Decision #30 - Maintenance Unit LengthOptions:A. Half the distance between refrigerators ~3km sector B. ~0.5km units (requires: 6 U-tubes or 24 valves at each location)

BCD: ~3Km sector

Pro:1. Minimizes the component count2. Minimizes the heat load.

Con (500m units provide):1. Reduced thermal cycles on CMs. (factor ~5)2. Reduced warm up times (factor >2)3. Reduced cooldown times (factor ~10)4. Reduced He storage (factor ~5)5. Refrigeration load sharing6. Modular “upgrade” elements

ACD: If the component reliability can not be reached; change design to 500m maintenance units.

ACD R&D: 300mm cold valve design: A) cold actuator and B) “slow opening”

Decision #38 - Refrigerator SpacingDrivers: T. Peterson’s presentation ~5km1. 2K temperature (pressure), Gradient, Q, cavity shape & 300 mm pipe diameter determine

the maximum length of the pumping line. 2. Maximum coldbox size 25kW of 4.5 K equivalent

Options:A. Pair of refrigerators at common locations each feeding a ~3.5km sector (Pipe

limited)B. Single larger refrigerator each feeding two ~2.8km sectors (Refr limited)

BCD: Single refrigerator spaced ~5.6km

Pro:1. Option B minimizes the pressure drops in the CM2. This reduces the baseline warm-up unit length.

Con:1. The TESLA design used option A; it permitted an initial half refrigeration installation2. Increases the number of utility systems required: Purifiers, LN2 systems, LHe systems,

GHe systems, ICW, etc

Required task: After the Decisions #3, 10 & 25 etc are chosen the 5.6Km needs to be verified