GTK GAS COOLING SYSTEM Marco Statera, Vittore Carassiti, Ferruccio Petrucci, Luca Landi, Stefano Chiozzi, Manuel Bolognesi NA62 - GTK working group meeting

THE SYSTEM COOLING: – GAS FROM LIQUID – GAS ONLY THE SYSTEM – how it works and costs RUN AND MAINTENANCE PROCEDURES – pumpdown, cooldown, time constants : fast ramp up/down, emergency warm up, 1 heater broken INTERLOCK Na62 GTK working group meeting, CERN Marco Statera1

GAS FROM LIQUID Na62 GTK working group meeting, CERN Marco Statera2 Pro liquid is a reserve of gas fast restart time after an emergency stop cooling power: K safe shut off: the emergency valve reduces the dewar pressure Cons needs cryogenic liquid pumping vapor COST 4 systems: 370 k€ the gas above a liquid bath is forced into the cooling pipes and cooled down by a cold head the pressure of the dewar is kept constant the flow is regulated by the valve GT

GAS ONLY Na62 GTK working group meeting, CERN Marco Statera3 Pro gas temperature selection no liquid involved gas selection (He or N2) higher flow possible Cons refill by outer bottle time after emergency stop: must cool down pressure 3-4 bara COST 4 systems 400 k€ The cooling gas is cooled, compressed and circulated to cool down the GT GT

THE SYSTEM gas from liquid solution is proposed three stations: one coling station is not cheaper since the cost of the cryogenic lines. Three pumping/cooling systems are required each station is independent (no crosstalks) Installation side: Jura or Saleve 20 m of cryogenic lines: – the cooling station few meters far from the beampipe – the outer diameter is about 35 mm, we asked for a 100x100 mm 2 cross section in the trench the control system (PLC) is outside the cavern Na62 GTK working group meeting, CERN Marco Statera4

RUN AND MAINTENANCE RUN refill liquid nitrogen start the coldhead emergency stop -> some nitrogen gas lost; the liquid is a reserve. NO access required 6 months running SAFETY cryostat: pressurized vessel cold nitrogen standard issues to be discussed with lab safety staff MAINTENANCE every 9000 hrs (12 months run) coldhead maintenance (2 skilled persons for 2 days): head o-ring kit and compressor filters valves check (emergency test) Na62 GTK working group meeting, CERN Marco Statera5

PROCEDURES pumpdown cooldown turning on and regulation warmup emergency one chip failure Na62 GTK working group meeting, CERN Marco Statera6

PUMPDOWN Na62 GTK working group meeting, CERN Marco Statera7 turbopump nominal pumping speed: 70 l/s (N 2 ) Typical working pressure < 1 E-5 mbar Improve vacuum performance: faster pumpdown and lower ultimate pressure accurate handling/cleaning UHV materials vacuum before installing

BOARD UNDER VACUUM Na62 GTK working group meeting, CERN Marco Statera8 EXAMPLE: VACUUM CYCLE OF THE VACUUM BOARD FIRST CYCLE IS SHOWN HIGH VACUUM REACHED: 1E-5 MBAR AFTER 3 CYCLES HIGH WATER CONTRIBUTION

COOLDOWN - 1 Na62 GTK working group meeting, CERN Marco Statera COOLDOWN CONSTANT FLOW COOLDOWN SEVERAL FLOWS

COOLDOWN - 2 Na62 GTK working group meeting, CERN Marco Statera10 stable cooldown conditions set cooling speed and temperature by flow regulation i.e. regualting the valve COOLDOWN TEMPERATURES AND FLOW

TURN ON AND REGULATION Na62 GTK working group meeting, CERN Marco Statera W (16 –> 24 W) ΔT 25 °C in 35 s the full digital power on (48 W) requires control (heater) regulating the flow 10 seconds compatible with a few seconds full on/off valve

TURN OFF Na62 GTK working group meeting, CERN Marco Statera12 power is turned off and then flow is turned off 1 to 2 seconds to react no need of a very fast interlock: 1Hz is fine

TURN ON PROCEDURE a heater resistor is required (on the N 2 line) use of an additional temperature sensor (a TC not on the sensor) increase the flow regulating the board temperature by the heater -> nominal flow (sensor temperature > -20 Celsius) turn on the sensors and turn off the heater regulate the SENSOR temperature by the valve (flow) Na62 GTK working group meeting, CERN Marco Statera13

WARM UP Na62 GTK working group meeting, CERN Marco Statera14 self warm up – cooling turned off max warming speed about 40 K/h heating not required Nov 2010

EMERGENCY Na62 GTK working group meeting, CERN Marco Statera15 about 25 seconds with the valve closed: temperature rise 4 seconds power is stopped no need of very fast interlock: about 1 second May 2011

CHIP FAILURE Na62 GTK working group meeting, CERN Marco Statera16 broken heater failing PT100 the temperature drop in case the heater (chip) fails is about 10 power 32 W The system reads one temperature, may change the flow and/or set an allarm

INTERLOCK INPUT (4) – sensor temperature (average or 1 point) – TC on the board (requested) – chip power supply current – emergency signal OUTPUT (3) – sensor temperature (crosscheck) – regulating valve opening – status (OK/alarm) PLC (fully hardware – interlock & control) – outside the cavern – no interaction during run – RATE: about 1Hz (typical 10Hz) Na62 GTK working group meeting, CERN Marco Statera17

PROGRAMS COOLDOWN – stable flow (i.e. valve opening) – regulating temperature by TC on the board STANDBY – preparation before run and after run – TC on the board useful RUN – control loop: Si temperature valve opening WARM UP EMERGENCY – close the regulating valve (normally closed) – open the safety valve of the dewar (1 atm in seconds) – turn off the cryohead (and heating to room temperature if possible) – emergency signal output Na62 GTK working group meeting, CERN Marco Statera18

CONCLUSIONS the results we have shown – the system has been tested up to 56 W (actual power distribution) – the system can work with different power distributions: 32 W homogeneus power distribution results system overview – cooling method: gas from liquid nitrogen – installation requirements – no access required during a full run – measured parameters for different working states control and interlock – input/output defined – running programs defined – interlock conceptual design for different working states Na62 GTK working group meeting, CERN Marco Statera19