TDR Cryogenics Parameters Tom Peterson 28 September 2011

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 2 Heat loads Static heat loads from cryomodule design –We have updates from S1-G Other sources of heat –Transfer lines –Magnets –Unique cryomodules in low energy regions Dynamic heat loads from beam, cavity, and RF parameters –RF scheme, pulse length, rep rate –Cavity performance (Q0, gradient) –HOM absorber strategies Heaters for dynamic load leveling and compensation Control margin Uncertainty

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 3 Main linac dominates ILC cryogenics but there is more... The main linac cryoplants and associated equipment make up about 60% of total ILC cryogenic system costs Main linac distribution is another 20% of total ILC cryogenic system costs –About half of that is 132 string connecting boxes Total is about 80% of ILC cryogenic system costs attributable to the main linac Also have Beam Delivery System, RTML, electron and positron sources

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 4 Major cryogenic distribution components - RDR 6 large (2 K system) tunnel service or “distribution” boxes –Connect refrigerators to tunnel components and allow for sharing load between paired refrigerators 20 large (2 K) tunnel cryogenic unit “feed” boxes –Terminate and/or cross-connect the 10 cryogenic units ~132 large (2 K) string “connecting” or string “end” boxes of several types –Contain valves, heaters, liquid collection vessels, instrumentation, vacuum breaks –Note that these have many features of modules! ~3 km of large transfer lines (including 2 Kelvin lines) ~100 “U-tubes” (removable transfer lines) Damping rings are two 4.5 K systems –Various distribution boxes and ~7 km of small transfer lines BDS and sources include transfer lines to isolated components Various special end boxes for isolated SC devices

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 5 Allocation of cryogenic plants Iterative with beam dynamics design, facilities design, and cryogenic plant design Some freedom to extend cryomodule string lengths Some freedom to place refrigerators and/or compressors away from feed box locations –Room temperature pipes from compressors –Cold transfer lines at 20 K or 4.5 K

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 6 ILC RF cryomodule count Above are installed numbers, not counting uninstalled spares

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 7 A cryogenic “string”

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 8 RDR Main Linac Layout - 1

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 9 RDR Main Linac Layout - 2

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters configuration (not in RDR)

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 11 RDR cryogenic plant arrangement

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 12 CERN LHC capacity multipliers We have adopted a modified version of the LHC cryogenic capacity formulation for ILC Cryo capacity = Fo x (Qd x Fud + Qs x Fus) –Fo is overcapacity for control and off-design or off-optimum operation –Qs is predicted static heat load –Fus is uncertainty factor static heat load estimate –Fud is uncertainty factor dynamic heat load estimate –Qd is predicted dynamic heat load

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 13 Cryogenic Unit Summary

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 14 Input parameters for 5+5 Hz RF pulse length = 2180 microseconds from SFUKUDA DRFS2.ppt slide 11 bin C 16/26 active cavities per RF unit all cavities active at low gradient RF pulse lengths from CryoPower-PHG-12jan2011.xls

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 15 Heat loads and cryoplant power The largest standard cryoplant based on heat exchanger sizes and transportation limits would be roughly 5.5 MW.

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 16 DRFS LE option -- all cavities, low gradient

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 17 DRFS LE option -- 60% cavities, high gradient

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 18 How long can a cryogenic unit be? The ILC RDR cryogenic units were considered to be limited by –Standard industrial cryogenic plant size. 4.5 K capacity of about 25 kW, a bit larger than LHC plants, is considered a limit for a single plant due to heat exchanger braze furnace sizes –Cold compressor capacity. Largest cold compressors provide about 4 kW at 2.0 K –Pressure drop through the 300 mm pipe. 3 mbar pressure drop starts to result in significant temperature rises at the high pressure end and significant lost refrigeration capacity

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 19 Cryomodule Pipe Sizing Criteria Heat transport from cavity to 2-phase pipe –1 Watt/sq.cm. is a conservative rule Two phase pipe size –5 meters/sec vapor “speed limit” over liquid –Not smaller than nozzle from helium vessel Gas return pipe (also serves as the support pipe) –Pressure drop < 10% of total pressure in normal operation –Support structure considerations Loss of vacuum venting P < cold MAWP at cavity –Path includes nozzle from helium vessel, 2-phase pipe, may include gas return pipe, and any external vent lines

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 20 Maximum allowable pressures Helium vessel, 2 phase pipe, 300 mm header –2 bar warm Limited by cavity detuning Issue for pushing warm-up and cool-down flows –4 bar cold Limited by cavity detuning Issue for emergency venting Shield pipes –20 bar Need high pressure for density to reduce flow velocities and pressure drops

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 21 Factors limiting flow distance Pressure drop plot assumes: –2.0 K saturated vapor flow –12 Watts per cryomodule x the 1.54 uncertainty and overcapacity factor, so flow matches that assumed for the refrigerator. (This factor is only used once.) –So 0.92 grams/sec of helium are added per cryomodule. At cryomodule #250 the pressure drop of 2.8 mbar corresponds to about 30 mK temperature rise –Pressure drop "taking off” and approx. 3 mbar –Secondary effect of warmer cryomodules and lower Q comes into play. Conclusion: we can safely go up to cavity cryomodules in a cryogenic unit, running in series. –We had nominally cavity cryomodules in the cryo system design, so this is a 250/192 = 30% longer cryogenic unit than the average for the ILC RDR work.

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 22

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 23 Remote compressor location -1 Estimate compressor flow for the three typical pressure levels of the large room-temperature compressor system

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 24 Remote compressor location -2 Given the estimated total compressor flow rates for one refrigerator from the previous slide, calculate pipe sizes required for a reasonably low pressure drop over a long distance.

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 25 Remote compressor location -3 Given the estimated total compressor flow rates from the previous slide, multiplied by 5 for 5 refrigerators, calculate pipe sizes required for a reasonably low pressure drop over a long distance.

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 26 Conclusions - 1 Primary input parameters for cryogenic system design include –Static and dynamic heat loads, which come from cryomodule design, beam dynamics, RF, and magnets –Allocation of cryogenic plants, which comes from lattice design, facilities engineering layout, cryogenic plant limitations, and site-specific issues Uncertainty and overcapacity factors are a requirement in order to build a working system –One can quantify these with information about cavity performance spread and degredation and more detailed concepts for cryogenic system control strategies

28 Sep 2011 Tom Peterson TDR Cryogenics Parameters 27 Conclusions - 2 ILC cryogenic system parameters allow some flexibility –Cryogenic unit length is flexible up to about 250 cryomodules, 30% more than the 192 in the longest RDR cryogenic unit –Compressors may be located some distance from the refrigerator with room-temperature piping connections