Mathew C. Wright October 2016 Cryogenic Cooling Mathew C. Wright October 2016

Cryogenic Operations Overview 11/12/2018

Cryogenic Cooldowns Types of Cryogenic Cool Downs: Using LN2 to cool down Cold Boxes Using 4K helium to cool down cryo modules Using LN2 HX to cool helium to cool magnets Mixing 300K helium with 4K helium Using Turbines to cool down cold boxes before LN2 Directly injecting LN2 into helium dewars then finishing the cool down with 4K helium

Cryogenic Cooldowns Things to be concerned about: Thermo-mechanical stresses of the components Especially heat exchangers Oil or contamination migration Capacity Limitations of the Equipment Refrigeration Helium Recovery / Purification Gas Management

Cryogenic Cooldowns Basic Rule: Cooling provided by the supply stream must be greater than that absorbed by return stream – rest of the cooling is used to cool down the equipment (HX etc.). This imbalance across the two streams is created by the bypass flow.

More strain = More Stress! Cryogenic Cooldowns Concerns: To reduce thermo-mechanical stresses of the components Normally Delta T less than 50K Thermal strain (i.e. contraction rate) is directly proportional to ∆T. More strain = More Stress! Cool down rate is less than 1K/min

Cryogenic Cooldowns Concerns To reduce Thermo-mechanical stresses of the components Delta T less than 50K Here, ∆T is the temperature difference between the streams at warm end or at the cold end.

Cryogenic Cooldowns Concerns To reduce Thermo-mechanical stresses of the components Flow through all HX passes should be low, causing the Cooldown to be extremely slow

Cryogenic Cooldowns Concerns Contamination migration Loads / Cryogenic Vessels: Always assumed Dirty. Entire cool down flow is taken to recovery system (via. Vaporizer). This also creates flow imbalance across HX. Cold Box Adsorbed Beds: Isolated/Bypassed until the process flow reaches the temperature they are meant to operate (i.e. 80K/20K). If possible they should be cooled separately (using same method as 1).

Cryogenic Cooldowns Basic Rules Oil or contamination migration Start Cool Downs of all Cold boxes w/ LN2 Check outlet vent to ensure the LN2 supply valve is only cracked open Use a bag over the vent pipe and crack open the valve until the bag starts to slowly inflate Cold box 80K carbon beds are 100K or less before starting turbines to reduce the chance of contamination getting down stream when turbines are started

Cryogenic Operations Overview 11/12/2018

Cryogenic Cooldowns CHL1 Direct LN2 injection

Cryogenic Cooldowns CHL1 Direct LN2 injection

Cryogenic Cooldowns Jlab Style Cryo Module Cool Down Direct 4K injection

Cryogenic Cooldowns Jlab Style Cryo Module Cool Down

Cryogenic Cooldowns Both LINAC’s can be supported by either CHL1 and CHL2 without having to warm-up any cryo modules Modules typically have to be warmed up for maintenance on the module

Solenoid in Hall D Bore 4m long 2m diameter Field at the axis ~ 2T at 1350A Full energy ~ 23 MJ at 1350A 4 coils in 4 separate He baths Built at SLAC in 1970’s, refurbished at IUCF and Jlab Total helium reservoirs 3500 liters

Cryogenic Operations Overview 11/12/2018

Cryogenic Cooldowns Hall D: Employing cool-down heat exchangers

Cryogenic Cooldowns Employing cool-down heat exchangers

Cryogenic Cooldowns Hall D: Employing cool-down heat exchangers

Cryogenic Operations Overview 11/12/2018

Cryogenic Cooldowns Hall A: Employing cool-down heat exchangers

Cryogenic Cooldowns Other Cool Down Methods Mixing 300K w/ 4K helium Uses 4K capacity when LN2 could be used Flow may need to be limited based on Size of the Recovery system Size of the Refrigerator Warm (300K) start-up of turbines Concern is that the 80K carbon beds are not cold and that contamination will migrate to the turbines Cool Down with LN2 directly into the process Rumors of people using LN2 directly injected into a helium dewar to cool down, then pump out the N2, and continue cooling with helium Concerned amount contamination If there are valves back to the helium system, concerned those valves leak and that the helium system has to be shut down to clean it up.

Cryogenic Operations Overview 11/12/2018

Cryogenic Operations Overview 11/12/2018