1. DT2 Scientific Tea 23.3.2007 CLOUD Technical Challenges Antti Onnela PH / DT2

2. A. Onnela, CERN PH/DT2 CLOUD Technical Challenges  The CLOUD Recipe: Step 1: Select and mix ingredients to create an “atmosphere” where clouds form in nature Step 2: Shoot that with a suitable beam Step 3: Measure what happens  Step 2 is easy at CERN !  But what is needed for steps 1 and 3 ?  First attempt: Year 2006 beam tests with CLOUD Mk I

3. A. Onnela, CERN PH/DT2 Final CLOUD, the chambers Beam Reaction chamber Diam. ~2m, height ~2m Cloud expansion chamber Diam. ~0.5m, height ~0.5m

4. A. Onnela, CERN PH/DT2 CLOUD Technical Requirements Gases & aerosols  Ultra-pure (artificial) air (80% N2, 20% O2)  Water vapour: Range: 0 < RH < 700% Range: 0 < RH < 700% RH >100% “supersaturations”RH >100% “supersaturations” Typical cloud values at supersaturation are 100.1% < RH < 101%Typical cloud values at supersaturation are 100.1% < RH < 101% Accuracy: 0.1% absolute, in the range 0% < RH < 100% Accuracy: 0.1% absolute, in the range 0% < RH < 100% Stability: 0.1% absolute, in the range 0% < RH < 100% Stability: 0.1% absolute, in the range 0% < RH < 100%  Aerosols, examples: H2SO4-H2O, (NH4)2SO4-H2O.  Trace gases, examples: SO2, O3, H2SO4, NH3, HNO3, terpenes. Cleanliness:  <0.01 condensation nucleus (molecular cluster of any size) per cm3 at start of each run.  Avoid “dangerous” impurities at sub-ppt level 100 drops of ink in Lac Leman! 100 drops of ink in Lac Leman! Dangerous impurities?: Any condensable vapour, like NH3 or organics Dangerous impurities?: Any condensable vapour, like NH3 or organics

5. A. Onnela, CERN PH/DT2 CLOUD Technical Requirements Temperature  Range: -90 ºC - +40 ºC Temperatures in troposphere and stratosphere. Temperatures in troposphere and stratosphere.  Accuracy: 0.1 ºC absolute  Stability: 0.01 ºC Slow variations (over few minutes) Slow variations (over few minutes)Pressure  Range 0-1.5 bar absolute Lowest pressure for vacuum bakeout. Lowest pressure for vacuum bakeout. Highest pressure for large expansion down to 1 atm Highest pressure for large expansion down to 1 atm  Accuracy: deltaP/P = 1 ‰ absolute  Stability: deltaP/P = 0.1 ‰ (0.1 mbar at 1 bar)  Cloud expansion chamber: Piston displacement range 10 μm up to 180 mm (= 0.002% to 36% volume increase) Piston displacement range 10 μm up to 180 mm (= 0.002% to 36% volume increase)

6. A. Onnela, CERN PH/DT2 CLOUD prototype 2006, main goals  First exercise of building a CLOUD setup in a beam Get experience, learn for the CLOUD requirements Get experience, learn for the CLOUD requirements Try how T11 area fits CLOUD needs Try how T11 area fits CLOUD needs  Get the CLOUD collaboration to work together High-energy physics style of collaborative work is not that common in all sciences…High-energy physics style of collaborative work is not that common in all sciences…  … and even obtain some physics results!

7. A. Onnela, CERN PH/DT2 CLOUD beam tests 2006: East Hall T11 beam area T11 counting room

8. A. Onnela, CERN PH/DT2 T11 beam area CLOUD beam tests 2006: East Hall

9. A. Onnela, CERN PH/DT2 CLOUD beam tests 2006: T11

10. A. Onnela, CERN PH/DT2 CLOUD beam tests 2006 CLOUD Test Chamber UV-lights Beam dump Measurement instrumentation Beam hodoscope Last magnet De-focused beam

11. A. Onnela, CERN PH/DT2 CLOUD beam tests 2006 T11 temperature measurements in April 2006:  Temperature outdoors varied between ~ +5 ºC and ~ +25 ºC + 12 ºC + 23 ºC 10 h 1 week Diesel fume ventilation at end of day…

12. A. Onnela, CERN PH/DT2 CLOUD proto Mk I Photos: DNSC, Copenhagen

13. A. Onnela, CERN PH/DT2 CLOUD proto Mk I Photos: DNSC, Copenhagen 0 V10 kV UV window

14. A. Onnela, CERN PH/DT2 CLOUD proto Mk I Photos: DNSC, Copenhagen

15. A. Onnela, CERN PH/DT2 Experimental areas: never too much space! Counting room looks fine! Experimental area was pertty nice in the beginning… …but quite full later. Photos: DNSC, Copenhagen

16. A. Onnela, CERN PH/DT2 CLOUD beam test 2006: Ultra-pure air system Flow requirements: 20 volume changes à 8 m3 at start Max flow rate ~100 l/min 50 l/min for sampling instruments TOTAL of ~ 5000 m3 of air for 10 weeks of running Photo: MPI, Heidelberg

17. A. Onnela, CERN PH/DT2 CLOUD beam test 2006 Photo: CERN Bulletin 43 / 2006

18. A. Onnela, CERN PH/DT2 CLOUD prototype 2006, lessons learned  Temperature stability extremely important and must be improved Rather clear ideas how to improve Rather clear ideas how to improve  Cleanliness extremely important and must be improved Measurement chamber AND feeding and sampling systems Measurement chamber AND feeding and sampling systems Some ideas how to improve, but not that clear yet Some ideas how to improve, but not that clear yet Chamber construction can be improved to facilitate cleaningChamber construction can be improved to facilitate cleaning Need better quality space, equipment and methodsNeed better quality space, equipment and methods Would be good to be able to clean also in-situ…Would be good to be able to clean also in-situ…  Gas supply system (dewars and mixing system) worked well Good basis for future development Good basis for future development Present equipment can be used in next beam test (autumn 2007) Present equipment can be used in next beam test (autumn 2007)

19. A. Onnela, CERN PH/DT2  Beam tests Sep-Oct 2007. New Mk II chamber being designed by the Danish team Sep-Oct 2007. New Mk II chamber being designed by the Danish team Beam area modifications being looked at with AB department Beam area modifications being looked at with AB department  Funding! EU FP7… EU FP7…  Design study for final CLOUD 2008-2010 2008-2010  CERN’s role in CLOUD? Approved CERN experiment (PS-215/CLOUD) Approved CERN experiment (PS-215/CLOUD) Host lab activities (beam area, safety aspects, etc.) Host lab activities (beam area, safety aspects, etc.) Other involvements at very low level now. This could change after LHC is ready… Other involvements at very low level now. This could change after LHC is ready… CLOUD, some words on the future

20. A. Onnela, CERN PH/DT2 CLOUD Technical Challenges SPARE SLIDES

21. A. Onnela, CERN PH/DT2 T11: Proposed new layout New dump Gas racks for CLOUD Move door slightly Modify wall Modify cable trays Modify platform Fence on top of wall

22. A. Onnela, CERN PH/DT2 CLOUD Technical Requirements Electric field  0 - 10 kV/m generated by open-geometry field cage mounted inside chamber volume.  Modest uniformity requirements.  Purpose Simulate fair-weather cloud electrification Simulate fair-weather cloud electrification Sweep ions/charged droplets when required Sweep ions/charged droplets when required Magnetic field:  No magnetic field requirements  No shielding requirements.

23. A. Onnela, CERN PH/DT2 CLOUD Technical Requirements Safety  Radiation Standard key-interlocked access restrictions to experimental area. Standard key-interlocked access restrictions to experimental area.  Activation Low beam intensities, no equipment activation Low beam intensities, no equipment activation  Pressures Necessary safety valves. Necessary safety valves.  Gases Most gases non-hazardous: naturally-occurring trace gases; concentrations at sub-ppm levels. Most gases non-hazardous: naturally-occurring trace gases; concentrations at sub-ppm levels. But also more “interesting ones”: liquid O2, NO2 But also more “interesting ones”: liquid O2, NO2  Electrical safety Groundings, HV protections Groundings, HV protections  Other Protection from UV exposure Protection from UV exposure