the Russian-American Gallium
solar neutrino Experiment


A Brief Description of SAGE


SAGE is a solar neutrino experiment based on the reaction 71Ga + n goes to 71Ge + e-. The 71Ge atoms are chemically extracted from a 50-metric ton target of Ga metal and concentrated in a sample of germane gas mixed with xenon. The atoms are then individually counted by observing their decay back to 71Ga in a small proportional counter.

A thumbnail pointing to a picture of the lab.
The 10 reactors containing the Ga can be identified by the red tops of the stirring motors. The glassware to the right is for the Ge extraction chemistry.
A thumbnail pointing to a picture of a proportional counter.
A typical ~16-cm long counter is shown.

The distinguishing feature of the experiment is its ability to detect the low-energy neutrinos from proton-proton fusion. These neutrinos, which are made in the primary reaction that provides the Sun's energy, are the major component of the solar neutrino flux and have not been observed in any other way.

To shield the experiment from cosmic rays, it is located deep underground in a specially built facility at the Baksan Neutrino Observatory in the northern Caucasus mountains of Russia. Nearly 100 measurements of the solar neutrino flux have been made during 1990-2000, and their combined result is a neutrino capture rate that is well below the prediction of the Standard Solar Model. The significant suppression of the solar neutrino flux that SAGE and other solar neutrino experiments have observed gives a strong indication for the existence of neutrino oscillations.

A thumbnail pointing to a description of the lab's overburden.
Mt. Andyrchi is shown with the lab's configuration. In addition the overburden and muon flux is shown as a function of distance into the Baksan Neutrino Observatory.
A thumbnail pointing to location of SAGE in Russia.

The overall functioning of the experiment was confirmed by calibration with a 517 kCi artificial neutrino source.

We acknowledge the support of the Russian Academy of Sciences, the Institute for Nuclear Research of the Russian Academy of Sciences, the Russian Ministry of Science and Technology, the Russian Foundation of Fundamental Research, the Division of Nuclear Physics of the U.S. Department of Energy, the U.S. National Science Foundation, and the U.S. Civilian Research and Development Foundation. This research was made possible in part by grants from the International Science Foundation and the International Science Foundation and the Russian Government.

For more information try the following links.


| The SAGE Collaboration | A Publication List |
| A Table of the Individual Extraction Parameters and Results | The Most Recently Released Results |
| The Argon Neutrino Source Development |


| UW Physics | UW electroweak Interaction Group |
| John Bahcall's Neutrino Page | The Neutrino Oscillation Industry |
| The Ultimate Neutrino Page |


This page maintained by
Steve Elliott (

Last updated on October 19, 2001