New far forward beampipe and cryostat model v2025 implementation

[nat93]

Briefly, what does this PR introduce?

This PR introduces a complete model of the cryostat (fwd and bwd) with detailed description of superconducting coils, support tubes, yokes, yoke shielding, heat shielding, and cryostat vessel. The fwd and rear sides were adjusted in order to avoid overlaps with off-momentum detectors and low-Q^2 tagger pipes.

The corresponding STEP file can be found on SharePoint: EIC Public Sharing Docs → Documents → Experimental Program → ePIC → Engineering → STR-Files → IR6_CRYOSTAT_2200m_top_4-24-2025.stp [https://brookhavenlab.sharepoint.com/:u:/s/EICPublicSharingDocs/EdR44ODny1BEmMTTks61CCwBe8tJYMc0iWkPIYY_EjYEuw?e=2XLUEt]

The changes have been communicated to TIC, IR, and MDP communities.

What kind of change does this PR introduce?

• Bug fix (issue #__)
• New feature (issue #__)
• Documentation update
• Other: __

Please check if this PR fulfills the following:

• Tests for the changes have been added
• Documentation has been added / updated
• Changes have been communicated to collaborators

Does this PR introduce breaking changes? What changes might users need to make to their code?

Does this PR change default behavior?

Yes, it adds extra materials between the beam pipe (beam loss hot-spots) and the ePIC detector. It is crucial for the realistic detector background and dose calculations.

[wdconinc]

@nat93 Everyone's work is important in this collaboration. Acting dismissive of others' work will not be tolerated here.

[nat93]

@nat93 Everyone's work is important in this collaboration. Acting dismissive of others' work will not be tolerated here.

Hi @wdconinc , perhaps my message was not clear. The main idea is to optimize the procedure to avoid double work for everyone. I did not mean what you wrote. Opposite, I do respect other people work and it would be not efficient optimizing configuration that is already outdated, postponing the central detector protection and collider design - this is the message.

[nat93]

Hi @ajentsch,
Thanks for catching the missing units — you are absolutely right that all dimensions should be explicitly defined with units. I have also added a few other missing units (including OMDs) and corrected some typos in the older scripts, as we previously discussed ('apperture' -> 'aperture').

[ajentsch]

Yes, we should. Those were put in "by hand" to have vacuum surrounding the detector planes. Those numbers will need to updated now, too. Will try to do that tomorrow.

…

------------------------------------------------------------- Alex Jentsch Assistant Staff Scientist, EIC Directorate Brookhaven National Laboratory Upton, NY 11973 Bldg. 510, 2-197 Phone (office): 631-344-2139 Phone (cell): 281-726-0114 Pronouns: he/him/his

On Fri, Jul 4, 2025, 12:20 AM Andrii Natochii ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In src/forwardBeamPipeBrazil.cpp <#893 (comment)>: > @@ -517,10 +525,23 @@ static Ref_t create_detector(Detector& det, xml_h e, SensitiveDetector /* sens * SubtractionSolid final_vacuum_main_pipe( vacuum_main_pipe, cutout_for_OMD_station, - Position(0.0, 0.0, (2251.0 - beampipe_dimensions[pieceIdx].zCenter))); Hi @ajentsch <https://github.com/ajentsch> , should not we use units here as well? — Reply to this email directly, view it on GitHub <#893 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADABSF3MWPU3VGW5ZS6XHH33GX6JPAVCNFSM6AAAAAB7UPHSWCVHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMZDSOBVGQZDGMRSGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[johnlajoie]

Hey @nat93 @simonge @ajentsch @wdconinc - I'm trying to follow along with this an other PR's to see where we are in converging on an updated geometry that can be used in a consistent fashion for the "events with background" that we need to get going on the preTDR studies. @simonge - you had a bulleted list of seven things you wanted to see before this PR was merged. Is this feasible in a reasonable amount of time, and how much time is that?

I realize a lot of work is being done by a small number of people so please don't take any of this as a criticism, just trying to to make sure I understand where we are.

[ajentsch]

EICrecon PR with updated OMD matrices is ready: eic/EICrecon#1957

[nat93]

Dear @wdconinc, @simonge, and @johnlajoie,

Following the suggestions from Simon and Wouter, as well as our Zoom discussion, @ajentsch and I have refined the PR to meet the outlined criteria. - Many thanks to Alex for assistance.

The FWD beam pipe remains unchanged in this PR - there is no impact on the far-BWD detectors. On the FWD side, the beam pipe was adjusted to eliminate overlaps between the cryostat and the OMD chamber (Alex has updated the detector positions accordingly). The magnetic fields remain unchanged, and the detector acceptance is not reduced. In fact, on the FWD side, the acceptance may slightly increase due to the larger inner radius of the HSR cryostat compared to the beam stay-clear aperture.

This PR is a step forward, but additional improvements will follow: proper beam pipe definitions, a warm and split B2eR, and refinements to the magnetic fields and/or coil length (to be coordinated with the optics and magnet teams).

If everyone agrees, we propose to proceed with merging this PR.

[veprbl]

Trying to figure out what are the remaining blockers.
@simonge You were planning to look at the impact of this latest version?
We also need to check material map before/after merging this.

[simonge]

From what I see there is no impact compared to the current version at the moment as expected.

[simonge]

We also need to check material map before/after merging this.
There shouldn't be any change to the material map as I understand because everything is outside of the central detector region and outside the beampipe in the FF/FB regions.

There might be some changes I suggest down the line but happy to approve now and get the OMD update in EICrecon merged too.

[nat93]

Hi @simonge , should we expect or wait for any further checks? If not, can you please approve the PR so we can merge it? Thanks

[simonge]

Approved. I was hoping someone with more experience of the material map would confirm a new one wasn't needed.

[veprbl]

I will take care of the map.