L2D2 Lamps (Deuterium Lamps )
TECHNICAL INFORMATION
OPERATING TEMPERATURE
PRECAUTION AND WARRANTY
Optimum Operating Temperature
Precautions When Using Deuterium Lamps
Construction
Discharging the L2D2 Lamps
Figure 6 shows the external view and internal construction of a deuterium
lamp. The anode has a unique structure covered with ceramic to prevent
abnormal discharge, and the cathode has a highly durable electrode.
Since a deuterium lamp uses the positive column flash of arc discharge,
the cathode is shifted sideways and an aperture is located immediately in
front of the anode so that high intensity is obtained. The aperture plate
placed between anode and cathode may be used as an auxiliary elec-
trode for lamps designed for low voltage lighting.
In deuterium lamps, an aperture electrode is placed between cathode and
anode to compress the discharge, so that high light intensity is obtained. This
required, a high voltage trigger discharge across cathode and anode.
In general, a typical power supply for deuterium lamps consists of the follow-
ing three power supplies.
ꢀ Constant current power supply of 300 mA
(open voltage about 150 V)
ꢀ Trigger power supply of 500 to 600 V peak
ꢀ Power supply for the heater (about 10 W)
However, in view of the need for cost reduction, safety and downsizing, lamp
manufactures are evaluating methods that eliminate the trigger power sup-
ply. One of these is the use of an auxiliary electrode. In this approach, the
electrical energy from a constant current power supply of 150 V/300 mA
(main power supply) is stored in a trigger capacitor and then is discharged
between lamp shield box and cathode. This generates ions and momentarily
reduces the impedance between anode and cathode, leading to the main dis-
charge. However, because this trigger discharge occurs only at a restricted
point near the cathode, it is a less reliable triggering method.
In the L2D2 lamp, ceramic insulators are used as part of the electrode sup-
port, so that the aperture potential is isolated from the shield box potential.
Since this aperture electrode is used as an auxiliary electrode, the trigger dis-
charge can be guided to the aperture, allowing operation at a voltage 40 to
50 V lower than that of a conventional lamp. This also results in higher reli-
ability of the triggering operation. Thus, the greatest advantage of the auxili-
ary electrode is that no trigger power supply is necessary. The circuit shown
on the below, resulting both a cost reduction and downsizing of the power
supply.
To obtain high stability and long operating life, ade-
quate care must be paid to operating conditions includ-
ing the operating temperature of the lamp.
1. Deuterium lamps emit ultraviolet rays which can be
harmful to your eyes and skin. Never look directly at
the emitted lights, nor should you allow it to come
into contact with your skin. Always wear protective
goggles and clothing when operating the lamps.
,
Although the lamp s bulb wall temperature (Tb) rises
as the ambient temperature (Ta) rises, the bulb wall
temperature of conventional deuterium lamps normal-
ly rises to approx. +200 °C (direct-heated cathode
type) to 240 °C (SQ cathode type) when the ambient
temperature is +25 °C. Moreover, the bulb wall tem-
perature of the L2D2 lamps rises even further by +50
°C reaching +280 °C due to the way in which the elec-
trode is constructed. (Bulb wall temperature (Tb) also
differs depending on the lamp type and heater voltage
as well as lamp housing.) Although the operating tem-
perature of Hamamatsu L2D2 lamps has been
designed based on lamps operated under normal tem-
perature, the temperature range given in the table
below is recommended as the allowable operating
temperature range enabling the use of the lamps over
a long period of time with high stability.
Since the bulb wall reaches a very high tempera-
ture (over +200 °C) when the lamp is on, do not
touch it with bare hands or bring flammable objects
near it.
2.
Figure 6: External View and Electrode Construction
External view
Construction
Do not exert mechanical vibration or shock on the
lamp, otherwise the stability will deteriorate.
3.
CERAMIC ELECTRODE
(REAR PIECE)
ELECTRODE
ANODE
APERTURE
4. Silica glass graded sealing.
CERAMIC ELECTRODE
(CENTER PIECE)
In the case of bulbs using silica glass, the window
is formed by connecting different glass sections hav-
ing slightly different expansion rates. Since the
mechanical strength of these seams is low, the bulb
fixing method should be so arranged that no force
is exerted on these seams during fixing or opera-
tion.
CATHODE
BULB
LEAD WIRE
BULB
TLSOC0030EA
LIGHT OUTPUT
5.
6.
Before turning on the lamp, wipe the bulb and win-
dow gently with alcohol or acetone. Dirt on the win-
dow will cause deterioration of the UV transmission,
so always wear gloves when handling the lamp.
High voltage is used to operate the lamp. Use
extreme caution to prevent electric shocks.
Terminology
1Solarization
Transmittance of UV glass and fused silica drops when they are used
over a long period. This is caused by a drop in transparency of the
glass resulting from dirt on the glass and the influences of ultraviolet
rays. In the worst case, the glass becomes cloudy and its life is short-
ened. This is called solarization, and transmittance drops, particularly
in short wavelength region. This phenomenon is hardly ever seen with
synthetic silica.
Table1: Allowable Operating Temperature Range for
Deuterium Lamps
Figure 7: Example Circuit Diagram
Auxiliary electrode operation
•
Lamp Type
L2D2 Lamp
Cathode Type
All Cathode type
+10 °C to +50 °C
Ambient temperature: Ta
Bulb wall temperature: Tb
(+20 °C to +30 °C)*
RT
2Discharge starting voltage
(5 kΩ)
TRIGGER
R
+245 °C to +280 °C
+290 °C Max.
ANODE
When the cathode is sufficiently heated and ready for arc discharge, a
pulse trigger voltage is applied between anode and cathode, and dis-
charge starts. The discharge starting voltage of 30 W deuterium lamps
is approx. 350 V (400 V max.). However, since the discharge starting
voltage rises according to the prolongation of operation time, it is rec-
ommended that a voltage of approx. 500 V be applied to assure dis-
charge. (The maximum applied voltage for trigger is 650 V.) The dis-
charge starting voltage varies depending on the trigger method and
trigger constant.
SWITCH
(<3 kΩ)
Warranty
DEUTERIUM
LAMP
Maximum allowable bulb
wall temperature: Tb Max.
300mA
CONSTANT-
The warranty period will be one year after our ship-
ment to original purchaser or guaranteed life time
whichever comes first. The warranty is limited to
replacement of the faulty lamp. Faults resulting from
natural disasters and incorrect usage will also be
excluded from warranty.
CATHODE
CURRENT
POWER SUPPLY
(150 to 160 V dc)
Temperature enclosed by ( ) indicates the optimum ambient
*
temperature.
CT
(>0.1 µF)
HEATER
POWER SUPPLY
TLSOC0019EB
Tb
Ta
3Output stability
(1) Drift
Conventional circuit
•
TRIGGER
SWITCH
Drift refers to variation of output over a long period caused as a
result of the change in thermoelectron discharge characteristic of
the cathode, change in gas pressure or dirt on the window. It is
expressed in variation per hour. In the case of deuterium lamps, it
takes 10 to 15 minutes until the inside of the lamp reaches thermal
equilibrium after start of discharge, so a warm-up period of 20 to 30
minutes is required.
Ta: Temperature measured at
a position 2.5 cm (1 inch)
away from the bulb wall
Tb: Temperature on the bulb
RT
(1 to5 kΩ)
ANODE
DEUTERIUM
2.5 cm
(1inch)
wall (cathode side)
TRIGGER
POWER
SUPPLY
(500 to
LAMP
300mA
CONSTANT-
CURRENT
POWER SUPPLY
(150 to 160 V dc)
CATHODE
(2) Fluctuation
CT
600 V dc)
(0.2 to 0.5 µF)
HEATER
POWER SUPPLY
Fluctuation refers to variation of output caused by deterioration of
the cathode or fluctuation of discharge position. Light output fluc-
tuates approx. 0.05 % at intervals between a few minutes and a few
hours. In addition, the position of the arc point also fluctuates.
As the ambient temperature (Ta) rises, cathode tem-
perature increases, resulting in evaporation of the
cathode. If the ambient temperature (Ta) drops, the
gas pressure inside the bulb is reduced increasing the
kinetic energy of the gas and ions causing sputtering
of the cathodes thermionic coating. In both cases, the
gas inside the bulb is rapidly consumed. This deterio-
rates the stability and intensity. Thereby drastically
shortening the operating life.
4Life
TLSOC0020EB
(1)Fluctuation of light output
When the L2D2 lamp series with an aperture size of 0.5 mm diameter will
be operated by the circuit as shown above, it is recommended to employ
CR constant as RT=1 kΩ and CT=0.5 µF to obtain the reliable lamp
ignition.
Life is determined by the point at which fluctuation combining
fluctuation and shift exceeds 0.05 %p-p.
(2)Drop of light output
Life is determined by the point at which the total emitted energy
drops to 50 % of the initial level. As described earlier, decrease in
light output is caused mainly by solarization and dirt inside the
window. The life specified is 2000 hours for L2-2000 series, and
4000 hours for L2-4000 series.
For stable operation of deuterium lamps, care should
be paid to the installation of the lamps so that the bulb
wall temperature (Tb) does not exceed +290 °C.
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HAMAMATSU [ HAMAMATSU CORPORATION ]
