 |
 |
By the way, I am thinking more and more that the bottom is a little more open than the nominal position. If you will all recall, in order to get top/bottom wires to agree on beam position, we assumed a pretty drastic vacuum sag for the bottom motor. However, making them agree was a condition that cannot be guaranteed, as built. At face value, your slide 9 might indicate that the bottom was open w.r.t. nominal by about 125-150 microns at layer 1. This would also have a real impact on bottom tracking efficiencies. Sho… did you produce results of the surveyed positions of the wires? I know you checked that they were repeatable, but I don’t recall whether you actually took measurements that allow us to correct their as-built positions. Frankly… this is a long overdue question on my part, but things were confusing enough back when we were trying to sort this out… Tim > On Jul 24, 2015, at 10:43 AM, Nelson, Timothy Knight <[log in to unmask]> wrote: > > Hi Norman, > > OK, let me see if I understand. On slide 11 you are projecting back to the known z position of the wire and asking what the y intercept is there. You find a 3mm discrepancy between the two sides. So, how does that indicate non-coplanarity of sensors? It seems more likely that the sensors are in the same plane but slot/hole are shifted laterally (in-plane) relative to one another. I think we know what have <50 micron shifts like this from survey, but that’s about the most it can be. This could also be caused by relative rotation of L1 and L2 around the beam axis. A 2-d plot of this as a function of position in L1 (or L2) would be illuminating: whether there is a step in crossing from the hole to the slot side or whether there is a trend as the hits in L1 and L2 move along the sensor from one end of the module to the other. > > Looks like there will be a lot to learn from this data, which is good news! > > Tim > >> On Jul 24, 2015, at 10:30 AM, Graf, Norman A. <[log in to unmask]> wrote: >> >> Hi Tim, >> Thanks for your comments. I was looking for you to discuss the physical geometry >> to see what constraints there are on the slot/hole module coplanarity. Although the >> slot module statistics are low the differences looked statistically significant. And those >> comparisons had layers 1-2-3 in common. The projections back to the wire are roughly >> 2.5 meters, so it wouldn't take much. >> Your comments about the opening angle are spot-on. On my list for today is to fit >> modules 1-2-3 and project into the four quadrants of layers 4-5-6. >> Norman >> >> -----Original Message----- >> From: Nelson, Timothy Knight >> Sent: Friday, July 24, 2015 10:10 AM >> To: Graf, Norman A. >> Cc: Nathan Baltzell; [log in to unmask]; hps-software >> Subject: Re: [Hps-analysis] July 24 DAWG Meeting >> >> Interesting, Norman. I'm not sure I understand the non-coplanarity comment on the last slide. Hole/slot sensors can't be in different planes by very much, a couple hundred microns at most dominated by non-flatness of the half modules. Also, anything that find shifts that are bigger than about 100 microns in x-y (I see >mm lots of places) or a few hundred microns in z from the geometry needs to be looked at very carefully, since that flies in the face of all other data, even if you are using the v1 detector. Shifts even that large in v2 would indicate problems in the survey measurements or mistakes in implementing them in the v2 detector (neither is completely impossible). >> >> What's being done for multiple scattering errors here? If you want to get meaningful results (e.g. unbiased residuals with a layer left out) you really need to run GBL or change the way multiple scattering is dealt with in seedtracker. Otherwise, relative misalignments in layers 1-2, which are close together (by ~an order of magnitude relative to the full SVT length) and are assigned small errors in seedtracker, will dominate the track parameters and bias what you see everywhere else. Obviously, the former (using GBL) is much more desirable. >> >> Finally, once GBL is working, probably the first thing that needs to be done (both here and with field on data) is use the data to figure out the actual opening angle of the detector, since uncertainty in that is now expected to be the dominant alignment uncertainty by far. Without having that right, trying to point to the wire is fraught with difficulties and you can really only look at internal consistency. >> >> Cheers, >> Tim >> >>> On Jul 24, 2015, at 9:05 AM, Graf, Norman A. <[log in to unmask]> wrote: >>> >>> Hello All, >>> Apologies for the SNAFU this morning. I've posted my slides to the meeting page on confluence. >>> Bottom line is that the data seems to be of sufficient quality and >>> quantity that we should be able to derive some alignment parameters >>> for the SVT independently of the field-on data. I'll give an update next week. But in the meantime, please let me know if you have any questions or comments. >>> Enjoy the weekend, >>> Norman >>> ###################################################################### >>> ## >>> Use REPLY-ALL to reply to list >>> >>> To unsubscribe from the HPS-SOFTWARE list, click the following link: >>> https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1 >> > > > ######################################################################## > Use REPLY-ALL to reply to list > > To unsubscribe from the HPS-SOFTWARE list, click the following link: > https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1 ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the HPS-SOFTWARE list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1