Sphenix-calibration-l mailing list

["Hughes, Charles [PHYSA]" <chughes2 AT IASTATE.EDU>]

Hey Ross,

Thanks again for your thorough responses.

"If you fire one laser, I would expect to see a single hot spot in that laser's hough transform, and nothing nearly so hot in any other laser's.  Are you thinking the harmonics are multiple hot spots in one laser shot, wrt that laser, or that they are due to the other lasers somehow?"

I think what is going on is that the reconstruction code only loops through one track at a time BUT the hitmap it tries to associate with the track contains the G4 hits from ALL lasers. I wanted to provide some plots to back up this statement but right now I don't have that. In the next couple of days, I'll work through this to make sure my thinking is correct.

"Thanks for these.  The blind spot is a lot bigger than I had been picturing."

When I read this yesterday, I didn't think too much of it. Overnight, I had second thoughts and decided to rerun the 3 + 6 o'clock case with finer stepping in phi:

directLaser->SetPhiStepping( 50, 10*deg_to_rad, 350*deg_to_rad );

What I found is that your original intuition is correct - that blind spot for the 3 + 6 o'clock configuration is smaller:

this only required step sizes of 6.8 degrees which I assume we can achieve with the resolution we have. I updated my .pdf from the previous email and attached it to this one for you to take a look at (Laser Orientation Tests_rev1).

---

From: Ross Corliss <ross.corliss AT stonybrook.edu>
Sent: Tuesday, February 28, 2023 5:03 PM
To: Hughes, Charles [PHYSA] <chughes2 AT IASTATE.EDU>
Cc: sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov>; Valenzuela Cazares, Luis [PHYSA] <luisval AT iastate.edu>; Applegate, Noah J [PHYSA] <nja1 AT iastate.edu>
Subject: Re: [Sphenix-calibration-l] Ad-hoc distortions meeting today, 11am

 

Hi Charles,

Comments in line.

==========
Dr. Ross Corliss
Research Assistant Professor
Center for Frontiers in Nuclear Science
Stony Brook University
virtual office:  https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09

On Feb 28, 2023, at 4:37 PM, Hughes, Charles [PHYSA] <chughes2 AT IASTATE.EDU> wrote:

Hi Ross,

Thanks for the response. See below:

"- regarding the 90-degree harmonics:  You are still plotting all 4/8 lasers in the same plot, I assume? " 

Actually, no. This is only true for Slides 6,7 (all 8 lasers on the same plot). Slides 8 - 11 in the presentation in my previous email are for each individual laser. And still,, one has harmonics. I will triple check that I'm plotting what I think I'm plotting. Christof's suggestion was to limit the delphi range depending on which laser one is looking at.

If you have a chance, I'm in my zoom while I work here in the lab.  If you fire one laser, I would expect to see a single hot spot in that laser's hough transform, and nothing nearly so hot in any other laser's.  Are you thinking the harmonics are multiple hot spots in one laser shot, wrt that laser, or that they are due to the other lasers somehow?

"- Optimum angle looks like it's still good -- the doubled laser tracks are the ±fewº envelope, or?"

Yes, it is a 10-degree wide envelope (+/- 5 degrees) in either direction. Also, one thing Christof, brought up during the meeting about the optimum angle for frozen lasers: do we have to worry about creating a lot of space charge if the laser hits metal (i.e. the field cage)?  The nominal angle hits probably miss the field cage and hit the central membrane but when varying the laser with the +/- 5 degrees as you suggested some laser tracks do indeed hit the field cage.

I can re-analyze the optimum angle if we want to prioritize not hitting the field cage.

I don't think hitting the field cage is a concern -- it's no more metallic than the central membrane.  No matter what we hit, we are likely to produce a splash at the end of the track, but that is something we won't know until we have installed it.

- "Was there any conclusion/discussion of the 3+6 o'clock configuration?  it does indeed look like it has a bad blind spot in the opposite corner.  Would 6 and 12, or 3 and 9, be better than two adjacent sites?"

I just went back and checked the 6/12 and 3/9 o'clock cases and put them in a .pdf and attached this here in the email (Laser Orientation Test). Please take a look at these new slides.

Here is what I learned:

• When doing the 3/6 o'clock configuration your bind spots cover almost the entire sector of Sector 5 (NS) and Sector 14 (SS) (see slide 3 in the presentation attached to this email).

• 6/12 and 3/9 o'clock don't appear to me to suffer from blind spots (Slides 6 and 9 of the presentation attached to this email). I don't know if this makes them preferable because I'm not sure if the laser placement in these orientations affects the coverage of the TPOT.
  

Again, please take a look at the slides attached to this email(Laser Orientation Test).

Thanks for these.  The blind spot is a lot bigger than I had been picturing.  I think we are going to be able to install enough motors that it is not a concern, but this suggests that the priority goes:

{6S}, {6S,6N},{3S,9S,6N},{3S,9S,3N,9N},{3S,6S,9S,3N,9N}, ...  with 6 o'clock falling out of favor once we have multiple lasers, since we want to cover / double-cover the TPOT, and want to avoid a large deadspot.

-Ross

---

From: Ross Corliss <ross.corliss AT stonybrook.edu>
Sent: Tuesday, February 28, 2023 12:27 PM
To: Hughes, Charles [PHYSA] <chughes2 AT IASTATE.EDU>
Cc: sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov>; Valenzuela Cazares, Luis [PHYSA] <luisval AT iastate.edu>; Applegate, Noah J [PHYSA] <nja1 AT iastate.edu>
Subject: Re: [Sphenix-calibration-l] Ad-hoc distortions meeting today, 11am

 

Dear Charles, all,

Thank you for this update.  It looks like you've covered a LOT of ground and I'm sorry I couldn't be there in person to ask about it.

- regarding the 90-degree harmonics:  You are still plotting all 4/8 lasers in the same plot, I assume?  I'm fairly confident that the harmonics are an artifact of the different coordinate systems implicit in each laser.  There should be no harmonics for a plot that just has laser 1's perspective.

- Optimum angle looks like it's still good -- the doubled laser tracks are the ±fewº envelope, or?

- Was there any conclusion/discussion of the 3+6 o'clock configuration?  it does indeed look like it has a bad blind spot in the opposite corner.  Would 6 and 12, or 3 and 9, be better than two adjacent sites?

We can probably complete six lasers after all, in which case the blind spot is rotationally the same no matter which location we leave out.  In that case, it seems like 12 o'clock, which covers the TPOT least, is the sensible thing to leave out.  We may have to do some prioritization of which lasers are the most pristine, in which case I would lean toward the 3+6 sites as being the most important.

-Ross

==========
Dr. Ross Corliss
Research Assistant Professor
Center for Frontiers in Nuclear Science
Stony Brook University
virtual office:  https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09

On Feb 28, 2023, at 11:55 AM, Hughes, Charles [PHYSA] <chughes2 AT IASTATE.EDU> wrote:

Hello Everyone,

The Ad-hoc meeting just finished up.

I wanted to send around a copy of my slides for everyone to look at (they are also on the indico page).

Main updates:

1. Still working on determining relative pointing angle (slides 5-11) - Christof provided very helpful feedback this morning

2. Re-presented work on the optimum angle analysis from lte last week (slides 12 - 22). Also showed Luis' work on this (slides 19-20). Considered situation with lasers only @ 3 & 6 o'clock (see below).

3. Investigating clustering (slides 23-25). As Hugo suggested, it is in fact breaking.  Not sure why - discussed w/ Christof a bit:

<image.png>

<image.png>

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From: sPHENIX-calibration-l <sphenix-calibration-l-bounces AT lists.bnl.gov> on behalf of Ross Corliss via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov>
Sent: Tuesday, February 28, 2023 9:36 AM
To: sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov>
Subject: [Sphenix-calibration-l] Ad-hoc distortions meeting today, 11am

 

Dear All,

We are finishing the direct lasers these next two days, so Evgeny and I will probably not be able to call in, but I think it's useful for those who are not as immediately tied up to call in.  The meeting page and zoom link are the same as always:

https://stonybrook.zoom.us/j/94081538941?pwd=Y256N3ptUC9zV2M4cjNtUGgyWnJYdz09 
https://indico.bnl.gov/event/18427/

Short report from here:  We have assembled 4 working eggs, with two more nearly done.  Bench alignment still needs to be done, but it is looking much more promising than the minimal configuration we discussed a few weeks ago.

-Ross

==========
Dr. Ross Corliss
Research Assistant Professor
Center for Frontiers in Nuclear Science
Stony Brook University
virtual office:  https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09

<20230228_TPC_Distortions_Meeting_Charles.pdf>

<Laser Orientation Tests.pdf>

Attachment: Laser Orientation Tests_rev1.pdf
Description: Laser Orientation Tests_rev1.pdf