The German Aerospace Centre carries out since many years studies on the flow and combustion of liquid jets expanding in a high pressure chamber through a single injector. For this study, liquid nitrogen has been injected into a pressurized test chamber filled with gaseous nitrogen at different test conditions. The behavior of the flow is well known on principal but the liquid zone, near the injector, is not accessible for the analysis using classical optical diagnostics. In order to be able to study this zone of the cryogenic jet, a new compact and pulsed (50 ns FHWM typical) X-ray source has been developed and utilized. During experiments carried out on the test bench M51 of the DLR, this soft X-ray flash energy, enable us to carry out radiography of the zone close to the injector (z/d < 10) for chamber pressures from 1.0 to 6.0 MPa and temperatures of the liquid nitrogen jet ranging from 100 to 130 K. The data and their Processing result in the possibility to obtain the various density profiles corresponding to injection conditions. The obtained results are compared with those collected by other methods (experimental and numerical) already used in the DLR.
KEYWORDS: X-rays, Radiography, Fluctuations and noise, Power supplies, Capacitors, Switches, Fast packet switching, X-ray sources, Control systems, Diodes
A compact single focus x-rays flash device is described in this paper. This device is composed of the following essential components: a 50 kV high voltage power supply, a capacitor bank, a pulse forming line, a high frequency and high voltage switch, a voltage multiplier and an x-ray tube. Before breakdown into the x-ray tube, voltage is rise up to 400 kV. Leading to photon energy at a maximum of 400 keV. The duration of voltage pulses is 100 ns. The device could work in two different modes, in the continuous pulsed mode up to 500 Hz and in burst mode, each burst is composed by 3 to 5 shots. At this time the burst mode is running at 3.5 kHz frequency.
In this paper, an EUV lamp development based on high repetition rate compact capillary discharge devices is presented. The first lamp, named CAPELLA (Capillary EUV Lamp for Lithography Approach) emits up to 1 W in-band and has been selected as the illumination source of the first experimental European exposure tool (BEL). An industrial version of CAPELLA named PROXIMA has recently been operated and is the first commercial product of a new spin-off of GREMI called IGETECH. The design of a 10 kHz capillary discharge likely to emit up to 10 W in-band and labelled as ATλAS (AT wavelength Alternative Sources) is finally documented.
The development and operation of a multi watt, multi kHz and low debris EUV gas discharge source is reported. The Capillary EUV Lamp for Lithography Approach (CAPELLA) is designed and characterized for its application in the french EUV exposure tool named BEL. The burst operation at high repetition rate, up to 3 kHz, of the source during time period of a few seconds is described and shown to be relevant for the BEL application. The long time stability over hours is measured to be of 0.6 percent. Other technical BEL requirements such as energy flux, EUV output stability, spatial position stability, collection angle are briefly presented and their fulfilment is documented through the experimental data obtained on the CAPELLA prototype. An experimental characterization of debris nature and deposition rate on plasma facing silicon targets has been performed over millions of shots showing evidence of the crucial role of the discharge regime.
In this work, ablative and gas capillary discharges have been investigated as potential sources for the EUV lithography technology. Carbon and lithium ablative discharge spectroscopy and EUV energy measurements have been performed. Gas (O2, Ne, Ar, Kr and Xe) capillary discharge were powered by fast, nanosecond, high voltage Blumlein-like pulser. Detailed investigation of capillary length and diameter, gas pressure, capacitance and inductance of the electrical driver are documented. The energy density, expressed in J cm-3, appears as a monitoring factor for an efficient production of 13.5 nm radiation band. The measurement and the evaluation of measurement uncertainties lead to the conclusion that the in band, 13.5 nm +/- 0.9 nm, energy radiated by the Xe lamp developed in this work ranges from 0.5 mJ/sr/shot to 20 mJ/sr/shot for a 7 J energy input. Repetition rate investigation of the first prototype have shown operation at 50 Hz in continuous mode and up to 350 Hz in burst mode.
The characterization of near nozzle dense sprays and axisymmetric gas jets using X-ray flash techniques is presented. Flash radiography and X-ray induced fluorescence imaging (X.I.F. imaging), using a flash X-ray developed at GREMI, offer two complementary diagnostics particularly efficient in high pressure conditions. In this work, a compact flash X-ray device is used to freeze fluid motions. Single shot radiographs of argon jets and water sprays expanding in ambient air have been performed. Radial density profiles were measured and quantitative density measurements have been extracted for argon, nitrogen-argon mixture and water jets, using flash X-ray radiography. UV fluorescence emissions due to X-ray excitation of the jet species were imaged on a gated intensified CCD camera.
The fluorescence of dense rare gas targets has been produced and analyzed using X-ray flash, e-beam and ion beam as excitation techniques. For the first time to our knowledge an extended database of argon and krypton molecular UV emissions, i.e. the Molecular Ion Continua, has been obtained with a very good agreement between spectra whatever the pumping technics is used. The estimation of potential surface for both singly and doubly charged argon trimers and the consideration of previous ab initio calculation for the argon dimer enables us to confirm some former hypothesis but also to suggest new pathways likely to be at the origin of the population of the upper states radiating in the Molecular Ion Continua.
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