HKS TOF hodoscopes

The HKS TOF hodoscopes determine the trigger timing and measure the velocity of the charged particles. There are three sets of hodoscopes, HTF1X, HTF1Y, and HTF2X. Each hodoscope consists of BC408 scintillator, equipped with acrylic light guides and Hamamatsu H1949-50 phototubes on both ends. The active area of the hodoscopes is 30$\times$125 cm$^2$ for 1X, 1Y and 35$\times$170 cm$^2$ for 2X. Figure 42 shows a schematic drawing of HTF1X. It consists of 17 scintillator slats each of which is 20 mm thick, 75 mm wide, and 300 mm long. Figure 43 shows the schematic drawing of HTF1Y. It consists of 9 segments of scintillation counters (20 mm thick, 3.5 cm wide, and 1250 mm long). HTF2X consists similarly of 18 segments of scintillation counters with a size of 20 mm thick, 95 mm wide, and 350 mm long.

The distance between HTF1X and HTF2X, 1 meter, was determined to allow flight time sufficient to separate kaons from pions in the momentum region of interest. A time resolution of 77 ps (rms) was achieved at the KEK-PS T1 test, corresponding to better than 4$\sigma$ separation between 1.3 GeV/$c$ kaons and pions (figure 44).

All materials purchased in Japan have arrived at Jlab. Gluing of plastic scintillators and PMTs is in progress at EEL building of Jlab. Test bench for the cosmic-ray test is ready.