1 / 22

C ryogenics for cold-powering at LHC P7

C ryogenics for cold-powering at LHC P7. U. Wagner CERN. Topics. B oundary conditions Mechanical Lay-out P rocess Retained cooling circuit Influence on the performance of the existing LHC refrigerators Items do be defined, designed, build and installed Open questions.

marnin
Download Presentation

C ryogenics for cold-powering at LHC P7

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cryogenics for cold-powering at LHC P7 U. Wagner CERN

  2. Topics • Boundary conditions • Mechanical • Lay-out • Process • Retained cooling circuit • Influence on the performance of the existing LHC refrigerators • Items do be defined, designed, build and installed • Open questions 1st HiLumi LHC / LARP

  3. Boundary conditions LHC P7 • Replacement of ARC current feed boxes from LHC tunnel to adistant underground cavern. • ~ 30 kA total current; • ~ 500 m “semi horizontal” SC link line. 1st HiLumi LHC / LARP

  4. Locations I: P7 • Cryogenic supply from existing refrigerators at P6 and P8 • Available fluids for cooling defined by existing infrastructure • Separation of fluids! • No mixing of helium from P6 and P8 refrigerator. 1st HiLumi LHC / LARP

  5. Assumptions • The following assumptions were first formulated in 2010. • They are still the baseline today • Link SC is MgB2 • Splice LTS to MgB2 (magnet to link) requires liquid helium bath. • Max MgB2 temperature 20K • Max. helium temperature 17 K • He consumption for current lead cooling: • As published by A. Ballarino in CERN/AT 2007-5 1st HiLumi LHC / LARP

  6. Helium conditions at interface P7 Worst case considered for study 1st HiLumi LHC / LARP

  7. Transfer line option1: “Flexible” Nexans transfer line • Advantage: • Easier to install; • Potentially allows to install whole length “prefabricated” with MgB2 inside. • Potentially allows to avoid splices on MgB2. • This could be a demonstrator for power lines with interest reaching above the CERN project • Disadvantage: • High heat load; assumed 0.3 W/m cold line; 2.5W/m shield line. 1st HiLumi LHC / LARP

  8. Transfer line option2: Custom made rigid transfer line • Advantage: • Low heat load; assumed 0.04 W/m cold line; 1.5W/m shield line. • These values have been demonstrated for the link line installed in P3. • Allows transfer line with thermal shield supply and return lines. • Disadvantage: • Installation in sections; time consuming; integration of MgB2 will potentially need sections -> splices. • As the consumption on the cryogenic system is relevant for existing installations both options are always compared. 1st HiLumi LHC / LARP

  9. Conclusions from 2011 presentation • For P7, low current case • Heat load on transfer lines defines the cooling flow. • Valid for both TL options. • Flow in excess for current lead cooling is heated to ambient. (“wasted”) • Invest design effort to obtain a transfer line with low heat leak. • Complex custom design transfer line • Shield circuit using 60 K, 18 bar gas (as already realised in P3) 1st HiLumi LHC / LARP

  10. Cost of cooling comparison • Two reference cases • Actual cooling with DFB in the tunnel. • Lower limit. • Reference for comparison as this case does not solve our problem. • LTSC link, as already realised in LHC P3 • Upper limit • Valid reference as possible to implement without any further R&D. 1st HiLumi LHC / LARP

  11. Current Base concept (all sites) • The 17 K limit for the MgB2 link allows only the 5 K, 3.5 bar helium from line C as coolant. • The link will be cooled by helium gas created by evaporating the liquid helium in the spice box. • Thermal shield solution not shown. • Either with 20 K, or with 70 K gas. Helium at max. 17 K Helium from line C 1st HiLumi LHC / LARP

  12. Studied cooling options • In total eight different cooling options were studied • The three most relevant are listed below • “Nexans like” line: • Shield cooling with 20 K gas. • Custom line: • Shield cooling with 20 K gas. • Shield cooling70 K gas and cold return line. 1st HiLumi LHC / LARP

  13. Cooling methods sketch Shield cooling with 20 K gas Nexans and Custom Shield cooling with 70 K gas Custom only 1st HiLumi LHC / LARP

  14. Comparison of cooling methods Values without uncertainty / overcapacity margin Requires TL with three cold lines, discarded for MgB2 as only minor advantage. Kept in mind if integration of Nexans line impossible. Reference . 1st HiLumi LHC / LARP

  15. Equipment modifications • Modify DFBM • Include a link from DFBM to DFBA for the 4 x 600 A leads • (either NbTi or MgB2) • Modify DFBA • Including the “Splice box” and the 13 kA leads for power extraction. • Possibly, but not necessarily with a modified jumper from the QRL 1st HiLumi LHC / LARP

  16. Modified tunnel DFB 1st HiLumi LHC / LARP

  17. Additional equipment • Two link cryostats • Transfer line with shield cooling and integrated MgB2 conductor. • Two new cavern DFB’s • (may be in one cryostat but with separation of the hydraulic circuits) • Two warm lines DN80 • From cavern DFB to helium ring line. 1st HiLumi LHC / LARP

  18. Cavern DFB (principle flow scheme) 1st HiLumi LHC / LARP

  19. Uncertainties as of last year • MgB2 performance and detailed requirements. • Progress has been made, we may consider this a minor uncertainty. • Lead performance and detailed requirements. • Can we assume that the lead performs close to what was published for the LHC lead? • Transfer line design (link cryostat) • Uncertainty remains, less for design but for realisation. 1st HiLumi LHC / LARP

  20. Uncertainties and recommendations 2013 • Nexans like transfer line • Desire to preassemble 500 m of “semi rigid” line with MgB2 conductor. • Handling the preassembled length? • Pulling the conductor without breaking it may be a major challenge! • Alternative: produce the line at the supplier with the MgB2 included; i.e. wind the line around the conductor. • This was quoted by Nexans as possible. • A demonstrator would be needed before any decision. • To be considered when in the project stage to include this approach. 1st HiLumi LHC / LARP

  21. Uncertainties and recommendations 2013 • Any other than the integrated 500 m design might require MgB2 to MgB2 splices in helium gas. • At least a demonstrator that this can be feasible should be developed. • Basically:if we can link MgB2 to HTS at 17K one should be able to realise a link at lower temperature. • The total pressure difference for the 20 K gas between supply and return is only about 150 mbar • The pressure loss budget at the moment is: • 50 mbar in the link line, 50 mbar in the DFB heater, 50 mbar in the return line. • The connection between Q6 (DFBM) and the main link line. 1st HiLumi LHC / LARP

  22. Conclusion 2013 • We are certain that we can supply the cooling for the current feed boxes and the corresponding superconducting link. • We do know sufficiently well what and how we will cool. • In short: • We know what we want to do and we know that we can do it. • But we still need to get a clear idea about the details. 1st HiLumi LHC / LARP

More Related