1. Nuclear Physics Institute Řež Fast neutron generators at NPI Řež M. Majerle P. Bém J. Novák E. Šimečková M. Štefánik

2. Outline -Neutron generators -White neutron source (D 2 O, thick Be) -Quasi monoenergetic neutron source -Research programs -In development (pneu post, CANAM) -Cross-section validation on Co (part of the F4E) -Description of experiment -CS extraction procedure -Uncertainties -Time-Of-Flight measurements of the neutron spectrum from our neutron generators

3. NPI cyclotron facility ■ isotope production and ■ neutron irradiation experiments (Li(C) and D 2 O, Be targets) well defined beams protons 6-25 MeV (3 μA) deuterons 12-20 MeV (3 μA) he-ions 18-55 MeV (1 μA) U-120 (1960) upgrade ■ to isochronnous regime (1975) ■ to alternative operation in +/- mode high-power beams protons 6-38 MeV (50-30 μA) deuterons 11-20 MeV (35-20 μA)

4. ACTIVATION WITH NEUTRONS: p+D 2 O source – IFMIF-like spectrum Target Specification: Neutron flux up to 5x10 10 n/cm 2/ s and energy extending to 32 MeV provide suitable tool for validation of IFMIF-relevant activation XS □ protons accelerated to 20-38 MeV (p+D 2 0) □ high proton beam power (800W for 37 MeV, ca 20  A) □ complicated cooling, PC controlled □ target cell: 30 mm in diameter and 16 mm of length equipped by 40 μm thick entrance Ta foil (0.5 MeV thickness for the 37 MeV protons) ■ Neutron energy (MeV) N eutron yield (n/ μA/sr /MeV ) 10 10 9 10 8 10 7 10 6 510 0 1520 p(37MeV)+D 2 O p(19MeV)+Be [Brede, PTB] p(24MeV)+D 2 O 2530 20 O 0O0O 40 O 0O0O 0O0O

5. ■ present neutron source for activation experiments is a copy of CYRIC (Tohoku Univ.): □ QME neutrons in the energy range 18-36 MeV are produced in standard 7 Li(p,n) reaction using □ irradiation of static 2mm 7 Li target followed by beam stopper (8mm thick C disk) NPI quasi-monoenergetic p+Li(C) neutron source The target station of NPI p-Li source Li foil position target chamber („dog box“) ■ the neutron flux up to 6 10 8 n/cm 2 /s in QME peak is operated for 38 MeV /6 μA proton beam and for minimal target-to-sample distance of 48 mm

6. Experimental program Close cooperation with KIT, Culham, MPI Munchen White spectrum: –Study of IFMIF-like spectrum from p, 3 He+D 2 O reactions –Dosimetry foil method to determine the neutron spectrum –Validation of neutron transport CS on Fe –Integral validation of neutron CS on CuCrZn alloy, EUROFER steel, W, Ta –Electronic hardness tests for CERN End-cup calorimeter (cooperation with MPI Munchen) QM neutrons: –CS in 20-35 MeV range on Al,Au,Bi,Co,Nb –ERINDA program (2 tasks: SCD – IRMM, Y CS – SWIERK) –RADMON testing Future irradiation program: –Gas production CS in EUROFER steel (F4E) –IRDFF benchmark (IAEA F41031)

7. Be target, Pneumatic post for activation Thick Be target – functional; licensing, analysis of spectrum in process First tests: Pneumatic post - proof of concept experiment performed: –10 sec delivery time –Plastic rabbit ok Planned for: –F4E - gas production CS for EUROFER components – 90m Nb, 89 Y (15-20 sec) not measured in our Nb and Y campains Thick Be target for white neutron spectrum

8. Webpage: canam.ujf.cas.cz

9. Cross-section validation on Co F4E-GRT-056, Task 4.2 (Nb and Co), KIT/NPI joint task Motivation: Exfor data mostly end at 20 MeV IRDF2002 evaluation up to 20 MeV, few reactions EAF is mainly not validated above 20 MeV

10. Protons with energies 20, 25, 27.5, 30, 32.5, 35, 37.5 MeV ca. 20 hours @ 5  A 0.5 As on target ~ samples irradiated with ca. 10 13 neutrons HPGe analysis and reaction rates extraction Neutron spectra for different proton energies. Validation of MCNPX with TOF measured at CYRIC

11. Extraction procedure – step1 Production from peak and from background ! Modified SAND-II code: –Input CS and n spectra –Calculate RR=integral(CS*n_spec), compare to exp. –Modify CS (with weights based on…) –Iterate until expRR=calRR Input: –CS from EAF-2010, processed in 0.25 MeV bins with PREPRO, according channels summed –n spectra with 0.25 MeV bins (from MCNPX and CYRIC)

12. Results

13. Final results More results available in final report of Task 4.2, F4E-GRT-056, free distribution Numerical data are in EXFOR, but not exactly from this report…

14. Uncertainty analysis – reaction rates HPGe spectra peak fitting (2%), MCNPX simulations < 0.5% - statistical gamma intensities (1%, differences LUND vs. ENSDF) efficiency calibration (2%) FWHM, profile and displacement of the proton beam – negligible Sample displacement 1-2% Neutron shielding by samples 0.5% @ 48 mm, 2-3% @ 87 mm Li thickness 5% (new Li for each measurement) Current measurement 5%

15. Uncertainty analysis – cross-sections Extraction procedure - SAND-II in this case; another method, but similar results -> choice of procedure not so important Differences in neutron spectra (CYRIC, MCNPX) Low energy tail Differences ~ uncertainties (up to 30%) R Nolte et al., NIM A 476 (2002) 369–373 Solution - the subtraction of the low energy tail ? Standard angles ?

16. RR to CS - method2 CS defined at n points (center of QM peak), linear interpolation Calc. RR = sum(CS*spectra) Minimization of the: sum(exp.RR-calc.RR)^2 This method works ! Not yet clear: point exactly at center ? linear interpolation, curve.. “recommended by IAEA” ? Example with 59 Co(n,3n) 57 Co, “exp.RR” were calculated, input and output values are the same 197 Au(n,2n) 196 Au from exp. RR

17. TOF measurement cyclotron neutron generator p+p+ n,  TOF base (max ca. 4.5 m) ZT4211-01 PCI 8bit 500 MHz (=2ns) 2 channels continuous acquisition up to 256MS RF antenna NE213

18. Pulse time structure Duty cycle 5-80%, (frequency 100-150 Hz) Several bunches of protons at different cyclotron orbits, exiting with RF frequency (20-30 MHz) Neutron pulses Time RF signal 0.6ms Detector response

19. Pulses timescale in detail Micropulse duration is ca 50 ns. Pulses from NE213 scintillator (50  ) are 10-20 ns long. 1000-4000 pulses from scintillator per macropulse. The idea is to record the time of all pulses and to put it in the histogram – this should give some TOF structure. Start of macropulse Micropulse duration 50 ns. 2  s Time Detector response

20. Analysis – fit function, n/  Fit function: convolution(A*exp(-at)+B*exp(-bt),gauss(s)), a=5ns,b=50ns,s=3ns Separation of n/  is determined with the ratio A/B Amplitude = surface under curve = A/2a+B/2b Output: time, A, B, chi^2 Time [ns]

21. Separation of n/  For PuBe input range 2V, for p+Li 5V, at higher energies we need 10V 8 bit ADC is not enough! On the other hand 200 MHz might be enough PuBe P+Li@27MeV Amplitude [rel units] Ratio A/B F. Belli et al. SOFT2012 poster

22. Time of flight (thick Be) p+Be reaction – no intense  peak (can be seen with n/  separation)  peak used for calibration of TOF Vertical sections = scintillator response P+Be@20MeV Amplitude [rel units] TOF [ns] Simulation of p+Be@20MeV

23. Conversion to MeVee Rel unit to MeVee – calibration by 4.43 MeV PuBe Scintillator responses for the adjustment of SCINFUL-R predictions Deconvolution of neutron spectra P+Li@27MeV Amplitude [rel units] Ratio A/B Scintillator response to monoenergetic peak ca. 25 MeV neutrons

24. p+Li(C)@33MeV neutron spectrum acquired by TOF method Neutron energy [MeV[ Experiment MCNPX simulation, reconstruction energy->time->energy With frame overlap

25. p+Li(C)@33MeV neutron spectrum acquired by TOF method Neutron energy [MeV[ Experiment MCNPX simulation, reconstruction energy->time->energy Without frame overlap – energy threshold Not really identical.. need more work.

26. Thank you !