the pressure level with the ionic pump was limited to ~ 1.5 .10**-7 mbar after several days of pumping, due to some leakage located on the bottom screws of the large flange.
so we decided to reopen the flange and change the copper joint.
we did a new leakage test, and after tightening properly the screws, it seems there is no leakage anymore.
so, we started the ionic pumping in the morning (several starts and stops to clean the ionic pump with the turbo pumping), and at 3.30 pm, we closed the turbo/vessel valve.
the vacuum level is at 2.3.10*-7 mbar.
let's see how much it is tomorrow morning to have an estimation of the time needed to reach 2.10**-8 mbar (in the vessel), which should reduce to 5.10**-9 once the ring/vessel valve will be opened (the ring has roughly the same volume as the two vessel volumes).
| Ronic Chiche wrote: |
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This afternoon, we installed a new M1 mirror, the only one for which the box was not already opened.
as the mirror should be "brand new", as the LMA has packaged it, we decided not to clean it with ultra-pure water and to install it out of the box.
we realigned it with the iris previously installed for that purpose.
primary and turbo pumping are in process. one has to wait until the vacuum level is low enough to start the ionic pumping and to reopen the isolating valve.
let's cross our fingers...
| Ronic Chiche wrote: |
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this morning, with Daniele, we took some images of the M1 mirror HR surface :
1- large image span of the mirror surface (~center) before being cleaned :
one can see a lot of spots
2- zoom in on some spots in the middle of the mirror.
Daniele saw 2 suspicious spots among many.
difficult to be sure if it's only some dust or if it's some damage
3- large image span of the mirror surface after being cleaned with the spin coater machine
only the 2 suspicious spots remain, all others have been washed.
4- zoom in on the 2 suspicious spots
if one compares with the image before cleaning, one can see the spots are much larger
5&6- zoom in on the 2 suspicious spots separately after a 2nd cleaning process with the spin coater,
it seems the spots are even a bit larger than before
conclusion : it seems that these spots are presently showing some damage on the mirror surface.
it is strange that there are 2 in the same time.
one possible explanation is that, as we had to move the z-axis motor before, and we know that the mechanics are rusty, it's possible that it released some metallic particles on the mirror surface.
and 2 were in the beam area....
| Ronic Chiche wrote: |
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after trying to increase the power and after moving S3 to try to change the size of the beam on the mirrors, the FPC power suddenly droped.
so, we need to remove M1 to check if it has been damaged.
we placed an iris in reflection of the FPC to keep the alignment for the new mirror M1.
the alignment has been done with an iris and the amplifier at 10% (to get a quite round beam) and the beam profiler.
once the iris is almost closed, the alignment is good, using the diffractions rings.
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