From Dmitri_Denisov Date: Wed, 27 Mar 2002 17:45:01 -0600 (CST) Subject: Increasing D0 operating efficiency Dear Captains! Over last 3 months we are steadily increasing D0 operating efficiency from ~30% after November shutdown to ~60% recently. Improvements are obtained both by improving hardware/software as well as our operating procedures. Below there are a few items which are useful to keep in mind in order to continue increase of our operating efficiency: 1. Time needed to ramp SMT HV down is currently 7minutes. So, 10 minutes before end of store (MCR suppose to call you 15 minutes before termination) you have to end global run and ask SMT and muon shifters to ramp HV to standby values. As soon as HV is reduced (about 2-3 minutes before expected store termination) you have to call MCR and confirm that D0 is ready for store termination. SMT group is working on futher reduction of HV ramp down time. It will be about 2minutes soon. 2. Time at the begining of the store is most valuable, but we typically loose 20-30 minutes starting global run due to readout problems. In order to reduce this period follow store checklist instructions: as soon as p's and pbar's are loaded, start global trigger list non recorded run with ALL crates planned to be in readout with recording OFF. You don't need HV to be ON for this run and you will exersize full DAQ/trigger system before beam. You can always adjust prescales on zero-bias trigger (global trigger list) to keep events flowing. As soon as store is colliding (watch ACNET and talk to MCR) you have to issue "begin store" command, ramp HV up (2 minutes), download correct prescale file and start global run. We did have stores when data collection started 5(!) minutes after begining of the store. 3. With current DAQ and our recommended trigger rates (60-80Hz into L3 and 20-30Hz to tape) our average FEB should be in the 5-10% range. Check this FEB value from time to time: it could increase substantially due to readout problems. DAQ/L3 group is working on reducing FEB number. 4. About 12% of D0 deadtime is due to muon readout crates errors. Short term solution is to watch closely events flow and reset/restart crates as soon as error observed. Typical current error rate is once per 10 minutes. Muon group is working on reducing this error rate. 5. Last serious downtime item is "major problem". Like master clock problem or similar. The best rule here is: if problem is not resolved within 5-10minutes by your crew start calling experts. Leslie just updated D0 Personnel Call List. 6. In summary, currently major factors of luminosity loss (all factors provide ~10% loss of delivered luminosity) are: beging/end store problems, FEB, muon readout crates, "major" system problems. All, except FEB, could be reduced substantially by effecient shift crew. Dmitri.