1. Status multiPMT OM design
Eric Heine and Patrick Werneke
Nikhef

2. 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

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

4. 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

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

6. 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

7. 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

8. 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

9. 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 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

10. 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

11. 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.

12. 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 , 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

13. + 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= years
465 FITs :: MTBF= years
807 FITS :: MTBF= 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*

14. PMT base status 2/2009 HV circuit PMT 10 dynodes,
cathode voltage -800 V 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

15. Thanks for the attention

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

17. 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.

18. 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

19. 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