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BGI Regular Meeting

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864/2-B14 - SALLE J.B.ADAMS (CERN)

864/2-B14 - SALLE J.B.ADAMS

CERN

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BGI Regular Meeting
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63808180348
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James Storey
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Present: James, Lauren, Mark, Justus, Lukas, Hampus

HL-LHC BGI

Budget and EVM structure

The updated budget structure has been divided into work units covering beamline (vacuum components), mechanics (instrument and chamber), electronics, magnet, power converters, and infrastructure. Electronics and magnet estimates are relatively mature, while mechanics and beamline costs still require refinement. Current totals remain broadly consistent with the overall project envelope.

Expenditures are currently being booked against legacy prototype budget codes, which no longer contain allocated funds. A new budget structure and codes will be created once the updated cost profile is finalized. The project contingency will be handled centrally, so contingency should not be included in individual subsystem budgets.

It was agreed that the baseline planning assumption remains four instruments plus one spare, with additional spare components (e.g. ceramics) procured as needed to mitigate yield risks. The possibility of producing a reduced-cost spare vacuum chamber for laboratory use was also discussed.

Magnet design and HV cable routing

Dominique has requested confirmation of available space in order to freeze the magnet design. In particular, the minimum bending radius and routing of the high-voltage cable must be verified. Possible solutions include routing the cable directly to the instrument or producing a custom made right-angle connectors to reduce bend-radius constraints.

Mechanical tolerances and simulations

Recent simulations of profile distortion due to detector tilt and rotation suggest that expected mechanical tolerances should be acceptable. Work is ongoing to translate angular misalignments into practical mechanical tolerance requirements.

Timepix mounting and cooling approach

A potential assembly sequence was discussed involving:

  • brazing a ceramic substrate to a copper-tungsten cooling block,

  • soldering or gluing the Timepix ASIC to the ceramic,

  • placing a PCB with a central cut-out over the ASIC, and

  • wire-bonding connections between ASIC and PCB.

Copper-tungsten appears promising due to matched thermal expansion and good thermal conductivity. Preliminary simulations indicate that adequate cooling can be achieved using this approach.

Outgassing tests on candidate materials are ongoing. Initial ceramic glue tests showed cracking due to curing and thickness issues; improved preparation and degassing procedures will be tested. Brazing and metallization options, including gold deposition on ASIC backsides, are being investigated with CERN and external specialists.

PCB and integration concept

The proposed PCB design includes a central opening allowing independent mechanical mounting and cooling of the ASIC stack. This approach avoids coupling PCB fabrication constraints with chip mounting requirements and simplifies thermal management. The feasibility of machining the PCB cut-out and accommodating power distribution and decoupling components needs to be confirmed.

Project milestones

A BGI production readiness review is scheduled for 22 April 2026. By that date, it will be important to converge on a baseline mounting and PCB design approach and obtain preliminary outgassing test results.

PS & SPS BGI

Software and system integration

Progress is ongoing toward commissioning one PS and one SPS system using the full software stack. Basic communication, monitoring, and parameter configuration are now functional.

Work is focused on implementing a background-process state machine to manage system tasks such as synchronization checks, noisy pixel detection, masking, and diagnostics. This will allow the system to maintain readiness autonomously between measurement cycles.

Equalization remains an important step but is currently lower priority compared to achieving stable measurement acquisition. Existing equalization files may be reused initially, with full equalization incorporated later into automated procedures.

The timeline is currently approximately two weeks behind schedule, with first operational tests expected shortly.

Timing system upgrades

PS and SPS timing will transition to White Rabbit-based timing distribution in future upgrades. This transition is expected to be handled centrally, with minimal required changes to the BGI systems.

Telescope

Sensor procurement and assembly strategy

Quotes for thinned Timepix assemblies have been received, but the high cost and lack of guarantees require careful evaluation. Questions have been sent to vendors regarding process reliability and testing procedures.

An alternative approach involving in-house testing of bare or partially processed ASICs is being considered, although handling and thinning risks remain significant.

Cooling and PCB development

Cooling system prototypes using water-glycol circulation are under development. Preliminary simulations indicate that stable ASIC operating temperatures can be achieved. PCB modifications are underway to accommodate cooling block geometry and optimized decoupling capacitor placement.

The readout architecture will initially rely on simplified prototyping methods (e.g. Python-based control via development hardware), allowing early validation of mechanical and electrical integration without waiting for full readout system deployment.

Prototype and beam test planning

CLEAR beamtime has been requested for late 2026. The goal is to develop a prototype detector with integrated cooling, PCB, and readout compatibility in time for initial testing.

A staged approach will be followed, beginning with mechanical and electrical prototypes and progressing toward fully integrated detector systems.

Actions

  • William: Review and refine HL-LHC BGI mechanics budget estimates.

  • James: Finalize HL-LHC BGI budget profile and create new budget codes once subsystem estimates are updated.

  • Lauren / Gunn: Confirm minimum bend radius and routing feasibility of HV cables to allow magnet design freeze.

  • Lauren: Continue glue preparation and outgassing tests; prepare additional samples with improved curing procedures.

  • Lauren / William: Coordinate brazing feasibility tests and investigate gold metallization options for Timepix mounting.

  • Mark / Lauren: Develop PCB design including central cut-out and integration with cooling concept.

  • Justus: Continue evaluation of telescope sensor procurement options and refine cooling prototype and PCB layout.

  • James: Prepare timeline for Timepix4 electronics development.

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