Problems of the Front-end Electronics

Low Voltage Power Supply in CMS

I. Vankov

         

CMS – BARELL + 2 ENDCAPS

 

          SUBDETECTORS:            

·       TRACKER (TR);

·       ELECTROMAGNETIC CALORIMETER (ECAL);

·       HADRON CALORIMETER (HCAL);

·       MUON CHAMBERS (MU).

 

NUMEROUS MEASURING CHANNELS:

·       EMU – 483830;

·       ECAL – 236830;

·       CMS > 106.

 

POWER CONSUMING FRONT-END ELECTRONICS

 

                                                                                           Table 1 

SUBDETECTOR

DIGITAL

I, kA

ANALOG

I, kA

TOTAL POWER

P, kW

ECAL

13,7

7,2

92,5

HCAL

2,35

1,7

21,6

EMU*

3,7

2,6

43

                        *EMU – Endcap Muon Chambers 

 

 

CLASSICAL SOLUTION – POWER SUPPLY CLOSE TO       THE LOAD

 

CMS LIMITATION FACTORS

·       MAGNETIC FIELD

·       RADIATION

MAGN. FIELD                   RADIATION      

INSIDE CMS                        4 T                   2 Mrad          5x1013 n/cm2

CMS PERIPHERY      0,1 – 0,32 T                   1,5/3x1010 n/cm2

GALLERY                         0,05 T                                    100 rad

OUTSIDE CAVERN   0                                            0

 

TWO BASIC SOLUTIONS

·       TWO STAGES LOW VOLTAGE SYSTEM

·       THREE STAGES LOW VOLTAGE SYSTEM

 

TWO STAGES LOW VOLTAGE SYSTEM

         

FOR ECAL AND TRACKER (?)

 

 

 

 

 

 

 


1864 LV CHANNELS

4 VOLTAGES IN ONE CHANNEL:  +5, -2 – analog

                                                                     +5, +2 – digital

 

HUGE POWER LOSS!

 

ULOAD, V

ULVPS, V

DU, V

I, kA

DP, kW

+5

+11,9

5,9

11,9

70,2

-2

-5

3

1,9

5,7

+5

+8,3

3,3

2,3

7,6

+2

+5,8

3,8

5,0

19,0

                                                                   Table 2

 

 

 

 

 

 

                                                       Total    102,5

 

         102,5 kW > 92,5 kW

 

 

  IF 120 m AWG 2 – 169,5 mm2 instead of 8 mm2 CABLE

                            

                             2,2 kW instead of 47,6 kW

  BUT

                      CABLE WEIGHT 176 900 KG

            CABLE CROSS-SECTION AREA 6320 cm2 (80X80 cm)

                 CABLE PRICE 1 726 000 $

 

THREE STAGES LOW VOLTAGE SYSTEM

FOR EMU and HCAL

VICOR DC-DC CONVERTERS

300 V input,  5 – 12 V output (nominal)

 

ME1/1 LOW VOLTAGE SYSTEM

 

 

 

 

 

 

 

 

 

 

 

 

 

    

 

 

 

 

 

      

 

                     Fig. 3

 

FOR ONE ENDCAP

 

30 kW input power at 300 V (70% efficiency) -

100 A current trough the 100 m long cables

 

AWG – 2  -  VOLTAGE DROP – 1,5 V

                   - POWER LOSS         - 144 W

 

 

 

 

MAGNETIC FIELD SHIELDING FOR DC-DC CONVERTORS

    FERMILAB’S PROTOTYPE - 1,25 cm SOFT IRON PLATES

    WITH WATER COOLING

 

Fig. 4

 

RADIATION PROBLEMS

 

TESTS WITH LOW ENERGY NEUTRONS:

OPTO COUPLER REPLACING BY HEWLETT-PACKARD’S

DEVICE

 

NEUTRON ENERGY – 60 – 200 MEV – SINGLE EVENT EFFECTS

TEST – 60 MeV PROTON BEAM IN Louven-la-Neuve, Belgium:

V300B12C250AL, VIN=300V,  VOUT= 12V, IOUT=21A

TESTED AT, VIN=200V,  VOUT=7,5V, IOUT=20 A

V300B5C200A, VIN=300V, VOUT=5V, IOUT =40 A

TESTED AT VIN=200V, VOUT=5,2V, IOUT=25 A

PASSED 2x1011 protons/cm2 WITHOUT PROBLEMS.

 

CONCLUSION

VICOR DC-DC CONVERTERS ROBUST AT REDUCED INPUT VOLTAGE – 200 V AND REDUCED OUTPUT POWER

 

PRICE OF EMU LVS SECOND STAGE:

·       DC-DC CONVERTERS  – 150 k$

          (with filters and PCB)

·       MAGNETIC SHIELDING –70 k$

                                       TOTAL       220 k$

 

TRANSFORMER SOLUTION FOR SECOND STAGE:

 

400 Hz AC

FULL WAVE RECTIFIER

 

PROVISORY COST ESTIMATION:

·       100 kVA 400 Hz MOTOR-GENERATOR    - 30 k$

·       TRANSFORMERS                                              - 15 k$

·       RECTIFIERS AND FILTERS                           -   8 k$

                                                                   TOTAL            53 k$

 

LINEAR VOLTAGE REGULATORS

 

EMU and HCAL - LHC4913

TESTS:

·       SPURIOUS CURRENT IN LOW VOLTAGE CONDITION;

·       NOT OPERATING INHIBIT FUNCTION

·       INSUFICIENT OUTPUT CURRENT - IOUT £ 2,6 A (INOM=3 A)

 

ECAL – MOTOROLA MC1723CP REGULATOR + SIEMENS

                SIPMOS TRANSISTOR SPP30N03L

         ALL CONTROL FUNCTIONS IN FIRST STAGE

 

TEST – ON PSI OPTIS BEAM with 1,25x109 protons/cm2s

                of 64 MeV

 

GENERAL CONCLUSIONS

 

1.                       The comparisons between three described variants of LVS show clearly, that the best solution is the three-stage system with transformers in second stage. Only reason to abandon it could be safety or noise considerations.

2.                       Further investigations and efforts needed for application of this system in ECAL and TRACKER.

3.                       Improvement of LHC4913 and further investigations of commercial low voltage regulators are necessary for finding and optimal solution.