Interim report from PMT task force

1. Interim report from PMT task force S. B. Kim for PMT task force Jan. 24, 2019

2. PMT Task Force S. Peeters, J. Spitz, F. Suekane, T. Maruyama and S.B. Kim (chair) Motivation and mission: Delay of DC Japanese PMT availability requires our strategy to minimize any delay for our data taking. 1stmeeting: 23:00-00:30 on Dec. 28, 2018 2nd meeting: 22:00-23:00 on Jan. 7, 2019 3rd meeting: 22:00-23:00 on Jan. 17, 2019

3. Status of DC PMT delay • According to our previous schedule, DC disassembly should have begun in Sep. or Oct. in 2018 and some of retrieved DC PMTs should have been delivered to J-PARC around Dec. 2018 or Jan. 2019. • An DC onsite supervisor has not been found and appointed yet. • A French fluent engineer can be employed by Saclay (or CEA) for a year. • The DC disassembly cannot take place without the supervisor. • A DC supervisor would be available at the end of this March or in early April in an optimistic case. Then it would take 6 or 8 (~7.5) months to install the PMTs because of LS extraction (~2.0), PMT removal(~2.0), packing/shipping(~1.5), and installation(2.0). Even in this case we expect data-taking in Nov. 2019.

4. Our efforts to push DC detector disassembly • Taka and Soo-Bong discussed on this issue and agreed to form a task force to tackle the problem around Dec 20, 2018. • Taka wrote a letter to the DC spokesperson on 22 Dec. in 2018, expressing our concern. • Anatael responded on 3 Jan. 2019: excuse for the delay and description of the detector dismantling status. ……. Let me to provide some information. The main issue is that we are lacking dedicated personnel for the dismantling operation, leading to major discomfort and very slow progress despite all best intentioned effort. For example, in 2018, all dismantling operations, including some very heavy mechanical actions by CNRS, proceeded within schedule within 2018 (all done within OCT) till we hit the critical "opening of the detector". There, there are 2 main issues: a) nuclear safety authority permissions and b) further technical support. Both require dedicate and even specialised personnel — not trivial. We have been doing what we can with the best of our current personnel, but there is little technical personnel fully dedicated to Double Chooz. Furthermore, some specialised knowledge required consultation to specialised safety engineers (not originally foreseen) that has led further delays in the documentation. This has been cleared by early DEC. So, the (relatively) good news is that most issues are cleared to launch operations in 2019 — complete documentation and permissions. The extra further personnel for the dismantling is also being resolved — this was expected originally to be ready by NOV 2018, but the person sought turned unexpectedly unavailable in the last minute. The bad news is that, honestly, I do not easily see the APRIL 2019 date. We remain very sensitive to your requirements — driving our agenda — and we will do whatever possible too try to meet them but there is no easy way to bypass key condition of work in a nuclear reactor environment. This is something beyond usual scientific frameworks such as CERN or alike. Beyond this advance, I cannot offer you nor further or more precise information without consultation to our technical coordination team, soon upon return to work. However, we shall get back to you shortly. We can then do a phone call discussion. Cheers, Anatael

5. Can we help DC detector disassembly? • We found no way to help finding a supervisor. • DC Japan grant for the dismantling work should be used till the end of March 2019. • JSNS2 may provide 3~5 people (US:1, UK:1, Korea: 1 or 2, Japan:1 or 2) for the DC PMT retrieving work. • We may seek for additional European collaborators so that they may provide resources for the DC detector disassembly. No success yet.

6. Any possible alternative options? • We should consider setting a deadline to make a decision on our action regarding the PMT delay. • The DC PMT would be installed in late 2019 in the best possible case. However, in reality, the DC disassembly could delay our data taking longer because of uncertain work progress on the other side. • The best alternative option would purchase new PMTs and start data taking in late 2019 or in early 2020 if one of Japanese grant applications is selected. • Using available ~100 PMTs, we may start data taking with partially installed PMTs in Oct. 2019.

7. Early data taking with partial PMTs • The maximum number of 10 inch ID PMTs available from the internal resources: ~110 • 6 (Tohoku, already installed in the detector) • 65 (Korea, RENO mockup: 31 + spare 34) • 33 (Japanese DC dismantle budget, 10 Myen) [* 10 inch PMT price: 2.9 k USD or 0.3 Myen per PMT] • ~8 (~2.5 Myen(?) from common fund) [* Taka described usage and expected amount of common fund that would be presented and discussed in an IB meeting.] • It takes a few months to purchase and obtain PMTs and a couple of months to install the PMTs, and thus data-taking with this option would be possible after June, 2019. [** For data taking 24 Veto PMTs are also needed.]  110 – 24 = 86 (ID PMTs) • Data-taking with partial PMTs would allow a dry run, debugging, and performance check of the JSNS2 detector as a commissioning run without being idle during the DC delaying period. However, it will take additional 4 or 5 months for installing remaining PMTs.

8. Performance of detector with partial PMTs photo coverage: 192 8” PMTs ~ 123 10” PMTs • Study for 96 PMTs by Hyoungku Jeon (ATDG meeting) • Performance of energy resolution: s/E ~2.5%, comparable to that (~2.3%) of 192 10 inch PMTs (see p. 5 in his slide on 1/9/2019) • Performance of vertex resolution: sx,y,z~6.7cm comparable to that (~5.6cm) of 192 10 inch PMTs (see p. 8 in the slide on 1/16/2019) 96 PMTs 192 PMTs

9. Possible options: pros and cons [* It will be known in March, end of April, or end of June, 2019, All PMTs can be purchased for 5M$ approval. ~100 PMTs can be purchased for 1.5M$ approval. + Korean PMTs + Japanese fund

10. Back-up plans in timeline 2019 2020 6 2 4 1 3 5 7 11 8 9 10 2 12 1 No Supervisor? PMT installation Physics data taking Yes ~110 partial PMTs Dry & calibration runs No Physics data taking No data taking (??????) Yes Barrel & bottom PMTs ~50 PMTs Top 30 PMTs 5M$ grant? 86 ID + 24 OD 1.5M$ grant? No Yes

11. Summary • Serious delay of JSNS2 due to slow progress of DC dismantling work • Need our own efforts and a backup plan to minimize damage of PMT delay • We should consider setting a deadline on our action according to the PMT delay. • Find possible and best options for early data taking and results. • Make serious efforts to purchase PMTs and study the performance of JSNS2 with partial PMTs.