Prediction of chamber condition at long time scale is the goal of chamber simulation research.

Chamber dynamics simulation program is on schedule. Program is based on: Staged development of Spartan simulation code. Periodic release of the code and extensive simulations while development

of next-stage code is in progress.

Chamber dynamics simulation program is on schedule. Program is based on: Staged development of Spartan simulation code. Periodic release of the code and extensive simulations while development

of next-stage code is in progress.

Documentation and Release of Spartan (v1.0) Two papers are under preparation

Exercise Spartan (v1.x) Code Use hybrid models for viscosity and thermal conduction. Parametric survey of chamber conditions for different initial conditions

(gas constituent, pressure, temperature, etc.) Need a series of Bucky runs as initial conditions for these cases. We should run Bucky using Spartan results to model the following

shot and see real “equilibrium” condition. Investigate scaling effects to define simulation experiments.

Documentation and Release of Spartan (v1.0) Two papers are under preparation

Exercise Spartan (v1.x) Code Use hybrid models for viscosity and thermal conduction. Parametric survey of chamber conditions for different initial conditions

(gas constituent, pressure, temperature, etc.) Need a series of Bucky runs as initial conditions for these cases. We should run Bucky using Spartan results to model the following

shot and see real “equilibrium” condition. Investigate scaling effects to define simulation experiments.

Several upgrades are planned for Spartan (v2.0)

Numeric:

Implementation of multi-species capability: Neutral gases, ions, and electrons to account for different thermal

conductivity, viscosity, and radiative losses.

Physics:

Evaluation of long-term transport of various species in the chamber (e.g., material deposition on the wall, beam tubes, mirrors) Atomics and particulate release from the wall; Particulates and aerosol formation and transport in the chamber.

Improved modeling of temperature/pressure evolution in the chamber: Radiation heat transport; Equation of state; Turbulence models.

Numeric:

Implementation of multi-species capability: Neutral gases, ions, and electrons to account for different thermal

conductivity, viscosity, and radiative losses.

Physics:

Evaluation of long-term transport of various species in the chamber (e.g., material deposition on the wall, beam tubes, mirrors) Atomics and particulate release from the wall; Particulates and aerosol formation and transport in the chamber.

Improved modeling of temperature/pressure evolution in the chamber: Radiation heat transport; Equation of state; Turbulence models.

Progress in UCSDChamber Simulation Experiments

Farrokh NajmabadiSophia Chen, Andres Gaeris, John Pulsifer

HAPL Meeting

December 5-6, 2002Naval Research Lab, Washington, DC

Electronic copy: http://aries.ucsd.edu/najmabadi/TALKSUCSD IFE Web Site: http://aries.ucsd.edu/IFE

Thermo-mechanical Response of the Wall Is Mainly Dictated by Wall Temperature Evolution

Most phenomena encountered depend on wall temperature evolution (temporal and spatial) and chamber environment. Only sputtering and radiation (ion & neutron) damage effects depend

on “how” the energy is delivered.

Wall response depends strongly on the “spectrum” of incidence energy from the target blast. Target designs are not finalized and target spectrum is not known; There is no simulation source that can completely simulate the energy

spectrum from the target.

In order to develop predictive capability: Focus on achieving temperature profiles similar to those expected in a

laser-IFE wall (Laser, ion source and X-rays can all do this). Measure and understand the wall response in the relevant range of wall

temperature profiles and in real time.

In order to develop predictive capability: Focus on achieving temperature profiles similar to those expected in a

laser-IFE wall (Laser, ion source and X-rays can all do this). Measure and understand the wall response in the relevant range of wall

temperature profiles and in real time.

Thermo-Mechanical Response of Chamber Wall Can Be Explored in Simulation Facilities

Capability to simulate a variety of wall temperature profiles

Capability to simulate a variety of wall temperature profiles

Requirements:

Capability to isolate ejecta and simulate a variety of chamber environments & constituents

Capability to isolate ejecta and simulate a variety of chamber environments & constituents

Laser pulse simulates temperature evolution

Laser pulse simulates temperature evolution

Vacuum Chamber provides a controlled environment

Vacuum Chamber provides a controlled environment

A suite of diagnostics: Real-time temperature Per-shot ejecta mass and constituents Rep-rated experiments to simulate

fatigue and material response Relevant equilibrium temperature

A suite of diagnostics: Real-time temperature Per-shot ejecta mass and constituents Rep-rated experiments to simulate

fatigue and material response Relevant equilibrium temperature

Components of Simulation Experiment

Optical train Operational. YAG laser is upgraded with injection seeding for reproducible and smooth temporal profile.

Vacuum Chamber Operational. Capable to below 10-8 Torr.

High-Temperature Operational. Specimen “equilibrium” temperature Specimen Holder can be maintained at up to 1,200oC. Endurance runs of

several hours have been made at 1,000oC.

Master Timing Operational (~100ps gitter). Capable of single shot to Control System 10 Hz.

Data Acquisition System Operational (1GHz, 1.25 GS/s, upgradeable to 2.5GS/s).

Diagnostics: PIMAX & Spectrograph Operational. Thermometer Calibrated externally (< 2% error).

In-chamber shake-down and tests are in progress. IR Camera Purchase is deferred (exploring alternatives). Quartz Microbalancing Purchase order is being placed. RGA Purchase order is being placed.

Specimen preparation Procedure in place. Need measurement of thermophysical properties at elevated temperatures.

Specimen holder operating at 1000oC

High Temperature Specimen Holder is tested to 1200oC with endurance runs at 1000oC.

Stainless steel vacuum seal

Specimen holder is made of Mo

Thermocouple feed through

Power feed through

Specimen is heated by radiation from a tungsten element located behind the specimen.

Specimen is heated by radiation from a tungsten element located behind the specimen.

Specimen

Real-time Temperature Measurements Can Be Made With Fast Optical Thermometry

Temperature deduction by measuring radiance at fixed One-color: Use tables/estimates for ()

Typical error < 25%

Two colors: Assume (1) = (2)

Typical error < 5 % Three colors: Assume d2/d[usually a linear interpolation of

Ln() is used] Typical error < 1 %

Temperature deduction by measuring radiance at fixed One-color: Use tables/estimates for ()

Typical error < 25%

Two colors: Assume (1) = (2)

Typical error < 5 % Three colors: Assume d2/d[usually a linear interpolation of

Ln() is used] Typical error < 1 %

Spectral radiance is given by Planck’s Law (Wien’s approximation):

L(,T) = C1 (,T) -5 exp(-C2/T)

Since emittance is a strong function of , T, surface roughness, etc., deduction of temperature from total radiated power has large errors.

Spectral radiance is given by Planck’s Law (Wien’s approximation):

L(,T) = C1 (,T) -5 exp(-C2/T)

Since emittance is a strong function of , T, surface roughness, etc., deduction of temperature from total radiated power has large errors.

Published work with Multi-color Optical Thermometry: Complicated optical design Use fiber optics Response time of > 10-100 s Use fast PD or

PMT

Published work with Multi-color Optical Thermometry: Complicated optical design Use fiber optics Response time of > 10-100 s Use fast PD or

PMT

MCFOT Is a Natural Extension of Multi-color Optical Thermometry

MCFOT—Multi-Color Fiber Optical Thermometry

Simple design, construction, operation and analysis. Can be easily mounted inside a vacuum vessel. Easy selection of spectral ranges, via filter changes.

MCFOT—Multi-Color Fiber Optical Thermometry

Simple design, construction, operation and analysis. Can be easily mounted inside a vacuum vessel. Easy selection of spectral ranges, via filter changes.

Schematic of Multi-Color Fiber Optical Thermometer

Sensor Head can be focused to < 1mm2 spots.

Rugged design with accurate swivel controls allows sensor head to be focused to < 1mm2 spots with a high degree of position accuracy.

Steel foil protects the sensor head from thermal radiation.

Steel foil protects the sensor head from thermal radiation.

Thermal radiation is injected by the Sensor Head into four bundled low-OH Silica fibers and relayed into fast PMTs

Each branch of the fiber bundle is filtered in a narrow spectral band by an interference filter and connected to a fast PMT

MCFOT is calibrated using the Optronics UL-45U lamp with a total error of < 3%

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

1200 1400 1600 1800 2000 2200 2400 2600 2800

MCFOT calibration 8cm lens

(Tcal-T

3C)/

Tcal

T [K]

14 Calibration points

One adjustable parameter (c1c3/c22)

ci =Vi (PMT) / Li (Sensor head)

14 Calibration points

One adjustable parameter (c1c3/c22)

ci =Vi (PMT) / Li (Sensor head)

MCFOT is installed in the chamber and shake-down tests are in progress

System Improvements: Issue: Limited range of voltage from PMTs (need > ~ 5 mV for good SN

ratio, PMT output saturates around 200 mV) Channel balancing by using neutral density filters in each channel Balance between voltages from calibration lamp filament and specimen

to be handled by a neutral density filter in sensor head.

Reliability Issues: Calibration: How long it is dependable? Speed: Individual PMT response is better than 700 ps. Would thermometer

achieve the same response time? Sensitivity: what is the minimal T measurable? Ease of use: mounting, alignment, interference, vacuum. Maintenance: Is it foolproof? PMTs electrode degradation? Heat/vacuum

damage to optics/mechanicals? Fiber breakage?

System Improvements: Issue: Limited range of voltage from PMTs (need > ~ 5 mV for good SN

ratio, PMT output saturates around 200 mV) Channel balancing by using neutral density filters in each channel Balance between voltages from calibration lamp filament and specimen

to be handled by a neutral density filter in sensor head.

Reliability Issues: Calibration: How long it is dependable? Speed: Individual PMT response is better than 700 ps. Would thermometer

achieve the same response time? Sensitivity: what is the minimal T measurable? Ease of use: mounting, alignment, interference, vacuum. Maintenance: Is it foolproof? PMTs electrode degradation? Heat/vacuum

damage to optics/mechanicals? Fiber breakage?

Several Tungsten samples have been prepared for initial simulation experiments.

Each sample has its own pedigree. Samples have been prepared with different initial polishing and

cleaning method. Pre-shot surface examination has been performed. Similar samples are also prepared for testing at RHEPP.

Each sample has its own pedigree. Samples have been prepared with different initial polishing and

cleaning method. Pre-shot surface examination has been performed. Similar samples are also prepared for testing at RHEPP.

WYKO500X Microscope

Surface photograph of samples polished with 1 m grit

Development of predictable capability for the thermo-mechanical response of the chamber wall is the goal of UCSD simulation facility

Experiment Assembly: Thermometer shakedown should be completed by Mid January. Quartz Micro-balancing and RGA should be also operational in January.

Experiment Assembly: Thermometer shakedown should be completed by Mid January. Quartz Micro-balancing and RGA should be also operational in January.

Experimental Studies:

Temperature Response studies Impact of surface morphology and impurities/contaminants, etc.

Thermal Fatigue Studies Different temperature gradients, “equilibrium temperature,” etc.

Material Loss Studies Survey of impact of surface temperature, surface morphology,

impurities, etc.

NEED: Characterization of thermophysical properties of specimen at high Ts

Experimental Studies:

Temperature Response studies Impact of surface morphology and impurities/contaminants, etc.

Thermal Fatigue Studies Different temperature gradients, “equilibrium temperature,” etc.

Material Loss Studies Survey of impact of surface temperature, surface morphology,

impurities, etc.

NEED: Characterization of thermophysical properties of specimen at high Ts

Backup Slides

QCM Measures Single-Shot Mass Ablation Rates With High Accuracy

QCM: Quartz Crystal Microbalance Measures the drift in oscillation frequency of

the quartz crystal.

QCM has extreme mass sensitivity: 10-9 to 10-12 g/cm2. Time resolution is < 0.1 ms (each single

shot). Quartz crystal is inexpensive. It can be

detached after several shots. Composition of the ablated ejecta can be analyzed by surface examination.