Mask/Select All
Edit/Copy
Enter Channels palette and Add New Channel
Edit/Paste/Paste As New Selection
Mask/Remove
If you want to copy the channel to the object palette as a new object.
Select channel in channel palette
Mask/Select All
Edit/Copy
Select an object in object palette
Edit/Paste/Paste As New Object
Photoshop is much easier for this sort of thing, but it should all be possible in PP.
Sark