TABLE OF CONTENTS
CHAPTER
1
TITLE
PAGE
DECLARATION
ii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
CONTENT
vii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF SYMBOLS
xv
INTRODUCTION
1.1
Overview
1
1.2
Thermal Loading of Lamp-pumped
3
Nd:YAG Lasers
2
1.3
Previous Research
4
1.4
Problem Statement
5
1.5
Research Objective
5
1.6
Research Scope
6
1.7
Thesis Outline
6
LITERATURE REVIEW
2.1
Introduction
8
2.2
Solid State Laser
8
2.3
Basic Construction of Solid State Lasers
10
2.4
The Nd:YAG Laser
12
2.4.1
Principle of Operation
13
2.5
Energy Transfer in Solid State Lasers
15
2.6
Thermo-optics Effects
16
2.7
Fundamental of Heat Transfer
17
2.8
Modes of Heat Transfer
18
2.8.1
Conduction
18
2.8.2
Convection
19
2.8.3
Radiation
19
2.9
Cooling Techniques in Solid State Lasers
20
2.9.1
Liquid Cooling
20
2.9.1.1 Water Cooler with a Liquid to Air
22
Heat Exchanger
2.9.1.2 Water Cooler with a
23
Liquid to Liquid Heat Exchanger
2.9.1.3 Water Cooler with a Refrigeration
24
Unit
2.10
3
2.9.2
Air or Gas Cooling
25
2.9.3
Conductive Cooling
26
Summary
27
DEVELOPMENT OF A WATER COOLING SYSTEM
3.1
Introduction
28
3.2
Water Cooling System
28
3.2.1
External Coolant
29
3.2.2
Internal Coolant
34
4
3.3
Laser Chamber
36
3.4
Lab Recorder
36
3.5
Monitoring Laser Chamber
38
CHARACTERIZATION OF THE WATER COOLING SYSTEM
4.1
Introduction
40
4.2
Water Temperature
40
4.2.1
Temperature of External Coolant
41
4.2.2
Temperature of Internal Coolant
43
4.3
4.4
5
Water Quality
46
4.3.1
The pH Level
47
4.3.2
Conductivity and Resistivity of Water
49
Summary
53
DEVELOPMENT OF A LASER CHAMBER
5.1
Introduction
54
5.2
Laser Chamber
55
5.2.1
Nd:YAG Laser rod
56
5.2.2
Flash lamp
56
5.2.3
Flow Tube
57
5.2.4
Stainless Steel Block
58
5.2.5
Chamber Heat Sink
60
5.2.6
Base Plate
62
5.2.7
Technical accessories
64
5.3
Assembly of the Laser Chamber
64
5.4
The Laser House
68
6
5.5
Piping
71
5.6
Testing the Circulation System
72
5.7
Water Flow
74
5.8
Summary
76
TEMPERATURE MONITORING DURING PUMPING
PROCESS
6.1
Introduction
77
6.2
Heat Loss
78
6.3
The Temperature Distribution of Laser Chamber
80
6.3.1
80
The Temperature Distribution of the
Laser Chamber with chilled water
6.3.2
The Temperature Distribution of the
84
Laser Chamber without water cooling
7
6.4
Heat at Different Part of the Laser Chamber
87
6.5
Summary
89
CONCLUSION AND SUGGESTIONS
7.1
Conclusion
91
7.2
Problems and Suggestions
93
REFERENCES
96
APPENDIX A
101
PUBLICATIONS
103
LIST OF TABLES
TABLE NO.
TITLE
PAGE
4.1
Temperature measurement of external coolant upon times
42
4.2
Temperature measurement of internal coolant times domain
44
4.3
pH of distilled water at various temperatures
47
4.4
Conductivity of distilled water at various temperatures
50
4.5
Resistivity of distilled water as the reciprocal of conductivity
51
at various temperatures
5.1
Physical properties of pump used by internal cooling system
75
6.1
Physical properties of laser chamber
79
6.3
Temperature at different parts of laser chamber with
81
chilled water operation
6.4
Temperature of laser chamber at different part without
85
chilled water
6.5
The results of energy absorbed at different parts in
laser chamber during pumping process
89
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
2.1
A generic solid state laser
10
2.2
Typical Pumping Cavities ;(a) Single ellipse,
11
(b) Double ellipse, (c) Circular Cylinder, (d) Close-warp
2.3
Energy level system of Nd:YAG laser
13
2.4
The flowchart of energy transfer in solid state lasers
16
2.5
Schematic of a water cooler containing a water to water
23
heat exchanger
2.6
Schematic of a water cooler employing a refrigeration unit
24
2.7
Laser head of a small air-cooled Nd:YAG laser
25
2.8
Typical geometry of a conductively cooled laser rod
26
3.1
The schematic diagram of whole cooling system
29
3.2
The circulation in external coolant
30
3.3
The schematic diagram of external coolant
32
3.4
Photograph of compressor based refrigeration system
33
components
3.5
Photograph of whole system of external coolant
33
3.6
The schematic diagram of internal coolant
35
3.7
The schematic diagram for Lab Recorder calibration
37
3.8
Experimental set-up for temperature measurement of
39
pumping system
4.1
The temperature of external coolant with respect to time
43
4.2
The temperature of internal coolant at various times
45
4.3
Graph pH versus temperature for distilled water
48
4.4
Graph resistivity versus temperature of distilled water
52
5.1
The photograph of Nd:YAG laser rod
56
5.2
The photograph of flashlamp
57
5.3
The photograph of flow tube
57
5.4
Engineering drawing of block 1. (Dimensions are in
58
millimeters (mm))
5.5
Engineering drawing of block 2. (Dimensions are in
59
millimeters (mm))
5.6
The photograph of stainless steel blocks 1 and 2
60
5.7
Dimension of top view of the chamber heat sink. (Dimensions
60
are in millimeters (mm))
5.8
The photograph of chamber heat sink
61
5.9
Dimension of side view of the chamber heat sink. (Dimensions
61
are in millimeters (mm))
5.10
Dimension of front view of the chamber heat sink. (Dimensions
62
are in millimeters (mm))
5.11
Dimension of top view of base plate. (Dimensions are
63
in millimeters (mm))
5.12
Dimension of side view of base plate. (Dimensions are
63
in millimeters (mm))
5.13
The photograph of base plate
63
5.14
The photograph of O ring, block clamps and other screw
64
used to ensemble laser chamber
5.15
The schematic diagram of complete pumping chamber
66
from side view
5.16
The schematic diagram of pumping chamber without
66
chamber heat sink from side view
5.17
The photograph of pumping chamber (From side view)
67
5.18
The photograph of pumping chamber without
67
chamber heat sink (From top view)
5.19
Technical drawing of front cover of laser house from
(a) front view , (b) side view. (Dimensions are in
68
millimeters (mm))
5.20
Technical drawing of housing from (a) front view (b) top view
69
(c) side view. (Dimensions are in millimeters (mm))
5.21
The photograph of laser (a) from top view without laser trail,
70
(b) from top view with laser trail and (c) from side view
including the laser chamber
5.22
Dimension of side view of L pipe. (Dimensions are in
71
millimeters (mm))
5.23
The photograph of L pipe
71
5.24
Schematic diagram showing circulation of cooling system
72
from coolant to the laser head
5.25
The flow path of distilled water in laser chamber
73
during circulation (top view)
5.26
The detail of circulation system in laser chamber
74
(focused in ellipsoid space)
6.1
Temperature profile at laser chamber when operated
83
with chilled water
6.2
Temperature profile without chilled water
87
LIST OF SYMBOLS
Qo
-
Heat before
Q
-
Heat after
t2
-
Time maximum
t1
-
Time minimum
∆θ
-
Temperature change
cp
-
Specific heat
m
-
Mass
θ
-
Temperature
R
-
Water flow rate
v
-
Volume
t
-
Time
Pabsorbed
-
Power absorbed
Pi
-
Power input
%Pabsorbed
-
Percentage of power absorbed