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SUPER-QUIET MERCURY-XENON LAMPS

Hamamatsu Photonics 

SUPER-QUIET MERCURY-XENON LAMPS

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

GLASS BULB

ANODE

HIGH PURITY Xe GAS

HIGH PURITY Hg

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

CATHODE

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)

ARC POINT

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

50 100

200

300

400

BULB TEMPERATURE (°C)

500

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.

AC

2

ANODE

CATHODE

TLSXC0034EA

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