Minutes BWS Design Review: PSB Beam Wire Scanner -- 19th January 2016 --
Participants: Raymond Veness, Bernd Dehning, William Andreazza, Dmitri Gudkov, Paolo Magagnin, Jose Luis Sirvent, Nicolas Chritin, Jose Antonio Ferreira, Rhodri Jones, Emilien Rigutto, Jan Hansen
Agenda ( https://indico.cern.ch/event/483648/
)
1. Review of the PSB Beam Wire Scanner Prototype Design (N.Chritin)
- Flange and mobile parts Weight: 17kg
- Vacuum Tank Weight: 23kg
- Ports CF100 included on vacuum tank for vacuum pump and top viewport
- Inner diameter of the beam pipe circular 120mm
- Margin between the tip of the fork and tank: 20mm
- Margin of 27mm on fork position and the end of the shaft.
- Question of the small port at the end of the shaft:
- Requested by Impedance.
- Rhodri asks if this has been simulated.
- Dmitry says that they will insert the feedthrough with cylindrical pad inside the shaft axial hole and there is a radial gap of 2 mm between this pad and the shaft internal wall.
- The configuration was discussed with Fritz Caspers and Christine Vollinger and approved.
- We should check this with Benoit.
- Discussion: RF Feedthrough ( See Drawing)
- Unclear what there will be installed on this Feedthrough: It is required to know the geometry of the device and cabling required.
- Likely there will be an antenna inside the shaft for RF purposes
- Study required for mounting-dismounting process
- Drawings available on line under CDD/EDMS: "PSBBWSRA%"
- Thin walls of the stepped vacuum chamber:
- Break and Resolver : 0.3mm
- Motor/Rotor : Vacuum chamber = 0.4mm, total gap Stator/Rotor = 0.7mm and 80mm long
- Paolo has done the buckling analysis. The configuration was already ok with t = 0.3 mm. Also the production is easier if the wall thickness is 0.4 mm.
- Materials for large pieces on both instruments and flanges have been ordered for 6+1 assemblies in December. DN273 flange.
- Question on the bake out and test procedure for the assembly of the optical system and the window. Is there a sleeve(membrane or glass – body interface)on the window?
- Maybe errors in Viewport Model : (Jose will send the real Viewport to Nicolas for inspection)
- Do we need blocking screws?
- Nicolas has one the main axis screw, but not on smaller screws.
- We will fix them with a torque wrench.
- Preparations for scanner mounting/dismounting tool done.
- Installation - will be close. Should consider an installation jig.
Comments:
- Nicolas can expect to get the drawings signed before the end of the month. Emilien says they can look at drawings before they are signed.
- Tubes for guiding kapton wires after entering on the shaft? (to avoid wires breakage)
- Stepped vacuum chamber alighning mechanism fixed with 6 screws
- Significant weight reduction on PSB proto with respect to SPS Proto (from 35kg to 17kg)
2. Beam Wire Scanner Equipment: Motor (Dmitry Gudkov)
3. Beam Wire Scanner Equipment: Forks, Disk and shaft optimization (Paolo Magagnin)
- Maximum offset on the wire´s edges PSB 16.9um , SPS 20.3um
- Shaft optimization:
- Inertia Now 1.1e-3, Before 8e-4
- Disk Optimization:
- Inertia 1.7e-4
- Optimization on the optical disk --> Final disk will contain around 6-7 arms.
- Disk is optimized to have a retardation in tangential direction less than 10um
- Decision to make about disk, material, fabrication process.
- Manufacture of the disc? Turn then mill then EDM the cut-outs? Stress relieve? Not sure. Concerns about the run-out of the disc? Needs to be 0.1 mm. 196 mm external diameter.
- This would be another good candidate for 3D additive machining with automated form optimisation! (R.Veness)
- Disk Vibrations simulations would be useful:
- Simulations with nominal acceleration and small disk mounting imperfections
- Paolo confirms that vibration simulations are possible.
- Discussion: Tube inside forks for kapton wire guiding:
- SPS proto has no tube for Kapton wires.
- There are a second series of forks with tubes.
- Discussion: Shaft on titanium.
- Steel higher elasticity.
- Difference in terms of inertia, small compared to steel.
4. Beam Wire Scanner Equipment: Optical System (Jose Luis Sirvent)
- Due to the larger disc, we have gained significantly in the number of slits (20’000 to 30’000) so resolution significantly improved (Resolution 314uRad --> 209uRad)
- Dmitry asks if possible to increase slit spacing to ease manufacture? Jose says probably could if necessary. However, precision of slit position is important and should not decrease (accuracy ~ 25urad).
- Re-Design of PSB and selection of new lenses system shown.
- Tests with Stainless Steel 304L and Aluminium Samples with different roughness performed:
- Laser treatment on samples was OK : In general all tracks were usable by the system (to decide which one shows better characteristics)
- Surface treatment of samples needs to be improved (light dispersion and optical signal completely lost in many areas of the disk)
- Next steps to improve the surface finish by diamond machining and/or electro-forming
- Bernd ask if possible to perform surface treatment with polishing (as done with glasses).
- Need to aim for Optical standards
- Ideal Specifications based on high quality optical mirrors: 20-10 Scratch-Dig, flatness lambda /10 @ 1310nm // Parallelism: ≤ 3arcmin // Rotation Run-out: +-100um
- Check Specifications meaning: http://www.newport.com/Optical-Surfaces/982742/1033/content.aspx
5. Experience of BWS in SPS Maintenance (William Andreazza)
- Very useful and valuable experience with SPS proto
- Breakage of glass disk --> Metallic disk selection, type of glass disk fixation and screws used.
- Plan to use Hybrid bearings with reduced radial gap.
- Ray asks if the steel cages of the hybrid bearings could seize in place after some use under vacuum. To be looked-at.
- Fatige tests performed over the SPS BWS operational life showed satisfactory results
- Accumulation of tolerances lead to friction of one screw with the stepped vacuum chamber (axially), screw type was changed on SPS intervention (Jan 2016).
- Generally happy with the way it was assembled and works.
6. Discussion:
- The "Disk Vibration" problem found on the SPS proto was also found in Lab proto (keep in mind for PSB and disk design)
- Proposed to make Drawings control at the end of January
- No blocking factors found for production
- Aiming for 3 Instruments and 2 Vacuum tanks (Offer requested to MME)
- 1st Goes to installation, 2nd for RF and Vacuum testing, 3rd for laboratory with a holding frame
- Required planning for PS prototype:
- Check budget availability for PS and formal request
- PS installation taken as an option
- Schedule of Motor tests on test-benches to confirm (Bernd, Jonathan)
- We need to start design of support system and the integration into the zone.
- Nicolas will discuss with JM Lacroix.
- Organization of the ECR for the installation Survey required - invite to another meeting.
7. Design Observations Collected:
- Think about other processes for reflective surfaces: Material deposition, Surface polishing.
- Encoder disk fabrication process to avoid deformations must be well studied and defined.
- What about activation of Cobalt (Rotor magnets)? Ray says does not appear to be an issue, was investigated by student in 2015.
- Concerns about bake out on viewport and material dilatation
- Concerns about aligning optical system before and after bake out
8. VSC Requests and recommendations:
Observations:
- We would recommend the DN35CF flange foreseen for the RF is changed to a DN35CFQ if this flange has to be opened each time you have to change the wire.
- The 4 DN16 windows must have direct access for leak detection.
- The shown window has no membrane, which are important for the installation and in case of bake out.
- We expect the tank will require damping plates which could be important for the total outgassing. This information is important to calculate the extra pumping speed.
- Information concerning the central RF unit might also have an effect on the required pumping speed and again important for the vacuum calculation.
Request:
- In the LIU-PSB all new installation concerning vacuum should be send for control 3. In TE/VSC the control 3 for new material is done in a dedicated vacuum design approval meeting where the 3D model and drawings if existing should be presented.
Recommendation:
- To install the FWS an off-set in the big flange might improve the dismantling and reinstallation of the wire scanner.
- It is important to get the motor vacuum tested as soon as possible (end of YETS 2016)
- Information about the costs of the extra pumping required will be received on the middle of next week (25-29 January)
9. New Actions:
Action |
Responsible |
Feedthrough Check (Done!) ECR for PSB |
Bernd / Fritz |
Validation of out-gassing of the motor magnets (February) |
William |
Motor Testing on test-benches |
Jonathan |
Vibration simulation and studies on Disk |
Paolo |
First set of drawings for Emilien Send drawings for approval Second control at beginning of February |
Nicolas |
Viewport model and drawing check New samples tests (Diamond machining and electro-forming) |
Jose Luis |
Request details about device on RF Flange and cabling |
Dmitry |
Topic revision: r4 - 2016-01-22
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