponse Timing properties 23

24 Calculational Characterization Monte Carlo Simulation have to follow individual reaction chains! 12 C(n,α) 9 Be* n + 8 Be 2α 12 C(n,n') 12 C* α+ 8 Be 2α Input for Monte Carlo codes: Light yield functions Resolution functions Nuclear data Established codes: up to 20 MeV: NRESP7 20 MeV MeV: SCINFUL above 100 MeV: MCNPX? Nota bene: small deviations in the response significant effects in unfolded spectra! (dn/dl) / arb. units 10 3 events/bin α-emission from 12 C* C(n,px) + 12 C(n,dx) + 12 C(n,αx) +... L / MeV 12 C(n,d) E n = 45 MeV exp. SCINFUL L / MeV 12 C(n,p) E n = MeV exp. NRESP7 n-p scattering 24

25 Experimental Characterization Monoenergetic neutrons: D(d,n) 3 He White neutron spectra: D(d,nx), Be+p (TOF cuts) Light yield and resolution from comparison of exp. and calc. response Counts per bin MeV MeV MeV MeV MeV L / arb. units Results: Each detector has it s own light yield functions Resolution depends on detector geometry Scatter of experimental efficiencies relative to 4" 2" reference detector: < 2% (in general!) 25

26 Light Yield and Resolution 0.08 Reference: Light yield of electrons: L e = E e MeV Specific light yield function for each detector: L p : exp. data from recoil protons L d : 2*L p (E d /2) L α : few. exp. data + educated guess L p /L (ref) -1 p L p for 2" x 2" detectors FOI GUL IPSN IRD NEU SCH UNH Higher energies: Influence of physical nonlinearity and PMT nonlinearity difficult to disentangle! Resolution is determined by detector geometry: E / MeV " x 2" NE213 detector photons neutrons A = 0.085, B = MeV 1/2 L L 2 = A 2 B + L A: light collection B: photo-electron statistics C: noise 2 2 C + L 10-2 L/L L / MeV 26

27 Unfolding Techniques TOF spectrometry only possible for pulsed beams: t 1-2 ns! Way out: solve inverse problem! N + ε = R Φ However: direct inversion does not work! Φ = R -1 N Suitable algorithms: Minimum χ 2 methods (FERDOR...) Non-linear iterative methods (GRAVEL) Maximum entropy methods (MAXED) exp. data detector response preinformation solution Existence? Uniqueness? Uncertainty? UMG unfolding package tailored to spectrum unfolding available from NEA more details: M. Matzke, Rad. Protection Dosimetry 107, 155 (2003) 27

28 TOF Unfolding counts per bin MeV T(d,n) Θ = exp. T(d,n) TARGET D(d,n) Φ E / (10 3 cm -2 MeV -1 ) MeV T(d,n) Θ = 98 exp. response calc. response 600 TOF TARGET TOF / ns E / MeV 120 counts per bin 15.6 MeV 10 4 T(d,n) Θ = 0 T(d,n) exp. TARGET D(d,n) Φ E / (10 3 cm -2 MeV -1 ) MeV T(d,n) Θ = 0 exp. response calc.response TOF TARGET TOF / ns E / MeV 28

29 TOF Unfolding events/bin α-emission from 12 C* E n = MeV exp. NRESP7 counts per bin 15.6 MeV 10 4 T(d,n) Θ = 0 T(d,n) exp. TARGET D(d,n) L / MeV TOF / ns Resolution: Unfolding better than TOF! Energy range: Exp. response matrix gives superior results for low-energy contaminations! Φ E / (10 3 cm -2 MeV -1 ) MeV T(d,n) Θ = 0 exp. response calc.response TOF TARGET E / MeV 29

30 Neutron JET (A.( Zimbal et al.) Setup at JET roof lab am NE213 detector NE213 (PTB) in µ metal cylinder : 5 cm x 10 cm 19 m 30

31 Experimetal Pulse Height Specta different heating scenarios (2002) MW NBI (6.0 s) 7 MW RF (1.0 s) MW NBI (4.5 s) Ohmic (42 s) N/(MeV s) E e /MeV 31

32 Unfolding using MAXED MW RF 4MW NBI Ohmic ϕ E (arbit. units) E n / MeV 32

33 Fast-Neutron Radiography (V.( Dangendorf et al.) FNRT in pulsed, wide energy neutron beam Pulsed deuteron beam Be target ~ 1 µs ~ 1 ns Deuteron pulses: 1,5 ns width 1-2 MHz rep.rate E N Pulsed neutron beam n γ t TOF m d = 2 t 2 N 2 TOF E n (t TOF ) Task: Neutron Transmission Imaging with Energy selection via TOF-measurement Neutron production and measurement: pulsed 2 µa pulsed deuteron beam hits Be target neutron yield: 5 x 10 5 s -1 cm -2 at 1-10 MeV energy energy selection via TOF measurement need for imaging system with fast timing capability 33

34 Resonance Imaging GEM-FANGAS: pulse-counting detector with PP radiator, multi-gem amplification and delay-line readout neutron energy : broad spectrum (2-10 MeV) acquisition time: 5.5 h 1200 c/pixel (matrix 300 x 300 pixel) 34

35 OTIFANTI 400 cm 2 BC 400 scintillator screen mirror Demonstation system: single ICCD camera, gated exposure with 10 ns 2 MHz repetition rate PM lens 25 mm gated intensifier Coupling lenses Cooled CCD camera 35

36 DX and DDX measurements (D.( Schmidt et al.) PTB TOF facility for measurement of neutron scattering cross section sample incident energy region (in MeV) points 16 O C D5 W CY nat Fe D4 nat Pb D3 Q nat Cr D2 P S T 51 V nat Ti D1 nat Si CO M 14 N nat Cu nat W m nat Nb ( 7-14 ) DX and DDX (emission spectra) for most nuclides 36

37 FNDA2006 Follow-up of the successful NEUDOS workshop (Pisa 2000) Broader coverage of topics! Agenda Fast neutron detectors Methods and facilities for the production of fast neutrons Simulation of detectors and fast neutron facilities Analysis techniques Signal processing and data acquisition Applications 2 nd circular in June/ July 2005 Pre-registrations still welcome! website: 37

38 Summary PTB offers access to well characterized neutron fields for applied research no user fees for research projects of mutual interest is open to share experience in detector development is interested in new activities, in particular in interrogation and security technologies Thank you for your attention! 38