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Datasheet: L2421 (Hamamatsu Corporation)

Super Quiet Mercury Xenon Lamps

 

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Hamamatsu Corporation
1
FEATURES
High stability
Fluctuation (p-p) ..................... 1.0 % (Typ.)
2.0 % (Max.)
Drift ....................................
0.5 % /h (Typ.)
Long life
Guaranteed life .................. 500 h to 1000 h
Average life ...................... 1000 h to 2000 h
Virtually no arc point shift ....... 0.1 mm (Max.)
Instantaneous starting and restarting
High intensity in deep UV region
Point light source, High luminance
APPLICATIONS
Wafer Inspection
Semiconductor annealing
Fluorescent microscope
Blood analyzer
UV curing for epoxies, etc.
Interferometer, Refractometer
Microfilm enlarger
A Mercury-Xenon Lamp is a special lamp designed to
provide high radiant energy in the ultraviolet region.
Since an optimum mixture of mercury and xenon gas is
enclosed, this lamp offers the characteristics of both
Xenon lamps and super-high-pressure Mercury lamps.
For example, the spectral distribution of a Mercury-Xe-
non Lamp includes a continuous spectrum from ultra-
violet to infrared of the xenon gas and strong mercury
line spectra in the ultraviolet to visible range. In com-
parison to super-high-pressure mercury lamps, the ra-
diant spectrum in the ultraviolet region is higher in in-
tensity and sharper in width. The Mercury-Xenon Lamp
also features instantaneous starting and restarting, which
are difficult with super-high-pressure mercury lamps,
thus making them an excellent choice as ultraviolet light
sources.
Conventional Mercury-Xenon Lamps have a shortcom-
ing in that the arc point fluctuates and moves gradually
with operating time as a result of the cathode erosion.
Hamamatsu has used its many years of experience and
expertise in the fields of photonics to produce Super-
Quiet (SQ) Mercury-Xenon Lamps. The Hamamatsu SQ
Mercury-Xenon Lamps employ a specially developed
cathode which has minimized the cathode erosion, thus
allowing extremely high stability and long life.
SUPER-QUIET
MERCURY-XENON LAMPS
DEEP UV LIGHT SOURCE
FOR PRECISION MEASUREMENT
PATENT
Information furnished by HAMAMATSU is believed to be reliable. However, no responsibility is assumed for possible inaccuracies or omissions. Specifications are
subject to change without notice. No patent rights are granted to any of the circuits described herein. 2003 Hamamatsu Photonics K.K.
Subject to local technical requirements and regulations, availability of products included in this promotional material may vary. Please consult with our sales office.
2
GLASS BULB
ANODE
HIGH PURITY Xe GAS
HIGH PURITY Hg
CATHODE
MOVEMENT OF ARC POINT
Conventional Mercury-Xenon Lamps have a shortcoming
in that their arc point can move gradually as a result of cath-
ode erosion during normal operation. The SQ Mercury-Xe-
non Lamp uses a specially developed, durable cathode
which shows negligible erosion with operating time. There-
fore, once the optical system is set up, it is no more neces-
sary to adjust it over the operating life of the lamp.
Figure 3: Comparison of Cathode Erosion
Super-Quiet Mercury-Xenon Lamps
After 5 h Operation
After 1000 h Operation
Conventional Lamp
After 5 h Operation
After 1000 h Operation
POWER SUPPLY
Mercury-Xenon Lamps must have a stable light emission
output to be used as light source for measuring purposes.
Therefore, because the output radiant intensity is approxi-
mately in proportion to the current flowing into the lamp, a
stabilized power supply should be provided for the lamp.
Figure 4 shows a diagram of such a stabilized power supply
consisting of a main power supply and a trigger power sup-
ply. Stabilized power supplies specifically designed for
Hamamatsu SQ Mercury-Xenon Lamps are also available
from Hamamatsu (See page 8).
Figure 4:
Block Diagram of Stabilized Power Supply
MAIN POWER
SUPPLY
TRIGGER POWER SUPPLY
CONSTANT DC CURRENT POWER
SUPPLY
TRIGGER
SWITCH
TRIGGER
TRANSFORMER
MERCURY-XENON LAMP
ANODE
CATHODE
AC
TLSXC0034EA
CONSTRUCTION AND OPERATION
Figure 1 shows the construction of the lamp. The lamp has
same shape as that of the conventional Xenon short-arc
lamp or super-high-pressure mercury lamp with two elec-
trodes of cathode and anode. The electrodes face each other
in an oval glass bulb which is filled with a certain amount of
mercury and high purity xenon gas under several MPa of
pressure.
Figure 1:
Construction of Lamp
TLSXC0033EA
As for operation, Mercury-Xenon Lamps utilize the principle
of light emission by arc discharge. This type of lamp must
be installed either vertically with the anode above the cath-
ode or horizontally. Initially an arc discharge triggers the
lamp to start its emission. The lamp maintains stable op-
eration via an applied dc voltage. The light emission from
the arc discharge has strong line spectra ranging from ul-
traviolet to infrared radiation. After the lamp is switched on,
emission of light from the xenon gas occurs. This is accom-
panied by efficient vaporization of the mercury, and emis-
sion of light for the mercury spectrum. It takes several min-
utes for the radiant intensity to reach the maximum value,
as the gas pressure inside the bulb increases after the bulb
is lit up until it reaches a thermal equilibrium. The gas pres-
sure during operation is approximately 3 times higher than
that when the lamp is not operated. Figure 2 shows the typi-
cal temperature distribution of a lamp bulb after thermal
equilibrium.
Figure 2:
Typical Temperature Distribution of a Lamp Bulb
(at Vertical Operation)
BULB
ARC POINT
100
50
200
300
500
400
BULB TEMPERATURE (
C)
TLSXB0007EA
STABILITY OF ARC (FLUCTUATION)
The elimination of arc fluctuation has been an important is-
sue for Mercury-Xenon Lamp users in precision light mea-
suring applications. Hamamatsu has studied this "fluctua-
tion" carefully, and ascertained that it is mostly an irregular
movement of the arc point caused by a lack of electrons
emitted from the cathode. The Hamamatsu SQ Mercury-
Xenon Lamp has solved this problem by incorporating a high-
performance cathode especially developed for this purpose.
SUPER-QUIET MERCURY-XENON LAMPS
3
1) Main Power Supply
Besides supplying the lamp with stable dc power, the main
power supply keeps the cathode at the optimal operating
temperature with a specified current. The cathode tempera-
ture is very important for lamps: when too high, evaporation
of the cathode materials is accelerated; when too low, work
function becomes worse, causing cathode sputtering which
greatly reduces the lamp's life.
The lamp current must be set within a specified range to
ensure lamps to operate stably for a long time. For this rea-
son, each wattage lamp has their respective operating lamp
current values and ranges. Since the radiant intensity is ap-
proximately in proportion to the lamp current values (as
agreed from Figure 9), the power supply must be designed
with higher stability than is required from the lamp.
2) Trigger Power Supply
This is for starting the lamp to discharge. As shown in Fig-
ure 4, it gives a high frequency triggering pulse to the lamp
load by inductive coupling. The lamp's initial discharge char-
acteristic is that its starting voltage is approximately 10 kV.
However, the characteristic fluctuates according to cathode
fatigue or variations of the filled-in gas pressures. There-
fore, in actual devices a triggering voltage of approximately
20 to 25 kV should be applied, taking safety margin into
consideration as well.
CHARACTERISTICS
With regard to data which differs with the wattage ratings, a
typical example would be the use of a 200 W lamp (type
L2423). The unspecified data that is given, applies to all the
lamps irrespective of the wattage of lamp.
1) Spectral Distribution
The radiation spectrum of the lamp has strong brilliant line
spectra from the ultraviolet to the visible range. Figure 5
shows the radiated spectral distribution, for Mercury-Xenon
lamps and other lamps. This spectral distribution includes
both the radiation spectrum of a Xenon lamp and brilliant
mercury line spectra.
Figure 6 shows a comparison of the radiated spectral distri-
bution of a Mercury-Xenon Lamp and a super-high-pres-
sure mercury lamp. Compared to the super-high-pressure
mercury lamp, the Mercury-Xenon Lamp provides greater
radiation intensity in the deep UV range from 300 nm down-
ward, and is characterized by sharp line spectra with high
peak.
Figure 5:
Spectral Distribution of Various Lamps
TLSXB0085EC
300
200
0.01
0.1
1
10
100
400
500
600
700
800
900
1000
RADIANT INTENSITY (
W/cm
2

nm
-1
) at 50 cm
WAVELENGTH (nm)
MERCURY-XENON LAMP (200 W)
DEUTERIUM LAMP (30 W)
HALOGEN LAMP (24 V -150 W)
XENON LAMP (150 W)
(313)
(405)
(577)
(365)
(436)
(546)
Figure 6:
Comparison of Mercury-Xenon Lamp with
Super-High-Pressure Mercury Lamp
TLSXB0078EA
2) Luminance Distribution
Maximum luminance is located nearby the cathode, and it
decreases towards the anode. Figure 7 shows the luminance
for a 200 W lamp distribution relative to the cathode area.
Figure 7:
Luminance Distribution (200 W Lamp L2423)
TLSXC0032EA
3) Flux Distribution
Figure 8 shows the flux distribution of the lamps. It has
uniform distribution in the horizontal direction.
Figure 8:
Flux Distribution (at Vertical Operation)
TLSXC0031EA
180
200
220
240
260
280
300
320
340
20
40
60
80
100
120
140
160
0
100 %
80
60
40
20
ANODE
CATHODE
+
-
(mm)
2.0
1.5
1.0
0.5
0
DISTANCE FROM CATHODE
40(%)
30
30
50
60
70
80
90
100
0.5
0
0.5
ARC WIDTH (mm)
LAMP CURRENT 8.0 A dc
AMBIENT TEMP. 25
C
ANODE
CATHODE
RADIANT INTENSITY (
W/cm
2

nm
-1
) at 50 cm
WAVELENGTH (nm)
200
300
400
500
600
0
10
20
30
40
50
60
297
313
365
577
405
436
546
SUPER-HIGH-
PRESSURE MERCURY
LAMP (200 W)
MERCURY-XENON
LAMP (200 W)
265
4
SUPER-QUIET MERCURY-XENON LAMPS
4) Lamp Current and Lamp Voltage
Figure 9 shows the current-voltage characteristic. The lamp
voltage slightly increases in accordance with the lamp cur-
rent.
Figure 9:
Current-Voltage Characteristic
(200 W Lamp L2423)
TLSXB0086EA
3) Fluctuation and Operating Time
As has been stated, the radiant intensity decreases with
operating time. No conspicuous change in fluctuation, how-
ever, occurs with the elapsing of operating time. Figure 15
a) - d) show the change in fluctuation according to the
elapsed operating time and Figure 14 shows the block dia-
gram for fluctuation measurement.
LIFE
1) Radiant Intensity and Operating Time
The light output intensity decreases with operating time. This
is due to a loss of glass transmittance caused by blacken-
ing the bulb wall. This is due to evaporation of the cathode
material, and partly by solarization effects from ultraviolet
radiation on the bulb glass crystals. Figure 12 shows the
change of radiant intensity as a function of the operating
time.
(Typ. at 25
C)
RELATIVE INTENSITY (%)
OPERATING TIME (h)
0
100
200
300
400
500
600
700
800
900
1000
0
100
90
80
70
60
(Typ. at 25
C)
LAMP VOLTAGE (V dc)
OPERATING TIME (h)
0
500
1000
1500
2000
15
20
25
30
(Typ. at 25
C)
RELATIVE INTENSITY (%)
OPERATING TIME (min)
0
5
10
15
20
0
50
100
MERCURY-XENON
LAMP
(200 W)
SUPER
HIGH PRESSURE MERCURY
LAMP (200 W)
(Typ. at 25
C)
RELATIVE INTENSITY (%)
LAMP CURRENT (A dc)
6.5
7.0
7.5
8.0
8.5
9.0
9.5
60
0
80
100
120
140
SPECIFIED RANGE
(Typ. at 25
C)
LAMP VOLTAGE (V dc)
LAMP CURRENT (A dc)
6.5
7.0
7.5
8.0
8.5
9.0
9.5
22
23
24
25
26
27
SPECIFIED RANGE
TLSXB0089EA
Figure 13: Lamp Voltage vs. Operating Time
(200 W Lamp L2423)
2) Lamp Voltage and Operating Time
The electrode distance in conventional lamps is gradually
increased due to sputtering phenomenon, resulting in in-
creased lamp voltage. Contrary to it, the SQ Mercury-Xe-
non Lamp exhibits negligible electrode spattering and there-
fore, the lamp voltage is almost constant over a long period
of operation. Figure 13 shows the change of the lamp volt-
age vs. operating time.
TLSXB0087EA
Figure 12: Radiant Intensity vs. Operating Time
(200 W Lamp L2423)
Figure 11: Radiant Intensity vs. Initial Operating Time
(200 W Lamp L2423)
TLSXB0090EA
5) Staibility of Radiant Intensity
5)-1 Radiant Intensity and Lamp Current
The output radiant intensity changes in proportion to the
lamp current. Figure 10 shows their relation. Furthermore,
compared to a super-high-pressure mercury lamp, the lamp
reaches its maximum radiant intensity within a very short
time. This is because the discharge through the enclosed
xenon gas causes the mercury to be efficiently vaporized.
This is shown in Figure 11.
Figure 10: Radiant Intensity vs. Lamp Current
(200 W Lamp L2423)
TLSXB0088EA
5
10 min
10 min
10 min
10 min
1.0 %
1.0 %
1.0 %
1.0 %
10 min
10 min
10 min
10 min
10 %
10 %
10 %
10 %
SQ MERCURY-XENON LAMP
WINDOW 20 mm
ND FILTER
APERTURE 5 mm
AMPLIFIER
SILICON PHOTODIODE
RECORDER
SQ MERCURY-
XENON LAMP
POWER SUPPLY
TLSXB0091EA
d) After 1500 h operation
c) After 1000 h operation
b) After 500 h operation
a) After 5 h operation
Figure 15: Fluctuation vs. Operating Time
TLSXC0030EA
Figure 14: Block Diagram for Fluctuation Measurment
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