(Minutes taken by Ch. Schmitt)
A.Maj, D.Jenkins, O.Dorvaux, J.P.Wieleczko, P.Napiorkowski, O.Stézowski, S.Courtin, D.Lebhertz, W.Korten, Ch.Schmitt, K.Mazurek, M.Kmiecik, J.Styczen, A. Czermak, F.Azaiez, B.Fornal, E.Gamelin, M.Rousseau, C.Fink, V.Nanal, J.Pouthas, N.Alamanos, Z.Dombradi, S.Erturk A.Lemasson, G. de Angelis, J.J. Valiente-Dobon, to be completed
Design and Simulations
Points which have been emphasized :
· presentation by O.Stézowski :
- To compare the performances of different geometries, the various “Simulations” groups shall adopt a common reference, proposed to be the ideal spherical configuration.
- In order to account for the volume inherent to a given geometry, the calculated performances should be normalized to a common volume of LaBr3.
- Crucial need of more simulations with photon multiplicities Mg > 1.
- Focus on spherical geometry with tapered LaBr3’s.
- The add-back procedure has to be tuned in connection with the “wrong summing tail” that is found to depend on the energy of the high-energy photon as well as on the multiplicity of accompanying low-energy g‘s.
à constraint on granularity
- comment : look at two-dimensional spectra such as e.g. Einner vs. Eouter to infer most suited add-back algorithm.
· presentation by D.Jenkins :
- Discussion on cubic geometry and PSD tests
- Conclusion: never as good as for a spherical configuration, but more economical and versatile.
· discussion :
- Decision on the final design configuration to be taken within one year if possible
à Intense simulations still required, more realistic (including dead layers, etc)
- Problem of different ways of analysing the results given by the simulation : e.g. considering either energy distribution or efficiency (the former might be more intuitive)
à Need of finding a common working procedure and methodology (cf. above)
- Decide on the maximum (v/c) to be considered, what strongly constrains the design.
- PARIS is planed to be coupled with many other ancillary detectors: do not forget these additional constrains.
- Optical photons: according to the few people in the audience who already tackled this point, including the influence of the optical photons might dramatically affect the result.
à Look at the work done by the “Neutron detection” community
- Response of the crystal to optical photons depends on its shape, position, etc
- Influence of neutrons not yet included in any simulation so far.
Continuation of the PARIS Open Meeting on January 28th 2009
Detector testing
- Neutron-g discrimination unsuccessful by PSA (~ 2ns rise time) with a 1.5”´1.5” LaBr3 detector (LaBr3 does not have a strong slow component as e.g. BaF2 has)
- Comment : The study having been done with a AmBe source i.e. mean neutron energies of (2-3)MeV, look at the outcome in terms of discrimination with faster neutrons.
- Neutron-g discrimination for sure possible by the time-of-flight provided the Tof resolution does not exceed a few hundreds of ps (for 20 cm flight path)
- LaBr3 vs. LaCl3 regarding n-g discrimination has to be looked at.
- Resolution measurements:
resolution found linear as function of ÖEg up to ~ 12MeV;
- APD characterization with a blue LED:
à Many detailed and interesting results has been shown of the HV and T response of the APD with LED. A detailed report with all the obtained results should be written in order to allow comments and conclusions to be drawn.
- Perspectives of the detector tests:
à New preamplifier (very stable)
à Work on n-g discrimination by PSA and/or Tof with digital electronics
à Test different LaBr3 sizes and a LaCl3 with CsI’s (constrained by date of delivery)
· discussion :
- The question is raised about the working conditions of PARIS, namely PMT’s do not work in magnetic fields (as e.g. would be the case at the intermediate focal plane of S3.
à A response should be brought soon on that issue by a dedicated small working group.
Concluding discussion
- Cubic LaBr3 detectors well suited for a cubic-like PARIS configuration, while tapered detectors are mandatory for the spherical geometry (otherwise sizeable loss of efficiency).
à Problem of manufacturing tapered detectors to be discussed with St Gobain by J.Pouthas.
- Several aspects in favour of a PARIS inner radius around 23 cm (namely for versatility, coupling with AGATA and Tof resolution).
- Question raised about first beam time at S3 (see minutes of the management board)
- Question raised by Z.Dombradi and F.Azaiez on the possibility of position sensitivity
(this would be discussed in near future with more concrete proposals)