40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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Entry  Mon Jul 4 10:30:37 2016, ericq, Update, General, Preliminary vent plans 
    Reply  Tue Jul 5 17:14:02 2016, ericq, Update, General, Vent progress noOsemSide.JPGOSEMside.JPG
       Reply  Tue Jul 5 19:10:41 2016, rana, Update, General, Vent progress jumpEvent20151105.png
          Reply  Tue Jul 5 21:51:35 2016, ericq, Update, General, Vent progress 
             Reply  Tue Jul 5 23:38:42 2016, gautam, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation image.jpeg
                Reply  Wed Jul 6 22:58:01 2016, gautam, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation 
                   Reply  Thu Jul 7 00:25:07 2016, ericq, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation 
                      Reply  Thu Jul 7 10:49:03 2016, gautam, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation UL_glitchMon_Striptool.png
                         Reply  Fri Jul 8 11:35:45 2016, gautam, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation coilGlitchMon.png
                            Reply  Fri Jul 8 11:48:09 2016, Koji, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation 
                               Reply  Fri Jul 8 14:03:26 2016, ericq, Update, General, ETMX removed from suspension zoom.jpg
                                  Reply  Fri Jul 8 16:33:26 2016, ericq, Update, General, ETMX removed from suspension 
                                     Reply  Fri Jul 8 20:44:09 2016, Koji, Update, General, ETMX removed from suspension 6x
                                        Reply  Sun Jul 10 15:38:01 2016, ericq, Update, General, ETMX in guiderod/standoff gluing fixture 6x
                                           Reply  Tue Jul 12 16:08:00 2016, ericq, Update, General, ETMX ruby guided gluing 
                                              Reply  Wed Jul 13 21:13:51 2016, Koji, Update, General, ETMX guide rod gluing / ETMY Magnet gluing 13x
                                                 Reply  Thu Jul 14 22:29:57 2016, ericq , Update, General, ETMX guide rod gluing / ETMY Magnet gluing 
                                                    Reply  Fri Jul 15 16:23:51 2016, ericq , Update, General, Gluing setbacks IMG_2768.JPGIMG_2771.JPG
                                                       Reply  Tue Jul 19 16:39:29 2016, Lydia, Update, General, ETMX magnet gluing/guiderod excess glue removed P7190201.JPGP7190203.JPG
                                                          Reply  Wed Jul 20 13:58:55 2016, Steve, Update, SUS, SUS damping out of vac chamber ETMXrack.jpgfromETMX-satBox.jpgsusDampingSatboxCab.jpgsusDampingSatboxCabl.jpg
                                                          Reply  Thu Jul 21 17:01:59 2016, ericq, Update, General, ETMX magnet gluing/guiderod excess glue removed 
                                                             Reply  Fri Jul 22 23:03:23 2016, gautam, Update, General, ETMX suspension - progress IMG_2828.JPGIMG_2826.JPGIMG_2821.JPGIMG_2822.JPGIMG_2823.JPG
                                                                Reply  Sun Jul 24 03:43:56 2016, ericq, Update, General, Magnet positioning 
                                                                Reply  Mon Jul 25 13:01:49 2016, ericq, Update, General, ETMX suspension - progress IMG_2829.JPGIMG_2830.JPGIMG_2831.JPGIMG_2832.JPGIMG_2833.JPG
                                                                   Reply  Mon Jul 25 13:47:19 2016, rana, Update, General, ETMX suspension - progress 
                                                                   Reply  Mon Jul 25 17:01:54 2016, Steve, Update, SUS, ETMX suspension - progress ITMYside2011.JPG
                                                                   Reply  Mon Jul 25 20:37:46 2016, gautam, Update, General, ETMX suspension - Side OSEM test osem_test_2016_07_25.png
                                                                      Reply  Tue Jul 26 18:07:57 2016, gautam, Update, General, ETMX suspension - Further OSEM Tests OSEM_spectra.pdf
                                                                         Reply  Thu Jul 28 03:22:28 2016, ericq, Update, General, ETMX magnets re-reglued 
                                                                            Reply  Thu Jul 28 13:49:44 2016, gautam, Update, General, ETMX magnets re-reglued ETMX_sideMagnet.JPGETMX_sideMagnet_zoomed.JPG
                                                                               Reply  Thu Jul 28 17:48:17 2016, gautam, Update, General, ETMY LR magnet broke off 
                                                                                  Reply  Thu Jul 28 22:43:03 2016, rana, Update, General, ETMY UL magnet broke off 
                                                                                  Reply  Wed Aug 3 10:52:03 2016, Steve, Update, General, ETMY soaking dish SD1.jpgSD2.jpgSD3.jpg
                                                                               Reply  Fri Jul 29 03:32:30 2016, ericq, Update, General, ETMX suspended once more 
                                                                                  Reply  Fri Jul 29 13:17:34 2016, Koji, Update, General, Oven 
                                              Reply  Thu Jul 14 01:00:33 2016, Koji, Update, General, ETMX ruby guided gluing ruby.jpg
                                  Reply  Thu Jul 28 16:43:01 2016, Lydia, Update, General, ETMX aluminium standoff groove condition wire_damage_4.jpgwire_damage_zoom.jpgno_wire.jpgcomparison_2.jpg
                            Reply  Fri Jul 8 21:22:38 2016, gautam, Update, General, Vent progress - ETMX SUS Coil driver electronics investigation 
             Reply  Wed Jul 6 09:34:26 2016, Steve, Update, General, PRM sensing voltage LR PRM_LR.png
             Reply  Wed Jul 6 19:36:45 2016, Koji, Update, General, SUS Vmon HPF.png160706_ITMX_VMON2.pdf160706_ITMX_VMON1.pdf
                Reply  Thu Jul 7 15:23:39 2016, ericq, Update, General, SUS Vmon coil_drive.png
                   Reply  Thu Jul 7 16:05:55 2016, Koji, Update, General, SUS Vmon 
       Reply  Thu Jul 7 17:12:50 2016, Johannes, Update, General, Vent progress IMG_2621.JPGIMG_2623.JPGIMG_2628.JPGIMG_2595.JPG
          Reply  Tue Jul 12 23:51:16 2016, Johannes, Update, General, Vent progress - ETMY inspection IMG_2679.JPGIMG_2673.JPG
             Reply  Wed Jul 13 00:38:25 2016, Johannes, Update, General, Vent progress - ETMY attempted repositioning 
                Reply  Tue Jul 19 13:21:42 2016, Johannes, Update, General, Vent progress - ETMY attempted repositioning 
       Reply  Sun Jul 10 17:33:00 2016, ericq, Update, General, Vent progress 
          Reply  Mon Jul 11 15:13:22 2016, gautam, Update, General, Vent progress: in-date First Contact procured image.jpeg
Message ID: 12328     Entry time: Sun Jul 24 03:43:56 2016     In reply to: 12327
Author: ericq 
Type: Update 
Category: General 
Subject: Magnet positioning 

When Koji and I were gluing magnets to ETMY, we decided to position the side magnet based on the empirically observed offsets from the standoff groove seen at other side magnet locations. Specifically, we figured that the magnet should be glued 1.25mm closer to the HR surface than the wire groove.

However, Steve has told me that he believed that this distance should be something like 0.5mm. 

I used the 1.25mm figure when gluing the ETMX side magnets, which now do not align well to their OSEM mounts. While it is certainly possible that I made an error when shimming the fixture, I think it is also possible that this figure was incorrect. 

Sadly, after poring through the DCC and various elogs, I have not been able to come up with a definitive answer on what this offset should actually be.

One approach is to examine the suspension tower dimensions. I.e. when subject only to gravity, the wire loop should lie in the plane of the back face of the top block of the suspension, as it is constrained by the clamps. Thus, the standoff grooves also lie in this plane. The center of the side OSEM mounting holes are about 1.64mm in front of this plane, which is larger than the 1.25mm figure that Koji and I came up with. Examining the picture Gautam posted of the marginal magnet/OSEM alignement, we see that this figure would in fact move the magnet in the wrong direction...

ELOGs in which the intitial side magnet gluing and fixture shimming are detailed do not reference the absolute position of the side magnet, nor do they include any pictures of their fixture setup. (Some links for the curious: 2652 2654 2668)

The DCC isn't much help either, as it is not clear what version of the gluing fixture we actually have. There is a drawing for a 40m specific version, but it includes swappable side-magnet-pickle-picker-slots to achieve different positions for different (circa 2001) optics; this is not the kind of fixture we currently have in our possesion. (https://dcc.ligo.org/D010131) I have discovered that some versions of this fixture (https://dcc.ligo.org/d990168) include an assumed 0.5deg wedge angle and thus position the two side slots differently. Although the fixture we have has no identifying marks on it whatsoever (naturally), I measured the two side slots to be different in axial position by roughly 0.6mm, which is consistent with a 0.5deg wedge. Furthermore, the sign of this difference indicates that this fixture ring is designed for the opposite wedge orientation than our ETMs, which have a 2.5deg wedge, making this fixture wrong by 3deg (which is ~4mm over the diameter of the optic). 

We did not account for this for either ETMX or ETMY, so this is another source of error, but this does not give us much guidance on what the real absolute magnet position should be.

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