Sphenix-tpc-l mailing list

[Dan Cacace <dannycacace AT gmail.com>]

Bob,

Agreed, just buying *the* mirror is a major advantage. As for the sensitivity of the position of the focal point, as you may imagine, it is largely dependent on the parameters of the beam (diameter, half angle, etc.) when it hits the ellipsoidal mirror. For example a beam with a half angle of 0.25 deg, diameter of about 0.15 mm and a +/-1 mm move of the focal point corresponds to the beam diameter changing 0.15 mm to 2 mm, 2ft away. I would say it is quite sensitive, but the same company that makes the rotational mirrors, also makes linear motors with a resolution of <0.05 µm. Or maybe we can buy a pre-made solution, like this: https://www.youtube.com/watch?v=X9AXI8czA7s.

-Dan

On Fri, May 1, 2020 at 5:52 PM Bob Azmoun <azmoun AT bnl.gov> wrote:

Hi Dan,

Aha!, thanks for checking this. This is one less thing to have to worry about regarding this beam steering option. I have to say, of all the very interesting (and pretty clever) options you showed us today, I think I like this one the most. Like you said, if we can just buy *the* mirror and only have to deal with the beam shaping (ie, the variable focal length shaping), I think this would be a big win. Not to mention, we get a continuum of angles in a *focused* beam steering configuration, the way Tom likes it :). One immediate issue I see is that the focusing of the beam in the center of the TPC may be a bit more challenging since we'd have to tune how much we favor the focusing element over the de-focusing one. In this sense, it would  be good to investigate this configuration some more in TracePro before the next meeting (also to see how sensitive the position of the focal point is on the beam divergence, etc), where we should probably try to narrow down the beam steering choices.

Cheers,

Bob

On Fri, May 1, 2020 at 4:16 PM Dan Cacace <dannycacace AT gmail.com> wrote:

Hi Bob,

One the last things I brought up and we discussed during today's meeting was using a true ellipsoidal mirror and adding a motor to adjust a focal lens and thus the focal point. One concern you had was if the focusing effect of the ellipsoidal mirror would be the same in both axes, so I quickly through it in TracePro assuming everything was "perfect". Looks like the focusing effect is the same, see attached.

-Dan

On Thu, Apr 30, 2020 at 7:43 PM Bob Azmoun <azmoun AT bnl.gov> wrote:

Dear All,

Given the need to hone in on a final design for the beam steering mechanism for the straight line laser source, it was decided to meet again this week, which is a departure from our normal bi-weekly schedule. We will have the meeting tomorrow at 9am. 

A link to the Indico page is here: https://indico.bnl.gov/event/8430/

and the bluejeans link is here: https://bluejeans.com/881710315

I put together a tentative agenda, but please feel free to modify it and upload any material you wish to present. 

Talk to you tomorrow!

Cheers,

Bob

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B. Azmoun
Brookhaven National Laboratory
Physics Dept. Bldg. 510 C
Upton, NY 11973
P: (631) 344-4082
F: (631) 344-3253
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-----------------------------------------------
B. Azmoun
Brookhaven National Laboratory
Physics Dept. Bldg. 510 C
Upton, NY 11973
P: (631) 344-4082
F: (631) 344-3253
-----------------------------------------------