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240,242 Pu( n,f ) measurement update

240,242 Pu( n,f ) measurement update. n_TOF Annual Collaboration Meeting CERN, November 28-30, 2012. Outline. Experimental R.I.Y. (“read-it-yourself”) Pu ( n,f ) run summary Event-search routine, RAW2DST conversion Analysis SF background Possible deterioration of detectors

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240,242 Pu( n,f ) measurement update

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  1. 240,242Pu(n,f) measurement update n_TOF Annual Collaboration Meeting CERN, November 28-30, 2012

  2. Outline • Experimental R.I.Y. (“read-it-yourself”) • Pu(n,f) run summary • Event-search routine, RAW2DST conversion • Analysis • SF background • Possible deterioration of detectors • Analysis of high-energy (>1MeV) data • Simulations (summary) • Summary, working plan 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  3. Samples • Eight (8) samples (4 x 240Pu, 4 x 242Pu) received from IRMM (Geel) • 3 cm diameter PuO2 deposit • 0.25 mm aluminium backing (5cm diameter) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  4. The Micromegas detector • MICRO-MEshGAseousStructure • Wireless gaseous detector • Drift electrode • Drift space (mm) • Primary ionisation and charge drift • Micromesh • Amplification region (25-50μm) • Charge multiplication • Readout • Already used for beam monitoring at n_TOF • 10B(n,α) and 235U(n,f) • Advantages • Low background (transparent detector) • Fast signal • Robustness, radiation hardness • Stability for long runs • Little material 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  5. The Micromegas chamber • Designed to hold up to 10 samplesand microbulkMicromegas detectors • BNC connections for signals and HV • Aluminium chamber • Kapton windows • Gas mixture • 88% Ar : 10% CF4 : 2% iso-C4H10 (isobutane) • p = 1 bar 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  6. Mounting the samples and detectors • Detectors mounted on the internal frame • Finally, the setup looks like this 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  7. Mounting the samples • A 235U sample (for reference) and an empty frame also mounted • Samples and connection arranged as shown 10 9 8 7 6 5 4 3 2 1 Vm CAEN multi-channel HV supply BEAM EMPTY Pu-240 Pu-242 U-235 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  8. Mounting the detector in the EAR • Micromegas chamber placed downstream from the TAC (@188.7m) • 16-channel preamplifier (10 channels used) • Constructed at INFN-Bari, based on FIC electronics • Electronic protection in place to prevent channel breakage (partially effective) neutrons neutrons 2011 2012 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  9. Preamplifier performance BEFORE AFTER New preamp from INFN-Bari tested recently with similar performance. 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  10. Pu(n,f) run summary • Data-taking has been completed! • During 2011 run: data acquisition in parallel with C6D6 (Ni-58, U-236) and TAC (U-236) measurements • During 2012 run: in parallel with C6D6(U-238, Zr-92-93, Mg-25), TAC (Sr-88) • Total protons: • 5.59 x 1018 + 7.89 x 10181.35 x 1019 protons • …before discarding setup runs etc. • Original proposal called for 8.0 x 1018 • However, the proposal was based on higher sample mass and assuming fission collimator setup • The measurement has been fully carried out in parallel mode 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  11. Analysis routine • In its previous form, the peak search routine could not discriminate overlapping pulses • The routine has been improved • Locates peaks looking for local maxima and minima 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  12. Amplitude spectra – Pu-242 En < 10MeV 0.1 MeV < En < 10 MeV 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  13. Amplitude spectra – U-235 En < 10MeV 0.1 MeV < En < 10 MeV 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  14. Amplitude spectra – Pu-240 En < 10MeV 0.1 MeV < En < 10 MeV • The behaviour of the Pu-240 has been investigated 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  15. Detector dismounting • The samples and detectors were recently removed from the chamber • An unexpected alteration of some detectors was observed • A distinct discoloration is visible in the 4 detectors used with the Pu-240 samples • Practically invisible in the other detectors • A displacement of one of the samples is deduced 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  16. Detector dismounting 3cm 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  17. Detector behaviour – Pu-240 En < 10MeV 0.1 MeV < En < 10 MeV • There seems to be a deterioration between the beginning of the 2011 run and the end of the 2012 run 2011 2012 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  18. Current analysis • Development of analysis software • Extracting cross sections using evaluated neutron fluence • General quality check • Timing issue reported at the last analysis meeting (determination of t0) has been resolved by correctly reading the PKUP signal • High-energy data analysis 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  19. Amplitude vs. En – Pu-242 55 40 45 40 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  20. Amplitude vs. En – U-235 20 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  21. 235U(n,f) & 242Pu(n,f) yields 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  22. Neutron fluence and beam interception factor • Beam interception factor from recent simulations • Evaluated neutron fluence for 2011(-12) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  23. U-235(n,f) cross section 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  24. Pu-242(n,f) cross section 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  25. Pu-242 spontaneous fission background En < 10MeV 0.1 MeV < En < 10 MeV 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  26. Pu-242 spontaneous fission background Spontaneous fission Pu-242(n,f) exp. cross section 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  27. Pu-242(n,f) to U-235(n,f) cross section ratio 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  28. High-energy analysis • “Compensation method” (previously used for analysis of FIC data by Marco, Francesca,…) • Baseline oscillation can be subtracted from adjacent detector • One step added in the data-processing flow • Matching structure of ROOT files created conventionally • Using the same analysis routines to extract the cross sections Cross section PEAK SEARCH Raw data DST files ROOT files ANALYSIS * RunNumber * EventNumb * PSpulse * PulseInte * FIMGdetn * FIMGsatfl * FIMGindex * FIMGtof Raw data ROOT files COMPENSATION • Conditions still need to be adapted to this measurement • γ-flash start • Event rejection • Several bugs have been resolved • Some random crashes still present, to be understood and resolved * Detn * Time * ampl * eve * PSPulse * prot 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  29. High-energy analysis BLUE = RED - BLACK Amplitude Time (ns) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  30. High-energy analysis BLUE = RED - BLACK Amplitude Time (ns) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  31. High-energy analysis BLUE = RED - BLACK Amplitude Time (ns) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  32. High-energy analysis BLUE = RED - BLACK Amplitude Time (ns) 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  33. High-energy analysis • Complete high-energy analysis software “chain” to be completed soon • Modifications already included • Corrected use of “timestamp” variable • Reading PS pulse type • Output to ROOT files only • Baseline calculation (from raw2dst routine) • Modifications to implement • Complete ROOT file creation to match standard output • Incorporate peak-search routine • Test and compare with conventional analysis • Energy overlap in the few MeV region • High-energy limit?  Probably different for 2011/2012 data 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  34. Simulations • Reproducing signals from α-particles and fission fragments • Simplified geometry of samples and active detector volume created in FLUKA • Energy deposition is scored event-by-event and transformed to charge • Electron drift velocity calculated for given gas mixture and drift voltage (GARFIELD) • We can thus calculate the current reaching the readout electrode and “pass” it through an appropriate circuit to reconstruct the signal • A large time window is selected in which we randomly add: • white noise • α-particle and fission fragment pulses (at appropriate rates) Gas V Sample dE/dz 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  35. Simulations: α-pile-up • How does α-pile-up (in Pu-240) affect the α-particle amplitude spectrum? • Comparison of the real amplitude distribution of simulated α-particles with the distribution extracted by the pulse analysis routine • A long tail at higher amplitudes appears! • The overall detection efficiency decreases 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  36. Summary – analysis “road-map” • Data taking has been completed! • Raw data analysis routine has been improved • Preliminary amplitude cuts have been selected • Analysis software has been written • U-235(n,f) and Pu-242(n,f) cross sections have been reproduced satisfactorily at a first approximation and 242/235 ratio • High-energy analysis chain to be finalised as described • Add statistics • Take samples from whole 2011-12 run • Discard useless runs • Beam-off runs studied • Behaviour of Pu-240 detectors has been investigated (continue) • Simulations • To be continued… 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

  37. The end 240,242Pu(n,f) measurement @ n_TOF n_TOF Annual Collaboration Meeting – CERN, November 28-30, 2012 | A.T.

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