1. FSP vacuum considerations
Munich,
Contents:
Vacuum requirement & gas load
Example calculation
Possible remedies?
Next steps
Johannes Treis MPI Halbleiterlabor

2. Johannes Treis / Halbleiterlabor der MPG
Camera head structure
Target: Compact vacuum-tight camera housing ~ 18 x 25 x 10 ( +x) cm
Johannes Treis / Halbleiterlabor der MPG

3. Vacuum requirements & gas load
Outgassing contributions:
Camera housing interior
Flange interior
Backbone & mechanical structure surfaces
Cables & interfaces
Hybrid & PCB surfaces
Glues
Thermal interfiller materials
Detector surfaces
Requirement (as communicated):
Pressure inside camera housing: < 1 mbar
Pressure gradient: < 0.1 mbar / d
Understanding vacuum requirement:
Thermal stability?
Stability of detector properties?
Contamination issues?
Vibrations?
Accessibility?
Leakage:
Vacuum signal feedthrough
Flanges
Main sealing
Window joint
Vacuum port
Johannes Treis / Halbleiterlabor der MPG

4. Johannes Treis / Halbleiterlabor der MPG
Example
Outgassing data from CERN:
6 layer FR4 PCB (vacuum bakeout)
Outgassing proportional to surface area
Gas load ~ 5 x (mbar l) / s cm2
Housing (estd.):
Assembly Volume ~ 6 x 15 x 20 cm3 = 1.8 l
Housing volume ~ 10 x 17 x 22 cm3 = 3.75 l
Free volume ~ 1.95 l
Inside pressure of 0.1 mbar
Gas load (PCB area only):
Total surface ~ !200 cm2
5 x (mbar l) / (s cm2)
6 x 10-7 (mbar l) / s
~ (mbar l) / d
Gas load increases pressure in free volume by mbar
25 % of total daily allowance created by PCB area!
Gas load budget tight?!?
Total PCB area:
Inboard IIC ~ 300 cm2
4 hybrids ~ 64.5 cm2 = 258 cm2
Phi pulsers ~ 2 x 24 cm2 = 48 cm2
Total area ~ 600 cm2
Johannes Treis / Halbleiterlabor der MPG

5. Johannes Treis / Halbleiterlabor der MPG
Caveats
Source: CERN
Thomas: Gas load < 4 x10-9 (mbar l) / (s cm2) for uncleaned, unbaked ML PCB w/ solder resist
Johannes Treis / Halbleiterlabor der MPG

6. Johannes Treis / Halbleiterlabor der MPG
Next steps
Understanding requirements:
Rationale behind requirement
What does really hurt?
Showstopper or nice to have?
Testing & qualification:
Agree on qualification procedure for used materials
Test all materials in terms of outgassing before use
Discuss possible countermeasures:
Use of suitable materials and techniques
Ensure vacuum compatibility by design
Minimize potential sources of gas load
Advanced cleaning and bakeout cycles
Use of getter materials?
Use of “cold traps”?
Share existing knowledge at MPS
Johannes Treis / Halbleiterlabor der MPG