Development of TOF detector with ultra-thin Formvar films for astrophysics experiment

At Kyushu university tandem laboratory, we are measuring $^{4}$He ($^{12}$C, $^{16}$O) gamma reaction cross section for the energy range of E$_{\mathrm{cm}}=$ 2.4 to 0.7 MeV by detecting $^{16}$O recoils. The produced $^{16}$O ions are transported to a recoil mass separator where they are separated from the unreacted $^{12}$C beam and they are detected by a particle detector placed at focal plane. Since the energy of the produced $^{16}$O ions were very low, the detector should have as small a thickness as possible. It is also of importance to have large effective area to collect all $^{16}$O ions. To satisfy these requirements, a TOF detector employing micro-channel plates was developed. Special attention was paid to develop an ultra-thin and large area formvar film, which acts as an electron emitter and a cathode electrode. The thickness was estimated to be 4 $\mu$g/cm$^{2}$ by measuring the energy loss of $^{16}$O beam, and the effective area was 80mm in diameter. In this symposium, we will report the method and the result of performance test of the developed TOF detector.