1. Summary of Presentation 1. Tolerances i. Vertical tolerances on BPMs (rf-BPM: ± 0.2μm, user BPMs: ±0.1μm, and X-BPMs: ± 0.1μm) ii. Tolerances on magnets’ motion (vertical: < 0.025 μm, horizontal: < 0.15 μm) iii. Tolerance on girder: < 0.07 μm 2. FE thermal analysis on the thermal deformations of girder, vacuum chamber and BPM support stand under conditions of air and water temperature fluctuations of ± 0.1 ºC and ± 0.05 ºC, respectively. Results showed the displacements were within tolerances. They suggested that BPMs need to be located near the fixed or flexible supports. 3. Natural frequencies of the first two vibration modes for the girder-magnet assembly are 63 Hz of rolling mode and 79 Hz of twisting mode. Stability of Mechanical Systems - Dr. Sharma

2. Temperature Stability 1. Temperature stabilities * Five mechanical rooms will supply totally 15 air loops to the storage ring tunnel. * Temperature stability +- 0.1 C with one hour cycle or less is easily achievable. * Temperature drift <0.02 C over two weeks is also easily achievable. * When the tunnel is in operation, a minimum of outside air will be used to improve temperature stability. The tunnel will be pressurized slightly. 2. Spatial temperature gradient within the tunnel * It is not critical as long as they do not affect magnetic field quality.

3. ** The time constant (thermal) of the user BPM support stand may not be that much of a problem. - What is needed is 2-3 days (ESRF model) between starting up the machine after a long shut down and sending beam to the users. - During short shut-downs it can be controlled with a resistive heater wrapped with insulation and control BPM Temp. to +/- 0.01C. ** The beam tube may deform due to internal heating from reflected internal radiation and distort BPM position. - The damping wigglers may give big problems in this area and must be studied. - Cooling method on reducing the temperature-induced problems has to be designed. ** User BPMs should be treated as metrology components. BPM Stability

4. 1. The estimate of resonance frequency for the girder could be off by a factor of ~ 2. - Prototype test is necessary. 2. How to stiffen the girder * Use welded plates about 0.5-m apart to stiffen the girder instead of cross bars. * Bolting concept needs to be reviewed. (APS experience shows that with practice bolted connections can be made accurately. So while tightening the magnet or girder bolts after alignment errors on the order of <10 μm will be observed.) Vibration

5. 3. Flow induced vibration --Water * Process water flow velocities in the headers and magnet coils will be kept reasonably low to mitigate flow- induced vibrations. -- Air * Flow rate of air 50 ft/min in the tunnel. At the outlet 800 ft/min. * Perforated grill duct will result in uniform air supply/ minimize turbulence.

6. Condition defined? (for highly accurate dimension) ENVIRONMENTAL **Operation temperature and humidity (including machining period) must be defined. **Other interferences, such as aging and creeping of the girder itself, or the interference from the “contact” with vacuum chamber need to be evaluated.

7. Different Frequency Domain? The stability requirements for low frequency vibration need to be identified. It is suggested that the effect to electron beam be simulated. Particularly, the relative position of beam line components are still affected when frequency <4Hz. It should be avoided in beam line component design not to touch the vibration resonance line. For IR beam line, the vibration at high frequency will influences the experimental result.

8. Technical issues, risks and critical path areas? Technical issues on alignment of the magnets and girders need to be identified. (Not the concern of this workshop.) Girder prototype is necessary to be fabricated and tested.

9. Resources (tools, expertise, etc)? Is in-house expertise enough in thermo and vibration, and CFD analyses? Flow pattern simulation for the storage ring tunnel and the experimental hall should be evaluated. NSLS-II has requested help from TLS - check necessity.