Development of a Liquid Deuterium Target System for the Neutral Kaon Spectrometer(I. Nuclear Physics)

We have developed a liquid deuterium target system to be used with the Neutral Kaon Spectrometer (NKS). We designed the system with attention to yield, background and safety. For maximizing the K^0 yield, target thickness was optimized and the density of the liquid was kept as high as possible. For minimizing the background, we tried to reduce the amount of material around the target region. For the safety operation, we adopted the LabVIEW on Linux which enabled the remote monitoring and controlling. The target cell is made of aluminum outer shell with a thickness of 1mm and beam windows of 75μm thick polyimide film. We adopted the carbon fiber reinforced plastic (CFRP) with a thickness of 1.5mm for the material of the wall of the vacuum chamber covering the target cell. We succeeded in suppressing the boiling of the liquid deuterium and keeping the state as long as 2 weeks. The density of the liquid deuterium throughout the beam time in May 2004 was 0.1731±0.00007g/cm^3 including long term stability and short term fluctuation. The total error of the number of the target is 0.63%, which is much less than the statistical error