Документ взят из кэша поисковой машины. Адрес оригинального документа : http://nuclphys.sinp.msu.ru/conf/lpp14/200809/Stodolsky_nuta.pdf Дата изменения: Wed Sep 16 15:10:03 2009 Дата индексирования: Tue Oct 2 00:46:57 2012 Кодировка: Поисковые слова: earth

Neutrino Technology


Because of (neutron numb er)2

G2 2 2 = NE 4 Neutral-Current Coherent Scattering Gives Large Cross Sections on Nuclei for MeV Neutrinos


For example at a reactor

Seem to only need kilograms!


But Must detect very small recoil of nucleus
10's eV to keV's Hence

Cryo-Detectors


Many technological and practical difficulties Nevertheless prosp ect of small, light, p ossibly mobile, neutrino detector suggested consideration of practical applications






Claim 34­Geological studies, with tomography and mobiblity, p otentially very interesting. Lo ok for oil-b earing formations, U dep osits (could have seen one later discovered in Canada),...


Main Practical Applications Seen At Present Reactor Monitoring · In case of accident and no access into reactor, neutrino detector can follow state of nuclear reactions · Neutrino energy sp ectrum can determine comp osition of fissile materials and so indicate illegal use for b omb materials Geological Studies Search for mineral, fuel dep osits


DIFFICULTIES

I Neutral Current Detector sees all neutrino typ es

I I Backgrounds

A) Exp erimental (not in an underground lab) B) Intrinsic (solar, whole earth neutrinos)


Exp erimental backgrounds: Dark Matter searches have made much progress with two-channel readout. Distinguish nuclear recoils (want to see) from e/ backgrounds (want to eliminate). CRESST uses light signal in addition to heat signal:

Clear separation into nuclear recoil and e/ bands. Can such techniques b e extended to lower energies?

Or consider detectors not resp onding to e/ background, like COUPP.


In geological application: Instrinsic background for coherent (neutral current) detector: solar neutrinos. Not true for detector which distinguishes neutrino and antineutrino.


Seems to b e a "window" 2-5 MeV.


Note for geology we are interested in lo cal p ositional variations of neutrino flux, while solar, whole earth, reactor, backgrounds vary little. Can adequate statistics b e collected to see these variations?

100's /kg-day on first pages are now 10-5/kg-day. Formidable task­ but not imp ossible?


Present Situation · Coherent Scattering: Developments are in progress to observe the pro cess. Cryo- and semiconductormetho ds. · Geology: Large liquid scintillator detectors have seen geo-neutrinos from the whole earth at ab out the exp ected level of 106/cm2sec (Kamland). Future very large liquid scintillator detectors (LENA...) should improve signal considerably. A fundamental new to ol for geophysics. Will it b e p ossible to see lo cal variations? Note the 40K neutrino­imp ortant for earth ­ is b elow threshold for such (liquid scintillator, p e+n) Ї detectors. ·Reactor Monitoring: There is interesting progress on relatively simple, `inexp ensive' liquid scintillator detectors which would b e fixed installations at reactors.


TASKS · For coherent scattering, further develop techniques for seeing small nuclear recoils (sup erconducting grains still the most b eautiful?) · While simultaneously suppressing electron-photon backgrounds without heavy shielding · Light, compact, accessory equipment (cryostats, gas handling....) · For inverse-b eta detectors, develop small, practical systems · Understand neutrino signal of various geological formations


APPENDIX­Grain prop erties


REFERENCES Many of the p oints on the present situation were presented at the NUTECH-09 Workshop (Triest, June 2009)http:// cdsagenda5.ictp.trieste.it/ Tables and Drukier and of a neutral astronomy, plots on coherent scattering are from A. L. Sto dolsky, Principles and applications current detector for neutrino physics and Phys. Rev. D 30 2295 (1984),

The CRESST plot is Fig. 7 of G. Angloher et al., Commissioning Run of the CRESST-I I Dark Matter Search Astropartphys 31, 270 (2009); arXiv:0809.1829 [astro-ph].