Closeout LAr20 R&D plan review

Closeout LAr20 R&D plan review Review at Fermilab, November 23, 2009. Committee: R.Kephart, T.Peterson, A.Rubbia, R.Svoboda, H.Weerts General findings Thank you for an impressive set of presentations on the LAr R&D program. Compared to the previous year this is a very comprehensive program of LAr TPC R&D, addressing many issues of LAr operation and possible operation at an underground location Overall Comments/Observations: LAr TPC is a difficult technology (compare to several years of R&D in Europe). Can a proper design of LAr20 (e.g. cryostat, electronics, underground eng., etc…) be developed and R&D performed on the timescale of LBNE (CD-1, …) ? Leads to question: Will FNAL pursue this R&D program independent of the LBNE timescale ? The committee recommends a “strong yes”.

Underground issues/Scalability Underground/ Scalability ARUP is selected for feasibility study. Problems that have never been solved before, need addressing Develop a sense of the scale of problems with independent ( lab based ?) team Bullet #1 from 2008 review: not convinced gold star deserved : Bullets from 2008 review were presented with ratings: Finding: Progress on all “gold star” bullets is being made, but not at the “gold star” level. Recommendation: A feasibility study addressing excavation the appropriate cavern, construction, operation and eventually decommissioning LAr20 at DUSEL must be performed. The study should involve Homestake’s mine expertise to develop the relevant rock engineering design (e.g. long term integrity, potential effect of water freeze, etc.). The study should focus on potential show-stoppers at DUSEL. Compare with the 2 year-long European study (LAGUNA) which considers 7 different sites for their large LAr detector to mitigate local risks.

Main Ingredients of the LAr R&D plan, I High quality work. Advanced technology. Question: how long will this work be useful i.e what are the plans for operation long term? Can contamination results be expressed in rate per area per hour? MTS(Luke): Useful effort, very high quality. Plans are good. Pursue with highest priority. What will/can be done beyond Phase I? Address scalability problems Phase 2 and 3 need to answer the question of viability of this technique. Consider carefully inventory of materials based on likely problem ones. It may be the case that virtual leaks are more important than materials and residual water or O2. How to handle this? What max size TPC could be inserted in the tank ? Could the instrumented tank be placed in a test-beam? . LAPD: Exploit ArgoNeut data for better understanding of detector: high priority to develop reconstruction algorithms and get first results Recommend hand-scan of events in parallel to developments of sophisticated automated software. Is its size sufficient for testbeam exposure ? ArgoNeut:

Main Ingredients of the LAr R&D plan, II Complete experiment: from R&D to physics. Questions on triggering for Supernova & proton decay signatures. The plan to address this in MicroBoone is not well developed. What are the options and goals ? What is importance of MicroBoone in relation to LAr20 project ( especially given timeline)? Does MicroBoone divert manpower from focused LAr20 R&D ? MicroBoone: Presentation clearly showed better performance for cold electronics. Does one need this extreme level of cold multiplexing ? What is the effect on the physics if it were warm? If cold electronics do not work is it a showstopper ? Electronics R&D: Note: the committee was not unanimous on the issue of cold electronics. Some thought that given the noise performance and reduction in cable plant/feedthroughs it should be pursued as the only solution. The questions above reflect concerns about cold electronics expressed by some.

LAr results needed Strong Encouragement to use test-beam for particle ID, energy resolution, etc. Compare those data to Monte Carlo and establish accurate simulation, reflecting realistic measured detector performance. This is necessary input to estimate sensitivity for signal events and rejection of background. For example: 16% resolution for EM showers was quoted, whereas one expects 3%/sqrt(E) for fully contained showers( Quote from A.Rubbia). Exploit ArgoNeut data for better understanding of detector: high priority to develop reconstruction algorithms and get first results ( see previous comments). Lack of results will lead to uncertainty on detector performance for DUSEL. Measure pi-zero mass in ArgoNeut, to establish an in-situ calibration. Only 100 events were scanned to measure the coherent pi-zero production rejection as background for ne events. MC statistics should be increased (Fleming, slide 9). There was some confusion on how the reduction from 6.5%(Slide 6) to 0.2%(Slide 7) acceptance for pi-zero events was obtained ( Fleming slide 6,7). Note: Manpower is currently not adequate to address all these items. Can synergies with other FNAL neutrino experiments be exploited? For future developments, as part of LBNE, the science collaboration needs to be fully engaged in charting the course of LAR20 and its R&D. This is critical to engage outside collaborators and get support from outside FNAL.

Comments Emphasis is on Membrane design. Test done in Korea; are there are other tests that can be done ? Investigate Modular design independently, maybe find company? Modular design has the advantage of being relatively well-understood. Issues “Outer vessel” (the rock cavern) presents new mechanical and thermal issues. Rock is affected by being slowly cooled. Cavern cooling provides slow change in structure. Cooling of surrounding rock will change dimensions and stresses in uncooled rock overhead. Inner vessel is non-standard. Changes from LNG tank designs for lower heat load and heavier liquid will affect the support of the inner vessel membrane. Although there is experience with membrane vessels for LNG on ships and on land, the deep cavern LAr vessel presents significant new design issues. Recommendation Develop both designs in parallel Cryostats

Comments Working through a 4850 ft elevation change is a unique and challenging issue for a cryogenic system. The cryogenic documents provided from BNL illustrate a very good conceptual design and initial review of system issues. It is unlikely that any industrial supplier has experience with a cryogenic system operating over such an elevation difference. Close interaction with the cryogenics and vessel conceptual/cost contract participants will be required to assure issues are addressed. Detector vessel temperature control will likely require special cryogenic system features. Issues From Integrated Plan, cryogenics section, “The liquid in the detector cryostat must have a small temperature variation (±0.2K) over its volume and the velocity of any currents in the liquid must also be small (< 0.1 m/s).” Such uniformity in a very large volume combined with low flow rates seems very difficult. Recommendation Probably useful data already exist regarding typical temperature variations from other large LAr detectors. Consider ways to incorporate temperature control studies and development in the R&D effort. Scale-up of all aspects of the cryogenic system from the small test systems, including components such as clean valves and clean pumps, should be considered during testing phases so that equipment representative of that in a large scale system may be tested and/or costed. Cryogenics

Comments A low detector vessel maximum pressure (5 psig was mentioned, but the precise number is not the issue) does not permit passive venting of argon vapor to the surface from the deep location. Issues A column of saturated vapor from the 4850 ft level to the surface results in a pressure of (very approximately) 12 psig. Thus, passive venting to the surface requires 12 psig plus a little pressure loss for the piping. A maximum allowable pressure of less than 12 psig means that with loss of LN2 cooling and without active pumping, the detector vessel cannot push argon to the surface. The detector must vent into the mine. ODH risks could be reduced by hardening the system such that it “fails safe” with venting to the surface. Of course, with such a large diameter vessel, every psi adds a large load to be carried by the vessel. In case of a membrane design, this is mainly the vessel cover. Recommendation Consider a vessel design which allows passive venting to the surface. Vessel safety and ODH

Risk findings Risk matrix. Not all risks have been identified in Table. Develop more fully Does R&D program addresses them all? Examples are on next three slides General observations: • Very important to address risks during all phases of the project: • Risks associated to construction • Risks associated to filling (LAr procurement, …) • Risks associated to operation • Risks implied by any needed access to the experiment e.g. massive electronic failure due to drift HV sparking • Plans for decommissioning (where to put argon ?)

Example of risks to include in table, I Safety analysis: There are cost risks associated with safety. E.g. What if active venting is not approved  pressure vessel must withstand > 15 psi during venting to surface. What entity determines the rules must you follow, approval of exceptions, risk that the rules change during the project ? Risk that hydrostatic pressure from water column connected to space between membrane liner and rock wall causes large deformation or rupture of vessel Risk that cool-down of rock walls and floor with time ( but not ceiling) of underground enclosure causes fractures of supporting rock Risk that small events like rock bolt failure or other mechanisms ruptures side or top of tank Risk large rocks from ceiling that fall onto detector and rupture vessel ( e.g. 50 T of debris) What is the plan to insure people are safe and that you can rid yourself of the Argon and reenter the mine at some point ? Risk of collapse on a side wall due to similar mechanisms… what mechanical requirements are there on the liner ? Risk that single point failure in electronics… e.g. mux design, fiber drivers, etc result in large number of channels dead  warm up/ cool down cycle… expensive without LAr storage Risk that companies will not buy back the LAr if you have to warm up

Example of risks to include in table, II If future development is to be on the LBNE project, then there must be focus on risks associated with operation at DUSEL. E.g. taking 600-700 tank trucks through town for a 20 kton fill. How long will this take? How many trucks available and what Is the cost? Is ARUP’s conception of what is a “leak” compatible with yours? How will state agencies and local groups be brought into the planning? Is the local community aware of the plan to store large amounts of LAr in town? How about senator, representative, governor, etc? What are state and local laws? DUSEL is not a DOE lab. Public reaction may also be a risk. Will R&D determine the required recirculation rate? If the detector had to be recirculated at the same rate planned for microBooNE (1/day) then the system would have to be larger than the SK water plant by factor of ~15. What is the maximum practical circulation rate taking into consideration costs, available pumps, filters, and other needed components in addition to currents allowed in the detector? Will R&D address this to the extent needed for CD-1? How will LAr be removed during decommissioning? There needs to be a decommissioning plan. Can one safety vent 20000 tons from the bottom of the mine? Must trucks be called in to remove? How much will this cost? Even though risk may be small, there should be a plan for a catastrophic leak of the cryostat. Surely such a plan exists for LNG carriers and the GEOSTOCK facility. State and local authorities must be informed as to what is being planned when there has been adequate thought given to such mitigation – certainly before CD-1.

Example of risks to include in table, III Risk: Perform failure modes and effects analysis of pump and dewar systems. Mitigation of all failures may be expensive due to large potential head pressures and need to vent to surface Risk: Some components may not scale easily in size ( pumps, purifiers, etc) resulting in large unexpected development costs Risk: Cascade failures… one TPC wire fails… leading to many broken wires …….. …….. Then an R&D plan that addresses these risks

The Committee is requested to review the current R&D status and the plan, and comment on progress and on the plan’s credibility and utility. Has the work done at Fermilab and by collaborating institutions so far advanced LAr/TPC technology in the US and more broadly? Yes. R&D has demonstrated methods for obtaining and verifying good liquid argon purity on a small scale. (See slides 1-4.) Is the plan sufficiently detailed to allow the needed human and financial resources to be allocated? No, not sufficient detail in plan to understand all resource requirements. However it is clear that more resources are needed to begin addressing all the R&D and programs mentioned. See slide 5 ( “LAr results needed”) Does the plan build on current capabilities effectively? Yes, but also we suggest increasing emphasis in R&D on implications of size scale-up. Are there significant issues not being addressed in the current plan? Yes. See slides 10-12. Conclusion -- responses to the charge to the committee

Closeout LAr20 R&D plan review