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"Sejauh ini, metode optik untuk pengukuran konsentrasi phytoplankton masih jarang dimanfaatkan di Indonesia. Dalam penelitian ini dilakukan perancangan, perakitan dua sensor optik untuk mengukur konsentrasi phytoplankton, khususnya chlorella spp. galur UI Depok yang dikulturkan dalam medium ekstrak tauge.Penelitian ini terdiri atas dua bagian utama, yaitu pengujian karakteristik optik yang mencakup sifat absorpsi dan fluoresensi Chlorella spp. serta perancangan, perakitan dan pengujian dua sensor optik berdasarkan sifat termaksud. Sensor optik terdiri dari konfigurasi sensor I yang bekerja berdasarkan gejala absorpsi dan hamburan cahaya, serta konfigurasi sensor II yang bekereja berdasarkan gejala absorpsi, hamburan dan fluoresensi cahaya phytoplankton. Untuk sejauh mungkin mengurangi pengaruh karakteristik air, zat lain yang terlarut dan intensitas sumber cahaya terhadap hasil pengukuran, pada konfigurasi I digunakan dua tempat larutan yang identik, satu sebagai wadah ukur, yang lain sebagai wadah referensi. Pada konfigurasi II diterapkan cara lain untuk mengurangi pengaruh tersebut.Pengujian kedua sensor optik dilakukan dengan cara mengukur intensitas cahaya yang bersesuaian dengan gejala yang dimanfaatkan pada masing-masing konfigurasi. Pengujian dilakukan untuk setiap sampel larutan Chlorella spp. yang telah diketahui konsentrasinya dan kemudian mengolah dan mengkaji hubungan antara intensitas cahaya dan konsentrasi phytoplankton.Dalam pengukuran untuk konfigurasi sensor opyik I dan II dilibatkan berturut-turut 45 dan 55 sampel larutan Chlorella spp. dengan konsentrasi yang berbeda. Rentang konsentrasi dari 0 s.d 10 pangkat 6 sel/ml dipilih mewakili konsentrasi yang terdapat di alam, yaitu mulai dari perairan tak subur hingga pada kondisi ekstrim (algal blooming) serta kondisi budi daya kultur.Didapatkan bahwa intensitas transmisi terukur pada kedua konfigurasi memiliki hubungan linier yang konsisten terhadap konsentrasi sel chlorella spp. pada seluruh rentang konsentrasi sesuai dengan yang diharapkan secara teoritik. Ambang pengukuran konsentrasi berharga sekitar 500 sel/ml.Hubungan kelinieran yang konsisten sesuai dengan teori didapatkan pula dari hasil pengukuran fluoresensi dengan konfigurasi sensor II, yaitu dari 1 x 10 pangkat 3 hingga 2,5 x 10 pangkat 6 sel/ml."

"The role of shock wave in the generation of laser induced secondary plasma was first suggested by Kagawa et al. from an experimental result employing N2 laser on metal targets at reduced surrounding air pressure. This so-called shock wave induced plasma model has since been reexamined and confirmed in a series of experiments performed by Kurniawan and Kagawa et al. using TEA (Transversely Excited Atmospheric) CO2 laser and XeCI excimer laser. All of these experiments were performed at reduced gas pressures. The most important characteristics revealed by those experiments consist of the typical hemispherical shape of the plasma with a thin emission shell at the plasma front, which moves with a propagation length proportional to t°-4, in excellent agreement with the shock wave characteristics predicted theoretically by Sedov. It was further demonstrated that ionic emission was generally insignificant compared to neutral atom emission. While those results have provided relatively solid and comprehensive supports for the model, additional evidence on the density jump characteristic of shock wave generation and other on some unique aspect concerning interaction of shock wave with an object will still be desirable for further clarification on the role of the model.A series of experiment have been carried out on the dynamical process taking place in the secondary plasma induced by normal oscillation and Q-switched Nd-YAG (yttrium aluminum garnet) laser on brass, copper and zinc targets at reduced air pressures. Accurate dynamical characterization of the cross-sectional view of the plasma expansion has been made possible by the unique confinement technique using two parallel glass plates. In order to detect the shock front and the emission front simultaneously, a new shadowgraph technique involving a He-Ne laser as a light probe was also developed. Furthermore in an experiment intended for giving support to the shock wave excitation model qualitatively, the plasma was forced to collide with a wedge placed in front of the target in order to examine the reflection and diffraction phenomena. Measurements were also performed on the time-profile of the plasma emission to provide a description of the plasma temperature variation with time. The study was further substantiated by measurement of the time-resolved spatial distributions of emission intensities.The results showed that the plasma was generated through the shock-wave and the dynamical process of the secondary plasma is divided into two stages, namely, the "shock excitation stage" and the "cooling stage". During the shock excitation stage, the atoms gushing out from the target were adiabatically compressed against the surrounding gas, resulting in a rapid rise of the plasma temperature up to around 9,000 K. For the case of 2 Ton gas pressure, with the laser pulse of 86 m7 targeted on copper sample, the shock excitation stage lasted for about 1 µs, which was followed immediately by the cooling stage and the plasma temperature decreases gradually to around 7,500 K in about 3 .is. The excitation stage and the cooling stage periods became longer with increasing laser pulse energy.The multiple excitation processes associated with the secondary plasma emission, and generated by successive multiple shock wave, was clearly observed when the normal oscillation laser was focused onto the surface of the target. The emission characteristics of this secondary plasma showed an extremely low ion and background emissions. This condition is suitable for highly sensitive spectrochemical analysis, as the temperature of the plasma is still high enough (around 7,000 K) for the excitation of neutral atoms. Another favorable conditions is the large amount of material ejected in the process (amounting to 10 µg), which permits an average analysis.For a practical consideration, the condition to increase sensitivity by suppressing the background was also studied. The result showed that the sensitivity of laser induced shock wave plasma spectroscopy could be increased by reducing laser pulse energy, in which the less expensive time-integrated detection method can be applied. On the other hand, when the sample requires a high power laser beam, the sensitivity could also be enhanced with the aid of a time-gated DMA (Optical Multi channel Analyzer) system by cutting-off the ionic emission coming from the shock excitation stage."

"In spite of abundant experimental evidences supporting the viability of the laser induced shock wave plasma model for the explanation of the important features ofthe plasma and the associated spectroscopic characteristics, a controversy on the atomic excitation mechanism in the plasma has remained to be completely resolved. In this study the contributions of the shock wave model and two other most popular models, the electron-ion recombination model and thc electron collision model were thoroughly investigated. For that purpose, a special technique has been developed for the direct detection of the charge current in conjunction with plasma emission measurement dining the laser plasma generation and expansion. The current detection was performed by placing a partially transmitting metal mesh electrode at a distance in front of the sample surface with the sample target sewing as the counter electrode. The electric Held between the mesh and sample surface was set up and varied by applying a variable DC voltage (0-400 Volt) between them. The laser plasma was generated by a YAG laser (64 ml, 8 ns) tightly focused on a Cu target through the mesh electrode in low-pressure surrounding gas. It was found that the charge current time profiles obtained at various gas pressures invariably exhibit a lack of consistent correlation with the emission time profile of the plasma throughout most of the emission period. The result of this study has thus practically eliminated any significant roles ofthe electron-ion recombination and electron collision models in the excitation process. We are therefore led to conclude that the shock wave model proposed earlier is most plausible for the consistent explanation of the secondary plasma emission, while the other two models may have some contribution only at the very initial stage ofthe secondary plasma generation."

"ABSTRACTAn comprehensiove study has been carried out for the study and extension of lases induce shock wave plasma spectroscopy (LISPS) application to non metalic soft and hard samples. For this purpose, a series of experiments were conducted to investigate the dynamical process taking place in the laser plasma generated by a high power and short pulse laser irradiations on a non metal soft and hard samples it was found that in the case of non metal soft sample, the ablated atoms failed to induce a visible plasma at the surface of the target however, it became possible, after a few laser shots depending on the target layer thickness, to generate the sock wave plasma emitting the characteristic spectral line of the target material.Another related phenomenon studied in this experiment is the pre-irradiation effect pbserved on a non metal hard sample such as quartz sample, which was characterized by absence of secondary plasma at athe initial shots. The disappearance of this effect at a later stage was found to be connected with the appearance of a crater of appropriate depth on the sample surface created by iniatial repeated irradiations on the sample surface. The plasma produced thereafter exhibited typical features of a secondary plasma. Further experiment employing aaratificial ring crater on the sample surface has eliminated the pre-irraduation effect completely, and has thus demonstrated that it is the confinenement effect of the crater which was solely responsible for the generation of secondary plasma from the non metal hard tearget. This conclusion is ini confrormation with the shock wave proposed earlier.These experimental studies have thus considerably substantiated our understanding of the process of secondary plasma generatuion. In turn, this result helps to improve the quality and extend the scope of LISPS applications in the future"

"ABSTRACTAn comprehensiove study has been carried out for the study and extension of lases induce shock wave plasma spectroscopy (LISPS) application to non metalic soft and hard samples. For this purpose, a series of experiments were conducted to investigate the dynamical process taking place in the laser plasma generated by a high power and short pulse laser irradiations on a non metal soft and hard samples it was found that in the case of non metal soft sample, the ablated atoms failed to induce a visible plasma at the surface of the target however, it became possible, after a few laser shots depending on the target layer thickness, to generate the sock wave plasma emitting the characteristic spectral line of the target material.Another related phenomenon studied in this experiment is the pre-irradiation effect pbserved on a non metal hard sample such as quartz sample, which was characterized by absence of secondary plasma at athe initial shots. The disappearance of this effect at a later stage was found to be connected with the appearance of a crater of appropriate depth on the sample surface created by iniatial repeated irradiations on the sample surface. The plasma produced thereafter exhibited typical features of a secondary plasma. Further experiment employing aaratificial ring crater on the sample surface has eliminated the pre-irraduation effect completely, and has thus demonstrated that it is the confinenement effect of the crater which was solely responsible for the generation of secondary plasma from the non metal hard tearget. This conclusion is ini confrormation with the shock wave proposed earlier.These experimental studies have thus considerably substantiated our understanding of the process of secondary plasma generatuion. In turn, this result helps to improve the quality and extend the scope of LISPS applications in the future"

"ABSTRACTIn spite of abundant experimental evidences supporting the viability of the laserinduced shock wave plasma model for the explanation of the important features oftheplasma and the associated spectroscopic characteristics, a controversy on the atomicexcitation mechanism in the plasma has remained to be completely resolved. In thisstudy the contributions of the shock wave model and two other most popular models,the electron-ion recombination model and thc electron collision model werethoroughly investigated. For that purpose, a special technique has been developed forthe direct detection of the charge current in conjunction with plasma emissionmeasurement dining the laser plasma generation and expansion. The current detectionwas performed by placing a partially transmitting metal mesh electrode at a distancein front of the sample surface with the sample target sewing as the counter electrode.The electric Held between the mesh and sample surface was set up and varied byapplying a variable DC voltage (0-400 Volt) between them. The laser plasma wasgenerated by a YAG laser (64 ml, 8 ns) tightly focused on a Cu target through themesh electrode in low-pressure surrounding gas. It was found that the charge currenttime profiles obtained at various gas pressures invariably exhibit a lack of consistentcorrelation with the emission time profile of the plasma throughout most of theemission period. The result of this study has thus practically eliminated anysignificant roles ofthe electron-ion recombination and electron collision models in theexcitation process. We are therefore led to conclude that the shock wave modelproposed earlier is most plausible for the consistent explanation of the secondaryplasma emission, while the other two models may have some contribution only at thevery initial stage ofthe secondary plasma generation.Key words: charge current, shock wave, electron-ion recombination and electroncollision.Praiseci is to the Lord for He is my reason in everything I do.This manuscript is never be done without the guidance by Pro£ Tjia May On, towhom I am extremely grateful. He also provided the support without which this thesiswould not possible. He is more than just a teacher for me for his words have deeplytouched me. Moreover, he also introduced me that knowledge is something we shouldshare among others and to improve the education in my country.I am also indebted to Prof. Kiichiro Kagawa at the Fukui University for providingthe atmosphere and the physical resources to make thesis writing in these times of fastpaced research. I am also thankful for the opportunity which is given to me to joinresearch together with him in his laboratory in Japan.Extra special thanks go to Dr. Hendrik Kurniawan for providing me withencouragement and support for this project. He is the first one who encouraged me totake Doctor Cotuse Program which seemed impossible at the beginning. Hiscompanion during research at Applied Spectroscopy Laboratory at University ofIndonesia is a leading experience in research for me.I am particularly grateful to the excellent team of referees who provided criticalcomments on this thesis. Their feedback was a great benefit to me.I gratefully acknowledge all my colleagues: Rinda Hedwig, Mangasi A.Marpaung, Hery Suyanto, MM. Suliyanti, Wahyu S. Budi, and Emon in AppliedSpectroscopy Laboratory at University of Indonesia, for their assistance and supportduring my study.My never-ending thanks to my beloved family, especially to my parents whoexhibited thoughtful patience over extended periods of time when I seemed to beinvisible. Thanks also to Loviana who helped me in all situations which I no longercan resist by myselflFinally, I apologize to all those who helped that I did not acknowledge specifically.I know there were many and greatly appreciate your assistance.August, 2002Author"

"A comprehensive study has been made on the dynamical process-taking place in the laser-plasma generation induced by a TEA CO2 laser bombardment on metal target and non-metal target from low to high pressures surrounding gas. In the case of metal target, pure zinc plate was used as a target and bombarded with 400-mJ-laser pulse energy. Dynamical characterization of plasma expansion and excitation were examined in detail both for target atomic emission (Zn I 481.0 nm) and gas atomic emission (He 1 587.6 nm) by using a unique time-resolved spatial distribution measurement and conventional emission spectroscopic detection method. The results showed that the plasma expands and develops with time. The mechanism of plasma generation can be classified into three cases depending on .the surrounding gas pressures; target shock wave plasma in the pressure range between 2 Ton and 20 Ton, coupling shock wave plasma in the pressure range between 50 Torr and 200 Torr and gas break down shock wave plasma in the pressure range between 200 Ton and I atm. In all cases in the laser-plasma generation under TEA CO2 laser bombardment on metal target, shock wave process always plays important role for exciting the target atoms and gas molecules.In the case of non-metal target, a museum glass was used as a target and bombarded with a 400 nd laser pulse energy. By using the conventional emission spectroscopic detection method, namely temporally and spatially integrated and time-resolved spatially integrated of plasma emission, it was shown that the plasma mainly consists of target atomic emission. Only weak gas atomic emission intensity could be observed even at I atm of surrounding gas pressure. These results indicate that the gas breakdown is not a major process responsible to the plasma formation even at high pressure surrounding gas. Shock wave process was considered as an important role in this plasma formation. By the use of shadowgraph technique to detect the density jump signal due to the shock wave front involving a He-Ne laser as a probe light, simultaneous detection of the shock wave front and the emission front was successfully implemented. The result showed that at the initial stages of plasma expansion shock wave front and emission front coincide and move together with time. At the later stages of plasma expansion the two fronts became separate with the emission front left behind the shock wave front. These results are completely coinciding with the shock wave plasma model. Unfortunately, in this experiment we succeed to detect the density jump signal only for high pressure surrounding gas, above 100 Torr. At the pressures lower than 100 Torr the density jump signal was very weak and it is difficult to distinguish with the noise including in the signal.The other important experimental results that support the shock wave plasma model were also obtained in this experiment, namely the coincidence of emission front regardless of their atomic weight and sub-target effect. By using lead glass as a sample, which contain Pb, Si, and Ca, it was confirmed that the emission front of the Pb I 450.8 nm, Si 1288.2 nm and Ca I 422.6 nm almost coincide regardless of their atomic weight. This result also supports the shock wave plasma model because, by the stagnation of the propelling atoms, the front position of the all atoms coincides regardless of its mass. In the case of sub-target effect, confirm that plasma could be produced even for soft target if sub-target is set behind the sample. In this case we use a quartz sample as a sub-target and a vinyl tape was attached to the quartz sample as a target. The TEA CO2 laser bombardment was used at 150 ml and at 1 atm of air. The main role of the subtarget is to produce a repulsion force for atom gushing with high speed. For shock wave, high speed is necessary condition to compress the gas.Coincidence of the movement of the shock wave front and the emission front in the initial stages of plasma expansion is a direct proof of the shock wave plasma model. By improving the detection technique of the density jump associated with the shock wave, the correlation between the shock wave front and the emission front was examined in detail. For this purpose rainbow interferometer system, which has higher sensitivity compared with the shadowgraph technique, was used to detect the density jump signal. We succeed to realize simultaneous detection of shock wave front and emission front from 3 Ton until 1 atm of air when a quartz sample is bombarded with a 600 nil TEA C02 laser. In all pressure that were examined, the shock wave front and the emission front always coincide and move together with time in the initial stages and separate at the later stages with emission front left behind the shock wave front. The coincidence of the shock wave front and emission front and move together with time at the initial stages of plasma expansion was also obtained by using ruby as a sample at 10 Torr and 100 Ton of air as well as with museum glass at the same laser pulse energy.Another important experimental result obtained in this experiment is that confirmation of the coincidence of the target atomic emission front and gas atomic emission front and density jump. This confirmation was obtained by examined a Quartz sample in 50 Ton of helium and a zinc sample in 100 Ton of helium. This result strongly supports the shock wave plasma model because, in ordinary shock tube experiment, gas emission takes place just behind the shock wave.From a practical point of view of direct microanalysis for spectrochemicaI application of alloy metal samples such as brass, selective vaporization effect was also studied. The results showed that even for Nd-YAG laser with short pulse duration (8 ns) and high power density (30 GWcm 2), selective vaporization take place to a certain extend. It was demonstrated in this experiment that selective vaporization is enhanced if the laser irradiation was repeated on the same spot of sample surface. Meanwhile it was also shown in this experiment that the effect of selective vaporization could be significantly suppressed by increasing the surrounding gas pressure from 2 Toff to around 50 Torr of air."

"ABSTRACTA comprehensive study has been made on the dynamical process taking place in the laser-plasma generation i.nduced by a TEA CO2 laser bombardment on metal target and non-metal target Eom low to high pressures surrounding gas. ln the case of metal target, pure zinc plate was used as a target and bombarded with 400 ml laser pulse energy. Dynamical characterization of plasma expansion and excitation were examined in detail both for target atomic emission (Zn I 481.0 nm) and gas atomic emission (He I 587.6 nm) by using an unique time-resolved spatial distribution measurement and conventionalemission spectroscopic detection method. The resultsshowed that the plasma expands and develops with time. The mechanism of plasma generation can be classified into three cases depending on the surrounding gas pressures; target shock wave plasma in the pnessure range between 2 Torr and 20 Torr, coupling shock wave plasma in the pressure range between S0 Torr and 200 Torr and gas ?break down shock wave plasma in the pressure range between 200 Torr and 1 atm. In all cases in the laser-plasma generation under TEA CO; laser bombardment on metal target, shock wave process-always plays important role forexciting the target atoms and gas molecules.ln the case of , non-metal target, a museum glass was used as a target and bombarded with a 400 mJ laser; pulse energy By using the conventional emission spectroscopic detection method, namely temporally and spatially integrated and time-resolved spatially integrated of plasma emission, it was shown that the plasma mainly consists of target atomic emission. Only weak gas atomic emission intensity could be observed even at 1 atm of surrounding gas pressure. These results indicate that the gas breakdown is not a major process responsible to the plasma formation even at high pressure surrounding gas. Shock wave process was considered as animportant role in this plasma formation. By the use of shadowgraph technique to detect the density jump signal due to the shock wave front involving a He-Ne laser as a probe light, simultaneous detection of the shock wave Bent and the emission iiont was successfully implemented. The result showed that at the initial stages of plasma expansion shock wave 'dont and emission front coincide and move together with time. At the later stages of plasma expansion the two fronts become separate with the emission front left behind the shock wave front. These results are completely coinciding with the shock wave plasma model. Unfortunately, in this experiment we succeed to detect the density jump signal only for high pressure surrounding gas, above 100 Torr. At the pressures lower than 100 Torr the density jump signal was very weak and it is diflicult to distinguish with the noise including in the signal.The other important experimental results that support the shock wave plasma model were also obtained in this experiment, namely the coincidence of emission iziont regardless of their atomic weight and sub-target effect. By using lead glass as a sample, which contain Pb, Si, and Ca, it was confirmed that the emission front of the Pb 1450.8 nm, Si I 288.2 nm and Ca I 422.6 nm almost coincide regardless of their atomic weight. This result also supports the shock wave plasma model because, by the stagnation of the propelling atoms, the front position of the all atoms coincides regardless of its mass. In the case of sub-target effect, we confirmed that plasmacould be produced even for sch target if sub-target is set behind the sample. In this case we use a sample as a sub-target and a vinyl tape was attached to the quartz sample as a target. The TEA CO2 laser bombardment was used at 150 mJ and at 1 atm of air. The main role ofthe subtarget is to produce a repulsion force for atom gushing with high speed. For shock wave, high speed is necessary condition to compress the gas.Coincidence of the movement of the shock wave iiiont and the emission front in the initial stages of plasma expansion is a direct proof of the shock wave plasma model. By improving the detection technique of the density jump associated with the shock wave, the correlation between the shockwave fiont and the emission front was examined in detail. For this purpose rainbow interferometer system, which has higher sensitivity compared with the shadowgraph technique, was used to detect the density jump signal. We succeed to realize simultaneous detection of shock wave front and emission front iiom 3 Torr until 1 atm of air when a quartz sample is bombarded with a 600 mJ TEA CO2 laser. In all pressure that were examined, the shock wave front and the emission front always coincide and move together with time in the initial stages and separate at the later stages with emission front left behind the shock wave tiont. The coincidence of the shock wave iiont and emission front and move together with time at the initial stages of plasma expansion was also obtained by using ruby as a sample at 10 Torr and 100 Torr of air as well as with museum glass at the same laser pulse energy."