Highlights from the mechanical review committee report

1
Highlights from the mechanical review committee
report

• Overall mechanical design
• Stress Analyses
• The magnetic field
• RF shield
• The vacuum system
• The pixel plane
• Substrate
• Sensor
• electronics

2
Overall mechanical design

• Design review positive. Some issues that we
  should address
• Table of design loads
• Cables (during cable dressing procedure and
  steady state)
• Thermal gradients
• Transmitted from the beam pipe to the detector?
• Installation procedure of half planes
• The vacuum box is the stainless steel used
  non-magnetic?
• Sealing of the PCB used for cable feed-through
• Use of a single PCB versus a few PCBs glued
  together
• Sealing properties of G10 (lateral leaks)

3
An example of leak-proof large pCB made up of 4
panels

• Large PCBs can be made-up of several boards
  joined together.
• The CLEO RICH cathode plane is about 2.5 m long
  and was made flat to specs.

4
Operation in a magnetic field

• Use of magnetic material inside the magnet should
  be avoided to protect the integrity of the
  components for safety issues
• Steady state magnetic forces
• Quench effects
• We should identify immediately the magnetic
  components and find alternative solutions.

5
RF shield

• The very thin RF/vacuum membrane will not take
  much pressure. Coordination of the initial
  pump-down to guarantee matched pressure. The same
  issue exists during let-up. Is any sort of over
  pressure protection possible?
• How this system will be leak tested? How could a
  small leak in the RF/vacuum shield be localized?
  
• Importance of early prototype work

6
The vacuum system

• Clarify specs definition (steady state-resilience
  against possible failure modes of different
  components)
• Interface with the beam specifications.
• Realistic estimate of the gas loads and possible
  gas accumulation at cold spots.
• Coordination of vacuum pumping in accelerator and
  vacuum box.
• Pressure protection to avoid permanent
  deformation of the RF shield
• Some concerns about the cryo-pumping option (see
  report)

7
The vacuum system and the cryogenic option

• Suggestion that maintaining the hybrid detector
  at cryogenic temperature (130K?) needs to be
  studied carefully in all its implications for the
  rest of the system
• Readout electronics
• Cables
• Stresses induced by temperature gradients
• Bump bonds

8
The pixel plane

• Items reviewed included mechanical design and
  external constraints.
• In view of the CTE issues, it is important to
  establish
• The operating temperature required by this
  system
• sensor assumed to require operating temperature ?
  -5 to -10 ?C
• Suggestion that the vacuum system may require
  going to cryogenic temperatures must be evaluated
  VERY carefully in all its implications
• The heat load must be established, including
  whether it is a static or a cycling load, i.e.
  periodicity in electronics power-down up.

9
The substrate choice

• The fuzzy carbon option has some very good
  aspects generally recognized (low mass, better
  CTE match to Si).
• Concerns that need to be addressed are
• Single source reliability, ability to complete
  project/maintain the projected cost/schedule
  agreed upon in the course of the project.
• The cooling manifold including many joints that
  need to be reliability sealed.

10
Substrate a realistic back-up?

• Be discussed at length. The CTE mismatch makes it
  a very unappealing back-up to most of the
  committee members.
• Potential failure of the wire-bonds/bump-bonds
• Stresses that make it impossible to identify
  where the pixels really are.
• We heard little about the pocofoam substrates but
  they look really promising?develop a realistic
  back-up solution based on them.

11
Attachment of the hybrid detector to the substrate

• Glue layer between ROC and substrate
• Material thickness (radiation length issues),
• temperature gradient across it,
• radiation resistance.
• Temperature profile across the thickness of the
  module

12
The cooling manifold

• Complex system with several joints. High priority
  item in prototyping effort.
• The joint between tubes and manifold
• how to make it solid?
• How to leak test them (during production after
  the final assembly)?
• Vibrations generated by flowing fluid (resonant
  frequencies)
• Leak-proofing the system effects of having a
  leak in the secondary vacuum

13
The cooling system

• Default option generally liked a lot
• Perhaps effort should be steered towards aspects
  related to the system design

14
Important items that we should review internally
very soon

• Alignment issues
• Method that we will use to determine initial
  alignment of the various pixel planes
• Factors that may make the planes move
• Hardware monitoring
• Assembly issues
• How is the system going to be assembled, tested
  for integrity at the various steps, which kind of
  stresses we anticipate in this process
• Testing procedure during assembly leak tests,
  electrical integrity tests, alignment