LENS R&D

Collaboration:

- Italy: INFN – Laboratori Nazionali del Gran Sasso
- France: College de France – Paris; DAPNIA CEA – Saclay
- Germany: MPIK – Heidelberg
- Japan: RCNP – Osaka (Japan)
- Russia: Institute of Nuclear Research RAS – Moscow; Institute of Physical Chemistry RAS – Moscow
- USA: Bell Laboratories – Murray Hill NJ; B.N.L. – Upton NY; LAL – Los Alamos NM

Location of the experiment: LNGS

National Responsible: C. Cattadori

1. Goal of the experiment

LENS is the acronym of Low Energy Neutrino Spectroscopy.

LENS R&D, has the goal to develop and fully characterize organic liquid scintillators (LS) with high scintillation output and attenuation length, and high (~10%) loading in Yb, In and other elements having isotopes with characteristic signature and high cross section for electron neutrino capture.

This development could be of interest also in neutron detection applications, as the cited elements have large cross sections also for neutron capture reactions.

Another aim of LENS R&D is to test O(100 l) modules of the produced liquid scintillator in a shielded environment, to study the intrinsic background of the scintillator.

More on the experiment…

2.

Activities during 2002

The activity during 2002, can be summarized as follows

- Completion of the low level underground test facility: the shielding (20 cm polyetilene, 23 cm iron and 15 cm ultralow background copper), offer an internal shielded volume of 2 m3; the measured (gamma ray spectrometry with Germanium detector) gamma background reduction factor is 104 í 105. The facility has been equipped with analog and digital electronic readout for up to 16 channels.

- Definition and Optimization of an original recipe to produce liquid scintillator highly doped (up to 10%) with Indium metallorganic compound having high performances in terms of light yield and transparency. Characterization of the fluorescents properties of the produced liquid scintillator, study of the stability in time of relevant parameters. Study of the properties of Indium loaded liquid scintillator based on different primary solvents (mineral oil, pseudocumene, dodecane, mixtures of listed solvents etc).

- Simulations of neutrino signal in presence of background for the full scale detector. In particular the mimics of the pp neutrino tagging from uncorrelated subsequent 115In beta decay producing bremssthralung gammas has been investigated. From the simulations the minimal requirements for the full scale detector to detect pp neutrinos come out; a segmented detector having Indium loaded cells (9cm x 9cm) intercalated with no Indium loaded cells. For this configuration the efficiency for neutrino detection is 20% with a S/N of 4: for 7Be neutrinos only, an homogeneous detector would be feasible with a detection efficiency of 57% (for 10 cm x 10 cm cells) and a S/N ca. 7.

- Simulations and tests of the reflectivity of high reflectivity film (VM2002 produced by 3M) and on flat quartz surfaces in view of prototype cells production.

- Commissioning of the inner array of cells (9 cells, quartz HSQ, 5 cm x 5 cm x 80 cm)

- Commissioning of the low level PMs

for the inner array readout

The following achievements have been obtained:

- Completion of the low level underground test facility (LLBF) (100 %)
- Background measurements in the LLBF with Germanium spectrometer (100 %)
- Definition and Optimization of two original and independent recipes (90 %)
- Montecarlo studies of granularity neutrino detection efficiency and S/N for a hypothetical full scale experiment (90 %)
- Simulations and tests of the reflectivity of VM2002 and flat quartz surfaces (100 %)
- Commissioning of the inner array of cells (quartz made) (100%)
- Commissioning of the low level PMs (100 %)
- Indium Bremmstrahlung (BS) measurements (50% ( ongoing))

Milestones 2003:

Synthesys of O(10 l) InLS with the best available (actual) recipe | 30-02-2003
End of the In bremsstrhalung measurement on 1 kg metallic In by Ge detector | 30-03-2003
Installation in the Low Level Background Facility (LLBF) of the inner quartz cells array and of the outer anticoincidence cell array + low level PM installation | 30-04-2003
Measurement in a shielded environment of O(5 l) InLS | 30-05-2003
Final fixing of the InLS synthesys recipe on the base of the ongoing stability/ageing studies | 30-06-2003
Measurement of O(50 l) InLS in inner cell array. | 30-12-2003

3. INFN contribution to the experiment in term of manpower and financial support

- Manpower: 4 researchers (0.9 FTE)
- Budget for the Year 2003: 0.2 % of the CSNII budget

4. Publications in refereed journals (in 2002): 1

5. Conference talks (in 2002): 2

6. Number of undergraduate and doctoral thesis on the experiment:

Undergraduate student: 1 student from l’Aquila University is doing her “tesi di laurea” on the characterization and development of InLS. She will graduate on April 2003.

7. Leadership roles and primary responsibilities in the experiment:

MPIK: LLBF, Electronics and DAQ, Inner cells array,

Reflectivity tests, LS development

INFN-LNGS: LS development and characterization, BS measurements

INR: LS development and characterization

DAPNIA-CEA: Montecarlo and Simulations

College de France: Electronics

Los Alamos: Envelope array of cells, test cell

Bell Labs: LS development

8. Innovative instruments:

Highly loaded (up to 10%) Indium scintillators, having veru good performances in terms of light yields and transparency. Light yields of the order of 8000 ph/MeV and light attenuation length of order of 1 m @ 430 nm have been obtained

9. Competing experiments:

- SIREn R&D

10. International committee which has reviewed the experiment:

This first phase of R&D for scintillator development is under examination by the INFN Committee II. LNGS Scientific commette reviewed the whole project both in March 2002 and in October 2002.