1 / 33

240,242 Pu( n,f ) measurement @ n_TOF

240,242 Pu( n,f ) measurement @ n_TOF. A. Tsinganis (CERN/NTUA) , E. Berthoumieux (CEA Saclay ), M. Calviani (CERN), V. Vlachoudis (CERN). n_TOF Annual Collaboration Meeting Lisbon, December 13-15, 2011. Outline. PART I Samples & detector Samples The Micromegas chamber

sydney
Download Presentation

240,242 Pu( n,f ) measurement @ n_TOF

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 240,242Pu(n,f) measurement @ n_TOF A. Tsinganis (CERN/NTUA), E. Berthoumieux (CEA Saclay), M. Calviani (CERN), V. Vlachoudis (CERN) n_TOF Annual Collaboration Meeting Lisbon, December 13-15, 2011

  2. Outline • PART I • Samples & detector • Samples • The Micromegas chamber • Mounting the samples • Mounting the chamber in the EAR • PART II • Data and analysis • Data • Preliminary analysis • Part III • Simulations • Technique • Results • End goals • Conclusions / To do 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  3. Introduction • An (n,f) measurement on 240,242Pu… • …using a Micromegas detector (FIMG – FIssionMicromeGas) • Proposal CERN-INTC-2010-042 / INTC-P-280 (21/05/2010) • http://cdsweb.cern.ch/record/1266869/files/INTC-P-280.pdf 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  4. PART I :Samples & detector

  5. Samples • Eight (8) samples (4 x 240Pu, 4 x 242Pu) received from IRMM (Geel) • 3 cm diameter • Chemical form: PuO2(plutonium oxide) • 0.25 mm aluminium backing (5cm diameter) • Mass • ~ 3.5 mg (Pu-240, 99.89%) • ~ 3.0 mg (Pu-242, 99.97%) • Surface density 0.10-0.13 mg/cm2 • Total mass is lower than included in proposal • Activity • 27.3 MBq (Pu-240) • 1.2 MBq (Pu-242) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  6. The Micromegas chamber • Designed to hold up to 10 samplesand microbulkMicromegas detectors • …although with some difficulty • BNC connections for signals and HV • Aluminium chamber • Kapton windows • Gas • 88% Ar • 10% CF4 • 2% iso-C4H10 (isobutane) • 1 bar 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  7. Mounting the samples • Mounting carried out in ISOLDE lab under strict RP supervision • Samples placed in appropriate holders for mounting 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  8. Mounting the samples and detectors • Detectors mounted similarly on the internal frame • Finally, the setup looks like this 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  9. Mounting the samples • A 235U sample (for reference) and an empty frame also mounted • Samples and connection arranged as shown Vd2 = 400V 10 9 8 7 6 5 4 3 2 1 Conventional HV supply Vd1 = 400V BEAM CAEN multi-channel HV supply EMPTY Pu-240 Pu-242 U-235 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  10. Mounting the detector in the EAR • FIMG chamber placed downstream of the TAC 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  11. Mounting the detector in the EAR • 16-channel preamplifier • Constructed at INFN-Bari, based on FIC electronics • Electronic protection in place to prevent channel breakage (quite effective, short of 100%) • A second module is available (we have 2 broken channels) • Shielding of pre-amp necessary to reduce γ-flash oscillations • Also HV filters replaced with better shielded ones (provided by E. Griesmeyer) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  12. PART II :Data & analysis

  13. Data • Sample signals • Baseline oscillation after γ-flash (down to a few MeV) • Obvious difference in α-activity α FF Pu-242 Pu-240 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  14. Baseline oscillations - grounding • EAR-1 grounding 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  15. Data • Data acquisition in parallel with C6D6 (Ni-58, U-236) and TAC (U-236) measurements • Removed for U-238 TAC measurement • Total protons: • ~ 5 x 1018 (beginning of July – mid-September) • Still short of proposed 8.0 x 1018 • Furthermore, the proposal was based on higher mass and assuming fission collimator setup • Size of data is considerable • Lengthy retrieval, ROOT-file creation and processing times! • Quota issues on lxplus 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  16. Preliminary analysis • The high α-activity of the 240Pu samples makes the pulse recognition routine unworkable in its present form • Routine to be adapted to tackle the problem • The preliminary analysis has thus focused on the 235U reference sample (high counting rate) and 242Pu • The analysis routine for the Diamond detector data (developed by Carlos & Christina) has been used to create the DST files • Retrieval of data very slow due to size of files • ROOT files have been created for only a limited part of acquired data (10% of 2011 statistics) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  17. Preliminary analysis • Artefacts due to γ-flash oscillations U-235 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  18. Preliminary analysis • Artefacts due to γ-flash oscillations 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  19. Preliminary analysis • Artefacts due to γ-flash oscillations 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  20. Preliminary analysis • Amplitude spectrum – alpha/FF separation U-235 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  21. Preliminary analysis • U-235 resonances 1-10eV • Compared with ENDF VII

  22. Preliminary analysis • Pu-242 at threshold • Compared with ENDF VII ~10% of 2011 statistics 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  23. PART II :Simulations

  24. Simulations • FLUKA simulations • Attempt to reproduce signals from α-particles and fission fragments • α-particles and fission fragments studied separately • Initial position sampled randomly within the sample volume • Particles emitted isotropically within 2π solid angle • Alpha-particles • Energy: 5.2MeV • Fission fragments • Mass and energy systematics from G.D.Adeev et al., Preprint INR 861/93 1993 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  25. Simulations • Simplified geometry created in FLUKA • Simulation of samples and active detector volume • Energy deposition along z-axis is scored event-by-event • From energy deposition to charge (~26eV / electron-ion pair) Gas Sample dE/dz 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  26. Simulations • Electron drift velocity calculated for given gas mixture and drift voltage • …using GARFIELD 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  27. Simulations • Simplified geometry created in FLUKA • Simulation of samples and active detector volume • Energy deposition along z-axis is scored event-by-event • From energy deposition to charge (~26eV / electron-ion pair) • Electron drift velocity calculated for given gas mixture and drift voltage • …using GARFIELD • …we can thus calculate the current reaching the readout electrode • This signal is passed through a CR-RC circuit to obtain the final pulse • Typical amplifiers use a CR-(RC)4 circuit to achieve a quasi-gaussian pulse shape Gas V Sample dE/dz 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  28. Simulations: data reconstruction • A large time window is selected in which we randomly add: • White noise • α-particle and fission fragment pulses • …at appropriate rates 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  29. Simulations: data reconstruction • Total (mixed) signal: 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  30. Simulations: data reconstruction • Each component is known… 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  31. Simulations: data reconstruction • …we can therefore apply the pulse recognition routine used for the experimental data and attempt to reconstruct an amplitude spectrum Counts α-particles The quality of the α – FF separation can then be estimated Amplitude cut Fission fragments Noise Amplitude 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  32. Conclusions • To do: • Fix analysis routine to address: • γ-flash oscillation • α-activity in 240Pu • Carry on with data processing and analysis (obviously) • Finalise simulations • Create realistic signals for different count rates • Pulse recognition routine • Study α – FF separation • Compare with experimental amplitude spectrum • Study pile-up probability • Detector efficiency • Once simulations are in place, the same technique can be used for the fission tagging measurements • FIMG chamber with Pu samples presently stored by RP in view of the 2012 run • Accumulate as much statistics as possible within 2012 planning • Actions during winter shutdown • Address grounding issues in EAR-1 (general action) • Investigate shielding improvement of pre-amp box 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

  33. The end 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – Lisbon, December 13-15, 2011 | A.T.

More Related