DUNE: ND-LAr Preliminary Design Review

America/Chicago
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Dan Dwyer (LBNL), Daniel Dwyer (AD/OPs), Michele Weber (University of Bern / LHEP)
Description

ND-LAr, a ~100 ton LArTPC system, is a core element of the DUNE Near Detector (ND). The primary aim of its design is a neutrino detector that is functionally identical to the DUNE Far Detector (FD) LArTPCs with comparable performance in the high neutrino interaction rate environment of the DUNE ND hall. ND-LAr has a modular design consisting of a 7x5 array of 1x1x3 m3 units which provide independent dual charge drift regions with a pixelated charge detection scheme that also serve as isolated optical detection regions with tiled photon detection systems. A dedicated downstream muon spectrometer (TMS) supports ND-LAr in reconstructing muons which exit ND-LAr downstream. 

The ND-LAr Consortium is responsible for the design, prototyping, production, and assembly of the detector system, while other organizations are responsible for the cryostat in which ND-LAr is deployed, the cryogenics required for its operation, the DUNE-PRISM system which moves the detectors transverse to the beam axis, and TMS. ND-LAr must also integrate with ND-wide systems such as data acquisition and slow control, as well as the overall installation and integration effort.

The review will assess the preliminary design of ND-LAr in achieving its goals and its readiness to proceed to the final design phase. It should also assess the plans and activities of the consortium in relation to risk mitigation, prototyping, production, QA/QC, and integration and installation. While the cryostat, DUNE-PRISM, TMS, data acquisition, and slow control are outside the scope of the consortium, interfaces should be suitably defined.

A conceptual design review of DUNE ND which included ND-LAr was conducted in July 2020. The ND-LAr consortium also held a PDR readiness review in May 2021.

Review Information
Review Home
Review Documentation
Charge Letter

Final Report

 

Zoom Information: Please see email or contact organizers: Bob Svoboda, Tim Bolton, Mary Bishai

Support

Notes/Minutes Monday June 27

 

Schedule:

2018-2024 Design

2025-2028 Production

>2028 Installation

 

Requirements are total systematics <3% as compared to current T2K and NOVA at 7%-8%

 

This requires a size large enough to contain events (except muons) and a DAQ that can handle pile up. This requires a segmented rather than monolithic detector.

 

Q&A:

JD: How deep in the liquid do the modules sit? Why a shallow depth? Will cameras be used to monitor? Ans: Design is for 10cm-20cm, and with only 25 kV needed this is enough to prevent bubbles and discharge. Do not plan to use cameras at this time.

 

BW: Will you show simulation results for 7m depth? Since the PDS is “off project” how will you manage it? Ans: Key partners have a record of successful delivery of 2x2 components, plus FSD will be on project. This is a bigger worry, since US contributions are capped.

 

BW: Part of the project assumes contributions from JINR in Russia. What’s happening with this? Ans: Still assuming JINR will deliver, but this is still under discussion.

 

 

Reiterating that with expected 55 interactions/spill at 1.2MW, a monolithic detector is not possible.

 

Q&A

BW: SBN expects ~8M events and ICARUS expects >100k nue events from NuMI. What is your plan to use these data? Ans: We assume these data will be used to update generators, and we will use those generators.

 

BS: You assume the beam has azimuthal symmetry, but in reality, the beam shape will not be perfectly symmetrical, the target will not be perfectly aligned, and the horn fields will not be perfectly symmetrical. What studies have been done to show that these factors are negligible, allowing you to have a detector smaller in one dimension? Ans: Such studies have been done, and we can make the documents available.

 

BW: The assumption of symmetry will especially be relevant when PRISM moves the detector off-axis. Have you also studied this? Ans: Yes, and will make documents available.

 

HN: What would you do if you need to de-scope? Have you thought about this? E.g. 6m instead of 7m. Ans: The costs do not change much with small changes to the current size, as cryogenics and other infrastructure are the same.

 

 

Two PDS systems (Arclight and LCM). JINR and Bern responsible, and they share information. They also share the same readout system.

 

Made tests to look for bubbles with prototypes, even a “no flow” test.

 

Ran slosh test simulation with PRISM acceleration at 1.25 cm2/s – about 5x nominal. FESHM has also performed hazard analysis.

 

Q&A

EB: Is the G10 board really 3 meters long, or is it in sections? Are they flat enough to meet specs? Have you identified a vendor that can make a 3m board to required flatness? Ans: Yes, they are 3m and we have identified a vendor that can do this at the limit of their capabilities. Have not purchased such a board yet.

 

BY: On slide 28 how do you know a rate increase is expected for boiling? What is the mechanism for that? Ans: Did a test where boiling was allowed to happen and a rate increase was observed. DD: speculate that this is due to change in capacitive environment which looks like a charge injection. Have observed this to happen with about 1 Hz frequency for boards with improperly bonded chips

 

Grounding specification is 10 ohms impedance at 1 MHz. Grounding scheme shown, which is built around tinned copper bus bars. Will be installing dielectric breaks in plumbing and in mounting. Another specification is for an accidental HV discharge to not fry electronics. No shared return paths between subsystems.

 

Q&A

CM: Do you have only one ground for the cryostat? Would the system have the intrinsic capacitance to damage components for a sudden drop of HV? Ans: Still working on this, plus also working on ASIC hardening.

 

BS: KLOE magnet is nearby, what is the field strength you expect? Have you estimated the induced current in your system if the magnet experiences a sudden turn-off? It could be substantial given the loop areas involved. Ans: We have not looked at this, but think the fields will be small.

 

 

The 30x30 prototype achieved TRL5, and the 2x2 achieved TRL6. 2x2 lesson learned can be seen in EDMS2737729. Deployment in NuMI test beam should reach TRL7.

 

Full Size Demo (FSD) at SLAC will be final design prototype needed.

 

Q&A:

CM: How does the purified Lar flow through the module? Will the gas stratification be disrupted? Ans: Flow is through top holes and out bottom holes.  Experience has shown that the purification system can handle this despite any issue with ullage gas.

 

BW: What is the expected 2x2 interaction rate at NuMI? Ans: 0.3 interactions/m3/spill, but this may be small compared to beam related backgrounds.

 

BS: Is positive ion feedback an issue, despite the fact you are underground? Ans: UG location and short drift distance makes this not a problem.

 

BW: What is the distribution of PDS units in the prototypes compared to FSD? Ans: essentially identical.

 

HN: Is the design info from Bern being transferred to US (since US has major contribution to production). Ans: FNAL people visit Bern and Bern people visit FNAL for this process.

 

 

Expected flow though module is 125 g/s.

 

QA/QC done at Bern before shipping to FNAL either by DUNE collaborators or contracted vendors.

 

Needed for FDR:

  • ICD to FDR level
  • Statics and heat transfer calculations finalized
  • Completion of FSD

 

FDR scheduled for Q4 CY2023

 

Showed results of FEA studies of stiffness and how it meets specs, along with details of mounting.

 

Q&A:

CM: The cryostat is different for the actual LArTPC and demos. This will lead to different flows. How wil you handle this? Ans: Expectation is that the actual cryostat will be better than the prototype ones.

 

EB: In slide #12 are the screws adjusted under load? This could lead to issues with seizing and/or galling. Ans: screws just prevent assembly from going up, not under lifting load.

 

BY: The 125 g/s seems like a very low flow. How does that compare to thermally driven currents? Ans: need more study on this.

Notes/Minutes Tuesday June 28

Notes/Minutes Wednesday June 29

 

Alice [missed Q&A]:

 

 

Jamie [missed Q&A]:

 

Harry: Is your assembly facility - what is the breakout between the technically permenant people at FNAL and the temporary university people who come and go?

Answer: There are full time people at FNAL ATF that are supporting the effort

 

Harry: The full scale demonstrator where does the effort take place - SLAC or FNAL or BERN? 3 assembly sites?

Answer: It is only BERN and Fermilab

 

Alice: I am wondering about the alignment of the pixels after all the assembly is done? Is there a final survey after assembly? How do you insure the flatness of the tile assembly?

Answer: There will be a survey after assembly - they are all planned to be shimmed - so we are hoping that the procedures with shimming and assembly will keep them flat. In practice the 2x2 went well and the procedure involves a continuous measurement as we go along with the assembly.

 

Duane: We need to keep in touch on the anti-motion - we need to understand when we put material in motion how that impacts the assembly

Answer: We are doing the FEA analysis to try and understand this better and how to plan it with stepper motors..etc

 

Harry: Do you go over to BERN very much and interact with the team there? Is there a tight connection between the two institutions?

Answer: COVID has prevented that but going forward I will be at CERN for FD work and will also work with BERN. We are using the same fixtures.

 

Louise

 

Alice: A general question on the cold N gas vs Lar testing - has that been reviewed, what is the decision process on the testing?

Answer: We did have a review, we had a task force created that reviewed the testing procedures and QA/QC and the tests at LArTF and we are mitigating risks by testing everything in the cold that we can in LArTF. If there is a need of course correction - there are capabilities at MATF for more tests. While the initial desire was to run everything in Lar we looked into this and the experience from the FD with testing some detector elements in cold N gas was good enough. To better use limited resources we looked into this carefully and came up with the current plan.

 

Harry: Once you turn it on cold and no breakdown or unusual current draws - it is usually fine -is this still true? What is the plan if you do find a problem? Do you have capabilities at the facility to do rework on a module?

Answer: We do have some space planned for a module to be sitting there to get some work done.

 

Harry: How many spares?

Answer: We plan to  have one row of spares - if it works out financially. The original idea was that each module can be totally replacable and taken out of the detector but we couldn’t make the cryogenics work, so we have the rows of interconnected modules.

 

 

Bob: The schedule you have driven by the funding flow - is that co-ordinated with the entire near detector elements?

Answer: Yes, we are a WBS element in the full ND project.

 

Bob: You bought up the issue of stopping and restarting - how do you keep the team together including the engineers? And reassemble the team at the necessary time.

Answer: We do realize it may not be possible to bring the same engineers back on board after they transitioned to other projects.

 

Bob: Do you have technically limited aspects or is everything driven by the budget profile?

Answer: We really have to keep many elements going to be able to assemble in the FSB - I&I is not on a technically limited schedule we can delay a bit.

 

Bo: Slide 25 - you show you have to store the modules for over 2 years - what is the plan to keep the module in particular the PDS in a controlled environment?

Answer: We do understand this issue and we have added this as a requirement in the I&I requirements for having a environmentally controlled storage but we need more engineering help to really dig into this and see what is required. This is probably a risk we need to consider.

 

Bo: For FD we have a parts breakdown structure - do you have somehting like this for ND?

Answer: Not fully yet, we have had some initial  disucssions with the FD to understand the numbering scheme. We are using a parts numbering scheme for the readout system since we are tracking different components already but this hasn’t really been fully developed for the full LArND

 

Bo: Is there any simple quick diagnostic you do after 1 row of modules is installed to check that everything is okay (slide 45)?

Answer: We are thinking about this, but we need to address safety concerns since we have a big pit open on the side of the installed row to access the top of the detector for tests.

 

Bo: There is no manhole on the cryostat so you cant actually get in? How do you do the survey if there is no room for people to get in.

Answer: Yes there is no manhole, and there is really no room in this TPC to get someone in. We do survey (slide 40) from the top of the row.

 

Bo: IS the roof deformation well understood?

Answer: It is well understood through FEA but we need to tie to near site and fiducials within the facility itself

 

Claudio: What is the current level of the understanding of the interference between this detector and the other ones? Both overlap space above ground and underground and also activities - like say welding

Answer: We do envision having a surface team working at the same time as a cavern team. In terms interference with other detectors most of it is with TMS and we need to interface with overall I&I management

Fabrice (overall ND I&I management): SAND is the last detector to install, TMS And cryostat ND Lar will be done in parallel with some very clear assumptions. At any given point, major activities will be done only on one ND system at a time so TMS only then switch to an activity on the cryostat then switch…etc. So we have a good understanding of the parallel activity and are consulting with the Fermilab riggers on this.

 

Harry: As the team re-assembles for installation - will LBNL manage all this from LBNL even though it is at Fermilab?

Answer: We don’t have a clear answer for this right now. The technicians are all Fermilab technicians and we welcome even more help from FNAL.

 

1:00 PM  1:15 PM
Break 15m

1:15 PM  2:15 PM
Path to FDR: Design, Prototyping, and Technology Maturation1h
Speaker: Michele Weber (Bern)
Weber_DesignDevelopmentAndPrototyping_NDLArPDR_v1_06222022.pdf

2:15 PM  2:30 PM

 

Bob: What is the status of the TDR/CDR and technical writeup?

Answer: We contribute a chapter in the current DUNE TDR

 

Harry: Can we get the Q&A from the 2x2 prototyping breakout discussion this morning?

 

Claudio: We had a discussion about testing the Lar flow in the 2x2 and there was a discussion about the heating that could be added to model the membrane cryostat.

 

Harry: Do you have time to go with the resistive cathode option for the cathode?

Answer: We have to keep the resistive option open as long as we can as a risk mitigation. We are preparing to do a test in the BERN setup and we will push it as much as we can. We have months of time to do some more tests before a decision is needs.

 

James: The initial plan was to receive the DR8 by early next summer so hopefully in time for the prototype construction.

 

Bob: What would be the impact if there is no funding for the SLAC facility?

Answer: We would still have the Bern one, but it would prevent us from building the expertise at SLAC who can then support the effort at FNAL. It is too big for Bern alone to run with students.

 

Bob: For the PDS  - having an inhomogenous system - what would be the impact if the funding for one or the other of the systems was not available?

Answer: We have thought about this, on the light collection it is easier to switch one to the other. We have built Arclights and LCMs at Bern and can have Dubna travel to Bern, The issue is the readout. The US DOE will not fill any shortcomings so this will have to be on the international partners to backfill. Switzerland is going through the equivilant of CD2/3 and commit the funding for this system in November but the US is still at CD1 and really the big risk is commitment from the US.

 

Conclusion15m
Speakers: Dan Dwyer (LBNL), Michele Weber (Bern)
Weber_Conclusions_NDLArPDR_Jun2022.pptx.pdf

2:30 PM  3:00 PM

 

  • Committee Executive Session

 

 

 

 

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