1. E.Guschin (INR,Moscow) 26 February 2008PS/SPD commissioning meeting CERN PS/SPD LED monitoring system status Tuning of SPD ‘C’ side: We concentrated our efforts on known problems: few ‘hot’ LED channels and group of very weak 16 LED’s. Also checks with new data show that some of not working drivers were already recovered since last data taking (May,2007) currently: ‘hot’ channels are tuned SPD4B05 weak driver was tuned during last night after a quite hard work. This was the very first experience of interactive tuning with data. Many thanks to Edu, Carlos and Álvaro. In first approximation, the tuning of LED on SPD “C” side is done. Some more checks and finalizing is needed.

2. E.Guschin (INR,Moscow) 26 February 2008PS/SPD commissioning meeting CERN PS “C” side Last data taken last Friday (Valentin) show few problems with full saturation at highest VLED bias voltage: PS2 – top part PS3 – middle part PS4 – two FEB (LED power cable PS4-4, trigger cable PS4-8) The reason found on PS2 and PS3 was bad connection in VLED bias line. In PS2 was shortcut in LED connector on module P90, in PS3 connection was lost inside the top electronic box. In both cases the result is ~0 voltage on LED -> always maximum light. The PS2 and PS3 were repared, PS4 is OK (reason is unknown). New data are needed for check.

3. E.Guschin (INR,Moscow) 26 February 2008PS/SPD commissioning meeting CERN Installations On PS “C” side all Al covers are installed. On SPD4 radiation monitor postbox is installed. The LED cables around the rack on “A” side were rearranged, thanks to Philippe. 44 cm 12 cm

4. E.Guschin (INR,Moscow) 26 February 2008PS/SPD commissioning meeting CERN To do To continue measurement of LED signals as function of LED bias (intensity) for PS ‘A’ and ‘C’ side in order to check LED operation. To finish the tuning on SPD “C” side and to move the work to “A” side.

5. E.Guschin (INR,Moscow) 26 February 2008PS/SPD commissioning meeting CERN Discussion Safety problem was arisen by Edu for PMT could suffer from high LED light. Critical situation: 1.HV and all low voltages are ON 2.LED bias is wrong or off -> high light 3.LED trigger from LEDTSB has to run. It seems it is more general problem, the protection is needed on occasional running with wrong settings. One of possible improvements are the rearrangement and restrictions at menu level.

6. E.Guschin (INR,Moscow) 26 February 2008PS/SPD commissioning meeting CERN Correction of LED group mapping Now is corrected. Before it was shown as 4-III.