Beam-line 11
Beamline 11.0.2 MES Monochromator 2/27/03
Identified problems or issues and upgrade solutions and/or resolutions:
1) Improve access to sine-bar flexure area at the drive linkage interface. The access was very limited and the configuration of the hardware resulted in a difficult assembly process.
Resolution and/or solution: Modifications to the vacuum chamber would be extensive and affect numerous other components and is not advised. To ease connection of the conflat on the sine arm end, the bellows on the vacuum-guard tube for the sine arm water line has been reduced in diameter and moved toward the conflat connection on the feed thru end.
2) Spring stiffness of the clamping springs holding grating to the grating cradle. The clamping pressure was just adequate to overcome gravity and coolant tube and bellows forces.
Resolution and/or solution: Increasing maximum spring load from 15 lbs to 25 lbs and modify nut to receive the new spring. Modifying adjuster body to eliminate potential binding between body and spring spanner nut, and replace spanner nut with hex nut. Reduce wall thickness of Teflon water feed tubes to grating (reduce the lateral load on the optics).
3) Level interference with bellows. The periscope on the arc second level interferes with the bellows during measurement.
Resolution and/or solution: Lower the level mounting surface and mounting features by 0.5 inches.
4) Studs and nuts were required on the interface between the air-guard bellows and the optic. The ‘cuff’ on the bellows that make up the air-guard between the two optics and their respective water manifolds was too short, thereby precluding the use of machine screws which was the preference of the vacuum technician and the design engineer.
Resolution and/or solution: This issue was a fabrication error and will be resolved at that level. Additionally, the bellows on all optic connections will be reduced in diameter to match the new sine arm tube bellows outlined above which should eliminate this issue completely.
5) Increase the adjustment range of the pre-mirror with respect to its cradle. In order to increase the range of adjustment, the nominal gap between the mirror and the mirror cradle must be increased or the counter-bores that provide clearance to the mirror kinematic mounts must be deepened.
Resolution and/or solution: Lower height of the mounted v-groove and increase depth of the counter-bore in cradle.
6) Increase the length of the bellows on the air-guard/water tube enclosure. The vacuum technician had difficulty keeping the Teflon water tube properly seated in its respective port while installing and connecting the air-guard assembly.
Resolution and/or solution: The bellows length will be increased along with the resizing outlined above
7) Improve mirror and grating mask fabrication. The mirror and grating mask coolant lines are somewhat difficult to manufacture with precision. The orientation of the conflats with respect to the tubing is critical.
Resolution and/or solution: Reduce the manifold bore receiving the coolant tubes and add a final machine OD of the coolant tube nipple after welding and brazing.
8) Eliminate the large radius on the mirror mask.
Resolution and/or solution: (Also see 7). Remove radius and L-shape leg. Simplify design to a flat plate.
9) Add hard stops to limit the travel of the linear stages. During the early stages of beam-line commissioning a limit switch malfunctioned and the sine arm was driven into the chamber wall. The force of the impact caused a leak in an air-guard flange and damaged one of the flexural pivots.
Resolution and/or solution: Add external, adjustable hard stops. Remove gear reducers and change linear stages to non-ball screw type having a finer thread pitch. Buy replacement stage as soon as possible and test for stick-slip and fine positioning capabilities.
10) Shorten the linear slides. The current design requires 6” linear slides which are rather large and bulky. Moreover, the required translation is only slightly more than 4”. With a slight modification to the sine-bar assembly, it may be possible to reduce the required range of motion to 4” or less. As an alternative, it may be possible for the vendor to provide a custom length slide for a small additional cost.
Resolution and/or solution: Change linear stages to non-ball screw type (noted above). This will reduce their overall length by one inch and eliminate any reduction in travel due to component interference.
11) Main Flexural pivots issues: Ease flexure pivot replacement and adjustability:
Resolution and/or solution: Easing flexure pivot replacement will not be possible. Adding spanner holes to the ampco pivot clamps should ease the rotation adjustment of the pivots clamps, and supply tool.
12) Sine arm feed thru flange weld: Difficulties in welding flange to chamber.
Resolution and/or solution: The original design required a butt weld directly between the flange and the chamber. Due to a detail drawing dimensioning error, the tin seal clamping holes were drilled through the vacuum wall. To avoid a difficult correction weld near the flange weld, noted above, a cuff was added to the flange and welded to the chamber. This placed the errant through hole on the air side of the chamber. This corrected the problem but created a second troublesome weld which took several attempts to seal. The solution is to return to the original design and butt weld the flange in place, correct the drawing depth dimension, and increase the size of the font on the drawing stating “DO NOT DRILL THRU”.
13) Sine arm drive kinematic attachment: Modify the sine arm to make it insensitive to lateral movement.
Resolution and/or solution: No changes. This issue has not been shown to be the cause to any problem. A lateral load was applied to the mirror sine arm and the measured displacement of the invar mount was negligible.
14) Sine arm length reduction: Reduce sine arm travel to match 4-inch linear stage.
Resolution and/or solution: Requires extensive modifications to the vacuum chamber and numerous other components and is not advised. Problem is solved with proposed changes to the 6-inch travel linear stages noted above.
15) Invar mount stiffness: The invar mount has lateral movement during the rotation of the mirror. The displacement measurements showed that both sides of the invar mount had some micron level lateral movement but the direction of the movement was not recorded. The cause of this motion is unclear.
Resolution and/or solution: Without understanding the cause of the movement in the invar mount, it is difficult to offer a solution. Stiffening of the invar mount would seem to be the only solution with any merit. Increase the width of the gussets and add a cross member to connect the vertical members.
16) Burrs on components: Burrs on the waterline components damaged o-rings and Teflon tubing during assembly.
Resolution and/or solution: Remove burrs prior to assembly.
17) Port reduction and flange type: Reduce the number of flanges on the chamber and switch to AL-SS type.
Resolution and/or solution: Reduce the number of flanges and modify all flanges to Stainless-to-Aluminum type. Issues about cuff length can be address by vender. They can either order custom flange or weld on cuff extenders.
18) Optic angular range: The angular range of the grating was reduced due to the interference of the linear stage with the chamber cross slide bearing guide. The alignment of the optics would be easier if we had the ability to set them horizontal.
Resolution and/or solution: Increase the angular range to include zero degrees or horizontal on both the pre-mirror and grating for optic alignment purposes. Revise grating angular range to 0-10 degrees and 0-7 degrees for the pre-mirror.
19) Optical mounting v-groove alignment: Due to a misunderstanding in the application of these pads, they were improperly assembled.
Resolution and/or solution: No design change. In addition to the current method of v-groove alignment, shims will be provided for final alignment. Torque specification will also be added to the drawing.
20) Grating sine arm attachment: A #6 screws holding the grating sine arm to the grating cradle broke during assembly.
Resolution and/or solution: Increase screw size from #6 to 1/4"
21) Mask/Mirror coolant flow: Each mask and mirror set use the same coolant supply and this requires tuning of their relative flow rates.
Resolution and/or solution: Measure the coolant flow rate in the mask and mirror and apply a flow limiter in the mask coolant line as needed.
22) Difficulties adjusting “cam adjuster” (Ampco18):
Resolution and/or solution: Add spanner holes for easy adjustment, and supply spanner wrench. Increase outside diameter of “cam adjuster” in order to facilitate the generic aspect of this design (to simplify bearing spacing changes).
23) Possible slippage of sine arm feed-thru bellows cover:
Resolution and/or solution: Add detent on cover and receiving flange.
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