Progress inChamber Simulation Experiments At

UCSD Laser Facility

Farrokh NajmabadiKevin Sequoia, Sophia Chen

HAPL Meeting

September 24-25, 2003University of Wisconsin, Madison

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

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 (High-speed

Optical Thermometer) Per-shot ejecta mass and constituents

(QMS & RGA) Rep-rated experiments to simulate

fatigue and material responseRelevant equilibrium temperature

(High-temperature sample holder)

A suite of diagnostics: Real-time temperature (High-speed

Optical Thermometer) Per-shot ejecta mass and constituents

(QMS & RGA) Rep-rated experiments to simulate

fatigue and material responseRelevant equilibrium temperature

(High-temperature sample holder)

Status of Diagnostics Development and Fielding

High temperature sample holder has been operational for quite some time.

RGA system was installed on the chamber and is routinely used to monitor chamber environment. No trace of W was found in the chamber (from heating filament of

the high-temperature sample holder). QMS was tested but has been removed form the chamber until we are

ready for test runs. Fast Optical Thermometer:

Proof-of-principle was demonstrated about 5 months ago. Focus of our effort has been on improving system reliability and

user friendliness: Major progress, unexpected problem.

High temperature sample holder has been operational for quite some time.

RGA system was installed on the chamber and is routinely used to monitor chamber environment. No trace of W was found in the chamber (from heating filament of

the high-temperature sample holder). QMS was tested but has been removed form the chamber until we are

ready for test runs. Fast Optical Thermometer:

Proof-of-principle was demonstrated about 5 months ago. Focus of our effort has been on improving system reliability and

user friendliness: Major progress, unexpected problem.

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

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

Two colors: Assume (1,T) = (2,T)

Three colors: Assume d2/d[usually a linear interpolation of Ln() is used]

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

Two colors: Assume (1,T) = (2,T)

Three colors: Assume d2/d[usually a linear interpolation of Ln() is used]

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.

Our observations Two-color method achieves sufficient accuracy (~1%). Three-color

method is too difficult.

Our observations Two-color method achieves sufficient accuracy (~1%). Three-color

method is too difficult.

Schematic of Multi-Color Fiber Optical Thermometer

System is configured as three independent two-color thermometer

Temperature is calculated from measurement of radiated energy at two wavelengths:

Temperature is calculated from measurement of radiated energy at two wavelengths:

11

22

5

1

2

212

1

2

5

1

2

212

ln

11c

ln

11c

VC

VC

L

LT

.

Calibration of Thermometer

Calibration is difficult because the lamp filament is discontinuous – image point should be exactly on the lamp filament.

We developed the protocol to reliably calibrate the thermometer (in <5 minutes).

Calibration is so accurate that one point calibration is sufficient to ensure < 1% accuracy over T=1,500-3,500 K

Calibration is difficult because the lamp filament is discontinuous – image point should be exactly on the lamp filament.

We developed the protocol to reliably calibrate the thermometer (in <5 minutes).

Calibration is so accurate that one point calibration is sufficient to ensure < 1% accuracy over T=1,500-3,500 K

Thermometer is calibrated with a tungsten lamp (calibrated for 7 temperatures in the range 1,500-3,500 K)

Thermometer Data Acquisition System

We have developed the software for downloading, post processing, and plotting of the thermometer data. Same interface is used for both calibration and data acquisition

We have developed the software for downloading, post processing, and plotting of the thermometer data. Same interface is used for both calibration and data acquisition

Graphical User Interface

Temperature

PMT2 signal

Significant reduction in the noise level

.

Thermometer Reliability

Test 1: Successive calibration: the basis for developing calibration protocol.

Test 1: Successive calibration: the basis for developing calibration protocol.

Test 2: Chamber installation test: thermometer is removed from calibration stand, mounted in the chamber, returned to calibration stand.Calibration held in repeated tries

Test 2: Chamber installation test: thermometer is removed from calibration stand, mounted in the chamber, returned to calibration stand.Calibration held in repeated tries

Test 3: Long-term reliability, i.e., how long the calibration is holding. Calibration is lost in the hour time

scale: limited set of data; maximum deviation is ~20%, data is stochastic.

Likely problem are the PMTs.

Test 3: Long-term reliability, i.e., how long the calibration is holding. Calibration is lost in the hour time

scale: limited set of data; maximum deviation is ~20%, data is stochastic.

Likely problem are the PMTs.

Current Activities

Improving Thermometer reliability: We are in discussion with PMT manufacturer We are developing 6-GHz amplifier system (30-40 dB gain) to replace

PMTs with PD/amplifier system. The major issue here is achieving the desired signal to noise ratio.

Improving Thermometer reliability: We are in discussion with PMT manufacturer We are developing 6-GHz amplifier system (30-40 dB gain) to replace

PMTs with PD/amplifier system. The major issue here is achieving the desired signal to noise ratio.

Slower/Cheaper Thermometer: We have built a two-color thermometer with 50MHz bandwidth (20 ns

resolution). This system is based on a single fiber connector and photodiodes with build-in amplifier.

The single fiber head has worked so well that we are modifying the high-speed thermometer head accordingly

Slower/Cheaper Thermometer: We have built a two-color thermometer with 50MHz bandwidth (20 ns

resolution). This system is based on a single fiber connector and photodiodes with build-in amplifier.

The single fiber head has worked so well that we are modifying the high-speed thermometer head accordingly

Current Thermometer Fiber Has a High Insertion Loss and Is Quite Sensitive to Positioning

Insertion loss is very high

Uneven signal

Insertion loss is very high

Uneven signal

Fibers image four distinct points on the sample. Very sensitive to surface non-uniformityFibers image four distinct points on the sample. Very sensitive to

surface non-uniformity

We Have Demonstrated 4X Improvement In Insertion Loss With Single Fiber Coupler

Single fiber from thermometer head

Band-pass filter/focuser

PMT or PD

Expander/neutral filter assembly

50-50 splitter

Can be configured with 2 or 4 channels (4 channel version is shown).

4 channel version would allow looking at IR band in order to extend temperature measurement to much lower temperature.

Can be configured with 2 or 4 channels (4 channel version is shown).

4 channel version would allow looking at IR band in order to extend temperature measurement to much lower temperature.