1. BL 8.2 MIRROR UPGRADE Front End Mirrors 8.2.1 (M101) and 8.2.2 (M201)

2. Reasons for replacement: To take advantage of improved beam quality after implementation of top-off- mode.

3. Scope of Review New “plug and play” replacement design to minimize down time by performing installation on two day shutdown.

4. Differences between the new mirrors and the old: New mirrors are longer to reduce the effects of the mirror benders on the ends of the mirror. New mirrors are of a two piece, frit bonded design, with internal cooling. Optical surface roughness will be improved. New mirrors will have new, external to vacuum, mirror bending, enabling fine tuning of mirror radius in operation.

5. Existing Mirrors

6. New Mirrors

7. BENDING DRIVE

8. Given: The horizontal mirror spring for the bender must provide a torque of 7750 ounce inches to each end of the mirror in order to bend it to the correct radius. Find: Suitable motor and gearhead to deliver required torque with a factor of safety near twice the required torque. Solution: A Parker step motor will generate 65 oz.-in. of torque, however a clutch will limit this torque to 50 oz.-in. A 50:1 gearhead with an efficiency of 85% will be used to raise the 50 oz.-in. to 2125 oz.-in. The gearhead will drive a drive screw with a thread pitch of 5/8-18. While this thread will provide a further mechanical advantage of 33:1, its efficiency is only about 17%, which is reduced to 5.6:1. This will increase the torque delivered to 11,900 oz.-in. This delivered torque provides a factor of safety is 1.54. CALCULATION OF TORQUE REQUIREMENTS FOR BL 8.2.1 MIRROR BENDER

9. WATER COOLING

10. SPRING DEFLECTION

11. STRONGBACK DEFLECTION