Fast neutron detection and their energy measurement is complex, because neutrons are electrically neutral particles, so they can’t be detected directly.

Mimac-FastN is a tight enclosure filled with a neutral gas at roughly the atmospheric pressure, with non-flammable and not regulated matters (so no 3He, no high pressure, no hydrogen, that limit operation in some industrial areas).

Neutrons can interact with the detector gas nucleii. This interaction results in a nuclear recoil : there is a partial energy transfer from the incident neutron to the gas nucleus.

The detector has a very fast sampling camera (40 MHz). Thanks to this camera, the detector provides 3D pictures of the nuclear recoils’ tracks in the gas.

At the same time, the energy deposited in ionization by the nuclear recoil in the gas is measured.

From these two information, tracks and ionization energy, we can calculate the energy of the incident neutron.

Hereafter a drawing of the detection principle :


Developments of Mimac-FastN result from 15 years of gaseous detectors know-how. Some specificities are listed below :

1/ A low noise and fast electronics, that opens the 3D detection field with a good resolution.

2/ The acquisition software, that controls physical events triggers.

3/ The ability of reconstructing the nuclear recoils kinetic energy from the measurement of their ionization energy. This reconstruction is specific to each gazeous mixture, and evolves with ionization energy. The higher the neutron energy is, the higher is the impact of this parameter on the kinetic energy calculation of the incident neutron.

4/ The data analysis software, that allows the selection of the events to consider for the neutron spectrum reconstruction or for the neutron source location.

Mimac-FastN differentiates from existing technologies with its performance that is not limited to neutron counting but also allows their energy measurement, with its mobility, with the 3D approach that gives access to the discrimination of all the physical contributions, and with its directionnal feature.

The proof of concept has been conducted in monoenergetic neutron fields, with a small mobile prototype, with data acquisitions of 1 hour.

Use cases are currently explored, for applications as diverse as detection of fissile matter in radioactive waste, characterization of atmospheric neutrons, or neutron dose measurements in industrial areas using neutron sources.

Reference : Article published in the NIM journal :

Nadine Sauzet : Scientific & technical responsible, simulations & data analysis

Olivier Guillaudin : Detector developments, micromegas & drift field cage

Marc Marton : 3D design, production & assembly


  • Design, realization of a 10 bar spherical gaseous detector
  • Coupling of the spherical detector to the COMIMAC facility
  • Organisation and participation of the test campaigns


190130 14h28 jfm sphere comimac

Jean-François Muraz : Technical Manager, Spherical detector design
Mohammed Chala :Assembly
Olivier Guillaudin : Gaseous detector expert

  • Project management at LPSC.
  • Definition, design followed by realization of a µTPC bi-chamber using a new generation of MicroMegas (Bulk) of gas amplification.
  • Definition, integration and participation in the exploitation of the workbench for Quenching factor measurement for MicroMegas detectors calibration.
  • Definition, and tests for a miniature ions source for µTPC calibration.
  • Design and realization of a station for gaz blending and filtration.
  • In charge of logistics operations for off-sites measurements campaigns.
  • Development of command-control software for ions sources.
  • Participation in the evaluation of µTPC concept witn industrials.
 190130 14h28 jfm sphere comimac


Olivier Guillaudin : Technical Manager
Alain Pélissier : Detector Development
Jean-François Muraz : Detector Design, COMIMAC platform manager
Marc Marton : Detector Design

190510 11h06 oz dame1 labview190510 11h06 oz dame2 setup190510 11h06 oz dame3 detecteur

  • Design, elaboration and tests of gaz detector prototypes for beam profile measurements in conformational radiotherapy
  • Patent co-author
  • High throughput data acquisition

Olivier Guillaudin : Detector Development
Olivier Zimmermann : Data acquisition

190117 14h17 oz hyperlinkDAMe page at LPSC Grenoble

On the LOHENGRIN experiment installed at ILL (Laue Langevin Institut), the SDI opearted on of a double small detector with neutrons manufacturing, with reading of current on the anodes XY wires composed of 4 cathode plans and of 8 anode plans (outside dimensions 75 mm × 38 mm), the useful window of detection of 20 mm by 20 mm. This activity, which took place in the year 2007, corresponds to :

- The manufacturing of 4 cathodes plans stuck, that is 4 times 2 frames FR4/Cu, 2 faces of 16/10 of mm of thickness. These two frames are in coincidence with, in the middle, a window of Mylar aluminised, 2 faces of 23 µm, with the HV supply contacts.

- The weaving of 2 wires plans (aluminum frames 250 × 140 × 10 mm). The wires are W/Au/Re of 30 µm, with a tension of 30 g, a tep of 1 mm, that is 115 wires/frame, for transfer on frames anodes.

- The transfer, the welds and the cuttings of the wires on the frames pads of XY anodes. There is 4 XY groups, that means 8 frames of FR4/Cu, two faces of 16/10 of thickness.
By anode, there are thus 20 wires at a step of 1 mm through useful window of 20 mm × 20 mm. Every anode has its reading electronic system directly cabled on the frame (printed circuit).



190117 14h17 oz hyperlink LOHENGRIN homepage

For the CMB Survey (Cosmic Microwave Backgroung), the experiments have for objective the measurement of the polarization of the radiation.

On the other hand, the LPSC, in association with the Ultra low Température group at Louis Neel Institute (ex CRTBT), was responsible for the manufacturing project of the mechanical part of an Martin Puplett interferometer (MPI, photo), this device was dedicated to the tests of arrays in the millimetric and submillimétric length domain.

In 2004, the department participated actively in the sizing of the interferometer and in the specification of components. The department of study and mechanical realization of the LPSC then designed and realized all the parts of the Martin Puplett during year 2005. The final assembly and the installation at CRTBT took place in December, 2005 (collaboration of the SDI and the engineering workshop).


Contact : Myriam Migliore

Martin Puplet Interferometer




190117 14h17 oz hyperlink homepageCosmological Microwave Background (Wikipedia)