(Germanium Experiment for measurement of Magnetic Moment Antineutrino) Experiment GEMMA (Germanium Experiment for measurement of Magnetic Moment Antineutrino) [Phys. of Atomic Nucl.,67,№11(2004)1948] Spectrometer includes an HPGe detector with mass 1.5 kg installed within NaI active shielding. The HPGe detector and the NaI are surrounded by multi layer passive shielding - oxygen-free copper, borated polyethylene and lead.

Suppression of microphonic noise

Background measurements 1 - detector without shielding, 2 - with passive shielding, 3 - with passive shielding plus active NaI and plastic scintillate shielding, 4 - with passive and active shielding plus frequency software cut. In energy region (10 – 60) KeV BG consists of ~ 2 events /KeV/kg/day

µ  GEMMA 5.0 ×10 -11 B Kalininskaya NPP (Udomlya): L = 14 m P = 3 GW = 2.6×1013  / cm2 / s T = 2 years µ  5.0 ×10 -11 B Raw spectrum Thr = 2 keV BG = 2.0 events / keV / kg / day Anti-coinc. with NaI “Fourier” –selection added

Reaching sensitivity in reactor experiment Nn : signal events B : background level m : target mass t : measurement time N  ν (neutrino flux) & related to T-threshold, reactor power and distance from reactor core. GEMMA II 2008 ν ~ 8×10 13  / cm 2 / s t ~ 2 years B ~ 0.2 keV-1 kg-1 day-1 m ~ 4.0 kg GEMMA III : m ~ 20 kg , Tth ~ 100 eV   1.5  10 -11  B  ~ 5  10 -12  B

Summary The present limit on NMM from star data could be confirm with modern and detailed observation of the parameters of He star flashing. The improving of the sensitivity on the NMM from solar data can be reached at analysis of the soft part of neutrino spectrum – new run at SK and future results from Borexino. In reactor experiment the sensitivity of the measurements NMM can reach value of   1.5  10-11  B during next 5 y. The Tritium Source of 40 MCi activity (4kg 3H) combined with ultra-low-threshold detectors (germanium and silicon) gives opportunity to reach sensitivity   2.5  10-12  B