Vacuum Window Fabrication and Installation Procedure

This procedure must be followed for installing any Hall C spectrometer vacuum window. One of the responsible personnel must be present during all steps of fabrication and installation. Although the procedure below is specifically for the HMS large window, it is the same for the small HMS and for both SOS windows, except as noted.

1. Place window material, thin Mylar side down, on a large flat, extremely clean, surface (such as the marble table in EEL 126 after being washed).

2. Place window flange ring (also freshly cleaned) on top of material and trace outer circle (or rectangle for SOS) and bolt holes with transparency marking pen.

3. Remove flange ring and cut out circle using Kevlar cutting shears.

4. Cut out bolt holes using appropriate (custom-made) drill press tool. For the larger windows, this is a two person job as one is needed to hold the material up so that it can't be nicked by the side of the drill press table while the other concentrates on cutting the holes.

5. Clean the aluminum flange ring thoroughly and wipe with isopropyl alcohol. For all but the HMS exit window, the flange ring and window should be brought to the hall. For the HMS exit window, continue as outlined below from step 6 on. For all other windows, install flange ring and window unit to spectrometer vacuum flange using standard O-ring vacuum seal practice (i.e. clean all surfaces thoroughly with alcohol, apply vacuum grease, tighten in star pattern, etc.) All bolts should be torqued to 50 ft-lbs (40 ft-lbs for the SOS exit window). There must be a correctly tightened bolt in every bolt hole. Continue to step 17.

6. (HMS exit window) Clean Viton O-ring with isopropyl alcohol and apply vacuum grease as is standard for vacuum connections.

7. (HMS exit window)Place Viton ring on HMS vacuum extension piece, composite window over ring, and aluminum flange (clamping) ring over window. Bolt together at four corners.

8. (HMS exit window)Place and tighten bolts in a star pattern as appropriate for standard O-ring vacuum seals.

9. (HMS exit window)All bolts should be torqued to 50 ft-lbs (40 ft-lbs for the SOS exit window).

10. (HMS exit window)Using standard O-ring seal technique, mount other side of vacuum extension piece on aluminum blanking flange.

11. (HMS exit window)Using a transparency marker, trace the flange circle onto the Mylar/Kevlar window.

12. (HMS exit window)Begin vacuum pumping on extension piece.

13. (HMS exit window)Note any creep of traced ring and window deflection. Check window for visual abnormalities or imperfections.

14. (HMS exit window)Leave under vacuum for at least 1 hour. Repeat step 13.

15. (HMS exit window)Bring vacuum extension piece back to atmospheric pressure and remove blanking flange.

16. (HMS exit window)Being extremely careful not to touch the Mylar/Kevlar window, install extension piece on HMS spectrometer in hut using standard O-ring vacuum practice.

17. Clear detector hut and pivot area for initial pump down. Do not allow entry for anyone other than the above named personnel to these areas until a vacuum of at least 50 mTorr is achieved.

18. Begin vacuum pumping.

19. One of the above named personnel should check and note the window deflections, recheck bolt torques, and generally look for irregularities in the window deflections, before allowing general entry to the detector hut or pivot areas. That person should wear ear protection at all times while near windows. Bolts should be retorqued if necessary.

20. Place a clearly visible tag near the vacuum window indicating date of installation, estimated date of removal, and names and phone numbers of contact personnel.

21. Recheck bolt torque, vacuum, and window deflection again a couple of hours later (again, this should be done by qualified personnel only, wearing hearing protection). Retorque bolts if necessary. If the window deflection has increased more than 3/4 inch, begin the entire process again with a new window.

22. The windows should be changed as close to every 6 months as reasonable given experiment run scheduling considerations. It is not necessary to stop a run to change the windows, but they should be changed as soon as possible thereafter.