Module design and development for LHCb VELO Upgrade Project Oscar Augusto de Aguiar Francisco on behalf of the VELO Upgrade group CERN Forum on Tracking Detector Mechanics 2018 Valencia - Spain
Outline Introduction Module Assembly Module Insertion JIG Vacuum feedthrough board Cooling safety system RF foil and motion system Temperature probes Summary 2
LHCb experiment and VELO LHCb experiment: One of the 4 major experiments at LHC Forward spectrometer designed to measure CP violation, study rare decays of c and b hadrons and search for new physics. Performance of the LHCb Vertex Locator - arxiv:1405.7808 Current VELO Subdetector located around the p-p collisions Responsible for vertex and track reconstruction 88 Si-strip sensors surrounding the interaction point Modules are moved away during the beam injection Excellent impact parameter resolution (down to 11.6 µm) Best single hit resolution ~4 µm Total power dissipated is ~16.5W/module 3
Key features for the upgrade In Run III, the luminosity will be increased by a factor 5 Very high (8x10 15 MeV n eq /cm 2 for 50 fb -1 ) & non-uniform radiation (~r 2 ) Huge data bandwidth: up to ~15 Gbit/s for central ASICs and 2.9 Tbit/s in total Operation under vacuum (Secondary vacuum) Cooling Sensor tip temperature < -20 o C Increased power dissipation (30 W) New cooling technique (See Wiktor Byczynski Talk for more details (Yesterday)) 4
New module design module foot (aluminium) Microchannel cooling substrate GBTx (Transceiver) Legs (Carbon Fiber ) midplate Beam Fluidic connector hybrid (copper+kapton) sensor bump-bonded to 3 ASICs (tile) VCR connector position CO2 capillary routing Cables and supports not shown! 5
Attachment of the feet and module base 2011 Araldite glue Tolerances of 50 μm along the beam axis and 20 μm in the transversal plane in respect to the JIG 6
Feet and base attachment Flatness of the JIG is within 10 μm The position of the legs are defined by the JIG The legs are glued with araldite to the foot The position of the substrate is defined by 3 pillars in the JIG The capillaries lie in the support The midplate is glued to the legs This is done with a precision of ±16 μm 7
Tiles, hybrids and GBTx attachment Stycast FT2850 catalyst 9 for the tiles Araldite 2011 or Loctite 5145 for the hybrids and GBTx Placement precision Tiles 10 mm Hybrids and GBTx 100 mm 8
Tiles, hybrids and GBTx attachment Front tiles are moved into position relative to the TURNPLATE fiducials. Alignment precision < 2 μm. TRANSFER PLATE placed on top and vacuum switched to pick-up. Transfer precision < 4 μm. The TRANSFER PLATE can pick-up the hybrids and the GBTx simultaneously Repeat with back side 9
Tiles, hybrids and GBTx attachment Both transfer plates are supported on robot platform (Fisnar F5200N) and a pattern of glue lines is applied The coverage of this pattern after gluing is ~80% 10
Tiles and hybrids attachment Transfer plates Module is mounted in the turn-plate and fixed by its foot, accurately located on a dowel and groove, with substrate support from side wings. Sensor tiles and hybrids are aligned onto front and back vacuum transfer plates. Transfer plates slide onto precision ground pins on the turn-plate and held in place by spring clamps. Micrometer screw legs control the spacing of the various components. 11
Components attachment Stycast FT2850 with catalyst 9 (High thermal conductivity - 1.25 W/m.K / hard glue Shore D 96) is used to glue the tiles to the substrate (No thermal expansion mismatch) Loctite 5145 100 μm thickness Shear force test For the Hybrids and GBTx, two glues are under investigation: Araldite 2011/2020: Epoxy glue (hard Shore D 80) It could lead to module stresses/deflections due to temperature changes Proven to be radiation hard Loctite 5145(Silicon glue - soft): Silicon glue/sealant (soft Shore A 45) It can absorb CTE mismatch Araldite and Stycast studies can be found in this public note (LHCb-PUB-2016-026, CERN-2001-006) 12
Tiles and hybrids attachment (Short videos) 13
Tiles and hybrids attachment (Short videos) 14
Wire bonding The electrical connections between the hybrid and the tiles are done with wire bonding (short 1.5 mm / long 2.3 mm) Tests with mechanical tiles show a very promising result using the G5 bond machine Tests on going to validate the quality of the connection (8 g pull test) 15
Cabling layout and pipe support Tiles GBTx Hybrids Data cables Low voltage cables CO 2 output CO 2 input Custom connector (wires not soldered) 16
Cabling layout and pipe support Bridge support: Reduces the total number of wires going away from the module (wire splitting) Also allows material reduction in the module area (thinner wires) Tubes support: Prevents stress in the capillaries during the assembly Cable support: Avoids that the weight of the cables deflect/stress the module 17
Insertion JIG Modules will be installed like cartridges The insertion JIG also allows to keep the modules in dry air or vacuum Any module can be removed even when it is already fully populated Insertion JIG for the current VELO 18
Vacuum feedthrough board Vacuum Isolation Vacuum (Cooling safety system) Secondary Vacuum O bent capillaries to absorb the motion of the detector Module Positronic connector Vacuum feedthrough board Air 19
Vacuum feedthrough board Interesting technique to use a PCB board as vacuum feedthrough Two aluminum half moons with dowel pins to keep all the parts in place Firstly, it is glued using araldite 2011 (more viscous) Araldite 2020 is used on both sides to make it leak tight 24 hours curing time for each gluing step (~ 72 hours in total) Helium test rate is order of 4.2 10 10 mbar L/sec at Vacuum chamber pressure 1.3 10 5 mbar At Helium test the FT (epoxy) behaves better than the O-ring 20
Cooling safety system Vacuum Isolation Vacuum (Cooling safety system) Secondary Vacuum O bent capillaries to absorb the motion of the detector Module Positronic connector Vacuum feedthrough board Air 21
Isolation Vacuum (Safety system) Keeps the safety valves in vacuum to prevent ice formation Every two module loops are in between two valves 52 modules and in total 52 valves (26 per side) An expansion volume is necessary to close the valves and prevent pressure build up while the system warms up Two bypasses: 1) Always open to ensure minimum flow to keep the distribution lines cold 2) Diverge the flow if the safety system is activated in such way that the variation of pressure over the detector is the same CO 2 CO 2 Closed valve Open valve Module Module Module Module CO 2 CO 2 Expansion Volume (Gas) Calibrated restriction 22
Isolation Vacuum (Safety system) Keeps the safety valves in vacuum to prevent ice formation Every two module loops are in between two valves 52 modules and in total 52 valves (26 per side) An expansion volume is necessary to close the valves and prevent pressure build up while the system warms up Two bypasses: 1) Always open to ensure minimum flow to keep the distribution lines cold 2) Diverge the flow if the safety system is activated in such way that the variation of pressure over the detector is the same CO 2 CO 2 Module Module Module Module Normally closed valve Normally open valve CO 2 CO 2 Expansion Volume (Gas) Calibrated restriction 23
Isolation Vacuum (Safety system) 3D design Bypass valve (Normally open) and permanent bypass 26 safety valves (normally closed) Filter (40 μm) Output and input tubes The valves are activated using a nitrogen supply (bottles redundancy) 24
Modules, mechanical supports and Isolation vacuum Isolation vacuum 26 modules per side Beam line 25
RF foil The beam vacuum (primary) is separated from the detector vacuum (secondary) by a thin aluminum foil. Milling Etching Mask Shield the detector against the beam high frequency Withstand a maximum variation of pressure of 10 mbar Minimum material (material interaction) It guides the mirror current of the beam Milling starting with a single aluminum block (Minimum of 250μm thickness around the beam line) Potential to etch even further close to the beam down to 150μm to minimize material interaction 26
Temperature probes on cooling loop and RF 1,5: Input / Output 2-4: Cooling status and state of the safety valves (Open/Close) 6: Safe to close the valves RF foil temp. Probes: 8 In isolation vacuum, per side: 2+1+26+13=42 In secondary vacuum, per side: 8+4*26= 112 Total of 154 temperature probes per side to control the cooling loops 1 2 3 4 6 5 27
Modules, mechanical supports and Isolation vacuum Modules are moved away 3 cm if the beam is not stable Motion system for the current VELO 28
Top view of the cables S-shaped cables to absorb the motion Vacuum feedthrough board Modules Beam 29
Full 3D design Isolation vacuum Beam vacuum Vacuum feedthrough board Modules Beam 30
2018 Timeline 28/09/17 Cooling Engineering design report 10/04/18 RF foil Production Readiness Report 30/04/18 Electronics Production Readiness Report 16/07/18 Module Production Readiness Report 01/10/18 Module + Base Production Readiness Report 31
Summary Well defined module assembly procedure Attachment of different components (Tiles, Hybrid and GBTx) Cable layout and pipes support Module insertion JIG Cooling safety system RF foil Temperature probes for safety and monitoring system Some topics were not covered (like module base, hood and deinstallation of current detector) Next important review: Assembly of the first electrical module for the Module Production Readiness Review (PRR) on July 16 th 32