1. HIGH VOLTAGE POWER SUPPLY SYSTEM FOR CMS FORWARD SUBDETECTOR Lubomir Dimitrov, Ivan Vankov Nuclear Electronics Laboratory, Institute for Nuclear Research and Nuclear Energy, BAS I. Vankov ET 2004, Sozopol, Sept. 2004

2. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004

3. HV PSS for HF LHC TUNNEL I. Vankov ET 2004, Sozopol, Sept. 2004

4. Compact Muon Solenoid (CMS) HV PSS for HF HEHB HF2HF1 I. Vankov ET 2004, Sozopol, Sept. 2004

5. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004 VERY FORWARD HADRON CALORIMETER (HF) Copper Block Cherenkov Detectors – Embedded Quartz Fibers 1728 Photomultiplyers (PMTs) Type Hamamatsu R7525 (8 stages: 7 dynodes + anode)

6. PROBLEMS CLASSIC SOLUTION: INDIVIDUAL RESISTOR DIVIDERS – GENERATE ALL PMT VOLTAGES, BUT: 1. NEED 1728 HIGH VOLTAGE CHANNELS and 1728 165 m long HV CABLES - VERY EXPENSIVE 2. LARGE SPACE FOR THE 1728 DIVIDERS 3. GREAT POWER LOSSES IN THE DIVIDERS – PRODUCE MUCH HEAT HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004

7. HV PSS for HF SYSTEM CONSTRUCTION 72 READ OUT BOXES (ROBOXES) – 36 for HF1 and 36 for HF2 36 roboxes – divided to 4 group of 9 corresponding to the four HF quadrants IN EACH ROBOX – 3 PRINTED CIRCUIT BOARDS (PCBs) AT EACH PCB – 8 PMTs (with similar parameters)

8. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004 PRINTED CIRCUIT BOARD DIAGRAM

9. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004 PRINTED BOARD CIRCUIT WITH 8 PMTs ONE RESISTOR DIVIDER FOR THE FIRST 6 DYNODES WITH TOTAL RESISTANCE ABOUT 20 Mohms – MAX. CURRENT < 50 uA THREE SUPPLY VOLTAGES: U K = 2000 V; U D7 = 800 V; U D8 = 400 V RESULTS: STABLE VOLTAGE TO D7 AND D8 VERY LOW POWER LOSSES

10. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004 ONE QUADRANT HV SYSTEM STRUCTURE PS3 PS2 PS1 ROBOX No 1 3 PCs x 8 PMTs Cable No 1 Cable No 2 Cable No 9 9 HV cables L 15 m 1 HV cable L 150 m ROBOX No 2 ROBOX No 9 HV MODULE No 1 U U D7,1 LG U D8,1 U K,1 U U D7,2 LG U D8,2 U K,2 U D7,2 LG U D8,2 U K,2 U D7,1 LG U D8,1 U K,1 U D7,3 LG U D8,3 U K,3 U U D7,3 LG U D8,3 U K,3 9 HV CHANNELS = 1 MODULE 1 CHANNEL SUPPLIES 9 PCBs 3 GROUPS OF 72 PMTs WITH SIMILAR PARAMETERS 1x12 WIRES 150 m HV CABLE 2x2 WIRES 15 m CABLES

11. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004 HV CHANNELS PARAMETERS PARAMETERCHANNELS 1, 4, 7 CHANNELS 2, 5, 8 CHANNELS 3, 6, 9 Max. output voltage, V2000800400 Voltage resolution step, V 111 Output ripple, mV P-P 300 Floating outputYes yes Max output current, mA 0,5 Long tem stability, %<0,1

12. HV PSS for HF I. Vankov ET 2004, Sozopol, Sept. 2004 CONCLUSIONS 1.HV SYSTEM NEW SOLUTION: PMTs united in groups with similar parameters; Only first 6 dynodes supplied by resistor divider, D7 and D8 – from individual HV channels; 9 PCBs (72 PMTs) connected to each HV channel. 2. ACHIEVED RESULTS: Drastically decreasing of numbers of the long HV cables – 8 instead of 144; Decreasing of the power losses and heating Drastically decreasing of the expenses