Copper Vapor Research Articles

Upgrade of the resonance ionization laser ion source at ISOLDE on-line isotope separation facility: New lasers and new ion beams

The resonance ionization laser ion source (RILIS) produces beams for the majority of experiments at the ISOLDE on-line isotope separator. A substantial improvement in RILIS performance has been achieved through a series of upgrade steps: replacement of the copper vapor lasers by a Nd:YAG laser; replacement of the old homemade dye lasers by new commercial dye lasers; installation of a complementary Ti:Sapphire laser system. The combined dye and Ti:Sapphire laser system with harmonics is capable of generating beams at any wavelength in the range of 210-950 nm. In total, isotopes of 31 different elements have been selectively laser-ionized and separated at ISOLDE, including recently developed beams of samarium, praseodymium, polonium, and astatine.

Analysis of temporal jitter in a copper vapor laser system

Temporal jitter in a magnetic pulse compression based copper vapor laser (CVL) system is analyzed by considering ripple present in the input dc power supply and ripple present in the magnetic core resetting power supply. It is shown that the jitter is a function of the ratio of operating voltage to the designed voltage, percentage ripple, and the total propagation delay of the magnetic pulse compression circuit. Experimental results from a CVL system operating at a repetition rate of 9 kHz are presented.

Laser Diagnostic Investigation on the Spray and Combustion with Butanol-Biodiesel-Diesel Fuel Blends

. In this paper, blends of butanol-biodiesel-diesel were tested inside a constant volume chamber to investigate liquid spray and combustion of the fuels. With high-speed camera and synchronized copper vapor laser, spray penetration during injection is recorded since it has a higher light reflectivity. Various ambient temperatures and fuel composition were investigated. There is a sudden drop in spray penetration at 800 K and 900 K, but not at 1000 K and 1200 K. When the spray penetration of the butanol-biodiesel-diesel blends is compared to that of the biodiesel-diesel blends, under non-combusting environment, a sudden drop in spray penetration length is also observed at 1100 K. High speed imaging shows that, for the non-combusting case, at 1100 K, the tip of the spray jet erupts into a plume sometime after injection for the butanol-biodiesel-diesel blend. The same is not seen with the biodiesel-diesel blend, neither at lower ambient temperature of 900 K. It is concluded that micro-explosion can occurs under particular conditions for the butanol-biodiesel-diesel blend, and the results is consistent with previous study in the literature.

Numerical calculations of the dynamics of liners formed by copper vapors’

The paper reports the calculations of the dynamics of fast copper liners. The implosion time is of the order of 80 ns. The problem is considered in a two-dimensional (axisymmetrical) statement. For simulation, a system of equations of electron magnetic hydrodynamics (EMH) is solved, using splitting into physical processes. At the first stage, the ideal MHD with a frozen-in magnetic field is considered. An implicit variation differential scheme is constructed for the solution of the equations of ideal two-temperature magnetic hydrodynamics. The dynamics of the liner splitting is calculated at different values of the Hall parameters. With an increased value of the Hall parameters, the character of the magnetic field’s penetration into plasma changes radically and the field’s “tongues” penetrating along one of the electrodes are formed.

Frequency dependence of amplifying parameters of a copper vapor laser using air as a buffer gas

We use a pair of copper vapor lasers in an oscillator–amplifier configuration to investigate amplifying parameters such as the small signal gain and the saturation intensity versus the pulse repetition frequency when two different types of buffer gases are employed. We show that the values of these parameters are not the same if different gas mixtures are used in the gain medium. We show that the values of the parameters are estimated to be higher if a He–Ne buffer gas is used than in the case of air. The laser output power is relatively high and has fairly good stability at some special pulse repetition frequencies when air is used as a buffer gas.

Comparative study on second harmonic conversion and saturation characteristics of three copper vapor laser beams of same average power and different spatial coherence

This paper presents a comparative study on second harmonic conversion and saturation behavior of three copper vapor laser (CVL) beams of same average power up to 11 W (510 nm), however with different spatial coherence width of 17%, 35%, and 100% of the full beam cross-section. The nonlinear crystal employed is beta barium borate. It is observed that the trends in second harmonic (SH) conversion efficiency and its saturation are widely different for the three CVL pump beams. As expected, the conversion efficiency scaled up with increase in pump power. However, very interesting trends are observed in SH saturation characteristics with scaling of pump beams spatial coherence. For lower coherence CVL beam, the saturation of SH efficiency is observed at lower pump flux and at higher average power. Also, the saturation occurred at lower SH efficiency for CVL beam of lower spatial coherence. The fall in the SH efficiency after the peak is more rapid for lower spatial coherence pump beam. The experimental trends are explained in terms of combined effect degree of spatial coherence of pump beams and the thermal dephasing in the nonlinear crystal by high pump average power.

Laser treatment for verrucous hemangioma

Verrucous hemangiomas (VH) are hyperkeratotic vascular malformations characterized by a combination of dilated vasculature in the entire dermis, or even much deeper, and prominent hyperkeratosis, which may result in papules, patches, or violet-colored erythematous tumors. Bleeding after trauma or scratching is frequent. Surgery is nowadays the gold-standard treatment but laser therapymay nevertheless be useful in the superficial component of the lesions. Treatments with argon laser and copper vapor laser have been used [1], but both are limited by lack of specificity, poor penetration, and adverse sequelae. Recently, the Nd:YAG 1,064-nm laser has been used in a few cases, either alone or combined with CO2 or the pulsed dye laser (PDL) [2].

Investigation of the characteristics of a colloidal solution and its solid phase obtained through ablation of zinc in water by high-power radiation from a copper vapor laser

Experimental data are presented on the study of a colloidal solution created through zinc ablation in water by means of high-power radiation from a copper vapor laser. Absorption spectrum analysis is performed in the optical range of λ = 200–600 nm. The structural composition and morphology of the solid phase isolated from the colloid are determined by means of X-ray diffractometry, and atomic-force and scanning electron microscopy. It is demonstrated that ZnO, as well as zinc, nanoparticles, which oxidize to ZnO under colloid ageing, are present in the colloid composition after target irradiation. The ZnO end product has a complex structure, which is based on hexagonal crystals 40 × 80 nm in size on average.

An experimental study and theoretical analysis of the mode characteristics of a narrow line-width, pulsed dye laser oscillator at different pump powers

This paper presents an experimental study and theoretical analysis on the effect of pump power on the divergence, pointing, line-width and wavelength stability of a narrow line-width, high repetition rate dye laser oscillator. The dye laser oscillator, based on the hybrid multiple-prism grazing-incidence grating cavity, was pumped by copper vapor laser (CVL). The dye laser mode characteristics were studied at CVL average pump powers of 2, 4 and 8 W. The single pulse dye laser divergence/pointing stability was studied by far-field intensity distributions. The line-width and wavelength stability were studied using a high resolution wave-meter. The experimental results were theoretically analyzed in terms of dye laser mode structure drift induced by beam pointing instability, beam divergence and thermally induced optical path length fluctuation. A comprehensive theoretical treatment on pointing stability of dye laser beam and its influence in the dye laser wavelength stability is presented. The theoretical and experimental trends were found to be in good agreement.

The effect of operational parameters on the output power of copper vapor laser with small-bore tube

The effects of buffer gas pressure, electrical input power and pulse repetition frequency on the output power of 510.6- and 578.2nm transitions have been experimentally investigated in a copper vapor laser with small-bore tube (11mm of diameter and 580mm of length). It is observed that the output power characteristics are strongly influenced by these parameters. A maximum output power of laser is obtained at about 4W with 27 kHz of pulse repetition frequency, 30 torr of Ne buffer gas pressure and 1.42kW of electrical input power. The waveforms of the current, tube voltage and laser pulses have also been observed.

A comparative study on thermal lensing characteristics of low (∼500 °C) and high (∼1500 °C) temperature variants of copper vapor laser

This paper presents a comparative study on thermal lensing characteristics of a low temperature copper vapor laser (CVL) (LT-CVL as Copper-HBr laser) and a high temperature CVL (HT-CVL as elemental CVL). Interferometric techniques were used to study the combined thermal lens power of active gaseous medium and discharge sealing optical windows as well as that of the optical windows separately at different electrical input powers. As the input power varied from 2.7 to 4.6 kW, the combined thermal lens power varied from −1.4 to +0.94 km −1 for LT-CVL and from +1.4 to +13 km−1 for HT-CVL. The thermal lens power of the windows varied from +3 to +15 km −1 for HT-CVL. On the other hand, for LT-CVL, the thermal lens due to windows was very weak and could not be measured. It was observed that the origin of net thermal lensing mostly resides in the discharge tube windows owing to its higher temperature variation of refractive index as compared to that of gaseous active medium. The weaker thermal lens characteristics of an LT-CVL was attributed to its much lower working temperature and relatively flatter radial gas temperature profile than that of an HT-CVL.

Visual Spray and Evaporization Character of Biodiesel Blend Fuels in a Combustion Chamber

Different from traditional engine test, an optical constant volume chamber simulated HTHP ambient condition was employed by using biodiesel-diesel-butanol blends. With high-speed camera and synchronized copper vapor laser, recorded fuel spray and combustion process, measured liquid jet penetration length and heat release rate under variable ambient temperature and fuel composition conditions. With ambient temperature increasing, burn process converted from premixed combustion to diffusion combustion, and the micro-explosion became weak and disappeared. It was concluded that micro-explosion could occur under particular initial ambient temperature and specific blend ratio conditions for the biodiesel-diesel-butanol fuel, that will distinctly enhance fuel evaporation and premixed combustion process.

Influence of dye gain medium flow on the wavelength jitter and the drift of high repetition rate—Single mode dye lasers

This paper presents the effect of the flow of the dye gain medium on the wavelength jitter (<30 s) and drift (≈10 min) of a single axial mode dye laser pumped by a copper vapor laser (5.5 kHz). The study was carried out using a wave-meter. The dye solution temperature was maintained to within ±0.1 °C to allow the influence of dye flow rate on the wavelength stability. For the investigated dye flow rate, varying from 1.4 to 2.8 lpm (with corresponding Reynolds number varying from 1975 to 3950), the dye laser wavelength jitter reduced from ±0.15 pm (±130 MHz) to ±0.08 pm (±70 MHz) and drift rate reduced from 1.0 to 0. 2 MHz/s. However for flows beyond 1.7 lpm, random fluctuations in dye laser wavelength were observed. The observed behavior was linked to the flow related variation of angular spread and angular drift of the dye laser beam circulating in the cavity. This was revealed by an exhaustive study of the long term (≈10 min) divergence and pointing stability of the single mode dye laser output beams for different dye media flows.

Necklace-shaped Au–Ag nanoalloys: laser-assisted synthesis and nonlinear opticalproperties

Here in this paper, necklace-shaped Au–Ag nanoalloys (NAs) have been synthesized by alaser-based approach. A chain of Ag nanoparticles (NPs), which were joined togetherwith Au junctions, was formed upon copper vapor laser (CVL) irradiation of acolloidal mixture of Ag and Au NPs; while the corresponding NPs were separatelyprovided by laser ablation of gold and silver targets in deionized water by a 1064 nmQ-switched Nd:YAG laser. Dependence of the NAs development process on the CVLirradiation time in three distinct stages of as-mixed, nucleation and complete formation hasbeen systematically studied by UV–vis optical absorption spectroscopy analysisas well as by transmission electron microscopy (TEM), which was exploited tovisually confirm the NAs evolution through the process. Furthermore, the x-rayphotoelectron spectroscopy (XPS) technique was accurately employed to determine thesynthesized alloy content. On the other hand, using the open-and closed-apertureZ-scan technique, the nonlinear absorption (NLA) as well as nonlinear refraction (NLR)changes in Au–Ag NAs were investigated through their formation. The deduced resultsfrom the nonlinear optical properties of the colloidal NAs in the mentioned stages wereinterpreted considering the spectroscopic and microscopic observations. The total change ofindividual Au and Ag NPs saturable absorption (SA) into the reverse saturableabsorption (RSA) behavior was concluded through the evolution into Au–Ag NAs.

Comparison of the output power of copper halide lasers versus buffer gas pressure and frequency

In this work, an iodide copper vapor laser (CuI) has been designed and fabricated. The effect of different operational parameters such as frequency and buffer gas pressure on output power laser have been investigated to determine the optimal condition of frequency and neon gas pressure. Based on experimental results, the maximum output power of about 0.5W is obtained at 16 kHz of frequency and 30 torr of Ne gas pressure. Moreover the experimental results of CuI laser have been compared to the similar data for the other halide copper lasers such as CuBr and CuCl. The output power of CuI laser is less than that of others. The optimum frequency of lasers have different values, but the optimum gas pressures are the nearly same for three lasers, at the same conditions.

A two dimensional theoretical model for describing gain coefficient in N2-lasers and the model validity for CVL and excimer lasers

Based on our previously reported measurements on the gain-value in a N2- laser and numerical calculations, we introduce a method to obtain an analytical expression for the small signal gain, g0, where the dependency of g0 on the laser geometrical configuration, including electrodes length and gap separation, is demonstrated. For this study one- and two-dimensional approaches for the photon density have been applied independently to determine gain-parameter, where for explaining the observed dependency of the gain-parameter on the laser electrodes separation, dAMP, which was found experimentally and explained by an empirical expression of the type g0=r+q/dAMP, with r and q some constants, realization of introducing an extra dimension along the gap separation was unavoidable. For the electrodes length, lAMP, we have already shown that an empirical equation of the type g0=m+n/lAMP, with m and n some constants, is consistent with the measurements corresponding to N2-lasers. With this realization, it is proved that the gain-parameter in N2-lasers can be written as g0abovethreshold=m″+g0z(γLz,z)+g0y(γLy,y), where it consists of two independent gain-values along the electrodes length (z) and gap separation (y) with the corresponding power losses given by γLz and γLy. m″ is a very small quantity showing that laser is operating slightly above the threshold. The results of this calculation are consistent with our recent measurements and also other reported N2-laser gain values measured under moderate current density conditions. To check the validity of the model for other types of lasers, the reported gain-values for copper vapor lasers of different laser tube radii, RAMP, and tube lengths, lAMP, have been examined using the one-dimensional model of either g0(RAMP) or g0(lAMP) and the consistency with the observed measurements was found to be quite satisfactory. The model was also found to be valid for the excimer lasers of different types, different gas mixtures and pressures at a constant input operational voltage. Due to limited numbers of the reported experimental measurements, for the graphs preparation of g0(lAMP) in excimer lasers we used the observed data at V0=30kV and also some variations of the input voltages in the range of ΔV≅20kV have been adopted. The results for both cases were found to be consistent with the proposed one-dimensional model.

Machining performance of laser surface micro-textured drilling tools

Surface modification of high-speed steel drills using laser has been proposed as a step before physical vapour deposition in order to increase the adhesion of the titanium nitride coating on the tool substrate. A copper vapour laser and a scanning-head system were used to produce highly controlled laser ablation on the surface. In the current work, the laser average power varied from 0.5 to 6 W and the laser shots were applied next to one another. After laser surface modification and coating, the drills were used to machine low-alloy carbon steel and stainless steel in a CNC machine. The tool lives were then compared to those obtained with the same kind of tool but whose substrate was prepared conventionally. The laser-treated drills had a longer lifetime than conventional ones. Under the conditions of this study, the laser-treated drills presented a 40% higher performance than conventional drills for carbon steel machining. The increase in performance reached 400% in stainless steel drilling. In general, laser processing with an average power of 1 W yielded the best results.

Multiple Facial Papules of Birt-Hogg-Dubé Syndrome Treated with a CO2Laser

Dear Editor: Birt-Hogg-Dube syndrome (BHDS) is an unusual genodermatosis related to systemic diseases such as recurrent pneumothorax, lung cysts and several malignancies like renal carcinoma1. Therefore, knowledge of and accurate management of BHDS can be of great benefit for the patient. The development of multiple benign adnexal tumors on visible areas can have an important psychological effect. We report 2 cases of BHDS treated successfully with a CO2 laser. Case #1 was a 41-year-old healthy man presenting with multiple firm skin-colour papules on the face, ears and neck since adolescence (Fig. 1, image on the left). His father had the same type of lesions in higher number and one episode of pneumothorax 20 years ago. Fig. 1 Pictures of case #1 before and after CO2 laser treatment showing improvement of the multiple facial papules without adverse events. Case #2 was a 54-year-old healthy man who developed, since the age of 20, multiple firm skin-colour papules on face, upper back and ears. No other family members were affected. Histological studies were consistent with fibrofolliculomas (FF) and angiofibromas (Fig. 2). A complete blood count, biochemical studies, tumor markers and thyroid hormones showed no alterations. A thorax computed tomography (CT) showed numerous subpleural cystic lesions in case #1 and was normal in case #2. Renal echography and abdomino-pelvic CT scans were normal. Fig. 2 Micrograph image. Hematoxylin and eosin staining reveals classical fibrofolliculoma epithelial strands arising from the infundibulum within a mucinous connective tissue in two lesions and angiofibroma in another one (×10). According to the literature, diagnosis of BHDS is done with more than 10 skin lesions that are clinically compatible with FF and a minimum of 1 lesion histologically diagnosed as an FF. These two cases were therefore diagnosed as BHDS2,3. They received one CO2 continuous wave laser treatment (2 watts, vaporization defocused. Sharplan 1060; Laser Industries Ltd. Tel Aviv, Israel). Topical anesthetics with lidocaine 25 mg+prilocaine 25 mg (EMLAR cream AstraZeneca) were used under 2 hours of occlusion. Substantial remission (over 75% of the facial lesions) was achieved in both cases and was maintained after 18 months of follow-up in case 1 and 4 years in case 2. There was no recurrence during this time (Fig. 1). BHDS is characterized by asymptomatic, firm, skin-colored papules on the face and upper trunk, usually beginning in the third decade. Ear location is rather specific in BHDS2. The classical triad included FF, trichodiscomas and acrochordons. However, controversy exists in the literature about the real identity of these tumors. Currently the most accepted theory is that they actually represent a unique entity: FF4. Molecular analysis of the folliculin gene mutation supports the diagnosis. Inactivation of a tumor-suppressor gene could explain the possible coexistence with chorioretinopathy and other skin tumors such as angiofibromas, lipomas, angiolipomas, oral polyps and collagenomas2, associations that have not always been found3. Knowledge of BHDS is extremely important due to its association with recurrent pneumothorax, pulmonary cysts and malignancies (especially renal and thyroid carcinomas). Controversy exists about the possibility of an association with gastrointestinal tumors)2,5. Patients and close-relatives must be screened with abdomino-pelvic CT scanning at the time of diagnosis and with subsequent annual magnetic resonance images. Chest radiography, blood and biochemical tests, tumor markers and thyroid hormones complete the work-up1. Differential diagnosis of these mixed ectodermal and mesenchymal origin FFs of BHDS must include other inherited syndromes with multiple firm facial papules. Those with epithelial lesions include: Cowden disease (trichilemmomas); Brooke-Spiegler syndrome and Rombo syndrome (trichoepitheliomas) and basaloid follicular hamartoma syndrome (basaloid follicular hamartoma). Angiofibromas (mesenchymal origin) [[should suggest?]] tuberous sclerosis although they have been reported in association with BHDS as well. Classical treatment options are excision, electrocautery, and dermabrasion. Nowadays, ablative lasers represent an interesting and secure choice allowing a fast and more effective result with fewer side effects. Few cases of BHDS FF treated with lasers have been reported. Er:YAG, copper Vapor laser and CO2 lasers have been used without adverse effects6-8. Head to head studies comparing different kinds of lasers or other ablative methods are lacking. In conclusion, we present 2 cases of BHDS treated with a low dose CO2 laser with excellent response without collateral effects. We review the required complementary studies that should be carried out.

Modeling of breakdown during the post-arc phase of a vacuum circuit breaker

After a high-current interruption in a vacuum circuit breaker (VCB), the electrode gap is filled with a high density copper vapor plasma in a large copper vapor density (∼1022 m−3). The copper vapor density is sustained by electrode evaporation. During the post-arc phase, a rapidly increasing voltage is applied to the gap, and a sheath forms and expands, expelling the plasma from the gap when circuit breaking is successful. There is, however, a risk of breakdown during that phase, leading to the failure of the VCB. Preventing breakdown during the post-arc phase is an important issue for the improvement of VCB reliability. In this paper, we analyze the risk of Townsend breakdown in the high copper vapor density during the post-arc phase using a numerical model that takes into account secondary electron emission, volume ionization, and plasma and neutral transport, for given electrode temperatures. The simulations show that fast neutrals created in the cathode sheath by charge exchange collisions with ions generate a very large secondary electron emission current that can lead to Townsend breakdown. The results also show that the risk of failure of the VCB due to Townsend breakdown strongly depends on the electrode temperatures (which govern the copper vapor density) and becomes important for temperatures greater than 2100 K, which can be reached in vacuum arcs. The simulations also predict that a hotter anode tends to increase the risk of Townsend breakdown.

Enhanced performance of a wide-aperture copper vapour laser with hydrogen additive in neon buffer gas

A wide-aperture copper vapour laser was demonstrated at ∼10 kHz rep-rate with hydrogen additive in its buffer gas. Maximum power in excess of ∼50 W (at 10 kHz) was achieved by adding 1.96% hydrogen to the neon buffer gas at 20 mbar total gas pressure. This increase in output power was about 70% as compared to ∼30 W achieved with pure neon at 5.5 kHz rep-rate. The 70% enhancement achieved was significantly higher than the maximum reported value of 50% so far in the literature. The enhancement was much higher (about 150%) as compared to its 20 W power at 10 kHz rep-rate using pure neon as the standard CVL operation.