summary of mechanical testing of pmts

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Summary of mechanical testing of PMTs Milind Diwan 1/26/2011

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Summary of mechanical testing of PMTs. Milind Diwan 1/26/2011. PMT Pressure performance. Primary Objective: The primary objectives of these tests are to eliminate the risk of PMT implosion and its effect that can cause an implosion chain reaction in neighboring PMTs. - PowerPoint PPT Presentation

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Page 1: Summary of mechanical  testing of PMTs

Summary of mechanical

testing of PMTsMilind Diwan

1/26/2011

Page 2: Summary of mechanical  testing of PMTs

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PMT Pressure performance Primary Objective: The primary objectives of these tests are to

eliminate the risk of PMT implosion and its effect that can cause an implosion chain reaction in neighboring PMTs.

• Stage 0 small chamber tests conducted at BNL on two manufacturer’s PMTs have identified that each manufacturer’s PMT implodes via a different mode. DONE

• Stage1-phase1 conceptual design and evaluation of a facility for testing of implosion abatement DONE

• Stage1-phase2 is to refurbish and establish the facility for complete testing of implosion abatement.

- In this stage we will measure the magnitude of shock wave pressure due to a single PMT implosion under hydrostatic pressure and to see how the shockwave magnitude varies while implosion. The mechanical design team, with the assistance of NUWC will analyze the test results to make sure the testing protocol is appropriate. DONE(to be reported here)

• Stage 3 test will be testing of PMTs using the COMPLETELY designed implosion abatement scheme. Requirement of this test will be determined by Stage 2 tests. (We are now ready for this)

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PMT pressure performance In Scope

• Define physical parameters (time scale, intensity, and distribution) of hydrodynamic pressure pulse due to breakage of a single PMT by means of analysis and experimentation.

• Impact on functional performance of neighboring PMTs in case of single PMT failure by pressure pulse

• Full scale testing of structural PMT support interface including an array of tubes and its reaction to single PMT failure pressure pulse .

Out of Scope• The following are considered out of scope of Test Plan:

• Material testing (PMT mounts, base etc.)

• Electrical Performance testing of PMTs+base assembly under pressure.

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Facility for pressure testing

Very large amount of documentation now on DOCDB.

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Storage tank

Pressure tank

50 ft diameter

rated for 100 psig

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Procedure

Place PMT make sure

cameras and lights work

For each sensor finger test and

test DAQ

Test noise level, no good wet pretest exists

Release pressure, start draining, secure data,

photograph after draining.

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•Tank is pressurized with air upto 88 psi•Poker is activated by pressurization with nitrogen

•For test on Dec. 16 poker was activated using a pressure accumulator. This failed at 1500 psi and succeeded at ~3000 psi•For test on Dec. 17 poker was activated slowly by continuously raising the pressure. Needed >4000 psi hydraulic pokerDec 16 test

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Dec 16 test

Setup for Dec 17

poker 1/16”

Page 12: Summary of mechanical  testing of PMTs

Conditions were cold, we had to time the events so that there was enough

time for draining and refilling operation. Refilling took 12-14 hours

for 1/2 tank due to slow filtering. Draining was faster.

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Initial look at data

Dec 16-RA0249 Dec 17-RA0284

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200kHz data

Dec 16-RA0249 Dec 17-RA0284

Speed of sound 1497 m/sec (at 25 C)

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TableDec-16-2010

Sensor Max(psi) FWHM(us) integral(psi*s)ACC5 300.326 18 0.021201ACC2 488.605 12 0.0239284ACC1 427.451 14 0.0219069ACC3 287.754 14 0.0179908ACC4 410.826 11 0.0183837ACC6 169.847 12 0.0102897ACC11 802.362 22 0.0544762

Dec-17-2010

Sensor Max(psi) FWHM(us) integral(psi*s)ACC5 350 40 0.024515ACC2 350 30 0.0224999ACC1 337. 40 0.0206258ACC3 290 30 0.0201209 ACC4 223.36 55 0.0191678ACC6 154.65 30 0.010826ACC11 1800.2 12 0.0730299

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PMT Implosion Test Predictions 16

PMT Implosion TESTS Simulations & “blind” Predictions

including:

* NAVSEA PMT Implosion Tests* BNL Hydrostatic PMT Tests* Navy Glass Sphere Implosion Test and Bubble Oscillation Confirmation

 N. SimosNuclear Science Department & Photon Science Directorate

January 25, 2011

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PMT Implosion Test Predictions 17

Benchmarking of implosion process against US Navy glass sphere tests and “exact” solutions of bubble oscillation

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PMT Implosion Test Predictions 18

VERIFICATION OF BNL IMPLOSION Model/Analysis:Experiments (Navy test on glass sphere implosion)

Experiment Pressure Recordings at 102 mm from centerData to compare predictions against

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PMT Implosion Test Predictions 19

VERIFICATION OF BNL IMPLOSION Model/Analysis:“Exact” Solutions of Air Bubble Collapse/Oscillation

“Exact” solution of bubble contraction/expansion “Exact” solution of bubble contraction/expansionPressure generation

BNL Simulation predictions. PERFECT match of contraction time to minimum bubble size, time arrival of pressure pulse and Pressure Pulse Amplitude

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PMT Implosion Test Predictions 20

PMT Implosion Tests

BNL Hydrostatic Tests

NAVSEA Tests

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PMT Implosion Test Predictions 21

PMT glass model

Simulation were performed ahead of all BNL and NAVSEA Tests

Relied on:• Arbitrary Eulerian-Lagrangian (ALE) formulation that allows solids (PMT glass) and fluids to interface• Exact reproduction of the PMT shape of “varying” cross section/thickness• Large model to incorporate the surrounding water (for the NAVSEA test a model consisting of 2,240,000 solid and fluid elements requiring ~240 hrs of CPU for 6 msec implosion duration was used)

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PMT Implosion Test Predictions 22

PMT inner volume density evolution

Tank Volume Pressure Drop (confirmed in test)

Pulse arrival time 20+ micro-secs CONFIRMED by test

PMT fractureSimulation Predictions confirmed by the BNL Tests:No shock develops !!Implosion process very long (20+ ms)Hydrostatic pressure limit ~270 psi (19 Atm) !!!

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PMT Implosion Test Predictions 23

BNL Hydrostatic tests and PMT instability predictions

Observed in the simulations is an instability modewhich is influenced by the strength of the base (or neck)where failure seems to initiate at much lower than anticipated (2nd mode) external pressure.

Hydrostatic tests at BNL showed similar results where PMTs failed hydrostatically at 19 Atm.

Predicted crack initiation/propagation

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PMT Implosion Test Predictions 24

“Blind” Predictions of the NAVSEA Implosion Tests

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PMT Implosion Test Predictions 25

Based on a 2,240,000+ fluid/solid element model and “adjusted” PMT glass constitutive and fracture relations, the implosion at 88 psi water pressure was simulated (~240 hrs CPU on a 8-cpu dedicated PowerEdge microstation)

• Predictions of pressure pulse at various sensor locations were very close to the test results.

• Also confirmed were the attenuation (as function of 1/r) and the pulse propagation velocity

Initiation & propagation of pressure pulse

PMT fracture evolution

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PMT Implosion Test Predictions 26

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PMT Implosion Test Predictions 27

attenuation Pulse propagation velocity

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- Rahul Sharma

PMT Stress Analysis

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Model Features, Loads and Constraints AppliedModel Features:Pads around dome simulating PA holding PMTPMT base encapsulation incorporated in the modelSplit model and sweep mesh features used to get fine

mesh

Loads and Constraints:**Please note that values used for loads in the model

may not be exact but are very close and can be modified

External Pressure of 7barBuoyant Force on PMT = 100 N (Assumption)Gravitational ForcePads constraining PMT domePMT base encapsulation constraining PMT close to neck

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PMT Model

Pads

PMT Base Encapsulation

PMT

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Results

Maximum Stress of 16.64 MPa.Maximum stress area after base encapsulation shifts to the neck of the tube.

Maximum Stress Area

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12 inch development

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Development on glass testingAs far as we can estimate, >50% of the cost of the tube is in the glass.

About 20% is in the rest of the materials, and rest in assembly.

Cost of the tube cannot be lowered by replacing the dynode structure by some other structure.

The 10 inch tube has 1 kg of glass; the 12 inch has 1.8 kg of glass. The detector consists of 30-40 tons of glass.

We must understand the requirements on this glass under stress in ultrapure water.

We have created a collaboration with Alfred university to provide us input into this.

Glass samples from both vendors have been sent to Alfred.

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SummaryWe have a complete facility that mimics the environment at the bottom of the 60 meter tall water Cherenkov detector. We are confident of mounting significant and detailed tests of our designs.

We have demonstrated a complete simulation from first principles of a PMT implosion event and found it to agree well with the data. It can be developed further for chain reaction modeling.

We have sufficient number of 12 inch PMT bulbs for further testing.

Collaboration with Alfred University on glass under stress in ultrapure water has expanded; student and new faculty on-board.

Next phase is on-going at BNL with the small pressure vessel. We are setting up for slow-pressure-rise tests with larger statistics.