Cryomodule Development Status Prashant Khare, Shailesh Gilankar Pradeep Kush, Rupul Ghosh Abhishek Jain, A. Laxminarayanan, Rajeev Chaube

PART -A

Some Queries on Previous Presentations Should we increase the static heat load figure in light of SNS cryomodule “U tube” figures of 10W. The power coupler heat leak in, is a bit higher than Tesla type power coupler ILC =0.06W, SNS =0.7 and 0.9 W ours is =0.152 May we have a copy of Power coupler heat from PX_couplers_ref_2.pdf by Sergey Kazakov Support post heat in leak is mentioned as 0.41W. But ILC type support post says 2.4Watts per CM i.e.0.8 Watts. A very minor issue. With standalone cryomodule is there a case under study where there are just 4 cavities in cryomodule. In that case static heat load per cryomodule will be still higher. Some Queries on Previous Presentations

Reference Sheet -1

A Static heat leak averaged over 5 cryomodules Reference Sheet -2

 High Beta Cryomodule  LHC concept of producing the 2 K in the CM rather than in the refrigerator is utilized. Spallation Neutron Source 6.3 m Cryomodule of JLab Reference Sheet -3

SNS Calculated Heat Load (watt) For Medium and High Beta Cryomodule Reference Sheet -4

Worst caseOther heatWorst caseuncertaintyWorst caseRiser areaRiser dia 30 degree angle dynamicper cavitytotalfactortotal heatrequired so take 1.3 cavity heat**cavity heatfor pipeincluding Fu with 1 W/cm2 factor (W) sizing -- Fu(W)(cm2)(cm) SSR SSR SSR MHz (beta = 0.61) MHz (beta = 0.91) GHz  Pls let us know how 1.3 factor is connected with 30 degree angle. Why heat carrying capacity has been now recalculated as chimney is inclined at by 30 .  Cross Sectional area for conducted heat flux will be perpendicular to flow path. One More Query on Previous Presentations

Probably it is 9.5cm Select Total mass minimum (4.0 bar) thermal shield Thermal shield flow perheliumHelium trace tube Reynold sFrictiontrace tube Cryomodulesegmentdensity viscosit y inner diameterflow area wetted perimeter hydraulic radiusnumberfactor total length pressure drop (g/s)(g/cc)(g/cm-s)(cm)(cm 2 )(cm) (m)(bar) SSR E E SSR E E B. Probably Hyd radius is 0.79 cm (2 x Free Flow area/perimeter) Small typographical errors ? A.

One More question About 2Phase pipe- Can we have this configuration finalized. It is Tesla type and can have stand alone feature too. 300mm pipe (St. steel) He 2-Phase pipe (Ti) Temp. shrinkage Compensator Can we support the pipe on the shape, connect with chimney in vertical fashion, which is a bellow. So that we do not have to accommodate such a big bend in two planes.

Page 11 48” vacuum vessel pipe 300 mm pipe 80K shield, pipes: (Nom: 35mm-ID) Warm up-cool down pipe (nom 25mm ID) 4K return pipe (nom 25mm ID) 2-Phase pipe (161mm-ID) 80K Return pipe 4K Return pipe (?) X-Y Section 1. We were targeting to reduce the diameter to 42inches 2. Can we put the 2K line inside “The No more HGR pipe”. 3. What could be the problem if 4K return line is used to Cool the HGR line

Possible layout of 2 K two phase pipe Cross section of possible configuration (with 2-phase helium pipe inside 300 mm supporting pipe) Flexible Chimney from Cavity helium vessel 300 mm Support Pipe ultimately supported by support posts Numbers of rollers (can be spring loaded) 2K two-phase He II line

PART -B

Thermal Shield :Steady state Analysis Boundary Conditions 1. Room Temp= 300K 2. Fluid Temp 70 K (No variation assumed along the pipe) 3. Value of h~ 200W/mk 4. Mass flow rate of helium 24gm/sec 5. Pressure drop <3mbar 6. Pipe Dia =50mm 7. Press drop <3mbar with 15mm dia pipe also

Different look at problem of heat transfer from trace line 70 K thermal shield Limited heat transfer area from pipe to thermal shield, even if pipe diameter of radiation shield is changed to improve convective heat transfer keeping total  P within limit of allowable pressure drop Can we go for different cross section instead of circular may be shape like semi-circular, rectangular for equivalent hydraulic diameter ? Instead of this These Cross sections?

Cavity Support System Max  Max VM  HGR Pipe Max VM  Hangers LC10.13 mm10 MPa LC mm35 MPa LC mm20 MPa10 MPa LC mm20 MPa17 MPa LC1 :Self Weight LC2: Self Weight +Cavity Load LC3: Self Weight + Cavity Load + Cooldown LC4: Self Weight + Cavity Load + 4 bar pressure + Cooldown

“Vacuum Loss” important heat flux data! Loss of vacuum to air  “ 3.8 W/sq.cm. for an un-insulated tank of a bath cryostat”  “0.6 W/sq.cm. for the superinsulated tank of a bath cryostat ” Given in “ Safety Aspects for the LHe Cryostats and LHe Containers,” by W. Lehman and G. Zahn, ICEC7, London, 1978 “Loss of cavity vacuum experiment at CEBAF,” by M. Wiseman, et. al., 1993 CEC, Advances Vol. 39A, pg 997.  Maximum sustained heat flux of 2.0 W/sq.cm. LEP tests and others have given comparable (2.0 to 3.8 W/sq.cm.) or lower heat fluxes ( Referred from slide of ILC presentation “Cryostat/Cryogenics Summary and (Proposed) Conclusions” on 25 April 2008 by Tom Peterson) Are you planning to perform Crash tests for new 650 MHz Cavity design? on similar line of CMTB at DESY (for 1.3GHz cavity) and CEBAF  Establish accidental vacuum loss condition heat flux data and MAWPS OR  Should we simulate it on ANSYS so that pipe sizes can be calculated.

Initial work for emergency venting calculations for cavity vacuum loss

Loss of Cavity Vacuum Emergency Venting Calculations of β= MHz Cavities For venting calculations;  5 inch size taken for emergency venting of helium for 2-phase/ gas return helium pipe  Venting temperature at bar MAWP is 5 K through 2-phase /HGR pipe considering max. f(T)= sqrt(v)/v(  h/  v)  Helium enthalpy is taken at above T, P conditons.  Reference density at above temperature and pressure taken for pressure drop calculations assuming a near isothermal flow condition  Conservatively higher value of f ~ 0.02 for friction factor considered.  Sonic condition is limit for flow rate

Venting Calculations 650 MHz assumptions  1.8 K helium cooling (~16 mbar)  33.6 W/cavity total heat  Includes one-time safety factor = 1.5 on heat/flow  So 33.6 W per cavity (in steady state analysis)  Cavity slot length = 1.4 m (From FNAL) (For calculating pipe lengths as function of number of cavities)  Cavity cold MAWP = ? but 2.5 bar (assumed)  Cavity surface area = 15,000 cm2  Single Vapor /2-phase pipe or separate /2-phase pipe ?  Only one connection from 2-phase to HGR pipe

For a ~ 3-inch diameter opening, air flow becomes the limiting factor in heat deposition after a few cavities in a cryomodule.

Tom Peterson -- Cryomodules 650 MHz cryo schematic

1) Higher heat transfer rates than for 2-phase, at higher flow rates, 2) No danger of sudden decrease in heat transfer rate, such as boiling 2 phase helium at CHF, 3) No flow instabilities as in 2- phase 4) Operating temperature can be optimized over a wider range and 5) Pressure drops are lower. 1) Near isothermal conditions obtainable from inlet to outlet 2) Smaller flow rate required to remove the same heat load due to use of latent heat of evaporation. Advantages of supercritical heliumAdvantages of 2- phase helium Supercritical helium Vs 2-phase helium for 4-5 K intercept  What is crucial? Isothermal condition or pressure drop ?  Standalone ?

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