How to change slit masks of FOCAS

Note:

Any troubles in mask exchange may cause serious damage of the MOS exchanging system. Please double check every step of the procedure. If you find any troubles/questions, please call SA (Ohyama) for assistance. Check notes at the bottom of this document.

1: Open the mask entrance of FOCAS.



Check that all ten (10) mask holders are stored back in the stocker. If you find a space within the stocker (i.e., any missing holders within the stocker), it means that one of the mask holders is still placed on the focal plane (at the center of the FOCAS). Ask SA for retracting the masks before you remove the stocker.

2: Release two silver clamps at left side of the stocker.

The following picture shows the position of the two clamps at release position. Follow the instruction shown on the mask entrance door.



3: Remove stocker out of FOCAS.

Pull the stocker out. It will move along a slider.



Then bring the stocker upward to release the stocker out of FOCAS. Note four holes (at bottom of the stocker) and pins (on the slider, which are not clearly seen in this picture).



The stocker should be placed on a table as shown below (base plate at the bottom), or two handles at bottom. If not, all the weight will be supported of tiny pins at silver release levers near the handle, which is not recommended.


 

4: Removing mask holder from the stocker

Press release levers for masks which you wish to remove. Numeral labels (from 1 to 10, in yellow) show the mask ID. Press two levers of the same ID on both sides of the stocker at a same time. Then pull the mask holder out gently from the stocker.

Here is the zoom up image of the release levers.

 

5: Exchanging masks within holder

Unscrews the top panel of the holder There are 8 tiny screws around the holder.
The holder without the mask (a carbon sheet) looks like this.

When installing a new mask (a carbon sheet) within the holder, align all "S" marks of the holder (bottom plate, top plate) and the mask, like this.


Then, screw all 8 screws to cover the top panel of the holder.

6: Holder installation to the stocker

To install holders into the stocker, press two levers, and insert a mask holder completely toward the end. Then bring it out a little until two pins are inserted into holes of the side walls of the mask holder. When correctly stored, you will hear a small "click" sound. Make sure that all ten (10) release levers are back at the original position (as shown in a picture of section 4).

7: Stocker installation

After changing all masks/holders, bring the stocker back to the FOCAS in an opposite way of  3 above. Push the stocker into the FOCAS toward the end. Then fasten two clamps on the left side of the stocker. Follow the instruction shown on the MOS entrance door. Do not forget to close the MOS entrance door.

8: Report

Please report the results of your jobs to SA (Ohyama, ohyama@subaru.naoj.org) by e-mail. If you find any problems, please feel free to call SA (Ohyama) at any time.

Note 1: Proper installation of masks/holder is crucial. Check the masks/stocker once more with care before finishing your job.

1: If you install masks/holder in a wrong direction or they are installed not securely, slit handling mechanism installed within the FOCAS may be broken in some serious ways. Please check the proper direction/position very carefully.





All the above pictures show the correct position of the masks within the stocker.
  1. Follow the "S" mark for proper directions. If every mask is stored correctly, all the yellow lines are shown on the right side of the mask when seen from behind the stocker.
  2. All release levers on both sides are at the close position, i.e., all pins of the levers are in the holes of the masks. If one of the levers is found not in the above condition, check the mask positions within the holder.
  3. Generally, all the conditions/positions of clamps/release levers/paint marking should be similar for all masks/holders. Exception generally indicates something wrong.

Note 2: Some other notes

  1. All ten (10) masks/holders should be installed into the stocker every time to maintain the weight balance within the holder.
  2. Avoid oil/dusts/debries on masks/holders. The masks will be installed near the FOCAS main optics. Use blower to remove dusts on masks.
  3. Handle the mask holder gently. Warp/distortion of the holder may cause the damage of the mask handling mechanism within the FOCAS.
  4. Some masks look similar to each other at a glance. Please check carefully which mask should be installed at which stocker position.