1

Gen2 DOM - the next generation
IceCube-Gen2 neutrino detector
candidates

Kareem Farrag on behalf of the IceCube Gen-2 Collaboration, ICEHAP, Chiba University
Chiba Satellite Workshop
Tuesday 8th August 2023
2023-08-06

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The Gen2 DOM = combination upgrade design!

Credit: N. Shimizu/ICEHAP

Credit: S. Niedworok/DESY

D-Egg

mDOM

2x 8’’ HQE PMTs & dia. 30 cm

24x 3’’ PMTs & dia. 36 cm

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06 2

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The Gen2 DOM = combination upgrade design!

mDOM

444 mmCredit: S. Niedworok/DESY

18 PMT option

540 mm

16 PMT option

Credit: N. Shimizu/ICEHAP

D-Egg
2x 8’’ HQE PMTs & dia. 30 cm

24x 3’’ PMTs & dia. 36 cm

312 mmKareem Farrag

ICEHAP, Chiba University (千葉大学)

318 mmIceCube Gen-2 Collaboration

2023-08-06 3

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Technical Design Report are now online

TDR link here: https://icecube-gen2.wisc.edu/science/publications/TDR/Part 1: Science and Conceptual Designs
Introduction, Gen-2 Science + Gen-2 Design
Overview
Yuya’s talk!
Part 2: Detector and Performance
South Pole’s potential for astrophysics, Optical
Array, Radio Array, Surface Array, Surface and Data
Acquisition Infrastructure, Data Systems andInfrastructure, Detector Calibration

Scan for
TDR!

Yuya’s talk!

Focus of this Talk and work in progress (to be published circa fall 2023):
Part 3: Detector Construction and Logistical Support Requirements

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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About Gen2
• IceCube-Gen2 = high energy extension of IceCube Neutrino Observatory at the SouthPole• 120 new strings, instrumented between depths 1.35 - 2.7 km, with 240 m inter-string
spacing• Each string has 80 Optical Modules with 17 m separation3• About 8 km of the detector volume will be covered by 9,600 new Optical Modules• Due to the extended inter-string spacing compared to IceCube, 125 m, we aim todevelop an Optical Module that has four-times better sensitivity compared to IceCube
Digital Optical Module (see Yuya’s talk!)

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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Drilling is very expensive
Just to see how much…

2023-08-06

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Drilling is a huge driver in cost
• Firn drill for first 50m sincesnow cannot hold water in
prep for hot-water drill• Per 10 holes = 225000 litresof fuel + 150 tons of cargo!
∘• 80 C water sent through 2.5km
hose to dedicatedinstrumented drill head

Image: Jim Haugen, IceCube/NSF

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

8

About Gen2
• Achieving this high sensitivity is possible by installing a larger number of small
diameter Photomultiplier Tubes (PMTs) in a larger pressure vessel• However, unlike other neutrino telescopes, the enormous cost of ice
drilling at the South Pole limits the size of the pressure vessel• The requirement on the diameter of the module is 12.5 inch even smaller thanthat of IceCube (13 inch)

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

9

SOUTH POLE

Construction
Considerations

Optical Sensor Types (4” PMT)
Materials
Cost
Construction Techniques
Implementation and Assembly(sealing)
Electronics, DAQ and Cabling
Scalability
Holding and Harnessing
Pressure
OpticsPenetrator

Transportation
Considerations

Packing
Protection from Exposure
Shipping and Cargo
Storage in heat
Storage in cold
Shock Test

Deployment
Considerations

Drilling Requirements (¥¥¥)
Load and Buoyancy/Weightbearing
Durability/Pressure from ice
Impact of cold temperature

Optical Detector Construction and Logistical Support Requirements
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

10

We can summarise Gen2’s biggest challenges

High module sensitivity(=complexity)

SevereMechanical Requirements

Durability for decades

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

11

We can summarise Gen2’s biggest challenges

High module sensitivity(=complexity)

Compact as possible

SevereMechanical Requirements

Light as possible

Durability for decades

Feasible to produce 9600!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

12

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
2. How will we make coupling scalable for the O(200000) PMTs?
3. How can we assemble the Gen2 DOM?
4. Will the Gen2 DOM survive severe pressure under the ice?
5. What is the response of the optical gel under pressure?
6. Can the Gen2 DOM survive the severe cold temperatures?

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

13

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
2. How will we make coupling scalable for the O(200000) PMTs?
3. How can we assemble the Gen2 DOM?
4. Will the Gen2 DOM survive severe pressure under the ice?
5. What is the response of the optical gel under pressure?
6. Can the Gen2 DOM survive the severe cold temperatures?

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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About the Gel

2023-08-06

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Gel properties• Shin-Etsu OSN(X)-3457-HE-A/B• First used in the D-Egg• Two-part silicone; polymer addition
reaction• High UV transmittance
Credit: N. Shimizu/ICEHAP• Elasticity to accommodate thermal∘

compressions down to -40 C

D-Egg
2x 8’’ HQE PMTs & dia. 30 cm• Mixing/Pouring Gel ⇒ air bubbles (these
affect optics and therefore must be
mitigated)

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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Gel pads• Discontinuities in the refractive

indexes of materials between theglacial ice and PMT glass must be
minimised to efficiently capture
Cherenkov photons.

Glass
Ice

• Replace Air ⇒ UV-transparent

conical-shaped silicone elastomers
called “gel pads.

PMT• Gel pads have a rim/cavity design
to allow for back-filling when
applying to glass housing

flKareem FarragRe ection
ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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Gel pad cavity filling

16 PMT option lling @ PSL
18 PMT option lling @ SeisgadgetfifiKareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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How we make themTwo sheets of either polypropylene/
High-impact polystyrene in our jigs

Kareem FarragWe cast our PMTs inside prevacuumed gel to avoid air bubbles,
then vacuum again

ICEHAP, Chiba University (千葉大学)

We then cure our vacuumed gel
pads ready for integration into
our module

IceCube Gen-2 Collaboration

2023-08-06

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How we make themTwo sheets of either polypropylene/
High-impact polystyrene in our jigs

We cast our PMTs inside prevacuumed gel to avoid air bubbles,
then vacuum again

Later we have a tour of our facilities so please enjoy!
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

We then cure our vacuumed gel
pads ready for integration into
our module

IceCube Gen-2 Collaboration

2023-08-06

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A big challenge with gel … bubbles!

Before vacuum applied
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

After vacuum applied
IceCube Gen-2 Collaboration

2023-08-06

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Takeaway - Gel Pads
• We established how to manufacture Gel Pads for photomultipliers in orderto parallelise production of many modules and integrate 4” PMTs into glass• We developed multiple designs that successfully couple to the glass

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

22

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
4. Will the Gen2 DOM survive severe pressure under the ice?
5. What is the response of the optical gel under pressure?
6. Can the Gen2 DOM survive the severe cold temperatures?

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

23

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
4. Will the Gen2 DOM survive severe pressure under the ice?
5. What is the response of the optical gel under pressure?
6. Can the Gen2 DOM survive the severe cold temperatures?

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

24

Assembly2023-08-06

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Internal Structure• The support structures for the two pressure vessel designs are based on
similar principles.

• The internal architecture of both designs features a central rod as the point ofreference for the internal configuration.

• A PMT holder, made of folded sheet metal, encases the central rod.
• The folded metal plate features circular apertures through which PMTs areinserted.

• In the case of Model-16 the central rod is directly attached to the glass vessel.
• For Model-18, the rod is supported around the central PMT due to thepresence of additional PMTs at the top and bottom of the vessel

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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Internal Structure Continued•

The second mechanism is a relatively simple design made of six metal springs on screws.

•

During installation, the spring mechanism is in the retracted position. After release, the springspress the gel pads of the PMTs against the pressure vessel glass.

•Open space behind internal structure used for clearance of wuBases (similar in 16-option)

Two mechanisms have beendeveloped for the PMTs toapply outward pressure• The first mechanism uses a bushing bearing to protect the PMT glass from the
sheet metal and allows the PMT to move back and forth along its axis.

• inflatable support collar is used to push PMTs pads against glass, and epoxy ispressed into the support collar and cured• Epoxy ⇒ no leaks ⇒ bladder doesn’t collapse• Since collar compressible around the neck of the PMT ⇒ elasticity of the mechanics
in response to shrinkage of the module due to outside pressure.

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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PMT Internal structure

Forms used in 16-Option. Image: Yuya Makino/PSL

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

Internal Structure using compressible collars. Image: Yuya Makino/PSL

IceCube Gen-2 Collaboration

2023-08-06

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PMT Internal structure

Central shaft demonstrated in 18-Option.
Image: KF, ICEHAP

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

Internal Structure assembly + unadhered Gel Pads.
Image: KF, ICEHAP

IceCube Gen-2 Collaboration

2023-08-06

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Takeaway - Assembly• We successfully created two options to integrate PMTs and electronics given
the Gen2 DOM options’ compactness via internal support structures• The structure both secures components, pushes PMT+Gel Pads against
glass and provides sufficient clearance to enable electronics/cablingcomponents sit well within the module

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

30

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
Using internal support structures to improve clearance and prevent delamination of gel pads
4. Will the Gen2 DOM survive severe pressure under the ice?
5. What is the response of the optical gel under pressure?
6. Can the Gen2 DOM survive the severe cold temperatures?
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

31

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
Using internal support structures to improve clearance and prevent delamination of gel pads
4. Will the Gen2 DOM survive severe pressure under the ice?
5. What is the response of the optical gel under pressure?
6. Can the Gen2 DOM survive the severe cold temperatures?
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

32

Pressure Testing2023-08-06

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What kind of pressure are we facing?
• P(h) = ρice × g × h ∼ (9000 × h) Pa
5• Every ~10 m depth = 10 Pa additional pressure, so our vessel needs towithstand at depths 3 km approx. 30 MPa• Our requirement for clearance of this threshold is 2.5 × this = 70 MPa

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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Pressure/Strain Tests @ JAMSTEC

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

35

Pressure/Strain Tests @ JAMSTEC
We performed two test
cycles(18 Option prototype)
Experiment One
0.6MPa/min until 70.9MPa
Hold for 10 mins
-2.0MPa/min to 0MPa
Experiment Two
0.6MPa/min until 50.7MPa
Hold for 10 mins
-2.0MPa/min to 0MPa

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

36

Strain Tests

Cyanoacrylate glue
20-60s cureSingle component
adhesive

7 WM2000SA loggers
Max memory 32KB
1Hz sample rate ⇒ 9hours
Default assumption strain gauge 2.0• Each air logger was thenattached to linear strain
gauge (Kyowa
KFGS-5-120-C1-11) madefrom polyamide/CuNi alloy
foil• Linear gauge insensitive tolateral force, but extension/
compression increases/
decreases gauge resistance

Gauge factor

ΔR/R= 2.12 ± 1 %ΔL/L

Kareem Farrag

ICEHAP, Chiba University (千葉大学)• Sensitive to O(μϵ), strain
ϵ = ΔL/L

IceCube Gen-2 Collaboration

2023-08-06

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70MPa glass test performance… success!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

38

50MPa glass test performance… success!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

39

70MPa gel pads test performance… success!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

40

50MPa gel pads test performance… success!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

41

Pressure Tests @ PSL• Similar pressure testing done for the

Nautilus glass used in 16-PMT Option• Module remains intact under 70 MPa
pressure … successfully retrieved!

See Yuya’s talkKareem FarragDeformation: 3.9mm (H) /2.4mm (V) at 70 MPa

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

42

Takeaway - Pressure Test
• Pressure testing was successful in both our prototypes for the Gen2 DOMs
• Both Nautilus/Okamoto glass options satisfy requirement of durability under
70 MPa pressure, exceeding subglacial pressure exertion• Deformations kept within requirements of ~5mm reassuring us that thevessel is durable enough for operation requirements

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

43

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
Using internal support structures to improve clearance and prevent de-lamination ofgel pads
4. Will the Gen2 DOM survive severe pressure under the ice?
Yes! 70MPa tests succeed in both Nautilus and Okamoto glass!
5. What is the response of the optical gel under pressure?
ShinEtsu Silicone displays good elasticity performance at severe pressure
6. Can the Gen2 DOM withstand the severe cold temperatures?
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

44

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
using internal support structures to improve clearance and prevent de-lamination ofgel pads
4. Will the Gen2 DOM survive severe pressure under the ice?
Yes! 70MPa tests succeed in both Nautilus and Okamoto glass!
5. What is the response of the optical gel under pressure?
ShinEtsu Silicone displays good elasticity performance at severe pressure
6. Can the Gen2 DOM withstand the severe cold temperatures?
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

45

We’ve been working on answering the following
1. How should we mechanically (and optically) couple the PMTs to the glass?
Silicone gel sensitive to Cherenkov Photons
2. How will we make coupling scalable for the O(200000) PMTs?
Pre-casting PMTs into Gel Pads for coupling to the glass
3. How can we assemble the Gen2 DOM?
using internal support structures to improve clearance and prevent de-lamination ofgel pads
4. Will the Gen2 DOM survive severe pressure under the ice?
Yes! 70MPa tests succeed in both Nautilus and Okamoto glass!
5. What is the response of the optical gel under pressure?
ShinEtsu Silicone displays good elasticity performance at severe pressure
6. Can the Gen2 DOM withstand the severe cold temperatures? Yes!
Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

46

Cold Temperature Testing2023-08-06

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Temperature test
• We need to check for any

mechanical performance issues for
the Gen2 DOM in cold
temperature (eg compressions,
delaminations of Gel pads) under∘-40 C temperature which ourmodules will experience during
deployment• In order to test this, we placed our
prototype in the freezer for 6.5
weeks

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

48

Temperature test
• In this test, we placed the 18-

Option Gen2 DOM into the freezer∘
at -40 C and monitored using ourlinear strain gauges until our
loggers ran out of power• We continuously left ourdemonstrator module beyond thispoint, and monitored once dailyfor de-lamination and detector
robustness

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

49

Temperature test

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

50

Takeaway - Temperature test
• We confirmed the Gen2 DOM can withstand thermal compression when∘

deployed in -40 C conditions• The gel provides enough elasticity and degrees of freedom to prevent delamination of gel pads from glass• This reversibility is great sign for when we integrate functional PMTs and test
their properties at low temperature, as in the current upgrade modules

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

51

We still have more work to do!
• Moving forward, we plan to integrate functional components and produce aworking half of both 16 and 18 Option modules by approx. the end of thisyear.

• Following our R&D, we aim to converge our designs in the coming months
with our focus on optimise both detector performance and production
procedure, whilst satisfying cost constraints• This means we have to study electronics and cabling, per-module detector
responses, flashers, harnessing and much more ahead!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

52

Conclusions• We have been researching and developing

prototype Gen2 DOM designs to be implementedin IceCube Gen2 as well as in IceCube Upgrade• Our approach - exploring two similar designs that

fit the design requirements of compactness but
sufficient complexity as stated in the IceCube TDR• We successfully built mechanical halves of bothdesign concepts and have tested their mechanicalperformance in extreme pressure, temperature all tests succeeded• Our efforts moving forward will dedicate creating

functional demonstrator modules for both 16 and
18 PMT options - in fact we are already working on
this now, stay tuned!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06

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Thank you!

Scan for
TDR!

Kareem Farrag

ICEHAP, Chiba University (千葉大学)

IceCube Gen-2 Collaboration

2023-08-06