E.Gushchin,S.Filippov(INR,Moscow) 16 April 2008Calo commissioning meeting CERN PS/SPD LED monitoring system status General status LED signal is used for checks and time alignment of detector/electronics during commissioning before physics. To prevent PMT suffering the hot LED light has to be discriminated by tuning of LED driver channels. Also the goal for tuning is to minimize the light variation within group of LED fired simultaneously (up to 256 LED) and operated by one DCS channel (up to 512 LED). PS “A” and “C” side, and SPD “C” side data taken in February. Few problems with cables, and “hot” channels with bad resistors are fixed. In zero approximation is OK, except one problem with shortcut on LED cable on PS “C” side, which is known and to be fixed. No regular tuning using on-line DAQ is done yet. SPD “A” : first data taken on 14 March show some problems. No threshold scan was available, so the tuning using online measurements is done using adjustment of the LED light for fixed threshold for the set of two PMT HV (500V and 700V). All outer and inner parts are tuned at 2500 DAC counts, middle part is tuned at 1600 counts.

E.Gushchin,S.Filippov(INR,Moscow) Tuning of LED light on SPD ‘A’ side The problems has been solved: 1.some “hot” channels, this was solved by resistor repairing 2.worse uniformity for some PMT, solved by tuning 3.“Noise” after LED pulse at some PMT. This is explained by low threshold. Effect is also reduced after tuning. 4.difference in LED bias point, i.e. for middle vs inner region. This is essential for different LED types. Finally, all middle part is tuned at the lower bias voltage (1600 DAC channels) and it is connected to separate DCS channel. 5. LED trigger timing problem for some VFE. It seems to be eliminated by correct initialization within PVSS project for LEDTSB. 16 April 2008Calo commissioning meeting CERN

E.Gushchin,S.Filippov(INR,Moscow) 26 March 2008Calo commissioning meeting CERN Checks Check of mapping was done with LED switching one by one for top and bottom of the detector. Checks with tuning confirmed. Check on the detector: few (~5) ‘hot’ channels -> problem with tuning resistors, easy solved by replacement. One LED shown 800 Om resistance for bias voltage was disconnected. Check jitter of LEDTSB output: In crate PRS7 the output pulse width was jumping nsec. It was seeing on Monday. On Tuesday it was not reproducible. Anatoly’s suggestion is that LEDTSB was not completely correctly configured. Continue to learn. Check of “noisy” LEDs: Trying twice larger VFE threshold reduce noise -> sometime threshold is too low.

E.Gushchin,S.Filippov(INR,Moscow) 26 March 2008Calo commissioning meeting CERN Tuning 6B01 500v/700v 700V better timing 700V Timing problem 500V

E.Gushchin,S.Filippov(INR,Moscow) 16 April 2008Calo commissioning meeting CERN Plans On SPD A-side : 1. To check using threshold scan if the uniformity after tuning is acceptable or not. 2. To improve the LED trigger timing, if possible. On SPD C-side: 1.Check using threshold scan. 2.To tune for better matching DCS channels, the same as it is done on “A” side. Full tuning will take ~ 1 week. On PS: 1.To fix shortcut on “C” side. 2.If necessary, to tune for better matching DCS channels. Full tuning on A and C side will take 7-10 days.