Results

The aim of BINGO is the development of a technology capable of investigating the Majorana nature of neutrino with unprecedented precision, down to a sensitivity of a few meV to the Majorana neutrino mass.

Preliminary results
Preliminary results

The first mini nylon assembly. Two Li2MoO4 crystals are fixed using nylon wire and PTFE pieces. Each detector is facing a square light detector that is sandwiched between the PTFE pieces.

Several tests have been carried out to validate the final mini-BINGO assembly. As a first test, two 2*2*2 cm^3 Li2MoO4 crystals held and fixed using a nylon wire was measured. The crystals were facing Ge wafer light detectors to read the scintillation light emitted from Li2MoO4. The test was carried out in a pulse-tube cryostat at IJCLab. The measurement have shown a very promising results. In fact, we had a very good sensitivity (nV/keV), energy resolution and baseline noise.

 

For the BINGO active veto candidates, a test was performed on samples of the two scintillators, ZnWO4 and BGO, facing circular light detectors. The measurement was carried out to study the light yield (keV/MeV, which is the energy of photons in the light detector in keV for a 1 MeV energy deposition in the scintillator) and radioactive contamination to choose the most proper scintillator as a veto for mini-BINGO. The light yield for cylindrical Ø6×3 cm BGO and ZnWOwere respectively 28 keV/MeV and 14 keV/MeV. 

 
Preliminary results

BGO crystal that was tested to study its light yield. This crystal is one of the proposed scintillators to be used as the veto for the mini BINGO. A ZnWO4 crystal with the same dimensions and assembly was also tested.

Preliminary results

Two BINGO assembly modules. Each module hosts 2 Li2MoO4 couples to two light detectors.

An underground cryogenic run of two BINGO nylon wire assembly modules was performed in July 2022. The measurement took place in the CROSS facility at Canfranc underground laboratory (LSC, Spain). Each module contained a two Li2MoO4 crystals that are coupled to a light detector each. The light detector is slid between three Teflon pieces that contains a slot. Against the same Teflon pieces, the Li2MoO4 are fixed. A nylon wire is used to permanently keep the crystals and the LDs. The nylon wire is stretched using a torque screw driver to exert the necessary tension to fix well the LDs and crystals (4kg for each wire extremity). The results showed a good bolometric performance for this innovative assembly with no hints of extra noise due to the nylon wire.

 

A prototype test on BINGO active shield was performed on a small section of the veto, composed of two bars of BGO scintillator. Each BGO is coupled to two normal Ge wafer light detectors (not Neganov-Luke LD). The two BGO were facing a TeO2 crystal that has a Uranium alpha source on the face facing BGOs. This source was deposited on TeO2 in order to produce surface events to study coincidences between BGO and TeO2. The measurement was performed in a pulse-tube cryostat at IJCLab (Orsay, France). The results showed a clear ability to tag alpha surface contamination through anti-coincidence between BGO and TeO2.

 
Preliminary results

Neganov-Luke light detectors. Top left: concentric square electrodes with rounded corners deposited by evaporation (the voilet color is SiO deposited on the wafer to increase light collection). Top right: concentric square electrodes with rounded corners deposited by lithography. Bottom left: concentric ring electrodes deposited by evaporation. Bottom right: double meander electrodes deposited by lithography.

A study on Neganov-Luke LDs is ongoing. The study is focusing on testing LDs with different electrodes geometries and different electrodes deposition techniques (evaporation and lithography). 

 
#12 - Last update : 06/07 2023