In the sun and massive stars, hydrogen is burning and helium is increasing by nuclear fusion reactions. After hydrogen is burnt out, helium burning takes places in massive stars, and ¹²C and ¹⁶O, which are important for organisms, are produced. In heavier stars, ¹²C and ¹⁶O begin to burn and supernovae occur. Our galaxy has two supernovae in 100 years on the average.
In the helium burning, ⁴He+¹²C->¹⁶O+g reaction plays a very important role in determining the ratio of ¹²C/¹⁶O and the scenario to proceed to supernova. Many efforts to measure the ⁴He+¹²C->¹⁶O+g reaction rate have been made for over 30 years in the world, however, the reaction rate is still unknown. The measurement is extremely difficult because the reaction rate is small and very few ¹⁶O's are produced.

The measurement is planned at the Kyushu University tandem accelerator laboratory (Fig.1). For this experiment, new methods have been invented.
1) ¹²C beam intensity was 1,000 times increased by a new idea of accel-decel strong focusing and by a new gas stripper that has the largest aperture in the world.
2) Target ⁴He gas is confined in vacuum without foils by a new idea of blowing-in.
3) Produced ¹⁶O's are separated from ¹²C beam and focused a recoil mass separator.
4) Continuum ¹²C beam was transformed to a pulsed beam to reduce backgrounds.

At present, the background level is 10^-14 of the ¹²C beam. When the level reaches 10^-15 we will start the measurement, and we will complete it when the level is reduced to 10^-19. A German group is making similar efforts. In a few years, the ⁴He+¹²C->¹⁶O+g reaction rate will be measured accurately at Kyushu University and in Germany.