R&D on detector components for rare K+ decay experiment in high intensity beam environment

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We have developed new detector components for rare K+ decay experiment to cope with high beam background environment:1)A new programmable trigger board and digital mean-timer modules using complex programmable logic device have been introduced to the trigger system of the BNL-E949 experiment. The online dead time was reduced from 4.0% to 1.7% by introducing an on-chip prescaler to the programmable trigger board. The acceptance loss of the online photon veto was reduced from 4.9% to 1.8% by introducing the mean-timer modules.2)We have developed a new heavy (XO=0.89cm) and radiation-hard (10**8 rad) Cherenkov radiators based on lead tungstate PbWO4 (PWO). We have found that doping PWO with trivalent rare-earth ions (La3+,Gd3+,Y3+,etc.) improves the characteristics of PWO dramatically including the transmittance, radiation-hardness and mechanical quality. In the course of studying the effects of trivalent ions, it has been found that heavy doping of these ions quenches the scintillation, thereby creating a new Cherenkov radiator by keeping good transmittance, excellent radiation-hardness, etc.3)We have developed a new monitoring system based on blue LED's. The system was introduced, to the E949 experiment, and enabled us to observe a variation within the beam spill. The kinetic-energy resolution of pi(+) in Kpi2 decay was improved from sigma=3.246MeV to sigma= 3.042MeV by using information of the new monitoring system.4)We have developed a single-sided silicon strip detector with a sensitive area of 92 x 92 mm**2 as a real-time, fast and medium-segmented hodoscope for rare kaon decay experiments in high beam background environment. The Equivalent Noise Charge(ENC, 1 sigma) at the preamplifier input was ~1600e (6% of the signal for single minimum ionizing particle ~27000e).