Cooling: CEDAR PMT & Electronics Tim Jones Liverpool Group

Overview Cooling System Parameters – Estimate Power Loads Active components Extraneous heat sources – Develop methodology for exploring cooling system parameter space Flow rate Pressure drop Pipe bores Control and Monitoring – Strategies – Implementation 15/03/20112PMT Array Cooling

Cooling System Parameters Working document - “Specifications for the Cooling System for the NA62 CEDAR Kaon Tagger” Considers 2 sides as being separate sub-systems – Chiller/Heater – Interconnect pipe-work – Internal pipe-work, etc.. System specification driven from a desired inlet- to-outlet bulk temperature rise 15/03/20113PMT Array Cooling

Considerations Desired temperature rise and total power defines the mass-flow; – 1g/s cools 4.2W for 1  C Mass flow, density and tube bore defines volume flow and velocity. Velocity defines Reynolds Number. Reynolds Number defines pressure drop and HTC HTC defines tube wall temperature 15/03/20114PMT Array Cooling

Power Estimate (half unit) FE – 32 PMTs per array – 4 arrays per cooling circuit connected in series – 0.5W per PMT – 16W per PMT array, 64W for four arrays on one side Environment – Box dimensions 1.2(h) x 0.6(w) x 0.3(d). Area of 5 sides = 2.16sq.m – Box insulation k=0.05 W.m -1.K -1 – Wall thickness 50mm – Assume external wall is at 30  C and internal wall is at 20  C – Power = 0.05 x 2.16 x 10 / 0.05 = 22W Total Power – 64 (FE) + 22(env) = 86W[Round this to 100W cooling power] 15/03/20115PMT Array Cooling

Pipe-work Geometry External Interconnect – Flow and return lines 7m long with a bore of 12mm Internal – Heat exchanger: heated length 0.5m per array – Interconnect: 4m in total – Bore: sensible choices might be 4, 6, or 8mm 15/03/20116PMT Array Cooling

System Properties Volume Flow – Inversely proportional to desired temperature rise – Independent of tube bore – Flow = 1.54/  T lpm 15/03/20117PMT Array Cooling

System Properties Pressure Drop – Depends on fluid velocity (strong dependence on tube bore) 15/03/20118PMT Array Cooling

Draft Chiller Requirements T rise0.5deg C0.25deg C0.10 deg C Bore4mm6mm8mm4mm6mm8mm4mm6mm8mm Flow Pressure Tabulate Flow and pressure for different bores of the internal pipe work and desired temperature rise Chiller Specifications (preliminary web-trawl) ModelPowerFlow 0 bar)Pressure (bar) Fryka DLK  C Grant RC350G 20  C lpm) Neslab Thermoflex 900/P2 40  C 12.5 bar)7 bar Jubalo FC600S 20  C Cole-parmer WU  C Lauda WK 20  C10 15/03/20119PMT Array Cooling

Chiller Parameters Cooling Specification – Cooling Power (W) – Flow Rate (lpm) – Maximum Pressure (bar) Control – Set-point stability – Heater Power (W) – PID / remote control – Control Temperature (internal / external) Alarm signal (low flow, low level, ….) 15/03/201110PMT Array Cooling

Monitoring DCS Monitoring – ELMB (ATLAS) – quote from ELMB128 User Guide “It should be usable in USA15 outside of the calorimeter in the area of the MDTs and further out. This implies tolerance (with safety factors) to radiation up to about 5 Gy and 3·10 10 neutrons/cm2 for a period of 10 years and to a magnetic field up to 1.5 T.” Automated reading, archival & presentation in central DCS – Inputs 128 floating input (2 wire) channels Can be configured for DCV, Ohms… Can be used in pairs for 4-wire RTD (PT100) DSS – Detector Safety System High level alarms relating to safety ONLY Independent of DCS 15/03/201111PMT Array Cooling

Control Issues – Maintain the PMT arrays at a given temperature – Minimise the heat transfer between the box and the CEDAR Options 1.Monitor the temperature of the PMT array and manually adjust the set point of the cooling unit so that the global temperature of the electronics box is close to the CEDAR (hydrogen). Provide sufficient thermal insulation to minimise coupling between box and CEDAR. 2.Additionally, control the temperature of the cooling fluid using a feedback loop such that the temperature difference between the electronics box and the CEDAR is minimised. Provide sufficient thermal insulation to minimise coupling between box and CEDAR (hydrogen). 15/03/201112PMT Array Cooling

Thermal Interfaces Heat Paths – Nitrogen enclosure/beam pipe/CEDAR – Environment/Support Tube/CEDAR – Environment/beam pipe/CEDAR 15/03/201113PMT Array Cooling

Option 1 15/03/201114PMT Array Cooling

Option 2 15/03/201115PMT Array Cooling

Comments Option 1: – Likely to need greatest number of interventions to adjust Chiller PID controller – Needs Chiller with in-built heater – Needs high precision chiller set-point & stability Option 2: – Highest cooling power requirement – Need to develop fault tolerant PLC /heater sub-system We would most likely implement option 1 first as a prototype system before moving to option 2 15/03/2011PMT Array Cooling16

Further Thoughts about the Nitrogen Enclosure We want to optimise the nitrogen enclosure as follows: – Separate the 8 octants to enable the electronics in each to be accessed without compromising the nitrogen environment of the others; – Separate nitrogen feeds to each to enable faster flushing; – Minimise outlets to reduce sealing and gas-leakage problems by routing cooling pipe-work externally; – Assure a nitrogen atmosphere close to the quartz windows. We envisage a cylinder, coaxial with the beampipe, as part of the support structure, with gas flow to the enclosures surrounding electronics in each octant. All will be enclosed within an insulated, protective cover. 15/03/2011PMT Array Cooling17

15/03/2011PMT Array Cooling18