The solar neutrino unit (SNU) is a unit of Solar neutrino flux widely used in neutrino astronomy and radiochemical neutrino experiments. It is equal to the neutrino flux producing 10−36 captures per target atom per second.[1] It is convenient given the very low event rates in radiochemical experiments. Typical rate is expected to be from tens SNU to hundred SNU.[2]
There are two ways of detecting solar neutrinos: radiochemical and real time experiments. The principle of radiochemical experiments is the reaction of the form
| A | |
| N |
Z+\nue
| A | |
| \longrightarrow | |
| N-1 |
(Z+1)+e-
The daughter nucleus's decay is used in the detection. Production rate of the daughter nucleus is given by
R=N\int\Phi(E)\sigma(E)dE
\Phi
\sigma
N
With typical neutrino flux of 1010 cm−2 s−1 and a typical interaction cross section of about 10−45 cm2, about 1030 target atoms are required to produce one event per day. Taking into account that 1 mole is equal to 6.022 atoms, this number corresponds to ktons of the target substances, whereas present neutrino detectors operate at much lower quantities of those.