Status multiPMT OM design Eric Heine and Patrick Werneke Nikhef

Design programme 1st Mechanical Reference Model (finished) Assembly test Cooling test 2nd Mechanical Reference Model (being built) Further optimisation PMT base development PMT tests in water with K40 (just started) 3rd Reference Model

Construction and tests on Reference Module 1 have been completed Mechanical RM1 Construction and tests on Reference Module 1 have been completed

Mechanical RM1 Reference Module 1: 31 mechanical 3” PMTs in a 17” sphere 19 in the bottom hemisphere 12 in the top hemisphere Pre-molded silicone rubber pads for the optical interface Foam core to hold the PMTs and springs

Mechanical RM1 – assembly test Assembly went well: Used rubber band to hold PMT’s in position Released rubber bands one by one

Mechanical RM1 – assembly test Lens did not make perfect contact with sphere: Need more R&D time for finding optimal shape Mechanical engineers confident problem can be solved, if this is the preferred solution

Mechanical RM1 – cooling test Latest inventory; 2 W 0.2 W 0.03 W 19°C 2 W 15°C 5 W 1.5 W 22°C 1.5 W 24°C 60 mW /PMT Temperature measurements to check the calculation model. Heat pipe only transfer heat from warm end to cold end. Since most heat is generated next to the shield the expensive heat pipe seems not necessary. Next reference module will be without a heat pipe but with a solid stem. With different PCB layouts, cables and connectors can be minimized. The PCB with the electrical and optical conversions will be shielded to minimize RFI problems. Total: 11.9 W 5.4 W Next: Second reference module with other form factor PCB’s and solid stem Cooling requirements met easily

Mechanical reference models 1st Mechanical RM program finished + PMT/PCB suspension -/+ Optical interface need more R&D + Cooling conclusion: design feasible, assembly can simpler, cooling system can simpler, application of lenses feasible but need more R&D 2nd Mechanical RM program objectives Thin gel layer as optical interface Further optimization of cooling system and tooling Optimalization form factor printed circuit boards Test of assembly procedure in terms of personpower

OM assembly steps continued optimalization in terms of reliability and personpower lower hemisphere 1 add optical gel + 1.a 1.b 1.c 1.d 1.e A upper hemisphere 2a glue 2a.a 2a.b 2a.c 2b 2c add optical gel + 2b.a 2c.a 2c.b 2c.c 2c.d B B closing the sphere There are 3 clear steps: Preparing lower hemishere Preparing upper hemisphere Integration both parts with final tests. Foam cores, PMT modules and cooler are deliverables. 1.a combine PMT modules and foamcore 1.b add glass sphere, turn opside down, 1.c add ic-board 1.d carry out some tests, because next step is beyond repair 1.e glue foam core and PMTs with otical gel to the sphere 2a.a glue cooler in hemisphere (glue 1.2 to 3.2mm to adapt pressure movements) 2a.b,c add the boards with the storey functionality and add the connection to the outside 2a.d carry out some tests, because next step is beyond repair 2b.a combine PMT modules and foamcore 2c.a combine the filled foamcore with the prepared hemisphere 2.c.b add ic-board 2.c.c carry out some tests, because next step is beyond repair 2.c.d glue foam core and PMTs with otical gel to the sphere 3.a add special tooling 3.b combine the products of 1 and 2 3.c move to a test stand, with light test, vacuum, etc. 3.d perform all the final tests includung burn-in 3.e ready for store or integragration to a detection unit A 3 storage 3.a 3.b 3.c 3.d 3.e

OM assembly planning Next: Verification with 2nd reference model A number of tasks of the previous sheet can be done in parallel. In this planning the cure times of glueing actions are in the over night period. In this way one module = one storey takes 3 days with about 2 persons. Possible with < 2 FTE Next: Verification with 2nd reference model

E/O Diagram STO-OM sphere- logic conversions ln+1 PMT-base pre- amp 12+19 sphere- logic conversions photons ln+1 PMT-base pre- amp 2 comp sphere logic LVDS apd BOB ln ic-board th dac HV tim.,sc ID i2c cpld decoder i2c 3V3 hv dac osc.1 feed back 400V switch switch 3V3 switch proto PMT-module extra electr.

STO - OM module Storey functionality OM functionality 1 . 12 base 1 . 12 ic base fuse splice conn. sphere e/e e/o sphere logic base From previous calculations (presented 4-12-08, WP7) STO-OM: l ≈ 300 FIT 1 . 19 ic The STO-OM blocks can be more detailed. This will represent the real circuit elements. On the base of calculation a FIT rate is calculated of <300 failures in 10^9 hours Failures / collection x 1 / mission time base Meaning; ≈220 failures out of 6000 items in 10year, less then 10% (CDR p.43). Next; Reliability formulea from WP7, Availability formulea from WP7

+ Reliability strategy Stress factors; Mobility Temperature Parts 22% Manufacturing 15% Design 9% System management 4% Wear-Out Induced 12% No Defect 20% Software 1 FIT = 1 failure in 109 hours MTBF=114000 years 465 FITs :: MTBF= 245 years 807 FITS :: MTBF= 141 years + Stress factors; Mobility Temperature High voltage Design errors must be avoided by worst case design and prototype testing Manufacturing errors must be avoided by production testing Extended FIT-rate: *pm* pt* pu 22 100 le»ls*

PMT base status 2/2009 HV circuit PMT 10 dynodes, cathode voltage -800 V - -1200 V Vripple <150mV/dynode, dV/dt < 75 mV/ms Stabilization 0.95% on 38% input variation Vinput 3.3 V Load < 4.5 mW Next; RFI measurements Tests with PMTs Optimize form factor Integration of controls (HV-level, Treshhold) Integration of pre-amp and comparator (VLSI) In the densely packed multi PMT Optical module The HV generation for the PMT’s has to be small with a very low dissipation. The circuit is based on a fly back converter follows with a Villard (or Cockcroft Walton) cascade. proto

Thanks for the attention

RM2 ideas 1 With solid stem in the cooler Foam next to the glass. A few gel will be sufficient

RM2 ideas 2 Replacing the PCB. Vertical board for the lower hemishere have 2 keys to which tooling is locked on the moment to integrate the both halves. In this way we are able to make the connection at the top without any cable and extra manual handling.

Mechanical RM1 – cooling test Thermal Results: Picture: total of 12W PMT Base = 60 mW/base Logic = 7W Interconnect = 3W Maximum T= 27.9 °C For nominal values: PMT base = 30 mW/base Logic = 4W Interconnect = 2W Maximum T = 22.7 °C The heat exchanger did not work according to specification: ~ 500 W/m·K instead of 5000 W/m·K

Mechanical RM1 – cooling test Status of the Multi PMT Optical Module development. Mechanical RM1 – cooling test Thermal requirements Sea, Tsea=14°C asea=500W/m²K sphere logic electronics T<40°C interconnection boards T<40°C PMT base electronics T<40°C There are some arguments to keep the temperature low as possible; -Temperature has a major impact on the lifetime. By the rule of Arrhenius each 8-10°C means a factor 2. -Solder with lead free solder gives a higher chance on more and longer tin whiskers, according the experiences at NASA Space-station. -Low temperature for the PMTs means low dark count rates. Each 5°C a factor of 2. PMT Foam core Silicon lenses contribution to WP 3,4,5 meeting Paris 151008