VI Single-wall Beam Pipe tests

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

2. Double Vs. Single Wall Design • Same heater • Same outer envelope • Same reflective layer (moved outside) M.Olcese – J.Thadome

3. 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 M.Olcese – J.Thadome

4. 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 M.Olcese – J.Thadome

5. Local effects and beam pipe offset • Conduction and radiation are uniform in f, while the convective heat flux varies significantly with f. This is due to the non f 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% conclusion 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) M.Olcese – J.Thadome

6. 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 Beam pipe with heater and insulation 1000 mm Insulating plug • 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 M.Olcese – J.Thadome

7. Experimental setup Monophase C6F14 cooling unit Heat exchanger fridge readout Beam pipe mockup Detail of aluminized kapton encapsulation M.Olcese – J.Thadome

8. 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 M.Olcese – J.Thadome

9. Temperature distribution vs. offset 5 mm vertical positive 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 insulation top mid bottom Beam pipe Temperature sensor M.Olcese – J.Thadome

10. 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 Cooling tube stave FE sensor - 4 °C Flex hybrid 0 °C 1.5 W/module (top stave) (15% nominal cooling capacity) M.Olcese – J.Thadome

11. New irradiation studies • A sample of Aerogel UQS has been bent at the beam pipe radius and irradiated up to a dose of 5x1015 pt/cm2 • 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) M.Olcese – J.Thadome

12. 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 M.Olcese – J.Thadome

13. 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 M.Olcese – J.Thadome