b-neutron detector meeting at LPC-Caen





List of participants:


After a brief introduction, N. Orr presented the goals of the meeting, which he identified as:

It was also noted in presenting these goals that although it would be not explicitly discussed at the meeting, the array would have the characteristics necessary for direct reaction experiments such as (d,n) and (p,n).

The talks that followed (see agenda) and associated discussions brought to light a number of points:

Beta-delayed neutron detection arrays for GANIL/SPIRAL-2 and DESPEC should have, as outlined at the Madrid meeting by N. Orr, the following characteristics (presentations by N. Orr and D. Cano-Ott):

A detector with such characteristics would clearly improve the quality of the experimental data and make certain experiments, such as those requiring multi-neutron detection, possible. This was illustrated with the example of an attempt to measure the 11Li -2n decay using the TONNERRE array (presentation by M. Marqués).

An array of consisting of ~100 to 200 NE213 liquid scintillator modules of ~5cm depth placed at distances on the order of 5 m from the source seems to be a realistic starting point for a possible baseline design to fulfill the needs enumerated earlier. Very promising developments of the NEUTROMANIA project (presentation by Franck Delaunay) were shown: a new solid scintillator developed in Strasbourg demonstrates good n/gamma discrimination capabilities. The R&D of the NEUTROMANIA project requires further funding (a request is currently being submitted to the French ANR) and may if all goes well lead to a prototype detector module being built in two-three years from now.

Digital electronics appear to be the solution of choice for the data taking. Flash ADCs with 12 bit precision and not less than 500 MHz sampling rates should be considered for the pulse-shape analysis. Furthermore, the goal is to reach a 10 keV (electron equivalent energy) threshold in the detectors. The FASTER system, underdevelopment at LPC- Caen, was described (David Etasse) and represents a promising way of allowing pulse- shape analysis at high rates and with large data-transfer rates. Two scenarios are being considered:

In addition, the development of a digital CFD to furnish the Time-of-flight information will also be undertaken within the next 18-24 months.

Various results of the work done by the DESPEC working group, including a fast pulse shape analysis routine for NE213 detectors were presented (D. Cano-Ott).

The design of such a detector will require Monte Carlo simulations and GEANT4 seems to be the most appropriate tool (presentation by B. Roeder). However, the neutron physics –both models and tabulated cross sections– needs to be improved significantly in order to allow reliable and accurate simulations to be undertaken (B. Roeder and D. Cano-Ott). In a more general context the DESPEC community (work by J.L. Taín, IFIC Valencia) has developed a realistic event generator which generates correlated particles: delayed -rays and neutrons.

In order to facilitate the use of GEANT4, a Monte Carlo simulation school will be organized by CIEMAT and IFIC if sufficient people are interested in participating. The tentative dates for the school are the 10-11 April in Madrid (contact daniel.cano@ciemat.es).

At present, it is envisaged by the French groups that the next 18-24 months will be devoted to simulating and studying various possibilities for a new array (including test and proof of principle measurements). A decision as to whether to proceed to a fully blown proposal and request for funding would then be taken in late 2008-early 2009. The schedule for the DESPEC array is more immediate. The construction of such an array has already been decided upon and a significant large fraction of the array (the exact extent depends on the funding) should be operational in 2010 for the startup of the experimental programmes with DESPEC.

Synergies between GANIL/SPIRAL-2 and DESPEC activities were discussed. From a practical point of view, the following activities could run in parallel:

The possibility of having a common cell design for both the GANIL/SPIRAL-2 and DESPEC array should be investigated as the needs of the experiments planned at the two facilities are very similar.

A few carefully selected source and neutron-beam measurements and a realistic test experiment should be performed as soon as possible (ideally this year) in order to characterize detector properties. In this context a number of issues were raised:

X. Ledoux (Bruyére-le-Chatel) offered the possibility of performing neutron irradiations and digital electronics tests using the neutron beams available from the BLC Van de Graaff facility.

A discussion of the levels of interest and possible contributions of each laboratory represented at the meeting was undertaken. At present it appears that apart from LPC and the DESPEC collaboration, only SUBATECH and IFIN-Bucharest are interested in becoming engaged in the design and construction of a new array. IPN-Orsay and GANIL would eventually be interested in using such a detector but not in its construction. As noted above, Bruyères-le-Châtel would be able to offer their services in the eventual testing of detector modules with their neutron beams, whilst the physics group (J.M. Daugas et al.) may be interested in utilising the detector once constructed.

Finally a brief letter from M. Lewitowicz regarding possible participation in a proposal to support SPIRAL2@GANIL within FP7 was discussed. It was concluded that the information provided by GANIL was far too sketchy to make any decision at this stage. Florian Negoita was scheduled to have a meeting with M. Lewitowicz concerning this proposal and the implication of IFIN-Bucharest. He would raise the issue with him.


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