Seite 1. The photoneutron source nelbe at HZDR

Transcription

1 Seite 1 The photoneutron source nelbe at HZDR

2 Helmholtz-Zentrum Dresden-Rossendorf Radiation physics High field laboratory ELBE accelerator Ion beam physics Radiochemistry Radiopharmacy Nuclear safety research Helmholtz Research Programme: Matter Health Energy Public funded national research laboratory 800 employees, federal+state budget: 61 M EUR Seite 2

3 ELBE: Electron Linear accelerator with high Brilliance and low Emittance DT generator E e 40 MeV I e 1 ma Micropulse duration t < 10 ps f = 13 MHz / 2 n nelbe photoneutron source nelbe is the only photoneutron source at a superconducting cw-linear accelerator HZDR invites external groups for experiments at ELBE Seite 3

4 nelbe photoneutron source nelbe neutron beam ELBE electron beam Seite 4

5 nelbe at ELBE : something special superconducting electron accelerator cw operation with variable micropulse repetition rate micropulse charge 80 pc (thermionic Injector) micropulse length t < 10 ps precise definition of time of flight For time of flight measurements the repetition rate is adjustable 13 MHz / 2 n, n = 0,,10 Very high repetition rate (200 khz), low instantaneous neutron-flux background of photon flash from bremsstrahlung is reduced since Januar 2010 : SRF Laser-Injector development bunch charge up to 1 nc (not yet reached) fligh path m neutron flux on target sample cm -2 s -1 neutron energy range (Liquid lead target, without moderator ) 100 kev < E n < 10 MeV energy resolution E/E < 1 % with 6.0 m flight path Seite 5

6 nelbe neutron spectrum October : neutron source strength: 1.4*10 11 n/s neutrons on target: 4.5*10 4 n/(cm 2 s) <I e- > = 19 A Max. thermionic injector at 200 khz rate November 2007 Fission chamber as primary beam monitor ( from PTB, Braunschweig) Spectrum is very similar to fast neutron spectrum e.g. 235 U(n,f) (ENDF-VII) Seite 6

7 National Center for High-Power Radiation sources 80 m 30 m NEW nelbe NEW LCBS NEW PW-Laser National Center for High-Power Radiation Sources X-ray source using Laser-Compton-Backscattering High-Power Laser (PW) for Ion Acceleration ground breaking started April 2010 New Neutron Time-of-Flight Facility for Transmutation Studies Autumn 2012 Seite 7

8 New neutron time of flight facility photoneutron source with liquid lead loop Parallel operation with Laser Experiments more beam time For nuclear data measurements Large neutron time of flight hall Length 9 m Distance from neutron beam line to surrounding concrete 3 m in all directions Seite 8

9 The new nelbe neutron time of flight facility Time of flight hall Data acquisition room 6 m? 6 m 9 m Seite 9

10 nelbe research program: Investigation of fast neutron induced reactions of relevance for nuclear transmutation and improvement of nuclear safety. 1. Inelastic neutron scattering (n,n ) 56 Fe, Mo, Pb, 23 Na and total neutron cross sections tot (Ta, Au, Al, C, H) 2. Investigation of minor actinides (radioactive targets) Collaboration with n-tof at CERN Joint research project Nuclear physics data of relevance for transmutation (German Federal Ministry for Science and Technology funded, 02NUK13) Neutron induced fission cross section of 235,238 U, 239,242 Pu Seite 10

11 Transmutationsrelevante kernphysikalische Untersuchungen langlebiger Aktinide Joint project for maintenance of compentencies in nuclear safety- and radiation research: Production and use of fast neutrons to investigate inelastic neutron scattering and fission of minor actinides MeV Gamma-Spectroscopy and development of high-resolution detectors (Comptoncamera) Production and use of thin actinide targets Seminars for young scientist involved PTB Braunschweig May 2010 Experimental Systems und Methods der Transmutation research Cologne, March 2011 Theoretical Concepts of nuclear reactions in heavy nuclei Munich, July th Advanced school in radiation detection and measurements Mainz, May 2012 Nuclear Chemistry of the Actinides Seite 11

12 Electrochemical deposition - Molecular Plating (MP) Deposition Deposition from from organic organic media media as as a molecule molecule (nitrate (nitrate oxide) oxide) Solvent: Solvent: isopropanol isopropanol or or isobutanol isobutanol Deposition Deposition time: time: h h Current Current density: density: ma/cm ma/cm 2 2 Voltage: Voltage: V V Chemical Chemical purification purification prior prior to to deposition deposition possible possible Recovery Recovery and and chemical chemical purification purification of of used used target target material material ( 248 ( 248 Cm: Cm: > > $/mg) $/mg) Small Small and and simple simple set-up set-up Components Components easy easy to to replace replace in in order order to to avoid avoid cross-contamination cm Rh-wire (anode) PEEK-funnel Organic solution Backing (Be, Ti, Al) Titanium block (cathode) Seite 12 Deposition yield: up up to to 90% 90% Target thickness: mg/cm 2 2 possible Water cooling

13 Radiographic Image of a nat U sample 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 0,9-1 0,8-0,9 0,7-0,8 0,6-0,7 0,5-0,6 0,4-0,5 0,3-0,4 0,2-0,3 0,1-0,2 0-0,1 Backing: polished Ti 250 m Surface area: 43 cm 2 Areal density g/cm 2 Also usage of Ti coated Si-wafers to reduce surface roughness: Nd deposits Seite 13 Courtesy: A. Vascon, K. Eberhardt, Johannes-Gutenberg Universität Mainz

14 Summary and outlook nelbe is intended to deliver data on fast neutron induced reactions the ELBE electron beam delivers a high neutron flux with very good time structure different kinds of experiments can be done: inelastic scattering using a double time of flight setup: Fe-56 and Na-23 neutron transmission: Al, Ta, Pb elastic scattering: D(n,n)D fission: U, Am, Np, Pu Future planned improvements: LaBr 3 detectors instead of BaF 2 better photon energy resolution new bigger experimental area within extension of ELBE facility Seite 14

15 Nuclear Transmutation Project Roland Beyer, Evert Birgersson, Anna Ferrari, Roland Hannaske, Mathias Kempe, Toni Kögler, Michele Marta, Ralf Massarczyk, Andrija Matic, Georg Schramm Arnd Junghans, Daniel Bemmerer, Eckart Grosse*, Klaus-Dieter Schilling, Ronald Schwengner, Andreas Wagner Development of the nelbe photoneutron source together with the Institut für Sicherheitsforschung, Frank-Peter Weiss and also with IKTP, TU Dresden, Hartwig Freiesleben, Klaus Seidel through a DFG project. * ( also at IKTP Dresden) Seite 15

16 Seite 16 Thank you for your attention

17 Production and use of thin actinide targets Production of thin homogeneous isotopically pure actinide layers by Klaus Eberhardt, Alessio Vascon, Johannes Gutenberg Universität Mainz Molecular plating technique: Deposition from organic media as a molecule (nitrate oxide) Surface characterisation by scanning microscopy (SEM, AFM,...) Calibration of a beam monitor: 235 U Fission chamber with PTB Measurements on photodisintegration of 239 Pu at ELBE Neutron-induced fission cross section of 242 Pu at nelbe Storage and Handling at HZDR Radiochemical Laboratories Dedicated glove box for handling actinide targets built. Fission chamber development ongoing Development of fast preamplifier readout electronics Seite 17

18 Seite 18 Measurements of photon production cross section

19 Seite 19 Measurements of photon production cross section with target without target

20 ELBE: Electron Linear accelerator with high Brilliance and low Emittance DT generator E e 40 MeV I e 1 ma Micropulse duration t < 10 ps f = 13 MHz / 2 n nelbe photoneutron source HZDR invites external groups for experiments at ELBE Seite 20

21 nelbe photoneutron target Electron beam power up to 40 kw power density in the neutron radiator up to 25 kw/cm 3 liquid lead circuit for heat transport Seite 21

22 Neutron time of flight spectrum with fission chamber Measured with PTB 235 U fission chamber n t = 5 mg/cm 2 Photofission: t(fwhm) = 4 ns Seite 22 low thermal neutron background J Cd /J < 8*10-5 from comparison with/without Cd absorber

23 nelbe double ToF detector setup BaF 2 array for gamma detection (42 crystals, 20 cm, Ø 5.3 cm) neutron beam flight paths: source - sample: 600 cm sample - BaF 2 : 30 cm sample - plastics: 100 cm PTB 235 U fission chamber for neutron flux determination sample: nat Fe (99.8%) % 56 Fe mass: g g 56 Fe 4 plastic scintillators for neutron detection (1 m, 11 x 42 mm 2 ) Background from elastic scattering to BaF 2 and subsequent inelastic scattering Improve shielding and geometry of BaF 2 detectors Seite 23

24 Improved double time of flight geometry and shielding Plastics BaF 2 -Setup borated polyethylene block between BaF 2 and plastics combination of two single sided readout 20 cm long crystals to one double sided readout 40 cm long detector number of random events reduced by one order of magnitude angular coverage: - n = = = +/- ( ) Seite 24

25 Experimental methods and results Inelastic scattering e n neutron source 56 Fe(n, n' ) 56 Fe 56 Fe n * Fe n' * Fe 56 Fe γ absorber with sample (78 h live time) fission chamber sample γ n neutron detectors γ detectors Seite 25

26 Total neutron cross section of Tantalum Transmission measurement T N N 0 exp( tot n t) Target: nat Ta 3.52 cm Bremsstrahlungabsorber: nat Pb 3 cm Counting cycle*: 80% target in 20% target out t Target ladder: Pb absorber Ta sample Measurement time 48 hours live time - target in 92% (2 khz) live time target out 80% (7 khz) measured with scalers * Y. Danon, NIM A 485 (2002) 585 Plastic scintillator with low detection threshold NIMA 575 (2007) 449 Flight path: 6.52 m Repetition rate: 100 khz Seite 26

27 Total neutron cross section of nat Ta E n - stat / -- E n /E n 0.2 MeV 5 % - 0.6% 2 MeV 1.2 % - 0.8% 7 MeV 2.3 % - 1.0% Seite 27