ESS Cryogenic Distribution System for the Elliptical Linac MBL/HBL - CDS requirements Preliminary Design Review Meeting, 20 May 2015, ESS, Lund, Sweden J. Polinski

CDS-HBL-L4-010 The CDS for the elliptical linac (HBL and MBL) shall consist of a four-channeled vacuum- insulated cryogenic transfer line and cryogenic distribution line as well as four auxiliary process lines. The cryogenic distribution line shall include 30 valve boxes (21 for high beta cryomodules and 9 for medium beta cryomodules) CTL Aux. Lines Valve Box

CDS-HBL-L4-010 The CDS for the elliptical linac (HBL and MBL) shall consist of a four-channeled vacuum- insulated cryogenic transfer line and cryogenic distribution line as well as four auxiliary process. The cryogenic distribution line shall include 30 valve boxes (21 for high beta cryomodules and 9 for medium beta cryomodules) CTL Cold Box - ACCP

CDS-HBL-L The CDS for the elliptical linac shall allow for warming up and cooling down a single cryomodule, while keeping the rest of the system at cryogenic temperatures. 1.Usage of the CV05 and the CV62 valve for providing the warm helium during warm-up phase of the single CM 2.Usage of the CV06 and the CV63 valve for by- passing the helium vapor/gas return during warm-up and cool-down phases of the single CM

CDS-HBL-L The CDS valve box shall allow for transferring the required cooling power from the main headers to the cryomodule. 1.Requirement of the specific helium flow (up to 130 g/s) at the inlet to the CDS MC line from the ACCP side - ACCP-CDS-L4-070, 2.Limitation of the heat flux to the CDS MC process line by thermo- mechanical optimization of the pipe supports design and thermal insulation system design, 3.Specified helium mass flow from the CDL to the CM – 6.6 g/s for cooling down, 3.3 g/s for nominal operation 4.Requirement of the max. temperature in the BC Line as 5.2K – CDS-HBL-L4-050

CDS-HBL-L The CDS valve box shall allow for separating a related cryomodule from the cryogenic distribution line. 1.Dismountable design of the jumper connection, 2.Using of the cut- off valve at the lines connecting the CDS with the CM, 3. Application of the vacuum barrier in the jumper connection.

CDS-HBL-L Maximum temperature in the helium supply main and branch lines shall not exceed 5.2 K 1.Requirement of 4.5K temperature helium inlet to the He Supply line from the ACCP side ACCP-CDS-L Limitation of the heat flux to the CDS MC process line by the mechanical optimization of the pipe support system, 3.Thermo-mechanical optimization of the supports design and appropriate thermal insulation system design. 4.Requirement of the specific helium flow at the inlet to the CDS MC line from the ACCP side.

CDS-HBL-L , 070, 080, 090 Maximum allowable heat loads to the helium supply line including the main header and side pipes shall not be higher than 81.4 W Maximum allowable heat loads to the Very Low Pressure (VLP) line including the main header and side pipes shall not be higher than W Maximum allowable heat loads to the Thermal Shield (TS) supply line including the main header and side pipes shall not be higher than 42.7 W Maximum allowable heat loads to the Thermal Shield (TS) return line including main headers and side pipes shall not be higher than 2282 W See separate presentation

CDS-HBL-L4-100 Maximum allowable pressure drop in the Very Low Pressure (VLP) line including the main header and side pipes shall be not higher than 2.0 mbar at the total flow rate of 113 g/s at 28 mbar of operating pressure and 4.0 K of average operating temperature Calculation of the required cross-section area (diameter) of the VLP line with respect of allowed flow pressure drop.

CDS-HBL-L4-100 q m from SPK – 26 g/s q m from each CM – 2.9 g/s T in – 4.0K p out – 28 mabr CDL VLP size – DN200 CTL VLP size – DN250

CDS-HBL-L4-110, 120 The helium leak rate across the valve seat of each process valve shall not exceed 1*10E-4 mbar*l/sec at design pressure and room temperature against vacuum The helium leak rate across the valve seat of each safety valve shall not exceed 1*10E-4 mbar*l/sec at operating pressure and room temperature against ambient pressure He leak test certificate from the manufacturer

CDS-HBL-L4-130 All materials and components of the CDL placed in the linac tunnel shall tolerate the radiation dose of 5*10E5 Gy. 1.Appropriate material selection, 2.Teflon will be avoided, 3.The EDPM rubber gasket will be used for the warm vacuum flange connections

CDS-HBL-L4-140 Under cryogenic operating conditions, the measured integral helium leak rate into the insulation vacuum shall not exceed 5*10E-7 mbar*l/sec 1.Appropriate welding technique, 2.Non-destructive (X-ray, leak tightness) test after the weld realization

CDS-HBL-L4-150 Insulation vacuum pressure at ambient temperature with active pumping shall be not higher than 5*10E-3 mbar after a pumping time not longer than 96 hours 1.The CDS line supports design with respect of the gas molecular flow resistance lowering, 2.Selection of the main vacuum pump appropriative pumping speed, 3.Using the temporary vacuum pumps, if necessary, 4.Collaboration with ESS vacuum group in this task is agreed.