35T experience with Cryo Measurements and CFD Alan Hahn FNAL 8/15/18 1
35 Ton Prototype Cryostat HV Field Cage Test Installation 8/15/18 2
Cryo Operations • Use LAPD Cryostat as a storage Dewar for LAr Deliveries from vendor • LAPD can supply 35T with ~70% of needed LAr • One last vendor delivery into LAr Trailer and then directly into 35 Ton. • All LAr into 35T passes first through filtration system • Measurements with inline Purity Monitor during this fill show the filtered LAr to have e - lifetimes in ~30 ms range—very pure) • Normal 35 Ton operation circulates the LAr from 35T cryostat, to filtration and back to 35 Ton. • ~2.5 volumes/day (~10 gal/minute) 35Ton and LAPD at PC4 8/15/18 3
35 Ton Operations 5 runs of ~2-3 months/run • First Run (2013-4)—Cryo demonstration that Membrane cryostat could attain TPC quality LAr using Purge/Recirculation technique pioneered by LAPD • Cryo Instrumentation (all recycled from LAPD ) • Purity Monitors (PrM) 4 in Cryostat, 1 “inline” just after LAr filters • RTD Spooler– 3 RTDs on pcb that could be lowered and raised in cryostat • Gas Analyzers • Second Run (2015-16)– Installed reduced-scale version of LBNE TPC • Cryo Instrumentation • RTD Spooler replaced with 4 fixed RTDs mounted on top face of PrMs in cryostat • No room for RTD Spooler with TPC & HV grabbing most ports on cryostat • Third-Fifth runs (2017-18) were HV tests of the ProtoDUNE Field Cage and Beam Plug • Cryo Instrumentation basically same as Second Run. 8/15/18 4
Run 1 RTD Spooler Measurements of Cryostat Temperature Profile 35T RTDs were/are not Calibrated absolutely. 8/15/18 5
Run 2: Immediately Notice PrM Lifetimes begin to diverge as function of height after LAr pump start and purification of liquid begins. PrM 1 (near Cryostat bottom) PrM 4 (near surface) O2 Gas Analyzer, ~(~80 cm from bottom) 8/15/18 6
Unscheduled (Friday night!) Power Outage (and pump off) provides opportunity to cross-check the different PrMs—and verify that with pump on, the Lifetime diverges as a function of height in LAr T a k e a d v a n t a g e LAr Pump re-started o f p r o b l PrM1 (Bottom)& PrM4 (top) now track!! e m s ! PrM1 & PrM4 (top) now diverge!! O2 from GA also is rising 8/15/18 7
Erik Voirin made new 35 Ton CFD calculations to see if he can match this stratification Dune DocDb 1156 Pump outflow 4 purity monitors in this corner (Geometry Not in CFD model) PrM1 Pump intake 8/15/18 8
New constraint Di Discus ussion n of Resul ults Phase separator (removes Argon bubbles from returning purified LAr) cools inlet flow to approach saturation temperature, which is below the “bulk temperature” of the argon. This cooler, more dense layer of argon tends to stay at the bottom, and not mix well with the rest of the argon. Recall RTD Spooler plot Pump Discharge Pipe with Phase Separator on Top, LAr flows down, and impinges on cryostat floor. Pump Suction RTD measurements next slide verifies this temperature stratification 8/15/18 9
Erik V. prediction that the temperature is stratified checks out using the “precision” RTDs mounted on the PrM top plates (1 RTD 12 hrs after Outage of the 4 was not functional). Pump is on Pump is off 20 mK Barometric Pressure ~ 4 ms 3 RTD offsets adjusted to match Uppermost RTD during this period ~ 2.4 ms PrM 1&4 show Lowest RTD same lifetime PrM 1&4 lifetimes diverge (not adjusted!) 8/15/18 10
Comparison of Measurements to CFD Model. Impressive overall agreement with measured lifetime values. Purity Monitor geometries are not in CFD model, 5” diameter cylinders with porous mesh on sides. These could influence the Impurity distribution near the top as the Vertical pump pipe does, which shows a sharp gradient near at the top purity monitor. Purity Monitors span up to 2 feet in elevation, but give a single value for electron lifetime. Slide from DocDB 1156 Erik Voirin 35 Ton Impurity/Lifetime Measurements and CFD Simulation 11
35 T HV runs –opportunity to verify CFD • Since the prediction was that the return LAr was colder than the bulk liquid, we decided to change the location of the return from the bottom of the cryostat to a location ~ ¾ the height of the LAr level. • So colder LAr should now better mix with bulk LAr • Also installed three more “precision” RTDs • For this issue, important one is in the LAr return outlet (or inlet in ProtoDune terms) • See E/ Voirons calculations, 35T photos next two slides • Results follow on third slide 8/15/18 12
35 Ton Phase Separator Modified LAr Return Boiling LAr enters Nominal LAr surface GAr out Phase separator LAr out LAr out New RTD 8/15/18 13
Result 1: Much Better Vertical Mixing than Bottom Discharge Erik Voirin 35 Ton Impurity/Lifetime Measurements and CFD Simulation 14
Results from HV Run– verify LAr return T is lower than bulk LAr Note PrM RTDs do not diverge as before Pump on LAr return outlet RTD 8/15/18 15
Suggested ProtoDune Cryo measurements • Monitor Temperature and PrM profiles during turn on of LAr pump. • Pump off might be interesting for CFD • Change of temperature profile and PrM lifetime profiles may be easier to check in CDF than absolute values. • Certainly establish Temperature profile • Note that surface T can be measured by level rising past a fixed RTD location. See following slide • Monitor LAr inlet temperatures (ProtoDune notation!) • Suggested to monitor temperature profiles if APA FE Electronics turned on/off • However, in ProtoDune, the electronics are all mounted on the top of APA, so not sure if this will make an impact or not on Temperature monitors. 8/15/18 16
Extra Slide RTD drop as LAr surface falls across RTD (emptying 35T Cryostat) http://dbweb5.fnal.gov:8080/ECL/dune_35t/E/show?e=10453 In Vapor In LAr Surface Layer 8/15/18 17 Time
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