These are minutes of BCG meeting held on 6-Apr-00. ----------------------------------------------------------------------------- *Recent status of operation (Haba) He briefly summarized the status of the masks and recent way of operation. The Mask set for "Injection" and "Physics" are re-arranged to reduce background more during Injection. Recent observation in Radfet shows the dose deposited during an injection is sigiificant for LER and "wide acceptance for LER injection" may be bad. As long as an injection efficiency is not degraded much, we will make the masks narrower. *Accident happened in Apr.1 and Apr. 5 (Tsuboyama) He reported on recent two accidents where a large dose deposited in BELLE. *What can we do more to prevent a large dose exposure especially during an injection. We discussed how to reduce danger of sudden large dose in a short pulse. 1)We ask KEKB crews to establish the procedures for a recovery from bad injection, which may include some confirmation that all major parameters are reproduced consistently. 2)1Hz operation: 3)Try to reduce charge per pulse (for example, with screen inserted) 4)Try to store small current with larger beta optics and then establish orbit. 5)KEKB team will develop a system which monitor the beam postion even in an injection period (That means the monitors working in a single turn mode). This helps much for their diagnositics of the injected beam. Currently SVD is turned-on even during injection. Tsuboyama's observation shows that the power consumption of VA1 chips increase as a step function when somthing radiation related happen. At the Apr.1 accident there were several steps there. A simple turn-off and -on procedure did not recover those increase (An automated turn -off and on happens when a beam abort is issued) Turning-off during a long bad injection might be better. (Who knows that would be long!) We will have a new procedure for SVD protection poposed soon from the SVD group. -- ------------------------- Best Regards; Junji Haba 幅 淳二 (in Kanji)