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Powering the main linac implications

This article discusses the cost impact of power converters, power consumption, power losses, heat load, and space allocation in the main linac, along with the implications of radiation exposure and EMI production.

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Powering the main linac implications

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  1. TE EPC Powering the main linac implications OUTLINE : Cost impact of power converters, power consumption and powering strategy, power losses, heat load, needs in space allocation. Daniel Siemaszko, Serge Pittet 01.06.2010

  2. Cost impact of converters (1/2) TE EPC CONVERTER COST µ POWER · MTBF · 1/MTTR · EFFICIENCY · PRECISION · REVERSABILITY · 1/VOLUME Radiations have an impact on: • MTBF: Mean Time Between Failure must be as high as possible considering the large number of power converters needed in the main linac. • MTTR: High spare quantity needed to compensate faulty module cool-down time. • EFFICIENCY: Sensitive switch mode supplies needed for high efficiency. • PRECISION: complex digital system needed in the 100ppm range. • REVERSABILITY: increased number of switching and control devices. • VOLUME: More sensitive active devices needed to reduce converter volume. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  3. Cost impact of converters (2/2) TE EPC • MB and DB main converters: • POWER · MTBF · 1/MTTR · EFFICIENCY · PRECISION · REVERSABILITY · 1/VOLUME • Low radiation area needed. • Correction dipoles: • POWER · MTBF · 1/MTTR · EFFICIENCY · PRECISION · REVERSABILITY · 1/VOLUME • Low radiation area needed. • DB trims: • POWER · MTBF · 1/MTTR · EFFICIENCY · PRECISION · REVERSABILITY · 1/VOLUME • Radiation hard modules could be deployed. CriticalModerate impactReasonable Daniel Siemaszko, Serge Pittet - EDMS 1075533

  4. Radiations in the tunnel TE EPC • Most of the radiations come from the drive beam (90%). • The expected average dose after four hours cooling reaches 100mSv/h. • A technician coming down on a monthly basis will be walking 1.5h in the tunnel. • The technicians will be exposed to a collective dose of 120mSv/year. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  5. Power distribution TE EPC • High voltage cables (36kV) go through the tunnel to power each cavern. • 36kV/400V transformers connect grid to distribution panels (Ref. C. Jach). • 400V grid in the tunnel is impossible because of power dissipation and voltage drop. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  6. Power consumption TE EPC • The consumption of the main linac is about 1.5-1.9MW per accelerating sector (considering losses). • Need for a distribution transformer of about 2.5MVA for each accelerating sector. • Total power consumption for the main linac: 80MW (100MVA). Daniel Siemaszko, Serge Pittet - EDMS 1075533

  7. EMI produced by cables TE EPC • 36kV grid produce 50Hz EMI on main beam transport. • DC cables for powering magnets produce EMI on module. • Magnetic field estimated for cables without shielding and arranged in compact pairs with very low distance between them. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  8. Space allocation in caverns TE EPC • The required space allocation includes power converters of different sizes, distribution panel and the distribution transformer. • Power converters stacked in standard racks. • Small racks containing trimmers can be placed in the tunnel. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  9. Cavern cross-section TE EPC • Two stages of racks can be put in the middle of the cavern, leaving space for the cables and the technicians. • 32m is needed for the converters in the first section cavern and 14m for the last. • Another 4m is needed for the trimmers if they are not in the tunnel. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  10. Cavern cross-section TE EPC Daniel Siemaszko, Serge Pittet - EDMS 1075533

  11. Alternative trimmers control TE EPC • RAD-HARD Trimmers placed close to the magnets with limited precision to 1% (still insuring a current precision of 100ppm in the magnet). • FEAS (CLIC Front End Acq. Sys.) ensures DA and AD conversion. • Need for 4 analogand 4 digital floating signals per CLIC module with a 100Hz rate. • Reference current managed by control unit, distribution references between mains and trimmers. (Consistent saving in cabling cost 25MCHF). Daniel Siemaszko, Serge Pittet - EDMS 1075533

  12. Correctors alternative control TE EPC • Correctors in the caverns using FEAS (CLIC Front End Acq. Sys.). • Fast control loop in the corrector (10kHz/precision 1%). • Slow control loop located over ground (1Hz), high precision (100ppm) allowed with temperature measurement and calibration parameters stored in database. • Need for 1 analog input, 3 analog outputs and 2 digital signals for each corrector. • FEAS with DA and AD converters and 100Hz read-out. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  13. Heat load in the caverns TE EPC • The converters in the caverns are water cooled but still, some heat dissipation to air is to be expected. The ventilation unit in the tunnel must sustain the whole heat load since the converters are in a confined space. • The heat load is estimated with the following assumptions: Converters efficiency of 85%, water cooling efficiency of about 90% and dissipation to air of transformer is 1%. • Heat load to air by transformer and converters: 52kW (down to 40kW). • Heat load to water is about 260kW (down to 200kW), meaning a flow of 3.1l/s(11.2 m3/h) with DT=20° is considered, with a pressure of 6-9 bars. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  14. Heat load in the tunnel TE EPC • Each trimmer dissipates from 1 to 50W. • Total power dissipated by the trimmers in one section: 18kW • Grouped in strings, each of them would dissipate 780W in the tunnel. Grouping in small racks and water cooling of trimmers is compulsory. One might expect some 40W of dissipation to air every 30-60m, depending on the amount of strings. • Power dissipation in power cables is about 15W/m for the drive beam and 20W/m for the main beam assuming 30 magnets strings. • The value of 35W/m is an absolute maximum. This value goes down to 20W/m in the last sector. Daniel Siemaszko, Serge Pittet - EDMS 1075533

  15. Needs in civil engineering TE EPC • Two types of caverns, one with an access lift (8 in total), one with access through tunnel only (40 in total). • The length of the cavern should be enlarged. Dedicated shaft for cables have to be designed. • Power converters in turnarounds would allow to save space in the caverns. However, we have good reasons to believe that radiation level will be too high because of neutron scattering. Radiation levels to be confirmed by simulations. Daniel Siemaszko, Serge Pittet - EDMS 1075533

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