Demonstration of the Density Dependence of X-Ray Flux in a Laser-Driven Hohlraum

Young, P. E.; Rosen, M. D.; Hammer, J.H.; Hsing, Wen Hao; Glendinning, S. G.; Turner, R. E.; Kirkwood, R. K.; Schein, J.; Sorce, C.; Satcher, Joe H.; Hamza, A. V.; Reibold, Reinhard; Hibbard, R. L.; Landen, O. L.; Reighard, A. B.; McAlpin, S.; Stevenson, M.; Thomas, Brian

doi:10.1103/physrevlett.101.035001

Cited by 47 publications

(41 citation statements)

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“…The vast majority of previous experiments employed hohlraums of cylindrical shape. [1][2][3] Recently, there has been increasing interest in hohlraums of an elliptical or "rugby" shape, [4][5][6][7] as this design provides the possibility of reduced energy losses into the wall and therefore enhanced radiation drive for a given laser energy input. These hohlraums are currently being investigated for a number of inertial confinement fusion applications.…”

Section: Introductionmentioning

confidence: 99%

High performance capsule implosions on the OMEGA Laser facility with rugby hohlraums

et al. 2010

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Rugby-shaped hohlraums have been proposed as a method for x-ray drive enhancement for indirectly driven capsule implosions. This concept has recently been tested in a series of shots on the OMEGA laser facility ͓T. R. Boehly, D. L. Brown, R. S. Craxton et al., Opt. Commun. 133, 495 ͑1997͔͒. In this paper, experimental results are presented comparing the performance of D 2 -filled capsules between standard cylindrical Au hohlraums and rugby-shaped hohlraums. The rugby hohlraums demonstrated 18% more x-ray drive energy as compared with the cylinders, and the high-performance design of these implosions ͑both cylinder and rugby͒ also provided Ϸ20ϫ more deuterium ͑DD͒ neutrons than any previous indirectly driven campaign on OMEGA and Ϸ3ϫ more than ever achieved on NOVA ͓E. M. Campbell, Laser Part. Beams 9, 209 ͑1991͔͒ implosions driven with nearly twice the laser energy. This increase in performance enables, for the first time, a measurement of the neutron burn history and imaging of the neutron core shapes in an indirectly driven implosion. Previous DD neutron yields had been too low to register this key measurement of capsule performance and the effects of dynamic mix. A wealth of additional data on the fuel areal density from the suite of charged particle diagnostics was obtained on a subset of the shots that used D 3 He rather than D 2 fuel. Comparisons of the experimental results with numerical simulations are shown to be in very good agreement. The design techniques employed in this campaign, e.g., smaller laser entrance holes and hohlraum case-to-capsule ratios, provide added confidence in the pursuit of ignition on the National Ignition Facility ͓J. D. Lindl, P. Amendt, R. L. Berger et al., Phys. Plasmas 11, 339 ͑2004͔͒.

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Section: Introductionmentioning

confidence: 99%

High performance capsule implosions on the OMEGA Laser facility with rugby hohlraums

et al. 2010

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“…Rosen and J.H. Hammer proved [5], and observed experimentally [6], that x-ray temperature in gold low-density converter is higher than in ordinary Au-converter of indirect-drive targets.…”

Section: Direct-indirect Targets Schemesmentioning

confidence: 99%

“…Rosen and J.H. Hammer proved [5], and observed experimentally [6], that x-ray temperature in gold low-density converter is higher than in ordinary Au-converter of indirect-drive targets.Au low-density converters of heavy ions energy to x-rays should have their density varying from 10 mg/cm 3 to 400 mg/cm 3 [7]. Unlike polymers, metal foams are heat conductive and allow cryo-layer formation in fuel capsule of the target by rapid cooling (quench).…”

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Laser study into and explanation of the direct-indirect target concept

Борисенко

Chaurasia

Dhareshwar

et al. 2013

EPJ Web of Conferences

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Abstract. The idea of direct-indirect target is experimentally tested with planar targets from LPI made of low-density metal foam (nanosnow) or of nanoparticles (30%) in plastic aerogels. The laser experiments in BARC have shown that compared to plain targets the foams of/with nanoparticles demonstrate: 1) better x-ray emissivity ; 2) smoother energy distribution over the target surface; 3) material flow from low-density wall being slower and more uniform; 4) active transverse energy transport over the target plane. These properties could be useful for hohlraums and direct-indirect concept. DIRECT-INDIRECT TARGETS SCHEMESPlasma from foams has been studied for decades [1 and ref.], but Au and Bi are not studied enough. The design of direct-indirect target using a 0.25 m-thick outer gold shell was suggested in [2]. The advantage of this design was in the easy process of laser focusing. Disadvantages, such as low x-ray efficiency, necessity of short laser pulse duration and high velocity of Au-plasma were consequent.Another design shown in Fig. 1 was proposed by Yu.A. Merkul'ev [3]. This is a target with Au-lowdensity converter which allows easy laser focusing and long laser pulse. As the result, the Au-plasma motion is slower, but the x-ray efficiency is still low. One more design, shown in Fig. 2, was proposed in [4]. The target with low-density absorber-converter was invented for 2 MJ 5 ns laser pulses. Easy laser focusing, possibility of long laser pulse and high efficiency for 0.53 m wavelength are among its advantages. However with mixed interaction (both x-ray and thermal) taking place in this case, the cryogenic DT layer is difficult to keep.M.D. Rosen and J.H. Hammer proved [5], and observed experimentally [6], that x-ray temperature in gold low-density converter is higher than in ordinary Au-converter of indirect-drive targets.Au low-density converters of heavy ions energy to x-rays should have their density varying from 10 mg/cm 3 to 400 mg/cm 3 [7]. Unlike polymers, metal foams are heat conductive and allow cryo-layer formation in fuel capsule of the target by rapid cooling (quench).Low-density Au is being developed in LLNL and GA, USA, as well as in LPI (Russia). METAL FOAMS PRODUCTION FOR DIFFERENT DENSITIESNo universal fabrication methods exist for high-Z low-density metals in a wide density range. Various technology routes of metal low-density layers are realized for

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“…Недавно в работах [4,5] теоретически было предска-зано повышение температуры рентгеновского излучения в конвертере при замене сплошного золота на пену из золота. Экспериментальная проверка [6] подтвердила теоретические предсказания. Плазма от золотой пены разлетается несколько медленнее, чем плазма (корона) от сплошного металла, что является дополнительным преимуществом применения пены, так как позволяет уменьшить объём «кожуха», увели-чив интенсивность излучения на рабочей капсуле-мишени с DT-смесью.…”

Section: Introductionunclassified

Fabrication of Effective Low-Density Converter of Intensive Laser Radiation to X-Ray and Novel Measurement Method of Layer Density From Heavy Metal Nanoparticles

Акимова¹,

Борисенко²,

Громов³

et al. 2012

PAST-TF

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Предложен метод измерения плотности слоёв из наночастиц тяжёлых элементов с использованием компьютерного рентгенов-ского микротомографа, заключающийся в том, что параллельно с нанесением слоя на подложку слой из наночастиц осаждается на стоящий рядом тонкий графитовый стержень -«свидетель». Средний диаметр частиц около 100 нм. При одинаковых ре-жимах работы томографа на эталонных слоях металла измеряется коэффициент пропускания для данного металла. Из получен-ных коэффициентов пропускания рентгеновских изображений «шапочки» на графитовом стержне определяется эффективная толщина t эф , которая делится на реальную толщину t x и умножается на плотность металла . Эта процедура позволяет опреде-лить плотность слоя  f = t эф /t x . Наши рентгеновские измерения позволили впервые установить, что плотность слоя наночастиц висмута толщиной около 100 мкм уменьшается по высоте (снизу) от 130 до 80 мг/см 3 . На конференции в Германии нашими студентами была представлена компьютерная программа для обработки рентгеновских изображений «свидетелей» и расчёта плотности слоёв малоплотных металлов. Мишени из малоплотного висмута были использованы в экспериментах на Nd-лазере в Центре атомных исследований в Бомбее, Индия.Ключевые слова: непрямые мишени, конвертер, малоплотный металл. FABRICATION OF EFFECTIVE LOW-DENSITY CONVERTER OF INTENSIVE LASER RADIATION TO X-RAY AND NOVEL MEASUREMENT METHOD OF LAYER DENSITY FROM HEAVY METAL NANOPARTICLES. I.V. Akimova, N.G. Borisenko, A.I. Gromov, Yu.A. Merkuliev, A.S. Orekhov P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, RussiaA method of measuring high-Z metal nanoparticles layer density using x-ray computer micro tomography scanner is proposed. This method is based on using a thick carbon pivot ("witness") near the targets during the layer evaporation. The average particle size is about 100 nanometers. The transmittance for the reference metal layers is measured in the same modes of the scanner. Then this transmittance of the top of the pivot is used to calculate the efficient thickness t eff , which is divided by real thickness t x and is multiplied by density of metal . These steps make available the density of the layer:  f = t eff /t x . Our research made possible to find out that the density profile in the nanoparticle layer is increasing in the top-down direction. If the thickness of the layer is 100 mkm, the density is 130 on the bottom and 80 mg/cc on the top. Our students presented a computer software for "witness" image processing and layer density calculation on conference in Germany. The targets made of low density bismuth were used during the experiments with Nd-laser in the Bhabha Atomic Research Center in Mumbai, India.Key word: indirect targets, converter, low-density metal. ВВЕДЕНИЕЭнергетическая эффективность рентгеновских (непрямых) лазерных термоядерных мишеней и ней-тронный выход существенно зависят от средней энергии спектра (температуры) и интенсивности рент-геновского излучения в «кожухе»-конвертере лазерного излучения в рентгеновско...

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Demonstration of the Density Dependence of X-Ray Flux in a Laser-Driven Hohlraum

Cited by 47 publications

References 5 publications

High performance capsule implosions on the OMEGA Laser facility with rugby hohlraums

High performance capsule implosions on the OMEGA Laser facility with rugby hohlraums

Laser study into and explanation of the direct-indirect target concept

Fabrication of Effective Low-Density Converter of Intensive Laser Radiation to X-Ray and Novel Measurement Method of Layer Density From Heavy Metal Nanoparticles

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