HIGH VOLTAGE POWER SUPPLY SYSTEM FOR CMS FORWARD SUBDETECTOR

Lubomir Dimitrov, Ivan VankovNuclear Electronics Laboratory, Institute for Nuclear Research

and Nuclear Energy, BAS

I. Vankov ET 2004, Sozopol, Sept. 2004

HV PSS for HF

I. Vankov ET 2004, Sozopol, Sept. 2004

HV PSS for HFLHC TUNNEL

I. Vankov ET 2004, Sozopol, Sept. 2004

Compact Muon Solenoid (CMS)

HV PSS for HF

HE HB

HF2HF1

I. Vankov ET 2004, Sozopol, Sept. 2004

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)

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

I. Vankov ET 2004, Sozopol, Sept. 2004

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)

HV PSS for HF

I. Vankov ET 2004, Sozopol, Sept. 2004

D1

D2

K

D3

D4

D5

D6

D7

D8

A

S

ID50 μA

D1

D2

K

D3

D4

D5

D6

D7

D8

A

S

A

B

C

D

E

F

A

B

C

D

F

E

D1

D2

K

D3

D4

D5

D6

D7

D8

A

S

A

B

C

D

F

E

PMT

No1

PMT

No2

PMT

No8

LG

UK

UD7

UD8

PRINTED CIRCUIT BOARD DIAGRAM

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:

UK = 2000 V; UD7 = 800 V; UD8 = 400 V

RESULTS: STABLE VOLTAGE TO D7 AND D8

VERY LOW POWER LOSSES

HV PSS for HF

I. Vankov ET 2004, Sozopol, Sept. 2004

ONE QUADRANT HV SYSTEM STRUCTURE

PS3

PS2

PS1

ROBOX No 13 PCs x 8

PMTs

Cable No 1

Cable No 2

Cable No 9

9 HV cablesL15 m

1 HV cableL150 m

ROBOX No 2

ROBOX No 9

HV MODULE No 1

UUD7,1

LG

UD8,1

UK,1

UUD7,2

LG

UD8,2

UK,2

UD7,2

LG

UD8,2

UK,2

UD7,1

LG

UD8,1

UK,1

UD7,3

LG

UD8,3

UK,3

UUD7,3

LG

UD8,3

UK,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

HV PSS for HF

I. Vankov ET 2004, Sozopol, Sept. 2004

HV CHANNELS PARAMETERSPARAMETER CHANNELS

1, 4, 7CHANNELS

2, 5, 8CHANNELS

3, 6, 9

Max. output voltage, V 2000 800 400

Voltage resolution step, V

1 1 1

Output ripple, mVP-P 300 300 300

Floating output Yes Yes yes

Max output current, mA

0,5 0,5 0,5

Long tem stability, % <0,1 <0,1 <0,1

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