High Pressure Mercury Discharge Research Articles

Transient Hg, Ba+, Ca+ and Y+ Optical Emission Lines of a Mercury HID Lamp Exposed to X-Ray: Thermal Analysis of the Tungsten Electrode with Emissive Mixture Based on Barium, Calcium and Yttrium

A study is made on optical emission spectrum modification during X-ray exposure, in the case of a high-pressure mercury discharge lamp operated at several powers. A strong dependence on the lamp operating power for all the spectral lines intensities is observed. Erosion of the emissive mixture based on barium, calcium and yttrium compounds is evidenced by higher values recorded for spectral line intensities in all cases of X-ray exposure compared with those corresponding to non-irradiated lamps. Boltzmann type functions fitted the experimental data of measured optical emission intensities versus time for Ba+, Ca+ and Y+ lines. However, X-ray influence on plasma electron temperature is not significant. The spectroscopic data are correlated with the results of electrical measurements and of thermal analysis performed for the electrode having the emissive mixture based on barium, calcium and yttrium compounds. A qualitative explanation of the results is also given.

High resolution ultraviolet imaging spectrometer for latent image analysis.

In this work, we present a close-range ultraviolet imaging spectrometer with high spatial resolution, and reasonably high spectral resolution. As the transmissive optical components cause chromatic aberration in the ultraviolet (UV) spectral range, an all-reflective imaging scheme is introduced to promote the image quality. The proposed instrument consists of an oscillating mirror, a Cassegrain objective, a Michelson structure, an Offner relay, and a UV enhanced CCD. The finished spectrometer has a spatial resolution of 29.30μm on the target plane; the spectral scope covers both near and middle UV band; and can obtain approximately 100 wavelength samples over the range of 240~370nm. The control computer coordinates all the components of the instrument and enables capturing a series of images, which can be reconstructed into an interferogram datacube. The datacube can be converted into a spectrum datacube, which contains spectral information of each pixel with many wavelength samples. A spectral calibration is carried out by using a high pressure mercury discharge lamp. A test run demonstrated that this interferometric configuration can obtain high resolution spectrum datacube. The pattern recognition algorithm is introduced to analyze the datacube and distinguish the latent traces from the base materials. This design is particularly good at identifying the latent traces in the application field of forensic imaging.

254 nm Radiant Efficiency of High Output Low Pressure Mercury Discharge Lamps with Neon-Argon Buffer Gas

High output low pressure mercury (LPM) discharge UV lamps have been briefly introduced. In order to measure the 254 nm radiant efficiency simply and preciously, Keitz formula was used and its advantage was illustrated. The LPM lamps had outer diameter of 19 mm (T6). The buffer gases are neon (65%) and argon (35%) with total pressure 1-10 Torr (133-1333 Pa). The lamps were operated with cold spot temperatures from 20°C to 80°C and discharge current from 0.8 A to 2.0 A. The electric field, input power, 254 nm UV irradiance and irradiance of other Hg lines from 265 to 579 nm in positive column were measured. The radiant power of each wavelength can be calibrated according to the 254 nm output and the Keitz formula. It was shown that the radiant efficiency of 254 nm can reach a maximum of above 40% at cold spot temperature 45-47 °C and current 1.6 A for filling pressure less than 3 Torr. The optimal mercury vapor pressure was 1.2 to 1.4 Pa. The output percentage of other Hg lines was below 5%. With the decrease of buffer gas pressure, the 254 nm radiant efficiency increased obviously.

254 nm Radiant Efficiency and Spectral Lines of High Output T6 Low Pressure Mercury Discharge Lamps with Neon–Argon Buffer Gases

254 nm Radiant Efficiency and Spectral Lines of High Output T6 Low Pressure Mercury Discharge Lamps with Neon–Argon Buffer Gases

Experimental and theoretical investigations on the warm-up of a high-pressure mercury discharge lamp

Modern high-pressure discharge lamps are forced to provide instant light and hot relight capabilities—if possible at lower power units. A detailed understanding of the warm-up of high-pressure discharge lamps is therefore required. Complex fluid model codes were developed for the past years including more and more processes like two-dimensional treatment of convection trying to provide a more comprehensive and consistent description of high-pressure discharge lamps. However, there is a lack of experimental data to examine the performance of these models. This work provides a very complete set of geometrical, electrical, spectroscopic, and thermographic data according to the warm-up of a high-pressure mercury discharge lamp that is compared to the results of a state of the art fluid code. Quantitative agreement is achieved for single parameters like wall temperatures. But the paper also reveals the need for further investigations and improvements of the code.

Study of photometric properties of high-pressure mercury discharge with thallium iodide additives (HgTℓI) using the ray-tracing method

The photometric properties of HgTℓI high intensity discharge (HID) lamps have been calculated by solving the radiation transport equations in the discharge, using the ray-tracing method. The partial pressures of the various chemical species in the plasma are computed assuming the plasma is in local thermodynamic equilibrium (LTE), using a curve fit to an experimentally measured temperature profile. The plasma is also assumed to be fully mixed, implying a constant mercury/thallium ratio throughout the discharge tube. The spectral line broadening includes neutral Van der Waals and charged particle Stark broadening. The potential influence of ‘de-mixing’ on the spectra is also considered.

A two-dimensional modeling of the warm-up phase of a high-pressure mercury discharge lamp

The main objective of this work is to provide a better understanding of the warm-up phase of high-intensity discharge lamps. As an example of application, we chose the high-pressure mercury lamp. Based on two-dimensional fluid model parameters, such as the electric current, the length and the diameter of the burner are modified and the effect of the convective transport is studied. This allows us to obtain a thorough understanding of the physics of these lamps in their transitory phase. The simulation of the warm-up phase is a must for the proper predictions of the lamp behavior and can be conducted by solving the energy balance, momentum, and Laplace’s equations for the plasma, using the frame of the local thermodynamic equilibrium coupled with the energy balance of the wall.

Application of an antenna excited high pressure microwave discharge to compact discharge lamps

A novel type of high pressure microwave discharge has been investigated to feed the microwave power at the centre of the compact high pressure discharge lamps using the antenna effect. This method of microwave discharge is named as the antenna excited microwave discharge (AEMD). The 2.45 GHz microwave of around 50 W from the solid state microwave generator can sustain a stable plasma column in the small gap between a couple of antennas fitted on the compact lamp filled with discharge gases at a pressure higher than atmosphere. The AEMD has been applied to a compact metal halide lamp and an extremely high pressure mercury discharge lamp. As a result, the metal halide lamp showed high luminous efficacy of around 130 lm W−1. The excellent lamp properties obtained here can be explained by the low heating loss at the antennas and the lamp wall. The profiles of the microwave electric field in the lamp and the microwave launcher have been numerically calculated to consider the microwave power supply into the lamp.

Influence of Plural Loads on Rupture of the Sealed Parts in Super High Pressure Mercury Discharge Lamps

Influence of Plural Loads on Rupture of the Sealed Parts in Super High Pressure Mercury Discharge Lamps

Temperature dependence of VUV transmission of synthetic fused silica

The temperature dependence of the VUV transmission of synthetic fused silica is of interest for commercial applications as well as for fundamental research. In this work the transmission properties of Suprasil 2 from Heraeus with an absorption edge at very low wavelengths is investigated. The absorption edge of this quartz glass shifts from 170 to 180 nm between 789 and 1129 K. The Urbach rule is discussed for the characterization of the temperature dependent transmission curves. The results are applied to the diagnostics of the Hg 185 nm line from a high pressure mercury discharge lamp.

The Effect of Residual Stress on the Rupture of Sealed Parts in Super High Pressure Mercury Discharge Lamps

Super-high-pressure mercury discharge lamps have been used as UV light sources in the photolithography exposure process. It is well known that these lamps applied internal pressure is more than 1MPa and the outer bulb temperatures reach over 500°C. Thus, the safety for rupture of the lamps has been a very important issues in their design. In this study, the effects of the following two factors on the rupture characteristics of the sealed parts were investigated experimentally, (1) joule heating in the current operation, (2) heat conduction from the discharge. In addition, the finite element calculation (FEM) was carried out to investigate the stress distribution in the sealed parts. The experimental results showed that the rupture occurred in the cooling process when the maximum temperature of the sealed parts was more than 1200°C. The numerical results showed that the maximum value of the maximum principal stress σ1 occurred near the point where a rupture initiated in the experiments. In addition, the experimental results were in fairly good agreements with the FEM results. The authors proposed that the maximum temperature of the sealed parts should be less than 1000°C during operation to prevent the lamp rupture.

Discrete ordinates method in the analysis of the radiative transfer in high intensity discharge lamps

This paper deals with radiation transfer in cylindrical high pressure discharges for which local thermodynamic equilibrium can be assumed. An S–N approximation (a set of N discrete directions) of the discrete ordinates method is used to solve the radiative transfer equation. A summary of the basic equations and numerical formulations is given in order to calculate the spectral intensities and then to evaluate radiative flux and net emission coefficient. Also, the net emission coefficient is described by a semi-empirical formula which contains terms representing the generation and absorption of radiation. The results are presented for a typical high pressure mercury discharge commonly used as a light source.

Lowering of the cathode fall voltage by laser exposure of the cathode in a high-pressure mercury discharge

The effect of an additional electrode heating by laser light exposure of one electrode has been studied in a high-pressure mercury discharge. The exposed electrode operates as cathode or anode during the corresponding half-cycles of a square-wave current which has been used for driving the discharge. The additional heating influences the discharge voltage and the electrode tip temperatures in different ways during the cathode and anode phases. Only during the cathode phase is there a noticeable decrease in the discharge voltage connected with a moderate increase in the cathode tip temperature. The maximum absorbed laser power of 6.2 W causes a voltage decrease of about 3.5 V for a discharge current of 1.8 A. The exposure during the anode phase is characterized by a strong increase in the electrode tip temperature and a nearly unchanged discharge voltage. Theoretically determined parameters of the cathode boundary layer are given. For a constant discharge current the power balance at the cathode surface suggests a nearly linear dependence of the discharge voltage lowering on the laser input power, which has been verified experimentally.

Lowering of the cathode fall voltage by laser exposure of the cathode in a high-pressure mercury discharge

Lowering of the cathode fall voltage by laser exposure of the cathode in a high-pressure mercury discharge

Spectroscopic measurement of radiation of high-pressure mercury discharge lamps

Compact size and high efficiency are important features for projection systems. As the most often used sources for projection optics, short arc lamps are characterized by their impressive economy and the ability to produce extremely bright light from small dimensional sources. In this contribution the old principle of back reflection towards the sources is applied to a high-pressure mercury discharge lamp with a reflector to improve the radiance of the source by 35% at a certain reduced solid angle. Increasing the optical thickness of sources is equivalent to reducing the total phase space (etendue) of emitted radiation by the same factor, which is very useful for compacting sources. In addition, by comparing the forward radiation and the back-reflected radiation obtained from spectroscopic measurements, we calculate the absorptivity, emissivity, absorption, and emission coefficients of the plasma of the arc lamp based on Kirchhoff’s Law and Planck’s equation which is necessary for determining its temperature and pressure.

A numerical study of the supply mode effects on high-pressure mercury discharge lamp dynamic thermal behavior

This paper presents a numerical study of the dynamic behavior of high-pressure mercury discharge lamp as a function of supply mode. Bidimensional time-dependent equations have been solved by using a semi-implicit finite-element code. The model has been developed in the frame of the local thermodynamic equilibrium hypothesis. After validation by using experimental data from the literature, this model was applied to analyze the effects of some key parameters such as frequency for an ac arc current and the ratio cycle parameter for square arc-current wave form on the convective process. The results obtained have been used to analyze the dynamic thermal behavior of high-pressure mercury plasma (pressure equal to 0.3 MPa) working under currents widely different in frequency and wave form.

Finite-Element Stress Analysis and Strength Evaluation of Super High Pressure Mercury Lamp Bulbs under Internal Pressure

Super high pressure mercury discharge lamps have been used as UV light sources for photolithography, such as patterning LCDs, PCBs and semiconductors. The bulbs of the lamps are generally made of silica glass. This study evaluates optimal shapes for various lamp bulbs under internal pressure employing the Finite Element Method (FEM). As the result, the optimal shape of the bulb was obtained and the relationship between the rupture stress and the bulb wall thickness t was clarified. The optimal shape of the bulb obtained is 0.7 ≤ D/L ≤ 0.85, where L is the total length of the bulb and D is the diameter. Static water pressure-tests were conducted in order to verify the numerical results. It was found that tendency between the numerical results and experiments were in fairly good agreement.

An Effect of Residual Stress on the Rupture Strength of Super High Pressure Mercury Discharge Lamp Bulbs

An Effect of Residual Stress on the Rupture Strength of Super High Pressure Mercury Discharge Lamp Bulbs

A Study on the End Shape of the Sealed Parts of the Bulb Side in the Super High Pressure Discharge Lamps to Improve the Lamp Strength under Internal Pressure

Super high pressure mercury discharge lamps have been used as a UV and visible light sources for photolithography exposure process, such as patterning LCDs, PCBs and semiconductors. This study examines their rupture characteristics and discuss a guideline for designing a part of lamp between the end of bulb and the end of the sealed part under internal pressure. Finite-Element method (FEM) was employed to investigate the maximum principal stress σ1 distribution near the end of the sealed part. Furthermore, static water pressure tests were conducted to examine the strength characteristic of the bulbs. As the results, the rupture characteristics near the end of the sealed parts can be elucidated and the guideline for designing the end of the sealed parts were drawn up. Moreover, the relationships among the rupture pressure and the outer diameter D2 of the glass parts in the sealed parts and the length L1 near the end of the sealed parts were obtained for increasing the bulb strength. It was found that the strength near the end of the bulb was increased as the diameter D2 was decreased and the length L1 was increased. The rupture characteristics obtained by the numerical results were in fairly good agreements with those by the experiments.

The characteristics of the sealed parts in super high pressure mercury discharge lamps under internal pressure

The characteristics of the sealed parts in super high pressure mercury discharge lamps under internal pressure