1. 1 VI Single-wall Beam Pipe tests M.OlceseJ.Thadome (with the help of beam pipe group and Michel Bosteels’ cooling group) TMB July 18th 2002

2. TMB: CERN June 2002 M.Olcese – J.Thadome2 Double Vs. Single Wall Design  Same heater  Same outer envelope  Same reflective layer (moved outside)

3. TMB: CERN June 2002 M.Olcese – J.Thadome3 Proposed thermal insulation  Nano-porous Silica Aerogel in flexible quartz fiber carrier Very low thermal conductivity: 10-12 mW/mK @ Tamb Very low density: 0.09-0.12 g/cm3 Radiation length: 250 cm (worst density) Resistant up to 600 °C Contains: mostly inert materials Si oxides, quartz fibers, not sensitive to irradiation Two available types from Aspen Aerogels: White grade (Pyrogel UQS) Black grade (Pyrogel CQS): carbon opacified to minimize the radiation at high temperature

4. TMB: CERN June 2002 M.Olcese – J.Thadome4 Thermal conductivity vs. T  The thermal conductivity of the Carbon opacified type does not change in the temperature range we are interested in  Carbon opacified type is apparently also more stable in terms of aerogel powder release  However it contains small quantities of carbon which in case of failure of the encapsulation might have a bad impact on the pixel detector

5. TMB: CERN June 2002 M.Olcese – J.Thadome5 Local effects and beam pipe offset  Conduction and radiation are uniform in , while the convective heat flux varies significantly with  his is due to the non  symmetric flow pattern in the gap  I have found an article on an experimental study in equivalent conditions (in terms of characteristic dimensionless Ra number). The proposed correlations lead in our case to a max local heat flux 2.6 times higher than the average (on the top).  Other experimental studies show that the influence of the beam pipe offset up to 5 mm produce a change of both the average and local heat flux of less than 10% The worst case heat flux, which the top B-layer stave will have to dissipate during the bake out is 10 W (9% of nominal cooling capacity) conclusion

6. TMB: CERN June 2002 M.Olcese – J.Thadome6 Thermal tests on real scale mockup  1 m long tube with deposited heater  Two layer of Aerogel UQS (total Aerogel thickness of 5-6 mm) with aluminized kapton encapsulation (total thickness of insulation package 9 mm)  External cylindrical heat exchanger to simulate the B-layer structure (black internal surface to maximize radiation) Tube cooled and maintained at a uniform temperature Insulating plug Beam pipe with heater and insulation  Tube was heated up to 250 ° C and as function of the outer tube temperature we measured: the required heating power (heat dissipated by the B-layer + losses) The temperature distribution on the outer surface of the insulation 1000 mm

7. TMB: CERN June 2002 M.Olcese – J.Thadome7 Experimental setup Heat exchanger Monophase C6F14 cooling unit Beam pipe mockup Detail of aluminized kapton encapsulation fridge readout

8. TMB: CERN June 2002 M.Olcese – J.Thadome8 Test results  Equivalent thermal conductivity of insulation package is 75% above the Aerogel expected value (from vendor data sheet): air gaps, radiation?  Measured heating power is about 35% more than what was expected but this includes the heat losses difficult to estimate correctly  The heating power increases only by 10 % for a B-layer temperature change of 10 ° C

9. TMB: CERN June 2002 M.Olcese – J.Thadome9 Temperature distribution vs. offset  Positive vertical offset does not show significant changes in temperature distribution  In case of negative vertical offset the mid and bottom temperatures are lower  This is confirmed by the measurements of the total heating power which in case of negative vertical offset is about 4% higher and it is also in agreement with literature Beam pipe Temperature sensor insulation top mid bottom 5 mm vertical positive offset

10. TMB: CERN June 2002 M.Olcese – J.Thadome10 Extrapolation to proposed design  Extrapolation from measurements leads to a max power of about 200 W/m  Worst stave position (top) would require a coolant T of – 8 ° C to keep the whole module below 0 ° C ° -8 ° C ° - 4 ° C ° 0 ° C 1.5 W/module (top stave) (15% nominal cooling capacity) Flex hybrid sensor FE stave Cooling tube

11. TMB: CERN June 2002 M.Olcese – J.Thadome11 New irradiation studies  A sample of Aerogel UQS has been bent at the beam pipe radius and irradiated up to a dose of 5x10 15 pt/cm 2  It has a negligible contact activation dose  The irradiated area of the sample does not show any visible mechanical degradation (cannot be distinguished from the non irradiated one)

12. TMB: CERN June 2002 M.Olcese – J.Thadome12 Remarks  The installation of the Aerogel around the beam pipe is not easy  The aerogel material is wavy and shows significant non-uniformities  The Aerogel cannot be glued : has to be hold in place by the kapton encapsulation  Need to find a better technical solution and to make more practice

13. TMB: CERN June 2002 M.Olcese – J.Thadome13 Next steps  check thermal conductivity of last irradiated sample at higher dose (Sept.)  Make vibration tests on thermal mockup (with a conservative spectrum) and repeat the thermal tests to check possible loss of thermal performances due to aerogel powder migration (Oct.)  Make same vibration tests on the irradiated sample and measure again the thermal conductivity (Oct.)  Assess installation methods including encapsulation  Study design changes to be incorporated in the current baseline: redesign the support collars, assess the design impact on the wire supports  Make a full VI section prototype?? I can manage I can help