BU DESI Group Meeting

Tuesday 15 Jul 2025, 13:00 → 14:00 America/New_York

Zeynep Demiragli (Boston University (US))

BU Group DESI Group Meeting

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Meeting ID: 936 9135 3615
Passcode: 096623

1. Cryostat and CCD Modifications

• Discussion began with the implications of upgrading the CCD within the cryostat.

• Key considerations include:

  • Increased thermal mass (slower cooldown time).

  • Potential increase in thermal load due to more wires and possible IR photon leakage.

  • Potential need for an upgraded or re-evaluated cryo-cooler.

• It was agreed that:

  • A heat load calculation is needed.

  • Existing cryostat assumptions will be maintained unless cost-effective upgrades are feasible.

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2. Cryostat Mechanical Design

• The cryostat consists of three main parts: two end caps and a barrel.

• Originally machined externally in California (GNP group).

• Questions arose around:

  • The use of two or more vacuum flanges.

  • One port was for an ion pump; others had unclear purposes or possible leaks due to makeshift sealing methods.

  • Improperly sealed ports were noted to lack proper O-ring grooves.

  • Welding may be required to ensure vacuum integrity.

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3. Feedthrough Issues and Solutions

• Existing feedthrough design includes Peak (non-flexible) and stainless steel; requires welding for vacuum sealing.

• The group discussed:

  • Creating better seals.

  • Possibly designing a custom feedthrough.

  • Alternatives like potting standard connectors with epoxy to make them vacuum-tight.

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4. Cryo-cooler Considerations

• Current system lacks a cryo-cooler; Berkeley uses a ~$35k unit based on a pulse-tube design.

• It was noted that significantly cheaper options exist unless high-end specs (e.g., space-rated) are needed.

• Decision deferred on whether to replace or operate existing cryo-cooler with elevated temperature settings.

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5. Feedthrough Redesign for New Electronics

• Berkeley team identified a commercial feedthrough that is larger than current dimensions allow.

• Workaround proposed: adding a “snout” extension to accommodate larger diameter without interfering with the bolted end plate.

• Geometry constraints due to internal standoffs and external connector placement need to be studied further.

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6. Path Forward

• Immediate Actions:

  • Procure and test the identified commercial feedthrough model.

  • Use CAD software (preferably SOLIDWORKS) to model fitment and resolve geometric constraints.

• Medium-Term:

  • Focus on resolving the feedthrough issues and vacuum sealing before addressing the cryo-cooler.

  • Assume existing cryostat structure remains unless critical.

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7. CAD & Computing Resources

• Discussion on accessing or installing SOLIDWORKS to enable detailed mechanical studies.

  • Student license (~$60/year) was suggested.

  • Windows-based system required.

  • BU has computing infrastructure that may be adapted for this purpose.

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8. Concluding Remarks

• Emphasis on solving feedthrough issues first, possibly fabricating a new compatible end plate.

• Interest expressed in visiting the cryostat setup.

• A postdoc candidate recommendation will be circulated by email following the meeting.

13:00 → 13:30 Round Table

Speaker: Zeynep Demiragli (Boston University (US))