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HL-LHC WP13 BI Meeting #1 - Jan 2017
Indico : https://indico.cern.ch/event/608554/
Present: Michal, Christos, Ray, Alberto, JJ, Rhod, Adriana, Sotiris, Gerhard, Thibaut, Enrico, RHUL by video link
E/O BPM Status (Alberto)
- 2 Possible set-ups
- Polarizer/Analyser
- Interferometer
- Should be more sensitive
- SPS prototype set-up
- LiNbO3 crystal
- 750nm wavelength with narrow bandwidth laser <200kHz
- Polarisation maintaining fibre for incoming path and normal single mode fibre for the outgoing path
- Photodiode signal amplified by 28dB
- Switch from negative to positive signal due to incoming polarisation state observed
- EM Simulations
- Big drop when EM field reaches crystal due to change in dielectric constant of the material 1/30
- Expecting 1.27uW but measures 5 times less ~230nW
- Needs more careful calculation & set-up optimisation before drawing conclusions
- Test Bench
- Coaxial line being set-up in RHUL
- Now functional ready for testing
- Next Steps
- New PU design
- Longer crystal, metallic button on beam side & grounding on outer side
- Overall increase in sensitivity of factor 10 expected
- Longer term
- Look at interferometric detection system
- Look at waveguide structures in very thin crystals to enhance field across crystal
- New PU design
- Questions / ACTIONS
- Rad hardness of crystal?
- SPS crystal did not suffer after 1 year in the machine
- Irradiation tests to be foreseen
- Comparison of expected performance from HT & E/O
- Ballpark figure required
- Rad hardness of crystal?
New IR BPM Status (Thibaut)
- Locations
- Now all placed >57cm (2ns) from long range encounters
- https://espace.cern.ch/HiLumi/WP15/default.aspx
- Open questions
- Can warm BPM in front of D2 be placed inside D2
- Aperture of BPTX & APWL
- BI & RF to decide on APWL or not
- Design of BPMQT
- Q2a, Q2b,Q3,CP,D1
- Inermet shielding requested for reducing radiation to front-face of Q2
- 2W deposited power in BPM from collision debris - needs cooling
- Latest design
- Octagonal shape
- Transitions are inserts welded on
- Inermet on outside of 1mm walls
- Is 1mm too thin?
- Needs to withstand pressure differential
- Can the pick-up be entirely out of inermet?
- How to braze/fix transitions & feedthroughs
- May need to look at other high Z materials - Tungsten, Molybdenum?
- To do
- Thermal calculation / heat load & cooling
- Coating for RF - can we do this with inermet?
- Need input from MME
- Stripline design
- 3D printing does not seem feasible in terms of tolerances
- To be checked with ML
- New "buildable" design being investigated by Michal
- Include feedthroughs
- 3D printing does not seem feasible in terms of tolerances
- Plans
- Functional specifications by March 2017
- Report back in April WP13 meeting
- First design by end 2017
- Prototype BPM in 2018
- Functional specifications by March 2017
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