1. GTK GAS COOLING SYSTEM Marco Statera, Vittore Carassiti, Ferruccio Petrucci, Luca Landi, Stefano Chiozzi, Manuel Bolognesi NA62 - GTK working group meeting 2-12-2011

2. 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 2-12-2011 Marco Statera1

3. GAS FROM LIQUID Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera2 Pro liquid is a reserve of gas fast restart time after an emergency stop cooling power: 170 W @ 77K 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

4. GAS ONLY Na62 GTK working group meeting, CERN 2-12-2011 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

5. 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 2-12-2011 Marco Statera4

6. 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 2-12-2011 Marco Statera5

7. PROCEDURES pumpdown cooldown turning on and regulation warmup emergency one chip failure Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera6

8. PUMPDOWN Na62 GTK working group meeting, CERN 2-12-2011 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

9. BOARD UNDER VACUUM Na62 GTK working group meeting, CERN 2-12-2011 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

10. COOLDOWN - 1 Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera9 7-11-2011 COOLDOWN CONSTANT FLOW 22-11-2011 COOLDOWN SEVERAL FLOWS

11. COOLDOWN - 2 Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera10 stable cooldown conditions set cooling speed and temperature by flow regulation i.e. regualting the valve 29-11-2011 COOLDOWN TEMPERATURES AND FLOW

12. TURN ON AND REGULATION Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera11 + 8 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

13. TURN OFF Na62 GTK working group meeting, CERN 2-12-2011 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

14. 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 2-12-2011 Marco Statera13

15. WARM UP Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera14 self warm up – cooling turned off max warming speed about 40 K/h heating not required Nov 2010

16. EMERGENCY Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera15 about 25 seconds with the valve closed: temperature rise 4 K/s @25 seconds power is stopped no need of very fast interlock: about 1 second May 2011

17. CHIP FAILURE Na62 GTK working group meeting, CERN 2-12-2011 Marco Statera16 broken heater failing PT100 the temperature drop in case the heater (chip) fails is about 10 Degrees @ power 32 W The system reads one temperature, may change the flow and/or set an allarm

18. 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 2-12-2011 Marco Statera17

19. 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 2-12-2011 Marco Statera18

20. 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 2-12-2011 Marco Statera19